One of the negative emission technologies is DAC (direct air capture), which captures low concentrations of carbon dioxide from the air. This study is a basic research on DAC technology and investigates various conditions for the formation of calcium carbonate by stirring a calcium hydroxide suspension. The calcium hydroxide suspension was agitated with a stirrer at 200–400 rpm and samples were taken at predetermined time intervals. Samples were taken at predetermined time intervals. The samples were characterized by X-ray diffraction, thermal analysis (TG-DTA) and SEM.

　When the calcium hydroxide suspension was stirred and carbonated, calcite was initially formed, but later needle-like aragonite was formed. The maximum aragonite fraction was 81%. The formation of calcium carbonate was accelerated with increasing agitation rate, and the grain size of aragonite became smaller. The volume of air contact was 42.8 L・h^－1 at a stirring rate of 300 rpm. The air contact volume reached a maximum of 54.1 L・h^－1 at the suspension concentration of 4 mass%. When the reaction vessel was increased to 5 liters, the volume of air contact increased to 179.3 L・h^－1.

　The effects of the addition of BaTiO₃ (BT) and β–Si₃N₄ (SN) on the thermal conductivity and dielectric properties of polyvinylidene fluoride (PVDF) were investigated. The formation of BT aggregates promoted the formation of a BT/PVDF/BT anisotype (N/P/N) heterointerface, improved the dielectric properties due to the junction barrier, and promoted the α–β phase transition of PVDF. On the other hand, the formation of SN aggregates promoted the construction of SN/PVDF isotype (P/P) heterointerface and particle group network, which improved the thermal conductivity. Additionally, the BT/PVDF interface did not inhibit thermal conduction, and the SN/PVDF interface did not adversely affect the dielectric properties. From the above results, it has become clear that composite material properties are strongly influenced by the aggregation and connection state of particle groups.