Short communication

The diffusion of copper, nickel and cobalt in silicon single crystals during irradiation with MeV protons, was studied under various experimental conditions. Under the irradiation normally used for charged-particle activation radiation enhanced diffusion negligible. The diffusion of radioisotopes caused by thermal effects however, lead to important errors. It is important to control the temperature of the irradiated samples.     

Use of solvent sorption to detect structural changes in rigid PVC compounds

The effects of type of PVC and its thermal history on solvent sorption behaviour were investigated. Samples were immersed in toluene at 25°C, and the equilibrium solvent uptake and sorption half-times were measured for a variety of samples. The shape of the sorption curve was also observed. Equilibrium sorption was found to decrease with increasing amount of crystallinity in the sample. Sorption half-time increased with increased crystallinity, but minimum equilibrium sorption did not correspond with maximum half-time, possibly due to the type of crystallinity present. The shape of the sorption curve (Fickian or Case II sorption) also depended on the ype of PVC used and is thermal history. The solvent sorption technique was shown to be a sensitive method for detecting small structural changes in PVC.     

Synthesis and characterization of polymerizable bisphthalonitrile monomers

The reactions of 4-aminophthalonitrile (APN) with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BPTDA), and with 1,2,3,4-benzenetetracarboxylic dianhydride (PMDA) have been studied to optimize the conditions for the synthesis of monomeric thermosetting bisphthalonitrile compound. Suitable procedures for the synthesis of the two monomers are presented. Elemental analyses, IR spectra, dynamic thermogravimetric analyses, differential scanning calorimetry, ¹H-NMR, and mass spectral studies have been used to characterize these compounds. Preliminary observations show that these materials can be polymerized to give high-temperature-resistant materials.     

Brillouin scattering and rotation translation coupling of (KCN)xX1−x mixed crystals

Brillouin scattering is used to study the concentration and temperature dependence of longitudinal and transverse phonon frequencies of KCN_χBr_1?χ, KCN_χC1_1?χ, and KCN_0.85I_0.15 mixed crystals. Unlike pure KCN, mixed crystals with χ < 0.7 show no phase transition upon cooling, and the transverse acoustic frequency ω_TA(110) displays a minimum at some characteristic temperature T_i.T_i is below the phase transition of pure KCN and depends on the C1^? concentration. The Brillouin data are discussed in terms of coupling of the acoustic phonons with orientational motion of CN^? ions and mean field theory.