Search

Glass microballoons (GMBs) are commonly used to reduce the density of epoxy-resin syntactic foams, but they can also be applied as a low-cost and lightweight catalyst support. In order to create a practical structure that can be utilized for such an application, a ceramic syntactic foam consisting of glass microballoons (GMBs) and silica nanofibers (NFs) with or without TiO2 binder was synthesized. The mechanical strength, phase composition, high-temperature deformation behavior, and microstructure of the composite material were analyzed using bending and compression tests, X-ray diffraction, and scanning electron microscopy, respectively. It was determined that the addition of nanofibers improves the thermal behavior and mechanical strength of the composite material during and after processing. The composite materials maintained up to 70% anatase titania at as high as 700 °C, and this indicates that they can be of interest for high-temperature catalysis. No high-temperature deformation of GMBs was observed at 800 °C or 1000 °C, whereas XRD of samples coated with TiO2 using a titanium oxysulfate solution indicated the formation of cristobalite above 800 °C. Preliminary methane-reforming experiments were performed with NiO-seeded titania-coated GMBs, uncoated GMBs, and an uncoated silica fibers/GMBs composite. Uncoated GMBs and titania-coated GMBs had a low conversion ratio of methane to products, but the uncoated composite structure showed high conversion of the reactants at high temperatures, indicating that it may be suitable catalyst support in this reaction.

High-yield, free-surface alternating field electrospinning (AFES) was effectively used in the fabrication of titanium oxide nanofibrous materials from the precursors based on titanium alkoxide and a blend of polyvinylpyrrolidone and hydroxypropyl cellulose. The alkoxide/polymer mass ratio in the precursor solution has significant effects on the precursor fiber production rate as well as the structure of resulting TiO2 nanofibers after thermal processing of precursor fibers at temperatures from 500 to 1000 °C. Within the range of tested process parameters, the best fiber production rate of ∼5.2 g h−1 was achieved, in terms of the mass of crystallized TiO2 nanofibers, with the precursor that corresponded to 1.5 : 1 TiO2/polymer mass ratio. TiO2 nanofibers produced by calcination at 500 °C for 3 h had 100–500 nm diameters and were composed of anatase (20–25 nm crystallite size) with rutile content 0.1–6.0 mol%, depending on the precursor composition. A considerable amount of anatase phase (up to 80 mol%) can be retained after thermal processing of TiO2 nanofibers at 750 °C for 3 h. A nanofibrous material composed of smooth and long, predominantly monocrystalline rutile, fibrous segments was produced at 1000 °C from the precursor with 2.5 : 1 TiO2/polymer mass ratio.

Nanofibrous zirconia (ZrO2) meshes were prepared from precursor fibers which were synthesized using the method of free-surface, high-yield alternating field electrospinning (AFES). The weight ratio of zirconyl chloride salt to polyvinylpyrrolidone (PVP) polymer in liquid precursors was investigated for its effect on the spinnability and formation of precursor fibers as well as on the resulting fibrous ZrO2. The precursor fiber generation measured at a rate up to 5.6 g/h was achieved with a single flat 25-mm diameter alternating current (AC) electrode, which corresponded to production of up to 1.5 g/h of fibrous ZrO2. The calcination process involved annealing the fibers at temperatures which ranged from 600 °C to 1000 °C and produced 0.1–0.2 mm thick fibrous ZrO2 meshes. Individual nanofibers were found to have diameters between 50 and 350 nm and either a tetragonal (t-ZrO2) or monoclinic (t-ZrO2) structure depending on the calcination temperature. The annealed meshes with total porosity between 98.0 ± 0.2% and 94.6 ± 0.2% showed little deformation or cracking. Tensile strength and modulus of fibrous t-ZrO2 meshes strongly depended on porosity and varied from 0.07 ± 0.03 MPa to 1.05 ± 0.3 MPa and from 90 ± 40 MPa to 388 ± 20 MPa, respectively. The m-ZrO2 meshes resulted similar moduli, but much lower strengths due to their brittleness. A power-law relationship between the elastic modulus and porosity of AFES-derived nanofibrous t-ZrO2 meshes, in comparison with other porous zirconia materials, was also investigated. The results of this study have demonstrated the feasibility of free-surface AFES in sizeable production of zirconia nanofibers and highly porous nanofibrous ceramic structures.

Nanocellulose/polyvinylpyrrolidone (nCel/PVP) fibrous composite materials containing rod-like nanocrystalline cellulose particles with the lengths varying in the range from 100 to 2000 nm were prepared by using DC electrospinning. The particle size had a strong effect on the precursor viscosity, process efficiency, and resulting fiber diameter. The thermal crosslinking of nCel/PVP composite nanofibers with up to 1.0 : 8.0 nCel/PVP weight ratio resulted in fibrous membranes with textural, air transport, and mass swelling properties varying significantly with the size of cellulose particles. The presence of nCel particles increased the oxidation resistance of PVP during the crosslinking and affected the morphological changes of nCel/PVP fibrous membranes in aqueous solutions. Particles with the smallest size improved the strength of the membrane but decreased its mass swelling capacity, whereas the larger particles led to a more porous and flexible, but mechanically weaker, membrane structure with a higher swelling ability. Thus, by using the nCel particles of different size and shape, the properties of nCel/PVP composite fibrous membranes can be tailored to a specific application.

Catalytic systems based on bimetallic Pd-Au particles deposited on SiO2 were prepared by ultrasonically assisted water impregnation and used in the hydrogenation of furfural obtained by the acidic hydrolysis of waste biomass (brewery&rsquo, s spent grain) in aqueous phase. Pd-Au/SiO2 catalysts containing 50 g of Pd and 2&ndash, 100 g of Au per 1 kg of catalyst were characterized by high activity in the studied process and, depending on the Pd/Au ratio, selectivity to 2-methyloxolan-2-ol. The modification of 5%Pd/SiO2 by Au leads to the formation of dispersed Au-Pd solid solution phases, which was confirmed by XRD, XPS, ToF-SIMS, SEM-EDS, and H2-TPR techniques. The effect of dilution of surface palladium by gold atoms is probably crucial for modification of the reaction mechanism and formation of 2-methyloxolan-2-ol as the main product.

This paper presents an overview of alternative uses for products of sugar beet processing, especially sucrose, as chemical raw materials for the production of biodegradable polymers. Traditionally, sucrose has not been considered as a chemical raw material, because of its use in the food industry and high sugar prices. Beet pulp and beetroot leaves have also not been considered as raw materials for chemical production processes until recently. However, current changes in the European sugar market could lead to falling demand and overproduction of sucrose. Increases in the production of white sugar will also increase the production of waste biomass, as a result of the processing of larger quantities of sugar beet. This creates an opportunity for the development of new chemical technologies based on the use of products of sugar beet processing as raw materials. Promising methods for producing functionalized materials include the acidic hydrolysis of sugars (sucrose, biomass polysaccharides), the catalytic dehydration of monosaccharides to HMF followed by catalytic oxidation of HMF to FDCA and polymerization to biodegradable polymers. The technologies reviewed in this article will be of interest both to industry and science.

Nanofibrous glass/ceramic rigid shapes with uncommon structures, consisting of electrospun vitreous silica nanofibers coated with 5–30 nm thick Al2O3 or MgAl2O4 ceramic layers, were fabricated in this study. Ceramic nanolayers restricted the viscous flow in silica nanofibers and provided strong structural bonding during partial sintering at 1200 °C. The interface interactions between the silica nanofiber core and ceramic nanolayer during sintering defined the resulting microarchitecture, porosity, and phase composition of the material. Nanofibrous glass-ceramic slabs with 90 ± 2% porosity revealed flexural and compressive strengths in the range from 0.7 to 3.2 MPa due to the combined effects of the compounds formed in the silica nanofiber core, ceramic layer, and at their interface. The structural uniformity and mechanical properties of nanofibrous glass/ceramic shapes make them strong alternatives to microfibrous porous ceramics in various applications, especially when a small size of ceramic components is needed.

Cotton is grown in about 90 countries and accounts for 24% of the fibers used in the global production of textiles. In 2018/2019, 25.8 Mt of cotton were produced around the world. Since this natural product consists mainly of cellulose, it can be used as a raw material in the so-called “sugar economy”. This paper discusses a model procedure for thermally assisted acidic hydrolysis of cotton into glucose and subsequent oxidation of the glucose into calcium gluconate over Pd-Au/SiO2 catalyst. In the first step, H2SO4 was used as a catalyst for hydrolysis. The cotton hydrolysates were neutralized using CaCO3 and applied as a substrate in the second step, where glucose was oxidized over Pd-Au/SiO2 prepared by ultrasound assisted co-impregnation. With the appropriate Au/Pd molar ratio, small crystallites of palladium and gold were created which were active and selective towards the formation of gluconate ions. This approach to the transformation of glucose represents as a viable alternative to biological processes using fungal and bacterial species, which are sensitive to the presence of inhibitors such as furfurals and levulinic acid in hydrolysates.

Nanofibrous alumina (Al2O3) structures were fabricated from the precursor aluminum nitrate/polyvinylpyrrolidone (PVP) nanofibers prepared using a free-surface alternating current (AC) electrospinning method. Precursor nanofibers were generated at rates up to 6.4 g/h and collected as 100–300 µm thick sheets suitable for direct conversion into the nanofibrous alumina structures. The effects of process conditions and annealing temperature on the nanofiber diameter, morphology, shrinking behavior and crystalline phase formation were investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). Textural properties of Al2O3 fibrous sheets composed of micro-/meso-porous nanocrystalline γ-alumina nanofibers with 260±90 nm diameters after the calcination at temperatures in the range from 700 °C to 1000 °C were determined from N2 adsorption/desorption isotherms. Preliminary air permeability and apparent air flow resistance studies of single sheet and multilayer nanofibrous alumina membranes were performed and compared with other porous alumina membrane structures for the evaluation of their possible usage in gas filtration, separation, and other applications.

Poly(e-caprolactone) (PCL) biopolymer nano- and micro-fibers have been fabricated at high rates up to 14.0 grams per hour using a needleless and collectorless alternating current electrospinning technique. By combining the ac-voltage, glacial acetic acid (AA) as the solvent and sodium acetate (NaAc) as an additive, beadless PCL fibers with diameters tunable from 150 nm to 2000 nm, varying surface morphology and degree of self-bundling were obtained. In this new approach, the addition of NaAc plays a crucial role in improving the spinnability of PCL solution and fiber morphology. NaAc revealed the concentration-dependent effect on charge transfer and rheological properties of the PCL/AA precursor, which results in broader ranges of spinnable PCL concentrations and ac-voltages suitable for rapid manufacturing of PCL-based fibers with different textural properties.

Tungsten oxide (WO 3 ) nanofibers with cylindrical (400±200 nm diameter) and ribbon-like (80±10 nm thick ribbons with the width-to-thickness ratio of up to 50:1) shapes were prepared by annealing electrospun polyvinylpyrrolidone/ammonium metatungstate (PVP/AMT) fibers with 1:1 PVP/AMT weight ratio. The effects of annealing temperature (573–1173 K), time (1–12 h), and fibers׳ shape on their crystalline structure and stability were investigated. Only a polycrystalline monoclinic phase of WO 3 was observed in all experiments, and the grain size increased with temperature and time from a few nanometers to ~1 μm. Results have shown that thermal stability of fibers depend on their shape and whether or not the fibers are clamped to the substrate. Loose fibers of both types were stable to at least 873 K. Ribbon-like structures degraded between 873 K and 973 K, whereas some fraction of cylindrical fibers survived annealing at 1173 K. When both types of fibers were clamped to silicon substrate, annealing above 873 K led to their partial disintegration with the formation of large needle and lamellar WO 3 crystals.

Lactic acid (LA) can be obtained easily through fermentation of saccharides, and is an extremely useful building block for the synthesis of valuable chemicals, including propylene glycol (PG). Catalysis is one of the key elements in this platform approach. The present study focuses on PG synthesis via catalytic hydrogenation of lactate ions. In the conventional biological method, separation and downstream processing of pure LA account for up to 50% of production costs. Therefore, we propose using a less pure solution of lactate ions as a feedstock. To this end, we have developed a new method for the treatment of post-fermentation broth containing calcium lactate, obtained from sugar beet pulp. Activated carbon was used for the purification of the post-fermentation broth, which was acidified to pH 2–3. Hydrogenation of LA into PG was performed over supported metallic catalysts, based mainly on ruthenium, under mild conditions. The yield of PG was satisfactory and the PG water solution obtained could be used in concentrated form as a component in antifreeze.

Catalytic systems based on highly dispersed Pd nanoparticles deposited on SiO2 modified with PVP, AMPS and AcrAMPS were prepared and used in the hydrogenation of furfural obtained by the aqueous phase acidic hydrolysis of waste biomass (sugar beet pulp, sugar beet leaves, and brewing grain) from the food industry. Pd/PVP/SiO2 catalysts containing 50 g of Pd per 1 kg of catalyst were characterized by high activity in studied process, but lower selectivity to THFA in comparison to Pd/AMPS-SiO2 or Pd/AcrAMPS-SiO2 catalysts. The modification of SiO2 by PVP followed by the palladium catalyst loading, limited the adsorption of furfural by carbonyl group which probably leads to the improvement in THFA formation, which was confirmed by FTIR studies. The physico-chemical properties of the obtained palladium catalysts were investigated by XRD, CO chemisorption, TPR H2, TG-DTA-MS and BET techniques. The ICP-AES indicated no leaching of metal into the environment during furfural reduction, which confirms the stability of the Pd/PVP/SiO2, Pd/AMPS-SiO2 and Pd/AcrAMPS-SiO2 systems in the studied process.

Nanotechnologies allow the production of yarns containing nanofibres for use in composites, membranes and biomedical materials. Composite yarns with a conventional thread core for mechanical strength and a nanofibrous envelope for functionality, e.g. biological, catalytic, have many advantages. Until now, the production of such yarns has been technologically difficult. Here, we show an approach to composite yarn production whereby a plume of nanofibers generated by high throughput AC needleless and collectorless electrospinning is wound around a classic thread. In the resulting yarn, nanofibres can form up to 80% of its weight. Our yarn production speed was 10 m/min; testing showed this can be increased to 60 m/min. After the yarn was embedded into knitwear, scanning electron microscope images revealed an intact nanofibrous envelope of the composite yarn. Our results indicate that this production method could lead to the widespread production and use of composite nanofibrous yarns on an industrial scale.

Detonation nanodiamonds (DND), with low hydrogen content, were exposed to microwave plasma generated in pure H2, N2, and O2 gases and their mixtures, and investigated using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman, and X-ray photoelectron spectroscopies. Considerable alteration of the DND surface was observed under the plasma conditions for all used gases, but the diamond structure of the DND particle core was preserved in most cases. The stabilizing effect of H2 in H2/N2 and H2/O2 binary gas plasmas on the DND structure and the temperature-dependent formation of various CNHx surface groups in N2 and H2/N2 plasmas were observed and discussed for the first time. DND surface oxidation and etching were the main effects of O2 plasma, whereas the N2 plasma led to DND surfaces rich in amide groups below 1073 K and nitrile groups at higher temperatures. Noticeable graphitization of the DND core structure was detected only in N2 plasma when the substrate temperature was above 1103 K.

A new low-cost pathway for the production of high-value propylene glycol (PG) is proposed. This route of waste biomass utilization employs catalytic reduction of lactic acid obtained from fermented enzymatic digests of sugar beet pulp.

Tungsten oxide (WO3) nanofibers with shapes ranging from cylindrical to ribbon-like were prepared by annealing electrospun polyvinylpyrrolidone/ammonium metatungstate (PVP/AMT) fibers. Formation of periodically folded “zigzag” patterns in PVP/AMT and WO3 ribbon-like fibers was observed for the first time at the initial stage of the electrospinning process on the surface of a stationary substrate. Among methods tested (capillary needle, needleless dc- and ac-electrospinning), only the capillary needle dc-electrospinning process was effective in producing ribbon-like fiber structures. Annealing of such PVP/AMT fibers at 500 °C in air led to the formation of 80 ± 10 nm thick WO3 ribbons with a width-to-thickness ratio of up to 50 : 1. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Raman spectroscopy were used to analyze the material. Analyses revealed that regardless the fiber's shape, the annealed oxide fibers were polycrystalline with a grain size of 60 ± 30 nm and consisted of the monoclinic phase of WO3. When compared to cylindrical fibers, the ribbon-like WO3 nanofibers exhibited higher porosity but lower mechanical strength with increased width of the ribbon-like structure.

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-β-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

The effect of iron introduction on the activity and selectivity of chemically precipitated supported palladium catalysts in the hydrodechlorination of 2,4-dichlorophenol in liquid phase at room temperature was studied. Bimetallic Pd–Fe catalysts supported on silica and alumina were characterized by using XPS, XRD, ToF-SIMS and TPR-H2 techniques. The dispersion of active phase in catalytic systems was examined by XRD and chemisorption of CO gas. Bimetallic Pd–Fe/SiO2 and Pd–Fe/Al2O3 catalysts containing 5 wt.% of Pd and 1–20 wt.% of Fe demonstrated high activity and high selectivity to phenol. However, Pd–Fe/Al2O3 catalysts with higher dispersion of the active phase were less active in the studied reaction than Pd–Fe/SiO2 systems, but selectivity to phenol was comparable for both types of bimetallic catalysts. The stability of Pd–Fe/SiO2 systems was higher than the bimetallic Pd–Fe/Al2O3 catalysts but selectivity to phenol decreases for that system systematically in each cycle of reaction, reaching only about 40% in the tenth cycle. It was also found that the addition of Fe to palladium catalysts limited the formation of cyclohexanone in the reaction medium.

Highly porous, 0.1–1.5 mm thick fibrous amorphous silica (FAS) meshes with 500 ± 200 nm fiber diameters were prepared from the precursor fibers made by a high-yield free-surface alternating field electrospinning (AFES) process. A combination of mild thermal and pressure treatment of the fibrous precursor material before the calcination step was used to tailor the mechanical and transport properties of the resulting FAS structures. Compression of the as-spun material determined the resulting porosity, effective fiber diameter, and microarchitecture of the FAS structures when calcined between 600 and 1000 °C. Flexible FAS meshes and membranes revealed the tensile strength and modulus up to 1.4 MPa and 580 MPa, respectively, and Darcy'S permeability coefficient in a range of 1.2 × 10−12–1.6 × 10−11 m2. Taking into consideration the compression-dependent effective fiber diameter, the permeability of compressed FAS membranes fitted the models developed for two-dimensional fibrous layer architectures with partial fiber alignment within the stacked layers.

Palladium catalysts promoted with a second metal demonstrate good activity and selectivity in many important oxidation and reduction reactions. The influence of co-metal on the catalytic performance of Pd depends on interaction between the two components and by the chemical state of both the Pd and co-metal. The understanding of the nature of such interaction is important in the optimization of such catalysts and development of new Pd-based catalyst systems with improved performance and stability. In this study, the surface structure and chemical states in several Pd–M/supported catalysts (where M = In, Bi, and Te) were experimentally investigated by using time-of-flight secondary ion mass spectroscopy (ToF-SIMS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It has been found that the formation of the intermetallic compounds and their composition can be responsible for a reduction or increase of catalytic activity and selectivity previously observed for the studied Pd–M systems.

Tungsten carbide-based coatings have been used in a wide variety of industrial applications such as high speed cutting tools, extrusion dies, drills, aerospace industries, and more. A few reports on ternary and quaternary coatings of WC with other elements indicate good prospects for these material systems. The present study focuses on the formation of quaternary WCeCreN and WCeAleN coatings during the simultaneous reactive RF-magnetron sputtering of tungsten carbide and Al or Cr targets in an argon/nitrogen gas mixture. The resulting coatings, with thicknesses of 3.5 mme8.2 mm, were characterized by using several analytical techniques including X-ray diffraction, SEM/EDS, AFM, and X-ray photoelectron spectroscopy. WCeCreN and WCeAleN coatings with high levels of tungsten (i.e. more than 50 at.% of the total metal content) demonstrated dense microstructure. Coatings with lower tungsten content formed columnar grain microstructure, with different surface morphologies depending on the process parameters. It was proposed that crystalline tungsten carbide (with partial N-substitution of C atoms) and chromium (or aluminum) nitride phases coexist in the coatings when the amount of tungsten was greater than 50 at.% of the total metal content; while at lower tungsten content, the dominating crystalline phase is either W-doped CrN1 y or AlN1 y solid solution, with WC1 x and small amounts of free sp2-bonded carbon present as X-ray amorphous phases.

Nanoparticles are used in an increasing number of biomedical, industrial, and food applications, but their safety profiles in developing organisms, including the human fetus and infant, have not been evaluated. Titanium oxide (TiO2) nanoparticles, which are commonly used in cosmetics, sunscreens, paints, and food, have been shown to induce emphysema and lung inflammation in adult mice. We hypothesized that exposure of newborn mice to TiO2 would induce lung inflammation and inhibit lung development. C57BL/6 mice were exposed to TiO2 (anatase; 8–10 nm) nanoparticles by intranasal instillation as a single dose on postnatal day 4 (P4) or as three doses on postnatal days 4, 7, and 10 (each dose = 1 μg/g body wt). Measurements of lung function (compliance and resistance), development (morphometry), inflammation (histology; multiplex analysis of bronchoalveolar lavage fluid for cytokines; PCR array and multiplex analysis of lung homogenates for cytokines) was performed on postnatal day 14. It was observed that a single dose of TiO2 nanoparticles led to inflammatory cell influx, and multiple doses led to increased inflammation and inhibition of lung development without significant effects on lung function. Macrophages were noted to take up the TiO2 nanoparticles, followed by polymorphonuclear infiltrate. Multiple cytokines and matrix metalloproteinase-9 were increased in lung homogenates, and VEGF was reduced. These results suggest that exposure of the developing lung to nanoparticles may lead to ineffective clearance by macrophages and persistent inflammation with resulting effects on lung development and may possibly impact the risk of respiratory disorders in later life.

Epitaxial boron-doped diamond films were grown by microwave plasma chemical vapor deposition for application as heating elements in high pressure diamond anvil cell devices. To a mixture of hydrogen, methane and oxygen, diborane concentrations of 240–1200 parts per million were added to prepare five diamond thin-film samples. Surface morphology has been observed to change depending on the amount of diborane added to the feed gas mixture. Single-crystal diamond film with a lowest room temperature resistivity of 18 mΩ cm was fabricated and temperature variation of resistivity was studied to a low temperature of 12 K. The observed minima in resistivity values with temperature for these samples have been attributed to a change in conduction mechanism from band conduction to hopping conduction. We also present a novel fabrication methodology for monocrystalline electrically conducting channels in diamond and present preliminary heating data with a boron-doped designer diamond anvil to 620 K at ambient pressure.

Fibrous nanocomposite scaffolds were electrospun from dispersions of hydroxyapatite nanoparticles (nanoHA) in polycaprolactone (PCL) with varying nanoHA contents (from 0% to 50% by weight). Such scaffolds were produced to mimic the nano-features of the extracellular matrix (ECM) for natural bone tissue regeneration. NanoHA was found to be well dispersed in the PCL fibers up to the addition of 30 wt%, whereas beads and agglomeration of HA particles was observed above this nanoHA concentration. The structural and morphological characterizations were evaluated by scanning electron microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). The average fiber diameter decreased with increased nanoHA concentration. The nanomechanical properties of the as-spun fibrous scaffolds as well as pressure-consolidated (pelletized) composites were evaluated by nanoindentation. Elastic modulus increased with increasing HA content, but was especially pronounced for 40-50% HA content where the indenter tip is more likely to probe agglomerated HA particles.

Undoped and boron-doped nanocrystalline (NCD) diamond films were deposited on mirror polished Ti-6Al-4V substrates in a Microwave Plasma Assisted Chemical Vapor Deposition system. Sliding wear tests were conducted in ambient air with a nanotribometer. A systematic study of the tribological properties for both undoped and boron-doped NCD films were carried out. It was found for diamond/diamond sliding, coefficient of friction decreases with increasing normal loads. It was also found that the wear rate of boron-doped NCD films is about 10 times higher than that of undoped films. A wear rate of ~5.2×10(-9) mm(3)/Nm was found for undoped NCD films. This value is comparable to the best known value of that of polished polycrystalline diamond films. Although no surface deformation, film delamination or micro-cracking were observed for undoped films, boron-doped NCD film undergoes a critical failure at a normal stress of 2.2 GPa, above which surface deformation is evident. Combined with high hardness and modulus, tunable conductivity and improved open air thermal stability, boron-doped nanocrystalline diamond film has tremendous potentials for applications such as Atomic Force Microscope probes, Micro-Electro-Mechanical System devices and biomedical sensors.

Hydroxyapatite (HA) nanoparticle-collagen composite materials with various HA/collagen weight ratios were prepared from HA/collagen dispersions using the solution deposition and electrospinning with static or rotating collectors. The composites with nanoparticle HA to collagen weight ratio of 80:20 can be easily prepared in the solution deposition approach, whereas in the electro-spun fibrous composites it was possible to reach a maximum HA/collagen weight ratio of 30:70 while maintaining a good fibrous structure. The structure, surface morphology, and nanoindentation properties of these nanoparticle HA/collagen composites with different microarchitectures were investigated. The values from 0.2 GPa to 20 GPa for nanoindentation Young's modulus and from 25 MPa to 500 MPa for hardness, were obtained depending on the fabrication technique, composition, and microarchitecture of the composites. It was observed that the nanoindentation Young's modulus and hardness of the HA/collagen composite materials seem to achieve maximum values for 45-60% HA content by weight. © 2007 Wiley Periodicals, 45-60% HA content by weight.

Background Some loss of joint prostheses has been attributed to osteolytic phenomena leading to loosening and associated with debris from wear of polyethylene articulating against metal alloys. Reduced polyethylene wear has been reported with ceramics serving as an alternative counterface.

We discuss the mechanical properties and wear characteristics of sol–gel CaTiO 3 nanocrystalline ceramic coatings on titanium substrates. The structure and surface morphology of the coatings were investigated by X-ray diffraction, optical profilometry, and atomic force microscopy. The mechanical properties of CaTiO 3 coatings were characterized by using nanoindentation, scratch- and microwear-tests. The effect of titanium nitride intermediate layer on the improvement of the coating properties has been investigated. The best CaTiO 3 coatings with a TiN intermediate layer demonstrated the bonding strength up to 70 MPa, stability and low linear wear rate (∼ 1 μm per million cycles) during ball-on-disc reciprocal wear tests in micromotion (50–500 μm amplitude) with Ti6Al4V-alloy static partner at contact pressures up to 500 MPa in both dry and simulated body fluid environments.

Diamond is increasingly used in biomedical applications because of its unique properties such as the highest thermal conductivity, good optical properties, high electrical breakdown voltage as well as excellent biocompatibility and chemical resistance. Diamond has also been introduced as an excellent substrate to make the functional microchip structures for electrophoresis, which is the most popular separation technique for the determination of analytes. In this investigation, a diamond electrophoretic chip was manufactured by a replica method using a silicon mold. A polycrystalline 300 micron-thick diamond layer was grown by the microwave plasma-assisted CVD (MPCVD) technique onto a patterned silicon substrate followed by the removal of the substrate. The geometry of microstructure, chemical composition, thermal and optical properties of the resulting free-standing diamond electrophoretic microchip structure were examined by CLSM, SFE, UV-Vis, Raman, XRD and X-ray Photoelectron Spectroscopy, and by a modified laser flash method for thermal property measurements.

The electroless plating of silver films on pure silver nanoparticle seed layers prepared by spin-coating and thermal decomposition of PVP/Ag nanoparticle composite has been investigated. The plating results strongly depend on the agglomeration of nanoparticles and interparticle distances in the seed layer, which in turn crucially depend on the thermal processing parameters. Uniform nanocrystalline 200-nm-thick silver films on glass were prepared by plating on nanoparticle layers with surface density of 5.7 × 10 10 cm − 2 and average particle size of 40 nm. It is shown that electroless plating on nanoparticle seed layers can produce different surface structures and can finely tune the surface plasmon resonance in nanoparticle layers that can be useful for optical and sensing applications.

In this paper we demonstrate a modified focused ion beam (FIB) milling approach integrated with self-alignment to synthesize ferroelectric nanostructures. Nanoscale holes ranging from 500 nm down to 100 nm in diameter are created on 'spun-on' amorphous TiO2 on Pt/TiO2/Si using FIB milling. It is found that spin-coating of PbZr0.4Ti0.6O3 (PZT) sol–gel precursors on these templated surfaces followed by low-temperature (~400 °C) annealing leads to a ferroelectric phase only within the holes. Piezoresponse force microscopy (PFM) was used to confirm that the crystallized phase within the holes were ferroelectric and switchable. The smallest lateral size shown to be ferroelectric is roughly 70–80 nm in diameter. Quantitative PFM of the nanoscale ferroelectric regions yielded a value of 17 pm V−1, in good agreement with previously published data on polycrystalline PZT. Additionally this method facilitates the integration of interlayer dielectrics or 'spun-on' glass during the synthesis without the need for additional lithography and processing.

In a number of studies, the formation of perovskite CaTiO 3 (CTO) phase was observed at the interface layer when depositing hydroxyapatite coatings onto biomedical titanium alloys. Recently, CTO itself has been proposed as a suitable candidate for biocompatible coatings for medical implants, particularly Ti implants. We report on polycrystalline CaTiO 3 coatings prepared on silicon and titanium using a sol–gel technique followed by rapid thermal processing (RTP). The structure, composition, and surface morphology of CTO coatings RTP crystallized in the range of 500–800 °C for 30–180 s were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and non-contact optical profilometry. Crystallization of single-phase CTO coatings on titanium is observed starting at 500 °C, while on Si, the coating remains amorphous at 550 °C, and an intermediate CaCO 3 phase is observed at up to 650 °C.

We report a method, based upon magnetic force microscopy (MFM), that permits the direct imaging of current distributions with submicron resolution. Magnetic force microscopy is used to measure the curvature of the magnetic field generated by a current-carrying structure. Maximum entropy deconvolution of the MFM phase image, followed by the application of a numerical inversion procedure derived from the Biot–Savart law, yields the current distribution in the sample. Careful theoretical analysis of the spatial resolution of this method shows that the lateral resolution is noise limited to approximately one quarter of the tip height. Since tip elevations of 100 nm are typical, we anticipate that this method has a spatial resolution of tens of nanometers. The method was used to determine the current distribution in the vicinity of a (1×9) μm2 slit-like defect embedded in a 11.5-μm-wide current-carrying metallic line. Current crowding and constriction are observed in the images and are resolved at the submicron level. The observed current distributions are found to be in good agreement with finite-element calculations of the current density for equivalent lines, confirming both the fidelity and the resolution of the imaging method.

We report magnetic and electrostatic phase imaging of micron-scale metallic lines covered with 525 nm of SiO 2 . Magnetic force microscopy (MFM) has been used to image a buried current-carrying line, to resolve its micron-scale defects, and characterize current crowding around those defects. The MFM phase signal from this structure compares quantitatively to the MFM signal from the same structure, taken prior to deposition of the oxide layer when transformed by a Green’s function propagation to account for the oxide thickness. The alternative use of electric force microscopy (EFM) to find the location of a break and identify void defects in buried lines is contrasted with MFM.

We studied the effect of ion damage on the properties of 50 keV Ga+ focused ion beam fabricated lead-zirconate-titanate capacitors as a function of the ion dose. We observed significant modification in the chemical composition of the damaged layer due to loss of lead and oxygen, and gallium impurity accumulation. The 5–10 nm thick damaged layer becomes dielectric after annealing and does not recover its ferroelectric properties. This dielectric layer substantially reduces the actual volume of the ferroelectric material in sub-100 nm structures, and can affect their performance.

The utility of vertical propagation by the Green’s function to test response linearity has been explored for magnetic force microscopy (MFM) data from current-carrying wires, by comparing the measured signal at various tip heights to the corresponding propagated MFM signals. Application of a one-dimensional Green’s function was found to be sufficient to predict signal height variation for sample regions of high to moderate field symmetry. For regions of high field asymmetry, the two-dimensional Green’s function was required to obtain good prediction of the height variation. Agreement between the measured and propagated signals was generally within 5%, except at the tails where the signal is not well behaved. The quality of agreement deteriorates gradually with the size of the height propagation. The good agreement spanning a decade of tip and sample separation suggests that the MFM signal is not significantly affected by nonlinearities and can thus be interpreted in terms of classical electromagnetic rela...

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-β-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

Needleless alternating current (AC)-electrospinning is capable of achieving high nanofiber generation rates while adding more flexibility to the process development when compared to common direct current (DC)-electrospinning. However, AC-electrospinning process may produce very different results than DC-electrospinning when using the same precursors. This study demonstrated that stable AC-electrospinning of uniform and mechanically strong polyacrylonitrile (PAN) nanofibrous meshes can be achieved at 30 ± 5 kV rms voltage when 0.75–6.0 wt % of nanocrystalline cellulose-II with respect to PAN is added to a typical PAN precursor solution. Efficient generation (up to 2 g/h rate or 0.7 g h−1 cm−2 mass flux) of nanofibers with 250–500 nm fiber diameters has been observed when using flat fiber-generating electrodes with diameters up to 25 mm. Depending on the amount of nanocellulose, nanofibrous nanocellulose/PAN meshes revealed large variations in tensile modulus (90–273 MPa) and yield strength (1.0–2.5 MPa), whereas the fiber diameter, air permeability, air resistance, mesh porosity, and water absorption were less affected. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45772.

Ternary B–C–N amorphous and crystalline coatings were deposited by microwave chemical vapor deposition using a mixture of NH 3 , CH 4 , B 2 H 6 and H 2 gases at substrate temperatures in the range 800–1350°C, and a gas pressure in the range (9.0–12)×10 3 Pa. We studied the influence of deposition conditions (i.e. gas composition, substrate temperature and material) on the coating structure, chemical composition and surface morphology. Both amorphous and polycrystalline coatings were deposited. Amorphous coatings were usually formed at lower substrate temperatures and were non-homogeneous across the coating thickness. Nanocrystalline inclusions of boron carbide, boron nitride and diamond were observed in amorphous B–C–N compounds. Polycrystalline coatings were generally represented by both diamond and boron nitride phases. In one case, a polycrystalline coating with the composition of B 2 CN 4 was fabricated. The experimental results are discussed in detail.

Applications of diamond and amorphous carbon films in micro-mechanical and sensor elements often require formation of submicron size patterns. A focused beam of 50 keV Ga+ ions was used in this work to fabricate sub-100-nm patterns in bulk diamond, CVD diamond and amorphous carbon films. The influence of the focused ion beam (FIB) parameters and ambient gas on the sputtering yield, surface morphology and structure modification of these materials was studied using ion microscopy, atomic force microscopy (AFM), measurements of electric resistivity and Raman spectroscopy. Detailed results on FIB gas assisted etching (GAE) are reported. GAE processes with NH3+Cl2 and XeF2 were found to enhance the sputtering yield of diamond and ta-C films 4–7 times. The electric resistivity of FIB GAE patterned material is almost independent on the ion dose and it is of 1–2 orders of magnitude higher when compared to the electric resistivity of non-assisted FIB patterned material.

A review is presented of approaches to integrate thin film Pb(Zr, Ti)O3-based ferroelectric capacitor structures on a filled poly-Si plug, which is a critical requirement for a high-density memory technology. Key materials issues relevant to the development of conducting diffusion barrier layers for integration of these materials on Si wafers are discussed. Specific attention in this paper is on the use of conducting perovskite oxide electrodes to contact the ferroelectric thin film. The second part of this review focuses on some novel materials that we have investigated for use as diffusion barriers. Finally, we present data on the scaling of ferroelectric properties with lateral dimensions of the capacitor.

Ti–Ti(N,O,C)–(Ti-C) n composite coatings with a thickness of about 1 μm were deposited on stainless steel substrates by continuous and pulsed arc discharge methods. The coatings were found to have a coefficient of friction in the range of 0.1–0.2, critical load for the coating delamination under a scratch test of 5.7–7.3 N, and microhardness of 21⊁25 GPa. Despite the comparatively small difference in values of the microhardness of the tested coatings, their service life under a pin-on-disk test varied by a factor of about 40. The mechanical properties of the upper layers were found to strongly affect the composite coating's service life and be dependent on the design and the deposition strategy of a top (Ti-C) n multilayer film containing a diamond-like carbon layer.