Effect of seed particles content on texture formation of Si_3N_4 ceramics by gel-casting in a strong magnetic field

In this paper, the textured Si3N4 ceramics were prepared by adding seed particles during gel-casting in the magnetic field of 6 T, followed by pressureless sintering. The effect of pH on the stability and dispersibility of Si3N4 slurry and the effect of seed particles content on texture formation of SiaN4 ceramics were both studied. Those results showed that the slurry with good stability and dispersibility was obtained when pH was about 11.6. The a or b-axis of Si3N4 particles or crystals was aligned parallel to the direction of the magnetic field in the magnetic field of 6 T. The degree of texture of Si3N4 ceramics further increased during sintering. With the increasing of additional β-Si3N4 particles in the magnetic field of 6 T, the degree of texture increased from 0.19 without seed particles to 0.76 with 9% （mass fraction） seed particles. The increase of seed particles content promoted the texture formation of Si3N4 ceramics.

Porous nickel–titanium alloy prepared by gel-casting

To explore the preparation of porous nickel- titanium alloy with excellent properties, larger size and complex shape, the premixed powder of Ni and Ti with atomic ratio of 1：1 was shaped by gel-casting. The effects of solids loading and the content of dispersant on flow ability of nickel-titanium slurry and the mechanical properties of nickel-titanium sintered body were studied. The drying models under different solids loading were also discussed. The results show that the viscosity of slurries significantly increases with an increase in solids loading. After a proper process of drying, the green body with complex shape is obtained. The sintered body with porosity rate reaching up to 49.5 % and compression strength reaching to 364.74 MPa could meet the basic demands of implant materials.

Effects of agarose concentration and addition on the properties of gel-cast 3Y-ZrO2 green and sintered bodies

Using agarose as a gel agent to prepare ceramics is a suitable non-toxic gel-casting method. The effects of agarose concentration and addition amount on gel-cast 3Y-ZrO_2 green and sintered bodies were investigated. Green bodies were prepared by gel-casting using an agarose solution of a different agarose mass fraction including 3.0%, 3.5%, 4.0%, 4.5%, 5.0% and 5.5%with an added amount of agarose in the green body at a mass fraction of 0.7%, and using the agarose solution of a mass fraction of4.5% with a different amount of added agarose including 0.6%, 0.7%, 0.8%, 0.9%, and 1.0% in terms of mass fraction. The green bodies were sintered at 1 600 °C for 4 h. The relative density, linear shrinkage, and bending strength of the green bodies, and the density, microstructure, bending strength, and fracture toughness of sintered samples were characterized and analyzed. Results show that comprehensive properties of green bodies made with 4.5%(in terms of mass fraction) agarose solution added to an mass fraction of agarose in the slurry at 0.6% were the best, of which the bending strength was 3.14 MPa, the linear shrinkage was below 4.3%, and the relative density is 57.3%. For sintered bodies, the best fracture toughness was 5.63 MPa m^(1/2), and the optimal density was 5.88 g cm^(-3).

Gel—casting法制备氧化锆陶瓷

对ＺｒＯ２注凝成型工艺中分散剂、固相体积含量对浆料流度性的影响进行了研究。

Effect of Bi_2O_3 Additives on Properties of La_(0.7)Ca_(0.3)CrO_3

Sintering characteristics of Ca-doped lanthanum chromite [La(Ca)CrO_3] powder, prepared by gel-casting process were studied by measuring density and the evaluation of micro structural information. Bi_2O_3 is found to be an effective sintering additive for this material. The amount of Bi_2O_3 is altered to investigate Bi_2O_3 effect on the properties of La_(0.7)Ca_(0.3)CrO_3. The amount of 10% (mass fraction) Bi_2O_3 is suitable to increase sinter-ability of La_(0.7)Ca_(0.3)CrO_3. Increased concentration of point defects arising form substitution of Bi in La site is the plausible cause of enhanced sintering. Measurement of electrical conductivity and thermal expansion coefficient indicate that the doping of Bi_2O_3 does not have any significant effect on these properties.

Enhanced electrical property of graphite/Al_(2)O_(3) composite fabricated by reductive sintering of gel-casted body using cross-linked epoxy polymer

In the present study,graphite/alumina composites are fabricated via reductive sintering of gel-casted green bodies with structurally controlled cross-linked epoxy polymers for the first time.The cross-linking degrees of polymers are tuned by the amount ratio of epoxy monomer/polyvinyl alcohol cross-linker utilized in gel-casting process.Superior electrical properties with respect to 5-fold enhanced electrical conductivity and 2-fold higher carrier mobility are successfully achieved in graphite/alumina composite fabricated from cross-linked epoxy polymer,whose phenomenon is attributed to the excellent conductive path in ceramic matrix established by highly uniform network with improved graphitization degree.

A strategy for improving sinterability and electrical properties of gadolinium-doped ceria electrolyte using calcium oxide additive

In this study,Gd and Ca co-doped ceria electrolytes with the compositions of Ce_(0.8)Gd_(0.2-x)Ca_(x)O_(2-δ)(x=0-0.08) were prepared by a novel gel-casting method.The effects of the addition of Ca on the phase compositions,sintering behavio r,and electrical prope rties of samples were investigated.According to the scanning electron microscope results and relative density measurement results,it is found that the addition of particular quantity of CaO can promote the sintering densification with a uniform grain growth.When the sintering temperature is 1400℃,the sample with 6 mol% addition of Ca has the highest relative density,which reaches 98.5% of the theoretical density.The electrical properties testing results confirm that the electrical conductivity of the samples can be improved significantly by doping appropriate CaO content.The maximum conductivity of 0.082 S/cm can be obtained at 800℃ in the Ce_(0.8)Gd_(0.12)-Ca_(0.06)O_(1.87) sample.It suggests that CaO can be used as an effective sintering aid and a codopant on the optimization of electrical properties for ceria-based electrolytes.

Doping Effect of Bi3+ on the Properties of YAG:Ce3+,Mn2+ Phosphor Ceramics for Warm WLEDs

A series of Bi^(3+)-doped YAG:Ce^(3+), Mn^(2+) ceramics was synthesized successfully by gel-casting method and structurally characterized by XRD and SEM. The doping effect and related mechanism of Bi^(3+) upon the luminescent property were studied. It can be assigned to the energy transfer of multipolar interaction from Bi^(3+) to Ce^(3+), leading to the improvement of emission intensity about 58% for 0.0001 Bi^(3+) and 0.05 Mn^(2+) doping. In addition, the emission is significantly red-shifted with the peak at 590 nm for the Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic specimen with in-line transmittance 81.6% at 1100 nm. The LED module assembled from Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic owns correlated color temperature(CCT) of 3960 K and luminous efficiency(LE) of 92 lm/W, implying that doping Bi^(3+) shows a good sensitization effect in the YAG:Ce^(3+), Mn^(2+) ceramic system and further serving as an attracting phosphor candidates for warm WLEDs applications.

Efficient MgO-doped CaO sorbent pellets for high temperature CO_(2) capture

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation.The effect of Na^(+) and MgO on the structure and CO_(2) adsorption performance of CaO sorbent pellets was elucidated.MgOdoped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO_(2) adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents.The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles.The presence of mesopores and macropores resulted in appreciable change of volume from CaO(16.7 cm^(3)·mol^(-1))to CaCO3(36.9 cm^(3)·mol^(-1))over repeated operation cycles.Ca2Mg1 sorbent pellets exhibited favorable CO_(2) capture capacity(9.49 mmol·g^(-1)),average adsorption rate(0.32 mmol·g^(-1)·min^(-1)) and conversion rate of CaO(74.83%) after 30 cycles.