Esmat M. A. Hamzawy

Sintered Mono-Cordierite Mg2Al4−xBxSi5O18 Glass-Ceramic with B/Al Replacement at the Nano- and Micro-Scale

Sintered glass-ceramics based on cordierite modified glass with partial substitution of aluminum by boron [(Mg2Al4−xBxSi5O18 (x = 1 and 3)] were prepared mainly from natural raw materials. Mono-mineralic cordierite was formed at all the sintering temperatures. The results of infrared spectra confirmed the cordierite presence. The microcrystalline structure shows scattered hexagonal cordierite crystals, either at the micro- or nano-scale, in a glassy groundmass. The microanalysis of the hexagonal crystals indicated the incorporation of some elements in the cordierite structure. The density of the sintered samples was 2.0857 and 1.4857 g/cm 3 and the coefficient of thermal expansion, from room temperature up to 500 ∘C, was in the range from 10.46 and 25.60 × 10−7∘C−1. The microhardness value was 5.64 GPa and 5.90 GPa.

Preparation and Electrical Characterization of Zn-Titanate / Borosilicate Glass Composites

A Composite materials from Zn-titanate/borosilicate glass of 10/0(ZT10), 9/1(ZT9), 7/3(ZT7) and 5/5(ZT5) ratios were prepared. Their XRD, SEM / EDX, electrical and dielectric properties were investigated. Willemite, rutile and Zn2TiO4 composite materials were developed through the sintering process. The incorporation of glass enhances the formation of willemite. The SEM micrographs show clear euhedral micro-size crystals of Zn2TiO4 spinel and willemite embedded in glassy groundmass. The EDX microanalysis shows the incorporation of Al- element into the structure of the formed phases. Both conductivity (σac) and dielectric constant (ε′)

In Vitro Bioactivity of Binary Nepheline-Fluorapatite Glass/Polymethyl-Methacrylate Composite

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Stable Wollastonite-Cuspidine Glass-Ceramic Using Inexpensive Raw Materials

, measured within frequency range 0.2 kHz -1 MHz, and temperature range 298- 573 (K). Glass-free sample showed the highest σac and ε′

Sintered cordierite glass-ceramic bodies

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Effect of TiO2, LiF and Cr2O3 in the Crystallization of Cristobalite and Tridymite in Sintered Glass-Ceramics

. Although, 5/5 sample exhibited relative higher values than those with 9/1 and 7/3. The dielectric constant of 9/1 and 7/3 and 5/5 samples show almost an independent behavior over a wide range of temperatures which was attributed to the micro-sized grains of crystalline phases and restraining effect of rigid glassy matrix. The results of ac conductivity may indicate the dominance of electronic conduction over the ionic transfer one in the studied samples. Therefore they may present good candidates for semiconductor materials in electronic devices.

Nanosized cordierite–sapphirine–spinel glass-ceramics from natural raw materials

In vitro bioactivity of stoichiometric nepheline-fluorapatite glass/polymethyl-methacrylate (PMMA (C5O2H8)n) composite was evaluated. Four glasses of nepheline/fluorapatite with different ratios (75/25, 80/20, 85/15, and 90/10 mole%) were added in 20 and 40  wt.% to PMMA. The composite samples were soaked in simulated body fluid (SBF) for 25 days. A scanning electron microscope with energy dispersive X-ray microanalysis (SEM/EDX) and thin film X-ray diffraction analysis was used to evaluate the composite materials after immersion in SBF. Inductively coupled plasma (ICP) and pH changes were used in the determination of the ions released and the alkalinity, respectively, after the immersion in Tris-buffered solution. Effect of glass filler loading on compressive strength of the cements was also evaluated. The four binary nepheline-fluorapatite glasses/PMMA cements composites are good potential bioactive materials. The compressive strength was between 70.36 ± 6.47 and 97.30 ± 3.90 MPa. In general, decreases of the compressive strength follow the increase of the glass ratio (i.e., 40 wt.%), but all meet that specified by the ASTM F-451.

Effect of Different Concentrations of Titanium Oxide (TiO2) on the Crystallization Behavior of Li2O-Al2O3-SiO2 Glasses Prepared from Local Raw Materials

Transparent glasses within the K2O-CaO-SiO2-F composition were prepared. The influence of CaF2, TiO2, Li2O, Li2O-TiO2 and CeO2 additions on the crystallization of the parent glass has been investigated. Crystallization process gave wollastonite and cuspidine as the major phases whereas; xontolite and traces of miserite were developed as subordinate ones. Wollastonite was developed alone in the temperature range of 800 °C-1100 °C in Li2O-containing the base glass. Wollastonite and cuspidine were stable in the 800-1100 °C range in Li2O+TiO2-containing samples and within the 900 °C-1100 °C range in CaF2 and CeO2 containing samples. The microstructure of the Li2O-containing glass-ceramic showed an interlocked needle in nano-scale wollastonite crystals, while fibrous textures were developed in all other crystallized samples at 1000 °C. The thermal expansion coefficient value of the crystallized samples was between 7.596 to 8.708 X10 −6 °C−1 (20-500 °C) and the higher values reflect the increase of crystallization content of cuspidine and even the traces of miserite. This glass-ceramic is thought to be important in dental laboratories.