Energy storage technology is crucial for a sustainable society, and its realisation strongly depends on the development of materials. Oxide glass exhibits high durability. Moreover, the amorphous structure of the glass without periodic ordering demonstrates excellent formability and controllability, thus enabling a large-scale production. These factors provide impetus for the development of new materials for thermal management applications. As vanadium dioxide (VO2) with a strongly correlated electron system exhibits a structural phase transition, leading to a large heat of transition. Therefore, VO2 demonstrates immense potential as a phase change material (PCM). This study reports the fabrication of VO2-dispersed glass and examines its potential as a new latent heat storage material, which can be applied for massive PCM heat storage applications.

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Phase change material (PCM), which enables heat storage based on phase transition, plays an important role for efficient energy utilization. This paper briefly describes our recent study about all-solid PCM by combination of vanadium dioxide (VO 2 ) with latent heat storage capacity and multicomponent glass, i.e., VO 2 -dispersed glass. A B 2 O 3 -P 2 O 5 -V 2 O 5 glass system is used as a matrix for the VO 2 -dispersed glass. An attempt to describe its latent heat storage function is given. Endothermic behavior due to structural phase transition of the VO 2 crystals was observed in the VO 2 -dispersed sample, and the transition enthalpy corresponding to latent heat storage capacity was estimated to be H∼9.5 J/g. The value of the studied sample was larger than the value of dispersed glass in the BaO-TeO 2 -V 2 O 5 system that was previously reported. Potential for PCM was considered in the studied sample.

In order to fabricate an alumina ceramics with high density at low sintering temperature, nanosized γ–Al2O3 powders with average size of 9.7 nm were added to microsized γ–Al2O3 powders with 2 #m and they were well mixed. Its sintering behavior was studied in the temperature range of 1000oC to 1300oC and in holding time from 1 hour to 10 hours. Compacted samples with a different mixed ratio of nanosized and microsized Al2O3 powders (N/M ratio) were prepared and pressured at 1 GPa in a uniaxial direction. The phase transformation from γ–Al2O3 to α–Al2O3 takes place at 1100oC for 1hour sintering in all compacted samples. This rate is increased with increasing N/M ratio. The relative density varied from 70% to 95% depending on temperature and N/M ratio. With increasing sintering temperature from 1000oC to 1300oC, it was changed from 70% to 93%. Especially, the relative density was enhanced about 9% higher than that of only microsized sample by only 10 wt% addition of nanosized powders.

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