Effect of aluminum addition on microstructure and properties of SiO<Subscript>2</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO vitrified bond

Influence of aluminum addition on the structures and properties of SiO₂-B₂O₃-Al₂O₃-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 °C were observed by scanning electron microscope (SEM). The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10^-6 °C^-1, respectively.     

Effect of ZrO<Subscript>2</Subscript> dopant on the sintering behavior and performance of mcmb-derived carbon laminations

Liquid ball-milling dispersant method was used to prepare the ZrO2-doped carbon laminations from mesocarbon microbeads(MCMBs). After sintering at 1 300 ℃ in nitrogen atmosphere, the effect of ZrO2 concentration on sintering behavior, electric conductivity as well as bending strength of the carbon laminations was investigated in detail. The results showed that the volumetric shrinkage rate of the carbon laminations decreased from 38.2% to 30.9% when the ZrO2 concentration in raw materials varied from 0 to 16...     

Effects of Adhesive Composition on Green Joining of CePO4-ZrO2 Ceramics

Green bodies of 25% CePO4/ZrO2 and ZrO2 ceramics were joined at 1450℃ for 120 min without applied pressure by using mixed powders slurries composed of CePO4 and ZrO2. The effects of CePO4/( CePO4 ZrO2 ) ratio of the adhesive on the bond strength of the joints were investigated. Maximum bond strength of 414 MPa was obtained by joining an adhesive with the ratio of 0. 5 Under the experimental conditions, the grain size of the particles grown in the joint was smaller than that in joined ceramics. The microstructure of the joint was more homogeneous than that of the matrix and without obvious crack, pores and other defects.     

Valence electron structure and properties of stabilized ZrO2

To reveal the properties of stabilizers in ZrO₂ on nanoscopic levels, the valence electron structures of four stable ZrO₂ phases and c-ZrO₂ were analyzed on the basis of the empirical electron theory of solids and molecules. The results showed that the hybridization levels of Zr atoms in c-ZrO₂ doped with Ca and Mg dropped from B17 to B13, the hybridization levels of Zr atoms in c-ZrO₂ doped with Y and Ce dropped from B17 to B15, and that the four stabilizing atoms all made the hybridization levels of O atoms drop from level 4 to level 2. The numbers of covalent electrons in the strongest covalent bond in the descending order are c-ZrO₂>Zr_0.82Ce_0.18O₂>Zr_0.82Y_0.18O_1.91>Zr_0.82Mg_0.18O_1.82>Zr_0.82Ca_0.18O_1.82. The bond energies of the strongest covalent bond and the melting points of the solid solutions in the descending order are Zr_0.82Ce_0.18O₂> c-ZrO₂>Zr_0.82Y_0.18O_1.91>Zr_0.82Mg_0.18O_1.82>Zr_0.82Ca_0.18O_1.82. The percentages of the total number of covalent electrons in the descending order are c-ZrO₂>Zr_0.82Y_0.18O_1.91> Zr_0.82Ce_0.18O₂>Zr_0.82Mg_0.18O_1.82> Zr_0.82Ca_0.18O_1.82. From the above analysis, it can be concluded that the stabilizing degrees of the four stabilizers in the descending order are CaO> MgO>Y₂O₃>CeO₂. Supported by the Major Project of the National Natural Science Foundation of China (Grant No. 90505015)     

Synthesis and photocatalytic property of the ZrO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> pillared laponite

The ZrO2/TiO2 pillared laponite (Ti-Zr-lap) photocatalysts were prepared with intercalation reaction by supercritical fluid drying (SCFD),and characterized by XRD,TEM,SEM and BET surface area analysis,and the photocatalytic properties of Ti-Zr-lap were investigated by degradation of azo dye acid red B (ARB).The results showed that the ZrO2/TiO2 pillared structures in laponite could be formed,with the mass fraction of (Zr4++Ti4+)/laponite (Xm) increasing,the basal spacing and the BET surface area of Ti-Zr-lap significantly increased.The Ti-Zr-lap used as photocatalyst had the advantages of stable and porous layered structure,large surface area with the anatase type TiO2.Compared with the Ti-Zr-lap dried by air drying,the Ti-Zr-lap dried by SCFD showed better photocatalytic property which was very close to that of P25 TiO2.Using the Ti-Zr-lap as photocatalyst with the optimum Xm of 0.16 and the calcination temperature of 500 ℃,under the conditions of the initial concentration of ARB 20 mg/L,photocatalyst concentration of 1.5 g/L and irradiation time 60 min,the decoloring rate of ARB could achieve 98.3%,indicating that the Ti-Zr-lap had excellent photocatalytic property.     

Influence of heat treatment temperature on microstructure and bonding of TiO<Subscript>2</Subscript> film coated on diamond particles surface

TiO₂ films were coated on the surface of diamond particles using a sol-gel method. The effects of heat treatment temperature on the morphology, phase composition and chemical bond of diamond particles coated with TiO₂ films were investigated through SEM, TEM, X-ray diffraction analysis, Raman spectroscopy, FTIR, and XPS. The results showed that when being heat-treated at 600 °C, the amorphous TiO₂ film transfered to the anatase film which bonded well with diamond substrate. Meanwhile, the Ti-O-C bond formed between TiO₂ film and diamond substrate. When being heat-treated at 800 °C, TiO₂ film was still anatase, and partial diamond began to graphitize. The graphitizated carbon could also form the Ti-O-C bond with TiO₂ film, although TiO₂ film would tend to crack in this case.     

Effects of Excess Barium on the Structure and Electrical Properties of (Ba,Ca)TiO<Subscript>3</Subscript> Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba_0.925Ca_0.075TiO₃ lead-free piezoelectric ceramics (abbreviated as BCT) with high mechanical quality factor were synthesized by conventional solid-state reaction method. The effects of excess Ba on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. X-ray diffraction and Raman spectra revealed that Ca²⁺ ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol% extra Ba²⁺ ions were added after sintering. The grain size of the ceramics was decreased by adding extra Ba²⁺ ions. The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%. High piezoelectric coefficients ( d₃₃ = 150–190 pC/N ) and high mechanical quality factors ( Q_m = 1 000–1 200 ) were obtained in the ceramics when the excess of Ba was between 0.5 mol% and 1 mol%. These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.     

Dielectric properties and electrical conductivity of CaCu3Ti4O12 ceramics doped with Zr4+

CaCu₃Ti₄O₁₂ (CCTO) ceramics doped with Zr⁴⁺ were prepared. Effects of Zr⁴⁺ on microstructure, dielectric properties and conduction behavior of CaCu₃Ti_4?x Zr _x O₁₂ (x=0, 0.05, 0.10, 0.20) ceramics were studied in the frequency range of 10–10⁶ Hz. Grain size and dielectric loss of Zr⁴⁺-doped CCTO ceramic decreased compared with pure CCTO. The loss tangent (tanδ) of CaCu₃Ti_4?x Zr _x O₁₂ (x=0.20) ceramic droped to 0.05 at a frequency of 1 kHz, which was reduced by 55% compared with pure CCTO ceramic. The mechanism effect of electrical conductivity on dielectric loss of Zr⁴⁺-doping CCTO ceramics was also discussed.     

Strengthening-toughening of ceramics by metal elements recovered from electroplating sludge

Co-precipitation compound precursors-hydrothermal processing was employed to synthesize Ni/Cu/Al₂O₃/ZrO₂ composite powder, and ZrO₂-based composite ceramics was prepared. The technology recycled the metal of nickel, copper and aluminum from sludge, and the recovery rate of nickel was up to 95.5%. The property of ZrO₂-based composite ceramics was improved because of the existence of nickel and copper particles. The fracture toughness of Ni/Cu/Al₂O₃/ZrO₂ composite ceramics was 8.52 MPa·m^1/2 and the compressive strength was 51 MPa, showing the increase by 2.54 times and 1.5 times, respectively, compared with those of pure ZrO₂ ceramics.     

Preparation and Performance of Magneto-optical Glasses Doped with Tb3＋/Dy3＋

In order to increase the content of rare-earth oxides in magneto-optical glass and improve the Verdet constant, the rare-earth doped ternary Ga2O3-B2O3-SiO2(GBS) system magneto-optical glasses were prepared by the melt quenching technique. The infl uence of Tb3+ and Dy3+ ions on the structure of GBS glasses was investigated using FTIR, DSC and Faraday rotations. The experimental results showed that the content of rare-earth oxides in the glasses with the double incorporation of Tb2O3 and Dy2O3 was higher. The crystallization parameter β achieved the maximum 0.48 with Tb3+/Dy3+ content of 35mol%. Terbium oxide existed mainly in [TbO3] units in the glasses and [TbO4] units were converted into [TbO3] with increasing Tb2O3 content. As Ga3+ ion is larger than B3+ ion in radius, leading to an increasing of the glass network gap and improvement in the ability of accommodating rare earth ions, Verdet constant increased.     

超高性能轻质混凝土的力学性能及微观结构

超高性能轻质混凝土(ultra-high performance lightweight concrete,UHPLC)是一种由高强水泥浆体、漂珠和纤维组成的密度低于1 950 kg/m~3的新型水泥基结构材料。本文研究了不同养护制度及养护龄期对UHPLC抗压强度、轴拉力学性能和弯曲性能的影响,最后利用扫描电镜观察了UHPLC中漂珠的微观形貌。结果表明:随着龄期增长,UHPLC的抗压强度、轴拉性能和弯曲性能均提高,并出现明显的应变强化现象,说明养护龄期对UHPLC基体强度和纤维-UHPLC基体的界面黏结强度均有显著提高作用;高温蒸汽养护3 d可促进UHPLC基体早期强度发展,使UHPLC的抗压强度和弯曲性能迅速达到标准养护28 d时的水平,显著缩短养护龄期,但对纤维-基体界面黏结强度的贡献不大,黏结强度仍主要受龄期影响;UHPLC实测密度为1 815.2 kg/m~3,100 mm立方体抗压强度达103.1 MPa,极限抗拉强度达7.60 MPa,极限拉应变达0.431%,出现明显的应变强化现象,弯曲峰值强度达22.43 MPa,满足了RPC160的抗折强度要求,实现了水泥基结构材料轻质高强的目标。     

Effect of nano-ZrO2 on microstructure and thermal shock behaviour of Al2O3/SiC composite ceramics used in solar thermal power

The Al2O3-ZrO2(3Y)-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength of samples with 10vol% nano-ZrO2 sintered at 1480℃ were 3.222 g/cm3 and 160.4MPa,respectively.The bending strength of samples after 7 times thermal shock tests (quenching from 1000℃ to 25℃ in air medium) is 132.0MPa,loss rate of bending strength is only 17%.The effect of nano-ZrO2 content on the microstructure and performance of Al2O3-ZrO2(3Y)-SiC composite ceramic was investigated.The experimental results show that the bending strength of samples with above 10vol% nano-ZrO2 content has decreased,because the volume expansion resulting from t-ZrO2 to m-ZrO2 phase transformation is excessive;Adding proper nano-ZrO2 would be contributed to improve the thermal shock resistance of the composite ceramics.The Al2O3-ZrO2(3Y)-SiC composite ceramic has promising potential application in solar thermal power.     

The effect of alumina content on fracture property of all-ceramics zirconia

The purpose of the present study was to evaluate the effect of Al2O3 content on the fracture property of all-ceramics ZrO2. To improve the all-ceramics ZrO2 restoration mechanics properity ,96 samples containing 0,5,10 and 15 wt% of Al2O3 particles were prepared by cold isostatic pressing (200 MPa) and 1 550 ℃ sintered .The phase was analyzed by X-ray diffraction analysis and the bulk densities of the samples were made using Archimedes principle. Samples were randomly divided into four groups. In each group, 24 specimens were prepared so that the angle between notch and specimen’s long axis is 90o and 60o. Notch depths were 1 mm for all samples. Samples were loaded with three-point bending method. 90° cut samples were used to measure fracture toughness while 60°cut samples were used to observe fracture curve by taking points on the fracture extension path under microscope, plotting points on coordinates, generating fitting curve by software "Origin", and analyzing the microstructure of the specimen fracture surfaces by scanning electron microscopy (SEM).The results show that the increment of Al2O3 has insignificant effect on the densification of all-ceramic ZrO2.XRD analysis shows that the specimen is comprised of t-ZrO2 and α- Al2O3 before fracture while fracture surface is m-ZrO2, t-ZrO2 and a-Al2O3. ZrO2 containing 10% Al2O3 has the optimum mechanical properties and unconspicuous crack propagation and distribution. The observations may provide a reference for the materials selection, shape design , and production process of all-ceramic crown and bridge.     

Structure and dielectric properties of ZnO and Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> doped BaO-TiO<Subscript>2</Subscript> system microwave ceramics

The microwave dielectric properties and microstructure of BaTi4.3ZnyO9.6＋y ＋0.02 mol% SnO2＋0.01 mol% MnCO3＋x mol% Nb2O5（x=0-0.05, y=0-0.08） system ceramics were studied as a function of the amount of ZnO and Nb2O5 doped. Addition of （y=0-0.05） ZnO and （x=0-0.025） Nb2O5 enhanced the reactivity and decreased the sintering temperature effectively. It also increased the dielectric constant ε r and quality factor Q（=1/tan 8） of the system due to the substitution of Ti^4＋ ions with incorporating Zn^2＋and Nb^5＋ ions, which was analyzed by the reaction ZnO＋Nb2O5＋ 3 TiTxTi →ZnTi＋ 2NbTi＋3TiO2. When the system doped with （y=0.05） ZnO and （x=0.025） Nb205 were sintered at 1 160 ℃ for 6 h, the εr. Qf0 value and rfwere 36.5, 42 000 GHz, and＋1.8 ppm/℃, respectively, at 5 GHz.     

Photocatalytic H2 evolution activity of CuO/ZrO2 composite catalyst under simulated sunlight irradiation

Zirconia-supported CuO (CuO/ZrO₂) composite photocatalysts were successfully synthesized via citric acid-assisted sol-gel technique. For comparison, CuO/ZrO₂ materials were also prepared by solid state reaction and co-precipitation method. The as-prepared powders were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and thermogravimetric-differential thermal analysis (TG-DTA). The photocatalytic activity of CuO/ZrO₂ catalyst was investigated based on the H₂ evolution from oxalic acid solution under simulated sunlight irradiation. The effects of molar ratio of CuO to ZrO₂, preparation method, phase change with the calcination temperature and the durability on the photocatalytic activity of the photocatalyst were investigated in detail. It is found that the optimal activity of photocatalytic H₂ evolution (2.41 mmol·h⁻¹μ⁻¹) can be obtained when CuO/ZrO₂ composite photocatalyst is synthesized by sol-gel technique and the mole ratio of CuO to ZrO₂ is 40%. The activity of copper oxide supported on monoclinic ZrO₂ calcined at higher temperature is much higher than that on tetragonal ZrO₂ calcined at lower temperature, and the best calcination temperature is 900 °C.     

Low temperature degradation of alumina-toughened zirconia in artificial saliva

The long-term aging behavior of an alumina-toughened zirconia (ATZ) ceramic in artificial saliva hydrothermal atmosphere was determined and compared with that of tetragonal zirconia polycrystals doped with 3mol% Y₂O₃ (3Y-TZP). The specimens of 3Y-TZP and ATZ were aged in distilled water and artificial salivary respectively at 134 °C. Monoclinic phase content was evaluated by X-ray diffraction (XRD) analysis. Specimen strength was determined by a biaxial bending test. Surface screening was done using an atomic force microscope (AFM). No statistically significant influence of any treatment on strength was demonstrated for either material. However, XRD measurements revealed ATZ’s anti-aging properties were much better than TZP after the aging treatment. Therefore, ATZ can be applied to the field of dentistry. Artificial saliva in ceramic surface sediments may be useful for strengthening ceramics.     

The influence of mo additive on the microstructure and property of Ti/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite

The influence of Mo on the microstructure, bending strength and HV of Ti/Al₂O₃ composite was studied, and the influence mechanism was analyzed. The results indicate that after the addition of Mo, the composite organization is finer and phases distribution is better-proportioned which make the microstructure denser, the bending strength and HV of composite are also increased to a degree. But the bending strength increases first then decreases with the increasing of Mo content, so the appropriate Mo content for the Ti/Al₂O₃ composite is to be further confirmed. WANG Zhi: Born in 1962 Funded by Natural Science Foundation of China (No. 50232020) and Natural Science Foundation of Shandong Province (No. 2002F21)     

Fabrication, property characterization and toughening mechanism of HA-ZrO2(CaO)/316L fibre composite biomaterials

HA-ZrO₂(CaO)/316L fibre composites were successfully fabricated with vacuum sintering method and their properties and toughening mechanism were studied. The results showed that HA-ZrO₂(CaO)/316L fibre biocomposite having 20 vol% fibres had optimal comprehensive properties with bending strength, Young’s modulus, fracture toughness and relative density equal to 140.1 MPa, 117.8 GPa, 5.81 MPa·m^1/2 and 87.1%, respectively. The research also addressed that different volume ratios of the composites led to different metallographic microstructures, and that metallographic morphologies change regularly with volume ratios of the composites. 316L fibres were distributed randomly and evenly in the composites and the integration circumstance of the two phases was very well since there were no obvious flaws or pores in the composites. Two toughening mechanisms including ZrO₂ phase transformation toughening mechanism and fibre pulling-out toughening mechanism existed in the compsites with the latter being the main toughening mechanism. Supported by the National Natural Science Foundation of China (Grant No. 50604017) and the Postdoctoral Science Foundation of Central South University     

Microstructure and mechanical properties of 8YSZ ceramics by liquid-phase sintering with CuO-TiO2 addition

The 8% (mass fraction) yttrium-partially-stabilized zirconia (8YSZ) ceramic was fabricated via liquid phase sintering at 1 200–1 400 °C by adding different mass ratios of CuO-16.7%TiO₂ (molar fraction) as sintering aid. Relative density, microstructure, Vickers hardness and bending strength as a function of sintering temperature and additive content were investigated. The experiment results show that liquid phase sintering at low temperature can be realized through adding CuO-16.7% TiO₂ to 8YSZ. The Vickers hardness and bending strength of samples with sintering aid are generally much higher than those of samples without sintering aid for all sintering temperatures, and increase with the increase of sintering temperature. When the addition content of CuO-16.7% TiO₂ is beyond 0.5%, the relative density, Vickers hardness and bending strength decrease with the increase of the mass ratio of sintering aid. Low additions of sintering aid are beneficial to aiding densification; high additions of sintering aid are detrimental to the sintered properties mainly due to greater amounts of pores generated by the volatilization of oxygen with the eutectic reaction between copper oxide and titanium dioxide. It is found that the fine grain size and high relative density are two main reasons of the high bending strength and Vickers hardness of the materials.     

Effect of metallic content on mechanical property of Ni/（10NiO-NiFe2O4 ） cermets

1 INTRODUCTIONThe use of inert or non-consumable anodes forreplacement of consumable carbon anodes in Hall-H啨roult electrolysis cells for the production of alu-minum has been a technical and commercial goalfor many decades .In the present process ,consumable carbon an-odes are used,andthe anode product is CO2. Withaninert anode ,the cell reaction will be :Al2O3=2Al +23O2(1)The basic requirements for aninert anode are :1) to exhibit a lowcorrosion rate in the high tem-perature melts an…