Effect of Glass Ceramic Crystallinity on the Formation of Simulated Apatite Layers

In silicate glasses the kinetics of apatite layer formation is usually rapid but the adhesion to the base glass is poor. Glass ceramics promote a stronger bonding between layer and substrate but decrease the rate of the apatite layer formation. In this work a glass of composition (wt%) 54,89%C3P-24,81%SiO2-20,30%MgO has been studied. This glass was heat treated at four temperatures (840 °C, 870 °C, 890 °C and 910 °C) to obtain glass ceramics with different contents of the same crystalline phase. A calcium magnesium phosphate phase was formed in all glass ceramics in a volume percent increasing with temperature. The apatite layer precipitated after immersion in simulated body fluid (SBF) formed faster on the glass than on the glass ceramics and a decrease in the amount of apatite formed was observed with the increase in crystallinity. It was generally concluded that heat treatment can turn a reactive glass into glass ceramics of different surface behaviors, from bioactive to quasi bio inert materials.

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The Crystallization and Characterization of Calcium-Magnesium- Aluminosilicate Glass-Ceramics

UNIOSUN Journal of Engineering and Environmental Sciences ◽

10.36108/ujees/0202.20.0260 ◽

2020 ◽

Vol 2 (2) ◽

Author(s):

Z.S. Aliyu

Keyword(s):

Weight Loss ◽

Glass Ceramics ◽

Glass System ◽

Aluminosilicate Glass ◽

Treatment Schedule ◽

Base Glass ◽

Soaking Time ◽

Calcium Magnesium ◽

Hardness Values

Calcium-magnesium-aluminosilicate (CaO.MgO.Al3O3.SiO2) glass-ceramics was developed from the base glass system of the composition 52.00 wt% SiO2, 16.00 wt% Al2O3, 12.00 wt% CaO, 8.00 wt% MgO, 2.00 wt% K2O, 6.00 wt% TiO2, 0.30 wt% NaCl and 3.70 wt% in this study. The study focused attention on the crystallization of CaO.MgO.Al3O3.SiO2 base glass system using 363℃ & 663℃ as nucleation and crystal growth temperatures respectively, and 1 – 4 hours as soaking time. The composition was melted at 1600℃ for 3 hours in a muffle furnace and the molten glass was cast into rods, annealed at 600℃ for 1 hour and finally cooled to room temperature. Due to the presence of impurities in the starting materials, the glasses produced have a brownish physical appearance. Base glasses were crystallized into glass-ceramics using double-stage heat treatment schedule, and XRD and SEM were used to characterize the produced samples. The XRD identified the crystalline phases precipitated in the residual glass matrix of the sample soaked for 4 hours as albite, quartz, wollastonite and witherite. The SEM result revealed that the microstructure of the sample is characterized by dense, circular-like and needle-like clusters alongside micro-sized voids dispersed in the residual glassy phase matrix. The density and hardness values were found to increase while weight loss decreased with increase in soaking time across the samples. The sample soaked for 4 hours has the lowest weight loss but with the highest density and hardness values making it suitable for use for abrasion due to its excellent properties.

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Hardening Effect and Electron Metallography of Precipitation in Uranium with Small Additions of Titanium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096151 ◽

1972 ◽

Vol 30 ◽

pp. 580-581

Author(s):

D. H. Johnson ◽

A. M. Ammons

Keyword(s):

Perchloric Acid ◽

Graphite Crucible ◽

Alpha Phase ◽

X Ray Diffraction ◽

Volume Percent ◽

Thin Foils ◽

Heat Treated ◽

Matrix Interactions ◽

Sponge Titanium ◽

Kinetics Of

Uranium-0.5 wt.% titanium and U-1.0 wt.% Ti alloys are alpha-phase, martensitic uranium alloys which show large increases in strength due to precipitation of U2Ti on aging at moderate temperatures. Hardness, electron microscopy, and X-ray diffraction were used to study growth kinetics of the U2Ti precipitation and the precipitate-matrix interactions.The alloys were induction melted from high-purity uranium and sponge titanium in a zirconia-coated graphite crucible and bottom poured into a zirconia-coated mold; subsequently, the alloys were solution treated at 800°C for one hour in a vacuum of 5 x 10-6 torr and water quenched. Small specimens were then heat treated at temperature in a vacuum of 5 x 10-6 torr and water quenched.Thin foils were prepared by a modification of the two-step electrothinning procedure of DuBose and Stiegler from rods using 15 volume percent perchloric acid and 35 volume percent butyl cellosolve in methanol for initial thinning and a bath of 6 volume percent perchloric acid cooled with a dry ice-acetone mixture for the final electropolishing.

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Structural Role of Strontium Oxide in Modified Silicate Glasses

10.21203/rs.3.rs-443520/v1 ◽

2021 ◽

Author(s):

Gomaa El-Damrawi ◽

Rawia Ramadan ◽

mohamed Biomey

Keyword(s):

Calcium Phosphate ◽

Network Structure ◽

31P Nmr ◽

Composition Range ◽

Glass Ceramics ◽

Silicate Glasses ◽

Strontium Oxide ◽

Amorphous Network ◽

Heat Treated

Abstract In the composition range of x= 0-15 mol%, glasses in the system 24.5Na2O.24.5CaO.6P2O5.xSrO.(45-x)SiO2 have been studied. The glasses are transparent and have an amorphous network structure when they are as prepared. Heat treated glasses, on the other hand, are transformed into opaque white glass ceramics with a highly crystalline network structure. The main well-formed crystalline species in material bioactivity were apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate [Ca2Sr(PO4)2. Increasing SrO improves material crystallite and increases the host glass matrix's hardness. The modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one is thought to be the cause of the change in XRD spectra, 31P NMR chemical shift, and hardness number as SrO increases. These species help to improve material properties and hardness.

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Preparation and Characterization of Yttrium Iron Garnet Glass-Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.785-786.767 ◽

2013 ◽

Vol 785-786 ◽

pp. 767-770 ◽

Cited By ~ 1

Author(s):

Jian An Liu ◽

Mei Mei Zhang ◽

Xue Na Yang

Keyword(s):

Saturation Magnetization ◽

Yttrium Iron Garnet ◽

Glass Ceramics ◽

Heat Treating ◽

Yttrium Iron ◽

Base Glass ◽

Heat Treated ◽

Iron Garnet ◽

Annealed Glass

Yttrium iron garnet (YIG) glass ceramic was successfully synthesized by aqueous aolution-melt method. The as-prepared base glass was heat treated at different temperature and investigated by XRD and VSM. The annealed glass at 580°C shows the formation of magnetite structure with saturation magnetization of 10.6A·m2/kg.And the annealed glass heat treating at 850°C for 6h, show the formation of garnet structure with saturation magnetization of 18.2A·m2/kg.

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Direct observations of radiation-enhanced transformations in glass

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075543 ◽

1983 ◽

Vol 41 ◽

pp. 354-355

Author(s):

J. F. DeNatale ◽

D. G. Howitt

Keyword(s):

Glass Matrix ◽

Diffusion Mechanism ◽

Bubble Formation ◽

Silicate Glasses ◽

Phase Decomposition ◽

Direct Observations ◽

Thin Foils ◽

Oxygen Bubble ◽

Electron Energy Loss ◽

Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

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Kinetics of compact layer formation and growth of 1,10-phenanthroline at the electrode surface

Journal de Chimie Physique ◽

10.1051/jcp/1990871597 ◽

1990 ◽

Vol 87 ◽

pp. 1597-1607 ◽

Cited By ~ 2

Author(s):

L Benedetti ◽

M Borsari ◽

C Fontanesi ◽

G Battistuzzi Gavioli

Keyword(s):

Electrode Surface ◽

Layer Formation ◽

Compact Layer ◽

Kinetics Of

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Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Journal of Electronic Materials ◽

10.1007/s11664-021-09067-4 ◽

2021 ◽

Author(s):

A. Leineweber ◽

M. Löffler ◽

S. Martin

Keyword(s):

Phase Equilibria ◽

Electron Backscatter Diffraction ◽

Metastable Phase ◽

Stable Phase ◽

X Ray Diffraction ◽

X Ray ◽

Heat Treated ◽

Ordered Phases ◽

Backscatter Diffraction ◽

Kinetics Of

Abstract Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

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