Papers by Keyword: Boron Trioxide

Abstract: Al₈B₄C₇ ceramic powder was successfully synthesized via a gas-solid reaction method using aluminum, boron trioxide and activated carbon as the starting materials. The effects of synthesis temperature and the amount of B₂O₃ addition on synthesis of Al₈B₄C₇ were investigated. The results indicated that the optimized process for preparing the Al₈B₄C₇ was that the mixtures were heated at 1800 °C for 2 h in flowing argon atmosphere. With the heated temperature increasing, the Al₈B₄C₇ content was decreased in the products. And 0.5 molar excess of B₂O₃ addition promoted the formation of Al₈B₄C₇. The heating samples at 1800 °C had a hexagonal plate-like morphology with ~100 μm in size.

Abstract: A new experimental porous glass ceramic coating for dental implants was prepared with a new formula consisted of a sintered glass ceramic based on alumina, silica glass and boron trioxide. The resultant sintered objects were anodized by one step anodization method at a constant potential of 40V and at a temperature of 22°C. X-ray diffraction analysis was performed to investigate the phase structure of the new material in addition to SEM investigation for surface texture and pores size and distribution. The new experimental material was subjected to failure under universal testing machine for compressive strength. The results showed a promising material to use as coating for implants as X-ray diffraction exhibited an amorphous phase diagram for the material structure whereas SEM results revealed that the pores in the specimens prepared by anodization method were highly ordered and the mean average pore size was 6.5-8.5 nm. The compressive strength test showed that the test-porous glass ceramic coating has a mean numerical value of up to 7.5 MPa which indicates an ambitious result for the new material.

Abstract: The protection coating, which was used on graphite anode, was developed. The materials were SiO2, B2O3 and soluble glass as binder. The micrographic pattern, the phase composition and the components of borate glass coating were analyzed. The results indicated that the coating was morphology of borate glass at 700~850°C, the components were SiO2, and B2O3 from XRD analysis, the coating could permeate into the pores of the graphite anode and seal the cracks developed by the coating, and it was adhesive strongly to the graphite anode from SEM analysis. The effects of the temperature and time on oxidation weight loss ratio and oxidation rate of graphite anode coating were observed and analyzed. The mechanism of oxidation resistance of the coating layer was explained. In addition, the thermal cycle experiments with the borate glass coating were done at 800°C and 850°C, and the results demonstrated the sample had good ability of resistance to thermal shock.

Abstract: Studies on xCuO-(1-x)As2O3-0.7B2O3(0.01≤x≤0.05) (G1-G5: x = 0.01, 0.02, 0.03, 0.04, 0.05) glasses were done using varieties of structure sensitive techniques. The powder X-ray diffraction (XRD) studies show the formation of glasses in the composition. The IR spectral results show the presence of Cu-O bond, planar [BO3/2] and [BO3 -n](n=1, 2, 3) units and tetrahedral {BO4/2]- units. The magnetic susceptibility results show Curie-Weiss behaviour in the range 4.2-400 K. The calculated values of the exchange integral from the Weiss constant obtained form the linear fit of the Curie-Weiss law are found to be in the range 5.22-29.50 meV. From the trend of the gmatrices of gơ>g⊥>ge (ge =2.0023) obtained from electron paramagnetic resonance (EPR) lineshapes simulation we conclude that the paramagnetic site in these glasses is Cu2+(3d9) which is in a tetragonally elongated octahedron [O1/2-CuO4/2-O1/2] exhibiting Jahn-Teller distortion having D4h symmetry with orbital singlet 3dx2-y2 (2B1g) as the ground state.