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Shot peening (SP) is a surface cold hardening process used on metals to enhance life under cyclic stress. In this case, SP was applied to SAE5160H samples of steel quenched tempered in oil at 460 °C used for leaf springs. This study shows the residual surface stresses measured through X-ray diffraction (XRD) and the microhardness variation through the perpendicular-to-the-peened surface using a combination of metallographic preparation and Vickers microhardness (HVN). This combination of techniques makes possible measuring the SP effect in perpendicular-to-the-treated surface. A residual stress of -365.8 ± 78 MPa measured by XRD and a maximum microhardness of 525± at 92.7 HVN on the surface were obtained for the SP material. Alternatively, an average of 54.2 ± 54.3 MPa residual stress measured by XRD and 433 ± 39.5 HVN were obtained for the As-it-is samples. In addition, corrosion electrochemical potential tests showed that SP increases the corrosion potential, which makes this process undesirable if the SP component is exposed to aggressive environments. Moreover, the As-it-is samples presented not statistically significant HVN difference in the measured points. The combination of experimental techniques allows estimating hardness change in perpendicular-to-the treated surface separated by as little as 10 µm but with a simpler specimen preparation than other techniques such as XRD or strain gauges. Such a combination can be an alternative for estimating residual stresses through depth., El granallado es una técnica de procesamiento de superficies en frío que en metales se usa para aumentar la vida bajo esfuerzos cíclicos. En este caso, el granallado se aplicó a muestras de acero SAE5160H (usado en resortes de ballesta) templado en aceite y revenido a 460 °C. En este estudio, se midieron esfuerzos residuales por medio de difracción de rayos X (DRX) y la dureza en la superficie perpendicular al tratamiento usando una combinación de pulido para metalografía y microdureza Vickers. Para el material procesado con granallado, las mediciones superficiales de DRX arrojaron una media de 365.8 MPa en compresión y una microdureza máxima de 525 ± 92.7 HVN. Por otro lado, para el material no procesado, se obtuvo una tensión residual positiva promedio de 54.2 MPa y 433 ± 39,5 HVN. Adicionalmente, ensayos de potencial electroquímico arrojaron que el granallado aumenta el potencial de corrosión, lo que hace este proceso indeseable si el componente granallado está expuesto a ambientes agresivos. La combinación de técnicas experimentales usadas permite estimar el cambio de dureza en la superficie perpendicular al granallado en mediciones discretas tan juntas como 10µm, pero con una preparación de probeta más simple que la requerida por otras técnicas como DRX o las galgas extensiométricas. Dicha combinación se puede ser alternativa para la estimación de esfuerzos residuales a través de la profundidad.

The influence of various electrolysis parameters, such as selected operating current regime, the cathode material type, composition and mixing conditions of the electrolyte and electrodeposition time, on the structural-morphological characteristics of the copper coatings has been investigated. Morphology and structure of the coatings were analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM). Characterization of mechanical performance, such as microhardness of the coating, was done using the Vickers microindentation test. The absolute hardness of Cu coatings was determined by application of the composite hardnes models, named the Chicot−Lesage (C−L). Based on this model, it is determined the critical relative indentation depth (RID)c of 0.14, independent of all examined parameters of the electrodeposition. Depending on the electrolyte type, two different Cu coatings were obtained: fine-grained microcrystalline coatings with a strong (220) preferred orientation from the basic sulfate electrolyte and smooth mirror bright nanocrystalline coatings with a strong (200) preferred orientation from the electrolyte with added leveling/brightening additives. The „softening effect“ of mirror bright coatings obtained in the presence of a combination of additives is explained by the grain boundary phenomenon. Two different substrates: monocrystalline silicon Si(111) and polycrystalline brass alloy, were selected for comparative analysis of composite hardness., Istražen je uticaj različitih parametara elektrolize, kao što je izbor radnog režima struje, katodnog materijala, sastav i uslovi mešanja elektrolita i vreme taloženja, na strukturno-morfološke karakteristike bakarnih prevlaka. Analizirana je morfologija i struktura prevlaka pomoću skenirajućeg elektronskog mikroskopa (SEM) i mikroskopa na principu atomskih sila (AFM). Karakterizacija mehaničkih performansi, kao što je mikrotvrdoća prevlaka, urađena je korišćenjem mikro utiskivača po Vikersovom testu. Apsolutna tvrdoća bakarnih prevlaka je određena primenom modela kompozitne tvrdoće, pod nazivom Šiko−Lezaž (Š−L). Na osnovu ovog modela određena je kritična relativna dubina utiskivanja (RDU) od 0,14 koja je bila nezavisna od svih ispitivanih parametara elektrohemijskog taloženja. U zavisnosti od tipa elektrolita, dobijene su dve različite prevlake bakra: sitnozrna mikrokristalna prevlaka bakra iz osnovnog sulfatnog elektrolita sa izraženom (220) preferencijalnom orijentacijom i glatka ogledalasto sjajna nanokristalna prevlaka bakra sa izraženom (200) preferencijalnom orijentacijom iz elektrolita sa dodatkom aditiva za poravnanje/sjaj. „Efekat omekšavanja” ogledalasto sjajnih prevlaka dobijenih u prisustvu kombinacije aditiva je objašnjen preko fenomena uticaja granice zrna. Za uporednu analizu tvrdoće kompozita odabrana su dva različita supstrata: monokristalni silicijum Si(111) i polikristalna legura mesinga.

The influence of various electrolysis parameters, such as selected operating current regime, the cathode material type, composition and mixing conditions of the electrolyte and electrodeposition time, on the structural-morphological characteristics of the copper coatings has been investigated. Morphology and structure of the coatings were analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM). Characterization of mechanical performance, such as microhardness of the coating, was done using the Vickers microindentation test. The absolute hardness of Cu coatings was determined by application of the composite hardnes models, named the Chicot−Lesage (C−L). Based on this model, it is determined the critical relative indentation depth (RID)c of 0.14, independent of all examined parameters of the electrodeposition. Depending on the electrolyte type, two different Cu coatings were obtained: fine-grained microcrystalline coatings with a strong (220) preferred orientation from the basic sulfate electrolyte and smooth mirror bright nanocrystalline coatings with a strong (200) preferred orientation from the electrolyte with added leveling/brightening additives. The „softening effect“ of mirror bright coatings obtained in the presence of a combination of additives is explained by the grain boundary phenomenon. Two different substrates: monocrystalline silicon Si(111) and polycrystalline brass alloy, were selected for comparative analysis of composite hardness., Istražen je uticaj različitih parametara elektrolize, kao što je izbor radnog režima struje, katodnog materijala, sastav i uslovi mešanja elektrolita i vreme taloženja, na strukturno-morfološke karakteristike bakarnih prevlaka. Analizirana je morfologija i struktura prevlaka pomoću skenirajućeg elektronskog mikroskopa (SEM) i mikroskopa na principu atomskih sila (AFM). Karakterizacija mehaničkih performansi, kao što je mikrotvrdoća prevlaka, urađena je korišćenjem mikro utiskivača po Vikersovom testu. Apsolutna tvrdoća bakarnih prevlaka je određena primenom modela kompozitne tvrdoće, pod nazivom Šiko−Lezaž (Š−L). Na osnovu ovog modela određena je kritična relativna dubina utiskivanja (RDU) od 0,14 koja je bila nezavisna od svih ispitivanih parametara elektrohemijskog taloženja. U zavisnosti od tipa elektrolita, dobijene su dve različite prevlake bakra: sitnozrna mikrokristalna prevlaka bakra iz osnovnog sulfatnog elektrolita sa izraženom (220) preferencijalnom orijentacijom i glatka ogledalasto sjajna nanokristalna prevlaka bakra sa izraženom (200) preferencijalnom orijentacijom iz elektrolita sa dodatkom aditiva za poravnanje/sjaj. „Efekat omekšavanja” ogledalasto sjajnih prevlaka dobijenih u prisustvu kombinacije aditiva je objašnjen preko fenomena uticaja granice zrna. Za uporednu analizu tvrdoće kompozita odabrana su dva različita supstrata: monokristalni silicijum Si(111) i polikristalna legura mesinga.

For the machining of long and narrow surfaces and when processing multiple pieces, planing technology is used, the productivity of which can be higher than that of milling, although it is relatively slow machining. The article aims to study the degree of influence of the geometry of the tool (the angle of cutting-edge inclination and the angle of the tool-orthogonal rake), as well as the cutting conditions (cutting depth and cutting speed) on the chip characteristics (temperature and microhardness) in orthogonal and oblique slow-rate machining of steel 1.0503 (EN C45). The experiments were carried out on specially prepared workpieces designed for immediate stopping of machining. The results of the experiments were statistically processed, and behavioural models were created for temperature and Vickers microhardness of chips for individual combinations of factors. The obtained dependencies revealed how the geometry of the cutting tool and the cutting conditions affect the temperature and microhardness in the cutting area and at the same time allowed the best conditions for both orthogonal and oblique machining to be set up.

OBJECTIVE: The aim of this study was to investigate the effect of preheating three bulk-fill and one conventional composite resin on the Vickers microhardness and depth of cure of these composites. METHODS: In this study, three bulk-fill composites-SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), and one conventional composite resin G-ænial POSTERIOR (GP) were used as the control group. The samples were obtained at room temperature (24°C) and at 55°C in T2 mode after being placed in a heating device for 10 minutes. The samples were divided into eight groups (n=10) according to the type of material and heating process that was utilized (preheated and nonheated). All samples were tested with a Vickers microhardness (VHN) tester on the bottom and top surfaces. The first measurements were obtained at baseline; the second set of measurements was performed after the samples were stored in distilled water at 37°C for 24 hours. The depth of cure was calculated using a bottom/top hardness ratio of measurements. Statistical analysis was performed utilizing the SPSS V23 and Shapiro-Wilk tests. Lastly, the Duncan test was used for multiple comparisons (p<0.05). RESULTS: While the VHN increased after the preheating procedure in bulk-fill composites, it decreased in GP. There was no difference between the baseline and the 24-hour VHN values in SDR and GP. After 24 hours, while the VHN of EST increased, the VHN of AFX decreased. There was no difference between the hardness ratios of the AFX and EST samples (p<0.001) and hardness ratios were greater than GP and SDR. CONCLUSION: When comparing the baseline and the 24-hour values, the VHN depended on the type of materials. Sufficient curing depth was obtained in all groups with a thickness of 2mm., OBJETIVO: El objetivo de este estudio fue investigar el efecto del precalentamiento de tres resinas Bulk-fill y una resina compuesta convencional sobre la microdureza Vickers y la profundidad de curado de estas resinas. MÉTODOS: En este estudio, se utilizaron tres composites Bulk-Fill-SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), y una resina compuesta convencional G-ænial POSTERIOR (GP) como grupo de control. Las muestras se obtuvieron a temperatura ambiente (24°C) y a 55°C en modo T2 después de haber sido colocadas en un dispositivo de calentamiento durante 10 minutos. Las muestras se dividieron en ocho grupos (n=10) según el tipo de material y el proceso de calentamiento que se utilizó (precalentado y no calentado). Todas las muestras se probaron con un medidor de microdureza Vickers (VHN) en las superficies inferior y superior. Las primeras mediciones se obtuvieron en la línea de base; la segunda serie de mediciones se realizó después de que las muestras se almacenaran en agua destilada a 37°C durante 24 horas. La profundidad de curado se calculó utilizando una relación de dureza inferior/superior de las mediciones. El análisis estadístico se realizó utilizando el SPSS V23 y las pruebas de Shapiro-Wilk. Por último, se utilizó la prueba de Duncan para las comparaciones múltiples (p<0,05). RESULTADOS: Mientras que el VHN aumentó tras el procedimiento de precalentamiento en las resina Bulk-Fill, disminuyó en los GP. No hubo diferencias entre los valores de VHN de referencia y de 24 horas en SDR y GP. Después de 24 horas, mientras que el VHN de EST aumentó, el VHN de AFX disminuyó. No hubo diferencias entre los ratios de dureza de las muestras de AFX y EST (p<0,001) y los ratios de dureza fueron mayores que los de GP y SDR. CONCLUSIÓN: Al comparar los valores de referencia y los de 24 horas, el VHN dependió del tipo de materiales. Se obtuvo una profundidad de curado suficiente en todos los grupos con un grosor de 2mm.

In this paper, selective laser melting fabricated specimens in non-heat-treated and heat-treated conditions were subjected to Vickers microhardness testing, by using a full range of loadings: 10, 25, 50, 100, 200, 300, 500, and 1000 g. Microhardness of longitudinal sections and cross-sections were correlated and the obtained values were plotted against loadings and indentation size effect was studied, in order to find the optimal loading range, that gives the material true microhardness, or load-independent hardness. The load dependence of the measured Vickers hardness values was described quantitatively through the application of the Meyer's law, proportional specimen resistance, and the modified proportional specimen resistance model. It was found that the microhardness rises as the loading is higher, causing a reversed indentation size effect, clearly indicating the range of true hardnesses of the tested material. Also, proportional specimen resistance and modified proportional specimen resistance models were found to have the highest correlation factors indicating their higher adequacy compared to Meyer's prediction model.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

Fine-grained nickel coatings were electrodeposited by direct current (dc) regime onto different substrates: polycrystalline cold-rolled copper, polycrystalline brass and single crystal (100)-oriented silicon. These composite structures belong to different type of laminated composite systems. The influence of the substrate material and coating plating parameters on microstructural and mechanical properties, such as hardness and adhesion, was characterized by the Vickers microindentation test for different loads. Above critical indentation depth (usually around 10% of the coating thickness), the measured hardness is the so-called “composite hardness”, because the substrate participates in the plastic deformations during indentation. Three composite hardness models (Korsunsky, Chicot-Lesage and Chen-Gao), constructed on different principles, were chosen for fitting the experimental results in order to determine the coating hardness and the critical reduced depth as the adhesion parameter. The coating hardness is mainly influenced by the current density, because increase in current density leads to decrease in grain size and increase in coating hardness. The critical reduced depth as the parameter of adhesion depends on the substrate material.

In this research paper, overlapped multipass Laser Transformation Hardening (LTH) of Ti-6Al-4V titanium alloy sheet of 2 mm thickness was analyzed experimentally for uniformly intense, CW spherical beam moving with constant speed using 2 kW Nd: YAG laser. Experiments were conducted for optimized two sets of laser process parameters: 1. High Laser Process Parameter (HLPP), Lp = 800 Watts, Ss = 3000 mm/min, Fp = -10 mm, with heat input 180 J/cm and 2. Low Laser Process Parameter (LLPP), Lp = 600 Watts, Ss = 2000 mm/min, Fp = -10 mm, with heat input 160 J/cm respectively having same Fp = -10 mm. The maximum, minimum and average hardened depths of 0.27, 0.19 and 0.23 mm respectively, achieved for HLPP were found to be minimum, as compared to the maximum, minimum and average hardened depths of 0.38, 0.29 and 0.33 mm, respectively, for LLPP. Measurements of Vickers micro-hardness survey of the hardened zone of the laser processed Ti-6Al-4V alloy are presented. Vickers micro-hardness of an as-received two-phase (α+β) Ti-6Al-4V titanium alloy is 328 HV. The results showed that Vickers micro-hardness on top of the surface (TS), in hardened or fusion zone (Fz), at the interface of Fz -Haz, in the heat affected zone (Haz) is higher than the bulk material. The high hardness values of 450 HV and 445 HV were investigated on the top surface for high and low laser process parameters respectively. This can be the quality characteristics of the dissolution of small amounts of oxygen, nitrogen, and carbon with hard martensite α' (transformed β) formation, thereby ensuring an increase in wear resistance of laser treated hardened surface of Ti-6Al-4V considerably in relation to the untreated or base alloy.

In this research paper, overlapped multipass Laser Transformation Hardening (LTH) of Ti-6Al-4V titanium alloy sheet of 2 mm thickness was analyzed experimentally for uniformly intense, CW spherical beam moving with constant speed using 2 kW Nd: YAG laser. Experiments were conducted for optimized two sets of laser process parameters: 1. High Laser Process Parameter (HLPP), Lp = 800 Watts, Ss = 3000 mm/min, Fp = -10 mm, with heat input 180 J/cm and 2. Low Laser Process Parameter (LLPP), Lp = 600 Watts, Ss = 2000 mm/min, Fp = -10 mm, with heat input 160 J/cm respectively having same Fp = -10 mm. The maximum, minimum and average hardened depths of 0.27, 0.19 and 0.23 mm respectively, achieved for HLPP were found to be minimum, as compared to the maximum, minimum and average hardened depths of 0.38, 0.29 and 0.33 mm, respectively, for LLPP. Measurements of Vickers micro-hardness survey of the hardened zone of the laser processed Ti-6Al-4V alloy are presented. Vickers micro-hardness of an as-received two-phase (α+β) Ti-6Al-4V titanium alloy is 328 HV. The results showed that Vickers micro-hardness on top of the surface (TS), in hardened or fusion zone (Fz), at the interface of Fz -Haz, in the heat affected zone (Haz) is higher than the bulk material. The high hardness values of 450 HV and 445 HV were investigated on the top surface for high and low laser process parameters respectively. This can be the quality characteristics of the dissolution of small amounts of oxygen, nitrogen, and carbon with hard martensite α' (transformed β) formation, thereby ensuring an increase in wear resistance of laser treated hardened surface of Ti-6Al-4V considerably in relation to the untreated or base alloy.

One of the main objectives in research and development of resin based cements (RBCs) is to enhance their clinical longevity and ease of use. In spite of the undeniable technological advances introduced in the last few decades, the polymerization shrinkage i.e. strain that accompanies the chain-growth polymerization of dimethacrylate monomers remains one of the major concerns for the clinical performance of composite restorations. Also, RBCs can produce a considerable amount of heat, due to the light energy from the curing lights and exothermic reaction of polymerization. The purpose of this study was to determine the temperature changes during the photo-polymerization using thermocouples and to measure strain field of the self-etching, self-adhesive RBC, Maxcem Elite (Kerr, Orange, CA, USA) (empty set5 x 1 mm - Group I and empty set5 x 2 mm - Group II) using experimental technique, 3D Digital Image Correlation (DIC) method. Digital images were recorded immediately after photo-polymerization of the samples with a LED-curing unit for 20 s, according to manufacturer's recommendation. Vickers microhardness was determined after photo-polymerization and after 24 h. Temperature curves for both groups indicated similar patterns but the peak temperature of Group II was significantly higher compared to peak temperature of Group I. DIC showed that peripheral zone of the samples had the highest strain values in both groups. Group I indicated significantly higher values of hardness. All the results were material-dependent and probably correlated to the composition of each material, which is not fully disclosed by the manufacturers.

The fatigue behaviour of SAE 5160 steel was evaluated before and after applying a shot peening process by using different Almen intensities and surface coverings (uncovered, partial coverage and total coverage). In the high-cycle fatigue tests, maximum stresses of 0.8Sut, 0.7Sut and 0.6Sut were applied in the three-point bending test on an Instron 8872 servo-hydraulic machine at a frequency of 10 Hz and a constant stress ratio of Smin/Smax¿=¿0.2 for all tests. The fatigue tests were performed based on the ASTM E8, the specimens were classified into six groups for each stress evaluated, and each group consisted of three standardised specimens (ASTM E466). Also, yield strength, ultimate strength, hardness and microhardness were obtained. The Wilcoxon’s non-parametric test was used to statistically compare all the mechanical properties obtained from the base material with those obtained after the application of the shot peening, for the different surface coverings and Almen intensities. The results showed that the shot peening process significantly increases the fatigue strength of the material, with a 94% increase in fatigue strength of the fully coated specimens. However, no significant increase in fatigue strength was found due to a change in the Almen intensity value. A high correlation factor was found between the increase in the ultimate resistance and the increase in Almen intensity; however, for the yield stress the correlation was medium and inverse. For hardness and microhardness, the correlation factor was very low. Finally, the microhardness values revealed a 3% increase in Vickers microhardness of the shot peening specimens compared to the untreated specimens., Peer Reviewed, Postprint (author's final draft)

One of the main objectives in research and development of resin based cements (RBCs) is to enhance their clinical longevity and ease of use. In spite of the undeniable technological advances introduced in the last few decades, the polymerization shrinkage i.e. strain that accompanies the chain-growth polymerization of dimethacrylate monomers remains one of the major concerns for the clinical performance of composite restorations. Also, RBCs can produce a considerable amount of heat, due to the light energy from the curing lights and exothermic reaction of polymerization. The purpose of this study was to determine the temperature changes during the photo-polymerization using thermocouples and to measure strain field of the self-etching, self-adhesive RBC, Maxcem Elite (Kerr, Orange, CA, USA) (ø5 × 1Â mm - Group I and ø5 × 2Â mm - Group II) using experimental technique, 3D Digital Image Correlation (DIC) method. Digital images were recorded immediately after photo-polymerization of the samples with a LED-curing unit for 20Â s, according to manufacturer’s recommendation. Vickers microhardness was determined after photo-polymerization and after 24Â h. Temperature curves for both groups indicated similar patterns but the peak temperature of Group II was significantly higher compared to peak temperature of Group I. DIC showed that peripheral zone of the samples had the highest strain values in both groups. Group I indicated significantly higher values of hardness. All the results were material-dependent and probably correlated to the composition of each material, which is not fully disclosed by the manufacturers. © Springer Nature Switzerland AG 2019.

Composite systems of monolayered electrodeposited Ni and Cu thin films (5-10 μm) on monocrystalline Si wafers and 50 μm-thick electrodeposited Ni film as the substrates were fabricated. On the basis of their difference in hardness, these systems can be thought of as “soft film on hard substrate” composite systems. Adhesion of electrodeposited films on different substrates was investigated by Vickers microindentation hardness testing. Strong adhesion corresponds to extended plastic deformation zone at the film/substrate interface. Interfacial tension effects contribute to the measured hardness. Composite hardness models of Chicot-Lesage (C-L) and Chen-Gao (C-G) were applied in order to investigate the influence of adhesion on microhardness test results. When adhesion exists between the film and the substrate, the critical reduced depth (the ratio between the radius of the plastic zone beneath the indent and the indentation depth) increases. Microhardness measurements are useful tool for assessment and quantification of the film/substrate interface strength.

Composite systems of monolayered electrodeposited Ni and Cu thin films (5-10 μm) on monocrystalline Si wafers and 50 μm-thick electrodeposited Ni film as the substrates were fabricated. On the basis of their difference in hardness, these systems can be thought of as “soft film on hard substrate” composite systems. Adhesion of electrodeposited films on different substrates was investigated by Vickers microindentation hardness testing. Strong adhesion corresponds to extended plastic deformation zone at the film/substrate interface. Interfacial tension effects contribute to the measured hardness. Composite hardness models of Chicot-Lesage (C-L) and Chen-Gao (C-G) were applied in order to investigate the influence of adhesion on microhardness test results. When adhesion exists between the film and the substrate, the critical reduced depth (the ratio between the radius of the plastic zone beneath the indent and the indentation depth) increases. Microhardness measurements are useful tool for assessment and quantification of the film/substrate interface strength.

Ni-Co coatings with various cobalt contents were electrodeposited from modified Watts bath. The effect of cobalt content on electrodeposition mechanism of the coatings was studied by electro-chemical impedance spectroscopy method (EIS). Surface morphology and crystallographic structure of the coatings were investigated by means of SEM and XRD. Mechanical properties of the coatings were determined using Vickers microhardness and tensile tests. It was found that with increasing the Co2+ ions in electroplating bath, the charge transfer resistance (Rct) of Ni-Co film increased whereas the Warburg impedence decreased. This may be due to enhancement in coverage of cathode surface by Co(OH)2 and higher diffusion rate of metal ions towards cathode surface, respectively. Also, with increasing the cobalt content in the bath, cobalt content in the alloy coating increased anomalously and (111) texture consolidated gradually. With increasing the cobalt content up to 45% in alloy coating, the grain size decreased and consequently, hardness and strength of the alloy increased. Further enhancement of cobalt content up to 55% led to a little decrease in hardness and strength. The maximum ductility was observed for Ni-25%Co coating due to relatively small grain size and compact structure. © 2016 The Nonferrous Metals Society of China.

This investigation has been carried out in order to analyse and compare the hardness response of different composite systems of the same type, named 'soft film on hard substrate' composite system. Composite systems of mono- and multilayered electrodeposited Ni and Cu thin films on (100) and (111)-oriented monocrystalline Si wafers and 100 µm-thick electrodeposited Ni film as the substrates were fabricated. The indentation behaviour of these composite structures was characterized using Berkovich nanohardness and Vickers microhardness testing. The measured hardness is so-called 'composite hardness', because the substrate participates in the plastic deformation during the indentation process. The contribution of the substrate to the measured hardness starts at indentation depths of the order of 0.07- 0.2 times the film thickness. Dependence of nanohardness and microhardness values on electrodeposition process conditions, substrate and film microstructure, total film thickness, layer thickness and Ni/Cu layer thickness ratio for different composite systems ratio was investigated. Composite hardness model of Chicot-Lesage (C-L) was chosen and applied to experimental data in order to determine absolute film hardness., Ovo istraživanje je izvršeno u cilju analize i upoređivanja odziva različitih kompozitnih sistema koji pripadaju istom tipu sistema nazvanom 'mek film na tvrdom supstratu', pri merenju tvrdoće. Formirani su kompozitni sistemi elektrodepozicijom jedno- i višeslojnih Ni i Cu tankih filmova na (100) i (111)- orijentisanim monokristalnim Si pločicama i 100-µm debelom elektrodeponovanom Ni filmu kao supstratima. Ponašanje ovih kompozitnih struktura pri utiskivanju je okarakterisano merenjem nanotvrdoće po Berkoviču i mikrotvrdoće po Vikersu. Izmerena vrednost mikrotvrdoće se naziva 'kompozitnom tvrdoćom' jer prilikom testiranja utiskivanjem dolazi i do plastične deformacije supstrata. Doprinos deformacije supstrata izmerenoj tvrdoći počinje na dubinama utiskivanja koje su reda 0.07-0.2 puta manje od debljine filma. Istraživana je zavisnost vrednosti nanotvrdoće i mikrotvrdoće od procesnih parametera elektrodepozicije, mikrostrukture supstrata i filmova, ukupne debljine filma, debljine pojedinačnog sloja u filmu i odnosa debljina Ni/Cu pojedinačnih slojeva u filmu za različite kompozitne sisteme. Radi određivanja apsolutne tvrdoće filma u sistemu, odabran je i na eksperimentalne rezultate primenjen model kompozitne tvrdoće Šiko-Lezaž (C-L).

Composite resins are the material election to restored minimal invasive cavities; conversely, it is important to explore their mechanical properties of commercial available dental materials. Objective: To compare the Vickers microhardness (VHN) of four available commercial composite resins of standardized samples and methods. Methodology: Composite cylinders were performed in a Teflon mould. We use the follow composite resins (n=4/gp): Microhybrid resins [Feeling Lux (Viarden) and Amelogen Plus (Ultradent)], Hybrid resin [Te-Econom Plus (Ivoclar)] and Nanohybrid resin [Filtek Z350 (3M ESPE)]. All samples were incubated in distilled water at 37 ºC for five days. The test was carried out with microhardness indenter at 10 N, and a dwelling time of 10 s for 9 indentations across the specimens resulting in a total of 36 indentations for each group. Data were subject to Kolmogorov-Smirnov normality test and ANOVA (post-hoc) Tukey test. Results: The VHN mean values corresponded from harder to softer as follow: Filtek Z350 (71.96±6.44) (p˂0.01)˃Amelogen Plus (59.90±4.40) (p˂0.05)˃Feeling lux (53.52±5.72)˃Te-Econom Plus (53.26±5.19). Conclusion: According to our results, the microhardness of the evaluated conventional composite resin can withstand the masticatory forces but nanohybrid composite resins showed better Vickers microhardness that clinically can results in suitable option for restored minimal invasion treatments., Las resinas son los materiales de elección para restaurar cavidades mínimamente invasivas, sin embargo, es importante conocer sus propiedades mecánicas de los materiales dentales disponibles comerciales. Objetivo: Comparar la microdureza Vickers (VHN) de cuatro resinas compuestas comerciales disponibles con muestras y métodos estandarizados. Metodología: Cilindros de resina compuesta fueron conformados en un molde de Teflón. Se utilizaron las siguientes resinas compuestas (n=4/gp): resina microhíbrida [Feeling Lux (Viarden) y Amelogen Plus (Ultradent)], resina híbrida [Te-Econom Plus (Ivoclar)] y resina nanohíbrida [Filtek Z350 (3M ESPE)]. Todas las muestras fueron incubadas en agua destilada a 37 °C durante cinco días. El análisis fue realizado con un indentador de microdureza a 10 N y 10 s de presión sobre la muestra, nueve indentaciones fueron realizadas a lo largo de la muestra resultando un total de 36 indentaciones por cada grupo. Los datos fueron sometidos a prueba de normalidad de Kolmogorov-Smirnov y un análisis de ANOVA (post-hoc) de Tukey. Resultados: Los valores de VHN correspondieron de la resina más dura a la más suave como se muestra a continuación: Filtek Z350 (71.96±6.44) (p˂0.01)˃Amelogen Plus (59.90±4.40) (p˂0.05)˃Feeling lux (53.52±5.72)˃Te-Econom Plus (53.26±5.19). Conclusiones: De acuerdo con nuestros resultados, la dureza de las resinas compuestas convencionales evaluadas puede soportar las fuerzas masticatorias pero las resinas compuestas nanohíbridas mostraron una mejor microdureza Vickers que clínicamente puede resultar como una adecuada opción para restaurar tratamientos mínimamente invasivos.

This investigation has been carried out in order to analyse and compare the hardness response of different composite systems of the same type, named 'soft film on hard substrate' composite system. Composite systems of mono- and multilayered electrodeposited Ni and Cu thin films on (100) and (111)-oriented monocrystalline Si wafers and 100 µm-thick electrodeposited Ni film as the substrates were fabricated. The indentation behaviour of these composite structures was characterized using Berkovich nanohardness and Vickers microhardness testing. The measured hardness is so-called 'composite hardness', because the substrate participates in the plastic deformation during the indentation process. The contribution of the substrate to the measured hardness starts at indentation depths of the order of 0.07- 0.2 times the film thickness. Dependence of nanohardness and microhardness values on electrodeposition process conditions, substrate and film microstructure, total film thickness, layer thickness and Ni/Cu layer thickness ratio for different composite systems ratio was investigated. Composite hardness model of Chicot-Lesage (C-L) was chosen and applied to experimental data in order to determine absolute film hardness., Ovo istraživanje je izvršeno u cilju analize i upoređivanja odziva različitih kompozitnih sistema koji pripadaju istom tipu sistema nazvanom 'mek film na tvrdom supstratu', pri merenju tvrdoće. Formirani su kompozitni sistemi elektrodepozicijom jedno- i višeslojnih Ni i Cu tankih filmova na (100) i (111)- orijentisanim monokristalnim Si pločicama i 100-µm debelom elektrodeponovanom Ni filmu kao supstratima. Ponašanje ovih kompozitnih struktura pri utiskivanju je okarakterisano merenjem nanotvrdoće po Berkoviču i mikrotvrdoće po Vikersu. Izmerena vrednost mikrotvrdoće se naziva 'kompozitnom tvrdoćom' jer prilikom testiranja utiskivanjem dolazi i do plastične deformacije supstrata. Doprinos deformacije supstrata izmerenoj tvrdoći počinje na dubinama utiskivanja koje su reda 0.07-0.2 puta manje od debljine filma. Istraživana je zavisnost vrednosti nanotvrdoće i mikrotvrdoće od procesnih parametera elektrodepozicije, mikrostrukture supstrata i filmova, ukupne debljine filma, debljine pojedinačnog sloja u filmu i odnosa debljina Ni/Cu pojedinačnih slojeva u filmu za različite kompozitne sisteme. Radi određivanja apsolutne tvrdoće filma u sistemu, odabran je i na eksperimentalne rezultate primenjen model kompozitne tvrdoće Šiko-Lezaž (C-L).

This investigation has been carried out in order to analyse and compare the hardness response of different composite systems of the same type, named 'soft film on hard substrate' composite system. Composite systems of mono- and multilayered electrodeposited Ni and Cu thin films on (100) and (111)-oriented monocrystalline Si wafers and 100 µm-thick electrodeposited Ni film as the substrates were fabricated. The indentation behaviour of these composite structures was characterized using Berkovich nanohardness and Vickers microhardness testing. The measured hardness is so-called 'composite hardness', because the substrate participates in the plastic deformation during the indentation process. The contribution of the substrate to the measured hardness starts at indentation depths of the order of 0.07- 0.2 times the film thickness. Dependence of nanohardness and microhardness values on electrodeposition process conditions, substrate and film microstructure, total film thickness, layer thickness and Ni/Cu layer thickness ratio for different composite systems ratio was investigated. Composite hardness model of Chicot-Lesage (C-L) was chosen and applied to experimental data in order to determine absolute film hardness., Ovo istraživanje je izvršeno u cilju analize i upoređivanja odziva različitih kompozitnih sistema koji pripadaju istom tipu sistema nazvanom 'mek film na tvrdom supstratu', pri merenju tvrdoće. Formirani su kompozitni sistemi elektrodepozicijom jedno- i višeslojnih Ni i Cu tankih filmova na (100) i (111)- orijentisanim monokristalnim Si pločicama i 100-µm debelom elektrodeponovanom Ni filmu kao supstratima. Ponašanje ovih kompozitnih struktura pri utiskivanju je okarakterisano merenjem nanotvrdoće po Berkoviču i mikrotvrdoće po Vikersu. Izmerena vrednost mikrotvrdoće se naziva 'kompozitnom tvrdoćom' jer prilikom testiranja utiskivanjem dolazi i do plastične deformacije supstrata. Doprinos deformacije supstrata izmerenoj tvrdoći počinje na dubinama utiskivanja koje su reda 0.07-0.2 puta manje od debljine filma. Istraživana je zavisnost vrednosti nanotvrdoće i mikrotvrdoće od procesnih parametera elektrodepozicije, mikrostrukture supstrata i filmova, ukupne debljine filma, debljine pojedinačnog sloja u filmu i odnosa debljina Ni/Cu pojedinačnih slojeva u filmu za različite kompozitne sisteme. Radi određivanja apsolutne tvrdoće filma u sistemu, odabran je i na eksperimentalne rezultate primenjen model kompozitne tvrdoće Šiko-Lezaž (C-L).

Thin metallic multilayer films consisting of nanometer layer thickness deposited on different substrates have shown promising mechanical, electrical and magnetical properties, especially for applications in fabrication of microelectromechanical (MEMS) structures and wear-resistant applications. Electrodeposition of Ni/Cu multilayer films on substrates of (111)-oriented single crystal Si and 100μm-thick electrodeposited Ni film was carried out using dual-bath technique (DBT). The current density values was maintained at 10 mA cm-2 and projected thickness of deposit was 5μm. Vickers microhardness of Ni/Cu thin multilayer films was investigated. The substrate starts to contribute the measured hardness at penetration depths of the order of 0.07 - 0.20 times the film thickness. The measured “composite hardness” is a complex value that depends on the microstructure and the hardness of the film and the substrate and their relative differences. Ni/Cu films on (111)-oriented Si wafer and 100μm-thick electrodeposited Ni film as the substrates can be thought as “soft film on hard substrate” composite systems. Chicot-Lesage model based on the model for reinforced composites can be applied to experimental data for all specimen and the film hardness was calculated for each indentation diagonal. The values obtained for the film hardness HF are not constant for all types of these composite systems, but influenced by the applied load.

Thin metallic multilayer films consisting of nanometer layer thickness deposited on different substrates have shown promising mechanical, electrical and magnetical properties, especially for applications in fabrication of microelectromechanical (MEMS) structures and wear-resistant applications. Electrodeposition of Ni/Cu multilayer films on substrates of (111)-oriented single crystal Si and 100μm-thick electrodeposited Ni film was carried out using dual-bath technique (DBT). The current density values was maintained at 10 mA cm-2 and projected thickness of deposit was 5μm. Vickers microhardness of Ni/Cu thin multilayer films was investigated. The substrate starts to contribute the measured hardness at penetration depths of the order of 0.07 - 0.20 times the film thickness. The measured “composite hardness” is a complex value that depends on the microstructure and the hardness of the film and the substrate and their relative differences. Ni/Cu films on (111)-oriented Si wafer and 100μm-thick electrodeposited Ni film as the substrates can be thought as “soft film on hard substrate” composite systems. Chicot-Lesage model based on the model for reinforced composites can be applied to experimental data for all specimen and the film hardness was calculated for each indentation diagonal. The values obtained for the film hardness HF are not constant for all types of these composite systems, but influenced by the applied load.

Introduction The aim of this study was to investigate the proper time to restore composite resin over mineral trioxide aggregate (MTA). Methods Thirty-five samples of MTA blocks were divided into 7 groups with 3 different times (10 minutes, 1 day, and 7 days) selected for restoring the composite resin over MTA with and without bonding resin, and a control group was included for comparison. After 21 days, the distances between MTA and the composite resin or between MTA and the bonding agent on sectioned planes along the long axis were measured using a scanning electron microscope (×2,000 magnification). The hardness of the MTA near the composite resin was presented as the Vickers microhardness. Results There were no gaps at the interface in the 10-minute groups, the 1-day group with a bonding agent, and the 7-day group with a bonding agent. The groups without a bonding agent at 1 and 7 days presented a separation or gap at the interface. The value of the Vickers microhardness in the 1-day groups was significantly decreased compared with those of the other groups regardless of the presence or absence of a bonding agent. Conclusions These findings suggest that composite resin with a bonding agent over MTA can be restored almost immediately after MTA mixing during a single visit., Journal of Endodontics, 39(9), pp.1167-1170; 2013

Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on massive electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testing for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth,1 when a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in order to analyse and determine the absolute film hardness. Further analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems.

Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on massive electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testing for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth,1 when a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in order to analyse and determine the absolute film hardness. Further analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems.

Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on massive electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testing for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth,1 when a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in order to analyse and determine the absolute film hardness. Further analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems.

Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on massive electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testing for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth,1 when a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in order to analyse and determine the absolute film hardness. Further analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems.

Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness.

Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness.

Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness.

Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness.

Маtеriјаli kојi sе kоristе u mikrоеlеktrоmеhаničkim sistеmimа (МЕМS) su nајčеšćе u оbliku tаnkih filmоvа kојi su dеpоnоvаni nа supstrаtimа ili fоrmirајu kоmpоzitе sа drugim filmоvimа. Таnkе višеslојnе strukturе imајu spеcifičnа еlеktričnа, mеhаničkа, mаgnеtnа i оptičkа svојstvа i zbоg tоgа imајu pоtеnciјаlа zа širоku primеnu u prоizvоdnji intеgrisаnih kоlа, izrаdi mаgnеtnih glаvа i rаzličitih kоmpоnеnti u МЕМS urеđајimа. Pоrеd tоgа, mаtеriјаli kојi su u оbliku tаnkоg filmа dеpоnоvаni nа supstrаt mоrајu biti kоmpаtibilni sа оsnоvnim mikrоеlеktrоnskim tеhnоlоgiјаmа - litоgrаfiјоm, nаgrizаnjеm, priprеmоm spојеvа, hеmiјskо-mеhаničkim pоlirаnjеm i kоnаčnо mеtоdаmа mоntаžе МЕМS urеđаја. Pоuzdаnоst urеđаја kојi sаdržе оvе višеslојnе strukturе zаvisi оd nеkоlikо fаktоrа uklјučuјući mеhаničku stаbilnоst urеđаја, аdhеziјu slојеvа kаkо mеđusоbnu, tаkо i sа supstrаtоm, аdhеziјu sа mаtеriјаlimа zаštitnih mаski pri nаgrizаnju i pоlirаnju i drugе. Zbоg tоgа su pоtrеbnа dеtаlјnа ispitivаnjа pоuzdаnоsti i kоmpаtibilnоsti mаtеriјаlа kојi ulаzе u sklоp МЕМS urеđаја. Zа pоmеnutu mеhаničku stаbilnоst МЕМS urеđаја bitnа su slеdеćа fizičkо - mеhаničkа svојstvа: аdhеziја nа grаničnim pоvršinаmа slојеvа, mоduli еlаstičnоsti upоtrеblјеnih mаtеriјаlа, tvrdоćа i žilаvоst filmа. Меhаničkа svојstvа tаnkih filmоvа sе rаzlikuјu оd svојstаvа u zаprеmini mаtеriјаlа (bulk mаtеriјаli). Оvо sе mоžе оbјаsniti mikrо/nаnоstrukturоm tаnkih filmоvа kао i timе dа pоstојi uticај supstrаtа nа kојi је film dеpоnоvаn. Uslеd rаzlikа u tеrmо-mеhаničkim svојstvimа supstrаtа i filmа, u tаnkim filmоvimа imа dоstа zаоstаlih nаpоnа nаkоn prоcеsа dеpоnоvаnjа. Тi zаоstаli nаpоni dоvоdе dо trајnih dеfоrmаciја filmа, pа i lоmа kао i dеlаminаciје kоmpоzitnоg mаtеriјаlа ukоlikо su višеslојnа dеpоnоvаnjа u pitаnju. Zbоg tоgа su ispitivаnjа i u еlаstičnој i u plаstičnој оblаsti nаprеzаnjа i dеfоrmаciја јаkо vаžnа zа kаrаktеrizаciјu tаnkih filmоvа. Prеdmеt rаdа оvе disеrtаciје је prоcеsirаnjе lаminаtnih kоmpоzitnih sistеmа mаtе, Materials and structures with small-scale dimensions do not behave in the same manner as their bulk counterparts. This became significantly important when we deal with thin films which are routinely employed as components in microelectromechanical systems (MEMS). Thin multilayered structures have specific electric, mechanical, magnetic and optical properties and because of that have great potential for applications in fabrication of different MEMS components. Thin film materials together with their substrates have to be compatible with fundamental MEMS technologies – litography, deposition methods, etching, mechanical and chemical polishing, etc.This thesis is mainly confronted with the problem of structural and mechanical characterization of multilayered composite films. Multilayered composite systems of alternately electrodeposited nanocrystalline Cu and Ni films on cold-rolled microcrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing.The mechanical properties of the composite systems were characterized using Vickers microhardness testing. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. After the mechanical testing, samples were prepared for the examination by metalographic microscopy. Topographic details were investigated by means of atomic force microscope operating in non-contact mode.Composite hardness models of Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky were applied to the experimental data in order to determine film hardness. The applicability of mentioned models is critically tested on two types of composite systems: hard film on soft substrate and soft film on hard substrate. Korsunsky model was chosen and applied for the multilayered composite systems Ni/Cu on polycrystalline Cu substrate. These systems were considered a

Маtеriјаli kојi sе kоristе u mikrоеlеktrоmеhаničkim sistеmimа (МЕМS) su nајčеšćе u оbliku tаnkih filmоvа kојi su dеpоnоvаni nа supstrаtimа ili fоrmirајu kоmpоzitе sа drugim filmоvimа. Таnkе višеslојnе strukturе imајu spеcifičnа еlеktričnа, mеhаničkа, mаgnеtnа i оptičkа svојstvа i zbоg tоgа imајu pоtеnciјаlа zа širоku primеnu u prоizvоdnji intеgrisаnih kоlа, izrаdi mаgnеtnih glаvа i rаzličitih kоmpоnеnti u МЕМS urеđајimа. Pоrеd tоgа, mаtеriјаli kојi su u оbliku tаnkоg filmа dеpоnоvаni nа supstrаt mоrајu biti kоmpаtibilni sа оsnоvnim mikrоеlеktrоnskim tеhnоlоgiјаmа - litоgrаfiјоm, nаgrizаnjеm, priprеmоm spојеvа, hеmiјskо-mеhаničkim pоlirаnjеm i kоnаčnо mеtоdаmа mоntаžе МЕМS urеđаја. Pоuzdаnоst urеđаја kојi sаdržе оvе višеslојnе strukturе zаvisi оd nеkоlikо fаktоrа uklјučuјući mеhаničku stаbilnоst urеđаја, аdhеziјu slојеvа kаkо mеđusоbnu, tаkо i sа supstrаtоm, аdhеziјu sа mаtеriјаlimа zаštitnih mаski pri nаgrizаnju i pоlirаnju i drugе. Zbоg tоgа su pоtrеbnа dеtаlјnа ispitivаnjа pоuzdаnоsti i kоmpаtibilnоsti mаtеriјаlа kојi ulаzе u sklоp МЕМS urеđаја. Zа pоmеnutu mеhаničku stаbilnоst МЕМS urеđаја bitnа su slеdеćа fizičkо - mеhаničkа svојstvа: аdhеziја nа grаničnim pоvršinаmа slојеvа, mоduli еlаstičnоsti upоtrеblјеnih mаtеriјаlа, tvrdоćа i žilаvоst filmа. Меhаničkа svојstvа tаnkih filmоvа sе rаzlikuјu оd svојstаvа u zаprеmini mаtеriјаlа (bulk mаtеriјаli). Оvо sе mоžе оbјаsniti mikrо/nаnоstrukturоm tаnkih filmоvа kао i timе dа pоstојi uticај supstrаtа nа kојi је film dеpоnоvаn. Uslеd rаzlikа u tеrmо-mеhаničkim svојstvimа supstrаtа i filmа, u tаnkim filmоvimа imа dоstа zаоstаlih nаpоnа nаkоn prоcеsа dеpоnоvаnjа. Тi zаоstаli nаpоni dоvоdе dо trајnih dеfоrmаciја filmа, pа i lоmа kао i dеlаminаciје kоmpоzitnоg mаtеriјаlа ukоlikо su višеslојnа dеpоnоvаnjа u pitаnju. Zbоg tоgа su ispitivаnjа i u еlаstičnој i u plаstičnој оblаsti nаprеzаnjа i dеfоrmаciја јаkо vаžnа zа kаrаktеrizаciјu tаnkih filmоvа. Prеdmеt rаdа оvе disеrtаciје је prоcеsirаnjе lаminаtnih kоmpоzitnih sistеmа mаtе, Materials and structures with small-scale dimensions do not behave in the same manner as their bulk counterparts. This became significantly important when we deal with thin films which are routinely employed as components in microelectromechanical systems (MEMS). Thin multilayered structures have specific electric, mechanical, magnetic and optical properties and because of that have great potential for applications in fabrication of different MEMS components. Thin film materials together with their substrates have to be compatible with fundamental MEMS technologies – litography, deposition methods, etching, mechanical and chemical polishing, etc. This thesis is mainly confronted with the problem of structural and mechanical characterization of multilayered composite films. Multilayered composite systems of alternately electrodeposited nanocrystalline Cu and Ni films on cold-rolled microcrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The mechanical properties of the composite systems were characterized using Vickers microhardness testing. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. After the mechanical testing, samples were prepared for the examination by metalographic microscopy. Topographic details were investigated by means of atomic force microscope operating in non-contact mode. Composite hardness models of Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky were applied to the experimental data in order to determine film hardness. The applicability of mentioned models is critically tested on two types of composite systems: hard film on soft substrate and soft film on hard substrate. Korsunsky model was chosen and applied for the multilayered composite systems Ni/Cu on polycrystalline Cu substrate. These systems were considere

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness., Sitnozrne prevlake nikla su elektrodeponovane iz sulfamatnog kupatila na različitim supstratima: hladno-valjanom polikristalnom bakru i monokristalnom silicijumu (111) orijentacije. Uticaj supstrata i odabranih parametara elektrodepozicije na mehanička i strukturna svojstva ovih kompozitnih struktura ispitivan je testovima mikrotvrdoće po Vickers-u pri različitim opterećenjima. Iznad kritične dubine utiskivanja, izmerena vrednost tvrdoće nije tvrdoća elektrodeponovanog filma, već takozvana 'kompozitna mikrotvrdoća', jer supstrat učestvuje u plastičnoj deformaciji tokom procesa utiskivanja. Odabrana su dva modela kompozitne tvrdoće bazirana na različitim principima (model Chicot-Lesage i Korsunsky) i primenjena na eksperimentalne rezultate u cilju izračunavanja tvrdoće filma. Vrednosti mikrotvrdoće elektrodeponovanih prevlaka nikla zavise od vrednosti gustine struje. Povećanje gustine struje vodi smanjenju veličine zrna i povećanju vrednosti mikrotvrdoće.

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness., Sitnozrne prevlake nikla su elektrodeponovane iz sulfamatnog kupatila na različitim supstratima: hladno-valjanom polikristalnom bakru i monokristalnom silicijumu (111) orijentacije. Uticaj supstrata i odabranih parametara elektrodepozicije na mehanička i strukturna svojstva ovih kompozitnih struktura ispitivan je testovima mikrotvrdoće po Vickers-u pri različitim opterećenjima. Iznad kritične dubine utiskivanja, izmerena vrednost tvrdoće nije tvrdoća elektrodeponovanog filma, već takozvana 'kompozitna mikrotvrdoća', jer supstrat učestvuje u plastičnoj deformaciji tokom procesa utiskivanja. Odabrana su dva modela kompozitne tvrdoće bazirana na različitim principima (model Chicot-Lesage i Korsunsky) i primenjena na eksperimentalne rezultate u cilju izračunavanja tvrdoće filma. Vrednosti mikrotvrdoće elektrodeponovanih prevlaka nikla zavise od vrednosti gustine struje. Povećanje gustine struje vodi smanjenju veličine zrna i povećanju vrednosti mikrotvrdoće.

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness., Sitnozrne prevlake nikla su elektrodeponovane iz sulfamatnog kupatila na različitim supstratima: hladno-valjanom polikristalnom bakru i monokristalnom silicijumu (111) orijentacije. Uticaj supstrata i odabranih parametara elektrodepozicije na mehanička i strukturna svojstva ovih kompozitnih struktura ispitivan je testovima mikrotvrdoće po Vickers-u pri različitim opterećenjima. Iznad kritične dubine utiskivanja, izmerena vrednost tvrdoće nije tvrdoća elektrodeponovanog filma, već takozvana 'kompozitna mikrotvrdoća', jer supstrat učestvuje u plastičnoj deformaciji tokom procesa utiskivanja. Odabrana su dva modela kompozitne tvrdoće bazirana na različitim principima (model Chicot-Lesage i Korsunsky) i primenjena na eksperimentalne rezultate u cilju izračunavanja tvrdoće filma. Vrednosti mikrotvrdoće elektrodeponovanih prevlaka nikla zavise od vrednosti gustine struje. Povećanje gustine struje vodi smanjenju veličine zrna i povećanju vrednosti mikrotvrdoće.

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness., Sitnozrne prevlake nikla su elektrodeponovane iz sulfamatnog kupatila na različitim supstratima: hladno-valjanom polikristalnom bakru i monokristalnom silicijumu (111) orijentacije. Uticaj supstrata i odabranih parametara elektrodepozicije na mehanička i strukturna svojstva ovih kompozitnih struktura ispitivan je testovima mikrotvrdoće po Vickers-u pri različitim opterećenjima. Iznad kritične dubine utiskivanja, izmerena vrednost tvrdoće nije tvrdoća elektrodeponovanog filma, već takozvana 'kompozitna mikrotvrdoća', jer supstrat učestvuje u plastičnoj deformaciji tokom procesa utiskivanja. Odabrana su dva modela kompozitne tvrdoće bazirana na različitim principima (model Chicot-Lesage i Korsunsky) i primenjena na eksperimentalne rezultate u cilju izračunavanja tvrdoće filma. Vrednosti mikrotvrdoće elektrodeponovanih prevlaka nikla zavise od vrednosti gustine struje. Povećanje gustine struje vodi smanjenju veličine zrna i povećanju vrednosti mikrotvrdoće.

Fine-grained nickel thin films were electrodeposited from a self-made sulphamate-based electrolyte on different substrates: polycrystalline cold-rolled copper and single crystal silicon with two different orientations, namely (100) and (111). The influence of the substrate and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Four composite hardness models (Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky models) are chosen and applied to the experimental data. The applicability of mentioned models is critically tested on two types of composite systems: Ni film on Cu substrate, which is example for "hard film on soft substrate" and electrodeposited Ni on Si substrate ("soft film on hard substrate") and their reliability is given.

Fine-grained nickel thin films were electrodeposited from a self-made sulphamate-based electrolyte on different substrates: polycrystalline cold-rolled copper and single crystal silicon with two different orientations, namely (100) and (111). The influence of the substrate and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Four composite hardness models (Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky models) are chosen and applied to the experimental data. The applicability of mentioned models is critically tested on two types of composite systems: Ni film on Cu substrate, which is example for "hard film on soft substrate" and electrodeposited Ni on Si substrate ("soft film on hard substrate") and their reliability is given.

Fine-grained nickel thin films were electrodeposited from a self-made sulphamate-based electrolyte on different substrates: polycrystalline cold-rolled copper and single crystal silicon with two different orientations, namely (100) and (111). The influence of the substrate and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Four composite hardness models (Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky models) are chosen and applied to the experimental data. The applicability of mentioned models is critically tested on two types of composite systems: Ni film on Cu substrate, which is example for "hard film on soft substrate" and electrodeposited Ni on Si substrate ("soft film on hard substrate") and their reliability is given.

Fine-grained nickel thin films were electrodeposited from a self-made sulphamate-based electrolyte on different substrates: polycrystalline cold-rolled copper and single crystal silicon with two different orientations, namely (100) and (111). The influence of the substrate and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Four composite hardness models (Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky models) are chosen and applied to the experimental data. The applicability of mentioned models is critically tested on two types of composite systems: Ni film on Cu substrate, which is example for "hard film on soft substrate" and electrodeposited Ni on Si substrate ("soft film on hard substrate") and their reliability is given.

Crystals of Sc2AlB6 were grown using scandium oxide and elemental boron as starting materials in a self-component aluminum solution under an argon atmosphere. The growth conditions for obtaining single crystals of relatively large size were investigated. Sc2AlB6 single crystals were obtained in the form of prisms extending in the b-axis direction. The largest Sc2AlB6 crystals prepared had maximum dimensions of about 0.4×0.4×4.2 mm3. The values of the Vickers microhardness and the electrical resistivity of Sc2AlB6 crystals are 12.7±0.8 GPa and 43±8 cm, respectively. The oxidation of Sc2AlB6 crystals starts at about 773°C, and the weight gain after TG determination is 12.9 mass% at 1200°C. The oxidation products of Sc2AlB6 crystals could not determined.