硝酸甲酯与不同亲核试剂的SN2反应的理论研究

用从头计算和半经验分子轨道ＡＭ１方法分别对系列亲核试剂和硝酸甲酯的电子结构以及它们之间的气相ＳＮ２反应进行了理论研究，揭示了反应过程中体系的结构，能量和电荷的递变规律，由反应活化能得了这些亲核试剂的亲核性次序为：ＯＨ＾－〉Ｆ＾－〉Ｉ＾－〉ＮＯ＾－３〉ＣＮ＾－〉Ｂｒ＾－〉Ｃｌ＾－〉Ｎ＾－３。     

TiO2陶瓷顶层膜的化学气相淀积生长研究

以ＴｉＣｌ和Ｔｉ（ＯＣ４Ｈ９）４为源物质采用热化学气相淀只（ＣＶＤ）法及射频ＰＣＶＤ法在多孔α－Ａｌ２Ｏ３陶瓷衬底上淀积生长ＴｉＯ２薄膜，观测ＴｉＯ２膜的生长方式、生长速率以及结构和表面形貌等，讨论其生长机制，评价ＣＶＤ改性生长的顶怪ＴｉＯ２陶瓷膜的气体渗透性。     

担载多孔Al2O3

研究了溶胶－凝胶法在多孔陶瓷载体上制备多孔Ａｌ２Ｏ３膜的工艺条件，发现在孔直径为１．１和１．６μｍ的多孔陶瓷载体上必须经过多次重复浸渍－干燥－焙烧过程，才能制备出担载均匀的多孔Ａｌ２Ｏ３膜，对溶胶和多孔陶瓷载体进行适当的化学改性后，能够减少浸渍－干燥－焙烧过程重复的次数，对Ａｌ２Ｏ３膜的孔径大小和透气性能进行了表征。     

担载多孔Al_2O_3膜的制备

研究了溶胶－凝胶法在多孔陶瓷载体上制备多孔Ａｌ２Ｏ３膜的工艺条件。发现在孔直径为１．１和１．６ｕｍ的多孔陶瓷载体上必须经过多次重复浸渍干燥－焙烧过程，才能制备出担载均匀的多孔Ａｌ２Ｏ３膜。对溶胶和多孔陶瓷载体进行适当的化学改性后，能够减少浸渍－干燥－焙烧过程重复的次数。对Ａｌ２Ｏ３膜的孔径大小和透气性能进行了表征。     

过硫酸胺与N－［（3－二甲氨基）丙基］丙烯酰胺氧化还原引发体系的研究

过硫酸胺与Ｎ－［（３－二甲氨基）丙基］丙烯酰胺氧化还原引发体系的研究司堃，郭新秋，丘坤元（北京大学化学与分子工程学院北京１００８７１）关键词Ｎ－取代丙烯酰胺，氧化还原体系，反应动力学，端基分析，反应机理Ｎ－［（３一二甲氨基）两基］丙烯酸胺（ＤＭＡＰＡ...     

芳胺常压气相N—烷基化反应研究

在固定床催化反应器中常压下研究了芳胺和醇的气相法Ｎ－烷基化反应。考察了γ－Ａｌ２Ｏ３系列催化剂的反应性能，筛选出了两种适用于苯胺Ｎ－甲基化反应且性能较好的催化剂。反应条件为：在甲醇和苯胺的摩尔比为３：１时，反应温度为２８０℃，液时空速为０．３ｈ＾－１的条件下，苯胺转化率为９９％，生成Ｎ，Ｎ－二甲基苯胺（ＤＭＡ）的选择性为９２％。研究了甲醇和芳环上不同位置取代的甲基苯胺的反应规律，其转化率顺序：苯胺     

胺类化合物气相色谱保留指数与结构的相关性研究

应用Ａｍ指数和引力指数Ｇ１对在３种体系下的胺类化合物的气相色谱保留指数和结构进行了相关性研究,并运用最佳子变量集算法和人工神经网法进行了计算分析,在非极性固定相ＯＶ－１０１和极性固定相ＯＶ－２２５和ＮＧＡ下均获得了比较好的相关模型。     

胆甾液晶二氮杂冠醚—Eu（Ⅲ）配合物LB膜和荧光性质研究

研究了胆甾液晶二氮杂冠醚Ｎ，Ｎ′－双（胆甾－５－烯－３β－氧羰甲基）－１，１０－二氮－４，７，１３，１６－四氧环十八烷（１）及其与Ｅｕ＾３＋的配合物（２），２一苯甲酸的混配物（３）的ＬＢ膜和荧光性质，结果表明：１，２和３在水溶液亚相液面形成稳定的单分子膜，但只有１的单分子面积受亚相ｐＨ的影响１，２和３的单分子膜都容易转移到石英基片上形成ＬＢ膜，其中２和３为Ｘ型，转移比分别为０．６和１．０，在ＬＢ膜     

ClnAlNHn和HnAlNHn(n=1～3)的振动光谱与化学键性质的研究

用从头计算分子轨道法和密度泛函理论，在ＨＦ／６－３１Ｇ＊和Ｂ３ＬＹＰ／６－３１Ｇ＊水平上对ＣｌｎＡｌＮＨｎ和ＨａＡｌＮＨｎ（ｎ＝１～３）及其碎片分子的几何构型、电子结构、振动光谱和化学热力学性质进行了理论研究。结果表明，优化几何参数与实验值相。ＣｌＡｌＮＨ２和Ｈ２ＡｌＮＨ２分子中，Ａｌ－Ｎ键为由一个σ键和一个π键组成的双重键，旋转势垒分别为３４．１０和５４．３５ＫＪ．ｍｏｌ＾－１，而Ｃｌ３ＡｌＮＨ     

含手性膦配体的钯（Ⅱ）配合物的二维核磁共振研究

利用一维和二维ＮＭＲ技术，对含有手性膦配体甲基－３脱氧－３（二苯膦基）－４，６－氧－苄叉基－α－Ｄ一吡喃阿卓糖苷（３－ＭＢＰＡ）和甲基－２－脱氧－２－（二苯膦基）－４，６－氧－苄叉基－α－Ｄ－吡喃阿卓糖苷（２－ＭＢＰＡ）的钯配合物ｔｒａｎｓ—［Ｐｄ（３－ＭＢＰＡＨ）２ＣＩ２」（１），ｔｒａｎｓ－［Ｐｄ（２－ＭＢＰＡＨ）２ＣＩ２］（２）和ｃｉｓ－［Ｐｄ（３－ＭＢＰＡ）２］（３），ｃｉｓ－［Ｐｄ（２－ＭＢＰＡ）２］（４）进行~１Ｈ和~（１３）Ｃ ＮＭＲ谱分析，归属了全部的~１Ｈ和~（１３）Ｃ ＮＭＲ谱线，并根据磷的化学位移及Ｒａｍａｎ谱确定化合物（３）和（４）是顺式构型，对实验中的一些现象也做了简单讨论。     

Plasma chemical vapor deposition of TiN

Experiments indicate that the temperature in chemical vapor deposition (CVD) of TiN can be decreased from about 1000°C in conventional CVD to about 500°C by the application of a D.C. nonequilibrium plasma. The hardness of the TiN film is greater than 2000 kg/mm² (Vickers). The effect of pressure, ratio of gas mixture, and discharge parameters on the film deposition rate, its hardness, and microstructures has been studied.     

Synthesis of Polymer Films by an Electron Emission CVD Technique

A low-pressure chemical vapor deposition (CVD) technique based on the formation of reactive film precursors by dissociation of gas-phase reactants by electron impact is described. The electrons are emitted by a hot filament and a positive bias voltage applied to the substrate provides control of the emission current. The emitted electrons are primarily responsible for the gas dissociation, but secondary electrons resulting from electron-impact ionization of the gas molecules also produce reactive species, contributing to the deposition process. This technique was used to synthesize polymer films from C₂H₂–N₂ mixtures at pressures ranging from 1–10 Pa. The dependencies of the current collected by the substrate, I_S, on the substrate bias voltage, V_S, and on the gas pressure were determined. The film deposition rate was measured as a function of several deposition variables such as I_S, V_S, and the N₂ to C₂H₂ flow rate ratio. Oxygen was present in the films as a contaminant. Analyses by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) provided insight into the film molecular structure, allowing identification of various functional groups and binding states of the C- and N–atoms. From the XPS spectra, the N/C and O/C ratios were determined.     

Fundamental physicochemical regularities of the chemical vapor deposition of nickel oxide layers

Physicochemical regularities of the chemical vapor deposition (CVD) of nickel oxide layers in the (EtCp)₂Ni–O₃–O₂–Ar reaction system at a reduced pressure were studied. Dependences of growth rate of NiO layers on deposition temperature, linear gas flow velocity, and roughness were derived. A mass-spectrometric study of the composition of the reaction gas phases formed in these systems provided evidence about the fundamental physicochemical regularities of the CVD process, which is important for solving applied problems associated with the development of technological equipment and industrial technology for deposition of NiO layers.     

Superhigh-Rate Epitaxial Silicon Thick Film Deposition from Trichlorosilane by Mesoplasma Chemical Vapor Deposition

Homoepitaxial Si thick films have been deposited by mesoplasma chemical vapor deposition (CVD) with SiHCl₃ (TCS)–H₂–Ar gas mixtures. The addition of a small amount of H₂ has been found to not only modify the film structure from polycrystalline to epitaxial but also effectively improve the deposition efficiency and film purity by removing Cl in the form of HCl. However, an excess introduction of H₂ decreases the deposition efficiency owing to the shrinkage of the plasma flame. On the other hand, an increase in TCS flow rate increases the epitaxial deposition rate despite exhibiting a saturating tendency, while the material yield tends to decrease gradually due possibly to an increase in the Cl atoms. Also, we observed a critical limit in the TCS flow rate for epitaxial growth, beyond which a polycrystalline film resulted. However, when RF input power was increased, not only the upper limit of TCS flow rate for epitaxy was extended but also the deposition yield was improved so that the deposition rate reached ~700 nm/s with the material yield of >50 % at 30 kW input power with an H₂/TCS ratio of 1.5. Additionally, high input power is found to be beneficial to decrease Cl atom incorporation into the film and improve the Hall mobility of the films. An epitaxial film with a Cl atom concentration of less than 3 × 10¹⁶ cm^?3 and a Hall mobility as high as 250 cm²/(V·s) was obtained at 30 kW input power.     

A transparent boron-nitrogen thin film formed by plasma CVD out of the discharge region

A transparent boron-nitrogen thin film of thickness 550 nm was successfully deposited out of the discharge region by rf plasma CVD. The deposition was performed with diborane (4.8 vol % in N₂) as the reactant gas and argon as the carrier gas by an inductively coupled reactor at a frequency of 13.56 MHz. The transparent films could be obtained at a low pressure of about 30 Pa, at a discharge power level of 30 W, and at room temperature without heating the substrate. The thin films obtained by rf plasma are compared with those obtained by microwave plasma. Both the refractive index and the deposition rate for the films deposited by microwave plasma are discussed according to the deposition conditions.     

Structural,thermal, and electrical properties of carbonaceous films containing palladium nanocrystals

Carbonaceous films containing Pd nanocrystals can be applied as active layers in gas sensor applications. In this article we show results of studies of C-Pd films, obtained with two different methods: (1) physical and (2) physical + chemical deposition. First type of film prepared by physical vapor deposition (PVD) process was composed of fullerenes, amorphous carbon, and palladium nanograins. In the second method PVD film was modified in chemical vapor deposition (CVD) process forming a foam-like structure. Both types of films were studied by SEM, TEM, TGA, and electrical characterization (measurement of resistivity versus composition of gaseous hydrocarbons mixture).     

Thin Film Growth of Germanium Selenides from PECVD of GeCl<Subscript>4</Subscript> and Dimethyl Selenide

Plasma enhanced chemical vapor deposition (PECVD) of germanium selenide thin films from germanium tetrachloride and dimethyl selenide was studied to determine the viability of these reagents for thin film deposition. Germanium tetrachloride and alkylselenides were selected as candidates for these reactions due to their lower toxicities and higher availabilities compared to the more typical substitutes: germane and hydrogen selenide in the formation of germanium selenides. Dimethyl selenide was used successfully for the deposition of germanium selenides. Variation in film stoichiometry was observed by the modification of reactant gas flow ratios. Relative mass flow rates were varied in order to determine their effect on germanium chalcogenide deposition, and the effect of these flow rate modifications on the film thickness, structural properties, and composition are reported.     

Mass Transport of β-Diketonate Precursors for MOCVD of YBa_2Cu_3O_(7-δ) High T_c Superconducting Thin Films

IntroductionSoonafterthediscoveryofhighT.supercoducting(HTSC)oxides,metalor-ganicchemicalvapourdeposition(MOCVD)wasproposedforpreparingtheirthinfilms[1j.Asgenerallyacceptedtoday['J,thistechniquehasdemonstrateditssuperioradvantagesinmakinglargeareahighqualityHTSCthinfilmsandwillplayamajorroleintheadvanceofdeviceapplicationofHTSCthinfilmsoverthenextfewyears.TheprecursorsusedinMOCVDforpreparinghighT.superconductingthinfilmsaremostlymetalbeta-diketonates.Theyaresolidsatroomtemperatureand…     

Cobalt ultrathin film catalyzed ethanol chemical vapor deposition of single-walled carbon nanotubes

We report a simple and efficient chemical vapor deposition (CVD) process that can grow oriented and long single-walled carbon nanotubes (SWNTs) using a cobalt ultrathin film ( approximately 1 nm) as the catalyst and ethanol as carbon feedstock. In the process, millimeter- to centimeter-long, oriented and high-quality SWNTs can grow horizontally on various flat substrate surfaces, traverse slits as large as hundreds of micrometers wide, or grow over vertical barriers as high as 20 microm. Such observations demonstrate that the carbon nanotubes are suspended in the gas flow during the growth. The trace amount of self-contained water (0.2-5 wt %) in ethanol may act as a mild oxidizer to clean the nanotubes and to elongate the lifetime of the catalysts, but no yield improvement was observed at the CVD temperature of 850 degrees C. We found that tilting the substrates supporting the Co ultrathin film catalysts can grow more, longer carbon nanotubes. A mechanism is discussed for the growth of long SWNTs.     

Superclean Growth of Graphene Using a Cold‐Wall Chemical Vapor Deposition Approach

Chemical vapor deposition (CVD) has become a promising approach for the industrial production of graphene films with appealing controllability and uniformity. However, in the conventional hot‐wall CVD system, CVD‐derived graphene films suffer from surface contamination originating from the gas‐phase reaction during the high‐temperature growth. Shown here is that the cold‐wall CVD system is capable of suppressing the gas‐phase reaction, and achieves the superclean growth of graphene films in a controllable manner. The as‐received superclean graphene film, exhibiting improved optical and electrical properties, was proven to be an ideal candidate material used as transparent electrodes and substrate for epitaxial growth. This study provides a new promising choice for industrial production of high‐quality graphene films, and the finding about the engineering of the gas‐phase reaction, which is usually overlooked, will be instructive for future research on CVD growth of graphene.