We have constructed a unified picture for icosahedral cluster solids by a comparative transdisciplinary research for the boron (B) icosahedral crystals in the field of semiconductors and the aluminum (Al)-based icosahedral quasicrystals in the field of metals. For the icosahedral cluster of Al, metallic-covalent bonding conversion occurs whether the center atom exists or not. When the center is occupied or not by the atom, the packing fraction approaches to the closest packing structure or becomes very low, and the cluster has metallic or covalent bonding. On the other hand, there are no elements which can occupy the center of icosahedron of B, whereas the similar situation appears when an atom occupies the interstitial A1 site, which has the similar environment to the center of icosahedron, in beta-rhombohedral boron (beta-B). The metallic-covalent bonding conversion occurs by doping of vanadium, which has high occupancy of the A1 site. The beta-B is a self-compensated solid, where the electron deficient of B12 icosahedral and excess of B28 clusters are compensated by the interstitial atoms and vacancies, respectively. When electrons are doped by occupation of the interstitial site in beta-B by Li or Mg, the doped electrons are compensated initially by the decrease of the interstitial atoms and the increase of the vacancies, then by generation of vacancies in the new site. The beta-B is the only elemental crystal where the self-compensation occurs. In the case of V-doped beta-B, the doped V atoms drop out by Li or Mg doping, which is considered to be extended self-compensation. This phenomenon is also considered to be metallic-ionic bonding conversion. For the Al-based approximant crystals of icosahedral quasicrystal, the self-compensation occurs, where a number of vacancies increases by the electron doping induced by the constituent element substitution.

Boron carbide (BC) possesses a number of unique characteristics that render it suitable for specialized device applications, including neutron detectors and low-k dielectrics. Since 10B is one of few isotopes with a high neutron capture cross section, boron carbide is one of a handful of boron-rich semiconductors under consideration for direct-conversion solid-state neutron detection. Further, with such a low average atomic number, BC has the potential to exhibit extremely low polarizability and therefore, a low dielectric constant, while also retaining chemical, thermal, and mechanical robustness, which positions well for low-k dielectric uses. For both of these applications, low leakage currents are required, and traditional semiconducting polycrystalline BxC (x ~ 4-11) is therefore unsuitable. A unique BC variant, amorphous hydrogenated boron carbide (a-BxC:Hy), fabricated by plasma-enhanced chemical vapor deposition from carborane precursors, has been found to possess the necessary semi-insulating properties for these applications. Known since the early 90's, carborane-based a-BxC:Hy has been the subject of some physical and electronic structure studies, but a lot remains to be done to thoroughly characterize its materials properties, as well as their tunability. Due to the amorphous nature of the solid, much of this characterization is nontrivial. Although it possesses a relatively similar stoichiometry to traditional BxC, a-BxC:Hy is a very different material, both in terms of atomic structure and material properties. Further, due to its complex bonding, it does not fall into a conventional framework for analysis, such as that developed for the classes of amorphous inorganic tetrahedral semiconductors or organic semiconductors. This contribution will describe recent efforts toward understanding a-BxC:Hy, including its local physical structure and the role of carbon and hydrogen, the nature of its electronic structure and disorder parameters such as Urbach energy, and their relationship to optical and electrical transport properties.

Boron carbide (BC) possesses a number of unique characteristics that render it suitable for specialized device applications, including neutron detectors and low-k dielectrics. Since 10B is one of few isotopes with a high neutron capture cross section, boron carbide is one of a handful of boron-rich semiconductors under consideration for direct-conversion solid-state neutron detection. Further, with such a low average atomic number, BC has the potential to exhibit extremely low polarizability and therefore, a low dielectric constant, while also retaining chemical, thermal, and mechanical robustness, which positions well for low-k dielectric uses. For both of these applications, low leakage currents are required, and traditional semiconducting polycrystalline BxC (x ~ 4-11) is therefore unsuitable. A unique BC variant, amorphous hydrogenated boron carbide (a-BxC:Hy), fabricated by plasma-enhanced chemical vapor deposition from carborane precursors, has been found to possess the necessary semi-insulating properties for these applications. Known since the early 90's, carborane-based a-BxC:Hy has been the subject of some physical and electronic structure studies, but a lot remains to be done to thoroughly characterize its materials properties, as well as their tunability. Due to the amorphous nature of the solid, much of this characterization is nontrivial. Although it possesses a relatively similar stoichiometry to traditional BxC, a-BxC:Hy is a very different material, both in terms of atomic structure and material properties. Further, due to its complex bonding, it does not fall into a conventional framework for analysis, such as that developed for the classes of amorphous inorganic tetrahedral semiconductors or organic semiconductors. This contribution will describe recent efforts toward understanding a-BxC:Hy, including its local physical structure and the role of carbon and hydrogen, the nature of its electronic structure and disorder parameters such as Urbach energy, and their relationship to optical and electrical transport properties.

Pigments are used to decorate ceramic bodies by incorporating them into glaze batches. Calcination temperature, the type of the mineralizator and glaze compositions significantly affect the color of the final glaze. In this study, Ca-borate and Mg-sulfate mineralizators were used to produce pigments and their effects on pigment production were investigated. The color of the glazes varied from pink to light brown depending on the pigment composition and type of the mineralizator affected the crystal structure of pigments. L*a*b* values of the glazes are measured by a spectrophotometer. Characterization of the pigments were conducted by XRD and SEM-EDX, respectively.

Sintering of composites based on nano-dispersed components of the system Fe-C at high pressures is of considerable interest because of the possibility to obtain improved physical and mechanical properties, in particular hardness and wear resistance. As the nanopowder source was used extracted fullerene soot (Cefs) micropowder and carbonyl iron with a particle size of 5-100 microns in a ratio of 90 wt. % Cefs: 10 wt. % Fe. The paper investigates the possibility of preparing a solid -Fe composite with a predominance of superhard carbon phase and a reflux ratio of the components of iron and carbon. A study of the fine structure of the nanocomposite, the refinement of the phase composition and the degree of disorder of the crystal structure was conducted. In order to study the fine structure of the nanocomposite, refinement of the phase composition and the degree of disorder of the crystal structure, methods of transmission electron microscopy (TEM), electron diffraction in the high resolution, raman spectroscopy and combination scattering spectrometer were used.

In this study, production of porcelain for the ceramic dielectric applications by using inexpensive natural raw materials or waste materials was undertaken. The principal raw materials of porcelain, such as kaolin, feldspar and quartz are relatively inexpensive and readily available. The basic electro-porcelain composition was selected consisting of 20% clay, 30% kaolin, 30% potash-feldspar and 20% quartz. The samples synthesized were characterized by X-ray diffraction (XRD) technique. The dielectric properties of porcelain bodies prepared, e.g. dielectric constant, dielectric loss tangent (tan δ) and loss factor, were investigated. Dielectric measurements have been carried out at 1 KHz in the ambient temperature. The dielectric constant ε' of standard porcelain and porcelain with boric acid samples sintered at the most proper sintering temperature 1310°C were about 8 and 16 respectively. The value of dielectric constant of porcelain with boric acid is higher as compared to standard porcelain.

In this study, mullite/zirconia composites were synthesized by reaction sintering from zircon, kaolinite and alumina mixtures having colemanite additions (wt. % 7). Prepared mixtures were sintered at 1450, 1500 and 15500C temperatures for 5 hrs. These two mixtures were compared using DTA and XRD analyses according to some physical properties. It was determined through both DTA and XRD analyses that colemanite addition to mullite/zirconia composite synthesis lowers reaction temperature. While zircon in the mixture without colemanite existed up to 1550oC, it decays completely in the composition with colemanite at 1450oC

Boron carbide – aluminium (B4C – Al) ceramic – metal composites are promising materials especially in armour applications for body and vehicle protection, where lightness is one of the most important constraints. Boron carbide provides high hardness and elastic modulus to the composite and its low toughness is increased with metal reinforcement via composite production approach. Al is a generally preferred metal with its low density, low melting point and cost effectiveness. Increasing the toughness with minimum loss of hardness and strength is the biggest challenge in such materials. Generally, ceramic – metal composites having high ceramic volume fraction are produced by infiltration of metal reinforcement into the partially sintered or pre – formed ceramic body. In this study, fine and coarse B4C powder compositions were prepared with both non-passivated and passivated powders at 1400 °C for 2 hours. B4C – Al ceramic – metal composites were produced by pressureless melt infiltration into partially Spark Plasma Sintered (SPS’d) B4C bodies. Microstructure and chemical analyses of B4C – Al ceramic – metal composites were correlated with passivation, ceramic and metal content, ceramic particle size and composition of the ceramic content. Results showed that passivation has positive effects on prevention of undesired reaction products.

In this paper, SiC particle reinforced Al based metal matrix composites were manufactured by powder metallurgy. Average particle sizes of Al matrix were 33 μm, 45 μm and 61 μm while dimension of SiC reinforcement were 33 μm and 61 μm. Prepared metal matrix composite specimens have 3%, 6% and 10% reinforcement. Prepared composites were sintered at 600oC. Specimens were then separated into three groups such as: not rolled after sintering, rolled after sintering, first sintered then heated to 500o C before rolling operation. After rolling of metal matrix composites, hardness and microstructure differences examined in hand. A description of the phenomena involved clustering of particles, particles cracking, interfacial failure associated with weak matrix-reinforcement bonding was presented. The effect of particle size, particle percent and rolling temperature on microstructure and hardness differences were investigated.

Polycrystalline zinc oxide (ZnO) thin films are deposited onto glass substrates, SnO2:F/glass and SnO2:F/Pyrex substrates by using chemical spray pyrolysis method from aqueous solutions of zinc acetate precursors at 440°C in air. Comparison of structural properties carried out for X-Ray Diffractometer (XRD). The results obtained in the evaluation of the optical behaviour of the films are reported and discussed. The dependence of structural, electrical and optical properties of ZnO on substrate was investigated.

Sr doped zinc oxide (ZnO) is deposited onto glass, SnO2:F/glass and SnO2:F/Pyrex substrates by using chemical spray pyrolysis method from aqueous solutions of zinc acetate and strontium chloride as precursors at 440A°C in air. A comparison of structural properties was carried out for X-Ray Diffractometer (XRD). Optical characteristics are measured using Xenon lamp as the excitation source. Microstructures of the surface deposited have the influence for a device performance and the optical properties are found to be influenced by the nature of the substrate.

We review the numerous static and dynamic studies on the polycrystalline and single-crystal specimens of B4C, address the important issues and discuss their implications in terms of the strain-induced changes in their crystallographic parameters and structure, transport properties and electronic structure. We will rely on an integrative analysis of the collaborative in-situ high-pressure studies involving synchrotron x-ray diffraction, ultrasonics, Raman and Brillouin scattering and electrical resistivity in diamond-anvil cell, in conjunction with theory.
Specifically, synchrotron X-ray diffraction (XRD) and Raman spectroscopy measurements have been carried out on polycrystalline B4C and single-crystal (nearly stoichiometric) in a diamond-anvil cell to 70 GPa. These results, in conjunction with high-pressure ultrasonic, Brillouin measurements, are compared with shock wave data in order to understand the compression behavior, establish the equations of state and explain the observed poor ballistic performance.
Whereas the powder XRD data indicate no easily detectable discontinuous changes within the studied pressure range, the Raman spectroscopy, electrical conductivity measurements and shock wave data suggest a more complex behavior. Motivated by this discrepancy, a detailed strain/stress analysis based on the peak profile broadening was performed, revealing two regions of discontinuous strain change, which cannot be explained by the transformations of pressure transmitting medium. These changes can be tentatively related with electronic transformations and changes in bonding. Preliminary results from the electrical resistivity and optical measurements support this interpretation.

We review the numerous static and dynamic studies on the polycrystalline and single-crystal specimens of B4C, address the important issues and discuss their implications in terms of the strain-induced changes in their crystallographic parameters and structure, transport properties and electronic structure. We will rely on an integrative analysis of the collaborative in-situ high-pressure studies involving synchrotron x-ray diffraction, ultrasonics, Raman and Brillouin scattering and electrical resistivity in diamond-anvil cell, in conjunction with theory.
Specifically, synchrotron X-ray diffraction (XRD) and Raman spectroscopy measurements have been carried out on polycrystalline B4C and single-crystal (nearly stoichiometric) in a diamond-anvil cell to 70 GPa. These results, in conjunction with high-pressure ultrasonic, Brillouin measurements, are compared with shock wave data in order to understand the compression behavior, establish the equations of state and explain the observed poor ballistic performance.
Whereas the powder XRD data indicate no easily detectable discontinuous changes within the studied pressure range, the Raman spectroscopy, electrical conductivity measurements and shock wave data suggest a more complex behavior. Motivated by this discrepancy, a detailed strain/stress analysis based on the peak profile broadening was performed, revealing two regions of discontinuous strain change, which cannot be explained by the transformations of pressure transmitting medium. These changes can be tentatively related with electronic transformations and changes in bonding. Preliminary results from the electrical resistivity and optical measurements support this interpretation.

The effects of coating thickness on the cyclic performance of Sn-Ni/MWCNT nanocomposite electrodes were investigated in this study. Nanocrystalline Sn-Ni/MWCNT composite was prepared by ultrasonic-pulse electrodeposition on a copper substrate in a pyrophosphate bath. Sn-Ni/MWCNT composites were characterized by scanning electron microscopy (SEM). X-ray diffraction analysis was carried out to investigate structure of Sn-Ni/MWCNT composites. Cyclic voltammetry (CV) tests were performed to reveal the reversible reactions of nickel-tin with lithium. The electrochemical performances of Sn-Ni/MWCNT composite electrodes have been investigated by charge/discharge tests, cyclic voltammetric experiments and the ac impedance technique. These cells discharge capacity cyclically tested by a battery tester at a constant current in voltage range between 0.02 V – 1.5 V. The thickness of composite coatings was shown to be a crucial factor to improve Sn-Ni /MWCNT composite anodes for cyclability and reversible capacity.

In this study, the multi-step design of nano Sn-Cu-C core–shell composite for high stability and long life lithium ion battery electrodes has been introduced. The core–shell Sn-Cu composite was successfully synthesized via electroless copper coating and subsequently a thin carbon layer was coated on the surface of Sn-Cu core-shell structure by microwave hydrothermally synthesis method. The surface morphology of the produced core-shell Sn-Cu-C composite powders was characterized using transmission electron microscopy (TEM). X-ray diffraction (XRD) analysis was applied to investigate the structure of the Sn-Cu-C composite powders. The electrochemical performances of the electrodes have been investigated in the voltage range of 0V to 2.0 V at the constant current of 200 mA g-1. Eventually, the produced carbon coated Sn-Cu core-shell composite electrode showed 451 mAh/g discharge capacity after 30 cycles due to buffering effect of copper and thin carbon layer on the surface of tin powders.

Compounds containing planar boron sheets are of current interest because of the important role of such sheets in the superconducting behavior of MgB2. Among them, solid state ternary borides of stoichiometry REMB4 such as YCrB4 (RE = rare earth metal and M = transition metal or heavy main group atom) exhibit infinite two-dimensional layers of boron atoms with topologies different from that encountered in MgB2. Parameters such as the symmetry, the electron count and the nature of the RE and M elements will be analyzed with the aid of density-functional band structure calculations to address the issues of structural arrangement and some physical properties, in particular thermoelectrical properties.

Compounds containing planar boron sheets are of current interest because of the important role of such sheets in the superconducting behavior of MgB2. Among them, solid state ternary borides of stoichiometry REMB4 such as YCrB4 (RE = rare earth metal and M = transition metal or heavy main group atom) exhibit infinite two-dimensional layers of boron atoms with topologies different from that encountered in MgB2. Parameters such as the symmetry, the electron count and the nature of the RE and M elements will be analyzed with the aid of density-functional band structure calculations to address the issues of structural arrangement and some physical properties, in particular thermoelectrical properties.

Fabrications of 2D, 3D, 4D or randomly distributed carbon fiber reinforced carbon matrix, C/C ceramics, composites exhibiting high thermal and stable mechanical properties at high temperature have been extensively studied for few decades. The viscous resin or powder mixture, which are already determined, can be used for the matrix material and the particular fiber arrangement such as 2D, 3D etc. could be formed. The mixtures of fiber and matrix can be carburized directly at certain temperature, or pre-form can be formed before carburization under the proper pressure or into some casting mold according to solid or liquid matrix materials. However, carbonization process should be carried out in controlled atmosphere which could be argon, nitrogen or vacuum environment, since carbon has poor exudation resistance during the carburization heat treatment. In this study, the solid preform, which is made up of randomly distributed carbon fiber, carbon black, phenolic resin and binder, has been formed under moderate pressure and temperature. 150-300oC of the temperature ranges are studied for preforming. The preform product obtained has carburized in the solid atmosphere instead of the gas flow controlled atmosphere or vacuum environment which is commonly preferred ones. The method using solid inert atmosphere during carburization step in open air furnace is the unique part of the study which is totally different than the conventionally known methods requiring controlled gas atmosphere or vacuum systems. In this scope, the pre-formed semi-product which has formed at warm temperature, 150-300oC, with moderate pressure is subjected to the carburization process in the created solid inert environment in open air furnace at 5 oC/min heating rate and 1100-1150oC carburization temperature. The semi-preform product consists of mixture of solid carbon powder and carbon fiber in 20, 25, 30, 35, 40 percent. 30–35% porosity occurs in carburized products following the pyrolysis process in which solid activated carbon inert bath is used. 5-10 cycles of impregnation processes have been applied by using a solution of furfuryl alcohol and tartaric acid. The carburization process with 5oC/min heating rate at 1100 oC for 20 hours duration has been repeated after each impregnation cycles. The density and porosity changes are measured according to the ASTM C20 following the impregnation. EDX and SEM examinations are performed on the produced carbon-carbon composite structure samples for microstructural analysis.

Unique physicomechanical properties of boron carbide provided efficient application of this material to the different areas of contemporary mechanical engineering, nuclear energy, precise machinery, etc. However, toughness and low crack resistance of the boron carbide product make obstacles to its widespread application. Resources of further improvement of the properties of this material by traditional methods have practically been expired. A way toward solving these problems is creating nano-sized systems where particle size is less than 50-100 nm. Nano-sized particles qualitatively differ from those of micron size. This difference is provided by drastic impact of the increasing surface layer on a free energetic balance of the system. Such systems reveal new opportunities for improving physical, mechanical, tribotechnical and other properties.
The present paper deals with the development of a technology for producing boron carbide powder in nano-crystalline state. The technology provides the powder fabrication via interaction of different types of organic compounds and boric acid at relatively low temperatures (1200 - 13000C). The materials selection for the synthesis of boron-containing polymer precursors is performed basing on the following polymers: polyvinyl alcohol, phenol formaldehyde resins, citric acid, sucrose, etc. The prepared precursor is subjected to pyrolysis in inert or hydrogen atmosphere at 600-10000C with subsequent thermal treatment at 1200 - 13000C in a regulated temperature mode. XRD, SEM, etc. analyses show that the resulting product is nano-crystalline boron carbide powder.

Dense and porous mullite ceramics have a long tradition as an important material both in traditional and advanced ceramic applications. Porous mullite ceramics exhibit an excellent combination of good thermal-shock resistance and low thermal expansion coefficient as well as high mechanical and chemical stability at elevated temperatures. Mullite ceramics can be produced via various different approaches; however, among the available approaches, fabrication of mullite ceramics by using kaolin as starting material is an important one due to its economic potential. In the current study, hierarchical porous mullite ceramics were produced via polymeric sponge method by using kaolin as starting raw material. Polyurethane sponges with a different number of pores per inch were physically joined together to produce an open porosity gradient in the structure layer by layer. Phase composition and microstructure evolution of the porous samples were investigated as a function of sintering temperature and soaking time at a constant heating rate.

Polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure polycrystalline BN have been tested as thermal neutron converters in a multilayer neutron detector design. Metal sheet electrodes were covered with 20 to 50 microns thick layers of composite material and assembled in a multi-layer sandwich configuration. High voltage was applied to the metal electrodes to create an interspacing electric field. The spacing volume could be filled with air, nitrogen or argon. Thermal neutrons were captured in converter layers due to the presence of the 10B isotope. The resulting nuclear reaction produced alpha-particles and 7Li ions which ionized the gas in the spacing volume. Electron-ion pairs were collected by the field to create an electrical signal proportional to the intensity of the neutron source. The detection efficiency of the multilayer neutron detectors is found to increase with the number of active converter layers. Pixel structures of such neutron detectors necessary for imaging applications and incorporation of internal moderator materials for field measurements of fast neutron flux intensities are discussed as well.

Non-oxide ceramics provide better mechanical and thermal properties compared to their oxide counterparts. On the other side, special sintering conditions such as high temperature, protective atmosphere and sometimes application of an external pressure are necessary to obtain flaw-free non-oxide ceramics and this limits processing and further application of these ceramics. To ease these limitations, studies have been carried out to lower sintering temperature under atmospheric conditions.
In this study, sodium borate was used to lower the sintering temperature. SiC-Si3N4 mixtures were prepared with various amounts of sodium borate and SiC-Si3N4 for TG-DSC analysis. TG-DSC analyses were performed up to 1200oC by using two different heating rate, 5 and 20oC/min. Also, TG-DSC analyses were applied for pure Si3N4, SiC and Si3N4-SiC mixtures for reliable comparison. While oxidation for pure mixtures were started above 1000oC, addition of sodium borate decreases the oxidation temperature to 800oC. The weight gain changed approximately 4 wt% for pure mixtures and this value increased to 10 wt% for mixtures that contain sodium borate. XRD studies revealed that mixtures with sodium borate had cristobalite as a major phase.

Additional coauthors (without e-mail address: Stefan Hoffmann; Guido Gerlach)<br />A recent theoretical structure model of carbon-rich boron carbide (Yaoa et al.) assumes a continuous phase transition accompanied by loss of inversion symmetry near 790K and a first-order transition at 717 K, breaking the 3-fold rotational symmetry. We checked this model by experiment, performing DSC measurements on single crystal B4.3C. A clear anomaly at 712 K, close to the theoretically predicted phase transition, has exothermic character, opposite to the endothermic one predicted. Phonon splitting between 700 and 800 K indicates structural changes. The IR-active vibration of the bending mode of the C-B-C chains between 100 and 800 K shows additional anomalies between 400 and 500 K: the distribution of isotopes on the B(3) site changes drastically, accompanied by a considerable lattice softening.

Many researchers have made efforts to develop alternative electrode materials to replace the conventionally used graphite. Sn is one of the most attractive anode materials that can be used as an alternative to the graphite, owing to its high theoretical capacity of 991 mAhg&#8722;1. However, bulk tin anodes have exhibited poor cyclability due to crumbling under large volume expansion (up to about 300%) during Li ion insertion, which causes the pulverization and delamination of active materials from current collector during cycling.
In this study, it is aimed to produce pyramid like nanostructured tin anodes for li-ion batteries by pulse electrodeposition to improve electrochemical reaction and cycle life of the tin anodes. To provide pyramid like nanostructured tin anodes, different peak current densities were applied when the other electrodepostion conditions were kept constant (pulse Ton = 5 ms and Toff = 5 ms). The structure of the produced anodes were investigated using SEM, XRD and EDS. Electrochemical characterization of the anodes were performed from 0.02V to 1.5V at a constant current density in CR2016 test cell.

Low Temperature Cofired Ceramics (LTCC) such as zinc titanate with their low dielectric constant and low losses are receiving increasing attention in research community because of its application in novel multilayer communication modules involving the integration of passive components. However, zinc titanate is usually sintered at temperatures above 1100°C, which are higher than the melting temperatures of Ag (961°C) and Cu (1064°C) interconnects in multilayer devices. Therefore, sintering of zinc titanate ceramics at low temperatures becomes a requirement for usage in the devices. In the present experimental work, sintering of zinc titanate ceramics was carried out with combined additions of V2O5 and B2O3 in the range of 0.5 to 1 wt%. The individual oxide powders were mechanically milled, calcined before adding the sintering enhancers and further calcined before compacting. Sintering was carried out in air between 850 and 1100°C. The sintered samples were analyzed for their phase content, dielectric properties and sinterability. It was found that the zinc titanate ceramics with a maximum density of 4.75 g/cm3 at temperatures as low as 900°C with a dielectric constant of 18.5 and a reasonable Q x F of about 14000 GHz. The phase content of the ceramics showed small TiO2 but varied phases of zinc titanate depending on the sintering temperature.
Key Words: Zinc Titanate, V2O5, B2O3, Sintering, Dielectric Properties

Boron and boron-rich solids are distinguished by outstanding characteristics like extraordinary high melting points, great hardness, low density and high chemical stability. The neutron absorption cross section of the 10B isotope is very high. The complex icosahedral boron-rich structures vary from the boron allotrope alpa-rhombohedral boron with 12 atoms to YB66 type crystals with 1584 atoms per elementary cell, including boron carbide, the hitherto technically most important and one of the most intensively investigated boron compounds. All of them are essentially composed of nearly regular B12 icosahedra, sometimes containing one carbon atom substituting for boron, forming open networks with hollow spaces in between. These allow accommodating foreign atoms, thus offering a basis for tailoring the individual properties according to technical requirements. Fundamental discrepancies occurred between experimental results proving semiconducting behavior and theoretical calculations predicting metallic character. Reason is the not yet understood tendency of these structures to avoid metallic behavior by generating structural defects in required concentrations. These are high, sometimes in the order of 1 to 10 %, thus explaining that the theoretical calculations based on idealized undistorted structures necessarily failed. According to Ogitsu et al., the partial occupancies of specific regular sites in the beta-rhombohedral boron structure result from a geometrical frustration originating from the intrinsic instability of the B28 subunits. They can be described by an antiferromagnetic Ising model on an expanded Kagome lattice. The experimentally gained electronic band scheme contains numerous acceptor-like gap states and a series of electron traps determining essentially the electronic transport properties. Apart from high concentration of vacancies in the center site of the elementary cell, the structures of boron carbides in the entire homogeneity range (B4.3C to B~11C) consist of B12 and B11C icosahedra and CBC and CBB chains, whose shares depend on the actual chemical composition. As the differently composed elementary cells are statistically distributed, X-ray and neutron diffraction, averaging comparably large volumes, failed in determining the components quantitatively. NMR failed as well. However, phonon spectroscopy on isotope-enriched boron carbide proved suitable to solve this problem. The experimentally determined band scheme of boron carbide, describing the electronic properties consistently, contains high concentrations of various gap states, which are generated by the structural defects. These gap states are responsible for the complex electronic properties.

Boron and boron-rich solids are distinguished by outstanding characteristics like extraordinary high melting points, great hardness, low density and high chemical stability. The neutron absorption cross section of the 10B isotope is very high. The complex icosahedral boron-rich structures vary from the boron allotrope alpa-rhombohedral boron with 12 atoms to YB66 type crystals with 1584 atoms per elementary cell, including boron carbide, the hitherto technically most important and one of the most intensively investigated boron compounds. All of them are essentially composed of nearly regular B12 icosahedra, sometimes containing one carbon atom substituting for boron, forming open networks with hollow spaces in between. These allow accommodating foreign atoms, thus offering a basis for tailoring the individual properties according to technical requirements. Fundamental discrepancies occurred between experimental results proving semiconducting behavior and theoretical calculations predicting metallic character. Reason is the not yet understood tendency of these structures to avoid metallic behavior by generating structural defects in required concentrations. These are high, sometimes in the order of 1 to 10 %, thus explaining that the theoretical calculations based on idealized undistorted structures necessarily failed. According to Ogitsu et al., the partial occupancies of specific regular sites in the beta-rhombohedral boron structure result from a geometrical frustration originating from the intrinsic instability of the B28 subunits. They can be described by an antiferromagnetic Ising model on an expanded Kagome lattice. The experimentally gained electronic band scheme contains numerous acceptor-like gap states and a series of electron traps determining essentially the electronic transport properties. Apart from high concentration of vacancies in the center site of the elementary cell, the structures of boron carbides in the entire homogeneity range (B4.3C to B~11C) consist of B12 and B11C icosahedra and CBC and CBB chains, whose shares depend on the actual chemical composition. As the differently composed elementary cells are statistically distributed, X-ray and neutron diffraction, averaging comparably large volumes, failed in determining the components quantitatively. NMR failed as well. However, phonon spectroscopy on isotope-enriched boron carbide proved suitable to solve this problem. The experimentally determined band scheme of boron carbide, describing the electronic properties consistently, contains high concentrations of various gap states, which are generated by the structural defects. These gap states are responsible for the complex electronic properties.

In view of the worldwide increasingly growing budget restrictions and the profuse concerns on the environment, it is imperative to carry out the modification or development of new materials and/or processes in an optimized way by proper use of the modified central paradigm of materials science and engineering, proposed previously by the authors. On the basis of two previous publications on the subject, the authors suggest that positive results can be observed at massive or commercial scale, only if the sustainable development or modification of processes and/or materials starts at lab level, in the research centers or universities with a proper education strategy. The Modified Central Paradigm of Materials Science and Engineering - depicted by the relationship "Processing, Structure, Property, Performance, Reutilization/Recyclability" considers, from the outset, the sustainability, pollution, reutilization and recycling aspects. The modified paradigm implicitly embodies the environmental and economic aspects, emphasizing the saving in the use of energy, chemical reactants, water and consumables. It is also based in a synergistic approach that encourages scientists to work hand-in-hand with other researchers by using by-products or residues from other investigations or by offering the ones generated in the lab. This requires another essential feature; namely, the use of creativity and innovation that implicitly triggers competitiveness. In this contribution, specific action steps are proposed to work under the modified paradigm, particularly at laboratory level.

Boron carbide (B4C) is the third hardest material at room temperature, surpassing even diamond and cubic boron nitride at temperatures over 1100 °C. It has many other attractive properties such as good wear resistance, high modulus, high chemical and thermal stability. These properties make boron carbide a promising candidate as hard and protective coatings for cutting tools, automobile parts, hard disk drives and other wear–resistance applications. Despite of these significant properties, boron carbide has not been investigated extensively in thin film form. In this study, we present our results on the deposition of boron carbide thin films by focusing on the micro/nanostructural properties of the coatings obtained. Boron carbide thin films were deposited by DC magnetron sputtering of a B4C target on Si (100) and steel substrates. Nanostructural observations conducted by TEM, HRTEM and EFTEM showed that columnar morphologies of B4C films deposited without heating and at floating potential formed by 20-25 nm thick single columns and 2-3 nm thick nano-voids at the column boundaries where impurity oxygen was present. Microstructural analyses realized by FE-SEM demonstrated the densification and the transition from columnar to non-columnar, featureless morphologies of the coatings with the increase in the bias voltages and temperature. Chemical analyses realized by EPMA demonstrated that films with columnar structures had excess amount of impurity oxygen in their composition. Boron carbide films obtained were amorphous according to FFT patterns. Hardness of films obtained from nanoindentation studies increased from 20±2 GPa to 40±2 GPa with the increase in the bias voltages and temperature, demonstrating that ultrahard boron carbide films with superior mechanical properties can be obtained by DC magnetron sputtering.

Structural similarity of graphitic carbon and hexagonal BN (h-BN) initiated the intensive studies of BN nanostructures. However, the ionic origin of BN leads to electronic structure and properties of BN structures that significantly differ from that of carbon nanostructures. Therefore, the goal of this work is to synthesize and research the properties of boron nitride powders and BN powders with additives (Ta, Si, In, C, Ni) produced under effect of concentrated light in a flow of nitrogen in a xenon high-flux optical furnace. Scanning and transmission electron and optical microscopes demonstrated structures of new morphologies for the powders, which were formed. X-ray Diffraction study, Raman scattering, Fourier transform infrared (FT-IR) spectroscopy and electron diffraction study have confirmed a complicated structure and phase composition of the powders with a prevalence of the amorphous phases. The study of optical properties was carried out on spectrophotometer. It was demonstrated an effect of experimental conditions, surface modification and additives on phase composition, optical properties, morphology and structure formation. The gaseous model based on an evolution of the bubble was proposed for explanation of nanotubes formation. Burst of these bubbles may result in graphene-like structures formation.
Keywords: Light heating, Nanostructures

Composite electrodeposition is a method including co-deposition of metal, non-metal or polymeric fine particles. During the process, insoluble reinforcements are suspended as colloidal in a traditional coating electrolyte and forced into growing metal film. The second phase may be particle, fiber or nonstructured materials such as fullerene, nanotubes, graphene. Second phase particles in the coating generally result in increasing microhardness, yield stress, tensile stress and wear resistance.
There are several methods to produce particle reinforced metal matrix composites. In recent years, electro co-deposition of particle reinforced metal matrix composites attracted much interest since it is easy applicable and its scale-up method includes both accumulated micron/nano sized polymeric and metallic/non-metallic particles in a metal/alloy matrix.
In this study, Ni/SiO2 and Ni/Al2O3 composite coatings are produced by using pulse current electrodeposition technique. Microhardness, wear resistance and wetting properties of composite coatings were examined when comparing pure metallic nickel coating. Both composite coatings showed higher microhardness and wear resistance than the pure nickel coating. The wetting angle of the pure nickel coating also increased by ceramic reinforcements. Particle sizes of ceramic powders are 80 to 100 nm, respectively. Adding the finer nano-particles into the composites increased the hardness values of pure nickel coatings. The presence of 2-3 wt % Al2O3 or 0.8 to 1.2 wt% SiO2 in the composite coating resulted in nearly two-times increment of hardness of pure nickel coating. Despite friction coefficient of alumina powders, reinforced Ni-Al2O3 composite is increased and the friction ratio of the coating is decreased regarding to the metallic nickel coating. The lowest friction coefficient and also wear ratio are obtained at the Ni/SiO2 composite. On the other hand, its wetting angle is found at the maximum value according to all coatings.

A fundamental theoretical problem for boron solids is that many structures are predicted to be metals, while experimentally all are insulators. This fundamental problem has been recently solved by the present authors. The problem is intimately related to a distinct property of the boron crystals, namely breaking of stoichiometry. By using this view, the authors have solved a longstanding problem of defects in boron carbide. The second material for testing our view is I±-tetragonal boron, which has also a historical problem as to whether pure structure exists or not. Recent experiments of high-pressure synthesis suggest the existence of pure structure. Our calculations attempt to describe under which conditions the pure structure becomes stable.

At the contemporary stage of the development of industry, there are widely used nanostructural composite materials. In particular, the materials containing metal carbides and metal borides should be noted. That is why the technologies for fabricating these materials by chemical methods, e.g. by the reduction processes require provision of large-scale theoretical and experimental studies.
Recent years have been marked by an intense development of studies of chemical and phase equilibria in multicomponent and multiphase systems by using the methods of computer simulation. This approach applied to the processes of fabricating composite and nanostructural materials is of great interest.
It should be noted that the method of Full Thermodynamic Analysis (FTA) used in the present work gives an opportunity to consider not only the equilibrium conditions occurring in the system processes, but also the mechanisms of interaction of components in complex systems and to regulate the composition of final product as well.
The aim of the present work was to provide thermodynamic analysis of the titanium carbide and titanium boride process of formation and on the basis of this analysis to carry out experiments for fabricating nanostructural composite materials.
The innovation of the work was the study of physical and chemical basics of high-temperature processes for producing carbides and borides of the specified systems, the study being a precondition to minimizing the number of experiments.
PTA of carbothermal reduction of the oxides of TiO2 and B2O3 of different composition was performed at high temperatures in vacuum resulting in the formation of titanium carbides and borides:
TiO2 - x mass %; B2O3 - y mass %; C - [100-(x+y) mass %]
There were not found any data on PTA of the considered system in the available literature. Therefore PTA performance on the specified system was of a great interest. Estimations were carried out on the COMPUTER applying the ASTRA 4 program in the range of temperatures 500-2000 K with the step of 500 in vacuum. The obtained results were presented in the form of charts (temperature dependent components).
The results of estimations were used in the provided experiments and pilot samples of composite materials were prepared.

Due to the unique bonding properties, sometime described by the location in the periodic table, elemental boron and boron compound exhibit unique structural, electronic and optical properties. Although their unique properties could be a great advantage in the development of novel functional materials, the complexity of boron chemistry has rather been a challenge for such attempt. Nevertheless, recent advancement in both computational approaches and experimental characterization techniques has contributed significantly to our understanding of these materials.
At the presentation, we will first review the progresses in understanding the boron allotropy where theoretical studies using high performance computing have provided very important insights as to how unique boron chemistry lead to the peculiar enthalpic stabilization via introduction of macroscopic amount of disordered defects in I²-rhombohedral boron. These recent theoretical studies also provided explanations for many unusual behaviors of boron allotropes reported over several decades, leading to more comprehensive understanding of elemental boron. For example, it is now suggested that another allotrope boron, T-phase, might also be stabilized by defects, without which, observation of T-50 phase could be rationalized as a thermodynamically stable phase.
Boron compounds are also known to exhibit unique and complex properties inheriting the complex boron chemistry. For example, it has been known that boron carbide, known as a lightweight superhard material, exhibit unique mechanical properties such as too low Hugoniot elastic limit compared to the predicted value from its hardness. We will discuss the thermodynamic stability of boron compounds and possible role of kinetics that might be relevant in precise understanding of mechanical properties of boron carbide.
We hope that further development of accurate and comprehensive picture on the properties of boron and its compound will lead to rational design of novel functional materials that serve our future.
The work performed under the auspices of the U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344

Due to the unique bonding properties, sometime described by the location in the periodic table, elemental boron and boron compound exhibit unique structural, electronic and optical properties. Although their unique properties could be a great advantage in the development of novel functional materials, the complexity of boron chemistry has rather been a challenge for such attempt. Nevertheless, recent advancement in both computational approaches and experimental characterization techniques has contributed significantly to our understanding of these materials.
At the presentation, we will first review the progresses in understanding the boron allotropy where theoretical studies using high performance computing have provided very important insights as to how unique boron chemistry lead to the peculiar enthalpic stabilization via introduction of macroscopic amount of disordered defects in I²-rhombohedral boron. These recent theoretical studies also provided explanations for many unusual behaviors of boron allotropes reported over several decades, leading to more comprehensive understanding of elemental boron. For example, it is now suggested that another allotrope boron, T-phase, might also be stabilized by defects, without which, observation of T-50 phase could be rationalized as a thermodynamically stable phase.
Boron compounds are also known to exhibit unique and complex properties inheriting the complex boron chemistry. For example, it has been known that boron carbide, known as a lightweight superhard material, exhibit unique mechanical properties such as too low Hugoniot elastic limit compared to the predicted value from its hardness. We will discuss the thermodynamic stability of boron compounds and possible role of kinetics that might be relevant in precise understanding of mechanical properties of boron carbide.
We hope that further development of accurate and comprehensive picture on the properties of boron and its compound will lead to rational design of novel functional materials that serve our future.
The work performed under the auspices of the U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344

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