Sintering Behavior and Machinability in Mica Glass-Ceramic of the System SiO2−Al2O3−MgO−K2O−B2O3−FSiO_2-Al_2O_3-MgO-K_2O-B_2O_3-F

Mica glass-ceramic was prepared by sintering method from in the $SiO_2-Al_2O_3-MgO-K_2O-B_2O_3-F_2$ system. The sintering behavior and machinability of a glass-ceramic composition were examined. The starting materials were mixed and milled in an alumina ball mill for 2 h. Then the powders were sieved to obtain grain sizes smaller than 75 μm. For the shaping process, disc samples were prepared by pressing at 100 MPa. The pressed discs were sintered at temperatures in the range from 900 to 1200C for 2 h in an electric furnace using a heating rate of 5°C/min. X-ray diffraction analysis, scanning electron microscopy, and machinability tests for characterization were performed on sintered samples. The results showed that all samples exhibited similar phases formation and good machinability

The Effect of Perlite Addition on Erosive Wear Behavior of Alumina Ceramics

In this study, the effects of perlite addition on mechanical properties and wear resistance of alumina ceramics were investigated. Alumina powders including perlite 5%, 10%, 15%, 20% and perlite free were prepared. These powders were shaped as rectangular by using uniaxial pressing system under the load of 100 MPa. The samples were sintered at 1400°C-1550C for 2 h and were subjected to some mechanical tests such as hardness and fracture toughness. X-ray diffraction analysis was employed to determine the crystalline phases. Bulk densities of the samples were measured. In addition, erosive wear test was performed to investigate the erosive wear resistance of the samples. The wear test results were presented depending on different sliding speed and sintering temperature. These results showed that perlite addition has a positive effect on erosive wear resistance of the alumina ceramics, generally

Glass and Glass-Ceramics Produced from Fly Ash and Boron Waste

In the current study, the effect of boron waste addition on some properties of fly ash based glass and glass-ceramics were investigated. The powder compositions including 10, 30, and 50 wt% boron waste was prepared. All the investigated compositions were melted at 1500C by using electrical furnaces. Melting structures were cast into the graphite mold. Thus, fly ash-boron waste based glass materials were produced. To transform the glass-ceramic, crystallization process was performed. Crystallization and glass-transition temperatures were determined by differential thermal analysis. Highly dense and crystalline materials, predominantly composed of diopside and augite together with tincalconite and residual glassy phase, were detected by X-ray diffraction analysis after heat treatment at 800, 900, and 1000C for 1 h. For the glass and glass-ceramic samples, mechanical tests such as hardness and fracture toughness were realized. A boron waste addition has a positive effect on the hardness of the specimens unlike the fracture toughness results. Furthermore, produced glass-ceramic materials were characterized via scanning electron microscopy

Bond Strength of Basalt Based Glass-Ceramic Coatings

In the present study, powders produced from the volcanic basalt rocks were coated on pre-coated AISI 1040 steel with Ni-5% Al bond coat by atmospheric plasma spray coating technique. The coated specimens were characterized by optical microscopy, scanning electron microscopy, metallography and X-ray diffraction. Bonding strength of coatings was evaluated in accordance with the ASTM C-633 method. Coated basalt material from the APS coating system was determined in the glassy amorphous state by X-ray diffraction analysis. The coated samples were heat-treated at 800C for 1-4 h for crystallization. The phases formed in the basalt base glass-ceramic coatings were augite, Fe-diopside, anorthite, and andesine which were detected by X-ray diffraction analysis. Basalt based glass-ceramic coatings include splat, porosity and un-melted particles which were the characteristic of plasma sprayed coatings. Experiment result showed that the crystallization time increase caused the decrease of the bond strengths of the coatings