Modification Of ZrO2 Research Articles

Application of ZrO2 and Ni modified carbon nanotube composites as bifunctional water electrolysis catalysts

By using carbon nanotube (CNT) as the carrier, Ni as the active center and ZrO2 as the modifier, an efficient electrocatalytic material (ZrO2-Ni/CNT) is designed and synthesized in this paper. The structure and properties of the catalyst are characterized by various instrumental analysis methods such as SEM, TEM, XRD and XPS. The electrochemical test results show that the addition of ZrO2 can significantly improve the catalytic performance of this catalyst in the electrochemical water splitting. In an alkaline solution, ZrO2-Ni/CNT catalyst displays an exceedingly low overpotential of 169 mV and 249 mV at the current density of 10 mA cm−2 towards hydrogen evolution reaction and oxygen evolution reaction, respectively. This work shows that the modification of ZrO2 can improve the electrocatalytic activity of Ni-based materials, and the modification strategy can be applied to improve the electrocatalytic activity of commercial Ni-based electrode materials.

Effect of The Amount of 3-(trimethoxysilyl) propyl methacrylate on Improving Surface’s Adhesive Properties of Zirconia

Abstract The objective of this research was silanize zirconium oxide (ZrO2) nanoparticles with 3-(trimethoxysilyl) propyl methacrylate (γ -MPS). Silanization is a surface treatment process of a material using silane compounds to improve the surface adhesive and compatibility of ZrO2 with other materials or coatings and to modify its surface. The surface modification of ZrO2 by 3-(trimethoxysilyl) propyl methacrylate as coupling agents under the influence of ultrasonic waves. The silanized ZrO2 was characterized Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). The FTIR analysis indicated the interaction of the silane compound on the ZrO2 surface, showing characteristic peaks corresponding to Zr-OH, C-H stretching, carbonyl groups, and Zr-O-Si bonds, indicating successful grafting. The FTIR spectra for the ZrO2 nanoparticles, showing peaks at 1088 cm−1 showed the formation of Zr-O-Si covalent bonds. ZrO2 nanoparticles also exhibited a characteristic peak at 400 cm−1, indicating the deformation of Zr-O-Zr bonds. C=C, and C=O peaks are observed in the range of 1632-1714 cm−1. Thermogravimetric analysis (TGA) measures showed a higher weight loss of the silanized ZrO2 when higher amounts of silane were added.

Phase relations in the La2O3-ZrO2-HfO2 system at 1250 °C and 1500 °C

In the present study, the phase equilibria in the ternary system La2O3-ZrO2HfO2 have been studied in the whole concentration range. In the course of the study, isothermal sections of the phase diagram of the system were constructed at temperatures of 1500 and 1250 °C. The obtained results indicate the no new phase formation in the studied system. It was found that in the La2O3-ZrO2HfO2 ternary system at temperatures of 1500 and 1250 °C, solid solutions are formed on the basis of monoclinic (M, space group P21/C) HfO2 and tetragonal (T, space group P42/nmc) modifications of ZrO2, solid solutions based on a hexagonal modification (A, space group P3m1) of La2O3, and an ordered phase with a pyrochlore-type structure of La2Zr2О7 (La2Hf2О7) (Py, space group Fd-3 m). The system studied is characterized by the formation of a continuous series of solid solutions with a pyrоchlore-type structure. A decrease in temperature from 1500 °C to 1250 °C leads to the shift of the three-phase region, containing solid solutions based on a pyrochlore-type structure of Ln2Zr2О7 (Ln2Hf2О7), monoclinic M-HfO2, and tetragonal T-ZrO2, towards the concentration area with higher ZrO2 content and also to an increase in the extent of the solid solution based on the monoclinic modification M-HfO2.

The promotional effects of ZrO2 modification on the activity and selectivity of Co/SiC catalysts for Fischer-Tropsch synthesis

Co/SiC catalysts have exhibited excellent performance in Fischer-Tropsch synthesis reaction. However, few research focuses on investigating the effect of SiC supports surface properties of on catalyst performance. In this study, ZrO2 was utilized to modify the SiC surface, leading to the preparation of a series of Co-ZrO2/SiC catalysts. The physicochemical properties of the catalyst were comprehensively analyzed by using N2 adsorption, XRD, H2-TPR, XPS analyses. Catalytic performance was evaluated using a fixed bed reactor, shedding light on the effect of ZrO2 modified SiC support on cobalt-based Fischer-Tropsch synthesis catalysts. The results indicated that ZrO2 surface modification on SiC resulted in an enhanced reduction degree of Co/SiC catalysts. Additionally, ZrO2 exhibited strong interaction with the amorphous phase on the SiC surface, thereby weakening the interaction between Co and the amorphous phase. This led to an increase in the electron density of cobalt species, consequently improving the selectivity of Co/SiC catalysts towards long-chain hydrocarbons.

Experimental study of isothermal sections of the ZrO2–HfO2–Eu2O3 ternary diagram at 1500 °С and 1700 °С

In the present work the phase equilibria in a system of zirconium and hafnium dioxides and europium sesquioxide have been studied. The study was conducted at temperatures of 1700 °С and 1500 °С. Based on the results, isothermal sections at these temperatures were constructed. It was found that in the ZrО2–HfO2–Eu2O3 ternary system at temperatures of 1700 °С and 1500 °С solid solutions are formed on a monoclinic (M, space group P21/C) modification of HfO2, a tetragonal (T, space group P42/nmc) modification of ZrO2, cubic solid solutions ZrO2 (HfO2) with a fluorite structure (F, space group Fm3m), C-type cubic solid solutions of Eu2O3 (space group Ia-3), solid solutions based on the monoclinic modification (B, space group C2/m) of Eu2O3, as well as an ordered phase with a pyrochlore structure of Eu2Zr2O7 (Eu2Hf2O7) (Py, space group Fd-3m). The phase boundaries and the unit cell parameters of the formed phases were determined. The studied isothermal sections of the ZrО2–HfO2–Eu2O3 system are characterized by the formation of continuous series of cubic solid solutions based on the phase with a pyrochlore structure. The formation of new phases in the ZrО2–HfO2–Eu2O3 system at 1700 °С and 1500 °С was not observed.

Preparation and catalytic evaluation of phosphated zirconia nanopowder for ethanol dehydration into diethyl ether

Research on renewable energy development is intensified nowadays, including the production of diethyl ether (DEE) as a high-value alternative fuel. This study explored the catalytic conversion of ethanol into diethyl ether using a phosphated zirconia catalyst. We examined different concentrations of phosphoric acid (1, 2, 3, and 4 M) and calcination temperatures (400, 500, and 600 °C) applied to zirconia nanopowder to evaluate their influence on the acidity of the resulting phosphated zirconia. The catalysts were characterized by FTIR, XRD, SAA, SEM-EDX Mapping, and TG-DTA. Among the catalysts tested, the PZ-2-400 catalyst, prepared with a 2 M H3PO4 concentration and calcined at 400 °C, exhibited the highest acidity value of 0.56 g/mol pyridine. When operated at the optimum temperature of 225 °C, this catalyst achieved an ethanol conversion of 80.04 % and a diethyl ether yield of 1.00 %. These findings suggest that modification of ZrO2 with phosphoric acid acts as a solid acid catalyst for diethyl ether synthesis with better activity and selectivity than unmodified ZrO2.

Improving catalytic activity of MoP for CO2 reforming of methane via ZrO2 modification

Molybdenum phosphide (MoP) has attracted increasing attention as a novel catalytic material for CO2 reforming of methane in virtue of superior coke resistance, but its catalytic reactivity is still relatively low. This work for the first time improved the reforming activity of MoP via ZrO2 modification. The Zr0.01MoP catalyst with Zr/Mo molar ratio of 0.01 possessed much higher activity than bare MoP at 800–900 °C. Structural characterizations revealed that the introduction of ZrO2 would decrease the particle size, modify the electronic structure and change the reducibility property of MoP, which may function together to deliver the higher activity.

Self-propagating high temperature synthesis of composite material based on stabilized zirconium oxide

In this work, ceramic composite materials based on stabilized zirconium oxide with the content of stabilizing additives up to 9 mol. %. Y2O3 was obtained by self-propagating high temperature synthesis. The effect of the content of the stabilizing additive on the characteristics of the combustion of the obtained materials, their phase composition has been studied. It is shown that the introduction of Y2O3 into the studied materials leads to the formation of the cubic modification of ZrO2 in the products of synthesis, while without the introduction of Y2O3 into the synthesis products there were three modifications of ZrO2.

ZrO2 modification of homogeneous nitrogen-doped oxide MgTa2O6−xNx for promoted photocatalytic water splitting

Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen, but currently the poor charge separation severely limits their photocatalytic performances. In this work, a homogeneous nitrogen-doped tunneled oxide of MgTa2O6−xNx with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO2 modification on the charge separation as well as photocatalytic performance. It is interesting to observe that the formation of the reduced tantalum species, regarded as recombination centers, in the MgTa2O6−xNx sample could be effectively inhibited via the surface passivation with ZrO2 nanoparticles, based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted. Together with modification of the deposited Pt cocatalyst, the optimized H2 evolution rate over Pt-ZrO2/MgTa2O6−xNx (Zr/Ta = 0.10) photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa2O6−xNx sample free of ZrO2 modification, whose apparent quantum yield at 420 nm (± 15 nm) achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts. The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO2 modification, which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species. This work extends the application territory of ZrO2 modification to the homogeneous nitrogen-doped oxide photocatalysts, and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.

ISOTHERMAL SECTION OF THE ZrO2–HfO2–Eu2O3 SYSTEM PHASE DIAGRAM AT 1100 °C

Phase equilibria and structural transformations in the ternary ZrO2–HfO2–Eu2O3 system at 1100 °C were studied by X-ray diffraction over the entire composition range. The samples of different compositions have been prepared from nitrate acid solutions by evaporation, drying, and calcinations at 1100 °C. Fields of solid solutions based on the cubic (F) modification with fluorite-type structure and tetragonal (T) and monoclinic (M) modifications of ZrO2 (HfO2), cubic (C) modification of Eu2O3, and an ordered intermediate phase with pyrochlore-type structure, Ln2Zr2O7 (Ln2Hf2O7)(Py), were established to exist in the system. The solubility of Eu2O3 in M-HfO2(ZrO2) is pretty low and approximately less than 1 mol%, which is confirmed by XRD. The boundaries of phase fields and lattice parameters of the phases were determined. The lattice parameters for F phase vary from а = 0.5305 nm in two-phase sample (C+F) containing 6.75 mol% ZrO2–8.25 mol% HfO2–85 mol% Eu2O3 to а = 0.5283 nm for sample containing 27 mol% ZrO2–33 mol% HfO2–40 mol% Eu2O3 and to а = 0.5275 nm in two-phase sample (Py+F) containing 29.25 mol% ZrO2–35.75 mol% HfO2–35 mol% Eu2O3, and from а = 0.5232 nm in two-phase sample (Py+F), containing 32.625 mol% ZrO2–39.875 mol% HfO2–27.5 mol% Eu2O3 to а = 0.5218 nm sample containing 33.75 mol% ZrO2–41.25 mol% HfO2–25 mol% Eu2O3 and to а = 0.5176 nm in two-phase sample (F+M) containing 40.5 mol% ZrO2–49.5 mol% HfO2–10 mol% Eu2O3 along the section Eu2O3–(55 mol% HfO2–45 mol% ZrO2). The fluorite-type structure (F) is in equilibrium with all phases that exist in the ternary ZrO2–HfO3–Eu2O3 system at 1100 °C and forms substitutional solid solutions with phases of the binary systems. In the ZrO2–HfO2–Eu2O3 system, an infinite series of solid solutions form from the Ln2Zr2O7 (Ln2Hf2O7) (Py) phase. The isothermal section of the ZrO2–HfO2–Eu2O3 phase diagram at 1100 °C contains one three-phase regions (T + M + F) and six two-phase regions (F + C, two-F + Py, F + M, F + T, T + M). No new phases were found in the ZrO2–HfO2–Eu2O3 system at 1100 °C and the nature of phase equilibria was determined by the constitution of the boundary binary systems.

Isothermal section of the ZrO2–HfO2–Nd2O3 ternary phase diagram at 1100 °C

In the presented work, based on the results obtained by X-ray diffraction and microstructural analysis, phase equilibria have been studied and an isothermal section of the ZrO2–HfO2–Nd2O3 ternary phase diagram at 1100 °C has been constructed. Unit cell parameters were calculated by the least squares method using the LATTIC software. The International Powder Standards Committee database (JSPSDS International Center for Diffraction Data 1999) was used to determine the phase composition.It was found that in the studied system are formed regions of solid solutions based on a cubic fluorite-type (F) modification, a tetragonal (T) modification of ZrO2, a monoclinic (М) modification of HfO2, a hexagonal (А) modification of Nd2O3, as well as an ordered (Py) pyrochlore phase of Nd2Zr2O7 (Nd2Hf2O7). The boundaries of the phase regions and the unit cell parameters are determined. A continuous series of solid solutions based on the ordered pyrochlore (Py) phase of Nd2Zr2O7 (Nd2Hf2O7) at the studied temperature is derived. The unit cell parameters of the ordered pyrochlore (Py) phase vary from a = 1.0633 nm for the two-phase composition (Py + M), 47.5 mol% ZrO2 – 47.5 mol% HfO2 – 5 mol% Nd2O3) to a = 1.0639 nm for the boundary composition of the solid solution (37.5 mol% ZrO2 – 37.5 mol% HfO2 – 30 mol% Nd2O3) and then up to a = 1.0648 nm for the two-phase (Py + A) composition (30 mol% ZrO2 – 30 mol% HfO2 – 40 mol% Nd2O3) which located along the Nd2O3 – (45 mol% ZrO2 – 55 mol% HfO2) constant ratio line. The studied isothermal section is characterized by the formation of two three-phase (Py + F + M and F + T + M) and six two-phase (A + Py, Py + M, Py + F, F + M, T + M, F + T) regions. In the ZrO2–HfO2–Nd2O3 ternary system, no new phases are detected at the temperatures studied.

Modeling of the ZrO2-SiO2-Al2O3 phase diagram using simulation by the 3D computer model and the NUCLEA database

The reliability of modeling of the ZrO2-SiO2-Al2O3 phase diagram up to the temperature 3000 K (melting of ZrO2) was illustrated using simulation by the three-dimensional (3D) computer model in comparison with the results of calculation by the NUCLEA database. For this purpose, the 3D computer model with three polymorphic modifications of ZrO2 and four modifications of SiO2 has been designed. The satisfactory agreement between both approaches as well as experimental studies of the ZrO2-SiO2-Al2O3 phase diagram was demonstrated while considering the features of isothermal sections and isopleths in the system under study.

Plasma Electrolytic Modification of Zirconium and Its Alloys: Brief Review.

The review focuses on the surface modification of Zr and its alloys, which is necessary to expand the applications of these kinds of materials. Data on the properties of pure zirconium and its alloys are presented. Since surface engineering and the operation of the above materials are in most cases associated with the formation of oxide coatings, information on the characteristics of ZrO2 is given. In addition, attention is paid to phasing in the zirconium-oxygen system. It is noted that the most effective method of surface engineering of Zr and its alloys is plasma electrolytic modification (PEM) technology. Specific examples and modes of modification are described, and the reached results are analyzed. The relevance, novelty and originality of the review are determined by the insufficient knowledge about a number of practical features concerning the formation of functional oxide coatings on Zr and some of its alloys by the technology of PEM. In particular, the information on the phase composition and possibilities of stabilization of the tetragonal and cubic modifications of ZrO2, the effects of the component composition of electrolyte solutions and electrolyte suspensions, and the specifics of the treatment of additive shaping and deformed materials are rather contradictory. This review aims to collect recent advances and provide insights into the trends in the modification of Zr and its alloys, promote the formulation of practical recommendations and assess the development prospects.

Phase equilibria in the ZrO2–HfO2–Nd2O3 system at 1500 °C and 1700 °C

The phase equilibria in the ZrO2–HfO2–Nd2O3 ternary system at 1500 °C and 1700 °C were studied over the whole concentration range by X-ray diffraction and microstructural analyses. Corresponding isothermal sections were constructed from the data obtained. It was found that solid solutions in this system are derived from a tetragonal (T) modification of ZrO2, a monoclinic (M) modification of HfO2, a hexagonal (A) modification of Nd2O3, a cubic phase with a fluorite (F) structure of ZrO2 (HfO2), and an ordered phase with a pyrochlore (Py) structure of Nd2Zr2O7 (Nd2Hf2O7). The phase boundaries and unit cell lattice parameters were determined. The solubility of Nd2O3 in M − HfO2 is pretty low and about less than 1 mol%, as confirmed by XRD and microstructural analyses. The ordered pyrochlore-type (Py) phase of Nd2Zr2O7 (Nd2Hf2O7) forms continuous series of solid solutions at 1500 °C and 1700 °C. The homogeneous region of these continuous series of solid solutions changes insignificantly with increasing temperature. The changes in the construction of the isothermal section of the ZrO2-HfO2-Nd2O3 phase diagram at 1500 °C compared to 1700 °C are associated with the thermal stability of cubic fluorite-type (F) solid solutions. Other phases in the ZrO2-HfO2-Nd2O3 ternary system are not detected at the studied temperatures.

Pt single-atom loaded on nonmetallic elements (C, N, P, S) doped ZrO2 in photocatalytic hydrogen evolution: First principles

It is of great significance to regulate the coordination environment of ZrO2 to enhance its photocatalytic hydrogen evolution activity. In this paper, non-metallic elements (A = C, N, P, S) doped ZrO2 photocatalysts are designed based on first-principles, and further loaded with single-atom Pt. The relationship between the composition and performance of photocatalysts during doping and loading of single-atom is explained through electronic properties, and their photocatalytic hydrogen evolution performance is explored. Loading and doping have a synergistic effect on the modification of ZrO2, and doping effectively improves its catalytic performance. Among them, P doping greatly reduces the Gibbs free energy of the reaction. After the introduction of Pt single atoms, Pt@ZrO2(111)-P still has the best structure for photocatalytic hydrogen evolution, and the good surface electronic activity significantly improves the hydrogen evolution reaction(HER) activity (free energy of −0.01 eV). This design provides a new catalytic model for the photocatalytic hydrogen evolution system and also provides some ideas for understanding the synergistic effects of loading and doping.

A Systematic Review on Current Status of Zirconia Bonding with Novel Silane Couplant for Dental Restorations

For the past two decades, research is under progress seeking alternative materials for titanium and titanium alloys that are used as dental metal restorations. Favorable characteristics of zirconia (ZrO2) ceramic replaced metal-free restorations. This paper provides an insight on ZrO2 potential with a novel silane couplant as a material for dental applications, its mechanical properties, biological characteristics and optical properties. Review shows ZrO2’s tooth like color, mechanical properties, biocompatibility, and low plaque affinity makes as it a suitable implant material. It is designed to produce the shape and functions of natural teeth by filling, denture and implant. Hence, ZrO2 replaced the titanium implants as an alternate with integrated CAD/CAM techniques. The research on surface modification of ZrO2 and its capability to chemically activate the surface is critical in achieving adhesive bonding. The chemical inertness shows difficulty in achieving the reliable bonding between the resin composite cements and ZrO2 ceramics. The silanization of zirconia reported promising results confirming the stability of zirconia in the long-term.

OXIDATIVE AMMONOLYSIS OF 4-METHYLPYRIDINEON OXIDE VANADIUM-TITANIUM-ZIRCONIUM CATALYST MODIFIED BY TIN AND TUNGSTEN OXIDES

Catalysts based on vanadium pentoxide modified by Ti, Sn, Zr and W oxides were tested in the oxidative ammonolysis of 4-methylpyridine. The role of the main process parameters such as temperature, the ratio of the initial components in the conversion of the methyl group to the nitrile one, and the optimal conditions for the oxidative ammonolysis of 4-methylpyridine were determined. It is determined that the V-Ti-Zr-O-catalyst and the sample containing 9% of tungsten oxide are superior in catalytic activity to the V-Ti-Zr-Sn-O contact. Conditions that ensure a high selectivity for the formation of 4-cyanopyridine were found. The highest yield of the target product (85-86%) was obtained on V-Ti-Zr-W-O at 270 °C, and the yield of 4-cyanopyridine was 87.5% at 310° C on the V-Ti-Zr-Sn-O catalyst. The phase composition and structural changes occurring in modified vanadium oxide catalysts have been studied. It is determined that mixed V-Ti-Zr-Sn-O and V-Ti-Zr-W-O catalysts contain ZrV2O7, the monoclinic modification of ZrO2 (baddeleyite), TiO2 (anatase), SnO2, WO3, and V2O5. In catalysts, it can exist in small amounts as a separate VO2 phase. The V-Ti-Zr-W-O catalyst showed the best catalytic properties. It has highactivity and selectivity towards 4-cyanopyridine.

ISOTHERMAL SECTION STRUCTURE THE ZrO2-La2O3-Gd2O3 SYSTEM AT 1500 °С

Using the methods of physicochemical analysis (XRD, petrography, scanning electron microscopy analyses) phase equilibria were firstly investigated in the ternary system ZrO2–La2O3–Gd2O3 system at 1500 ºС. It was established that in the system there exist fields of solid solutions based on hexagonal (A) modification of La2O3 and cubic with fluorite-type structure (F) and tetragonal (Т) modification ZrО2 , cubic (С) and monoclinic (M) modification Gd2O3 and ordered intermediate phase with pyrochlore-type structure lanthanum zirconate La2Zr2O7 (Py). No new phases were found. The refined lattice parameters of the unit cells for solid solutions for the systems were determined.
 In the zirconia-rich corner, the solid solutions based on tetragonal modification of ZrO2 are formed. The phase field T-ZrO2 is narrow and elongated (0–18 mol% CeO2) along the ZrO2–CeO2 side of the binary system. The solubility of La2O3 in the T-ZrO2 is low and amounts to ~ 0.5 mol%, as evidenced by XRD analysis results. It is worth noting that the solid solutions based on tetragonal modification of zirconia cannot be quenched from high temperatures due to low stability of T-ZrO2 under cooling with furnace conditions. The diffraction patterns recorded at room temperatures included the peaks of monoclinic phase M-ZrO2.
 The homogeneity field of solid solution based on A-La2O3 extends to 31 mol% Gd2O3 and 12 mol% ZrO2 in the corresponding binary systems and locates near the composition 6,7 mol % ZrO2–90 mol% La2O3–3.3 mol% Gd2O3 on the section La2O3–(67 mol % ZrO2–33 mol % Gd2O3). It should be noted that the samples with a higher lanthanum oxide content after annealing and cooling rapidly absorb water in humid air and become hydrated. Hence, according to XRD, the hexagonal A-La(OH)3 modification forms instead of the hexagonal A-La2O3 phase. The lattice parameters for A-La(OH)3 phase vary from а = 0.6513 nm, c = 0.3847 nm the sample containing 3.35 mol % ZrО2–95 mol % La2O3–1.65 mol % Gd2O3 to а = 0.6508 nm, c = 0.3847 nm in the two-phase sample (Py+А ) containing 6.7 mol % ZrО2–90 mol % La2O3–3.3 mol % Gd2O3 and to а = 0.6477 nm, c = 0.3725 nm in the three-phase sample (Py+F+А) containing 40.2 mol % ZrО2–40 mol % La2O3–19.8 mol % Gd2O3
 The isothermal section of the ZrO2–La2O3–Gd2O3 system at 1500°C contains four three-phase regions (F+Py+A, F+B+A, F+C+B, T+F+Py) and ten two-phase regions (Py+A, A+F, A+B, F+B, B+C, C+F, F+Py, Py+T, T+F, Py+F).

Effect of Al<sub>2</sub>O<sub>3</sub> nanofibers on compaction, phase composition, and mechanical properties of ZrO<sub>2</sub>-based composites obtained by vacuum pressureless sintering

This work studies the effect of the relative content of Al2O3 nanofibers on the compaction, phase composition, and physicomechanical properties of composites based on ZrO2 obtained by free vacuum sintering. It was found that in the process of manufacturing composites, nanofibers are sintered into Al2O3 grains of complex, elongated shape, which form a solid, frame-reinforcing structure. The relative density of composites with 5 wt. % and 10 wt. % of nanofibers, decreases up to 95%. It is shown that in all sintered samples the tetragonal modification of ZrO2 acts as the main phase, and the different content of nanofibers affects the amount of cubic and monoclinic modifications of ZrO2. It was found that addition of 5 wt. % and 10 wt. % of Al2O3 nanofibers increases the microhardness of the composite by 11% and crack resistance by 46%.

Phase equilibrium in systems based on oxides of zirconium, lanthanum and samarium

According to the results of the samples studied by X-ray diffraction and microstructural analyzes the phase equilibria in the binary La2O3 – Sm2O3 and ternary ZrO2 – La2O3 – Sm2O3 systems were studied. The boundaries of the phase fields of the binary system are specified and an isothermal cross section of the ternary state diagram of the ZrO2 – La2O3 – Sm2O3 system at a temperature of 1500 °C is constructed. No new phases have been identified in the studied systems. It is established that in the ternary system ZrO2 – La2O3 – Sm2O3 at 1500 °C fields of solid solutions on the basis of cubic (F) modification with structure of fluorite type, tetragonal (T) modification of ZrO2, monoclinic (B) modifications of Sm2O3, hexagonal (A) are formed. La2O3, as well as an ordered phase with a structure of the type of pyrochlore Ln2Zr2O7 (Py). The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. A characteristic feature of this isothermal cross section is the formation of a continuous series of solid solutions based on the phase of the pyrochlore type La2Zr2O7 (Sm2Zr2O7). The limiting solubility of Sm2O3 in the ordered phase La2Zr2O7 is 16 mol. % along the section Sm2O3- (67 mol.% ZrO2 - 33 mol.% La2O3). The solubility of La2O3 in the solid solution Sm2Zr2O7 is slightly less and is 11 mol. % along the section La2O3- (67 mol.% ZrO2 - 33 mol.% Sm2O3). The isothermal cross-section of the state diagram of the ZrO2 – La2O3 – Sm2O3 system at 1500 °C is characterized by the presence of three three-phase (Py + T + F), (A + Py + B), (Py + F + B) and eight two-phase (A + Py), (B + A), (B + Py), (F + B), (T + F), (Py + T), (F + Py-two) areas.