A mass spectrometric study of the vaporization of boron phosphate (BPO(4))

The vaporization behavior of boron phosphate has been studied by using Knudsen effusion mass spectrometry. The vapor over BPO(4) consists of B(2)O(3), P(4)O(10), PO(2), BPO(4) (platinum cell) and B(2)O(3), PO, PO(2), BPO(3), BPO(4) (molybdenum cell). Standard enthalpies of formation and atomization (kJ/mol) were derived for BPO(4) (g) (-1000 +/- 15 and 2863 +/- 16) and for BPO(3) (g) (-731 +/- 15 and 2347 +/- 16), respectively. Copyright 1999 John Wiley & Sons, Ltd.     

Microwave heating of ceramic composites

The microwave heating of a ceramic composite is modelled andanalysed. The composite consists of many small ceramic particlesembedded in a ceramic cement. The composite is assumed to bewell insulated, and each particle is assumed to be in imperfectthermal contact with the surrounding cement. Based on thesetwo assumptions an asymptotic theory exploiting the small Biotnumber and small non-dimensional contact conductance is developed.Our asymptotic theory yields a set of nonlinear partial differentialequations which govern the temperature in the composite. Theseare reduced to a set of coupled nonlinear ordinary differentialequations in which the surface area of each particle entersas a parameter. Recent experiments with such composites haveshown that the steady-state temperature of the composite isstrongly dependent upon the radii of the embedded particles.Our model captures this effect. In fact, our analysis showsthat the assumption of imperfect thermal contact between theparticles and the ceramic cement is essential for this trendto be established.     

在接枝微粒PS/SiO2上固载季铵盐及初步应用

采用"grafting from"的方式在溶液聚合体系中将苯乙烯(St)接枝聚合在微米级硅胶表面,制备了接枝微粒PS/SiO2;使用新型氯甲基化试剂1,4-二氯甲氧基丁烷,对接枝的聚苯乙烯进行了氯甲基化反应,制得了接枝有氯甲基聚苯乙烯(CMPS)的接枝微粒CMPS/SiO2;使用叔胺试剂对CMPS大分子链上的苄氯基团实施了季铵化反应,最终制得了固载有季铵盐(Quaternary salt)的复合型功能微粒QPS/SiO2.用红外光谱(FTIR)与化学分析法对功能微粒QPS/SiO2的化学结构与组成进行了表征;研究了各种因素对CMPS/SiO2季铵化反应的影响规律;初步考察了QPS/SiO2对大肠杆菌的(E.coil)抗菌性能.研究结果表明,接枝微粒CMPS/SiO2的季铵化反应比较容易进行;溶剂性质、叔胺试剂的种类及温度对CMPS/SiO2的季铵化反应均有影响.使用CMPS的良溶剂和用位阻小的叔胺试剂,所得产物的季铵化度均较高.QPS/SiO2具有很强的抗菌活性.使用很小的剂量(10 g/L)、在很短的接触时间内(3 min)抗菌率即可达100%,是一种优良的水不溶抗菌材料;QPS/SiO2的季铵化度越高,其抗菌活性越高;使用碳氢链较长的三丁胺制备的QPS/SiO2,其抗菌性能明显优于使用三乙胺制备的QPS/SiO2.     

Optical colours and polarization of a model reflection nebula

Simple models of a reflection nebula in the form of a plane-parallel slab containing smooth spherical solid particles in submicron size range have been considered. Single scattering has been assumed. The effect of varying the composition and size distribution function of the grains have been brought out in the calculations using Mie theory of scattering. The analytical part of the geometry of the problem has been treated quite rigorously and the resulting expression for nebular intensity has been presented in a somewhat new form. In this paper, the case of the star behind the nebula has been examined. A comparison of the theoretical results with the observations of the Merope nebula shows that the dirty ice grains with index of refraction about 1·3–0·1i and size parametera ₀ = 0·5μ give reasonable agreement with the colours. Simultaneously, the polarization in the visual and blue wavelength bands agree approximately up to offset angle of 6 minutes of arc. The larger offset angles pose an intriguing problem. The general trends of nebular colours and polarization with variation of real and imaginary parts of index of refraction and the size distribution parameter have been tabulated to serve as a guide for further study of reflection nebulae with the star in the rear. A part of this work was presented at the first scientific meeting of the Astronomical Society of India, held on 27 and 28 February 1974 at Hyderabad. An erratum to this article is available at .     

Ca0．80Zn0．20Te晶体的生长及性能研究

用本实验室合成的Ca0．80Zn0．20Te多晶料为原料，采用改进的布里奇曼法在镀碳和未镀碳的石英安瓿中生长出Ca0．80Zn0．20Te晶锭。使用X射线衍射仪对合成产物及晶锭进行了分析，生长晶体的X射线衍射峰尖锐，摇摆谱对称，表明晶锭的结晶性能较好；用IRPrestige-21红外光谱仪分析了晶体的红外透射光谱，测试结果表明安瓿镀碳后生长的晶体位错密度小，均匀性较好，电阻率优于未镀碳安瓿生长的晶体；晶体的蚀坑密度在10^3-10^4cm^-2之间，比未镀碳安瓿生长的晶体低1个数量级。     

Surface structure of protonated R-sapphire (1102) studied by sum-frequency vibrational spectroscopy

Sum-frequency vibrational spectroscopy was used to study the protonated R-plane (1102) sapphire surface. The OH stretch vibrational spectra show that the surface is terminated with three hydroxyl moieties, two from AlOH(2) and one from Al(2)OH functional groups. The observed polarization dependence allows determination of the orientations of the three OH species. The results suggest that the protonated sapphire (1102) surface differs from an ideal stoichiometric termination in a manner consistent with previous X-ray surface diffraction (crystal truncation rod) studies. However, in order to best explain the observed hydrogen-bonding arrangement, surface oxygen spacing determined from the X-ray diffraction study requires modification.