Morphological and kinetics study of PEO/PVC blends

The kinetics of spherulite radial growth and the morphology of the compatible system PEO/PVC have been studied by optical microscopy. The usual spherulite radial growth behaviour has been found for compatible blends with PEO content higher than 70%. For lower composition, distortion of the usual spherulite morphology has been observed; the anomalies have been attributed to partial miscibility of the components.     

Studies on the synthesis of SAPO-5

Silicoaluminophosphate (SAPO-5) molecular sieves have been synthesised from reaction mixtures having a molar composition of: 0.7–1.0 Al₂O₃:0.7–1.0 P₂O₅:0.01–2.0 SiO₂:xR:40 H₂O (where R = (C₂H₃)₃N or (C₂H₃)₄NOH and x = 1.5–2.5 for (C₂H₅)⁵N and 0.5 for (C₂H₅)₄NOH, at 473 K using various sources of alumina and silica. The effects of (i) varying the crystallinity of the alumina source (boehmite) and (ii) the use of different silica sources such as freshly prepared silica either from sodium silicate or paddy husk extract, silica gel from commercial water-glass, and tetraethyl orthosilicate have been studied. The crystallinity of boehmite has been found to have a strong effect on its reactivity towards the formation of SAPO-5. The activity of boehmite for SAPO-5 formation increased with a decrease in its crystallinity (or with increase in its moisture content). Any silica source devoid of sodium ions could be employed for the synthesis of SAPO-5. The process of crystallisation started as early as within 1.5 h of reaction and incorporation of silicon into the AlPO₄ framework has been noted at this stage. Formation of some tridymite phase as impurity has been observed under conditions such as (i) SiO₂ concentration > 1.7 mole and (ii) x > 2.0 when R = (C²H₅)₃N.     

Kinetics of methane hydrate formation in aqueous electrolyte solutions

Experimental data on the kinetics of methane hydrate formation in aqueous electrolyte solutions are reported. The experiments were carried out in a semi-batch stirred tank reactor in three NaCl and two KCl solutions as well as in a solution containing a mixture of NaCl and KCl at three different nominal temperatures from 270 to 274 K and at pressures ranging from 3.78 to 7.08 MPa. The kinetic model developed by Englezos et al. (1987a) was adapted to predict the growth of hydrates. The model is based on the crystallisation theory coupled with the two-film theory for gas absorption in the liquid phase. The kinetic rate constant which appears in the model was that obtained earlier for methane hydrate formation in pure water. The effect of the electrolytes was taken into account through the computation of the three-phase equilibrium conditions and the corresponding fugacities. Overall, the model predictions match the experimental data very well with the largest prediction error being less than 10%.     

非晶态Ni-W-P镀层退火晶化和激光晶化组织结构的演变

用XRD定量分析法并结合扫描电镜形貌观察,研究化学沉积高磷(13.3%)含量的Ni-W-P镀层在不同热处理条件下的晶化程度、晶粒尺寸及晶格应变等组织结构的演变规律。结果表明:高磷非晶态镀层在退火晶化过程中,Ni3P相的体积分数始终高于Ni相的,700℃时,两相的体积分数之差显著增大,镀层仍有残存的非晶相;在400~500℃之间形成的Ni3P的晶粒尺寸大于Ni的;温度为500~700℃时,Ni相的尺寸大于Ni3P的,但均未超过纳米级。镀层晶格应变表现为随退火温度的升高而降低,镀态时晶格应变最大。激光晶化处理的非晶态Ni-W-P镀层的显微结构特征介于400~500℃之间退火的镀层晶化特征。随扫描速度增加,不仅Ni3P晶粒尺寸增大,而且两相的尺寸差变大。     

Effect of Ce,Sb and Sn on mechanism and activation energy for crystallisation of X‐ray irradiated photosensitive glass

Abstract

Abstract

This work aims to determine the effect of Ce, Sb, Sn and Ag on the mechanism and activation energy of crystallisation for an X‐ray irradiated photosensitive lithium silicate glass composition and to compare it with the one that contained only Ag. According to the obtained results, while the addition of Ce, Sb and Sn changed the crystallisation mechanism of lithium silicate crystal from two‐ to three‐dimensional growths, these additions did not affect the activation energy of crystallisation for lithium metasilicate. Differential thermal analysis was used for studying the mechanism and activation energy for crystallisation of these glasses through the Matusita and the modified Kissinger methods; SEM and XRD were used to investigate the lithium silicate and silver crystallisation in the glasses.     

Using an additive to control the electrospinning of fibres of poly(ε‐caprolactone)

Electrospinning is a route to polymer fibres with diameters considerably smaller than available from most fibre‐producing techniques. We explore the use of a low molecular weight compound as an effective control additive during the electrospinning of poly(ε‐caprolactone). This approach extends the control variables for the electrospinning of nanoscale fibres from the more usual ones such as the polymer molecular weight, solvent and concentration. We show that through the use of dual solvent systems, we can alter the impact of the additive on the electrospinning process so that finer as well as thicker fibres can be prepared under otherwise identical conditions. As well as the size of the fibres and the number of beads, the use of the additive allows us to alter the level of crystallinity as well as the level of preferred orientation of the poly(ε‐caprolactone) crystals. This approach, involving the use of a dual solvent and a low molar mass compound, offers considerable potential for application to other polymer systems. Copyright © 2010 Society of Chemical Industry     

Food applications of trans fatty acid substitutes

The review outlines the increasing need to reduce trans fatty acids, and addresses the functionality issues of various trans free solutions through discussion of hydrogenation, interesterification, and fractionation, and their influence on fat crystallisation and solid fat content. Caution is urged not to focus solely on physio‐chemical aspects, but to approach trans free designing for specific food applications from a multidisciplinary angle. Examples of specific applications; margarines, shortenings and frying oils are given. The review also offers a glimpse into what the future trans free trends may hold.     

超声波辅助马铃薯冻结的实验研究

为了研究超声波辅助沉浸冻结的机理,将马铃薯样品分别浸入脱气冷冻液与未脱气冷冻液中冷却。每次实验时,从?1℃时开始,启动超声波发生装置,使马铃薯内的水分在超声场中冻结。利用扫描电镜比较分析不同实验条件下马铃薯组织的微观结构,实验结果表明不同冷冻液中的马铃薯样品遭受超声波辐射后,其组织在冻结过程中受到的损伤均小于无超声波作用的样品,而且超声波对浸于未脱气冷冻液中样品组织的改善作用更为显著。表明超声波诱发的冷冻液的分子振动与空化均对沉浸冻结有影响。     

重轨坯滴状偏析成因研究

通过对重轨钢初轧坯结晶组织形状的观察，分析了滴状偏析的成因，结果表明：滴状偏析的形成，是因为浇注温度低，过于粘稠，使富集溶质元素的偏析液不能充分上浮所致。