Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.     

Synthesis and Stereochemistry of New Bis(1,3-Oxathian-2-yl) Derivatives: Epimerisation and Chair–Twist Equilibria

The synthesis and stereochemistry of some new bis(1,3-oxathian-2-yl) derivatives are reported. The conformational behavior of these compounds and the orientation of their substituents are deduced from the NMR spectra, from the X-ray crystal structures of two compounds and from the ab-initio level calculations. The epimerization of diastereoisomers and the chair ⇌ 22,5-twist equilibria were studied by variable temperature NMR.     

Effect of Oxygen Redistribution on the Normal and Superconducting Properties of Yttrium High‐Temperature Superconductors

An anomaly is found in the vicinity of T_max 560$ K on electric resistance versus temperature curves for yttrium hightemperature superconductors of the 123 phase. Xray phase analysis suggests a structural phase transition in the vicinity of T_max due to oxygen redistribution in the mobile sublattice of this compound. Investigation of samples with Y partially replaced by Ca has shown that the structural phase transition does not depend on carrier concentration in the conduction band.     

Forms of vibrations and structural changes in liquid state

Summary The forms of vibrations and displacements of particles in amorphous structures have been investigated. The particles, moving on highly non-linear amplitude, are responsible for the creation of disordered structures of amorphous bodies. The non-linear oscillators, even if 'few' in concentration, are characterized by unpredictable trajectories in phase space. The non-linear oscillators are fully developed in the liquid state above the crossover temperature T_cr and between T_cr and T_g their number decreases. Under T_g they completely disappear. The interconnection between the linear oscillators in blocks plays the most important role in the characteristic time spectra in liquid state. Using the additive properties of elements polarizibilities, the number of acoustical units in individual blocks at T_cr is estimated to be about 600 units. The diameter of blocks at T_cr was estimated to be about 1.8 nm. Even if the non-linear high amplitude motions disappear at solidification, the remnants of structural irregularity remain and the disordered structure of glass is formed.     

Influence of velocity and surface temperature of alumina particles on the properties of plasma sprayed coatings

In this paper are described the main characteristics of the plasma spraying process of alumina deposits, i.e., the temperature and flow field of the plasma jets obtained with the classical spraying torches, the injection of the particles into the plasma jet, the particle surface temperature and velocities in the plasma (measured for calibrated alumina particles), and the coating generation. The measurements on the alumina particles are compared with the predictions of a mathematical model. The experimental and computed particle velocities are in rather good agreement. However, this is not the case for the particle surface temperature. Possible reasons for the discrepancy are proposed (influence of the carrier gas, thermophoretic forces, and poor penetration of the particles into the plasma core even for an injection velocity twice that of the optimal calculated one, as shown by recent measurements). Finally the correlations between the particle velocities and surface temperature, and the properties of the alumina coating (porosity, crystal structure, mechanical properties) are studied.     

Low-temperature synthesis of allyl dimethylamine by selective heating under microwave irradiation used for water treatment

Low-temperature synthesis of allyl dimethylamine (ADA) by selective heating under microwave irradiation (MI) used for water treatment is investigated. The effect of MI, ultrasound irradiation (UI) and conventional heating on yield of ADA, reaction time and the flocculation efficiency of polydiallyl dimethylammunion chloride (PDADMAC) prepared form ADA were studied. The results show that by selective heating at low temperature, MI not only increases yield of ADA and reduces reaction time, but also greatly enhances the flocculation efficiency of PDADMAC.     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

含间苯基聚芳醚酮的合成与性能研究

含间苯基聚芳醚酮的合成与性能研究林权，张万金，吴忠文，尹玖梅（吉林大学化学系，长春，１３００２１）（中国科学院长春应用化学研究所）关键词聚芳醚酮，间苯基，熔点，结晶度聚芳醚酮作为一类耐高温特种工程塑料，由于具有优异的热、电、机械性能，已被广泛应用于电...     

Growth transition and morphology change in polypropylene

The growth rate of isotactic polypropylene is deduced from microscopic observations during isothermal crystallizations. A change in the growth regime is observed at 138 C and interpreted as a Regime III Regime II transition, according to Hoffman's kinetic theory of polymer crystallization. A Regime II Regime I transition is also theoretically predicted at 155 C, i. e. at a temperature outside the investigated temperature range. The Regime III Regime II transition is related to the positive to negative change in the spherulite birefringence, which is generally attributed to a change in the organization of crystalline lamellae: quadritic arrays of intercrossing lamellae atT _c < 138 C (Regime III) and preferentially radiating lamellae atT _c > 138 C (Regime II). It is suggested that such a morphological change could be interpreted using the concept of non-adjacent re-entry introduced in Hoffman's kinetic theory. This interpretation could also explain the interspherulitic ruptures observed in negative spherulites.     

乙醇在杂多酸上的氧化、脱水和程序升温脱附研究

合成了两个系列具有Keggin结构的12-钒钼磷酸和钨钼磷酸,研究了它们对乙醇氧化、脱水的催化反应。借助程序升温脱附技术研究了反应物及产物乙醇、乙烯、乙醚等在样品上的程脱作用。讨论了钨、钒取代部分钼原于后对杂多酸酸性及氧化性能的影响。