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The influence of BaO content (up to 15 mol%) on the crystallization behaviour, structure, thermal properties and microwave dielectric properties of the BaO-CaO-B 2 O 3 -SiO 2 glasses and glass-ceramics system was investigated. The glasses were produced by melting at 1400 °C and quenching into water, and the glass-ceramics were produced via heat treatment at temperatures between 750 and 800 °C. The results of X-ray diffraction analysis showed that increasing the BaO content raised the resistance of the glass against crystallization and favoured the transformation of β-CaSiO 3 and α-CaSiO 3 phases, which crystallized in the Ba-free and in low BaO content compositions, into SiO 2 and Ba 4 Si 6 O 16 , which crystallized in compositions with higher concentrations of BaO. The BaO content had little influence on the glass transition temperature ( T g ) and the linear coefficient of thermal expansion (CTE), but strongly reduced the softening point ( T s ). Even the addition of BaO as minor additives resulted in a dramatic reduction of the T s ; for example, the T s decreased from 902 °C for the Ba-free composition to 682 °C for the BaO-containing one (5%). Low values of the dielectric constant (5.9 ≤  ε r ≤ 6.63) and dielectric loss (1.12 × 10 −3 ≤ tan δ  ≤ 3.15 × 10 −3 ) were measured. [ABSTRACT FROM AUTHOR]

This paper presents that polyethylene glycol (PEG) synthesizes a form-stable phase change material (FS-PCM) with high thermal conductivity and considerable heat storage density. PEG was confined to the chain structure of epoxy resin (EP) via high-temperature melt blending and curing, which solves the leakage problem of PCMs during phase transformation. In order to increase the thermal conductivity and stability of the PEG/EP while maintaining good heat storage capacity and insulation ability, a low loading of reticulated porous Al 2 O 3 ceramic (RPC) was introduced into the PEG/EP matrix. RPC increases the thermal conductivity of FS-PCM by 5.5 times and the heat storage rate by 4 times. In addition, FS-PCM filled with 13.8 vol% RPCs has a coefficient of thermal expansion (CTE) of 80 ppm/K at 85–150 °C -a decrease of 62% over the matrix. Furthermore, the BN network is formed on RPC by vacuum impregnation technology, which further improves the thermal conductivity. This novel FS-PCM has excellent comprehensive properties and does not need for case package, indicating great prospects in thermal management and thermal storage. [ABSTRACT FROM AUTHOR]

Dense AlN ceramics with a thermal conductivity of 180W/m·K were obtained at the sintering temperature of 1750 °C using CaF2 and YF3 as additives. At temperatures below 1650 °C, the shrinkage of AlN ceramics is promoted by liquid (Ca,Y)F2 and Ca12Al14O32F2. Liquid CaYAlO4 mainly improves the densification of the sample when the sintering temperature increases to 1750 °C. The formation of liquid (Ca,Y)F2 at a relatively low temperature results in homogeneous YF3 distribution around the AlN particles, which benefits the removal of oxygen impurity in the AlN lattice, and thus a higher thermal conductivity. [Copyright &y& Elsevier]