In this article, we studied the influence of Mn2+ on the properties (on the phase composition, porosity, microstructure, three-point bending strength and microhardness) and sintering of the ZrO2 – Al2O3 – SiO2 composite ceramic materials. The ZrO2 – Al2O3 – SiO2 ceramic powder containing 2,5 wt.% Al2O3 and 0,5 wt.% SiO2 with 24,7 m2/g specific area was synthesized through co-precipitation method. Three concentrations of Mn2+ are considered: 0.25, 0.50 and 0.75 mol%. The introduction of Mn2+ leads to a significant increase in mechanical properties. The samples sintered at 1250 and 1300 °C for 2 hours. The highest value of strength at three-point bending 761 ± 36 MPa and microhardness 9.5 ± 0.5 GPa was characterized by the material of the composition ZrO2 – Al2O3 – SiO2 containing 0.75 mol.% Mn2+ sintered at 1300 °С. The crack resistance of this material was 7.0 MPa·m1/2. At the same time, the highest values of crack resistance 9.3 ± 0.5 MPa·m1/2 were shown by materials of the composition ZrO2 – Al2O3 – SiO2 containing 0.75 mol. % Mn2+ sintered at 1250 °C.

Abstract—The influence of various technological conditions of crystallization melting of corundum with cerium on its electrical conductivity and electroluminescence has been studied. The relation between the electrical conductivity of the samples and Ce4+ ions in the crystal lattice is discussed. The relation between electroluminescence of the samples and Ce3+ ions in electrically conducting samples is considered.

Effects of a liquid-phase sodium disilicate additive on the properties of ZrO2 ceramics containing 3 mol.% of Y2O3 and 2 wt% of Al2O3 are presented, including phase composition, microstructure, shrinkage, porosity, and bending strength. The distribution of elements along grain boundaries and the composition in a selected area of a lamella were investigated by transmission electron microscopy in pure and additive-containing samples. As a result of the introduction of the additive, sintering activity of the material increased, and the sintering temperature diminished down to 1150 degrees C. Thus, dense nanocrystalline materials with a crystallite size of 50-70 nm and a bending strength of up to 450 MPa were obtained. Optimized polymer-ceramic suspensions were used to produce objects with complex geometric shapes by 3D molding technology through layer-by-layer vat polymerization. According to in vitro assays, the obtained samples are nontoxic and cytocompatible with human osteosarcoma MG-63 cells, and according to in vivo experiments, are biocompatible and showing osseointegrative properties when implanted into the rat tibia.

The paper considers the effect of hydrothermal treatment, simulating a long stay in a biological environment, on the phase composition and bending strength of Al2O3 – [ZrYb]O2 composites containing a variable amount of Al2O3 and including strontium hexaaluminate. It has been shown that composites retain bending strength after hydrothermal action. This fact indicates the preservation of the phase composition in the volume of materials. It is determined that a monoclinic phase of zirconia is formed in the near-surface layer of the samples, the amount of which ranges from 11 to 9 %, correlating with the increase in the content of alumina in the composite. The formation of the monoclinic phase of zirconia in such an amount is well below the limit of 25 % specified in ISO 13356 2015 Implants for surgery — Ceramic materials based on yttria-stabilized tetragonal zirconia (Y-TZP). The results obtained make it possible to recommend Al2O3 – [ZrYb]O2 composites containing strontium hexaaluminate for medical applications.

The kinetic patterns of nitride formation have been established and the sequence of structural transformations characterizing high-temperature (at 1900 °C) nitridation of Zr-U alloys containing 2 and 5 wt.% U in the range from 3.5 to 60 minutes is presented. During high-temperature saturation with nitrogen for each composition, the solid solution (Zr,U) decomposes with the formation of composite structures ZrN-(ZrN1-n/UxEy/U)-ZrN (where E is O, N; n, x, y are stoichiometric coefficients ). During the decomposition of the solid solution, zirconium nitride is formed and a phase of metallic uranium is released, which accumulates impurities contained in the initial solid solution in the central part of the sample. Kinetic curves for a temperature of 1900 °C are approximated by an exponential law and correspond to the nitridation of zirconium. The nitridation rate of the (Zr,U) solid solution increases with increasing uranium content. To complete the formation process of a compact nitride solid solution of (Zr,U)N of stoichiometric composition, it is necessary to increase the temperature and increase the reaction duration.

Прямой карбидизацией циркониевого проката в атмосфере смеси газообразных аргона и этилена синтезирован компактный образец стехиометрического карбида циркония ZrC заданной формы. Формирование керамики происходит в результате взаимодействия металла с газообразным этиленом и при поглощении углерода, образующегося на реакционной поверхности при пиролизе С 2 Н 6 . Охарактеризована субструктура керамики, дана оценка механических и проводящих свойств ZrC.

Определены кинетические закономерности образования нитридов сплавов Zr–Nb (содержание Nb 0.1, 2.5 и 5 мас. %) при температуре 1900°C. Процесс азотирования характеризуется двухстадийностью, где обе стадии описываются экспоненциальным законом. Скорость химической реакции на второй стадии значительно меньше, чем на первой. Охарактеризован состав формирующихся гетероструктур Zr 1– х Nb х N–ZrN 1– n /β-твердый раствор циркония в ниобии–Zr 1– х Nb х N, установлена последовательность нитридизации компонентов исходного сплава. На первой стадии процесса происходят образование α-твердого раствора азота в Zr и его переход в нестехиометрический нитрид. Кинетическая зависимость на второй стадии описывает нитридизацию фазы β-Nb, образовавшейся при распаде твердого раствора Zr〈Nb〉. Показано, что продолжительность второй стадии процесса определяется количеством ниобия в исходном твердом растворе. Экспериментально подтверждена возможность создания однофазной керамики с активными добавками нитридизацией сплавов Zr–М в одностадийном процессе с сохранением исходной формы металлической заготовки.

Министерство науки и высшего образования Российской Федерации Российское химическое общество им.Д.И.Менделеева Секция по химической термодинамике и термохимии Научного совета РАН по физической химии Сибирское Отделение Российской Академии Наук Институт неорганической химии им.А.В.Николаева СО РАН

We have demonstrated general kinetic aspects of the formation of nitrides of Zr–Nb alloys (containing 0.1, 2.5, and 5 wt

Ceramic nitride samples of tailored composition and shape have been prepared by controlled nitridation of Ti–V metal pairs. We have obtained kinetic and current–voltage curves for the interaction of the Ti–V metal pairs with nitrogen. In different parts of the metal pairs, the nitridation process follows different mechanisms. In the case of the pure metals, the formation of nearly stoichiometric ceramics involves the formation of three- and two-layer graded structures. Nitridation of the junction region, containing a Ti–V solid solution, is determined by the chemical affinity of titanium and vanadium for nitrogen. The formation of titanium nitride leads to decomposition of the Ti–V solid solution in the junction and vanadium metal separation on grain boundaries. The rate of vanadium nitridation increases as the titanium content of the solid solution decreases. The thermoelectric voltage of the Ti–V system in the temperature range from –195.7 to +550°C has been evaluated as a function of the degree of nitridation. The thermoelectric voltage and Seebeck coefficient of metal–ceramic and ceramic structures have been determined as functions of temperature. Characteristically, the thermoelectric voltage of all the nitrided pairs rises monotonically over the entire temperature range studied. Nitrided titanium–vanadium pairs with tailored composition can be used as ceramic thermoelectric converters.

— Compact stoichiometric zirconium carbide (ZrC) with a tailored shape has been synthesized by direct carburization of rolled zirconium metal in an atmosphere of an argon + ethylene gas mixture. Ceramics have been produced by reacting zirconium metal with ethylene gas, through absorption of the carbon released on the reaction surface as a result of C 2 H 6 pyrolysis. We have characterized the microstructure of the ceramics and assessed the mechanical and conductive properties of the synthesized ZrC.

Abstract—The kinetic laws of nitride formation are revealed. The sequence of structural transformations characterizing high-temperature (at 1900°C) nitriding of Zr–U alloys with 2 and 5 wt

We describe a sequence of structural transformations characterizing high-temperature nitridation of zirconium–niobium alloys containing 0.1–10 wt % niobium. High-temperature saturation of solid solutions of niobium in zirconium with nitrogen is accompanied by decomposition of the Zr〈Nb〉 solid solution and the formation of Zr1 – хNbхN–(ZrN1 – n/β-solid solution of Zr in Nb)–Zr1 – хNbхN composite structures. During nitridation of the heterostructures, zirconium nitride reacts with β-niobium, which is the final step of the nitridation of the parent Zr〈Nb〉 solid solution. Characteristically, the ceramics thus prepared have near-surface porosity reproducing the surface porosity of the as-rolled material.

Ceramics based on hafnium carbide of a given shape have been synthesized by direct carbidization of rolled hafnium in a hydrocarbon atmosphere. Excess carbon resulting from high-temperature pyrolysis of hydrocarbons forms on the surface of ceramic hafnium carbide an easily detachable layer consisting of graphite with an admixture of amorphous carbon. The final formation of ceramics occurs at a temperature of 2400 °C in an atmosphere of an inert gas — argon. The phase composition and structure of the synthesized ceramics are characterized.

Zr–Nb–N nitride ceramics have been prepared via nitridation of rolled Zr–Nb solid solutions at temperatures of 1700, 1900, and 2400°C. We have determined the phase composition of the as-rolled alloys and the composition of the heterostructures and compact nitride obtained. Interaction of solid solutions of niobium in zirconium (0.1–10 wt % Nb) with nitrogen at temperatures below and above the peritectic reaction temperature has been shown to occur in two steps. In the first step, the solid solution decomposes to give zirconium nitride and metallic niobium embedded in its bulk: Zr〈Nb〉 + N2 → ZrN1 – х + β-Nb. In the second step, the metallic niobium reacts with nitrogen: ZrN1 – х/β-Nb + N2 → (Zr,Nb)N. The resulting niobium nitride dissolves in the ZrN, reducing the lattice parameter of the zirconium nitride.

Stoichiometric niobium carbide (NbC) samples with a tailored shape have been synthesized by direct carburization of rolled metallic niobium in an atmosphere of an argon + ethylene gas mixture. Ceramics have been produced by reacting niobium metal with ethylene gas, through absorption of the carbon released on the niobium surface as a result of ethylene decomposition. Complete carburization has been shown to be accompanied by the formation of an anisotropic inner cavity, reflecting the initial shape of the sample, which is characteristic of ceramics produced using the oxidation-assisted engineering approach. We have studied the substructure, superconducting properties, and mechanical properties of NbC synthesized via high-temperature carburization of niobium foil.

The article presents the results of 3D printing with ceramic suspensions by DLP method using inorganic dyes.