Influence of B2O3 on Dielectric, Mechanical, and Thermal Properties of MgO-Al2O3-SiO2 Glass-Ceramics

2019 ◽  
Vol 821 ◽  
pp. 435-439
Author(s):  
Bo Li ◽  
Ke Jing ◽  
Hai Bo Bian
Keyword(s):  
Activation Energy ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Low Temperature ◽  
Flexural Strength ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Mechanical And Thermal Properties ◽  
Sintering Process ◽  
Low Thermal Expansion

Low temperature sintered MgO-Al2O3-SiO2 glass-ceramic with high mechanical and low thermal expansion was prepared for package. The remarkable influence of B2O3 addition on the electrical, mechanical, and thermal properties was fully investigated. A small amount of B2O3 promoted the sintering process and improved the densification of MAS. The kinetics via Kissinger method indicated that an appropriate B2O3 content decreased the activation energy and helped the occurrence of crystallization. Due to the increase of crystallinity and indialite phase, B2O3 addition significantly enhanced flexural strength and Young’s modulus. MAS doped with 3wt% B2O3 can be sintered at 900 °C and obtained good properties: σ = 229 MPa, φ = 86 GPa, α = 1.66×10-6 /°C, εr = 5.29, and tanδ = 5.9×10-4.

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.

Improving mechanical and thermal properties of graphite–aluminium composite using Si, SiC and eggshell particles

2019 ◽  
Vol 54 (17) ◽  
pp. 2365-2376 ◽  
Author(s):  
MO Durowoju ◽  
TB Asafa ◽  
ER Sadiku ◽  
S Diouf ◽  
MB Shongwe ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Relative Density ◽  
Coefficient Of Thermal Expansion ◽  
Mechanical And Thermal Properties ◽  
Sem Images ◽  
Plasma Sintering ◽  
Low Thermal Expansion ◽  
Spark Plasma

Graphite–aluminium (Gr–Al) composites are being used for diverse engineering applications because of their light weight, good electrical conductivity and thermal properties. However, their applications are limited by high coefficient of thermal expansion and low microhardness values which can be enhanced by adding cheap and efficient fillers. This paper reports the effect of addition of eggshell (ES) particles on the properties of sintered Gr–Al-based composites. Five different composites (Gr–Al, Gr–Al  +  20 wt.%Si, Gr–Al + 20 wt.%SiC, Gr–Al + 20Si wt.% + 20 wt.%ES and Gr–Al + 20SiC wt.% + 20 wt.%ES) were sintered at a temperature of 540 ℃, holding time of 10 min, heating rate of 52 ℃/min and pressure of 50 MPa using spark plasma sintering system. The sintered samples were characterized based on morphology, microhardness, relative density, coefficient of thermal expansion and electrical conductivity. Based on SEM images, graphite particles of flake-like structure were largely undeformed while Al particles were smaller, round and irregular in shape and fairly uniformly distributed in the composites. The microhardness value of sintered Gr–Al + 20 wt.%SiC + 20 wt.%ES composite was 39.55 HV compared to 30.46 HV for Gr–Al, the least of the samples. The Gr–Al + 20 wt.%SiC + 20 wt.%ES composite also has a very low thermal expansion coefficient (0.98 × 10−5/K) but lowest electrical conductivity at temperature beyond 150 ℃. Highest densification and minimum relative density (94%) were obtained in Gr–Al + 20 wt.%Si + 20 wt.%ES composite. These enhanced performances are largely due to the incorporation of ES particles. This study therefore demonstrated that ESs particles enhanced microhardness and lowered thermal expansion of Gr–Al-based composites which have promising applications in industries especially for thermal management.

β-Spodumene Glass-Ceramic with Anomalous Low Thermal Expansion

2008 ◽  
Vol 39-40 ◽  
pp. 381-386 ◽  
Author(s):  
Akihiko Sakamoto ◽  
Yusuke Himei ◽  
Yoshio Hashibe
Keyword(s):  
Thermal Expansion ◽  
Mechanical Strength ◽  
Ceramic Material ◽  
Glass Ceramic ◽  
Silica Glass ◽  
Coefficient Of Thermal Expansion ◽  
Glass Ceramics ◽  
New Method ◽  
Low Thermal Expansion ◽  
Natural Stones

To survey new method for controlling thermal expansion of glass-ceramic material, we studied the coefficient of thermal expansion (CTE) and the microstructure of β-spodumene glass-ceramics. We found that the CTE of the β-spodumene glass-ceramics is remarkably reduced by introducing interstices at the boundary between the crystalline and glass phases. Despite its relatively low crystallinity (45vol%), a newly developed glass-ceramic showed an anomalous low thermal expansion of 7x10-7 /oC, which compares to that of silica glass. The mechanical strength of this glass-ceramic was at the same level as that of natural stones: marble and granite.

Influence of Bi2O3 on Crystalline Phase Content and Thermal Properties of Åkermanite and Diopside Based Glass-Ceramic Sealant for SOFCs

2017 ◽  
Vol 751 ◽  
pp. 483-488
Author(s):  
Pornchanok Lawita ◽  
Apirat Theerapapvisetpong ◽  
Sirithan Jiemsirilers
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Glass Ceramic ◽  
Crystalline Phase ◽  
Coefficient Of Thermal Expansion ◽  
Glass Ceramics ◽  
Clean Energy ◽  
Softening Temperature ◽  
Quantitative Phase Analysis ◽  
Clean Energy Source

Solid oxide fuel cell (SOFC) is an electrochemical energy conversion device which is considered as clean energy source generator with reliability and relatively inexpensive production cost. One of the most important components for planar design SOFC is the hermetic seal that prevents fuel from leaking out of between the stack of fuel cells. Glass-ceramics are attractive materials as sealing materials for this device. The expected coefficient of thermal expansion (CTE) of the glass-ceramic sealants should be between 9 and 12 x 10−6 K−1. Glass – ceramics based on åkermanite (Ca2MgSi2O7) crystalline phase were reported their high CTE value from about 10 to 11.3 x 10−6 K−1. In this study, glass compositions in the CaO-MgO-B2O3-Al2O3-SiO2 system with varying amounts of Bi2O3 from 0 to 10 wt. % were prepared by conventional melting and investigated their properties. The selected compositions were derived from ternary åkermanite–forsterite–anorthite phase diagram. Phase composition and quantitative phase analysis of glass–ceramics were examined by X-ray diffractometer. The onset of crystallization (Tx) and crystallization temperature (Tc) were measured by DTA. The thermal properties of bulk glass samples and heat treated samples at 900 oC for 2 h which were glass transition temperature (Tg), dilatometric softening temperature (Ts), and coefficient of thermal expansion (CTE) were determined by dilatometer. Furthermore, the long-term stability of their CTE was investigated. The samples were continued to soak at 800 °C for 100 h and observed their change in CTE value. The results found that the åkermanite phase tended to increase with increasing amount of Bi2O3 content.

Preparation and Properties Study of Cu-MoSi2 Composites

2007 ◽  
Vol 534-536 ◽  
pp. 581-584 ◽  
Author(s):  
Xiaoou Yi ◽  
Wei Hao Xiong ◽  
Jian Li
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Mechanical And Thermal Properties ◽  
Matrix Composites ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Powder Metallurgy Process ◽  
Expansion Coefficients ◽  
Metallurgy Process

The particulate dispersive strengthened Cu-MoSi2 composites were prepared by a powder metallurgy process with aim to develop novel copper based composites of reasonable strength, high thermal conductivity and low thermal expansion coefficients. Compacted samples were sintered to over 90% of theoretical density. Microstructure of the composites was investigated by SEM while mechanical properties such as tensile strength, elongation and thermal properties such as thermal conductivity and thermal expansion coefficient (CTE) of the composites were examined as a function of the MoSi2 content and the process of fabrication. A comparative analysis of the mechanical and thermal properties of various Cu-matrix composites currently in use was given and the strengthening mechanisms for the Cu-MoSi2 composites were discussed.

Material and application study for low thermal expansion glass-ceramic CLEARCERAM series

2005 ◽  
Author(s):  
Kousuke Nakajima ◽  
Toshihide Nakajima ◽  
Nobuo Kawasaki ◽  
Yoshiyuki Owari
Keyword(s):  
Thermal Expansion ◽  
Glass Ceramic ◽  
Application Study ◽  
Low Thermal Expansion

Radiation effects on a low‐thermal‐expansion glass ceramic

1987 ◽  
Vol 62 (8) ◽  
pp. 3488-3490 ◽  
Author(s):  
T. E. Tsai ◽  
P. L. Higby ◽  
E. J. Friebele ◽  
D. L. Griscom
Keyword(s):  
Thermal Expansion ◽  
Glass Ceramic ◽  
Radiation Effects ◽  
Low Thermal Expansion

The Effect of Phase Composition on the Mechanical and Thermal Properties of LTCC Material

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000492-000497
Author(s):  
Kostja Makarovič ◽  
Anton Meden ◽  
Marko Hrovat ◽  
Janez Holc ◽  
Andreja Benčan ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Phase Composition ◽  
Flexural Strength ◽  
Mass Fraction ◽  
Major Change ◽  
Multilayer Structures ◽  
Propagation Mechanism ◽  
Mechanical And Thermal Properties ◽  
Thermal Coefficient ◽  
Biaxial Flexural Strength

Low-temperature co-fired ceramic (LTCC) is an important material in the production of ceramic multilayer structures. Large and complex multilayer structures are usually fired at higher temperatures and/or longer firing times compared to the relatively thin LTCC tapes. The firing conditions of LTCC determine the phase composition and the microstructure, which both influence the physical characteristics, such as the mechanical and thermal properties. In this work the effect of the phase composition on the biaxial flexural strength and the temperature coefficient of expansion of the DuPont 951 LTCC is presented. The samples were fired at different temperatures and times to obtain different phase compositions. The phase composition, especially the mass fraction of anorthite, was correlated with the biaxial flexural strength and the thermal coefficient of expansion (TCE). A very long firing time, i.e., 100h at 800 °C, yields, apart from crystalline anorthite, the cristobalite phase. The anorthite that crystalizes from the glass phase in a dense LTCC material changes the crack-propagation mechanism and improves the biaxial flexural strength of the material. The major change in the biaxial flexural strength is observed when the anorthite phase appeared. The increasing mass fraction of anorthite does improve the biaxial flexural strength less drastically. With the increasing mass fraction of the anorthite, decreases of the TCE of the material and a small decrease of the density of the LTCC material occur.

scholarly journals Effect of the bur grit size on the flexural strength of a glass-ceramic

Cerâmica ◽  
2016 ◽  
Vol 62 (362) ◽  
pp. 121-127 ◽  
Author(s):  
P. P. Kist ◽  
I. L. Aurélio ◽  
M. Amaral ◽  
L. G. May
Keyword(s):  
Surface Roughness ◽  
Flexural Strength ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Internal Surface ◽  
Grit Size ◽  
Diamond Grit ◽  
Cad Cam ◽  
Negative Effect ◽  
Ceramic Blocks

Abstract The purpose of the present study was to determine the biaxial flexural strength (BFS) of a CAD/CAM leucite reinforced glass-ceramic ground by diamond burs of different grit sizes and the influence of surface roughness on the BFS. For this, 104 plates were obtained from CAD/CAM ceramic blocks and divided into 4 groups (n = 26), according to bur grit size: extra-fine, fine, medium and coarse. Roughness parameters (Ra, RyMax) were measured, and plates were kept dry for 7 days. The flexural test was carried out and BFS was calculated. Ra, RyMax and BFS data were subjected to analysis of variance and post-hoc test. Weibull analysis was used to compare characteristic strength and Weibull modulus. Regression analysis was performed for BFS vs. Ra and RyMax. When burs with coarse grit were used, higher surface roughness values were found, causing a negative effect on the ceramic BFS (117 MPa for extra-fine, and 83 MPa for coarse). Correlation (r) between surface roughness and BFS was 0.78 for RyMax and 0.73 for Ra. Increases in diamond grit size have a significant negative effect on the BFS of leucite-reinforced glass-ceramics, suggesting that grinding of sintered glass-ceramic should be performed using burs with the finest grit possible in order to minimize internal surface flaws and maximize flexural strength.

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