KＡＮＧ Jing-rui ZＨＡＯ Ya-bin ZＨＡＯ Ying-na
（North China University of Science and Technology Yisheng College，Tangshan Hebei 063009, China）
【Abstract】Microcrystalline glass is a kind and architectural glass. When preparing bioglass material, low sintering temperature in microcrystalline glass causes low degree of densification, difference of bond strength between particles, even “slag” problems; Thus, the research progress of bioactive glass-ceramic material by low temperature sintering has been reviewed. We are analyzing the status quo, the crystallization mechanism and expectation.
【Key words】Low temperature sintering; Microcrystalline glass; Crystallization; Expectation
０ Introduction
Microcrystalline glass plays a role in mechanical properties, biological activity of bone replacement and repair materials. People want to find a sintering temperature, which will not affect the practical activity of microcrystalline glass, can achieve the materials needed to fit in more ways again. The present study in some of the microcrystalline glass showed that sintering temperature limits clinical application, though it has good biological activity, mechanical properties and machinability. And we can see, exploring the low temperature sintering microcrystalline glass is very promising.
1 Main glass systems research of low temperature sintering glass-ceramics
Microcrystalline glass can form stable chemical bonding with bone tissue, form a good hydroxyapatite implant site layer rapidly, and it has good affinity, non-toxic.It is helpful for human.
Chen lei, et al[1], show the low temperature sintering A/W.ZTA. In the system of SiO2-CaCO3-Mg(NO3).6H2O-NH4H2CaF2-CaF2 based on the use of stretch forming process, obtain synchronization of ZTA material and HAP under low temperature sintering.
Rong-guang sun and others[2] discovery the system of 3ZnO2-2B2O3 and Al2O3 produces chemical reaction, the formation of ZnAl2O4 while 3Z2B sinters at low temperature of 850~950 ℃, precipitating the main crystal phase. At the same time 3ZnO2-2B2O3will be densification, the 3ZnO2-2B2O3 glass and Al2O3 system microwave dielectric properties can be improved.
Isabelle Denry others[3] study the influence of sintering temperature different ratio between Ca and Al in glass system of SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2.As it showed that the best sintering temperature range 775℃ to 900℃, while the ratio reaches 98.99±0.04% and 91.31±0.10%.
2 Study on low temperature sintering glass-ceramics with crystallization and mechanism
YuBing, kaiming liang, Gu Shouren[4] use differential thermal analysis (DTA). ZrO2 on the glass crystallization activation energy were analyzed and the influence of ZrO2 causing glass crystallization crystallization index increasing were surveyed based on ZrO2 [5-6].
We can describe a general inquiry framework routine.
The Johnson-Mehl-mostly Awamic (JMA) equation is mostly approved.
lna（1-x）＝ktn（１）
Among them: x- Crystal integral number when the moment is upto t.
a-Heating rate.
n-Crystal growth index.
k-Crystallization kinetics parameters. It can be expressed as Amhenius type of equation
k=ANexp（－E/RT）（２）
Among them: E- Crystallization activation energy
R-The universal gas constant
T-Absolute temperature
A-Constant
N-Number of crystal nucleus
3 Disadvantages and expectations
Though research of low temperature sintering glass-ceramics has been used in clinical, it is still a big difference and inadeq as a new kind of bone substitution materials compared with natural bone union[7-8]：
First of all, glass-ceramic mechanical strength is insufficient by the low temperature sintering method. Biological glass-ceramics in fracture strength, toughness, biological activity and practicality can be further improved；
Then, low temperature sintering glass-ceramic biological performance is not stable. Most of low temperature sintering glass-ceramics contain silicon compounds , affecting the function of cells and tissues around, and is likely to affect ion balance in the body.
Overcoming the shortcomings, giving full play about the excellent properties of low temperature sintering glass-ceramics is a research and development trend between material scientists and medical workers. Microcrystalline materials are of great significance with the development of 3 D printing[9].
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