Anomalous phase transition behavior of carbon tetrachloride in silica pores

The size-dependent phase transition behavior of carbon tetrachloride confined in silica pores (rp = 5–50 nm) has been investigated by DSC and X-ray measurements. The melting point of CCl4 in the pores linearly decreased with the reciprocal pore size. The solid-to-solid transition temperature of CCl4 in the pores also depended on pore size. Below the pore radius of 16.5 nm, the process of phase transition of CCl4 on cooling was different from that of bulk CCl4. The decrease in the heats of the transitions in the pores suggested the existence of non-transforming phase in the pores. The geometric restriction of small pore contributes to the anomalous transition behavior of CCl4 in the pores.