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A remarkable number of scientific papers are available in the literature about the bulk amorphous alloys and metallic glasses. Today, DSC is an essential tool for amorphous alloys research and development, and of course for quality assurance. In many cases, users seek to examine the determination of only one or two properties, although much more information can be obtained from the measurements. The research involved structural relaxation, Curie temperature, glass temperature, crystallization, phase separation, nanocrystalline volume fraction, melting point and liquidus temperature determination subjects and kinetics of microstructural transformations induced by thermal treatment. We collected and present the information that can be obtained with this technique and draws the reader’s attention to some potential problems related to data interpretation.

Graphite, one of the polymorphic forms of carbon, has become a versatile industrial material of nowadays due to its particular attributes. It is used mainly in the automobile industry, metal extractive industry and in the high-tech industry. Moreover, it is also included in the list of critical raw materials for the EU. Our aim was to prove the presence of graphite by thermal analysis beyond X-ray powder diffraction (XRD) and Raman spectroscopy. Thermogravimetry yields comparable results with quantitative XRD. The formation conditions are described by Raman spectrometry and microscopy examinations of drill core samples from Szendrőlád (Szendrő Mts, NE-Hungary; (Szendrőlád Limestone Formation, middle-late Devonian, shelf-basin facies). Polished rock slabs were made for optical microscopy, scanning electron microscopy with energy dispersive spectrometry (SEM–EDS) and Raman spectroscopy. X-ray powder diffraction (XRD) and thermal analysis (DTA-TG) measurements were made on powders. Based on our results, the graphite is epigenetic; its quantity varies between 1.5–3 mass% in the samples. It was developed in 20–50 μm sized flakes, which are often arranged in > 300 μm sized aggregates. Graphite was formed during regional metamorphism from the organic matter-rich shales. The average formation temperature, calculated from the results of Raman spectroscopy, is around 410 °C (± 30 °C). The Raman measurements also indicated the presence of a partially graphitized (disordered graphite) material beside graphite.

Tanulmányunk célja a Szendrői-hegységben található Meszes település melletti Vasbánya-hegy felszíni feltárásaiból (Szendrői Fillit Formáció) gyűjtött fekete fillitek vizsgálata optikai és elektronmikroszkópiával, illetve röntgen-pordiffrakcióval a kőzetekben található grafitra és kritikus elemekre fókuszálva. Vizsgálataink alapján a grafit pikkelyes formában, 50-150 µm-es nagyságban volt észlelhető. A kritikus elemeket tekintve, a minták tartalmaztak titánt (főként TiO2-ként, ritkán ilmenitként, valamint fengitbe beépülve), nióbiumot (TiO2-ba beépülve), stronciumot (fluorapatitban és monacitban), valamint ritkaföldfémeket (xenotimban, monacitban és goethitben).

Cu/AlN–Al2O3 nano-multilayer (NML) was deposited by magnetron sputtering method on 42CrMo4 steel samples, starting with a 15 nm AlN–Al2O3 layer and followed by 200 alternating layers of 5 nm thick Cu and 5 nm thick AlN–Al2O3 layers. The microstructure and thermal behaviour of the as-deposited and heat-treated multilayer was studied. Starting from about 400 °C, extensive coarsening of Cu nanocrystallites and the migration of Cu within the multilayer were observed via solid-state diffusion. Part of the initial Cu even formed micron-sized reservoirs within the NML. Due to increased temperature and to the different heat expansion coefficients of Cu and the AlN–Al2O3, the latter cracked and Cu appeared on the top surface of the NML at around 250 °C. Below 900 °C, the transport of Cu to the top surface of the NML probably took place as a solid-state flow, leading to faceted copper micro-crystals. However, above 900 °C, the Cu micro-crystals found on the top of the NML have rounded shape, so they were probably formed by pre-melting of nano-layered Cu due to its high specific surface area in the NML. Even if the Cu crystals appear on the top surface of the NML via solid-state flow without pre-melting, the Cu crystals on the top surface of the NML can be potentially used in joining applications at and above 250 °C.

Carbon nanosheets (CNs) were successfully synthesized from nettle stem (NS) which is an inexpensive material with a high carbon content that is abundantly available in nature. CNs were produced using chemical (potassium hydroxide activation and acid exfoliation) and thermal treatments. Sulfuric (H2SO4), phosphoric (H3PO4) and nitric (HNO3) acid solutions were used for exfoliation. CNs exfoliated by H3PO4 have higher specific surface area (789 m2 g−1) compared to CNs exfoliated by H2SO4 (705 m2 g−1) and HNO3 (106 m2 g−1). In this work, NSCNs were found to be a potential candidate for electrode material in electrochemical capacitors. The maximum specific capacitance of the NSCNs exfoliated by H3PO4 is found to be 27.3 F g−1 at a current density of 0.05 A g−1, while the specific capacitance of NSCNs exfoliated by H2SO4 and HNO3 is 9.34 F g−1 and 1.71 F g−1, respectively. Energy density (0.06–0.95 Wh kg−1) and power density (20.9–26.7 W kg−1) of NSCNs are confirmed to be supercapacitor materials and can be applied in energy storage devices.

Abstract One of the main challenges in the field of heterogeneous catalysis is the involvement of thin solid films and membranes and their application in flow systems. In this regard, we report here the application of self-supported bacterial cellulose (BC) reinforced nanosized platinum (Pt)/N-doped bamboo-like carbon nanotube (NBCNT) hybrid catalyst membrane with a thickness of 35 ± 5 µm in the hydrogenation of n-butene. To synthetized the BC-NBCNT/Pt nanohybrid membrane catalyst a simple impregnation route was applied in a two-step process. As-prepared material was tested in a continuous flow system and the conversion was followed directly by using Fourier transform infrared spectroscopy. Furthermore, the fabricated films were characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and specific surface area measurement (Brunauer–Emmett–Teller). Hydrogenation performance was studied on both single and double films. Results revealed that 97% conversion of n-butene can be achieved using these bacterial cellulose reinforced hybrid membranes. Graphic abstract

Numerous slag samples and a piece of iron bloom with slag from excavations of Celtic settlements (La Tene C and D) at Ordacsehi, Szilvasvarad and Jaszbereny (Hungary) were examined. The main object...

This paper communicates new results on fire aided limnosilicte mining in a Hungarian paleolithic site. The beneficial effect of temperature on material fragmentation and chipping was proved by labo...

The SiO2 varieties of low temperature other than quartz play an important role in the composition of many archeological tools, products, byproducts, and raw materials. We have encountered several S...

By applying ultrasonic cavitation, palladium particles were deposited onto the surface of two different types of carbon nanotubes (nitrogen-doped bamboo-shaped carbon nanotubes, N-BCNT and multiwalled carbon nanotubes, MWCNT). To achieve this, palladium ions have been reduced by the adsorbent (N-BCNT or MWCNT) itself. Hydroxyl functional groups were identified on the surface of the MWCNTs, while amine groups have been found on the N-BCNTs. The Zeta potential was lower (−9.8 mv) in the case of the N-BCNT sample, than for MWCNT (−6.1 mV), which was in accordance with their different dispersibility in aqueous phase. The incorporated nitrogen atoms and their oxidized forms within the N-BCNT structure lead to increased adsorption capacity and thus, this type of nanotube is more efficient adsorbent for Pd particles, than MWCNT. The higher adsorption capacity of the N-BCNTs can be explained by the presence of nitrogen atoms which increase the interaction between the Pd and nanotubes. Both Pd/nanotube systems show high catalytic activity (after 30 min – 99% aniline yield) in hydrogenation of nitrobenzene to aniline. Thus, palladium coated carbon nanotubes were synthetized in a one-step reduction procedure, and the produced composites are applicable as catalysts in heterogeneous hydrogenation reactions.

This article is focused on the development of geopolymer–glass foam composite, produced by encapsulation of glass waste based lightweight aggregate in geopolymer matrix. The aim of the investigatio...

Maghemite particles were synthesized by using a combined combustion method and sonochemical step. Maghemite was used as carrier to prepare supported Pt and Pd catalysts after deposition via a sonochemical step. The catalysts were immediately ready to be used (metals were catalytically active) for the 2,4-dinitrotoluene hydrogenation to produce 2,4-toluenediamine. The most active catalysts were the Pd/maghemite and bimetallic Pd-Pt/maghemite. The catalysts were easily separable after reaction due to their magnetic properties.

Cellulose grains were carbonized and applied as catalyst supports for nickel- and magnetite-promoted bimetallic palladium- and platinum-containing catalysts. The bimetallic spherical aggregates of Pd and Pt particles were created to enhance the synergistic effect among the precious metals during catalytic processes. As a first step, the cellulose bead-based supports were impregnated by nitrate salts of nickel and iron and carbonized at 973 K. After this step, the nickel was in an elemental state, while the iron was in a magnetite form in the corresponding supports. Then, Pd and Pt particles were deposited onto the supports and the catalyst surface, precious metal nanoparticles (10–20 nm) were clustered inside spherical aggregated particles 500–600 nm in size. The final bimetallic catalysts (i.e., Pd–Pt/CCB, Pd–Pt/Ni–CCB, and Pd–Pt/Fe3O4–CCB) were tested in hydrogenation of chlorate ions in the aqueous phase. For the nickel-promoted Pd–Pt catalyst, a &gt, 99% chlorate conversion was reached after 45 min at 80 °C. In contrast, the magnetite-promoted sample reached an 84.6% chlorate conversion after 3 h. Reuse tests were also carried out with the catalysts, and in the case of Pd–Pt/Ni–CCB after five cycles, the catalytic activity only decreased by ~7% which proves the stability of the system.

“Support on support” (SoS) core-shell nanostructure was prepared by using zeolite beads as supports for nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs). The N-BCNTs were synthetized with cata...

Nitrogen-free multi-wall carbon nanotubes (MWCNTs) and N-doped bamboo-like carbon nanotubes (BCNTs) were synthesized by using catalytic vapor deposition (CVD) and used as catalyst support materials. Pd, Rh, Ru, and Ir have been deposited onto the nanotubes to achieve metal/nanotube catalysts. The catalytic activity of the samples was fine-tuned by changing the type of support. BCNT supported Pd and Rh (Pd/BCNT, Rh/MWCNT) catalysts were found to be the most active for liquid phase hydrogenation of octadecene amongst these samples. The initial olefin hydrogenation rate of the Pd/BCNT sample was slightly higher than the corresponding MWCNT-supported catalyst. Based on the hydrogenation reaction, the performance of these catalyst had been ranked as follows: Pd/BCNT ≈ Rh/MWCNT > Pd/MWCNT > Rh/BCNT > > Ir/MWCNT > Ru/BCNT > Ir/BCNT > Ru/MWCNT. The structural properties of chemisorbed Pd on MWCNT and N- BCNT were also characterized by means of computational chemical methods in order to shed some light on the nature of metal binding properties of N-doped and undoped surfaces. The calculations shown preference towards the edges of the surfaces which is in good agreement with the experimental findings.

Nitrogen-doped bamboo-like carbon nanotube (N-BCNT) coating was synthesized onto the surface of zeolite beads by using Catalytic Chemical Vapour Deposition (CCVD) method to develop a “support on support” (SoS) system. These complex structured materials were used as supports during the preparation of hydrogenation catalysts. Rhodium, palladium and platinum nanoparticles were deposited homogeneously onto the surface of the N-BCNTs of the SoS (final metal content 2 wt%). The catalytic activity of these samples was compared in the hydrogenation of nitrobenzene. The Pt/N-BCNT-zeolite sample was the most active (182 mol nitrobenzene after 30 min). The activity of the other two catalysts at 20 bar was well below this value, 99.5 mol after 60 min and 96 mol after 120 min for Pd and Rh, respectively. The aniline selectivity was different for the three catalysts and they facilitate the formation of various by-products (e.g. N-methylaniline, cyclohexylamine). The usage of the Pd and Pt/N-BCNT-zeolite catalysts are more convenient, as only one main by-product was formed. It was confirmed that the zeolite supported N-BCNTs are efficient catalyst supports in hydrogenation processes. Furthermore, by using this special SoS structure to support the catalytic metals the applicability is widened and the catalyst removal is easier.

We study the weak solvability of a general m −dimensional (m = 2, 3) mechanical model describing the contact between a piezoelectric body and a conductive foundation. The piezoelectric effect is characterized by the coupling between the mechanical and the electrical properties of the materials. This coupling leads to the appearance of electric potential when mechanical stress is present and conversely, mechanical stress is generated when electric potential is applied.

The aim of this study was to investigate the construction and demolition waste (CDW) fine size fraction by increasing its reactivity with mechanical activation (MA) in a stirred media mill. Systema...

Poly(ethylene terephthalate) (PET) materials with different molecular weights were isothermally crystallized from melt by systematically varying the temperature and duration of the treatment performed in the differential scanning calorimeter (DSC). Multiple endotherm peaks were observed on the subsequent heating thermograms that were separated from each other on the basis of their melting temperature versus crystallization temperature and melting temperature versus crystallinity function. By this new approach five sub-peak sets were identified and then comprehensively characterised. Wide-Angle X-Ray Diffraction (WAXD) analyses revealed that the identified sub-peak sets do not differ in crystalline forms. By analysing the crystallinity and the melting temperature of the sub-peak sets as a function of crystallization time, crystallization temperature and intrinsic viscosity, it was concluded that below the crystallization temperature of 460 K the sub-peak sets that were formed during primary or secondary crystallization transform partially or completely to a third sub-peak set during the heating run of the measurement, while above this temperature, the sub-peak set formed during primary crystallization gradually transforms to a more stable structure, with higher melting temperature. These formations and transformations are described with mathematically defined parameters as well.

In the current research, the effect of mechanical alloying (MA) of iron-coated NbC and Si on the material?s fineness and crystal structure was investigated. The MA experiments were carried out in a batch-type laboratory scale stirred media mill for various residence times up to 240 min in isopropanol. During MA, milling energy was measured, and stress energy (SE) was calculated. Morphology and material structural changes, during the mechanical alloying process, were determined by means of scanning electron microscopy (SEM) and powder X-ray diffraction (XRD), respectively. The particle size distribution of the product was measured by a Horiba 950 LA laser particle size analyser. Evolution of phases during highenergy milling of NbC, Al-Fe-carbide, Fe, and Si was studied as a function of specific milling energy. Transformations in the crystal structure were revealed, namely the generation of cementite and Nb-Si-carbide, which was proved by XRD results and thermodynamic calculations. As result of the experiments, optimum MA conditions were determined. The application of the mechanical alloying method gives the opportunity to produce nanocrystalline phase from the initial ironcoated NbC and Si powder

The kinetics of transformation of 5 w% TiB2 nano-particles (50 nm diameter) dispersed and pressed (1.5 GPa) in the of Ti matrix (150 µm diameter) into TiB nano-whiskers was studied as a function of temperature (800–900–1000 °C) and time (5–720 min) in 25 experiments in total, by vacuum sintering. The classical one-step Avrami kinetics does not properly describe this transformation due to the formation of oxide inhibitors from contaminants. However, the same results could be perfectly described by a complex Avrami kinetics supposing two parallel steps of transformations: i). fast transformation along the initially metallic Ti/TiB2 interface and ii). delayed transformation along contaminated Ti/TiB2 interface. Data for kinetic calculation was obtained by X-ray diffraction and Rietveld refinement on the sintered samples. Extrapolating the experimental results by the complex Avrami model beyond the measured temperature interval it was found that at and above about 1050 °C, the second step is missing due to the fast dissolution of oxide films in the beta-Ti matrix, leading to very fast kinetics.

A catalyst nanocomposite was synthesized based on zeolite supported nitrogen-doped carbon nanotubes (N-CNT) decorated with palladium nanoparticles. Zeolite beads impregnated with nickel nitrate solution were used as CCVD catalyst support during the synthesis of N-CNT. Then the zeolite supported N-CNT was decorated with palladium nanoparticles and the final nanocomposite was tested in nitrobenzene hydrogenation. The structure of the nanocomposite was characterized by SEM. The surface of the zeolite beads is extensively covered by N-CNT. The particle size distribution of the palladium nanoparticles on the surface of N-CNT is relatively homogenous (

Nitrogen‐doped, bamboo‐like carbon nanotubes (BCNTs) were synthesized from butylamine by catalytic chemical vapor deposition (CCVD method). The nanotubes were oxidized by H2SO4/HNO3 treatment and used to prepare calcium alginate gelled BCNT spheres. These beads were first carbonized and then Pd, Rh and Ni nanoparticles were anchored on the surface of the spheres. These systems were then applied as catalysts in CO2 hydrogenation. The BCNT support was examined by Raman spectroscopy, dynamic light scattering (DLS) and X‐ray photoelectron spectroscopy (XPS). The prepared catalysts were characterized by HRTEM and SEM. The oxidation pretreatment of BCNTs was successful, with the electrokinetic potential of the water‐based dispersion of BCNTs measuring −59.9 mV, meaning the nanotube dispersion is stable. Pyridinic and graphitic types of incorporated nitrogen centers were identified in the structure of the nanotubes, according to the XPS measurements. The Pd‐containing BCNT sphere catalyst was the most efficient in the catalytic studies. The highest conversion was reached on the Pd catalyst at 723 K, as well as at 873 K. The difference in the formation rate of CO was much less at 873 K between the Pd and Rh compared to the 723 K values. Accordingly, the application of Pd‐containing BCNT/carbon‐supported catalyst favored the generation of CO. However, the Ni‐BCNT/carbon catalyst leads to the formation of CH4 as the major product.

A Hungarian natural zeolite was mechanically activated by grinding in a Netzsch MiniCer stirred media mill for various activation times from 0 to 480 min. The research goal was to produce submicron-size activated zeolite with narrow particle size distribution and to investigate the energetic aspects of grinding and material characteristics. During mechanical activation (MA) the grinding energy was measured and stress energy was calculated. Additionally, the particle size distribution of the product was characterized by a Horiba 950 LA laser particle size analyzer (LPSA). Furthermore, the BET specific surface area and adsorption capacity of the MA zeolite were measured using TriStar 3000 apparatus and methylene blue adsorption test, respectively. The structural characterization of mechanically activated zeolite was carried out using Rietveld refinement on X-ray powder diffractometry data, Fourier transform infrared spectroscopy and transmission electron microscopy (TEM-EDS). TEM images and LPSA data of MA zeolite revealed the presence of particles below 100 nm. Significant amorphization, as well as the decrease in clinoptilolite phase, was found during entire MA process, while methylene blue adsorption was maintained. Finally, the relationship between grinding operating parameter (specific grinding energy) and material characteristics (amorphous content, the crystallite size of quartz and clinoptilolite) was created.

In the present article a 45Mo-45Cu-10Al2O3 (wt%) nano-composite was produced by mechanical alloying, shaped by cold pressing then by hot pressing at 950 °C. Our aim was to investigate the effect of different ball to powder ratio (BPR) on the particle size and shape, as well as on the material composition. Investigations were done with XRD, SEM and for hot pressed specimens Brinell hardness measurement. Lower BPR resulted in nano-sized crystallites in the powder, a homogenous phase distribution and higher BPR resulted in even smaller crystallite sizes, but with ZrO2 contamination from the milling equipment. The milling resulted in two separate fractions in the metallic phases separated by crystallite size, strain and lattice parameter. After hot pressing, the lower BPR powders developed a homogeneous, evenly distributed microstructure. Cu recrystallized during hot pressing, but still remained nanocrystalline, the crystallite size of Mo and α-Al2O3 decreased even more due to crystallite deformation and in the case of Mo, the lattice strain values indicates that recovery had also happened. The heating eliminated the crystal defects at highly strained areas and the subsequent cooling evened out the stresses in the respective metallic phases. The inner grain structure was revealed by etching, showing that α-Al2O3 particles congregated only at the Mo grain boundaries, but penetrated the Cu grains. The lattice strain values combined with the BSE images reveal that the Cu is the main matrix of the α-Al2O3 particles. The results indicate that the α-Al2O3 particles induced Particle Stimulated Nucleation (PSN) in the Cu explaining its moderate crystallite size increase. The hot pressed samples of higher BPR had higher ceramic (ZrO2 and α-Al2O3) content, resulting in higher hardness, but lower relative density (92.4%), compared to the samples of lower BPR, which reached 97.2% relative density and hardness still significantly higher than Mo Cu alloys.

Novel ultrafine grain composites of Cu matrix reinforced with 2-50 wt. % of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 (at. %) amorphous-nanocrystalline alloy particles have been fabricated by powder metallurgy. The composites showed a homogeneous structure. The characterization of composites was performed by optical and scanning electron microscopy (SEM), X-ray powder diffraction (XRD), micro- and macrohardness, as well as density measurements. After hot-pressing the crystallite size of Cu was smaller than 200 nm and nanocrystalline phases of reinforcing powder were 5-35 nm. Densities of 97-76 % relative to calculated values of consolidated composites were obtained, depending on the reinforcing weight fraction. Additionally, the mechanical properties and electrical resistivity of composites have been investigated. The results reveal that the 0.2% offset compressive yield strength of composites increases by two and five times, with respect to pure Cu matrix, for the composites reinforced with 2 and 50 wt. % of reinforcing particles, respectively. Electrical resistivity increases continuously, with higher values after 30 wt. % of addition. Changes in mechanical and electrical properties were produced by the increase of amorphous-nanocrystalline additive.

Zeolites are crystalline microporous alumosilicates whose unique pore and channel systems are the reason for their important role in catalysis, separation, and ion exchange. This work focuses on th...

In this paper, the effect of ball milling on Ti-based amorphous powders with nominal compositions of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 (at.%) was studied. For this purpose, Ni and Zr containing crystalline master alloys were ball-milled for 20 h in total. According to XRD analysis, the maximal amorphous fraction has been achieved in the case of Ni containing powder after 5 h of milling. The nanocrystalline phase of CuTi3(Ni) having a grain size of 0.17–0.29 nm formed in the early stages of the milling process and remained stable until the end of milling. The amorphous-nanocrystalline transition of this phase is a reversible process. The amorphization process of Ti48Cu39.5Zr10Co2.5 is not so rapid than that in the Ni containing alloy system. This confirms that kinetic energy of the milling process is insufficient for destabilization of the Cu2ZrTi2 nanocrystalline (0.15–0.26 nm) phase. The microhardness of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 particles was found to be HV0.01 519 ± 40 and 630 ± 55, respectively. For both compositions amorphous-nanocrystalline composites have been successfully obtained.

Fly ash, mechanically activated up to 120 min, has been used to synthesize geopolymers at ambient temperature. Fourier transform infrared spectroscopy (FTIR), quantitative X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM-EDS) have been used for the structural characterization. The decrease in characteristic particle diameter up to 60 min and then increase is related to particle breakage and aggregation/agglomeration respectively. The manifestation of mechanical activation (MA) during geopolymerisation resulted in enhanced dissolution and precipitation of Si and Al. The appearance of a new FTIR band in 1080–1096 cm−1 region in MA geopolymers is attributed to SiQn (n = 3–4) structural units of quartz. The increment in amorphization in MA fly ash resulted in an increase in crystallinity of geopolymers. The shift in characteristic XRD amorphous hump towards lower d(A) value in geopolymers is associated with incorporation of OH− and Na resulting in structural changes in amorphous phase. TEM-EDS revealed that geopolymers from as received fly ash exhibited predominance of primary structures such as nano-crystalline mullite, microcrystalline quartz and alumino-silicate glass. Whereas geopolymers from MA fly ash has shown secondary features mainly N-A-S-H gel, whose nano-porosity increased due to changes in gel characteristic. Finally, a conceptual mechanism of reaction is presented.

The aim of this study was to evaluate new Zr-based bulk metallic composites with crystallized dendrites or droplets which have the volume fraction below the critical one (the percolation limit). The Cu 36 Zr 48 Al 8 Ag 8 alloy was chosen as matrix. Dendrites formed by in-situ solidification due to Ni addition. It was found that a new monotectic alloy system can be created successfully owing to Y addition (1–7 at.%) to the matrix. Small amount of dendrites with non-random distribution has a strong influence on the compressive strength. Experiment showed that the alloy with 4.1 at.% Ni has the maximum compressive strength (1998 MPa) and Young's modulus (86 GPa) within the examined samples. The results of compression test reveal that the cracks propagate near the small droplets below 1 μm in diameter which generate weakening in the microstructure. In contrast, the large droplets especially above 3 μm in diameter create a strong barrier for the shear band propagation.

The formation of alpha-cristobalite and its effect on the elastic modulus (E modulus) was investigated in sewage pipe (SP) and tile bodies derived from Westerwald ball day (WBC), employing the results of previous research on WBC as a baseline. In this study, the SP and tile bodies derived from WBC are compared with the bodies derived from two residual Turkish kaolin and one Turkish ball clay, resulting in four sources of alpha-cristobalite formation: tile, SP, residual kaolin and ball clay. The crystallization of alpha-cristobalite in the fired WBC results from two primary pathways. The first pathway occurs as a devitrification product from the glass phase saturated with excess silica, which is typically present in ball clay after a >= 1100 degrees C; the second pathway results from a minor amount of transformation of peripheries of quartz crystals, firing at over a >= 1200 degrees. In addition to these two sources, other a-cristobalite sources for sewage-pipe bodies include smectitic clay and chamotte (prefired clay) addition. Conversely, no alpha-cristobalite occurred in tile mixture bodies containing approximate to 2 wt% potassium oxide (K2O). The alpha-cristobalite phase only forms in kaolinite-rich ball clay when K2O content is less than approximate to 2 wt% because devitrification of excess silica phase of tile bodies is primarily governed by K2O content. The 2 wt% K2O ratio inhibited a-cristobalite formation in tile bodies, while the same percentage or greater of K2O content in SP bodies did not inhibit the alpha-cristobalite formation due to the presence of chamotte and smectitic clay in the SP mixture. The measured minimum E moduli were attributed to cristobalite formations because of chamotte and smectitic clay additions to SP bodies. In the bodies derived from Turkish residual kaolin at over 1000 degrees C, the opaline and chalcedonic silica phase are transformed to a-cristobalite at a lower temperature than those observed for rock crystal quartz and Si-rich glassy phase in WBC bodies. Thus, determining the different alpha-cristobalite sources in clay-based ceramic bodies derived from either the ball clay, the residual kaolin or the bodies containing smectitic clay together with chamotte provides the essential pre-condition for the optimum admixing ratio in industrial SP and tile bodies.

Carbon black (CB) supported palladium-platinum catalysts were prepared with and without nickel(II) oxide or iron(III) oxide promoter materials. By applying ultrasonic cavitation highly efficient CB supported catalysts were created. The designed catalyst preparation is a one-step procedure, as post-treatments (e.g. calcination, hydrogen activation) are not necessary. The activation of the catalysts occurs during their preparation due to the ultrasonic cavitation. Thus, a fast and simple catalyst preparation procedure have been developed. The activity of the catalysts was compared in nitrobenzene hydrogenation at different temperatures in the range of 283-323 K at 20 bar hydrogen pressure. In terms of selectivity and aniline yield, no significant differences were detected even when promoters were present. By using the NiO promoter, the activation energy was extremely low (7.6 ± 0.7 kJ mol-1). The selectivity was over 99% in every case, and 99.6% aniline yield was achieved without any promoters (99.7% with NiO), while less than 1.0% by-products were formed. The reaction rate was high with every catalyst, and no significant differences were detected. All in all, the prepared catalysts show excellent catalytic activity in the hydrogenation of nitrobenzene.

The volume fraction of austenite (γ), ε martensite and α′ martensite is of key importance in the research of TWIP/TRIP steels. When mechanical loading is involved, the crystallographic texture also develops, which complicates X-ray diffraction-based phase ratio determination. The problem is more pronounced when only a couple, or only one Bragg-reflection can be measured. A solution for such cases is to determine the ratio of the phases based on the pole distribution function of a selected Bragg-reflection of the present phases. In this manuscript, this method is reconsidered for and applied to non-transmittable bulk specimens for the first time in the reflection mode of XRD pole figure measurements. First, the method was applied to a series of γ–α′ powder mixtures. The results were compared to those obtained by the Rietveld method. Afterwards, the technique was applied to strongly textured, bulk TWIP/TRIP steel specimens which were tensile tested at different temperatures. It was shown that the results of the presented method were close to those of the Rietveld technique in the case of powder mixtures. The results of the tensile-tested steels revealed that the α′ content increases with decreasing test temperatures, and the variation of the α′ ratio correlates very well with the ultimate tensile strength versus the temperature, confirming the contribution of the α′ content to the strength of TWIP/TRIP steels.

Cobalt, copper, and nickel ferrite spinel nanoparticles have been synthesized by using a combination of sonochemical treatment and combustion. The magnetic nanoparticles have been used as supports to prepare ~4 wt% palladium catalysts. The ferrites were dispersed in an ethanolic solution of Pd(II) nitrate by ultrasonication. The palladium ions were reduced to metallic Pd nanoparticles, which were then attached to the surface of the different metal oxide supports. Thus, three different catalysts (Pd/CoFe2O4, Pd/CuFe2O4, Pd/NiFe2O4) were made and tested in the hydrogenation of 2,4-dinitrotoluene (DNT). A possible reaction mechanism, including the detected species, has been envisaged based on the results. The highest 2,4-diaminotoluene (TDA) yield (99 n/n%) has been achieved by using the Pd/NiFe2O4 catalyst. Furthermore, the TDA yield was also reasonable (84.2 n/n%) when the Pd/CoFe2O4 catalyst was used. In this case, complete and easy recovery of the catalyst from the reaction medium is ensured, as the ferrite support is fully magnetic. Thus, the catalyst is very well suited for applicationy in the hydrogenation of DNT or other aromatic nitro compounds.

W and Cu can be found in separate phases in the W-Cu composites since these elements do not dissolve in each other neither in liquid nor in solid phase, but with mechanical alloying it is possible to produce nonequilibrium W-Cu alloys In this work the nanostructured W-Cu composites were produced by planetary ball milling. The nanostructured W-Cu powder was sintered on 900 °C and 950 °C with 50 MPa pressure applied. The meso- and microstructure of the W-Cu powder and the sintered samples, were investigated with SEM, TEM and XRD. After 50 h of milling, the size of the W crystallites was ~10 nm, and about 10% of the Cu was solved in the W matrix, producing a W-Cu nonequilibrium alloy layer on the surface of W nano crystallites. During sintering, the Cu atoms left from the W surface to the Cu phases, so the W-Cu nonequilibrium alloy layer disappeared. The size of the W crystallites – after 60 min of sintering on 950 °C - was around 170 nm, and the relative density was ~90% of the theoretical density.

In this work, silver (Ag) was reduced in nano-size on the surface on titanium (Ti) powder by chemical reduction method, which is a new, efficient and reproducible method. The amount of the Ag nanoparticles was at least 1.9 at. % in the Ti-Ag implant material and the typical size of these nanoparticles was under 50 nm. Owing to the powder metallurgy methods porous structure can be created and the relative density of the cold-pressed and sintered samples was 81 ± 1%. The mechanical properties were as follows: HV0.01 (363 ± 78), ultimate compressive true stress (470 ± 4 MPa) and Yield strength (277 ± 12 MPa). After the sintering process, TiAg and Ti2Ag phases were formed owing to the diffusion. The antibacterial features of Ag coated Ti powder, the sintered Ti-Ag alloy and its etched form were investigated. The strong antibacterial property was observed in the case of Ag coated Ti powder. It also turned out that E. coli bacteria in close contact of these Ti-Ag alloy surfaces cannot survive and the observed antibacterial properties may not be associated with the release of water soluble component from the alloy. Due to this local antibacterial feature of Ti-Ag alloys, they can be a good candidate for antibacterial implant material with potential biocompatibility.

The phase analysis based on the X-ray diffraction method is a well-known procedure for determining the phases crystalline in the sample. The phase identification is simple in case of the isotropic powder samples, however the standard investigation protocol cannot always be used, e.g. in case if the presence of anisotropy like preferred orientation (PO) is observed. In case of steels, the diffracted intensity of a given phases is influenced by the directional phase development having a needle character caused by the martensitic transformation; some reflections can even disappear from the diffractograms as a consequence of the strong PO. One impacting consequence of PO is over quantitative evaluation, percentages close to actual values are obtained only if diffracted intensity is integrated for the whole measured 2θ range for each phase and anomalous intensities caused by PO are corrected. Incorrect quantitative values were obtained by using the full-profile analysis method in the course of our earlier investigations, because no correction method had been available for the recognition and evaluation of the orientated structures in phase-identification of metals. By using the Rietveld refinement method for whole measured 2θ range, both the PO and the size-strain broadening effects are accounted for. Strain results from stress developing in the lattice and can be taken into consideration in the calculated model and results are corrected to accurately describe the real structure. In the course of our research work, orientated, complex structures developing in the Cu-base alloys were investigated by using the Rietveld refinement method. The quantity of phases was determined in the different samples in which clear signs of the used technological processes could be observed in the structures. The character of orientation appearing in the structure was observed, evaluated and the necessary corrections were performed.

Self-supported and flexible bacterial cellulose (BC) based hybrid membranes were synthesized and decorated with zinc oxide/multi-walled carbon nanotube (ZnO–MWCNT) composite additives in order to modify and tune their surface and bulk properties. Two types of ZnO–MWCNT additives with different morphologies were used in a wide concentration range from 0 to 90% for BC-based hybrids produced by filtration. The interaction between BC and ZnO–MWCNT and the effect of concentration and morphology of additives on the properties like zeta potential, hydrophilicity, electrical conductivity, etc. would be an important factor in various applications. Furthermore, the as-prepared hybrid membranes were characterized with the use of scanning electron microscopy (SEM), focused ion beam scanning electron microscopy (FIB-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and surface area measurement (BET). Applying the presented synthesis routes, the surface properties of BC-based membranes can be tailored easily. Results reveal that the as-prepared BC–ZnO–MWCNT hybrid membranes can be ideal candidates for different kinds of applications, such as water filtration or catalysts.

The role of organic solvents in governing the crystallization and morphology of semi-crystalline poly-l-lactide (PLLA) sheets was systematically investigated. Three different organic solvents, ethyl acetate (EA), o-dichlorobenzene (ODCB), and nitrobenzene (NB), with a solubility parameter analogous to PLLA and with a high capability of swelling, were chosen. It has been witnessed that the degree of crystallization and crystal morphology depends highly on the degree of swelling and evaporation rate of the solvent. Besides, the temperature and time of treatment played a significant role in the crystallization of polymers. The effect of different solvents and curing times are reflected by the measured X-ray diffraction (XRD) peaks and the differences are best shown by the unit cell size. The largest variation is observed along the c-axis, indicating shorter bonds, thus, showing better conformation after NB and ODCB treatment. The percentage of crystallinity calculated using the classical relative crystallinity index of XRD shows closer values to those calculated with differential scanning calorimetry (DSC) data, but a huge variation is observed while using the LeBail deconvolution method. The strong birefringence of polarised optical micrograph (POM) and the crystal morphology of scanning electron micrograph (SEM) also evidenced the orientation of polymer crystallites and increased crystallinity after solvent-supported heat treatment.

Shrinkage of Ni (X) and Si (Y) versus the annealing time at 453K reveals the parabolic kinetics in all cases; shrinkage of a-Si is faster than that of c-Si due to the high diffusivity of Ni in a-Si.Display Omitted Reaction in nanocrystalline-Ni/amorphous Si or Si(100) systems at low temperature.Shift of individual interfaces of reaction layer was determined in very early stage.Kinetics of shrinkage of nanocrystalline Ni and Si layers follows parabolic law.Formation of NiSi2 in the amorphous Si is due to high diffusivity of Ni. Nanocrystalline Ni(20nm)/crystalline-Si and Ni(20nm)/amorphous-Si systems were heat treated at 453K and 473K for 0.25-2h. The formation of the reaction layer at the interface and the positions of the individual interfaces were followed by depth profiling using Secondary Neutral Mass Spectrometry and a profilometer. The kinetics of the shrinkage of the initial nanocrystalline Ni film and the Si layer, as well as the average growth kinetics of the product layer containing Ni2Si and NiSi phases, were determined in the very early stage of the solid state reaction. The kinetics of the Si and Ni shrinkage followed the parabolic growth law in both systems i.e. the change of the thicknesses were proportional to t1/2. In systems with a-Si, at longer annealing times, a layer with composition of about 40% Ni was developed suggesting the formation of the NiSi2. This was interpreted by the relatively high diffusivity of Ni in a-Si. Results on the effect of Pt on the enhanced homogeneity of the NiSi phase formed as well as on the growth kinetics are also presented.

Fly ash is a fine powder residue resulted from combustion of pulverized coal in thermal power plants. Different size fractions of fly ash have different properties. Four size fractions (with characteristic particle diameter D 50 of 40.37, 23.64, 10.33 and 2.98 μm respectively) collected from different fields of an electrostatic precipitator and representing the entire particle spectrum of fly ash has been selected for the study. These fractions have been characterized for their granulometry, chemistry, glass content and mineralogical phases. Geopolymerisation of size fractioned fly ash has been carried out at ambient (27 °C) and elevated (60 °C) temperature using isothermal conduction calorimetry (ICC) and the microstructure has been studied using X-ray diffractometry (XRD), scanning electron microscopy with X-ray microanalysis probe (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). Calorimetric studies showed that the heat flow curve during geopolymerisation has linear correlation with the glass content of fly ash. The compressive strength development at both ambient and elevated temperature was due to the combined effect of SiO 2 /Al 2 O 3 ratio, particle size and glass content. SEM-EDS studies have shown more reaction product in finer fractions and unreacted particles in coarser fractions. Formation of more thermonatrite phase was due to poor reactivity of coarse size fraction resulting into free alkali which in presence of atmospheric carbon formed Na 2 CO 3 ⋅H 2 O.

Present paper deals with the mechanical activation of deposited brown coal y ash in a high energy density mill. The mechanical activation was carried out in a laboratory scale stirred media mill using various rotor circumferential speed (5 and 7 m/s), and di erent grinding time (from 1 min up to 180 min). The consumed energy was measured during the grinding process. Furthermore, particle size distribution and speci c surface area were determined using laser particle size analyzer. The structural changes were detected by Fourier transform infrared spectroscopy. Additionally, transformation in mineralogical phases was measured by X-ray di raction, as well as particle morphology and crystal defects were determined by transmission electron microscopy. As a result of the investigation, relationship between the technological parameters of the grinding and the properties of the ground material was created. It was found that there is a certain mechanochemical e ect on the crystal structure of y ash components in the stirred media mill, as it was revealed by X-ray di raction and transmission electron microscopy. The most e cient grinding parameters were determined.

Forsterite, a new biocompatible material was synthesized from Mg(NO3)2·6H2O and TEOS by using the sol–gel method. The material was then heated at 800, 900 and 1000 °C. The forsterite was noticed as the main crystalline phase in the material fired at 900 and 1000 °C, while periclase (MgO) was present in all the samples. The tests confirm that in the first two samples forsterite is present as crystallites

In the traditional heavy-clay industry, compounds are usually prepared by the addition of organic waste material. These additives originate mainly from the wood, food or paper industries. The purpose of this study is to present the results of the examination of friction contact between the wall of the forming die and the clay compounds containing organic additives. Saw dust and ground sunflower seed shell were mixed to clay in 0 wt%, 3 wt% and 5 wt%. The water content of compounds was also varied. The clay and the additives were described by morphology, XRD, bulk density and equivalent diameter. Friction tests were carried out on a special tribometer up to plastic deformation of the sample. The coefficient of friction decreased when normal stress was increased for all the ten compounds. Average results showed that the tendency of change in the value of the coefficient of friction could be divided into three sections: a decreasing, a quasi constant and a shearing section. It follows from this that the coefficient of friction can be characterized with a number only inside the quasi constant section, i.e. between two definable normal stress values. Averaged coefficient of friction was between 0.17 and 0.21 for saw dust and between 0.19 and 0.21 for the compounds with ground sunflower seed shell.

Properties of powders made from Ti 50 Cu 27,5 Ni 10 Zr 10 Co 2,5 alloy, milled under different conditions for only 3600 s in total were investigated. For this purpose two different milling atmospheres and two different Process Control Agents (PCA) were tested: argon without PCA, air without PCA, argon combined with stearic acid, argon combined with petroleum spirit. Results showed that the size and shape of particles, and the microstrucutre and hardness of partcicles were highly depended on the milling conditions. According to XRD analysis, the maximal amorphous fraction has been achieved in the air atmosphere withouth PCA milled sample (57 wt. %) powder. However the extent of Fe contamination and weight loss during milling powder resulted bigger values. As a result, the optimal combination of morphology, contamination amount and weight lost level has been observed in the case of powder milled in argon atmosphere using stearic acid.

Nanocrystalline/amorphous powder was produced by ball milling of Ti50Cu25Ni20Sn5 (at.%) master alloy. Both laser diffraction particle size analyzer and scanning electron microscope (SEM) were used to monitor the changes in the particle size as well as in the shape of particles as a function of milling time. During ball milling, the average particle size decreased with milling time from &gt, 320 &micro, m to ~38 &micro, m after 180 min of milling. The deformation-induced hardening and phase transformation caused the hardness value to increase from 506 to 779 HV. X-ray diffraction (XRD) analysis was used to observe the changes in the phases/amorphous content as a function of milling time. The amount of amorphous fraction increased continuously until 120 min milling (36 wt % amorphous content). The interval of crystallite size was between 1 and 10 nm after 180 min of milling with 25 wt % amorphous fractions. Cubic Cu(Ni,Cu)Ti2 structure was transformed into the orthorhombic structure owing to the shear/stress, dislocations, and Cu substitution during the milling process.

Vegetal materials are generated in high amounts and are applied as additives in clay bricks since ancient times. They have a certain heat contribution to the firing process. As revealed by X-ray Powder Diffraction, main component of vegetal waste materials is cellulose. Thermal and Evolved Gas Analysis revealed the combustion process in its details. Mixtures of clay and vegetal additives prepare for test bodies were analyzed by Thermal Analysis. The thermal effects were quantified by Differential Thermal Analysis and correlated with Thermogravimetry and Derivative Thermogravimetry.

Experimental work was conducted on illite-chlorite and kaolinite-carbonate rich clays to investigate effects of pore forming additive materials. Three types of additives were applied: vegetal materials like sawdust, sunflower seeds hull and rice husks; lignite, as high organic content mineral material; fuel-grade coke, as synthetic additive. Raw materials were characterized regarding their composition, thermal behavior, microstructure and chemical composition. Expansion of extruded samples was detected after pressing release. Correlations were determined between the type and cellulose content of vegetal materials and expansion caused. The mineral and synthetic additive does not produce expansion, but lowers the working moisture needed.

A plastic brick clay with high clay mineral content was selected and the effects of different extruder heads on the main physical properties of the extruded products were investigated. The raw material was processed by a laboratory extruder after homogenization and wetting. Extruder heads with conical and special (spherical and torus) inner shape were applied to form and produce the green products which were examined after drying and firing. The rotation of the extruder screw was also varied between 15-55 1/min. Applying optical microscopy and SEM, the structure of the green products was analyzed. In addition to the physical properties of the products, the pressure caused by the extruder heads was determined by theoretical calculation and measurement. The results revealed that the physical properties of the products could be changed only by changing the shaping die geometry when the product size and production method remained unchanged. Maximal compressive strength of fired brick products (35.45 MPa) was obtained in case of the spherical head while the use of torus head caused some 5% decrease in the power consumption of the extruder. The density of fired products decreased and water adsorption increased when the rotation speed of the extruder screw was increased. The measurements confirmed the theoretical order of the applied extruder heads in terms of capability of pressure generation.