Papers by Keyword: Zro₂

Abstract: Oxidation resistance and bending strength at high temperatures of 5 vol% Ni/(10 vol% ZrO₂+Al₂O₃) were investigated in this paper. Oxidation tests were conducted at temperature ranging from 1100 to 1300oC for 1 to 24 h in air. The oxidation resistance of the composites was studied via observation of oxidized-zone development from a cross-section view after oxidation. Three-point bending tests were conducted at temperatures ranging from room temperature to 1200oC in order to estimate its performance at high temperatures. Bending strength of the composites achieved 1200 MPa at room temperature and 460 MPa at 1200oC. Dispersion of ZrO₂ in Ni/Al₂O₃ composites enhanced both their room and high temperature bending strength. Nevertheless, ZrO₂ slightly degraded the oxidation resistance of the composites. The oxidation rate of Ni/(ZrO₂+Al₂O₃) was one order of magnitude higher than that of Ni/Al₂O₃.

Abstract: The core-shell red pigment γ-Ce₂S₃@ZrO₂ was prepared by a two step method. γ-Ce₂S₃ was pre-coated at 30°C with hydrolysis, followed by hydrothermal reaction at 180 °C for further coating and crystallization. The effect of preparation method, hydrolysis dropping speed and the number of hydrothermal process on the microstructure of the ZrO₂ layer was observed. The influence of coating layer to chromaticity, heat resistance and acid stability was also investigated. The results show that a complete layer at nearly 90 nm coated on the surface of the γ-Ce₂S₃ particles. The as-prepared pigment exhibited pure red color (L* = 44.38, a* = 31.94, b* = 23.14). Moreover, this coating layer can provide protection to pigment particles. The core-shell pigment can remain red color (L* = 42.71, a* = 26.23, b* =18.38) after calcined in air at 380 °C, while uncoated pigment turned to grey dark at 360 ^oC.

Abstract: It is well known that sol-gel technique is a simple method to produce nano sized ceramic powders. In this study, cerium oxide doped zirconia samples, with 10 mol%-12mol% and14mol% CeO₂, were synthesized by sol-gel technique and characterized. The surface morphology, elemental composition, microstructure, and phase analysis, of the sintered CeO₂ doped ZrO₂ ceramics were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, and X-ray diffraction (XRD) respectively. X-ray diffraction for samples sintered at 1550 °C for 4h revealed that the zirconia ceramics have a tetragonal phase structure. The addition of CeO₂ can raise the content of the tetragonal phase, but the minor monoclinic phase exists even at the CeO₂ content of 10 mol%. The effect of dopant concentration on the lattice parameter, average primary crystallite size and micro-strain was studied. Relative densities for CeO₂ doped ZrO₂ bulk ceramics varied between 95% and 99 %, depending on the CeO₂ addition.

Abstract: The bio-composited ceramic stabilized zirconia-hydroxyapatite had been formed by ball milling method. The hydroxyapatite was synthesized from chicken eggshell via chemical precipitation. And it was mixed with stabilized zirconia powder together. All of the samples had been investigated by XRD, FTIR and UTM tester. The XRD and FTIR result showed that the stabilized zirconia-hydroxyapatite sample powder after ball mill was found only hydroxyapatite and zirconia phase without addition of other phase. High crystallinity of hydroxyapatite can be found after heat treatment and calcium zirconium oxide was formed around 1300 °C. In addition, the compressive strength increased with increasing the zirconia content shown by UTM tester.

Abstract: Hybrid nanocomposite epoxy-based coatings containing ZrO₂, ZnO and Fe₂O₃ nanoparticles (≤50nm) were deposited on Grade A naval steel substrates by dip-coating technique. The surface morphology and the mechanical properties of coated steel samples were analyzed by optical microscopy and CETR tribometer, respectively. The mechanical measurements showed that 1wt. % doping metal oxides nanoparticles significantly affect the mechanical behavior of coatings in terms of microhardness and friction coefficient. Best results were obtained in the case of Fe₂O₃ and ZrO₂ doping, for which were obtained microhardness in the range of 90-120MPa and 142 MPa, respectively. Regarding the friction coefficient, values in the range of 0.02-0.08 were obtained

Abstract: The content of ZrO₂ and TiO₂ in alkali-resistant fiberglass mesh was determined by ICP OES. The sample was pretreated by acid-soluble and alkali-fusion methods. Compared with the results of standard method, the results showed that the method can be used for the determination of ZrO₂ and TiO₂ in alkali-resistant fiberglass mesh. Standard solutions were prepared based on the content of elements. The best analysis of spectral lines was determined for each element. Blank solution was prepared and injected ten times continuously. The corresponding concentration of three times of standard deviation (3S) was used to calculate the detection limit of the method, and the detection limit was from 0.0018% to 0.0047%. The corresponding concentration of ten times of standard deviation (10S) was used to calculate the quantitation limit of the method, and the limit of quantitation was from 0.0060% to 0.016%. Six repeated tests were performed on two samples, and the relative standard deviations (RSDs (n=6)) of the test were from 0.60% to 0.78%. Compared to standard method, absolute error was less than 0.2% and the relative error was less than 2.0%. The results showed that the method can be used for simultaneous determination of ZrO₂ and TiO₂ in alkali-resistant fiberglass mesh., with fast analysis and reliable results.

Abstract: Water-based suspensions from commercial Tetragonal stabilized zirconia (3Y-TZP) were produced and characterized with different contents of solids and two different dispersants. According to zeta potential measurements, 3Y-TZP particles showed basic surface characteristics and IEP of around 9 when in aqueous media. The critical volume fraction of solids was about 79.6 wt%, which hindered the processing of more concentrated slurries. Rheological measurements confirmed that well dispersed slurries could be obtained with solid content as high as 79.6 wt.%. The results showed that Triton X-114 was an effective dispersant for preparing well stabilized 3Y-TZP suspensions for the layer-wise slurry deposition process.

Abstract: CaO–B₂O₃–SiO₂ (CBS) glass-ceramics containing ZrO₂ were prepared by conventional melting and heat treated crystallization method. The effects of ZrO₂ on the crystallization behavior, sintering characterization and dielectric properties of the glass-ceramics were analyzed respectively. The results indicated that ZrO₂ addition can improve the crystallization and densification of CBS glass-ceramics. The major crystallized phase of sample with≥7wt% ZrO₂ was cyclowollastonite (α-CaSiO₃).It is found that the optimal sintering condition for the glass-ceramics is 770 ^oC for 30min. CBS glass ceramics sample with 7wt% ZrO₂ shows the best sintering characterization and dielectric properties (ρ= 2.71g/cm³, ε_r ≈8.8,tan δ=2.36×10^-3 at 1 MHz), which is supposed to be suitable for LTCC application.

Abstract: A kind of ceramic composite consisted of Mg-Y co-doped ZrO₂ and MgAl₂O₄ was prepared as candidate material to replace the high destiny graphite crucible which was often used in nuclear industry. When the addition of MgAl₂O₄ was 7 wt%, samples with good thermal shock resistance were obtained. The obtained samples were tested up to 12 h in molten uranium, and no apparent cracks were found on the corrosion surface. Meanwhile, the corrosion rate decreased significantly from 30 mg·cm^-2·h^-1 to 3 mg·cm^-2·h^-1 as the corrosion time prolonged from 2 h to 12 h due to the formation of a protection layer consisted of UO₂, Al₃Zr₂ and ZrC during the uranium corrosion test. These results suggested that the ceramic composite prepared in this study owned both good corrosion resistance to the molten uranium and thermal shock resistance at high temperatures,so it’s a high potential material to replace the high density graphite crucible in nuclear industry.

Abstract: Alumina-zirconia (Al₂O₃-ZrO₂) composite ceramics were prepared by means of cross spraying and hydrothermal method under atmospheric pressure with nanometer powders doped with ZrO₂ as the raw material. Then, the prepared powders and ceramics were characterized by SEM, XRD and BET methods. The results showed that combining cross spraying with hydrothermal method under atmospheric pressure could improve the dispersity of the ZrO₂ composite ceramics nanopowders_, while adding Al₂O₃ accelerated the low temperature sintering for 3Y-ZrO₂ and improved the bending strength, fracture toughness and density of ZrO₂ composite ceramics. In addition, through optimization the bending strength and fracture toughnessof the obtained ceramic, were 1,150 MPa and 8.2 MPa∙m^1/2 respectively.