Fabrication of ultrahigh density ZnO-Al_2O_3 ceramic composites by slip casting

The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites.The Zeta potential of raw powders was measured.ZnO and Al2O3 powders have lower Zeta potential than-45 mV commonly at pH 8-10.3 with polyacrylic acid(PAA)added.The influence of pH and the mass fraction of the additives on the stability and fluidity of the suspensions added with PAA and polyethylene glycol(PEG) was investigated by experiments of viscosity and sedimentation.The suspensions have the lowest viscosity and the best stability at pH 9 with 0.2%PAA(mass fraction).The maximum density of green compacts is 66.6%of theoretical density(TD)with compacting and homogeneous green particles.An ultrahigh density sintered compact(>99.6%TD)could be obtained after pressureless sintering at 1 400℃for 2 h.

Preparation of YSZ solid electrolyte by slip casting and its properties

Fully stabilized YSZ solid electrolyte was prepared by slip casting. The density was measured according to the Archimedes principle and the linear shrinkage was calculated from measuring the sizes of samples before and after sintering. XRD analysis was conducted to verify the phase structure of both the starting YSZ powder and the prepared YSZ electrolyte. The microstructure of fracture surface and the electrical properties of the samples sintered at different temperatures were investigated via SEM and a complex impedance method, respectively. By comparison of the properties and features among the samples, a slip casting method was established to be a simple way to manufacture high-quality YSZ electrolyte at the sintering temperature of 1550℃ for 3 h, which provides a new approach for YSZ electrolyte with complex shapes and mass production.

Electrical Properties and Applications of (ZrO_2)_(0.92)(Y_2O_3)_(0.08) Electrolyte Thin Wall Tubes Prepared by Improved Slip Casting Method

mole fraction) yttria-stabilized zirconia electrolyte thin wall tubes were p repared by i mproved slip casting method. The length and wall thickness of the tubes are 266 mm and 0.4～0.9 mm, respectively and the relative density is 96.7%. The microstr ucture and electrical properties of samples sintered at different temperatures w ere studied using SEM and ac impedance spectroscopy. The effect of sintered dens ity, grain and grain boundary on the electrical properties of the samples was analyzed. The research results show that the density of the samples increase s gradually with increasing sintering temperatures. The microstructure of sample s strongly influences its electrical properties, and the electrical properti es of samples enhance with the increase of sintered density. The ionic conductiv ity of grain and grain boundary is increased as the sintering temperature incre ases. Better sinterability of the samples was obtained at the sintering temperat ure of 1650 ℃. The maximum open circuit voltage and short circuit current for s ingle cell is 0.946 V and 1.84 A, respectively. The maximum output power of sing le cell is 0.46 W at the temperature of 850 ℃.

Preparation and properties of gradient Al_2O_3-ZrO_2 ceramic foam by centrifugal slip casting method

The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.

Cone-shaped cylindrical Ce_(0.9)Gd_(0.1)O_(1.95) electrolyte prepared by slip casting and its application to solid oxide fuel cells

A cone-shaped gadolinium doped ceria（Ce0.9Gd0.1O1.95,GDC） electrolyte cylinder with a thin wall was fabricated using slip cast-ing technique.The diameter of the larger open end of the cone-shaped cylinder was 0.85 cm,the length was 1.0 cm,and the thickness of the wall was 0.026 cm after sintering.Both the electrolyte and electrode powders were fabricated by using a glycine-nitrate process.A single solid oxide fuel cell（SOFC） was prepared with the cone-shaped electrolyte,NiO-GDC（70：30 wt.%） anode and Sm0.5Sr0.5CoO3（SSC） cathode.Its electrochemical performance（I-V curve） and electrochemical impedance spectroscopy（EIS） were studied with humidified hydrogen as the fuel and air as the oxidant.The maximum output power density was about 300 ？mW/cm2 at 700 oC.The EIS results showed that the dominant loss of the SOFC was from the ohmic resistance of the electrolyte.

Preparation of transparent Y_2O_3 ceramic by slip casting and vacuum sintering

In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid（PAA-Na） as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dis-persant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scanning electron microscopy（SEM） and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0 dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 oC for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative den-sity of 99.36% and transmission of 30% at 800 nm wavelength.

A novel technique for making open-cell Al_2O_3-ZrO_2 ceramic foam with plant seed template

The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.

Investigation of Microstructure of Al_2O_3/LaPO_4 Ceramic Composites

SUS/TZP FGM was fabricated by slip casting. The relationship between the performing and sintering process was investigated. The suitable sinter temperature was determined. The cooling rate is controlled to avoid the crack caused by the different shrinkage of SUS and TZP. Therefore, the performance of FGM can is maximal if the sintering process is controlled to the optimal condition.

Sea Urchin Spines as a Model-System for Permeable,Light-Weight Ceramics with Graceful Failure Behavior.Part Ⅱ.Mechanical Behavior of Sea Urchin Spine Inspired Porous Aluminum Oxide Ceramics under Compression

Sea urchin spines were chosen as a model system for biomimetic ceramics obtained using starch-blended slip casting. Porous alumina ceramics with cap-shaped layers with different alternating porosities were found to have superior fracture behavior under bulk compression compared to ceramics with uniform porosity.They fail in a cascading manner,absorbing high amounts of energy during extended compression paths.The porosity variation in an otherwise single phase material mimicks the architectural microstructure design of sea urchin spines of Heterocentrotus mammillatus,which are promising model materials for impact protection.

Predicting model on ultimate compressive strength of Al_2O_3-ZrO_2 ceramic foam filter based on BP neural network

In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template （F）, centrifugal acceleration （v） and sintering temperature （T）, while the only output was the ultimate compressive strength （（7）. According to the registered BP model, the effects of F, v, T on 0 were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.

Preparation of Porous Calcium Phosphate Bioceramic

Porous calcium phosphate ceramics were prepared by slip casting and molding method respectively. By these two different methods, different microstructures can be got. By slip casting method, the pore size was 100- 350μm and 20- 80 μm ; pores were opened, interconnected and ball-like ; the grain size was 2-4μm. By molding method, the pore size wus 100-500μm and 1- 10μm ; the grain size was 2- 8μm. By slip casting method regalar and interconnected pores can be gnt. By molding method the porosity and strength can be adjusted easily.

Towards high degree of c-axis orientation in MgB_(2) bulks

The paper presents fabrication and characterization of spark plasma sintered textured(001) MgB_(2)with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magnetic field(12 T) and 0 T magnetic field, respectively.Structural characterization was performed by X-ray diffraction, and electron microscopy. The analysis revealed unexpected preferred orientation also in the MgO secondary phase due to the epitaxial growth of(111) MgO on(001) MgB_(2). The influence of oriented microstructure on the superconducting characteristics expressed by critical current density(J_(c)), irreversibility field(H_(irr)), and on the pinning properties were assessed. High anisotropy versus sample orientation in applied magnetic field, H, was observed for J_(c), Hirr, pinning activation energy(U^(*))extracted from relaxation measurements. The zero-field critical current, J_(c0)and F_(p),maxare weakly or not dependent on the direction of H,while the other indicated parameters are significantly influenced. Results enable control of superconducting parameters by further optimization of microstructure through MgB_(2) texturing as a novel and viable strategy for development of bulk MgB2with enhanced properties when taking advantage of its anisotropy.