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The paper presents a low-temperature method for the synthesis of tungsten boride containing ultra-fine powders of boron carbide matrix ceramics constituting an important class of superhard materials with diversity of industrial applications. Wet chemical method was used to prepare preceramic precursors. The technique provides annealing of a viscous paste of the mixture of ammonium paratungstate–zirconium(IV) oxide–cobalt acetate tetrahydrate–sucrose–amorphous boron at 200 °C in air and then at 600 °C in argon atmosphere for 2 h with the further grinding and additional annealing of the obtained powders at 800–1500 °C. Hot pressing of the complex ceramic powders at 1000–1700 °C was realized by using the SPS method. It was established that at 600 °C there were formed WO3–x, Co3O4, CoO, and amorphous carbon. The XRD data confirmed low temperature (800–1000 °C) formation of WC–Co, ZrB2, B4C, and W2B5. Tungsten carbide was completely converted into tungsten boride. Structural-morphological characteristics of the obtained samples were studied by using the SEM.

In this paper, graphene oxide (GO) was obtained by oxidation of powdered graphite foil wastes (pGFW) at 0 - 40°C. Oxidizing reagents can easily penetrate the layers of graphite foil and thus, the intercalation or functionalization-oxidation processes may occur resulting in graphite oxide formation. The methods of synthesis of GO and its separation from the reaction mixture were partially corrected. GO was reduced, also, to the reduced graphene oxide (rGO) by using hydroiodic acid, ascorbic acid, zinc powder, hydrazine, and Alnus extract. Thermal treatment of GO powders and GO films, obtained from pGFW was implemented at 20-300° C in air and at 20-1000° C under argon flow and in a vacuum. At high-temperature treatment (1000°C) of GO graphene was obtained with a defective structure.

The results of the study of the production technology, phase composition, structure and physico-mechanical properties of metal-ceramic materials based on boron carbide and their components are pres...

Nanocomposites based on boron carbide B4C are hard materials with wide field of applications in modern technologies. A system of first-order ordinary differential equations that simulates the process of chemical synthesis of nanopowders of B4C&ndash, TiB2 compositions containing titanium diboride (TiB2) as an additional phase is suggested and resolved numerically for a typical ratio of reaction constants. Reagents and products concentrations are found as time-functions. In this way, the optimal route of production technology of boron carbide-based nanomaterials can be identified.

This study reports the role of graphene in improving the mechanical and electrical properties of TiO2/graphene nanoplatelets (GNPs) composite. Graphene oxide (GO), as a precursor was used with varying concentrations of 0, 0.5, 1, and 2 wt%. The GO was being reduced simultaneously with the TiO2 matrix, providing uniform distribution of rGO nanoplatelets among the matrix particles. Spark plasma sintering technique (SPS) was used for sintering initial powder of the TiO2/rGO composite. Alongside the sintering of the powder, SPS induces rGO transformation to graphene nanoplatelets at high temperatures and provides the densification of TiO2/GNPs as a final composition. Morphology and microstructure of prepared samples were characterized by XRD and SEM. Density and microstructural studies were used to determine the sintering quality and compared to the theoretical density of TiO2 and TiO2/GNPs composites. Vickers microhardness method was used to calculate hardness and fracture toughness depending on the crack propagation alongside the indentations. The two-probe method was applied to study the electrical conductivity by resistance measurement. The results indicated that there was a significant change in the structural and physical properties of TiO2/GNPs composites. The rGO takes an important role as a grain growth inhibitor, acting as the barrier for crack propagation and leading to increased fracture toughness. Thus, GNPs can be considered as a good reinforcement for titanium dioxide ceramic in order to improve the material's brittleness and electrical conductivity without adversely affecting its microhardness.

Fine-grained boron carbide and metal boride composites are known for their superhardness, which is used in many industrial technologies. The introduction of binder components in free metallic (alloy) state and/or additional ceramic components can further improve the material mechanical properties by making it more dispersive. A new chemical method is proposed for the synthesis of the fine-grained powder complex composites boron carbide–titanium diboride–tungsten boride–cobalt (B4C–TiB2–WC–Co).

According to our studies of polarization-sensitive materials based on azochromophores and polymers in recent years, a factor significantly influencing their photoanisotropic properties has been revealed. The degree of molecular integration of the material components (light-absorbing centers and polymer matrix) is in direct connection with the level of achievable birefringence in media obtained on their basis. This paper considers the results of a study of the integration of polarization-sensitive materials by means of molecular electrostatic forces. Experimental data of the photoanisotropic behavior of optical media based on advisedly designed organic chromophore salts with the participation of almost all alkali metals are shown. Lithium (Li⁺), sodium (Na⁺), potassium (K⁺), cesium (Cs⁺) and hydrogen (H⁺) are used as cations for these polarized light-receiver organic salts, and as an anion, on the other hand, is a residue of functional monoazo dye. The obtained light-absorbing organic salts are doped into the hydrophilic polymer matrix having good lyophilic compatibility. To study the induction of photoanisotropy in the obtained photosensitive materials, we investigate the effect of actinic polarized light on them with wavelengths of 445 nm and 532 nm and variation of reading wavelengths (at 532 nm and 635 nm) depending on the spectral characteristics of the test samples. Optimum parameters of exposure for each composition are determined experimentally. The kinetic curves of the induction of photoanisotropy in the new comparing polarization-sensitive media are shown as light-induced effective photoanisotropy for the various illumination conditions.

The developed nanotechnology makes it possible to prepare lots of standard powders of Aluminates such as lutetium and yttrium orthorombic LuAlO 3 , YAlO 3 (LuAP, YAP – perovskite), aluminum garnets Lu 3 Al 5 O 12 , Y 3 Al 5 O 12 (LuAG, YAG) with cubic structure and aluminates with monoclinic structure Lu 4 Al 2 O 9 , Y 4 Al 2 O 9, (LuAM, YAM). Powders of scintillation materials are prepared by sol-gel method, co-precipitation method and a combination of sol-gel method with combustion reactions. Crystallization process of LuAG phase starts at 900 °C. At lower temperatures, during the pyrolysis of the gel, amorphous powders have been produced. After pyrolysis of the gels without additives of aminoacetic acid a mixture of LuAG+Lu 2 O 3 has been formed instead of LuAP. New phase of LuAP in a cubic form is detected. Diffraction peak profile analyzes and scanning electron microscope (SEM) investigations are performed to approximately establish grain size of the obtained powder. Thermogravimetry analysis (TGA) was carried out for detection of thermal effects in the range up to sintering temperature. Perovskite phases of aluminates have been synthesized via pyrolysis (at

In this work, obtaining methods of ultrafine alumina powdery composites and high temperature pressing technology of matrix ceramic composites with different compositions have been discussed. Alumina was obtained by solution combustion synthesis and sol-gel methods. Metal carbides containing powdery composites were obtained by homogenization of finishing powders in nanomills, as well as by their single-step high temperature synthesis .Different types of matrix ceramics composites (α-Al2O3-ZrO2-Y2O3, α-Al2O3- Y2O3-MgO, α-Al2O3-SiC-Y2O3, α-Al2O3-WC-Co-Y2O3, α-Al2O3- B4C-Y2O3, α-Al2O3- B4C-TiB2 etc.) were obtained by using OXYGON furnace. Consolidation of powders were carried out at 1550- 1750°C (hold time - 1 h, pressure - 50 MPa). Corundum ceramics samples have been obtained and characterized by high hardness and fracture toughness, absence of open porosity, high corrosion resistance. Their density reaches 99.5-99.6% TD. During the work, the following devices have been used: High temperature vacuum furnace OXY-GON Industries Inc (USA), Electronic Scanning Microscopes Nikon Eclipse LV 150, Optical Microscope NMM- 800TRF, Planetary mill Pulverisette 7 premium line, Shimadzu Dynamic Ultra Micro Hardness Tester DUH-211S, Analysette 12 Dynasizer., {"references":["A. Kmallik, S. Gangadharan, S. Dutta and D. Basu. Micrometer size\ngrains of hot isostatically pressed alumina and its characterization, Bull.\nMater. Sci., 2010, 33(4), 445–449.","V. Lysenko, V. Mali, A. Anisimov. Microhardness of Ceramics\nObtained by Different Methods from Nanopowders of Different Oxides,\nAthens J. of Sciences, 2014, 269-279.","H. Antonio, D. Aza, J. Chevalier, F. Gilbert. Slow-crack-growth\nbehavior of zirconia-toughened alumina ceramics processed by different\nmethods. J. Am. Ceram. Soc., 2003, 86(1), 115-120.","Chih-Jen Wang, Chi-Yuen Huang, Yu-Chun Wu. Two-step sintering of\nfine Alumina-zirconia ceramics. 2008, Available online at www.\nsciencedirect.com.","M. Zakeri, M. R. Rahimipour. Effect of cup and ball types on mechanochemical\nsynthesis of Al2O3-TiC nanocomposite powder. Ceramics–\nSilikaty, 2012, 56(2), 130-134.","V. Naglieri, P. Palmero, L. Montanaro, J. Chvalier. Elaboratorion of\nAlumina –Zirconia composites: Role of the Zirconia Content on the\nMicrostructure and Mechanical Properties. Materials, 2013, 6, 2090-\n2102.","M. Vlasova, N. Kakazey, I. Rosales and al., Synthesis of Composite\nAlN-AlON-Al2O3 powders and ceramics prepared by High-pressure\nsintering. Science of Sintering, 2010, 42, 283-295.","US 8030234 B2, 2011. Aluminum boron carbide composite and method\nto form said composite.","Lu Shen, Chunfeng Hu, Yoshio Sakka and Qing Huang. Study of phase\ntransformation behaviour of alumina through precipitation method. J.\nPhys. D: Appl. Phys, 2012, 45, 215302(6pp). doi:10.1088/0022-\n3727/45/21/215302.\n[10] T. Kuchikhidze, N. Jalagonia, Z. Phachulia, R. Chedia. Transformation\nof Aluminum Oxyhydroxides in α-Al2O3 in Presence of Various Seeds.\nInternational Science Index (ICEMA) 2015, 17, 1303-1307.\n[11] N. Jalabadze, R. Chedia, T. Kukava, L. Nadaraia, L. Khundadze.\nDevelopment of new high performance nanocrystalline hard metals.\nNanotech., 2008, 1, 213-216.\n[12] Jalabadze Nikoloz, Mikeladze Archil and Chedia Roin. New Technology\nfor the Manufacturing of Nanocrystalline Materials. Second IEEE\nConference on Nanotechnology - IEEE-NANO' 2002, August 26-28,\n2002, Washington DC, USA.\n[13] N. Jalabadze, A. Mikeladze, R. Chedia, T. Kukava, L. Nadaraia and L.\nKhundadze. Development of New High Performance Nanocrystalline\nHard Metals. Nanotech., 2008. NSTI Nanotechnolgy Conference and\nTrade Show. June 1-5, 2008, Boston, MA, USA. V.1, p. 297-300.\n[14] Nikoloz V.Jalabadze, Roin Chedia, Tengiz Kukava and Lili Nadaraia.\nDevelopment of New Technologies for the Manufacturing of\nNanocrystalline Scintillation Materials. IEEE Transactions on Nuclear\nScience. 2008, 55(3), 1514 – 1522."]}

Boron carbide has unique physicochemical and mechanical properties such as: high modulus of elasticity, high value of a strength-to-density ratio, heightened wear-resistance in unfriendly environment, etc., however dense product of boron carbide is not widely used in the area of engineering due to low impact strength, brittleness and low thermal conductivity of this material. Recent efforts of the scientists working in this area are focused on creating the so-called hetero-modulus metal-ceramic composite materials comprised of high-modulus ceramic and a metallic phase as an elastic binder. Creation of effective boron carbide based hetero-modulus materials is possible when a) boron carbide has a high degree of dispersion; b) metallic binder has a high adhesion ability and low reactivity toward boron carbide. The technology developed for producing boron carbide based metal-ceramic materials provides pyrolysis (900–1100 °C) of the precursors comprised of amorphous boron, carbon-chain polymers and appropriate metal salts. Each particle of the obtained powder contains both – nanostructured components of boron carbide and of a binding metallic phase. The fabricated metal-ceramic product has heightened parameters of impact strength and thermal conductivity in parallel with the retained unique properties of boron carbide.

Thermal reaction of Au(PPh3)(C СC СFc) (Fc = ferrocenyl) with Re2(CO)8(NCMe)2 gives complexes Re2(AuPPh3)(μ-C4Fc)(CO)8 (4) and Re4(AuPPh3)(μ4-C2)(μ3-C2Fc)(NCMe)(CO)13 (5). Compounds 4 and 5 are characterized by 1H and 31P{1H} NMR, cyclic voltammetry and single crystal X-ray diffraction.

Tungstate crystals are considered high-class scintillators to be used as detector material for high-energy radiation. These crystals are frequently used as references in measurements on new luminescent materials. In this paper, we present manufacturing process of nanocrystalline tungstate materials. Lead tungstate (PbWO4), cadmium tungstate (CdWO4), calcium tungstate (CaWO4), and zinc tungstate (ZnWO4) were synthesized via modifying sol-gel process. An advantage of the developed technology is the possibility of manufacturing tungstate powders in nanocrystalline state not only at elevated temperatures but at room temperatures as well. X-ray diffraction method, scanning electron microscopy, and thermal investigations were done to establish structural and morphological state of these materials. For reaching the most dispersible with the lowest agglomeration single-phase system of tungstate materials, there was an established optimal relationship between the system of starting reagents and solvents.

Technology of producing single crystal scintillators is rather a hard and complex technological task connected with a very low output issue (15-50%) of the material and the restricted area of its application. Recent efforts of scientists are directed toward searching for alternative ways for producing these materials. It was established that high-performance ceramic scintillation materials for producing the scintillators could be prepared by using powder metallurgy techniques. However despite of certain achievements in this area, transparency of ceramic scintillators is still under the question. In our opinion a key to the solution of the problem lies in preparing scintillators in nanocrystalline structural state. A technology developed on the basis of the modified Sol-Gel method shows possibilities of manufacturing number of standard (as well as new hard to obtain as single crystals) scintillation materials. Present work is dedicated to the problems of manufacturing yttrium orthosilicate (Y2SiO5)-as of one of the perspective scintillation materials.

Single crystal scintillators are widely applied in many areas of science and technology. Production of single crystal scintillators is a rather complex, long-standing and power-intensive process. As an alternative to single crystals scintillation ceramic materials made of nanocrystalline powders were being considered. Sol-gel and co-precipitation methods have been used for establishing possibilities of fabricating rare earth metal ion-doped scintillators. By these methods, if modified, it is possible to regulate sizes of powder particles. Finely dispersed powders of single-phase lutetium silicates, titanates, aluminates, tungstates, molybdates and other materials were synthesized. Main goal of the present work was to study the influence of different factors on purity of LSO and LPS phases. Pyrolysis procedure of amorphous gels promoted formation of phase mixtures (LSO, LPS, Lu2O3 and SiO2) due to disturbance of the Lu:Si ratio under the influence of fluorine- and chlorine-containing compounds. Optimum modes for preparing nanophase powders of Ce3+-doped lutetium silicates (LSO, LPS) were defined. The synthesized samples were studied by using X-ray diffraction, electron microscopic and thermal analysis methods. LPS luminescence characteristics were established.

Ceramic obtained on the base of aluminum oxide has wide application range, because it has unique properties, for example, wear-resistance, dielectric characteristics, and exploitation ability at high temperatures and in corrosive atmosphere. Low temperature synthesis of α-Al2O3 is energo-economical process and it is topical for developing technologies of corundum ceramics fabrication. In the present work possibilities of low temperature transformation of oxyhydroxides in α-Al2O3, during the presence of small amount of rare–earth elements compounds (also Th, Re), have been discussed. Aluminum unstable oxyhydroxides have been obtained by hydrolysis of aluminium isopropoxide, nitrates, sulphate, and chloride in alkaline environment at 80-90ºC temperatures. β-Al(OH)3 has been received from aluminum powder by ultrasonic development. Drying of oxyhydroxide sol has been conducted with presence of various types seeds, which amount reaches 0,1-0,2% (mas). Neodymium, holmium, thorium, lanthanum, cerium, gadolinium, disprosium nitrates and rhenium carbonyls have been used as seeds and they have been added to the sol specimens in amount of 0.1-0.2% (mas) calculated on metals. Annealing of obtained gels is carried out at 70– 1100ºC for 2 hrs. The same specimen transforms in α-Al2O3 at 1100ºC. At this temperature in case of presence of lanthanum and gadolinium transformation takes place by 70-85%. In case of presence of thorium stabilization of γ-and θ-phases takes place. It is established, that thorium causes inhibition of α-phase generation at 1100ºC, and at the time when in all other doped specimens α-phase is generated at lower temperatures (1000-1050ºC). Synthesis of various type compounds and simultaneous consolidation has developed in the furnace of OXY-GON. Composite materials containing oxide and non-oxide components close to theoretical data have been obtained in this furnace respectively. During the work the following devices have been used: X-ray diffractometer DRON-3M (Cu-Kα, Ni filter, 2º/min), High temperature vacuum furnace OXY-GON, electronic scanning microscopes Nikon ECLIPSE LV 150, NMM-800TRF, planetary mill Pulverisette 7 premium line, SHIMADZU Dynamic Ultra Micro Hardness Tester, DUH-211S, Analysette 12 Dyna sizer., {"references":["H. Hou, Y. Xie, Q. Yang, Q. Guo, C. Tan. Perapration and\ncharacterization of γ-AlOOH nanotubes and nanorods. Nanotechnol.,\n2005, 16(6), 714-721.","Y. Xia, Y.Yang, P. Sun, Y. Wu, B. Mayers, A. Gates, Y.Yin, F. Kim, H.\nYan, Onedimensional nanostructures: Synthesis, characterization and\napplications. Adv. Mater., 2003, 15(5), 353-357.","G. L. Teoh, K. Y. Liew, W. A. K. Mahmood. Synthesis and\ncharacterization of sol–gel alumina nanofibers. J. Sol-Gel Sci. Technol.,\n2007, 44(3), 177-180.","M. G. Ma, J. F. Zhu. A Facile solvothermal route to synthesis of γ-\nalumina with bundle-like and flower-like morphologies. Mater. Let,\n2009, 63, 881-885.","Q. Yang, Y. Deng, W. Hu. Synthesis of alumina nanofibers by a\nmercury-mediated method. Ceram. Intern, 2009, 35(1), 531-537.","S. Cava, S.M. Tebcherani, I.A. Souza, S.A. Pianaro, C.A. Paskocimas,\nE. Longo, J.A. Varela. Structural characterization of phase transition of\nAl2O3 nanopowders obtained by polymeric precursor method. Materials\nChemistry and Physics, 2007, 103, 394–399.","A. Odaka, T. Yamaguchi, A. T. Fujita, B. S. Taruta, K. Kitajima.\nDensification of rare-earth (Lu, Gd, Nd)-doped alumina nanopowders\nobtained by a sol−gel route under seeding. Powder Technology, 2009,\n193(1), 26-31.","Yiguang Wang, C. Suryanarayana, Linan An. Phase Transformation in\nnanometer-sized χ-alumina by mechanical milling. J. Am. Cer. Soc.,\n2005, 88(3), 780-783.","Y. Yoshizawa, K. Hirao, S. Kanzaki. Fabrication of low cost finegrained\nalumina powders by seeding for high performance sintered\nbodies. Journal of the European Ceramic Society, 2013, 33(13–14),\n2365-2830.\n[10] R. L. Smith, G. S. Rohrer, A. J. Perrotta. The Influence of diaspore\nseeding and chloride concentration on the transformation of \"Diasporic\"\nprecursors to corundum. J. Am. Cer. Soc., 2001, 84(8), 1896-1902.\n[11] A. Sharma, O.P. Modi, G.K. Gupta. Combustion synthesis of\nnanocrystalline Al2O3 powder using aluminium nitrate and urea as\nreactants-influence of reactant composition. Advances in Applied\nScience Research, 2012, 3 (6), 3819-3824.\n[12] T.V. Kuchukhidxe, V.G. Gabunia, Z.V. Phachulia, N.T. Jalagonia, R.V.\nChedia. Some Issues of Ultrafine Alfa-alumina Powders Fabricated by\nLow Temperature Synthesis. 2014, 8, 303-312, ISSN 1314-7269,\nhttp://www.scientific-publications.net.\n[13] T.V. Kuchukhidze, N. T. Jalagonia, V. G. Gabunia, T. N. Archuadze, Q.\nG. Sarajishvili, R.V.Chedia. Influence of Some Metal Ions on Low\nTemperature Transformation of Alumina Metastable Oxides in\nα−Al2O3. 3th International Conference « Nanotechnologies» NANO-\n2014, 20-24 0ctomber, 2014, Tbilisi, Georgia."]}