Transparent thin films of pure and nickel-doped ZrO2 are grown successfully by sol-gel dip-coating technique. The structural and optical properties according to the different annealing temperatures (300 oC, 400 oC and 500 oC) are investigated. Analysis of crystallographic properties through X-ray diffraction pattern reveals an increase in crystallite size due to increase in crystallinity with temperature. All fabricated thin films are highly-oriented along (101) planes, which enhances the increase in nickel doping. Scanning electron microscopy and energy dispersive spectroscopy are employed to confirm the homogeneity in surface morphology as well as the doping configuration of films. The extinction coefficient is found to be on the order of 102, showing the surface smoothness of deposited thin films. UV-visible spectroscopy reveals a decrease in the optical band gap with the increase in annealing temperature due to the increase in crystallite size. The variation in Urbach energy and defect density with doping and the change in annealing temperature are also studied.

Effect of sulfation processes on the physicochemical properties of ZrO2 and TiO2 nanoparticles were thoroughly investigated. SO4/ZrO2 and SO4/TiO2 catalysts were synthesized to identify the acidity character of each. The wet impregnation method of ZrO2 and TiO2 nanoparticles was employed using H2SO4 with various concentrations of 0.5, 0.75, and 1 M, followed by calcination at 400, 500, and 600 °C to obtain optimum conditions of the catalyst synthesis process. The highest total acidity was found when using 1 M SO4/ZrO2-500 and 1 M SO4/TiO2-500 catalysts, with total acidity values of 2.642 and 6.920 mmol/ g, respectively. Sulfation increases titania particles via agglomeration. In contrast, sulfation did not practically change the size of zirconia particles. The sulfation process causes color of both catalyst particles to brighten due to the presence of sulfate. There was a decrease in surface area and pore volume of catalysts after sulfation; the materials’ mesoporous structural properties were confirmed. The 1 M SO4/ZrO2 and 1 M SO4/TiO2 catalysts calcined at 500 °C are the best candidate heterogeneous acid catalysts synthesized in thus work.

In this study, a chlorination technique for recycling Li2ZrO3, a reaction product of ZrO2-assisted rinsing process, was investigated to minimize the generation of secondary radioactive pyroprocessing waste. It was found that the reaction temperature was a key parameter that determined the reaction rate and maximum conversion ratio. In the temperature range of 400−600℃, an increase in the reaction temperature resulted in a profound increase in the reaction rate. Hence, according to the experimental results, a reaction temperature of at least 450℃ was proposed to ensure a Li2ZrO3 conversion ratio that exceeded 80% within 8 h of the reaction time. The activation energy was found to be 102 ± 2 kJ·mol−1·K−1 between 450 and 500℃. The formation of LiCl and ZrO2 as reaction products was confirmed by X-ray diffraction analysis. The experimental results obtained at various total flow rates revealed that the overall reaction rate depends on the Cl2 mass transfer rate in the experimental condition. The results of this study prove that the chlorination technique provides a solution to minimize the amount of radioactive waste generated during the ZrO2-assisted rinsing process.

A stacked high-voltage (900 V) Al electrolytic capacitor made with ZrO2 coated anode foils, which has not been studied so far, is realized and the effects of Zr-Al-O composite layer on the electric properties are discussed. Etched Al foils coated with ZrO2 sol are anodized in 2-methyl-1,3-propanediol (MPD)-boric acid electrolyte. The anodized Al foils are assembled with stacked structure to prepare the capacitor. The capacitance and dissipation factor of the capacitor with ZrO2 coated anode foils increase by 41 % and decrease by 50 %, respectively, in comparison with those of Al anode foils. Zr-Al- O composite dielectric layer is formed between separate crystalline ZrO2 with high dielectric constant and amorphous Al2O3 with high ionic resistivity. This work suggests that the formation of a composite layer by coating valve metal oxide on etched Al foil surface

This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated ZrO2 ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated ZrO2 particles are observed by FE-TEM and FT-IR. The rheological properties of VTEScoated ZrO2/High-temp composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3Dprinted objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated ZrO2 ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.

Cordierite composed of an alumina-silica-magnesia compound has a low coefficient of thermal expansion(CTE) and excellent thermal shock resistance. It also has a low dielectric constant and high electrical insulation. However, due to low mechanical strength, it is limited for use in a ceramic heater. In this study, ZrO2 is added to an 80 wt% cordierite-20 wt% mullite composition, and the effect of ZrO2 addition on the mechanical strength and thermal shock resistance is investigated. With an increasing addition of ZrO2, cordierite-mullite formed ZrO2, ZrSiO4 and spinel phases. With sintering conducted at 1400 °C with the addition of 5 wt% ZrO2 to 80 wt% cordierite-20 wt% mullite, the most dense microstructure forms along with an excellent mechanical strength with a 3-point flexural strength of 238MPa. When this composition is quenched in water at ΔT = 400℃ , the 3-point flexural strength is maintained. Moreover, when this composition is cooled from 800℃ to air, the 3-point flexural strength is maintained even after 100 cycles. In addition, the CTE is measured as 3.00 × 10−6·K−1 at 1000℃ . Therefore, 80 wt% cordierite-20 wt% mullite with 5 wt% ZrO2 is considered to be appropriate as material for a ceramic heater.

ZrO2 is a candidate material for hip and knee joint replacements because of its excellent combination of biocompatibility, corrosion resistance and low density. However, the drawback of pure ZrO2 is a low fracture toughness at room temperature. One of the most obvious tactics to cope with this problem is to fabricate a nanostructured composite material. Nanomaterials can be produced with improved mechanical properties(hardness and fracture toughness). The high-frequency induction heated sintering method takes advantage of simultaneously applying induced current and mechanical pressure during sintering. As a result, nanostructured materials can be achieved within very short time. In this study, W and ZrO2 nanopowders are mechanochemically synthesized from WO3 and Zr powders according to the reaction(WO3 + 3/2 Zr→W+ 3/2 ZrO2). The milled powders are then sintered using high-frequency induction heating within two minutes under the uniaxial pressure of 80MPa. The average fracture toughness and hardness of the nanostructured W-3/2 ZrO2 composite sintered at 1300oC are 540 kg/mm2 and 5 MPa·m1/2, respectively. The fracture toughness of the composite is higher than that of monolithic ZrO2. The phase and microstructure of the composite is also investigated by XRD and FE-SEM.

본 연구에서는 투명도와 기계적 특성을 향상시키기 위해 저온 공정의 졸-겔 법을 이용하여 하이브리드 복합체의 코팅 박막을 제조하였다. 하이브리드 복합체로는 ZrO2/TiO2/organosilane을 사용하였으며, 그 중 organosilane은 3-(trimethoxysilyl)propyl methacrylate을 사용하였고 이는 저온 공정의 광경 화 반응을 위해 도입되었다. 다양한 조성비로 합성된 복합체를 폴리 카보네이트 기판 위에 저온 공정의 졸 -겔 법을 이용하여 광경화와 열처리 공정을 거처 코팅 박막을 제조하였고 이 코팅 박막의 광학 특성 및 기계적 강도를 확인하였다. 코팅 박막은 가시광선 영역에서 97.5 % 이상의 투과도를 가짐을 확인하였고 기계적 강도는 9H 이상의 연필 경도를 가진 것을 확인하였다. 특히 ZTS-2-1 코팅 박막의 나노 압입 경도는 1.14 GPa로 가장 높게 측정되었다.

In this study, ZrO2 ceramic ink was formulated for additive manufacturing three dimensional structure using dispenser printing technique. Ceramic ink with various ZrO2 loading (30, 40, 50vol%) was prepared to evaluate their rheological properties and printability. High ZrO2 loading ZrO2 ceramic ink showed higher elastic modulus and improved shape retention, when the ceramic ink was printed and sintered at 1450 oC for 1h. Microstructural analysis of printed ZrO2 objective indicated that high ZrO2 loading objective showed lower porosity and smaller pore size.

YSZ (Yttria-stabilized zirconia) is a ceramic material that is used for electronic and structural materials due to its excellent mechanical properties and specific electrical characteristics according to the Yttrium addition. Hydrothermal synthesis has several advantages such as fine particle size, uniform crystalline phase, fast reaction time, low process temperature and good dispersion condition. In order to synthesize YSZ nanoparticles with high crystallinity, hydrothermal synthesis was performed at various concentrations of NaOH. The hydrothermal process was held at a low temperature (100 °C), with a short process time (2,4,8 hours); the acidity or alkalinity of solution was controlled in a range of pH 2~12 by addition of NaOH. The optimum condition was found to be pH 12, at which high solubility levels of Y(OH) and Zr(OH) were reported. The synthesized nano powder showed high crystallinity and homogenous composition, and uniform particle size of about 10 nm.

Inorganic phosphors based on ZrO2:Eu3+ nanoparticles were synthesized by a salt-assisted ultrasonic spray pyrolysis process that is suitable for industrially-scalable production because of its continuous nature and because it does not require expensive precursors, long reaction time, physical templates or surfactant. This facile process results in the formation of tiny, highly crystalline spherical nanoparticles without hard agglomeration. The powder X-ray diffraction patterns of the ZrO2:Eu3+ (1-20 mol%) confirmed the body centered tetragonal phase. The average particle size, estimated from the Scherrer equation and from TEM images, was found to be approximately 11 nm. Photoluminescence (PL) emission was recorded under 266 nm excitation and shows an intense emission peak at 607 nm, along with other emission peaks at 580, 592 and 632 nm which are indicated in red.

2ZrO2·P2O5 powder, which is not synthesized by solid reaction method, was successfully synthesized through PVA solution method. In this process, the firing temperature and the PVA content strongly affected the crystallization behavior and final particle size. A stable α-phase 2ZrO2·P2O5 was synthesized at a firing temperature of 1200 oC and holding time of 4 h. β-phase 2ZrO2·P2O5 was observed, with un-reacted ZrO2 phases, for firing temperatures lower than 1200 oC. In terms of the PVA content effect, the powder prepared with a PVA mixing ratio of 12:1 showed stable α-phase 2ZrO2·P2O5; however, the β-phase was found to co-exist at relatively higher PVA content. The synthesized α-phase 2ZrO2·P2O5 powder showed an average particle size of 100~250 nm and an average thermal expansion coefficient of −2.5 × 10−6/oC in the range of room temp. ~800 oC.

Transparent organic-inorganic hybrid hard coating films were prepared by the addition of SiO2 or ZrO2, as an inorganic filler to improve the hardness property, filler was highly dispersed in the acrylic resin. To improve the compatibility in the acrylic resin, SiO2 or ZrO2 is surface-modified using various silanes with variation of the modification time and silane content. Depending on the content and kind of the modified inorganic oxide, transparent modified inorganic sols were formulated in acryl resin. Then, the sols were bar coated and cured on PET films to investigate the optical and mechanical properties. The optimized film, which has a modified ZrO2 content of 4 wt% markedly improved in terms of the hardness, haze, and transparency as compared to neat acrylate resin and acrylate resin containing modified SiO2 content of 8 wt%. Meanwhile, the low transparency and high haze of these films slowly appeared at SiO2 content above 10 wt% and ZrO2 content of 5 wt%, but the hardness values were maintained at 2H and 3H, respectively, in comparison with the HB of neat acrylate resin.

To increase the capacitance of an Al electrolytic capacitor, the anodic oxide film, Al2O3, was partly replaced by an Al2O3-ZrO2 (Al-Zr) composite film prepared by the vacuum infiltration method and anodization. The microstructure and composition of the prepared samples were investigated by scanning electron microscopy and transmission electron microscopy. The coated and anodized samples showed multi-layer structures, which consisted of an inner Al hydrate layer, a middle Al- Zr composite layer, and an outer Al2O3 layer. The thickness of the coating layer could go up to 220 nm when the etched Al foil was coated 8 times. The electrical properties of the samples, such as specific capacitance, leakage current, and withstanding voltages, were also characterized after anodization at 100 V and 600 V. The capacitances of samples with ZrO2 coating were 36.3% and 27.5% higher than those of samples without ZrO2 coating when anodized at 100 V and 600 V, respectively.

Lanthanum zirconate, La2Zr2O7, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a La2Zr2O7-4YSZ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.

The oxide films formed on etched aluminum foils play an important role as dielectric layers in aluminum electrolytic capacitors. Y2O3-doped ZrO2 (YZ) films were coated on the etched aluminum foils by sol-gel dip coating, and the electrical properties of YZ-coated Al foils were characterized. YZ films annealed at 450 oC were crystallized into a cubic phase, and as the Y2O3 doping content increased, the unit cell of ZrO2 expanded and the grain size decreased. The etch pits of Al foils were filled by YZ sol when it dried at atmospheric pressure after repeating for several times, but this step could essentially be avoided when being dried in a vacuum. YZ-coated foils indicated that the specific capacitance and dissipation factor were 2-2.5 μF/cm2 and 2-4 at 1 kHz, respectively, and the leakage current and withstanding voltage of films approximately 200 nm thick were 5 × 10−4A at 21 V and 22 V, respectively. After being anodized at 500 V, the foils exhibited a specific capacitance and dissipation factor of 0.6-0.7 μF/cm2 and 0.1-0.2, respectively, at 1 kHz, while the leakage current and withstanding voltage were 2 × 10−4 - 3 × 10−5 A at 400 V and 420-450 V, respectively. This suggests that YZ film is a promising dielectric that can be used in high voltage Al electrolytic capacitors.

The purpose of this study was to investigate the microstructures and mechanical properties of zirconia toughened alumina (ZTA) ceramics prepared from two kinds of 3Y-TZP powders. ZTA composites were prepared by adding two kinds of 3Y-TZP powders, 3YEH (BET = 7m2/g) and 3YEM (BET = 16m2/g), to α-alumina in the range of 5-25 wt%. It was found that the microstructure photographs of the ZTA composites showed that the average grain size of alumina decreased as the content of zirconia increased. In our present study, specimens containing 3YEM zirconia exhibited smaller grain sizes compared to those of 3YEH zirconia. The Vickers hardness of the ZTA composites that were sintered at 1600˚C for 2 hrs was found to smoothly decrease with increasing zirconia content because of the low Young modulus in zirconia. The Vickers hardness of the ZTA containing 3YEH zirconia was greater than that of the 3YEM zirconia. In substance, the fracture toughness (K1c) of the ZTA composites increased as the content of zirconia increased. The fracture toughness (K1c) of ZTA containing 3YEM zirconia was greater than that of 3YEH zirconia.

To increase the mechanical property of zirconia, we have investigated the phase change and the resulting hardness of zirconia ceramics by hydroxyapatite (HA) powder bed sintering. It was observed using X-ray diffraction that the cubic zirconia phase, which has a higher hardness value than that of the tetragonal phase, was obtained at the surface of 3 mol% Y2O3 doped tetragonal zirconia polycrystal (3Y-TZP) ceramics during the sintering process; in our experimental conditions, the phase change at the surface increased as the sintering time increased. We believe that the observed crystalline phase change originated from the decomposition of HA and the diffusion of CaO, as follows. CaO, which was derived from the decomposition of HA at high temperature (1400˚C), diffused into the surface of 3Y-TZP and acted as a stabilizer. As a result, the Vickers hardness value of the treated specimens was higher than that of the non-treated specimen due to the formation of the cubic phase on the surface of 3Y-TZP.