Papers by Keyword: Slip Casting

Abstract: Boron Oxide (B₂O₃) was doped in fused silica using slip casting technique. Effects of addition of B₂O₃ on mechanical as well as dielectric properties along with microstructure were studied. It was observed that B₂O₃ acts as devitrification inhibitor by reducing the formation of cristobalite content during sintering of fused silica. Mechanical properties were improved by addition of B₂O₃. Density and flexural strength with (3% by weight) addition of B₂O₃ was 1.89 g/cc and 52MPa respectively.

Abstract: The effect of sintering temperature on physical properties of Setiu clay sediment was studied. The ceramic samples were prepared via slip casting method, and sintered at different temperatures ranging from 900 to 1100°C, with 2 hours soaking time. Morphologies of ceramic samples were characterized using Tabletop Microscope. Shrinkage was determined from measurement of samples before and after sintering process. A good ceramic sample without warping or cracks obtained after casting process and after sintered at different temperatures. The results show that sintering temperatures greatly influence morphology of samples. As sintering temperature increased the grain boundaries between particles become smoother and compacted while pores shrunk due to the densification behavior. A considerable increased in shrinkage from 5 to 20% were observed with increasing temperature from 900 to 1100°C. As conclusion, Setiu clay sediment are suitable for production ceramic products and 1000°C can be consider the best sintering temperature in terms of quality of products and production costs.

Abstract: The rheology of A96% alumina slips and the physical and mechanical properties of slip cast samples were studied. The slips had a constant solids loading of 40 wt% alumina and a polyvinyl alcohol (PVA) content of 0-3 wt%, as a binder. The rheological behavior and viscosity of the slips were examined to determine the flowability of the slips necessary for the casting process. The slips were prepared by ball milling and the bend bar samples were cast in plaster molds. The green densities and the flexural strength of the bars were measured, and the fracture surfaces were examined by scanning electron microscopy. It was found that the slip viscosity increased with an increase of PVA content. The green flexural strength also increased to a maximum value of 0.52 MPa with increasing PVA up to 2 wt%. The further addition of PVA decreased the flexural strength. The green density did not significantly change with the PVA content, however the samples produced using 3 wt% PVA showed the lowest percentage of theoretical density of 41%. The fracture surface of the 3 wt% PVA sample showed numerous large pores compared with the other samples. Therefore, in this study it was concluded that there is in optimal amount of PVA to produce the highest green density and flexural strength of cast samples. Excess PVA reduced the flowability of the slip and resulted in excess porosity, which decreased the green density and deteriorated the flexural strength.

Abstract: A laminate composed from alumina and mixture of alumina and 5 vol.% of SiC as well as standards with composition of each layer were prepared using a slip-casting method for green body preparation with following spark plasma sintering. The laminate had a sharp interface between layers and no delamination was observed. Prepared materials were characterized in terms of their microstructure, hardness and fractographic analysis. Because of supposed ballistic potential all prepared ceramics were also subjected to depth of penetration testing.

Abstract: In this paper transparent chromium and neodymium co-doped YAG ceramics were prepared by slip casting and vacuum sintering using high purity Al₂O₃, Y₂O₃, Nd₂O₃ and Cr₂O₃ powders. After mixing the high purity Al₂O₃, Y₂O₃, Nd₂O₃ and Cr₂O₃ powders under the appropriate percentages, pure phase Cr-Nd-doped YAG powders were preparated via calcining at 1300°C for 2 hours. The slurry with the solid content of 40% was casted by self-pressure slip casting under 25°C and 60% humidity to obtain green body. The green body was dried for 96 hours at 33 °C and 75% humidity and then sintered at 1800 °C for 10 hours in vacuum to obtain Cr,Nd:YAG ceramics finally. The transmittance of 1.0 at.%Cr,1.0 at.% Nd:YAG is nearly 80% at 1064nm, and two absorption peaks of Nd³⁺ can be seen near 760 nm and 808 nm.

Abstract: The effect of slip degassing on the microstructure and mechanical properties of slip cast and reaction bonded Si₃N₄ was studied. The slip was prepared by aqueous ball milling of silicon (Si) powder. Hydrogen bubbles, a result of Si oxidation during milling, were degassed from the slip using a combination of vacuum and heat. The slip was then cast into a plaster mould to obtain rectangular green bodies. The Si green samples were sintered in a nitrogen atmosphere at 1500°C to convert the Si to Si₃N₄. After that the nitrided samples were polished to dimensions of 3 x 4 x 30 mm. The density, porosity, flexural strength, phase content and microstructure of the sintered samples were studied. The results showed that the degassing process increased the slip density. After casting and subsequent nitridation, it was found that the average apparent density of the samples increased from 2.89 to 2.95 g/cm³, the porosity decreased from 52.9 to 49.5 %, and the flexural strength increased from 8.1 to 9.3 MPa, when the degassed slip was used. A microstructural examination showed that the pores in the samples were filled with whiskers, which most likely resulted from a vapor phase growth mechanism. The samples produced from the degassed slip tended to have fewer whiskers, due to the reduced pore size and volume. A comparison of the XRD patterns showed no phase differences between the samples. The appearance of Si₂N₂O, and SiC likely resulted from the reactions between O₂ and C impurities with Si₃N₄.

Abstract: Slip/starch casting consolidation (SSCC) is a technique for obtaining porous ceramics, which joins the forming process by starch consolidation with the slip casting method. In this work, a slip which contains ceramic powders, starch and dispersant, is poured into a porous mold and is taken to an oven so that the gelling process occurs. After sintering, it is noticed that the ceramics show different characteristics from the ones obtained exclusively by slip casting or by starch consolidation. Alumina ceramics were produced by using the three methods presented in this work. The ceramics were characterized by apparent porosity, mechanical resistance and scanning electron microscopy. The ceramics produced by SSCC presented the highest mechanical resistance value (289 MPa), while the ones produced by starch consolidation and slip casting presented values of 126 MPa and 191 MPa, respectively.

Abstract: Ceramic materials have particular properties when compared to other classes of materials, exhibiting poor ductility as an example. Slip casting is a widely used ceramic forming technique, and already established in the literature and in the ceramic industry. This study aims to present slip casting as a processing route for producing hydroxyapatite (HA) struts, and show the thermal phase stability. The ceramic suspension was produced and stabilized with hydroxyapatite powder, deionized water and polyethylene glycol 400. The slip was poured into gypsum mold. The green bodies were heat treated at 900 and 1100°C. Hydroxyapatite was the only phase present in all samples, before and after heat treatments. Density measurements showed that the densification was higher for the ceramic bodies sintered at 1100°C, when compared to the ones calcined at 900°C.

Abstract: The connectivity of pores in the hydroxyapatite scaffold was quantitatively estimated by the infiltration of a setting resin in the scaffold and was evaluated by counting the number of pores filled with resin. As pore filled resin indicated the connection with at least one neighboring pore and outside, the volume fraction of the filled pores corresponded to the connectivity previously defined. For the specimen with 88% of connectivity, the scaffold successfully showed cellular migration and bone growth even at the deep part of the scaffold by the in vivo test. Thus, the connectivity evaluated in this study is a useful criterion for the prediction of successful cellular migration.

Abstract: A lotus type-porous copper will be used to substitute wick materials from tabulate coral capillary for heat pipe applications. The lotus type-porous material are normally fabricated using Gasar process, in which unidirectional solidification was applied to the metal-eutectic systems to obtain long cylindrical pores in the direction of solidification. A new process is proposed to fabricate the lotus type-porous material using slip casting and sintering. As an initial work, this paper is aimed to obtain appropriate processing parameters of fabrication of lotus-type porous copper using slip casting and sintering techniques. Nylon strings were used as pore formers to form cylindrical pores. They were coated with copper slurry consisting of copper powder and binding agent. The coated nylon strings were arranged in a mold and the slurry were poured. After drying, these castings were sintered at various sintering temperatures and sintering times. The results showed that starch as the binding agent is superior to PVA. The mixture of starch-water with starch content of 97%, the copper slurry with copper content of 50% by volume, the copper powder size of 200 µm, the sintering temperatur of 900°C, and the sintering time of 60 minutes are able to produce lotus-type porous copper similar to that produced through Gasar process.