用低温固相反应制备p型Mg2Si基热电材料

用Mg粉和Si粉通过固相反应在823 K时保温8 h合成了Mg2Si粉末;并通过外加Ag粉用二次固相反应在相同条件下合成了Mg2Si基热电固溶体.采用放电等离子烧结法(SPS),以掺杂Ag后的固溶体为原料制备出了p型Mg2Si基热电材料.研究了Ag掺杂量对Mg2Si材料热电性能的影响.结果表明随着掺杂Ag的摩尔分数的增大,材料的Seebeck系数(即温差电动势)和电导率均有增大的趋势,但热导率变化不大.温度为513 K时,掺杂Ag的摩尔分数为15×10-3的试样的优值系数Z值和优值系数与温度之积ZT均为最大,分别为18.2×10-6 /K和0.01.     

硅化镁热电材料的放电等离子反应烧结

硅化镁(Mg2Si)是一种窄带隙n-型半导体,具有高的电导率和低的热导率且无毒无污染、耐腐蚀,是很有潜力的环境友好型中温域热电材料.实验用高纯镁(Mg)粉和硅(Si)粉,系统研究了放电等离子烧结制备Mg2Si热电材料的工艺过程.测试了样品的密度.用X射线衍射、场发射扫描电镜表征了样品的相组成和显微结构.结果表明:Mg,Si完全固相反应的温度为823K,适度过量的Mg含量对纯相Mg2Si的获得非常重要.823K,250MPa,30min条件下制各样品的相对密度达到97%,但样品表面容易产生裂纹.经823K,6MPa,10min完全反应的Mg2Si在1 023 K,20 MPa,10 min条件下进行二次烧结,获得了结构均匀、相对密度为98T的Mg2Si块体热电材料.     

Mg2Si基热电材料的制备与掺杂研究现状

热电材料是一种性能优越的环境友好型材料,它能够直接把电能和热能相互转化,是目前新技术能源材料领域的关键材料.Mg2Si基半导体是一种新型的中温区热电材料,具有热电值高,原料无毒害等优点,由于镁的活性较高,如何制备出性能更加优良的Mg2Si基块体热电材料成为本领域研究的重点.本文简要介绍了Mg2Si基热电材料的基本性质,阐述其各种制备方法和掺杂研究现状,并展望其未来研究方向.     

碲化铋基热电材料复合改性的研究进展

近年来Bi2Te3基热电材料被广泛用于医疗器械、电子、航空航天等各种商业领域,材料的性能已经逐步得到提高.目前已有大量关于通过掺杂、纳米化或与其他材料复合来提高碲化铋基热电材料热电性能的报道,而材料复合是其中一种重要的优化手段.本文重点对碲化铋同有机与无机材料的复合改性进行了介绍,总结了复合不同类型的物质对材料热电性能的影响,对比了不同方法下所制备的复合材料的热电参数,并对Bi2Te3基热电材料复合改性的未来发展进行了展望.     

碲化铋基热电材料复合改性的研究进展

近年来Bi2Te3基热电材料被广泛用于医疗器械、电子、航空航天等各种商业领域,材料的性能已经逐步得到提高.目前已有大量关于通过掺杂、纳米化或与其他材料复合来提高碲化铋基热电材料热电性能的报道,而材料复合是其中一种重要的优化手段.本文重点对碲化铋同有机与无机材料的复合改性进行了介绍,总结了复合不同类型的物质对材料热电性能的影响,对比了不同方法下所制备的复合材料的热电参数,并对Bi2Te3基热电材料复合改性的未来发展进行了展望.     

铋掺杂硅化镁材料的制备及热电性能

采用放电等离子体烧结方法制备不同含量铋（Bi）（0、0.7％、1.0％、1．5％、2．0％,摩尔分数,下同）掺杂硅化镁（Mg2Si）热电材料,对材料进行物相、结构及热电性能分析。结果表明：Bi在Mg2Si中最佳掺量为1．5％,继续增加会有Mg2Bi3杂相生成;随着Bi掺量的增加,材料电导率δ不断增加,当Bi掺量为1．5...     

通过In/Sb双掺杂优化SnTe基材料热电性能

采用高温熔炼、热压烧结方法制备了p型Sn Te基热电材料Sn_(0.995–x)In0.005Sb_xTe(x=0～0.16)并研究了其热电性能。In掺杂可以在SnTe中引入共振能级,态密度增加,使得室温Seebeck系数提升。此外,因为与Sn所带电荷不同,Sb的异价掺杂会产生大量自由电子,从而降低Sn Te基材料过高的载流子浓度;而纳米尺度富Sb第二相散射也会让晶格热导率进一步降低,在825 K时获得最低晶格热导率约0.73 W/(m?K)。通过电学和热学的协同优化,整个温度区间的zT值都得到提升。其中,Sn0.915In0.005Sb0.08Te在825 K时获得zT最大值约1.1,说明该体系Sn Te基材料在热电应用上有一定潜力。     

BiCuTeO的高压合成与电输运性能研究

四元层状化合物BiCuTeO具有极低的热导率和很好的热电性能，但多数文献报道的结果表明该类材料的制备较为困难，单相化合物不易合成。通过吉布斯自由能计算发现利用CuO替代Bi₂O₃和单质Cu作为Cu源和O源有利于BiCuTeO的合成，并利用一步高压合成方法快速制备了BiCuTeO。为了优化BiCuTeO的电输运性能，还分别利用Se和Pb对其Te位和Bi位进行了掺杂研究，结果表明：Se在Te位掺杂能够提高BiCuTeO的载流子有效质量进而提高Seebeck系数，但霍尔迁移率降低和带隙增大导致电阻率升高、功率因子降低；Pb掺杂可以同时提高BiCuTeO的载流子有效质量和载流子浓度，因而有利于提升电输运性能。     

稀土镧对DMSO有机溶剂体系电沉积铋−碲热电薄膜的影响

在二甲基亚砜(DMSO)有机溶剂中先通过阴极极化曲线和循环伏安曲线测试研究了Bi(Ⅲ)、Te(Ⅳ)离子在镍电极上电沉积的电化学行为.再在不同电位下电沉积制备了Bi–Te热电薄膜,研究了沉积电位和稀土La对Bi–Te薄膜性能的影响.结果表明,Bi–Te热电薄膜的电沉积属于正则共沉积,不同电位下所得Bi–Te薄膜均含有Bi2Te3化合物和单质Te.La的加入可以显著改善薄膜的微观形貌,影响薄膜中各组分的含量,但对薄膜的物相结构无明显影响.     

Bi2Te3基P型赝三元热电材料的热压制备及性能

采用熔炼-粉碎法制备了P型Bi2Te3基赝三元热电合金粉体,粉体经筛分后,用热压法制备了(Sb2Te3)0.75(1-x)(Bi2Te3)0.25(1-x)(Sb2Se3)x样品.通过X射线衍射和扫描电镜对样品进行表征.结果表明:在热压烧结样品中,出现了晶粒的(0001)面垂直于压力方向的明显取向,垂直于压力方向是热压样品的高热电优值方向.在一定的热压压力下,样品的电导率和温差电动势率都随温度的增加而增大.在一定的热压温度下,随着压力的增加,样品的电导率增加,而温差电动势率变化不大.最好样品的热电优值达到2.78×10-3/K.     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。     

典型煤碳燃烧特性研究和数值模拟

本文以三种典型煤的碳燃烧为研究对象，分别采用简单一维沉降燃烧方式和等温加热燃烧方式，实验研究了煤在快速加热条件下，其碳的初期和中，后期燃烧过程。以实验为基础，建立了煤的碳燃烧模型，变工况数值模拟了煤的碳燃烧过程，揭示了煤不同条件下的单颗粒碳燃烧特性。     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

卫生陶瓷烧成用窑炉发展之我见

归纳了当今卫生陶瓷工业的发展现状和水平 ,对窑炉产业提出了的新要求 ,分析了某一新型窑炉的特点 ,对发展我国陶瓷窑炉产业提出了建议     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.