Showing papers in "Journal of Inorganic Materials in 2001"

Progress of Study on ZnO Thin Film and its Properties

Abstract: ZnO thin films are the materials with many excellent properties such as piezoeletricity, conductivity, optical absorption and emission, gas-sensitivity, and highly nonlinear voltage-current characteristics They have a wide variety of applications such as transparent conductors, luminescence diode, window materials for solar cells, optical wave guides, phosphor for monochrome field emission displays, piezoelectric transducers in the GHz range, surface acoustic wave devices, micro-sensors and micro-actuators, and low-voltage varistors There are many methods for the preparation of ZnO thin films, and each has its advantages and disadvantages The properties of ZnO thin films depend on the dopants and the preparation conditions This paper reviews the preparations and properties of ZnO thin films, and discusses their development prospects

Preparation Methods of Ceramic Ink for Jet-Printing Forming

Abstract: Several preparation methods of ceramic ink for jet printing forming are reviewed and the related research work is reported. Although the dispersion method is simple, its dispersiveness and stability are not good enough for jet-printing forming. Fine particle size in ceramic ink can be obtained by sol methods and its dispersiveness is much better. Unfortunately,its stability still requires to be improved further to match the needs of forming. The reverse microemulsion has excellent dispersiveness and stability, and can easily achieve the dispersion in nanometer level. However, the problem of low solid content in reverse microemulsion should be solved by taking effective measures.

Effect of TiO2 and MgO additions on microstructures of Al2O3

Abstract: By using pressureless sintering technique, the samples of Al2O3 with anisotropic grains through the doping of small amount of TiO2 and MgO were prepared. The effects of quantity of TiO2 and MgO and sintering temperature on the microstructure of Al2O3 were also investigated. The doping of MgO makes the grains of Al2O3 smaller in contrast to the ones in Al2O3 doped with pure TiO2. It is possible to adjust the aspect ratio of Al2O3 grains and gain a homogeneous microstructure in Al2O3 by means of changing the amount of MgO additions in the material.

Process and Study on Preparation of Continuous Zirconia Fibres from Zirconia Acetate

Abstract: In order to obtain continuous zirconia fibres with high melting point and mechanical properties, newly-produced zirconium acetate was used as a precursor to synthesize a sol containing Zr-O chains by a sol-gel process and continuous zirconia fibres were produced by dry spinning. The spectral and thermal properties of zirconium acetate were studied. The sintered fibres were observed by SEM, and their XRD results analyzed, while their tensile strength tested. The results show that a long chain of Zr-O bond exists in zirconium acetate precursor and the sol has good spinnability and stability. The obtained fibres with diameter under 20um have certain tensile strength and toughness. 5mol% Y-doping is effective on stabilizing the tetragonal phase of zirconia.

Structural Characterization of Micro-arc Oxidation Formed Titanium Dioxide Films Containing Ca and P

Abstract: Titanium dioxide films containing Ca and P on titanium alloy were prepared by micro-arc oxidation. The effect of electrolyte composition and micro-arc voltage on the phase construction, Ca/P atomic ratio, and morphology of the films were explored. The results show that the films are composed of anatase TiO2 and rutile TiO2, which appear dense for inner layer and porous for outer layer in morphology. And Ca/P atomic ratios in the films tend to increase from the film/titanium alloy interface to the surface. The content of amorphous TiO2, size of pores, and Ca/P atomic ratio in the films are increased with increasing micro-arc voltage. Howewer, the films exhibit micro-cracks at higher micro-arc voltage. Increasing Ca/P ratio of the electrolyte can improve the Ca/P atomic ratio in the films.

Reaction Mechanism of Silicon Carbide Ceramics Derived from Woods

Abstract: The process of reaction of silicon carbide ceramics derived from wood was investigated The reaction mechanism was also analyzed The results show that the temperature of silicon infiltration determines the ultimate microstructure of SiC ceramics Porous SiC materials are formed at lower temperature, while at higher temperature, compact Si/SiC composite materials formed The process of silicon-carbon reaction can be described as three steps: (1) Melted Si ascends via capillary of charcoal and reacts with contacted carbon forming silicon carbide (2) The thickness of SiC layer increases toward carbon layer till the end (3) Reaction-formed SiC will re-crystallize in the later stage of the reaction, and the ultimate microstructure is composed of large size of polygonal SiC and free Si

Experimental Research of the Synthesizing of 13X Molecular Sieves from Potash Feldspar Ores

Abstract: X molecular sieve was synthesized from potash feldspar ores by baking and hydrothermal synthesizing procedures. The optimal technological parameters were determined by means of quadrature experiment. The properties of the synthesis powder such as XRD, crystal constants, SEM, DTA, chemical composition, SiO2/Al2O3 are similar to those of the ideal 13X moleclar sieve. And its absorbability comes up to the state standards of chemical industry of China.

Preparation of Nano-sized Alumina Powders at Low Temperatures

Abstract: Alpha alumina nanocrystalline powders, with mean particle size less than 50nm, were prepared by a novel synthesis process using Al(NH3)39H2O and NH3H2O solutions as raw materials The process mainly utilized a seed-effect of fine grains worn from the milling mediums and also utilized ZnF2 or AlF3 additives The phase transformation temperatures to alpha alumina can be reduced dramatically to 900-920℃ by improving the homogeneity of seeds with the hydrous alumina and accelerating the mass diffusivity and transportation in the transformation process

Progress in bismuth-contained mixed conducting oxide membranes

Abstract: Mixed oxygen-ion and electronic conducting ceramic membranes have received increasing attention in the past decade The progress in bismuth-contained mixed conducting oxide membranes was reviewed, considerable attention was paid to the progress made in our group during the past years The problems associated with the bismuth-contained materials were discussed The promising developing direction was also pointed out

Shape Control of Hydroxyapaptite Crystal Seed and Its Effects on the in-situ Reinforcement of Calcium Phosphate Cement

Abstract: The effects of the contents of different regulators including D-sorbital, mannose, galactose, glucose, and fructors on the growth of hydroxyapaptite crystal seeds were studied, and the crystal seeds obtained were then applied to the in-situ reinforcement of calcium phosphate cement. The experimental results show that the discrepancies of the surface energy and structure of the crystal of different orientations lead to different growth rates, and this is the thermodynamic foundation of its in situ reinforcement. The compressive strength of the hardening body is up to 76.1 MPa, the diamentral tensile strength is up to 24.5 MPa.

Influence of Transition-Metal Cr Doping on Optical Properties of Rutile Single Crystal

Abstract: The visible-light absorption of rutile was raised through doping Cr ion into the surface of rutile crystal with high-temperature-diffusion-doping-sensitization technique. TiO2: Cr specimen was analyzed by means of UV-VIS, XFA, XRD, XPS and LRS, respectively. As a result, it is shown that after Cr ion is doped into the surface of the crystal, Cr ion exists in the solid-melting-state Cr2TiO5, which induces the original absorption edge(410nm) move to 750nm, and achieves match with solar spectrum and raises optical absorption to visible-light effectively.

Direct Coagulation Casting of Silicon Nitride Ceramics

Abstract: Direct coagulation casting (DCC) is a novel in-situ shape-forming method for ceramic green bodies, especially for fabricating parts with complex shapes. On the basis of a series of studies, such as surface modification of silicon nitride powder, adjustment of pH in dispersing medium and introduction of efficient dispersant, silicon nitride suspension with low viscosity and high solid loading was prepared. After optimizing the forming parameters, silicon nitride green body with 60% of the theoretical density and sufficient strength for demoulding was produced. The green body has homogeneous microstructure and smooth fractured surface. The pore size distribution of the green body is uniform, narrow and unimodal. At a lower sintered temperature (1750℃), bulk density of the material by pressless sintered is 98% of the theoretical value. The specimen sintered at 1800℃ for 2h has a homogeneity microstructure, flexure strength of 758.4MPa and a fracture toughness of 6.3 MPa·m1/2.

Solid State Synthesis and Gas Sensing Properties of Nanometer ZnO

Abstract: Precursors were synthesized by solid state reaction of zinc acetate with oxalic acid. ZnO gas sensing materials were obtained by decomposition of the precursors and characterized by XRD and TEM. La2O3 and Nd2O3 were doped in nanometre ZnO materials by the methods of solid state and liquid state reaction. The sensitivity of the materials was measured at various mole ratios of ZnO to La2O3 or Nd2O3. The gas sensitivity of ZnO element to C2H5OH, NH3 and LPG were measured in static state at a various operational temperatures. The results show that ZnO prepared by this method is highly sensitive to C2H5OH and selective between C2H5OH, NH3 and LPG at a low operational temperature.

Impregnating Process of Reticulated Porous Ceramics Using Polymeric Sponges as the Templates

Abstract: Commercial polyurethane sponges with three dimensional network and open cells, were used as the templates to produce SiC based reticulated porous ceramics (RPCs) from ceramic slurries by the replication process. Surface modification of polyurethane sponges was carried out by a surfactant with hydrophile-lipophile balance (HLB) valuel2. This pretreatment is beneficial to increase the adhesion of the slurry to the sponge. Effects of slurry solids content, pore diameter of sponge, distance between the rolls and the number of passes on the loading of slurry on the sponges and macrostructure of RPCs, were investigated in detail. The results indicate that the macrostructure of RPCs depends strongly on the slurry solids content and relative distance. The relative density of RPCs has a good linear relationship with the relative distance, which is very important to predict and optimize the permeability and mechanical properties of RPCs.

Preparation of Yttria Stabilized Zirconia Ultrafiltration Membranes with Inorganic Precursors

Abstract: Yttria stabilized zirconia (YSZ, 8% mol Y2O3) membranes with expected composition were coated on porous alumina substrates by a dip-coating process with YSZ sol, which was prepared by sonicated dispersing YSZ powder in ethanol. The YSZ powder was synthesized by co-precipitation from inorganic aqueous solutions of ZrOCl2.8H2O and Y(NO3)3.6H2O, followed by azeotropic distillation and sintered at 600℃ for 2h. Crystalline structure of the YSZ powder was characterized by X-ray diffraction. Particle size of the sol was determined by laser scattering measurement. The mean pore diameter of an unsupported YSZ membrane was about 6nm as investigated by nitrogen isothermal desorption measurement. Investigation with scanning electron microscopy and nitrogen permeation testing showed that the membranes were crack-free.

Bioinorganic Material─The Crude Ca-oxalate Conservation Film on Historic Stone

Abstract: A crude conservation film was found that formed naturally on the surface of some historic stone buildings and monuments It was so well preserved that the stone inscriptions under the film were not damaged though they were made one more thousand years ago In this contribution, the composition and origin of the crude conservation film were focused The samples o f the film were analyzed by FTIR, PLM, EDAX, SEM and TEM The results show that the film consists mainly of calcium oxalate and there is a microbial involvement in the calcium oxalate film There is no clear dividing line between the carbonatematrix and oxalates film The transformation layer is about 15um thick The thin bioinorganic film is very compact non-porous shell and the calcium oxalate is far more acid resistant than that of calcium carbonate The forming mechanism was discussed and the chemical bionics of this crude film was also researched

Influence of Fiber Pre-coating on Mechanical Properties and Interfacial Structures of SiC(f)/SiC Composites

Abstract: High performance SiC(f)/SiC composites were fabricated by chemical vapor infiltra- tion (CVI) processing. The effects of pre-coating of SiC fiber on the mechanical properties and microstructures of SiC(f)/SiC composites were investigated. It was found that the introduction of C or BN pre-coating on SiC fiber surface could promote the pull-out of fiber and interfacial debonding in the course of fracture markedly coupled by great increases of fracture toughness and work of fracture. SEM micrographs indicated that strong interfacial bonding between fiber and matrix was changed, suggesting that the brittle fracture mode of SiC(f)/SiC composite without any pre-coating was improved. HREM observation showed that in the initial period of CVI pro- cessing, graphite interphase with obvious layered configuration with better crystallization degree was first deposited on the surface of fiber, whereas the C pre-coating on SiC fiber was amorphous.

UV Light Irradiation of Nanocomposite SiO_2-TiO_2 Thin Films Derived by a Sol-Gel Method

Abstract: The nanocomposite silica-titania thin films were deposited with a dip-coating method on silicon wafers, fused quartz and K9 glass substrates from a sol made by a two-step hydrolysis method. A high-pressure mercury lamp was used to act as irradiation treatment. AFM, ellipsome- try, FTIR, UV-Vis spectrophotometer and XRD were used to characterize the structure and optical properties of the as-grown and UV irradiated films. The results show that the UV-irradiation is one of the effective methods to densify the sol-gel thin films at a relative low temperature. The densification mechanism is different from that of the conventional thermal treatment. Electron ex- citation is induced directly by the UV light irradiation,which is able to cause the bond cleavage in gel network and make gel films densify through the rearrangement of the gel structure eventually

Fabrication and characterization of anode substrates and supported electrolyte thin films for intermediate temperature solid oxide fuel cells

Abstract: LSGM+NiO anode substrates for intermediate temperature solid oxide fuel cells were fabricated and the relationships between porosity, pore radii distribution, electrical conductivity of the substrate and its composition were studied Effects of the substrate composition, microstructure, fabrication process on the formation process, quality and structure stability of the supported LSGM thin films were investigated Based on these works, we successfully made a dense supported LSGM thin film with a thickness of 20-50 mum using a costly effective wet chemical-physics method Anode substrate with 60% NiO possesses preferable sintering-shrinkage rate, porosity and pore radii distribution Its specific pore surface area and specific pore volume are also larger Electrical conductivity of reduced anode substrates increases with NiO content in the substrates Electrical conductivity of reduced anode substrates with low NiO content increases rapidly with ac impedance measuring time and changes from electronic conduction to ionic conduction Electrical conductivity of substrates with high NiO content changes very slow with measuring time, showing metal conducting property and very high electrical conductivity from the beginning On the surfaces of supported LSGM thin films fabricated by non-restraint sintering method, large flat grains can be seen and cracks appear along grain boundaries after reduction in H(2) On the surfaces of supported LSGM thin films fabricated by isostatic-pressure sintering method, just small grains with even crystal sizes which contact with each other tightly can be seen and after reduction in H(2), no cracks appear on grain boundaries

Interfacial Reaction of SiC/Fe-Cr Alloy

Abstract: The microstructure of the reaction zone and the reaction kinetics of sintered α-SiC/Fe- 20Cr alloy annealed at 900℃ to 1150℃ were studied by using XRD, EMPA, SEM. The reaction zone can be divided into two sections of the SiC reaction zone and the metal reaction zone, according to the morphology and element distributions of the reaction zone of SiC/Fe-20Cr. The SiC reaction zone has high Fe and Si, but low Cr concentration, and it is composed of the bright matrix of Fe3Si, Cr7C3 and Cr3Si, and randomly distributed graphite precipitates. The metal reaction zone is a uniform region of (Cr,Fe)7C3, possessing very high Cr content. It is believed that the interface reaction is controlled by the atom diffusion through the reaction zone, and the reaction rate constant K is equal to 1.9×10-4exp(-235×103/RT)m2·s-1. The metal reaction zone hinders the interface reaction by inhibiting the diffusion of Fe atoms from the alloy towards the SiC reaction zone. The effect of the metal reaction zone can be improved with the increase of Cr content of the Fe-Cr alloys.

Preparation of TiO_2 Nanometer Powders

Abstract: Monodisperse controllable TiO2 nanoparticles were prepared by using the hydrolysis of metal alkoxides(titanium tetrabutoxide) and modification of surface of particles in alcohol solution. The effect of reactive condition including reactant concentration, reactant time and solvent was studied in detail. The properties of particles were analysised by TEM, IR and so on. The experimental results show that TiO2 particles prepared are amorphous, well dispersed, and their particle sizes vary from 50 to 300nm along with the change of reactive conditions.

Effects of Polyvinyl Alcohol(PVA) Content on the Microstructures of Unsupported Alumina Membranes

Abstract: Polyvinyl Alcohol(PVA) can prevent the microcrack of the sol-gel-derived aluminamembranes from occurring during the drying process, and at the same time has effects on themicrostructures of the membranes. In the present paper, the crystalline phase, thermal stability,specific surface area, pore size distribution and pore surface fractal of alumina membranes dopedwith PVA were characterized by XRD,DTA,DGA, FT-IR and BET. The results show that PVA iscompletely removed after calcination at 400℃. The N2 adsorbed amount of PVA-doped aluminamembranes is greater than that of pure membranes, but doesn't increase in proportion to PVAcontent. The PVA-doped alumina membranes have a sharper pore size distribution, higher porevolume and lower pore surface fractal dimension.

KDP Crystal Growth by Decreasing Temperature Using Supersaturation-Control System

Abstract: A real-time cross-correlation between concentration, temperature and electrical conductivity of KDP aqueous solution was determined by using an transformer-type conductivity sensor. This correlation can be expressed by L(Ts,t) = L0(t) + b1(t)Ts + b2(t)Ts2. On the base of the correlation, a computer system was made to realize the in-line measurement and control of the supersaturation of the growth solution. The system can control the supersaturation within ±0.049 KDP/100g water (±0.12% relative supersaturation). The system was used to study the relationship between the supersaturation of the growing solution and the properties of the crystals grown from different raw materials. It was found that growth rate rise but the homogeneity of KDP crystal goes down as the supersaturation increases. The system makes KDP crystal growing under a stable supersaturation and the growth band and scattering particles inside the crystals suppressed, so the optical transmittance and laser damage threshold of the crystal improved.

PMN-PT Ferroelectric Relaxor Crystal and Its Ultrasonic Transducer

Abstract: The electric and mechanical properties of PMN-PT (67/33) ferroelectric relaxor crystal were measured. The piezoelectric and dielectric properties of PMN-PT crystal was discussed in comparison with the generally used piezoelectric ceramics and polymer. The performances of the unturned PMN-PT ultrasonic transducer with longitudinal vibration mode was evaluated. The influence of the PMN-PT dielectric and mechanical loss on impedance and transducer loss were discussed.

Properties of Crystallizing and Absorbing F~- Ion of HAP Synthesized by Sol-Gel Process

Abstract: Hydroxyapatite (HAP) was prepared by a sol-gel process. XRD, IR, BET measurement and static -dynamic absorption test were used to study the absorbing mechanism and action, to analyze the specific surface area, degree of crystallization and lattice defect, crystalline size, thermal stabilization and equilibrium capacities of absorbing F- ion of the HAP synthesized by changing the molar ratio of Ca to P and calcination temperature. Test results indicate that the HAP can be used as green environment protection material, as the result of its strong ability of absorbing F- ion under the operating conditions of common temperature and common pressure and non-secondary pollution.

Processes Affecting Microwave Sintering of ZTA Ceramics

Abstract: The Al2O3-ZrO2 system was chosen to be fabricated by microwave sintering The principal processes affecting the sintering rate were analysed on account of the properties of ZTA ceramics The TE444 multi-mode microwave system was designed and a hybrid heating system was developed with well arranged aided heaters The ZrO2 content in ZTA samples affected the microwave sintering rate, which showed the probability for the low-loss materials to be sintered by microwave process mixed with high-loss materials to raise their sintering rate The increase of the inlet power made the temperature raise rapidly The aging phenomena of the aided heaters lowered the sintering rate and the thermal runaway should be avoided to advance the sample properties