Specific heats and phase transition in TMMC

The specific heats of the nearly one-dimensional antiferromagnet TMMC showed a sharp discontinuity in the temperature range ?(≡∥1?T/T_N∥) ≈ 2 × 10^-3 at T_N =0.835 ± 0.010 K. The remaining magnetic entropy below T_N is about 1% of its total for S = $\text{5}\text{2}$.     

127I Mössbauer spectra of iodine adsorbed on zeolites

The adsorption behavior of iodine on zeolites and silver-loaded zeolites has been studied by¹²⁷I Mössbauer spectroscopy. Iodine is adsorbed on zeolites in two forms. One is a physically adsorbed species and the other is a dissociative species. The former is the major form and their intermolecular interactions are suggested to be weakened. Iodine is converted to silver iodide on the surface of silver-loaded zeolites, although some portion is physically adsorbed.     

Study of molecular motion of block copolymers in solution by high-resolution proton magnetic resonance

Molecular motions of hydrophobic–hydrophilic water-soluble block copolymers in solution were investigated by high-resolution proton magnetic resonance (NMR). Samples studied include block copolymers of polystyrene–poly(ethylene oxide), polybutadiene–poly(ethylene oxide), and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide). NMR measurements were carried out varying molecular weight, temperature, and solvent composition. For AB copolymers of polystyrene and poly(ethylene oxide), two peaks caused by the phenyl protons of low-molecular-weight (M?_n = 3,300) copolymer were clearly resolved in D₂O at 100°C, but the phenyl proton peaks of high-molecular-weight (M?_n = 13,500 and 36,000) copolymers were too broad to observe in the same solvent, even at 100°C. It is concluded that polystyrene blocks are more mobile in low-molecular-weight copolymer in water than in high-molecular-weight copolymer in the same solvent because the molecular weight of the polystyrene block of the low-molecular-weight copolymer is itself small. In the mixed solvent D₂O and deuterated tetrahydrofuran (THF-d₈), two peaks caused by the phenyl protons of the high-molecular-weight (M?_n = 36,000) copolymer were clearly resolved at 67°C. It is thought that the molecular motions of the polystyrene blocks are activated by the interaction between these blocks and THF in the mixed solvent.     

Zirconia based oxide ion conductors for solid oxide fuel cells

The electrical conductivity in the ZrO₂-Ln₂O₃ and ZrO₂-MO₂-Ln₂O₃(M = Hf, Ce, Ln = lanthanides) systems has been examined.The highest conductivity of 0.3 S/cm at 1000 °C was found in the ZrO₂-Sc₂O₃ system. The addition of MO₂ into the ZrO₂-Ln₂O₃(Ln = Sc, Y, Yb) systems showed the conductivity decreasing. The conduction mechanism in the zirconia based oxide ion conductors was discussed in view of the dopant ionic radius. The aging effect of the conductivity in the ZrO₂-Ln₂O₃ systems has been measured in a temperature rang 800–1000 °C. ZrO₂ with a high content of Ln₂O₃ showed no significant conductivity degradation. Paper presented at the 97th Xiangshan Science Conference on New Solid State Fuel Cells, Xiangshan, Beijing, China, June 14–17, 1998.     

Dielectric loss of polyethylene at very low temperatures in the frequency range from 1 kHz to 100 MHz

The dielectric loss of high-density polyethylene was measured from 1 kHz to 100 MHz with the improved calorimetric method at liquid-helium temperature for samples with different oxidation times t. Two loss peaks, centered at ca. 4 kHz and at 1 MHz, both increase in height with increasing t. On the bases of these results along with previously reported ones, the low-frequency and high-frequency losses are ascribed to the tunneling of protons of OH groups in crystalline and amorphous regions, respectively.