半导体制冷技术在化工上的应用展望

半导体制冷是阿尔帕效应在制冷方面的应用,被称为21世纪新的绿色"冷源"。但是半导体制冷技术在化工上的应用并不多见,如果半导体制冷技术能在化工上得到很好的应用,它将对节能环保和化工设备的集成化具有重要的意义。文章介绍了半导体制冷的原理和特点及其在化工上的应用现状,并对今后半导体制冷在化工上的应用做了几点展望。     

超高纯度锗和硅的制造

引言半导体物理学近年来得到飞速的发展,在半导体的制造、研究和应用方面取得了极大的成就。А.Ф.约飞院士在苏联科学院1954年召开的半导体材料会议上的报告中曾指出,研究半导体材料是当前摆在科学和技术面前的重大任务。对于化学家和冶金学家来说,制造合乎要求的半导体材料则是应该担当的责任。锗和硅是最重要的半导体材料。半导体仪器     

半导体制冷器在分析仪表中应用的优化设计方法

半导体制冷器在分析仪器中有着广泛的应用,但由于设计上的缺陷造成半导体制冷器经常损坏,通过时小型制冷系统在供电电压、控制方法、胶封处理、合理安装、并联使用和增加完善的保护措施等几个方面的优化改进,能够极大地延长半导体制冷器的使用寿命.从实用的角度介绍了延长半导体使用寿命的方法,对于小型制冷系统的设计人员有一定指导意义.     

上转换/半导体核壳结构纳米复合材料光催化研究进展

上转换荧光材料具有将近红外光转换为紫外光和可见光的光学性能,与传统的半导体材料复合,使其光谱响应拓展到近红外区域,充分利用太阳光,从而提高光催化效率。核壳结构除能够有效地防止核(上转换纳米材料)被污染失活外,还可以使其紧密接触,有利于荧光共振能量的传递,提高壳(半导体材料)对光的利用率。系统论述了上转换半导体核壳结构纳米复合材料的制备方法、催化降解效率和催化影响因素,对此类复合材料的结合和催化机理进行分析,指出今后应加强高效率荧光材料和催化活性更强的半导体材料复合及如何在实际中应用的研究。     

二氧化碳在P^＋／P—Si半导体电极上光电化学还原的研究

1870年,Royer使用Zn电极将CO_2还原为HCOOH。近年来,人们对CO_2在几十种金属电极上的电化学还原进行了深入的研究。但普遍存在的问题是CO_2在金属电极上还原的过电位较大,导致耗电较多。而半导体电极能吸收光能降低CO_2还原的过电位,所以人们对CO_2在半导体电极上的光电还原进行了探讨,使用的光阴极材料有P-GaP,P-GaAs,P-InP,P-CdTe。半导体Si的禁带宽度E_g=1.12eV,     

电沉积制备半导体纳米合金材料的研究进展

近年来,采用电沉积法制备了多种具有优异特性的半导体纳米合金材料,如光电半导体材料和热电半导体纳米材料等.与其它方法相比,具有许多优点.它不仅工艺简单、方便,而且价格便宜,并可在大小不同和形状各异的基体上沉积.研究表明:可以通过目标系统配置,就可获得高效率的半导体纳米材料,并拓宽其应用.     

用于半导体工业的杜邦新Kalrez全氟弹性体部件亮相

在2008欧洲半导体设备与材料产业展览会上,杜邦高性能弹性体公司（DPE）重点推出专为半导体热处理过程开发的最新Kalrez8900全氟弹性体部件。它实现了在更高温度的半导体制造过程中更长的密封寿命,减少了昂贵的设备停工时间,降低了设备拥有成本。DPE还公布了Kalrez9100部件最近在沉积、蚀刻、灰化／剥离等制程上的成功商业化,并推出了可提高光伏生产密封可靠性的Kalrez产品。     

自动化公司亮相半导体展会 罗克韦尔自动化参加SEMICON China2003

20 0 3 0 3 12～ 14 ,罗克韦尔自动化参加了在上海浦东新国际博览中心举行的半导体设备和材料展览会 (SEMICONChina 2 0 0 3)。作为此次展会上唯一的自动化公司 ,罗克韦尔自动化现场展示了集成架构、变频器和RSView人机界面软件等 ,吸引了许多与会者驻足。大中国区总经理夏明伟、全球半导体销售经理艾略特还亲自来到展会现场 ,回答了参观者的很多问题。不久前 ,罗克韦尔自动化全球副总裁兰迪 -弗里曼率领一支半导体销售队伍来到上海进行考察。时隔半个月 ,罗克韦尔自动化又参加了这次半导体展会 ,显示了公司对中国半导体市场的重视。罗…     

C．A．染料文摘（145：5、6、7、8、9）

145：125988x酞菁络合物的应用Tretyakova,I．N．等（Inst. Obshch. Neorg. Khim. Im. V.I. Vemadskogo） Ukrainskii Khimicheskii Zhumal （Russian Edition） 2005, 7 （11-12）, 85-92 （俄文） 一篇评论,对酞菁系统作为新的电致变色,非线性光学液晶材料、传感器、半导体在生物和医药中的应用可能性作了评述。     

半导体制冷晶体直接镀镍的研究

1　前言我公司是一个生产半导体制冷器的企业 ,在半导体N型、P型基材表面上需进行电镀。至今一直采用如下工艺 :晶片基材喷砂喷镍喷砂预镀镍镀镍浸锡切割组立上述表面处理工艺环节过多 ,成本较高 ,喷砂、喷镍中易引起晶片破裂。同时 ,因晶片表面受到高温、高压的冲击 ,影响制冷性能 ,导致半导体制冷器最高温差在△ 74°C ,低于国际先进水平的△ 76°C。据介绍 ,如果减少对晶体的热冲击 ,采用在半导体N型、P型晶片表面直接电镀 ,可以把温差提高 1.5～2 .0°C。但由于半导体制冷材料的特性 ,在这上面直接电镀镍层 ,镀层结合力不够稳定 ,平…     

碳酸钠促进选择性非催化还原脱硝的动力学模型与模拟

Abstract The detailed kinetic model of selective non-catalytic reduction （SNCR） of nitric oxide, including so-dium species reactions, was deyeloped on the basis of recent studies on thermal DeNOx mechanism, NOxOUTmechanism and promotion mechanism of Na2CO3. The model was validated by comparison with several experi-mental findings, thus providing an effective tool for the primary and promoted SNCR process simulation. Experimental and simulated results show part-per-million level of sodium carbonate enhances NO removal efficiency andextend the effective SNCR temperature range in comparison with use of a nitrogen agent alone. The kinetic modeling, sensitivity and rate-of-production analysis suggest that the performance improvement can be explained as ho-mogeneous sodium species reactions producing more reactive OH radicals. The net result of sodium species reac-tions is conversion of H2O and inactive HO2 radicals into reactive OH radicals, i.e. H2O＋HO2=3OH, which enhances the SNCR performance of nitrogen agents by mainly increasing the production rate of NH2 radicals. More-over, N2O and CO are eliminated diversely via the reactions Na＋N20=NaO＋N2, NaO＋CO=Na＋CO2 andNaO2＋CO =NaO＋CO2, in.the pro.moted SNCR process, especially in the NOxOUT process.     

氧化锌分散体光反应产生的自由基中间体

溶液中光诱导的电子转移反应已进行了大量的研究。而半导体粉末在水相或非水溶剂中的光化学研究也与自俱增。这种光化学与成像体系、太阳能转换以及光催化或污物的光降解有关。因此,越来越引起人们的重视。 Harbour和Hair用自旋捕捉技术研究了在ZnO-H_2O的分散体系中光合成过氧化氢,并检测到羟基自由基。他们认为氧化锌可能通过水的氧化将O_2还原成H_2O_2,从而使太阳能转换成化学能。人们自然会想到ZnO在其它溶剂中是否-也能观察到溶剂光氧化     

Radiation Chemistry of Ethylene Glycol,Meso-Erythritol, 2-Deoxy-D-Ribose and Alkyl Phosphates as DNA Model Compounds

The γ-radiolysis of ethylene glycol, meso-erythritol, 2-deoxy-ribose, and alkyl phosphates has been studied in diluted (10^?2 M), N₂ O-saturated, deoxygenated aqueous solutions. Products and their G values have been determined. Reaction schemes were derived from complete material balances. In the polyols the primary attack of the radiolytically formed OH radicals and H atoms leads to α, β-dihydroxyalkyl radicals (A) which eliminate water to give substituted α-carbonyl-methyl radicals: (B) Disproportionation reactions of the radicals A and B yield products having the structural units ? CO? CHOH? and ? CO? CH₂ —. In ethylene glycol a chain reaction is induced, radical B abstracts a hydrogen from ethylene glycol to give acetaldehyde and radical A. In 2-deoxy-ribose the major attack is at C-1. Products from this radical are 2-deoxy-ribonic acid and 2,5-dideoxy-ribonic acid. In the formation of the latter a rearrangement is involved. With trimethyl phosphate, the reaction of the solvated electron is only small (2 × 10^s 1/mole sec), as shown by pulse radiolysis. Dimethyl and methyl phosphates do not react with the solvated electron to a measurable extent. The attack of the OH radical apparently leads to a cleavage of the alkyl phosphate linkage.     

Radical formation in polymer electrolyte fuel cell components as studied by ESR spectroscopy

To clarify the deterioration mechanism for polymer electrolyte fuel cells, OH radical formation at the catalyst electrodes was investigated by ESR (electron spin resonance) spectroscopy using a flow cell with the catalyst electrodes. OH radicals produced from H₂O₂ were detected by a DMPO (5,5-dimethyl-1-pyrroline N-oxide) spin-trapping method for a Nafion-coated Pt/Carbon catalyst electrode under a high potential (0.85 V versus RHE) on supplying H₂ and under low potentials (lower than 0.40 V). When Pt–Ru catalysts were employed instead of Pt catalysts, the formation of OH radicals was barely detected. The results suggest the possibility of the formation of OH radicals by the oxidation of H₂O₂ at the oxidized Pt surface under a positive potential as well as the reduction of H₂O₂ at the clean Pt surface under a low potential.     

Synergistic flame retardancy of tris(1-methoxy-2,2,6,6-tetramethyl-piperidin-4-yl)phosphite and tris(2,4,6-tribromophenoxy)-1,3,5-triazine/Sb2O3 in high-impact polystyrene

Synergistic flame retardancy of tris(1-methoxy-2,2,6,6-tetramethyl-piperidin-4-yl) phosphite (NORPM) and tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBPC)/Sb₂O₃ in high-impact polystyrene (HIPS) was studied by limiting oxygen index (LOI) determination, UL-94 test, and cone calorimetry test (CCT). NORPM has an exceptional synergistic effect in HIPS. When the dosage of TTBPC, Sb₂O₃, and NORPM was 12.8, 3.2, and 0.5 wt% respectively, flame retardant effectivity and synergistic effectivity were 0.424 and 1.15 respectively. Compared with the Flame retardant (FR)-HIPS containing 16.0 wt% of TTBPC/Sb₂O₃, the LOI of FR-HIPS increases from 23.8% to 25.4%, the flame-retardant rating of FR-HIPS can be improved from UL 94 V-2 to V-0, and the peak heat release rate and total heat release are significantly reduced by combining NORPM in 0.5 wt% concentration. NORPM induces the synergistic effect mainly through the following mechanisms: the active radicals produced by the pyrolysis of NORPM promote the release of bromine radicals from TTBPC and the formation of HBr, which improves the flame retardancy of TTBPC; the above active radicals, together with HBr, quench active free radicals, such as the hydroxyl radical (·OH) and decompose the free radical source, which interrupts the chain reaction during combustion and results in a more efficient flame retardant effect in gaseous phase.     

HOCO radical chemistry

Free radicals are important species in atmospheric chemistry, combustion, plasma environments, interstellar clouds, and biochemistry. Therefore, researchers would like to understand the formation mechanism, structure, stability, reactivity, spectroscopy, and dynamics of these chemical species. However, due to the presence of one or more unpaired electrons, radicals are often very reactive and have short lifetimes, which makes it difficult to conduct experiments. The HOCO radical appears in the atmosphere as well as in combustion environments and plays an important role in the conversion of CO to CO(2). Through the interplay between theoretical and experimental investigations, researchers have only recently understood the chemical role of the HOCO radical. In this Account, we systematically describe the current state of knowledge of the HOCO radical based on recent theoretical and experimental studies. This radical's two stable conformers, trans- and cis-HOCO, have been identified by high-level ab initio calculations and experimental spectroscopy. trans-HOCO is more stable by approximately 1.8 kcal/mol. The heat of formation of HOCO (298 K) was determined to be -43.0 ± 0.5 kcal/mol, giving a potential well depth of 30.1 ± 0.5 kcal/mol relative to the asymptote of the reactants OH + CO. The HOCO radical is very reactive. In most reactions between the HOCO radical and atoms, the HOCO radical acts as a hydrogen donor to reaction partners. Generally, the hydrogen is transferred through the formation of an association intermediate, which then proceeds through a molecular elimination step to produce the reaction products. The reaction rates of HOCO with some small radicals fall in the range of 10(-11)-10(-10) cm(3) molecule(-1) s(-1). These results clearly illustrate important features in the reactivity of the HOCO radical with other molecules.     

利用热激活过硫酸钾技术降解噻虫胺

探讨了多种影响因素对热激活过硫酸钾技术降解噻虫胺的影响,并检测反应体系中的活性自由基种类。结果表明,噻虫胺的降解符合准一级反应动力学规律。提高反应温度和S2O82-浓度,噻虫胺的降解速率都迅速增大;酸性和中性条件下的降解速率高于碱性条件;水溶液中Cl~-和HCO_3~-的存在影响噻虫胺的降解效果;自由基探针实验验证了反应体系中同时存在SO_4~-·和·OH两种自由基,酸性和中性条件下,以SO_4~-·为主,碱性时·OH含量较多。     

ZnO纳米晶的光催化还原性能研究

用直接沉淀法合成粒径小于20 nm的氧化锌颗粒,采用XRD和TEM等技术对其进行表征.在其悬浮体系中对CO32-进行光催化还原实验,以光谱分析法测定还原产物甲酸、甲醛和甲醇的含量,研究催化剂的浓度、CO32-浓度、pH值等因素对还原产物产率的影响.结果表明,纳米氧化锌具有较强的光催化还原活性,光激发生成的电子可将CO2转化为甲酸、甲醛及甲醇等基本有机原料.     

Influence of the hard-to-soft segment ratio on the adhesion of water-borne polyurethane adhesive

Three water-borne polyurethane dispersions were synthesised by the pre-polymer mixing process. Different hard segment contents in the polyurethanes were obtained by varying the diisocyanate/macroglycol (NCO/OH) molar ratio. A decrease in the NCO/OH ratio produced an increase in the mean particle size and in the pre-polymer viscosity, as well as a decrease in the molecular weight of the polyurethane. On the other hand, the lower the NCO/OH ratio, the more crystalline the polyurethane and the lower the resistance to flow at high temperature. Lower NCO/OH ratios improved the thermal degradation stability of the polyurethane. Finally, a high initial adhesion to PVC was obtained in all joints produced with the aqueous polyurethane dispersions and the final adhesion increased as the NCO/OH ratio in the water-borne polyurethane adhesive decreased.     

稀土材料增强自由基减废技术

引言 为了提高内燃机的燃烧效率,降低有害废气的排放,国内外采用了很多技术,如绝热发动机、催化燃烧、富氧燃烧、废气涡轮增压、中冷技术、均匀充量压缩燃烧(HCCI)等.同时对柴油也进行了各种实验,如将柴油通过电场[1]可加快燃烧速度,提高热导和蒸汽.也有掺水乳化柴油的研究[2],柴油催化燃烧添加剂制备与研究[3],水三元复合乳化燃料[4],纳米水合燃料[5]等技术,这些技术稳定性比较差,一定程度上损伤了机器,因此很多技术不宜推广.