Crystallization and Thermal Expansion of MgO-Al2O3-SiO2-TiO2 Glass-Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 1635-1638
Author(s):  
Hua Shao ◽  
Kai Ming Liang ◽  
Feng Zhou ◽  
Fei Peng
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Phase Separation ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Treatment Condition ◽  
Glass Ceramics ◽  
Heat Treatment Condition ◽  
Crystallization Sequence ◽  
The Relationship

Crystallization sequence of MgO-Al2O3-SiO2-TiO2 system glass was investigated by means of DTA, XRD, SEM and EDS. The relationship between crystalline phases, heat treatment methods and thermal expansion coefficient (α) were well discussed. The results have shown that: The glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phases. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss and α-cordierite made their appearance successively. The thermal expansion coefficient as a function of the heat treatment condition was studied.

Effect of B2O3 and P2O5 Addition on the Phase Separation and Crystallization of Li2O-MgO-Al2O3-SiO2 Glass-Ceramics

2016 ◽  
Vol 848 ◽  
pp. 243-248 ◽  
Author(s):  
Zhen Hong Bao ◽  
Li Feng Miao ◽  
Wei Hui Jiang ◽  
Jian Min Liu ◽  
Jian Liang ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Phase Separation ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Crystalline Phase ◽  
Raw Materials ◽  
Glass Ceramics ◽  
Lithium Silicate ◽  
Solid State Method ◽  
Main Crystalline Phase

B2O3- or P2O5-doped Li2O-MgO-Al2O3-SiO2 (LMAS) glass-ceramics were prepared by solid state method using Li2CO3, MgO, Al2O3 and SiO2 as the raw materials, B2O3 or P2O5 as the additives. The effects of adding B2O3 and P2O5 on the phase separation, crystallization and thermal expansion coefficient were investigated by means of X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and thermal dilatometer, respectively. The results showed that B2O3 or P2O5 addition could promoted phase separation of glass and increased the size of spherical phase separation droplet. With the addition of B2O3 or P2O5, the crystallization temperatures (Tc) of LMAS system decreased from 764 oC to 726 oC and 764 oC to 750 oC, respectively. However, the crystalline phase compositions did not changed, and β-quartz solid solution (s.s) (Li2Al2Si3O10) was still the main crystalline phase, and lithium silicate (Li2SiO3) and forsterite (Mg2SiO4) were the minor phases. The thermal expansion coefficient (α) of B2O3-doped and P2O5-doped LMAS glass-ceramics in the temperature range 20-600 oC were 5.215×10-6/ oC and 5.008×10-6/ oC, respectively, which were higher than that of LMAS glass-ceramics (α=3.790×10-6/ oC).

Crystallization Behavior and Performance of MgO-Al2O3-SiO2 Glass-Ceramics by Sintering

2010 ◽  
Vol 92 ◽  
pp. 65-71 ◽  
Author(s):  
Pei Xin Zhang ◽  
Li Gao ◽  
Qiu Hua Yuan ◽  
Hai Lin Peng ◽  
Xiang Zhong Ren ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Flexural Strength ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Crystallization Process ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Low Thermal Expansion ◽  
Main Crystalline Phase ◽  
And Performance

The glass-ceramics of MgO-Al2O3-SiO2 system were prepared by sintering technology. The crystallization process of MgO-Al2O3-SiO2 glass-ceramics was investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), and other techniques; the discussion of breaking strength, thermal expansion coefficient and relevant properties at different sintering temperatures was also presented. The results show that: (1) The main crystalline phase isα-cordierite at different sintering temperatures, and the samples show high flexural strength and low thermal expansion coefficient; (2) with the increase of sintering temperature, the content of crystal phase increases, while the thermal expansion coefficient decreases evidently, the flexural strength and tightness density rise up first, then go down.

Effects of Heat-Treatment Temperature on the Properties of Negative CTE Eucryptite Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 123-125 ◽  
Author(s):  
Yong Li ◽  
Qi Hong Wei ◽  
Ling Li ◽  
Chong Hai Wang ◽  
Xiao Li Zhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Heat Treatment Temperature ◽  
Bending Strength ◽  
Sol Gel ◽  
Negative Thermal Expansion ◽  
Treatment Temperature ◽  
Heat Treated

In this paper, negative thermal expansion coefficient eucryptite powders were prepared by sol-gel method using silica-sol as starting material. The raw blocks were obtained by dry pressing process after the powder was synthesized, and then the raw blocks were heat-treated at 600º, 1150º, 1280º, 1380º, 1420º and 1450°C, respectively. Variations of density, porosity and thermal expansion coefficient at different heat treatment temperatures were investigated. Phase transformation and fracture surface morphology of eucryptite heat-treated at different temperatures, respectively, were observed by XRD and SEM. The results indicate that, with the increasing heat- treatment temperature, the grain size and the bending strength increased, porosity decreased, thermal expansion coefficient decreased continuously. Negative thermal expansion coefficient of -5.3162×10-6~-7.4413×10-6 (0~800°C) was obtained. But when the heat-treatment temperature was more than 1420°C, porosity began to increase, bending strength began to decrease, which were the symbols of over-burning, while the main crystal phase didn’t change.

scholarly journals The Relationship Between the Electrical Properties of Thick Film Resistors and the Thermal Expansion Coefficient of the Substrates

1987 ◽  
Vol 12 (4) ◽  
pp. 251-257 ◽  
Author(s):  
Toshio Inokuma ◽  
Yoshiaki Taketa ◽  
Miyoshi Haradome
Keyword(s):  
Thermal Expansion ◽  
Electrical Properties ◽  
Low Temperature ◽  
Thick Film ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Film Resistor ◽  
Thick Film Resistor ◽  
The Relationship ◽  
Resistance Value

The temperature characteristics of RuO2-based thick film resistors on various substratcs having different thermal expansion coefficient have been investigated.It became clear that, if the thermal expansion coefficient of the substrate is larger than that of the thick film resistor, a compression is being exerted by the substrate on the as-fired resistor at low temperature. As temperature rises, the resistance value increases, and the TCR becomes positive.On the contrary, if the thermal expansion coefficient of the resistor is larger than that of the substrate, the as-fired resistor is being stretched by the substrate at low temperature. As temperature rises, the resistancc value decreases, and the TCR becomes negative.

Nanosize Beta-Spodumene Glass-Ceramic Powders Synthesized by Sol–Gel Route

2011 ◽  
Vol 110-116 ◽  
pp. 3844-3848
Author(s):  
Zhuo Hao Xiao ◽  
Wen Yan Luo
Keyword(s):  
Thermal Expansion ◽  
Electron Microscope ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Glass Ceramic ◽  
Sol Gel ◽  
Ceramic Powder ◽  
Average Particle Size ◽  
Glass Ceramics ◽  
Average Particle

Beta-spodumene glass-ceramic powder was prepared by Sol–gel route. Tetraethyl orthosilicate (TOES), aluminum nitrate, lithium carbonate were used as starting materials. X-ray powder diffraction (XRD), thermal expansion coefficient (TEC), scanning electron microscope (SEM) and transmission electron microscope (TEM) were utilized to characterize the dried LAS gels and glass-ceramic blocks. The results suggest beta-spodumene is the only crystals phase in the prepared LAS glass-ceramics powder when sintering temperature is 950 °C. The average particle size of the beta-spodumene crystal is about 30 nm with a narrow size distribution both in prepared LAS glass-ceramics powder and block. The thermal expansion coefficient of moulding pressed blocky LAS glass-ceramics is lower than 0.6×10-6 oC-1.

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