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The implementation of the circular economy concept in industries demands experimental and innovative investigations. The set of strategies and paradigms that express the theoretical base of the circular economy plays a vital role in the enhancement of the quality and performance of polymer and composite materials. In this article, tungsten carbide material is advanced for tribological investigations. The scanning electron microscope and an optical and mechanical profilometer were used for the analysis of cotton polymer and tungsten carbide ball surfaces. A newly developed tribometry technique was introduced to investigate the coefficient of friction, wear, and deformation. The cotton surface was found damaged and rough. The tungsten carbide balls showed low roughness and higher hardness. The average surface roughness parameters Ra, Rz, and Rp of tungsten carbide balls were 0.10, 0.15, and 0.20, respectively. The average friction constant values were found to be 0.12–0.15 in the perpendicular direction and 0.11–0.17 in the parallel direction. Reciprocation distance increment has been used for industrial optimization. The coefficient of friction remained constant and slightly deformed cotton polymer. Based on the friction values, deformation, wear, and morphology evaluations, tungsten carbide ceramic materials could be used operationally for surface alterations of industrial machinery parts. The results could also enhance the quality and performance of polymer and composite products.

In this manuscript surface roughness, coefficient of friction (COF) and tensile properties of a post-consumer cotton fabric are evaluated. Fabric roughness, COF, effective tensile force and breaking force measured by optical profilometer, CETR tribometer and Instron tensile machine, respectively. The results proved that COF could rely on fabric pattern. Moreover, microscopically roughness influences on friction and tensile properties due to surface defects. It was found that increase in roughness of textile cotton relates to increase of number of random directional fibers. These fibers intensify friction and reduce tensile properties. The reduced values of tensile (140.49 N), breaking (123.23 N) and effective tensile force (251.43 N) of warp direction are greater than values of tensile (79.54 N), breaking (67.97 N) and effective tensile force (179.69 N) of weft direction. These effects can lower cutting performance of post-consumer textile.

The circular economy is still a hypothetical field in Europe. Different shredding and manufacturing machinery parts in textile industries are presumed to enhance product quality and performance. The quality and performance of recycled textile products play a vital role in the development of textile recycling technologies. The quality is principally associated with the mechanical and tribological properties of machinery parts. In this article, TiCN Coating is used to determine the coefficient of friction of post-consumer cotton fabric. The scanning electron microscope, optical and mechanical profilometer, and tribometer were used for surface and tribological evaluations. The TiCN coating was found smooth and homogeneous. The average coating surface roughness parameters Rmax, Rz, Rp were 0.24 µm, 0.21 µm, and 0.20 µm, respectively. The dynamic coefficient of friction values was found 0.38 to 0.30 in the warp and 0.33 to 0.28 in weft directions. The increase in sliding distance is used for industrial applications and evaluations. The increase in distance deformed and fractured cotton fabric surface. The coefficient of friction and deformation becomes constant after 40 m of sliding distance. Based on coefficient of friction values, permanent deformation, fracture, and morphologies evaluations TiCN coatings could be used operationally for surface modification of textile machinery parts. The surface modification of textile machinery parts with TiCN coating can enhance the quality and performance of textile products.

Rough, damaged, and distorted post-consumer natural and synthetic polymers cause wear and damage to textile machinery parts, presenting a major obstacle to the quality of recycled products. In this research, TiAlN coatings were used to measure the coefficient of friction (COF) for tribological properties. The scanning electron microscope (SEM) studies of cotton textiles revealed surface damage, distortions, and loose fibres produced on the fabric surface. SEM morphology of TiAlN coatings was found smooth and uniform. Additionally, Contour GT-K 3D optical microscope and mechanical profilometer (Mahr Perthometer) were used for coating surface analysis. The average coating surface roughness parameters were Rmax (0.30 µm), Rz (0.26 µm), and Rp (0.17 µm). The microhardness value was 35 GPa on the HV scale. The lower surface roughness and higher hardness values are an indication of reasonable quality and performance of textile fabrics during recycling. The dynamic COF values were obtained from 0.47 to 0.30 in warp and from 0.35 to 0.23 in weft directions. Higher COF values occurred in the warp direction due to lower thread densities, rough surface, preferred fibre orientation, randomly oriented fibres, and a plain-woven structure. Based on the COF values, permanent deformation, and morphology evaluations, TiAlN coatings could be used optimistically for surface modification of shredding, cutting, and textile machinery parts. The TiAlN coatings applications in industries could also enhance the quality and performance of recycled textile products.

Cotton, polyester, and polyethylene terephthalate are the most common types of polymers that produce huge wastes. The circularity of these post-consumer (PC) waste faces operational problems during processing. In this innovative research, the relationship between circularity, surface characterization, mechanical and tribological testing of fiber reinforced (cotton, polyester), and particulate (polyethylene terephthalate) composites is explored for industrial pilot production. Cutting model can control the size of fibers during grinding. The fiber reinforced composites (FRCs) with 10% (by weight) fiber loadings are found as operational candidates for structural, automotive, and medical applications due to suitable tensile strength (26–29 MPa), percentage of extension (10%) and abrasive wear (3 × 10−6 mm3/Nm). An increase in fiber content produces micro-defects like asperities, rough areas, voids, cracks, and pits in recycled composites. Therefore, the particulate and FRCs with 40% (by weight) fiber loadings become hard and brittle. However, these composites (especially with 40% wt. fiber loadings) exhibit reasonable elastic modulus (1526–2751 MPa) and abrasive wear (6.5 × 10−6 mm3/Nm). The ductile to brittle transition effect has appeared in all composites (with 30% wt. fiber content) due to continuous fiber addition, micro-defects creation and dual phase presence. In conclusion, natural and synthetic PC wastes can be utilized for sustainable processing of commercial polymer composites. Moreover, injection molding, polymer characterization, tensile testing, abrasion evaluation, and regression analysis can be introduced for the transformation of open-loop into closed-loop manufacturing.

Nanocrystalline diamond (NCD) films were grown on the High Pressure High Temperature (HPHT) (110) single crystal (SC) diamond substrates by Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD) in methane/hydrogen/nitrogen plasma. The thickness of the films was varied between 2.2 and 22.5 μm. The cauliflower-like surface morphology was observed by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The scaling behavior of NCD films growth was investigated. The relatively high value of the roughness exponent αs = 1.5–1.6 was found indicating anomalous scaling. Therefore, shadowing and diffusional instabilities can affect the film growth. The tribological properties of the NCD films deposited on the SC(110) diamond were compared with the NCD films prepared on the Si(100) substrates. Both types of specimens were tested under similar Hertzian contact pressure. The lower wear volume losses were observed on the NCD/SC(110) specimens. Therefore, the influence of substrate and substrate/film interface properties on the tribological behavior of the NCD films grown on Si(100) can be expected to cause NCD films deflection.

The study investigates thermal stability and high temperature tribological performance of a-C:H:Si diamond-like carbon (DLC) coating. A thin alumina layer was deposited on top of the a-C:H:Si coating to improve the tribological performance at high temperatures. The a-C:H:Si coating and alumina layer were prepared using plasma-activated chemical vapour deposition and atomic layer deposition, respectively. Raman and X-ray photoelectron spectroscopy were used to investigate the structures and chemical compositions of the specimens. The D and G Raman peaks due to sp2 bonding and the peaks corresponding to the trans-polyacetylene (t-Pa) and sp bonded chains were identified in the Raman spectra of the a-C:H:Si coating. Ball-on-disc sliding tests were carried out at room temperature and 400 °C using Si3N4 balls as counter bodies. The a-C:H:Si coating failed catastrophically in sliding tests at 400 °C, however, a repeatable and reproducible regime of sliding with a low coefficient of friction was observed for the Al2O3/a-C:H:Si coating at the same temperature. The presence of the alumina layer and high stress and temperature caused structural changes in the bulk a-C:H:Si and top layers located near the contact area, leading to the modification of the contact conditions, delivering of extra oxygen into the contact area, reduction of hydrogen effusion, and suppression of the atmospheric oxidation.

Comparative analysis of dry sliding wear behavior of nanocrystalline diamond (NCD) films and NCD films coated with a thin Al2O3 layer (Al2O3/NCD) is the main goal of the present study. Plasma-enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD) methods were used to prepare the NCD and alumina films, respectively. Sliding wear tests were conducted at room temperature (RT), 300 and 450 &deg, C in air. Independent of type of specimen, superlubricating behavior with the coefficient of friction (COF) in the range of 0.004‒0.04 was found for the tests at 300 &deg, C. However, the COF value measured on the Al2O3/NCD films in the tests at 450 &deg, C is lower than that for the NCD film. A relatively short run-in period and a stable COF value of about 0.15 were observed at this temperature for the Al2O3/NCD films. The width of the wear scars measured on the Al2O3/NCD films after the tests at 450 &deg, C is significantly smaller in comparison with the NCD film. The apparent wear volume of the wear scar on the NCD film tested at 450 &deg, C was noticeably higher than that on the Al2O3/NCD films.

The focus is on the oxidation resistance and tribological performance of ta-C and Al2O3/ta-C coatings. The wear tests were carried out on the ball on disc tribometer at room (25 °C) and high (400, 450 and 500 °C) temperatures in ambient air with Si3N4 balls as counterbodies. Scanning electron microscopy and Raman spectroscopy were used to analyze the surface morphology and chemical bonding, respectively. The Al2O3/ta-C coating exhibited better oxidation resistance and tribological performance at elevated temperatures than the ta-C coating. The Raman analysis revealed that a thin alumina layer suppresses structural changes in the ta-C coating at elevated temperatures, thus preserving the sp3 content.

The nanocrystalline diamond films were deposited by microwave plasma enhanced chemical vapour deposition (PE-CVD) on Si (100) substrate. Reciprocating sliding tests were conducted using Si3N4 balls as a counter body. A method based on the construction of the Abbott curve representing the areas of pristine and worn surface in the wear scars was applied for estimation of the wear rate. The calculated wear rates were compared with the results obtained by profilometric measurements and direct measurement of the wear scars cross sections by scanning electron microscopy (SEM).

The present study deals with the tribological behavior of nanocrystalline diamond (NCD) coatings at high temperature sliding conditions. The NCD coatings were grown by plasma enhanced chemical vapor deposition (PECVD) method on the hard metal (WC-Co) substrates. The friction and wear tests were performed on ball-on-disc tribometer using a high-temperature chamber with rotary drive. The tests were carried out at room temperature, 300, 450 and 600 °C. The scanning electron microscopy (SEM), optical microscopy, mechanical profilometry and Raman spectrometry were used for investigation of the morphology and chemical composition of the wear scars and pristine surface. The depth and width of the wear scars measured after the high temperature sliding tests are larger in comparison with room temperature tests. It was observed that the coefficient of friction (COF) increased with increasing temperature. The wear rate of NCD coatings tested at 300-450° C was about 10 times higher than that at room temperature. The mechanisms involved for these variations are discussed.

The paper investigates the variation of friction force (Fx) during reciprocating sliding tests on nanocrystalline diamond (NCD) films. The analysis of the friction behavior during the run-in period is the focus of the study. The NCD films were grown using microwave plasma-enhanced chemical vapor deposition (MW-PECVD) on single-crystalline diamond SCD(110) substrates. Reciprocating sliding tests were conducted under 500 and 2000 g of normal load using Si3N4 balls as a counter body. The friction force permanently varies during the test, namely Fx value can locally increase or decrease in each cycle of sliding. The distribution of friction force drops (dFx) was extracted from the experimental data using a specially developed program. The analysis revealed a power-law distribution f-&micro, of dFx for the early stage of the run-in with the exponent value (&micro, ) in the range from 0.6 to 2.9. In addition, the frequency power spectrum of Fx time series follows power-law distribution f-&alpha, with &alpha, value in the range of 1.0&ndash, 2.0, with the highest values (1.6&ndash, 2.0) for the initial stage of the run-in. No power-law distribution of dFx was found for the later stage of the run-in and the steady-state periods of sliding with the exception for periods where a relatively extended decrease of coefficient of friction (COF) was observed. The asperity interlocking leads to the stick-slip like sliding at the early stage of the run-in. This tribological behavior can be related to the self-organized criticality (SOC). The emergence of dissipative structures at the later stages of the run-in, namely the formation of ripples, carbonaceous tribolayer, etc., can be associated with the self-organization (SO).

TiCN and TiAlN gradient coatings were deposited on the AISI 316L stainless steel substrates by lateral rotating cathode arc (LARC) physical vapour deposition (PVD) technology. Corrosion and tribocorrosion behaviour was studied in 3.5 wt. % NaCl solution. The thickness of coatings was about 3 μm. For both coatings the corrosion potential shifted to more positive values as compared to the uncoated substrate. The corrosion current density decreased for TiCN and TiAlN coatings indicating up to 40 folds higher polarization resistance. The coefficient of friction value of TiCN coating is three times lower and durability is six times higher than that of TiAlN coating under the same tribocorrosion conditions.

The study deals with the calculation of the wear rate of nanocrystalline diamond (NCD) films. The NCD films were grown by microwave plasma enhanced chemical vapor deposition (MW-PECVD) on (100)-oriented Si wafers. Reciprocating sliding tests with different loads and test durations were conducted. The depth profiles of wear scars were analyzed by the mechanical (stylus) profilometer and the wear rate was evaluated. The NCD films were broken across the wear scars and the wear rate was estimated by the measurement of the area of wear scar using the scanning electron microscopy (SEM) cross-sectional image. A good agreement was found between two methods.

The study investigates the wear of microcrystalline diamond (MCD) and diamond-like carbon (DLC) coatings. The MCD and DLC coatings were grown by plasma enhanced chemical vapor deposition (PECVD) method on WC-Co substrates. The sliding wear tests were performed on the ball-on-plate type of tribometer in reciprocating mode. The ball-cratering wear tests were carried out using Calo tester. The mechanical profilometer, optical and scanning electron microscopes (SEM) were used for investigation of the surface morphology of the wear scars. The wear of DLC coating is more intense in comparison to the MCD coating. In contrast to the MCD coating, no evidence of the DLC coating deflection was found.

Circular economy is still a theoretical field. In this research, alumina ceramic material was used to measure the coefficient of friction (COF) of cotton fabric with the objective of supporting the circular economy of textile industries. A scanning electron microscope (SEM), optical profilometer, mechanical profilometer and tribometer were used for evaluations of the cotton fabric surface and the coefficient of friction (COF). The cotton fabric surface was detected rough and damaged while the ceramic balls displayed smoothness along with high microhardness. The dynamic COF values were 0.12 to 0.15 in warp and 0.11 to 0.17 in weft directions. Based on the COF values, deformation, wear and morphologies evaluations, alumina ceramic materials could be used operationally for surface alterations of textile machinery parts. The results could also enhance the quality and performance of textile products.

Mechanical and tribological properties of the hard-multilayer TiN-AlTiN/nACo-CrN/AlCrN-AlCrO-AlTiCrN coating deposited on WC-Co substrate were investigated. The sliding tests were carried out using ball-on-disc tribometer at room (25 &deg, C) and high temperatures (600 and 800 &deg, C) with Al2O3 balls as counterpart. Nano-scratch tests were performed at room temperature with a sphero-conical diamond indenter. The surface morphology and chemical composition were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and in-situ high-temperature X-ray diffraction (HT-XRD). The phase transition from fcc-(Al,Cr)2O3 into &alpha, (Al,Cr)2O3 was observed at about 800 &deg, C. The results of the tribological tests depends on the temperature, the lowest apparent and real wear volumes were observed on the coating after the test at 800 &deg, C along with the smallest coefficient of friction (COF). The plastic deformation of the coating was confirmed in sliding and nano-scratch tests. The nano-scratch tests revealed the dependence of COF value on the temperature of the sliding tests.

The study deals with tribological properties of diamond films that were tested under reciprocal sliding conditions against Si3N4 balls. Adhesive and abrasive wear are explained in terms of nonequilibrium thermodynamic model of friction and wear. Surface roughness alteration and film deformation induce instabilities in the tribological system, therefore self-organization can occur. Instabilities can lead to an increase of the real contact area between the ball and film, resulting in the seizure between the sliding counterparts (degenerative case of self-organization). However, the material cannot withstand the stress and collapses due to high friction forces, thus this regime of sliding corresponds to the adhesive wear. In contrast, a decrease of the real contact area leads to the decrease of the coefficient of friction (constructive self-organization). However, it results in a contact pressure increase on the top of asperities within the contact zone, followed by material collapse, i.e., abrasive wear. Mentioned wear mechanisms should be distinguished from the self-lubricating properties of diamond due to the formation of a carbonaceous layer.

The study investigates alterations in surface morphology of microcrystalline diamond (MCD) film under reciprocating sliding test conditions. The MCD film was grown by microwave plasma enhanced chemical vapor deposition (MW-PECVD) on (100)-oriented Si wafer. The surface morphology was characterized by optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and mechanical profilometry. The formation of ripples on the wear scar surfaces was observed. The normalized wear rate (mm3/mN) of diamond film was evaluated using different approaches in order to understand the influence of diamond film deflection to wear.

The study investigates wear performance of nanocrystalline diamond (NCD) films under reciprocating sliding conditions. The NCD films were grown by hot-filament chemical vapor deposition (HFCVD) method on (100) oriented Si wafers. The surface morphology was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and mechanical profilometry. The study focuses on the understanding of mechanisms resulting in NCD films deformation and formation of ripple patterns on the wear scars surface observed during reciprocal sliding tests. Plastic deformation of the Si wafer due to NCD film deposition and high local contact pressure and temperature during sliding lead to structural changes on the Si(100)/NCD film interface, thus causing the NCD film to deform and the characteristic ripple patterns to develop on the wear scars surface. DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7232

Nanocrystalline diamond (NCD) films were produced by microwave plasma enhanced chemical vapor deposition (MPCVD) in methane/hydrogen/air plasma. The thickness of the films was varied from 0.15 to 22 μm. X-ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM) were used to investigate the structure and surface morphology of the films. During a short initial period of the deposition, i.e. from 2.5 min to 60 min, the growth dynamics involve relatively strong non-local effects, followed by a growth stage, which is characterized by a contribution of non-local and non-linear effects to the growth dynamics. The later regime of growth with roughness exponent α ~ 0.35–0.4 and growth exponent β ~ 0.25 can be related with the Kardar–Parisi–Zhang (KPZ) scaling regime of growth. The morphological peculiarities observed on the NCD film surface after already 2.5 min of deposition influence the morphology of the films for prolonged deposition time. Therefore, control over the size and distribution of these peculiarities by systematic variation of the deposition parameters allows to optimize the surface morphology for specific applications. The mountain-like patterns observed on the NCD films surface can be related to conformal KPZ growth regime, in contrast to the cusp-like patterns caused by non-local effects and noise.

Nitrogen vacancy (NV) color centers in diamond form promising magnetic sensors due to stable photoluminescence (PL), optically readable spins and high coherence times even at ambient conditions. Either individual centers or ensembles of NV centers can be used; the first offering ultimate resolution down to the nanoscale [1]; the latter offering enhanced sensitivity and a gain in PL signal [2].

The formation of nanoscopic ripple patterns on top of material surfaces has been reported for different materials and processes, such as sliding against polymers, high-force scanning in atomic force microscopy (AFM), and surface treatment by ion beam sputtering. In this work, we show that such periodic ripples can also be obtained in prolonged reciprocating sliding against nanocrystalline diamond (NCD) films. NCD films with a thickness of 0.8 µm were grown on top of silicon wafer substrates by hot-filament chemical vapor deposition using a mixture of methane and hydrogen. The chemical structure, surface morphology, and surface wear were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and AFM. The tribological properties of the NCD films were evaluated by reciprocating sliding tests against Al2O3, Si3N4, and ZrO2 counter balls. Independent of the counter body material, clear ripple patterns with typical heights of about 30 nm induced during the sliding test are observed by means of AFM and SEM on the NCD wear scar surfaces. Although the underlying mechanisms of ripple formation are not yet fully understood, these surface corrugations could be attributed to the different wear phenomena, including a stress-induced micro-fracture and plastic deformation, a surface smoothening, and a surface rehybridization from diamond bonding to an sp2 configuration. The similarity between ripples observed in the present study and ripples reported after repeated AFM tip scanning indicates that ripple formation is a rather universal phenomenon occurring in moving tribological contacts of different materials.

This paper investigates the morphological modifications of the nanocrystalline diamond (NCD) film surface under reciprocating sliding test conditions. The surface morphology was characterized by atomic force microscopy (AFM). We observed longitudinal grooves and transverse ripples which were formed during the sliding tests on the NCD film surface. The primary goal of the study was to understand the influence of frequency, sliding distance and load variations on the formation of ripple patterns on the wear scars surface. The morphological alteration from continuous to broken ripple shapes was observed. Our study suggests that the geometrical shape of ripples is affected by the formation of the periodic array of grooves.

TiN coatings with different thickness were prepared by arc ion plating (AIP) physical vapor deposition (PVD) on high speed steel (HSS) substrates. TiN coatings surface roughness was investigated by atomic force microscopy (AFM) and 3D optical profilometry and growth kinetics was described using scaling exponents β and α. The growth exponent β is 0.91-1.0 and the roughness exponent α is 0.77-0.81. Due to relatively high value of the exponent α, the surface diffusion is likely predominant smoothening mechanism of TiN growth.

Main focus was on the deposition of carbon nanofibers (CNFs) onto the hard nanocomposite (nc-Ti1 − xAlxN)/(a-Si3N4) (nACo®) coating surface and the investigation of the structure and tribological properties of CNFs. The alcohol chemical vapor deposition (ACCVD) method was employed to prepare CNFs and the deposition temperatures were 600 and 700 °C, respectively. Prior to the CNF deposition, Ni catalyst was deposited onto the nACo® surface using the magnetron sputtering. The influence of the deposition temperature on the carbon nanofibers structure was investigated by Raman spectroscopy and scanning electron microscopy (SEM). The higher order degree of CNF structure is observed with increasing deposition temperature. Tribological tests were carried out under fretting contact conditions against Al2O3 ball. It is shown that the coefficient of friction (COF) decreases from 1.0 to 1.2 for the clean nACo® surface to 0.2–0.4 for the CNF layers deposited on the nACo® surface. The roughness of the nACo® surface was varied and a higher durability of the CNF layers deposited on the rougher nACo® surface is found.

Diamond-like carbon (DLC) films were prepared in-situ on top of hard coatings, namely, prior to the DLC deposition, CrN, TiCN and nanocomposite nACo (nc-AlTiN/(a-Si3N4) layers were deposited on WC-Co substrates. The Ra roughness of WC-Co substrates was 0.05 and 0.2 µm. Surface morphology of DLC coatings was investigated by means of profilometry and geometrical parameters Ra, Rsk, Rku and Rz were evaluated. Fretting tests were conducted with 3 mm in diameter alumina balls under 1 and 2 N load, at slip distance of 2 mm and frequency of 2 Hz. Statistical analysis shows significant correlation between Ra and Rz parameters corresponding to initial DLC surface and wear scar surfaces produced by fretting tests after 2400 and 4800 cycles, respectively. This finding indicates a relationship between friction (wear) and Ra and Rz parameters. Positive correlation between the coefficient of friction (COF) and kurtosis Rku indicates that surface flatness is an important factor for optimal friction of an alumina ball against DLC coating.

This study focuses on the influence of surface geometry of hard coatings on tribological behavior. TiN, TiAlN, AlTiN and nanocomposite (nc-Ti1−xAlxN)/(a-Si3N4) (nACo) coatings were deposited by means of the lateral rotating cathode arc method on high speed steel (HSS) substrates. Surface topology (area of 50 μm × 50 μm, 10 μm × 10 μm and 5 μm × 5 μm) investigations by the atomic force microscopy (AFM) revealed that for all types of coatings the non-Gaussian height distribution function (HDF) is mainly due to the macroparticles. Factors and mechanisms affecting the value of the coefficient of friction (COF) during the running-in period were discussed.

We investigate bright fluorescence of nitrogen (NV)- and silicon-vacancy color centers in pyramidal, single crystal diamond tips which are commercially available as atomic force microscope probes. We coherently manipulate NV electronic spin ensembles with $T_2 = 7.7(3)\,\mu$s. Color center lifetimes in different tip heights indicate effective refractive index effects and quenching. Using numerical simulations, we verify enhanced photon rates from emitters close to the pyramid apex; a situation promising for scanning probe sensing., Comment: 4 pages, 3 figures, for additional information, please see supplementary material uploaded as ancillary file Version 2 to appear (open acces) in Applied Physics Letters

The oxidation of CoAl(1 0 0) was investigated by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED), high resolution electron energy loss spectroscopy (HREELS), and scanning tunneling microscopy (STM). In the case of alumina grown after oxidation with 15,000 L at room temperature, the characteristic EEL spectrum, along with the sharp (2 × 1) LEED pattern observed after annealing at 1000 K, showed that a stable well-ordered θ alumina was formed. The intermediate phase was found after heat treatment at 1150 K. At higher temperatures, the formation of the α-like alumina was observed. The comparative study of as-oxidation versus subsequent annealing of amorphous alumina at high-temperatures revealed a close similarity between the structures of alumina.

In the present study, the elastic properties of Ti1?xAlxN (0 ? x ? 0.75) hard coatings were studied by ab initio calculations. The bulk (B), shear (G) and Young's (E) moduli and Poisson's ratio (?) were calculated for isotropic materials. In addition, the anisotropy of the elastic moduli (G12, G23, E11, E22) and the Poisson's ratios (?12, ?21, ?23) are described with respect to particular crystallographic planes. The results of the calculations enable us to relate the experimentally observed increase in hardness to an increasing Al content, at least within the range 0 ? x ? 0.5, to an increase in G and E and to a decrease in B. The calculated longitudinal Young's modulus E11(1?1?1) of Ti1?xAlxN (0 ? x ? 0.4) is in good agreement with experimental data taken from the coatings with the (1?0?0) preferred orientation.

We have investigated the growth of Co nanoparticles on {theta}-Al{sub 2}O{sub 3}/CoAl(1 0 0) by means of Auger electron spectroscopy (AES), high-resolution electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Due to Volmer--Weber growth, Co forms particles with a mean diameter of approximately 2.5 nm and height of 0.8 nm. Even on the entirely covered oxide, there is no Ostwald ripening and Co particles stay structurally isolated. The nanoparticles exhibit a small size distribution and tend to form chains, as predetermined by the streak structure of the oxide template. For sufficient high coverages Co-core-CoO-shell nanoparticles may be evidenced, which is explained as a result of surfactant oxygen. The nanostructured particles may open the door to numerous applications, such as in catalysis and magnetoelectronic applications, where large areas of ordered nanodots are desired.

Clean and oxidized surfaces of CoAl(1 0 0) were investigated by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), high resolution electron energy loss spectroscopy (HREELS), and scanning tunnelling microscopy (STM). The regrowth or step flow of terraces was observed at 1150 K. The correlation between the growth of oxide and the step flow on the CoAl(1 0 0) surface is discussed in this paper.

We have employed Auger electron spectroscopy (AES), high resolution electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to investigate the growth of an Al2O3 film on CoAl(1 0 0). While exposure to oxygen at room temperature leads to the formation of amorphous alumina, subsequent annealing at higher temperatures results in the growth of well-ordered θ-Al2O3. Well-ordered Al2O3 films are also formed by oxidation at temperatures of 800 K and above. The oxide is characterized by Fuchs–Kliewer modes at around 430, 630, 780 and 920 cm−1. Oxide islands grow in two sets of domains perpendicular to each other. Under ultra-high vacuum conditions, self-limiting thickness of the oxide layer (9–10 A) has been found. The band gap of the θ-Al2O3 film on CoAl(1 0 0) is 4.3–4.5 eV.

The oxidation of a CoAl(1 0 0) surface at 300 K was studied by means of Auger electron spectroscopy, high resolution electron energy loss spectroscopy (EELS), low energy electron diffraction and scanning tunneling microscopy (STM). For an exposure ⩽0.3 L, the oxygen atoms are chemisorbed on the CoAl(1 0 0) surface, while for a larger O2 exposure the oxidation of the surface sets in. For an exposure ⩾300 L the surface is entirely covered with amorphous Al2O3 (a-Al2O3) whereas the Co atoms seem to be unaffected. The EEL spectra of a-Al2O3 exhibit Fuchs–Kliewer modes at around 640 and 890 cm−1. The thickness of the a-Al2O3 film is estimated to be 7.1 ± 0.7 A. The STM images show that the oxide grows as large islands which cover the whole surface. The band gap of the ultra-thin a-Al2O3 film on CoAl(1 0 0) is found to be 3.2 eV and thus it is strongly diminished with respect to the bulk value.

The growth of Co on thin Al2O3 layers on Ni3Al(1 0 0) was investigated by Auger electron spectroscopy, high resolution electron energy loss spectroscopy (EELS), and scanning tunneling microscopy. At 300 K, Co grows in three-dimensional clusters on top of the Al2O3 layer. A defect structure of the alumina layer plays a crucial role during the early stage of Co growth. After deposition of 10 A of Co, a complete screening of the dipoles of the Al2O3 layer due to the Co film is found in the EELS measurements. Annealing the Co film reveals a process of coalescence of Co clusters and, above 700 K, diffusion of the Co atoms through the oxide film into the substrate takes place.

The oxidation of the Ni 3 Al(1 0 0) surface at 1100 K with 2000 l was investigated by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), high resolution electron energy loss spectroscopy (EELS), and scanning tunneling microscopy (STM). Oxidation at 1100 K, leads to the formation of a well ordered, ultra thin Al 2 O 3 film on top of Ni 3 Al(1 0 0). The oxide grows with the (1 1 1) plane of the γ′-Al 2 O 3 parallel to the surface plane of the substrate. The observed LEED pattern of the Al 2 O 3 film is explained by a hexagonal structure in two domains which are perpendicularly oriented with respect to each other. The lattice constant of the hexagonal structure amounts to ∼3 A. In addition, two hexagonal superstructures with a lattice constant of 17.5 and 54 A were found on the oxide surface.

A spherical cap grinder (kaloMax) was employed to evaluate the wear resistance of hard coatings. Simplicity is the attractive advantage of the test. A comparative study of TiN and AlTiN coatings was carried out to elucidate capabilities and limitations of the technique. The relatively high uncertainty of measurement suggests that the test can be used only for qualitative evaluation of wear.