Structural, electrical and thermal properties of borosilicate glass–alumina composites (original) (raw)
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Journal of Materials Science: Materials in Electronics, 2009
Five samples of glass/ceramic composites were prepared from borosilicate glasses and both nano-aluminum oxide and nano-titanium oxide. The glass composite samples contain 10, 20, 30, 40, 50 wt.% of alumina and titania mixture. The ratio of Al 2 O 3 :TiO 2 in the mixture was 1:1. The formation of cristobalite in the glass matrix of low firing glass/ceramic composite substrates limits the efficiency of the ceramic substrate when it is used in circuit boards. In the present study, addition of both alumina and titania to a borosilicate glass as a ceramic filler caused the diffusion of alumina and titania phases (anatase and rutile) constituents into the glass matrix and prevented the formation of a cristobalite. Addition of both the ceramics suppresses cristobalite formation more effectively than one of them used alone and results in lower dielectric constant and thermal expansion coefficients.
Effect of cerium oxide addition on electrical and physical properties of alkali borosilicate glasses
Elesevier, 2010
The study of electrical conductivity, density and coefficient of thermal expansion (CTE) of Na 2 O:K 2 O:B 2 O 3 :SiO 2 :BaO glass samples with addition of cerium oxide has been carried out. It has been observed that the addition of cerium oxide affects the electrical conductivity, density and CTE. The results have been explained on the basis of the variation in number of bridging oxygens (BOs) and non-bridging oxygens (NBOs) present in the glass. In general, the glass with more NBOs has a weak network which exhibits higher electrical conductivity. The weakening of the network has been supported by the observed decrease in density and increase in CTE for the glasses.
Physica B: Condensed Matter, 2019
BaO-CaO-Al 2 O 3-SiO 2 (BCAS) glass and their derivatives have gained extreme importance for their high endurance to elevated temperatures and suitability for various electrochemical applications. Two glass systems, one being 50mol%[SiO 2-B 2 O 3 ]-xBaO-(45-x)CaO-5Al 2 O 3 with x= 0, 10, 20, 25, 30, 35 and 40 mol%, represented as BCBSA and another without Al 2 O 3 termed as BCBS, synthesized using melt quenching technique are considered here. The authors focus on the thermal and mechanical properties of these glasses. Reducing BaO concentrations improve the coefficient of thermal expansion (CTE/α) and other characteristic temperatures of glasses. Compacted glass pellets made of the water quenched frits show maximum shrinkage at 700 °C. Dilatometric analysis were conducted on compacts showing maximum shrinkage. CTE of these pellets are more than the bulk glasses. Glasses with low BaO concentrations exhibit high hardness and Young's modulus. Glasses bearing 20 mol% BaO, or even lesser, meet the thermal and mechanical properties required for high temperature sealants.
Influence of Al2O3 Addition on Structure and Mechanical Properties of Borosilicate Glasses
Frontiers in Materials, 2020
Alkali-borosilicate glasses are one of the most used types of glasses with a high technological importance. In order to optimize glasses for diverse applications, an understanding of the correlation between microscopic structure and macroscopic properties is of central interest in materials science. It has been found that the crack initiation in borosilicate glasses can be influenced by changes in network interconnectivity. In the NBS2 borosilicate glass system (74.0SiO 2-20.7B 2 O 3-4.3Na 2 O-1.0Al 2 O 3 in mol%) two subnetworks are present, i.e., a silicate and a borate network. Increasing cooling rates during processing were found to improve glasses crack resistance. Simultaneously, an increase in the network interconnectivity accompanied by an increasing capacity for densification were noticed. Their individual contribution to the mechanic response, however, remained unclear. In the present study the borosilicate glasses were systematically modified by addition of up to 4.0 mol% Al 2 O 3. Changes in the network connectivity as well as the short-and medium-range order were characterized using Raman and NMR spectroscopy. Both the Raman and the 11 B NMR results show that four-fold-coordinated boron is converted into threefold coordination as the Al 2 O 3 content increases. Additionally, 27 Al NMR experiments show that aluminum is dominantly present in four-fold coordination. Aluminum-tetrahedra are thus charge balanced by sodium ions and incorporated into the silicate network. Finally, nanoindentation testing was employed to link the inherent glass structure and its network configuration to the mechanical glass response. It was found that the glass softens with increasing Al 2 O 3 content, which enhances the crack resistance of the borosilicate glass.
Materials
With the rapid development of the microelectronics industry, many efforts have been made to improve glass-ceramics’ sinterability, thermal conductivity, and dielectric properties, which are essential components of electronic materials. In this study, low-alkali borosilicate glass-ceramics with PVA addition and glass-BN composites were prepared and successfully sintered at 770 °C. The phase composition, density, microstructure, thermal conductivity, and dielectric constant were investigated. It was shown that PVA addition contributes to the densification process of glass-ceramics (~88% relative density, with closed/open pores in the microstructure) and improves the thermal conductivity of glass material from 1.489 to 2.453 W/K.m. On the other hand, increasing BN addition improves microstructures by decreasing porosities and thus increasing relative densities. A glass-12 wt. % BN composite sample exhibited almost full densification after sintering and presented apparent and open pores...
Crystallization Kinematics and Dielectric Behavior of (Ba,Sr)TiO3 Borosilicate Glass Ceramics
Perovskite [(Ba 0.6 Sr 0.4 )TiO 3 ]-[2SiO 2 -B 2 O 3 ]-[K 2 O]-La 2 O 3 glass was prepared by conventional melt quench method. The differential thermal analysis (DTA) was performed on glass sample in the temperature range from 100˚C to 1000˚C by different heating rate to study the crystallization kinematics. The kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass samples were subjected to appropriate heat treatment schedules for their suitable crystallization. X-ray diffraction analysis (XRD) of glass and glass ceramic samples were done to check the amorphous state and crystalline nature. XRD of glass ceramic sample shows the major perovskite phase of BaTiO 3 (BT) along with the formation of secondary phases Ba 2 TiSi 2 O 8 (BTS) and Ba 2 Ti 2 B 2 O 9 (BTB). Scanning electron microscopy (SEM) is also studied to see the morphology of the grains of major and secondary phase formation in BST glass ceramic samples. La 2 O 3 is played an important role to increase the nucleation of the crystallites in the glassy matrix. The addition of La 2 O 3 results in development of well interconnected crystallites formed as major phase of BST. In this paper, we are reporting the crystallization behavior of BST borosilicate glass system and high temperature dielectric characteristics of their glass ceramics.
Egyptian Journal of Chemistry, 2021
Borosilicate glass recycling is a challenge because it has high melting point and different chemical structure which makes it non-recyclable in the glass industry. This work focuses on borosilicate recycling through the preparation of a low thermal expansion and chemically durable borosilicate glass-ceramic composite (BsGC). Low thermal expansion and high chemical durability ceramics are advantageous in many applications such as lab supplies, corning ware, automobile components, and other low expansion products that are resistant to thermal shock. Kaolin and borosilicate were chosen for the preparation of glass-ceramic composite, because they have low thermal expansion and good chemical durability. BsGC was prepared by sintering borosilicate glass waste (e.g., Pyrex laboratory glassware, household glass) and kaolin at different temperatures (750-900 ° C). Water absorption method was used to measure the apparent porosity of the prepared composites. Surface morphology of the prepared BCGs was investigated using scanning electron microscopy (SEM). Phase composition of the prepared BGC samples was characterized using X-ray diffraction technique (XRD). The XRD results showed that at sintering of 750 °C a monocrystalline quartz was only existing. By increasing sintering temperature up to 800°C the quartz phase decreased, while at 850 o C the quartz phase completely disappeared. The sintered BCG composites obtained exhibited low coefficients of thermal expansion in the range of 48 x 10-7 o C-1 and exhibited high chemical durability.