Fused Silica Powders Research Articles

Light weight silica tiles through foam casting method

The possibility of making porous silica tiles starting from inexpensive fused silica powder using a direct foaming process has been examined. Aqueous slurry of silica with appropriate surfactants and binders have been allowed to foam by entraining air, following which it was cast, dried, and subsequently sintered at 1100 °C. The role of slurry composition and foaming duration, on the green and final density of foams has been studied. Silica foams with density as low as 11% of the theoretical density, and containing interconnected, primarily spherical pores with average size in the range of 50–2000 μm have been fabricated. The porous silica with densities between 18% and 62% of the theoretical value, have shown Young's modulus and compressive strengths in the range of 120–380 MPa and 0.5–3.3 MPa, respectively. A surface densification process, that can seal off the surface pores and provide a smooth exterior to the tiles, has also been established.

Development of ZrO 2/SiO 2 bioinert ceramic coatings for biomedical application

Gas tunnel-type plasma spraying (GTPS) was employed to deposit ZrO 2/SiO 2 bioinert ceramic composite coatings with an appropriate thickness on SUS 304 substrate. Zirconia and fused silica powders, with equal wt%, have been mixed together in ceramic pot for 30 min and internally fed in the plasma jet. The composite coatings were sprayed at two different gas flow rates (120 and 150 l/min) and constant vortex arc current of 450 A and gun current of 50 A. The microstructure of as-sprayed coatings was examined by scanning electron microscope. Elemental analysis was achieved for the composite coatings using EDS analysis unit which is attached to SEM. Phase structure was investigated by X-ray diffraction. The hardness and abrasive wear test of the coatings were investigated. The biological property of the coatings was examined by immersing the as-sprayed coatings in simulated body fluid (SBF) solution for 20 days at 36.5 ∘C. The growth of apatite (HA) on the coatings surfaces was observed by SEM and EDX analysis.

내화물 응용을 위한 산화물 재료들과 탄소와의 고온 반응거동

High temperature reaction behaviors of various oxide materials (such as bauxite, pyrophyllite, mullite and fused silica powders) used in the refractory materials for tap-hole plugging of blast furnace were investigated with varying temperature in the carbon surrounding. Kinetics of carbothermal reduction of SiO₂ for forming SiC with high corrosion resistance were strongly dependent on it’s crystalline phase. SiC generation yield increased with increasing catalyst amount in oxide regardless of generated SiO gas amount at temperature of ＜1500℃. However, in case of fused silica over 1500℃, SiC generation yield was dominantly influenced by SiO amount without catalyst effect. Bauxite showed the most effective carbothermal reduction reaction, since bauxite have a large amount of catalyst and well-dispersed SiO₂ phase in oxide matrix.

Fabrication and characterization of plasma-sprayed HA / SiO 2 coatings for biomedical application

Fused silica powder has been mixed with hydroxyapatite (HA) powder and plasma sprayed by using gas tunnel-type plasma jet. The influence of silica content (10 wt% and 20 wt%) on the microstructure and mechanical properties of HA–silica coatings was investigated. For investigating the microstructure and mechanical properties of HA–silica coatings, SUS 304 stainless steel was used as substrate material. The spraying was carried out on roughened substrate in an atmospheric chamber. Scanning electron microscope micrographs of cross-sectioned HA/SiO 2 coatings showed that the sprayed HA coatings with 10 and 20 wt% SiO 2 have dense structure with low porosity compared to the pure HA coatings. On the other hand, as the amount of silica was increased the coatings became denser, harder and exhibited high abrasive wear resistance. The presence of silica significantly improved the adhesive strength of HA/SiO 2 coatings mainly due to the increase in bonding strength of the coating at the interface.

Highly filled particulate thermoplastic composites: Part I Packing density of irregularly shaped particles

The packing density of irregular shaped particles greatly affects the properties of highly filled particulate composite materials. The effects of particle size distribution parameters on the packing density of fused silica powder and cristobalite flour powder of different size ranges is reported. Various size distributions, according to the log-normal function, were prepared by sieving and characterized by light scattering, using a Malvern 2600 light scattering instrument. The apparent and tap density of the various powders was used to characterize the packing density. The size distribution width was found to have a major effect on the packing density. In addition, the particle size was found to affect the packing density however, its significance depends on the size range and shape of the particles. Mixtures of powders, each having a different size distribution, behave differently.

A Model for Thermal Conductivity of Granular Porous Media

This note describes an improved model for estimating thermal conductivity of granular porous media, in which radiation and convection heat transfer effects can be considered negligible. Because the model proposed is semi-empirical in nature, only the thermal conductivities of solid and fluid phases and the porosity are required for estimation purposes. With the minimal property data required, inherent assumptions are that both fluid and solid phases are homogeneous and contact conductance is not a parameter. Use of the model gives thermal conductivity estimates that are between the bounding estimates discussed by Maxwell and Hashin and Shtrikman. The authors illustrate here the utility of the model by comparing predictions with experimental data for a porous medium composed of fused silica powder and air.

Characterization of fused silica powders

Characterization of fused silica powders