Calculation and Characterization of Silicon-Boron Phases in Metallurgical Grade Silicon

Introduction

It is a challenge that boron is removed in upgrading metallurgical grade silicon (MG-Si) to solar grade silicon (SoG-Si) with a metallurgical process. In this research, the Si-B binary system is thermodynamically assessed and characterized by using the CompuTherm Pandat software, which is helpful to the boron removal in refining MG-Si to SoG-Si.

Methods

The Si-B binary system was thermodynamically assessed and characterized by using the CompuTherm Pandat software. The SEM-EDS and XRD technologies were used.

Results

The solution phases, including Liquid, diamond-Si and ??-B were treated as substitutional solution phases, of which the Gibbs energies were expressed with Redlich?CKister polynomial functions. Meanwhile, the compounds, SiB₃, SiB₆, SiB_n, were modeled as stoichiometric compounds. The thermodynamic parameters formulating the Gibbs energies of various phases were obtained and the equilibria and transition of the phases were discussed. According to XRD technology, the intermediate phase SiB₄ was obtained and observed. It was tested that the phase SiB₄ existed objectively although it is not found in the assessed Si-B binary phase diagram.

Discussion

The existent forms for Si-B phases in the MG-Si melt were forecast and tested to be SiB₆ and Liquid.     

反应精馏法处理乙醇废水的工艺模拟

模拟了反应精馏处理乙醇废水的工艺,探讨了一些工艺参数呈现模拟所得趋势的原因,发现经过反应精馏处理后,产品流股中乙酸乙酯的质量分率仅比流股2提高了1%,随后分析了其原因。     

Sodium azide and metal chelator effects on 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from methylene blue photosensitized lard

Thermal oxidation of edible oils can generate 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from oxidized lipids (RSOLs). However, effects of photosensitization on the formation of RSOLs have not been reported yet. Methylene blue (MB) photosensitization and involvement of singlet oxygen and transition metals on the RSOL formations were determined in stripped lard oils. RSOLs were formed in lard containing MB and visible light irradiation only. Addition of sodium azide decreased RSOLs with concentration dependent manner, which implies singlet oxygen was involved on the RSOL formation. Ethylenediammetetraacetic acid (EDTA), a well known metal chelator, accelerated the formation of RSOLs through protecting the decomposition of MB photosensitizer. Results from p‐anisidine values showed that RSOLs from photosensitization may not be formed from the same pathways compared to thermal oxidation. Practical application: Understanding mechanisms of lipid oxidation can help extend the shelf‐life of foods. Photosensitization plays important roles in accelerating the rates of lipid oxidation. The results of this study showed that foods containing photosensitizers can generate radical scavenging compounds from oxidized lipids (RSOLs) under visible light irradiation and singlet oxygen is involved in the formations of these compounds. However, these compounds may not share the same pathways with thermally oxidized lipids. Metal chelating agents accelerated the rates of lipid oxidation and formation of RSOLs which implies that metal chelators can act as prooxidant. Careful considerations are necessary on the addition of metal chelators because non‐polar photosensitizers can act a prooxidant.     

Wavelength conversion using rare earth doped oxides in polyolefin based nanocomposite films

Nanocomposites are a new class of polymeric materials which include organic or inorganic nano‐phase materials. These nanocomposite films can show interesting properties which have many applications for wavelength conversion and energy saving. In this paper, we present polyolefin based nanocomposite films prepared using wavelength‐converting red ‘phosphors’ such as Y₂O₃: Eu³⁺ and LiAl₅O₈:Fe³⁺ and blue ‘phosphor’ CaMgSi₂O₆: Eu²⁺. The durability of the polymer chain is unaffected by incorporation of inorganic nanoparticles as there is no direct interaction between them. The addition of surfactant in the nanocomposite film helps to improve the dispersion ability of the nanoparticles and increase the flexibility of the polymer film. Wavelength‐converting ‘nanophosphors’ incorporated in a polymer matrix help to increase the tensile strength of the film. The films show excellent wavelength conversion ability of UV light into the visible and near IR range. These nanocomposite films have great application in energy saving devices. Copyright © 2012 Society of Chemical Industry     

Viscoelastic constitutive model for uniaxial time‐dependent ratcheting of polyetherimide polymer

Based on the experimental observations, a cyclic nonlinear viscoelastic constitutive model was proposed to describe the uniaxial time‐dependent ratcheting of polyetherimide (PEI) polymer under tension–compression and tension–tension cyclic loading. The model was constructed by extending the nonlinear viscoelastic Schapery model (Schapery, Polym. Eng. Sci., 9, 295 (1969)). The extension emphasized the changes of parameter functions used in the original model, which enabled the model to describe the ratcheting of polymer material. Comparing the simulations with corresponding experimental results, the capability of the extended model to predict the uniaxial time‐dependent ratcheting of PEI was verified. It is shown that the extended model can reasonably describe the uniaxial time‐dependent ratcheting of the polymer under the tension–compression and tension–tension cyclic loading with different peak‐holdings, stress rates, and stress levels. POLYM. ENG. SCI., 52:1874–1881, 2012. © 2012 Society of Plastics Engineers     

基于提标升级改造的CAST工艺优化研究

利用CAST反应器处理生活污水,通过改变曝气时间、进水过程中曝气频率、气流速度,对比各参数条件下的出水水质,研究各参数对污染物去除的影响,探索它们与污染物去除之间的相关性,研究结果表明,试验条件下CAST工艺的最优工况为:进水时间40 min,进水过程中每5 min曝气一次,曝气量1.2 m3/h,曝气3 h,出水COD、氨氮和总磷达GB 18918-2002一级A标。且体系中DO与ORP的变化与污染物的去除也存在一定的相关性,两者随时间变化的转折点能用于指示氨氮达标的时间点。     

硅和四氯化硅耦合加氢反应体系的热力学分析

基于Gibbs自由能最小原理,对硅和四氯化硅（SiCl₄,STC）耦合加氢反应体系进行了热力学分析。通过化学平衡产物组成分布的分析,确定了反应体系主要产物为三氯硅烷（HSiCl₃,TCS）、二氯硅烷（H₂SiCl₂,DCS）、盐酸（HCl）,并构造了3个相应的独立反应,讨论了对应的反应热（ΔrHθm）、自由能（ΔrGθm）和平衡常数（Kθp）与温度的关系。计算所采用的温度为673~923 K,压力为101.325 ~2 026.5 kPa,原料H₂与SiCl₄物质的量比为1~5。结果表明,生成TCS和DCS的反应为体系随着温度升高,四氯化硅平衡转化率及三氯硅烷产率降低;高压和适中的原料配比（H₂与SiCl₄物质的量比）有利于四氯化硅转化率及三氯硅烷产率的提高。     

Low-temperature synthesis of LiFePO<Subscript>4</Subscript> nanocrystals by solvothermal route

LiFePO₄ nanocrystals were synthesized at a very low temperature of 170°C using carbon nanoparticles by a solvothermal process in a polyol medium, namely diethylene glycol without any heat treatment as a post procedure. The powder X-ray diffraction pattern of the LiFePO₄ was indexed well to a pure orthorhombic system of olivine structure (space group: Pnma) with no undesirable impurities. The LiFePO₄ nanocrystals synthesized at low temperature exhibited mono-dispersed and carbon-mixed plate-type LiFePO₄ nanoparticles with average length, width, and thickness of approximately 100 to 300 nm, 100 to 200 nm, and 50 nm, respectively. It also appeared to reveal considerably enhanced electrochemical properties when compared to those of pristine LiFePO₄. These observed results clearly indicate the effect of carbon in improving the reactivity and synthesis of LiFePO₄ nanoparticles at a significantly lower temperature.     

Synthesis and characterization of integrated layered nanocomposites for lithium ion batteries

The series of Li[Ni _x M _x Li_1/3-x Mn_2/3-x ]O₂ cathodes, where M is cobalt or chromium with a wide compositional range x from 0 to 0.33, were prepared by hydroxide coprecipitation method with subsequent quenching. The sample structures were investigated using X-ray diffraction results which were indexed completely on the basis of a trigonal structure of space group with monoclinic C2/m phase as expected. The morphologies and electrochemical properties of the samples obtained were compared as the value of x and substituted transition metal. The particle sizes of cobalt-substituted Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ samples are much smaller than those of the Li[Ni _x Cr _x Li_1/3-x Mn_2/3-x ]O₂ system. The electrode containing Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ with x = 0.10 delivered a discharge capacity of above 200 mAh/g after 10 cycles due to the activation of Li₂MnO₃.     

Measurement and correlation of the isobaric vapor-liquid equilibrium for mixtures of alcohol+ketone systems at atmospheric pressure

Vapor-liquid equilibrium (VLE) for binary mixtures composed of ethanol+methyl isobutyl ketone, 1-butanol+ methyl ethyl ketone, and 1-butanol+methyl propyl ketone systems was measured using a circulation type equilibrium apparatus at atmospheric pressure. The measured data and literature data for alcohol and ketone systems have been correlated by the UNIversal Quasi-Chemical (UNIQUAC) model with two binary interaction parameters and the non-random lattice fluid equation of state with hydrogen bonding equation of state (NLF-HB EoS) using a single binary interaction parameter. For the NLF-HB EoS calculations, the numbers of proton acceptor for ketones were adjusted between 0 and 1. The calculation results with the NLF-HB EoS are better than those with the UNIQUAC model.