Addition Of ZrO2 Research Articles

Mechanical and tribological characteristics of ZrO2 reinforced Al2014 matrix composites produced via stir casting route

Metal matrix composites reinforced with fillers found many applications in several industries like aerospace and automobile in recent decades. In this current work, Al2014 was chosen as the matrix material and Zirconium Oxide (ZrO2) as reinforcing material. ZrO2 was varied at 2, 4, 6 wt% in Al2014 matrix while magnesium was maintained constant at 1 wt% for all compositions. Magnesium was added to the composite for increasing the wettability. The composites was produced by stir casting process. The dispersion characteristics of the manufactured specimens was studied by Field Emission Scanning Electron Microscope (FESEM) with EDS. The specimens were prepared according to ASTM standards to carry out tests like tensile strength, compressive strength, hardness and impact strength. The tribological properties of the manufactured Al2014 and Al2014 composites specimen were examined using two body wear tests. The mechanical properties and tribological properties of the Al2014 composites increased when the addition of ZrO2 by 6 wt%. The worn surface morphology of the abraded samples was studied by optical microscope which minimum level of damage when ZrO2 was added at 6 wt%.

Effect of Transition Metals Oxide Additives on the Properties of Mixed-Alkali Glass for Electric Insulating Coatings on Aluminum

In order to reduce the cost of the thick-film technology of microcircuits and heating elements, as well as to expand its areas of use, it became necessary to expand the range of materials that, along with ceramics and steel, can also be used as substrates for these products. One of these advanced materials is aluminum. Electrically insulated coatings on metals are subjected to repeated heating and cooling while their produce and use, which promotes the creation of temperature stresses in the coating and leads to their chipping. Therefore, in order to improve the water resistance and adhesion strength of electrical insulation coatings on aluminum, CuO, ZrO2 and Bi2O3 additives were examined. There was found an increase in water resistance with a simultaneous increase in the adhesion strength of the enamel coating with an aluminum substrate with the addition of not more than 3 pts. wt. of copper oxide (II), up to 1 pts. wt. of zirconium oxide (IV), and up to 4 pts. wt. of bismuth oxide (III) w.r.t. 100 pts. wt. of glass.

Performance of Catalytic Fast Pyrolysis Using a γ-Al2O3 Catalyst with Compound Modification of ZrO2 and CeO2

To investigate the catalytic pyrolysis performance of complex metal oxide catalysts for biomass, γ-Al2O3 was prepared through the precipitation method, and then ZrO2 and γ-Al2O3 were blended in the proportion of 2:8 using the co-precipitation method. Next, CeO2 was loaded on the surface of the catalyst for further modification. The three catalysts, A, ZA and CZA, were obtained. The specific surface and acidity of the catalysts were characterized by nitrogen adsorption–desorption and NH3-Temperature Programmed Desorption (NH3-TPD) respectively. The catalytic pyrolysis performance of catalysts for bamboo residues was investigated by Pyrolysis gas chromatography mass spectrometry (Py-GC/MS). Chromatograms were analyzed for identification of the pyrolysis products and the relative amounts of each component were calculated. Experimental results indicated that catalyst A had a good catalytic activity for the fast pyrolysis of bamboo residues. The addition of ZrO2 and CeO2 could continuously enhance the acidity of the catalyst and further promote the pyrolysis of macromolecular compounds and deoxidation of oxygen-containing compounds. Finally, catalyst CZA, obtained by compound modification, could not only dramatically reduce the relative content of phenol, acid and aldehyde and other oxygen-containing compounds, but also achieved the maximum hydrocarbon yield of 23.38%. The catalytic performance of catalyst CZA improved significantly compared with catalyst A.

Effects of SDBS and ZrO2 additives on the microstructure and properties of silicon-bonded SiC porous ceramics

Porous silicon-bonded silicon carbide (SBSC) ceramics were prepared under argon atmosphere, with silicon as pore former and bonding material, simultaneously, sodium dodecyl benzene sulfonate (SDBS) and ZrO2 as sintering additives, the effects of SDBS and ZrO2 on the porosity, pore size, mechanical, physical and thermal properties and microstructures were investigated. The results suggested that suitable content of SDBS and ZrO2 could not only effectively lower the sintering temperature to 1450 °C due to the sticky flow of molten silicon, but also increase the pore structure and improve the bending strength. The reason for this is that SDBS decomposed into Na2O which reacted with ZrO2 and impurity SiO2, which was the native oxide film on the surface of SiC particles, to form a bonding phase between SiC particles to improve the bending strength; meanwhile, the disappearances of impurity SiO2 would benefit the bond of molten silicon and silicon carbide particles, and silicon melt leaving pores in its original position to increase the pore structure. The optimal apparent porosity, bending strength, average pore size, gas permeance and residual bending strength after thermal shock cycles of SBSC porous ceramic sintered at 1450 °C with 5 wt% SDBS and 6 wt% ZrO2 were 38.33%, 55.4 MPa, 11.3 μm, 106.4 m3/m2·h·kPa and 28.2 MPa, respectively.

Effect of graphene and zirconia on microstructure and tribological behaviour of alumina matrix nanocomposites

The inherent brittleness of monolithic alumina (Al2O3) has consistently limited its potential for several high-performance structural applications such as engine turbine parts and high temperature space materials. The fracture toughness and wear properties of alumina can be improved by the uniform dispersion of sub-micron and nano-phase particles in the alumina parent matrix. In the current study, alumina-based nanocomposites were fabricated by homogeneous dispersion of zirconia (4 wt% and 10 wt%) and graphene (0.5 wt%) using colloidal mixing followed by hot-pressing at 1600 °C for 1 h. The microstructure of the processed composite was extensively observed under high-resolution electron microscopes. The effects of zirconia and graphene on the mechanical and tribological properties were also investigated. The final microstructures depict extensive grain-refinement by the uniform dispersion of 0.5 wt%Gn and 10 wt%ZrO2 in the parent alumina matrix. A coarse-grain microstructure was observed with the addition of the 4 wt%ZrO2 due to insufficient inhibition of alumina grain growth during sintering. The coefficient of friction results from the wear test using a UMT Tribolab equipment with constant normal load of 25 N, 100 mm/s sliding velocity for 1000s, under ASTM G133-05 illustrates a steep increase for the 0.4 wt% ZrO2 addition but a significant decrease for the 10 wt%ZrO2 addition. Consequently, the addition of 10 wt% ZrO2 resulted in ∼98% decrease in the wear rate which was attributed to its refined microstructure and effective load-bearing activities of the uniformly dispersed ZrO2 precipitates. Meanwhile, the addition of 0.5 wt%Gn revealed a fine-grained microstructure and consequent lower wear rate (∼90.5%), but there was a relative increase in the coefficient of friction, which suggested that there is a direct relationship between the microstructure and wear behaviour than the coefficient of friction.

Enhanced thermal shock resistance of BN-based composites sintered by hot-pressing with the introduction of nano oxides

In this study, the BN-SiC composites were enhanced using individual or composite nano additives (Al2O3, ZrO2) sintered by hot pressing. The phase compositions, microstructure, mechanical properties, and thermal shock resistance of BN-based composites were comparatively investigated. The results showed that: the collaborative addition of nano ZrO2 or Al2O3 stimulated the solid diffusion and promoted the densification behavior. Meanwhile, the BN-SiC composites presented suitable development of BN plates and exhibited excellent structural uniformity due to the nano particles incorporated. As a result, the flexural strengths and fracture toughness of 10 wt% Al2O3 and 10 wt% ZrO2 improved significantly to 355.7 MPa and 5.78 MPa m1/2, respectively. In addition, BN-based composites exhibited excellent thermal shock resistance up to temperature difference (ΔT) = 1200 °C, where no catastrophic failure has been observed for all the specimens except the individual 10 wt% Al2O3 containing specimens. The main enhancing mechanisms were attributable to the “crack deflection”, “crack bridging” and “pulling-out” of BN plates, and the prolonged crack propagation paths along the fine particles.

Effects of nano ZrO2 content on the comprehensive properties of BN-SiC composites

Hot-pressed BN-SiC composites applied for the steel casting application were enhanced using nano Al2O3 and ZrO2 additives. The influences of nano ZrO2 content on the mechanical properties, thermal shock resistance, oxidation resistance, and steel corrosion resistance of BN-SiC composites were investigated. The results showed that the collaborative addition of nano ZrO2 and Al2O3 dominated the densification behavior due to the enhanced solid diffusion and pore filling effects. the improved densification and induced microstructure evelopment contributed to enhanced mechanical properties and thermal shock resistance. Consequently, the flexural strength and fracture toughness of 15 wt% nano ZrO2 containing specimens reached to 334.6 ± 0.1 MPa and 4.60 ± 0.13 MPa m1/2, respectively. Furthermore, no catastrophic fracture was observed during thermal shock tests even under a temperature difference at 1200 °C. In addition, the prepared composites exhibit excellent steel corrosion resistance at 1600 °C, attributing to the much finer grain size and quick formation of protective ZrO2 layer at the interface.

Gelation, Phase-Formation, and Sintering Processes in the Sol-Gel Method of Producing Aluminosilicate Glass-Ceramic Modified by Refractory Hafnium and Zirconium Oxides

Glass-ceramic based on compositions in the system Sr(Ba)–Al2O3–SiO2, modified by additions of zirconium oxide ZrO2 and hafnium oxide HfO2 with and without yttrium as a stabilizer, was synthesized by the sol-gel method. It was shown that the introduction of refractory oxides shortens the gelation time of the initial solutions, intensifies the sintering of the glass-ceramic, and changes the temperature intervals of phase formation processes and the nature of the precipitated crystalline phases. The sol-gel method made it possible to obtain a uniform distribution of the modifier-oxide grains in the bulk of the glass-ceramic. The yttrium oxide in the structure of the materials is concentrated near ZrO2 and HfO2 particles.

Properties of zirconia-containing glass-ionomer cement

Abstract Glass-ionomer cements (GICs) are used as restorative dental materials due to their capacity to chemically adhere to enamel and dentin, low thermal expansion coefficient, and compatibility with dental structures. However, these materials have low resistance to wear and fracture. In this work, zirconia-reinforced GICs were prepared to evaluate the influence of particle size as well as ZrO2 content on their properties. All evaluated composites presented compressive strength values above the pure GIC strength. The highest compressive strength values were obtained with the addition of 8.5 wt% ZrO2. The average roughness obtained was not significantly changed compared to commercial GIC and the lowest value was for the composite with 10 wt% ZrO2 (50 mesh). In the microhardness test, the highest values were obtained with the addition of 8.5 wt% of ZrO2. Therefore, the results indicated that the addition of ZrO2 to GIC is an effective alternative to improve the quality of dental restorations.

Elucidation on the Microstructural and Mechanical Properties of Tailored VAL12 Hybrid Composites with ZrO<sub>2</sub> Dispersoids Fabricated by Squeeze Casting Technique

The effect of ZrO2 (2, 4, 6 and 8 wt%) dispersoids with 1 wt% graphite on the microstructural, mechanical properties on squeeze cast VAL12 matrix hybrid composite is investigated in the present study. The hybrid composites were characterized using advanced characterization techniques to reveal its microstructural and physical properties. The microscopic examinations using optical and SEM technique reveal that the addition of dispersoids accelerates the nucleation kinetics, thus attaining fine, equiaxial grains in hybrid composites. The squeeze cast composites show almost nil porosity, defects and owing to it, the actual density of the composites are found to be more than 95% as that of the theoretical density values. The hardness values and tensile values increase with respect to the increase in percentage addition of ZrO2. The tensile results show that there is an appreciable increase in the UTS values of composites without much loss in its ductility as the addition of graphite improves the self-lubricating property and provides wettability during the casting. Fractographic studies on tensile tested specimen reveal that the crack occurs in both matrix and particles showing the good interface between matrix and dispersoids. Machinability studies reveal the formation of continuous chips in hybrid composites with a lower percentage of reinforcement (up to 4% ZrO2 + 1%Gr) and segmented chips in case of the composite with 8% ZrO2 + 1%Gr, as the increase in the percentage of dispersoids improve the chip breakability of the composites. On an overall, the hybrid aluminium matrix composites with 1%Gr and 6 % ZrO2 unveiled better optimal results.

Fast-setting and anti-washout tricalcium silicate/disodium hydrogen phosphate composite cement for dental application

Although Mineral trioxide aggregate (MTA) has been widely used in endodontic treatments and gained great clinical success, development of fast-setting tricalcium silicate (TCS)-based cements with good anti-washout performance remains a huge challenge. Hence, this study was aimed at engineering a novel TCS-based endodontic material to meet abovementioned requirements via introduction of disodium hydrogen phosphate (Na2HPO4) as the hydration accelerator. The setting time, flowability, mechanical strength and anti-washout property of the composite cements were evaluated. Furthermore, bioinert ZrO2 was used as radiopacifier and the effects of ZrO2 content on the radiopacity, physicochemical properties, apatite-formation ability, pH, antibacterial activity, cement-dentin interface and cell cytocompatibility of radiopaque composite cements with an optimal component were also investigated. The results showed that the setting time of cement pastes notably shortened from 169 to 33 min with adjusting the amount of Na2HPO4 from 0 to 30 wt%, whereas flowability and compressive strength of cements exhibited a decreasing trend. Meanwhile, cement pastes displayed good anti-washout performance because of acceleratory effect of Na2HPO4 on hydration process of TCS and formation of additional binding phase. Furthermore, the radiopacity of hybrid cements obviously enhanced with the addition of ZrO2 while a little increase in setting time was observed, and washout resistance of composite pastes was slightly reduced with the increase in ZrO2 amount. The radiopaque composite pastes could induce apatite deposition on their surfaces and showed good marginal adaptation at cement-dentin interface. Additionally, the addition of ZrO2 content had no significant influences on alkaline formation ability, antibacterial activity, and cell cytocompatibility of cement pastes. Our results indicated that TCS/Na2HPO4/ZrO2 cement exhibited a great potential to be used as a novel dental material and might be a promising candidate for endodontic treatments.

Chemical Looping Hydrogen Generation over Ceria/Zirconia-Enhanced NiO–NiFe2O4 Oxygen Carrier

The objective of this paper is to systematically investigate the influences of different metal modification on the performance of Ni-ferrite as oxygen carrier (OCs) in chemical looping hydrogen (CLH) production. Ni-ferrite OCs were modified with single-metal NiO, bimetallic NiO/ZrO2, and bimetallic NiO/CeO2. The sample was characterized by CO thermogravimetric analysis, X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller method. The results showed that NiO could promote the release of oxygen from Ni-ferrite, and the release of oxygen can reach about 99% at 800 °C. The addition of ZrO2 and CeO2 could further increase the oxygen release rate of the oxygen carrier, but the oxygen storage amount would decrease. However, the bimetallic modified OCs exhibited higher hydrogen yield, and the hydrogen yields of NiO/ZrO2- and NiO/CeO2-modified Ni-ferrite could reach 9800.0 and 8786.2 μmol g(OC)–1, respectively. Furthermore, the bimetallic modified oxygen carrier showed higher structural stability, in which the ZrO2 particles weaken the active particle contact by coating effect, while the CeO2 is mixed into the active particles to form steric hindrance, both of which can inhibit the sintering of the oxygen carrier to maintain structural stability. Finally, the oxygen carrier reaction mechanism is analyzed, and the results show that the oxygen atoms around Ni2+ first migrate through the existing vacancies. And the residual vacancies provided the space for the immigration of other nearby oxygen atoms, which enhanced migration velocity. Moreover, Fe3+ gradually transferred to the adjacent Ni2+ to generate Fe0.64Ni0.36 after its oxygen migration.

Microstructure, properties and oxidation behavior of MoSi2-MoB-ZrO2 coating for Mo substrate using spark plasma sintering

MoSi2-MoB-ZrO2 composite powders are one-step synthesized prepared by self-propagating high-temperature synthesis (SHS), which are further utilized to prepare the oxidation protective coatings by spark plasma sintering (SPS) method on molybdenum substrate. Microstructure and properties of the coatings were investigated and determined. Oxidation behavior of the coatings at high temperature was also studied. The results showed that the composite coating is dense and crack-free due to the addition of ZrO2, which is beneficial for the decrease of mismatch in coefficient of thermal expansion, and no void exists in the diffusion layer owing to the diffusion of Si, which is inhibited by adding MoB. Compared with the pure MoSi2 coating, the high hardness of the composite coating is enhanced by about 20% while the fracture toughness of the composite coating is improved by about 25%, which makes the occurrence of intergranular fracture, crack deflection and crack bridging. After oxidation at 1400 °C for 80 h, MoSi2 coating failed while xMoSi2-MoB-3ZrO2 (x = 3, 4, 5) composite coating still kept its protective effect. Only a little substrate is consumed during oxidation and improved oxidation resistance is gained by MoSi2-MoB-ZrO2 composite coating. 3MoSi2-MoB-3ZrO2 coating shows the relatively best oxidation resistance due to the formation of crack-free oxide film on the surface of the coating.

Fabrication of Cr based electrodeposited composite film using nano ZrO2 particles on aluminum substrate

In this study, the coating method suitable for producing high-quality film on aluminum substrate was investigated by using different surface treatment to each specimen before electrodeposition. Microstructure of coating cross section was observed with Electron Prove Micro Analyzer (EPMA). Vickers hardness of coating surface was measured. The measurement of polarization behavior of aluminum in CrO3-H2SO4 electrolyte with ZrO2 addition was carried out to investigate corrosion resistance. The addition of ZrO2 particles increased Vickers hardness of Cr coating. The existence of Zr in the coating was confirmed by point analysis from coating cross section. Polarization point was shifted higher by dispersing ZrO2 particles into the plating bath, and this means that corrosion resistance was improved by the addition of ZrO2 particles.

TiO2-ZrO2 membranes of controlled pore sizes with different Ti/Zr ratios for nanofiltration

TiO2-ZrO2 colloidal and polymeric sols were successfully prepared using the sol-gel method. The effects of aging and Ti/Zr molar ratios on TiO2-ZrO2 sols and powders were investigated. The particle size of colloidal sols was decreased with an increase in aging time, while the particle size of the polymeric sols increased. TiO2-ZrO2 polymeric sols with Ti/Zr molar ratios that varied from 10/0 to 0/10 showed an increase particle size with an increase in the Zr-content. In addition, TiO2-ZrO2 powders derived from colloidal sols had a crystalline structure even without firing. With firing at temperatures that approached 500 °C, however, TiO2-ZrO2 powders derived from polymeric sols had a structure that was more amorphous than that of pure TiO2 and ZrO2 powders, but the most amorphous structure was achieved at a Ti/Zr molar ratio of 5/5. TiO2-ZrO2 nanofiltration (NF) membranes, which were prepared by coating colloidal and polymeric sols onto α-Al2O3 porous supports, showed an average pore size and molecular weight cut-offs (MWCOs) in the NF range. Average pore size, N2 permeance, water permeability (Lp), and MWCOs of the membranes were generally decreased with an increase in ZrO2 content with an optimum addition of ZrO2 that approached an equimolar composition. TiO2-ZrO2 (9/1, 7/3, 5/5) membranes showed a relatively low MWCO and a moderate Lp, which suggested that these membranes would be good for nanofiltration.

Structural and corrosion behavior of Ni-Cu and Ni-Cu/ZrO2 composite coating electrodeposited from sulphate-citrate bath at low Cu concentration with additives

Ni-Cu and Ni-Cu/ZrO2 composite coatings were electrodeposited by addition of Cu, Cu and ZrO2 in Ni deposit from a sulphate-citrate bath at low Cu concentration with additives. Effects of the added Cu atoms and zirconia (ZrO2) particles on surface morphology and structural properties of Ni matrix were examined with various methods. The effects of deposition parameters like current density, duty cycle and their combination on corrosion behavior of Ni-Cu/ZrO2 coating were examined. The hardness was evaluated by Vickers hardness tester. Results indicated that the presence of Cu and ZrO2 changes the texture of nickel and reduces its crystallite size. The corrosion resistance of Ni deposit has been enhanced by the formation of Ni-Cu or Ni-Cu/ZrO2 composite coating. The average roughness values (Ra) of the Ni-Cu, Ni-Cu/ZrO2 coating is about 4–5 nm, 16–20 nm, respectively, indicating the rougher surface of Ni-Cu/ZrO2 in comparison with Ni-Cu alloy. Ni-Cu/ZrO2 composite coating presents higher hardness than Ni and Ni-Cu alloys. It was found that not only the current density, duty cycle, but also their combination affects the corrosion properties of the composites. Compared to others, Ni-Cu/ZrO2 coating electrodeposited at duty cycle of 30% has the highest impedance value. Also, the higher corrosion-resistant property of Ni–Cu/ZrO2 composites were obtained under the parameter combination of 3 A dm−2, 80% and 8 A dm−2, 40% in comparison with other parameter combination.

Tribological Characterization of Iron Based Ceramic Reinforced Self- lubricating Material

In this paper, the effect of ZrO2 reinforcement and MoS2 as solid lubricant on tribological properties of iron-copper-tin composite for plain bearing application have been investigated. This paper includes two studies, one in which wt% of MoS2 is varied keeping wt% of ZrO2 constant and in another wt% of ZrO2 is varied keeping wt% of MoS2 constant to see the effect of ZrO2 as reinforcement and MoS2 as a solid lubricant for improving tribological properties of sintered Fe-Cu-Sn material. The material was prepared by sintering at temperature of 1150° C. The tribological properties of developed materials were analysed by ball on disk test.Least value of COF 0.0421 is shown by sample with 2 wt.% of MoS2 and 2 wt.% of ZrO2. Least wear rate of 0.4581x10-4 mm\\Nm for sample with 2 wt.% of MoS2 and 2 wt.% ZrO2.Characterization of worn surfaces revealed abrasive and adhesive wear including third body abrasive wear, delamination and micro-ploughing in reinforced composites. The addition of MoS2 has improved tribological properties, whereas ZrO2 addition not only improved tribological properties, but also improved strength and hardnessof the composite. Maximum hardness value 208HV (701.4MPa) is shown by the composite with 2 wt.% of MoS2 and 2 wt. % of ZrO2. The findings show that the developed material could be used for antifriction andantiwear plain bearing applications.

Microstructure and oxidation resistance of spark plasma sintered Yttria-Zirconia ODS steels

In this experiment, the effect of Y2O3 and ZrO2 additions on the microstructure and cyclic oxidation resistance of 17-Cr ODS steel containing Al consolidated using spark plasma sintering method were studied. In addition, density, porosity and hardness were also observed. Four compositions of ferritic steels as Fe-17Cr-3.5Al-Ti-Y (‘FP’), Fe-17Cr-3.5Al-Ti-Y-0.4Y2O3 (‘FY’), Fe-17Cr-3.5Al-Ti-Y-0.4ZrO2 (‘FZ’), and Fe-17Cr-3.5Al-Ti-Y-0.2Y2O3-0.2ZrO2 (‘FYZ’) were prepared by mechanical alloying and followed by sintering at 1000 °C. Microstructure characteristics were observed for different aspect, viz. elemental distribution, composition, and phase identification. Cyclic oxidation tests were carried out at 800 °C for 8 cycles. The results show that ZrO2 addition suppresses the formation of Y-Al-O clustering and promotes the formation of Y-Zr-O clustering and the enhancement of oxidation resistance of the alloy. However, in some condition it also has a deleterious effect on crack resistance. In contrast, the addition of Y2O3 decreases the oxidation resistance but increases the hardness.

An investigation of equibiaxial flexural strength and hardness properties of Al2O3–Ni nanocomposites based microstructures with ZrO2 and Cr2O3 additives

The investigation of new ceramics and ceramic composites to overcome the inadequacies of monolithic ceramics without using costly techniques and equipment is essential for developing ceramic armor components. The aim of the research was analyzing the mechanical properties (elastic modulus, flexural strength, and hardness) of Al2O3/1 vol% Ni nanocomposites with 5 vol% ZrO2 or 1 vol% Cr2O3 additives and estimating their performance by comparing with the pure Al2O3, Al2O3/ZrO2 composite, and Al2O3/Cr2O3 ceramic system for armor applications. The heterogeneous precipitation method was used to obtain nano-sized metal particles in the ceramic matrix for the Ni-containing compositions. Equibiaxial flexural tests were conducted for strength measurements and stored energy at failure was estimated by using the theoretical deflection of the cylindrical plate; also, post-failure total crack lengths were measured. Simultaneous addition of Ni and ZrO2 on Al2O3 matrix resulted in the highest hardness (25.5 ± 1.0 GPa) and flexural strength (367 ± 34 MPa) compared to other compositions because of the hardening effect of Ni and the grain boundary strengthening mechanism. Moreover, this composition showed the highest resistance to fragmentation as evidenced by the shortest crack length per stored energy at failure. Cr2O3 addition also provided remarkable results related to the solid solution formation for both the pure Al2O3 and Al2O3/Ni composites. By this comparative study, different compositions with high mechanical properties have been introduced as the potential candidates to be used in armor applications with static tests giving an indication about ballistic performance.

Sol–gel synthesis of precursors and preparation of ceramic composites based on LaPO4 with Y2O3 and ZrO2 additions

Nanosized powders as precursors have been synthesized via sol–gel technique to prepare ceramic composites in the LaPO4–Y2O3 and LaPO4–ZrO2 systems through normal sintering. Sol–gel technique was based on separate synthesis of LaPO4·nH2O, Y(OH)3, and ZrO(OH)2 components as sol using “reverse precipitation” (or “reverse flocculation”) technique, and further mixing them together to prepare (1‒x)LaPO4·nH2O–xY(OH)3 and (1‒x)LaPO4·nH2O–xZrO(OH)2 compositions as gels. During sol–gel synthesis, formation of hexagonal LaPO4·nH2O and Y(OH)3 or monoclinic ZrO(OH)2 was observed. As-prepared precursors of nanosized powders were then calcined at 850 °C for dehydration of the components and decomposition of yttrium and zirconium hydroxides to obtain nanosized (1‒x)LaPO4–xY2O3 and (1‒x)LaPO4–xZrO2 compositions, where x did not exceed 0.20 mole fraction. Ceramic composites were prepared by sintering these compositions subsequently at 1000, 1200, and 1300 °C for 24 h. Vickers microhardness was found to depend on x and sintering temperature. The influence of yttria and zirconia additions on dispersion of powders, their thermal behavior, specific surface area and ceramic fracture surface of the composites, and their open porosity was discussed.