Sintering and crystallization behaviors of a LZS glass-powder were investigated by means of thermal shrinkage, differential thermal analysis, X-ray diffraction as well as density and mechanical properties measurements. The melted glass, 9.56Li2O.22.36ZrO2.68.08SiO2(wt%) first was cast into water to provide a frit for milling. The milled glass powder (mean particle size 5.0 µm) was then uniaxially pressed at 100 MPa and the obtained samples were isothermally sintered in the 800-950°C temperature range in air for appropriated time intervals (15-120 min). Sintering was found to start at about 640°C and crystallization took place just after completion of sintering and was almost complete at 920°C. The glass powder compacts crystallized into lithium and zircon silicates so that glass-ceramics with relative densities between 84 and 99% were obtained reaching maximum hardness and bending strength values of 8 ± 0.5 GPa and 214 ± 20 MPa, respectively.
Physical and mechanical properties of a glass-ceramic belonging to the LZS (Li2O-SiO2-ZrO2) system were investigated by dilatometric analysis, differential thermal analysis, X-ray diffraction and measurements of density, hardness, bending strength, modulus of elasticity and fracture toughness. The obtained glass-ceramics showed ZrSiO4 and Li2Si2O5 as main crystalline phases, relative densities between 84 and 99%, maximum hardness, bending strength, modulus of elasticity and toughness of 8±0.5 GPa, 214±20 MPa, 115±0.42 GPa and 3.65±0.21 MPa.m1/2, respectively.
In this work suspensions containing natural amorphous silica fibers (NASF), amorphous silica gel and nanometric colloidal amorphous silica were prepared and rheologically analyzed. The suspensions were prepared by varying the volume percentage of solids between 22 and 32%, ammonium polyacrylate (APA), as dispersant, from 0 to 5% and polyvinyl alcohol (PVA), as binder, between 1 and 3.5%. The mixtures were obtained in a propeller mechanical mixer and formed by slip casting. The results of rheological characterization indicated that the suspensions with 30% solids, 4% dispersant and 3% binder were those that showed a stable rheological system and suitable for processing by slip casting.
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