旋转CVI快速沉积热解碳基体

采用一种新的CVI工艺(旋转CVI)进行了二维碳布沉积热解碳基体的实验研究.通过实验优化工艺参数,在低压(5 kPa)、高温(1 100 ℃)、体积分数为62.5%的C3H6与3.5 mm.min-1的碳布旋转线速度条件下,获得了微观孔隙中0.25 μm.h-1的热解碳沉积速度、约7%的C3H6转化率与理想的热解碳基体形貌.分析了旋转CVI工艺中沉积温度和C3H6浓度等分别对沉积速度、热解碳基体形貌及C3H6转化率的影响.     

碳毡自加热热解沉积致密化工艺初探

本文通过对不同尺寸、叠层层数,密度,形状和孔洞的碳毡进行自加热研究,探究了不同物性参数碳毡预制体的自加热规律,并进一步进行了自加热热解沉积制备C／C复合材料的可行性研究。研究发现：预制体在加热中能维持高温,并能在预制体中形成一定的逆向温度梯度,在自加热的工艺条件下,热解沉积制备C／C复合材料工艺是完全可行的。     

高陶瓷转化率聚碳硅烷的固化行为研究

采用非等温DSC法、红外和旋转流变仪研究了具有高陶瓷转化率的聚碳硅烷(PCAS)的固化行为。通过Kissinger,Ozawa和Crane方程计算得到PCAS的固化动力学参数:表观活化能E=122.5 kJ/mol,固化反应级数n=0.95,指前因子A=9.74×108。PCAS树脂在固化过程中发生Diels-Alder反应和硅氢化反应,可在220℃快速固化,粘度从7.12×103Pa·s变化至1.52×107Pa·s。     

沉积温度对微波热解CVI制备碳/碳复合材料密度及组织结构的影响

以碳毡为预制体,N2为稀释气体,甲烷为碳源前驱体,其分压为10 kPa,滞留时间为0.15 s的工艺条件下,研究了不同沉积温度对微波热解化学气相渗透(chemical vapor infiltration,CVI)工艺制备碳/碳复合材料的致密化速率、样品的体积密度及其密度均匀性的影响,并对其组织结构进行了观察.分析了沉积温度对微波热解CVI工艺制备碳/碳复合材料的密度与组织结构的变化规律.结果表明:在微波热解CVI工艺中,随着沉积温度的降低,碳毡预制体的致密化速率及最终体积密度呈现先升后降,1100 ℃沉积制备复合材料的密度均匀性最好,并呈现从内到外逐步沉积的规律.热解碳的织构主要为中等织构.     

煤催化微波热解技术及其碳基吸波催化剂研究进展

微波技术与煤热解技术结合而成的煤微波热解技术可高效地治理传统煤热解技术中环境污染高和资源利用效率低的难题,为低变质煤的清洁高效利用和分级提质利用提供了新的思路。煤催化微波热解技术能有效改善热解升温特性和产物分布,从而受到较多学者的关注。本文从低变质煤催化微波热解技术发展历程着手,概述了国内外煤催化微波热解研究技术进展,通过加入Fe、Co、Ni和Cu等金属化合物或焦炭、活性炭等碳材料作为吸波剂,能显著增强煤对微波的吸收能力,提高热解升温速率、产物收率及产物质量,而有些金属化合物在微波热解反应中不仅起到吸波作用,还具有催化作用。碳基吸波催化剂作为一种性能优越的煤微波热解催化剂,具有优越的电磁和吸波性能、较好的催化性能和高经济性等优点,本文在煤催化微波热解技术研究现状的基础上,对碳基吸波催化剂进行了较为详细地分析,概述了碳基吸波催化剂的碳基体和催化活性组分的研究进展,对比了3种常见碳基吸波催化剂制备方法的优劣势。最后,总结了碳基吸波催化剂在研发过程中存在的难题,并展望了低变质煤催化微波热解技术的应用前景。     

C涂层对SiC纤维介电性能的影响

以丙烯(C3H6)和氮气(N2)为反应气,用低压化学气相沉积(LPCVD)法在SiC纤维表面制备了热解碳层。考察了碳层厚度对纤维介电性能、反应气中C3H6体积分数对碳层微观结构及纤维介电性能的影响。结果表明,沉积100nm厚碳层后,纤维复介电常数实部由76.4～73.8增加到176.9～174.3,虚部由67.5～66.0增加到214.7～210.2。但碳层厚度进一步增大到200nm后,介电常数的增加不多。当C3H6体积分数由0.6降为0.45时,碳层结构有序化程度降低,晶粒变粗大,纤维介电常数实部由176.9～174.3降为156.4～153.7,虚部由214.7～210.2降为194.5～189.6。     

碳沉积法制富氮用炭分子筛的研究

本文提出的碳沉积法是用煤焦油馏分油的有机溶液浸渍煤炭化物,然后热解以进行“孔调变”。确定了最佳工艺条件,制得富氮性能良好的炭分子筛。并用D-A方程求取了各种样品的微孔结构参数。     

二维纳米碳材料的制备及其在苯甲醇选择性氧化反应中的应用

本文围绕非金属纳米碳材料的制备及其在苯甲醇选择性氧化反应中的性能调控和机理开展研究。选择富含-OH的微晶纤维素（α-cellulose）为前驱体,在较低的温度（500～700℃）下热解制备了二维纳米碳材料。研究发现,该材料在90℃下实现高效的苯甲醇选择氧化,转化率和选择性分别达到92.1%和93.7%。本研究为开发高效催化剂和促进废弃物资源化利用提供了技术支持,并对碳材料在催化领域的应用具有重要的指导意义。     

化学气相沉积热解炭机理及其化学动力学

综述了化学气相沉积热解炭的沉积机理、化学动力学的发展状况及一些基本理论问题，着重介绍了K.J.Huettinger等提出的沉积模型。     

碳纤维与热解碳基体中间相沥青过渡层复合材料的制备方法

本发明涉及一种碳纤维与热解碳基体中间相沥青过渡层复合材料的制备办法。先将碳纤维预制体放红不锈钢浸渍罐中,用中间相沥青粉包埋后放入浸渍炉,存惰性气氛保护下进行真空浸渍,然后存碳化炉中,在惰性气氛保护下,采用不同升温速率分段升温、保温,进行碳化,然后放入化学气相沉积炉中用化学气相渗透法进行沉积,制成中间相沥青过渡层碳／碳复合材料成品。     

Indium Tin Oxide@Carbon Core-Shell Nanowire and Jagged Indium Tin Oxide Nanowire

This paper reports two new indium tin oxide (ITO)-based nanostructures, namely ITO@carbon core–shell nanowire and jagged ITO nanowire. The ITO@carbon core–shell nanowires (~50 nm in diameter, 1–5 μm in length,) were prepared by a chemical vapor deposition process from commercial ITO nanoparticles. A carbon overlayer (~5–10 in thickness) was observed around ITO nanowire core, which was in situ formed by the catalytic decomposition of acetylene gas. This carbon overlayer could be easily removed after calcination in air at an elevated temperature of 700°C, thus forming jagged ITO nanowires (~40–45 nm in diameter). The growth mechanisms of ITO@carbon core–shell nanowire and jagged ITO nanowire were also suggested.     

炭质吸附剂的孔结构修饰及表征

用1-丁烯炭沉积法修饰碳分子筛的孔结构。考察了炭沉积的位置、浓度、温度、沉积时间和活性组分对沉积效果的影响。结果表明,当1-丁烯浓度为31.8%,沉积温度为993 K,沉积时间为10 min,炭沉积量合适时,空气变压吸附(PSA)N2浓度可达85.6%;对浸Ni(Ni载持量5%)样,炭沉积主要发生在接近外表面的中孔和大孔中,不容易导致孔的堵塞,Ni的加入起到了提高炭沉积选择性的作用,(PSA)N2浓度可达91.0%。FT-IR、XRD、in-situTG/DTA测试表明,经炭沉积修饰后的碳分子筛具有微孔分布独特的骨架网络结构。     

Characterization of Photoluminescent (Y1–xEux)2O3 Thin Films Prepared by Metallorganic Chemical Vapor Deposition

The purpose of this study was to identify and correlate the microstructural and luminescence properties of europium-doped Y₂O₃ (Y_{1– x} Eu _x )₂O₃ thin films deposited by metallorganic chemical vapor deposition (MOCVD), as a function of deposition time and temperature. The influence of deposition parameters on the crystallite size and microstructural morphology were examined, as well as the influence of these parameters on the photoluminescence emission spectra. (Y_{1– x} Eu _x )₂O₃ thin films were deposited onto (111) silicon and (001) sapphire substrates by MOCVD. The films were grown by reacting yttrium and europium tris(2,2,6,6-tetramethyl–3,5-heptanedionate) precursors with an oxygen atmosphere at low pressures (5 torr (1.7 × 10³ Pa)) and low substrate temperatures (500°–700°C). The films deposited at 500°C were smooth and composed of nanocrystalline regions of cubic Y₂O₃, grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600°C developed, with increasing deposition time, from a flat, nanocrystalline morphology into a platelike growth morphology with [111] orientation. Monoclinic (Y_{1– x} Eu _x )₂O₃ was observed in the photoluminescence emission spectra for all deposition temperatures. The increase in photoluminescence emission intensity with increasing postdeposition annealing temperature was attributed to the surface/grain boundary area-reduction effect.     

铁矿微粉低温输送预还原及附碳行为

研究了铁矿微粉低温输送预还原中气固比、还原时间、炉温、矿粉粒径、还原剂种类等参数对矿粉还原率的影响,并运用正交设计和模式识别方法对工艺参数进行了优化,对预还原过程中样品的附碳行为进行了探讨. 结果表明,在矿粉粒径14~20 mm、炉温660~700℃、反应时间180~220 s、还原气成分CO 0~20%(j)的优化条件下,预还原率较高,最高达70.16%. XRD分析表明,还原样品发生碳吸附现象,少量氢气可提高碳吸附率.     

Characterizing herring bone structures in carbon nanofibers using selected area electron diffraction and dark field transmission electron microscopy

The use of selected area electron diffraction and centered dark field imaging using a transmission electron microscope is demonstrated for studying the herringbone structure of carbon nanofibers (CNFs). The experimental method is described and illustrated with CNFs that were grown via a chemical vapor deposition method with a nickel catalyst. It is demonstrated that this method gives the angle of the herringbone with great accuracy and gives insight into the uniformity of graphitic elements in the herringbone structure. It was found that the Ni catalyst could be removed from the fiber-tips by treatment in HNO₃, without affecting the carbon structure. These electron microscopy results were confirmed by XRD. The parameters that can be determined by application of this characterization method are expected to be useful to study and optimize growth conditions for carbon nanofibers grown by chemical vapor deposition.     

甲烷浓度对金刚石薄膜(100)织构生长的影响

以H2和CH4的混合气体为气源,用微波等离子体辅助化学气相沉积法(MPECVD)在1 cm×1 cm S i(100)基体上沉积了金刚石薄膜。研究了不同的甲烷浓度对金刚石薄膜(100)织构生长趋势的影响。分别采用扫描电子显微镜(SEM),Ram an光谱对金刚石膜的表面形貌、质量进行了分析。结果表明,当基体温度为750℃,气压为4.8×103Pa,甲烷浓度为1.4%时,薄膜表面为(100)织构。     

Preparation of nickel-on-active carbon catalyst by CVD method for methanol carbonylation

The nickel on active carbon (Ni/A.C.) catalysts prepared by a simple chemical vapor deposition (CVD) method showed comparable catalytic activities for the vapor phase carbonylation of methanol to those of the catalysts prepared by impregnating A.C. with nickel nitrate and activating by hydrogen treatment. The CVD method was successfully applied to the in situ catalyst preparation.     

Chemistry and kinetics of chemical vapor deposition of pyrocarbon: VI. influence of temperature using methane as a carbon source

The chemical vapor deposition of carbon from methane was investigated at an ambient pressure of about 100 kPa, a methane partial pressure of 10 kPa and temperatures ranging from 1050–1125°C. Carbon deposition rates and compositions of the gas phase as a function of residence time have been determined using a substrate with a surface area/reactor volume ratio of 40 cm⁻¹. Increasing temperatures lead to strongly increasing deposition rates, decreasing partial pressures of ethane and increasing partial pressures of ethene, ethine and benzene. The overall activation energy of carbon deposition, determined from the initial deposition rates at a residence time versus zero amounts to 446 kJ/mol as compared to 431.5, 448 and 452.5 kJ/mol reported in earlier papers. Two possible rate-limiting steps are discussed, namely dissociation of methane, which is favored in the earlier papers, and dissociation of carbon–hydrogen surface complexes.     

Characteristics of nitrogen doped diamond-like carbon thin films grown by microwave surface-wave plasma CVD

Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-type silicon (p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (< 100 °C). For films deposition, argon (Ar: 200 sccm), acetylene (C₂H₂:10 sccm) and nitrogen (N: 5 sccm) were used as carrier, source and doping gases respectively. DLC:N thin films were deposited at 1000 W microwave power where as gas composition pressures were ranged from 110 Pa to 50 Pa. Analytical methods such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, FTIR and Raman spectroscopy were employed to investigate the chemical, optical and structural properties of the DLC:N films respectively. The lowest optical gap of the film was found to be 1.6 eV at 50 Pa gas composition pressure.     

Deposition mechanism of pyrolytic carbons at temperature between 800–1200 °C

The textures, growth features, microstructures and binding of carbon atoms of pyrolytic carbons prepared by chemical vapor deposition (CVD) at a temperature between 800–1200 °C on graphite substrate and carbon fibers were studied. The intermediate product phase of pyrolytic carbons was also investigated. Based on the present study a deposition model of viscous droplet was proposed in this paper. The viscous droplet here refers to all kinds of fine spheroids that are more or less viscous. The mechanism of the formation of three typical textures namely, smooth laminar, rough laminar and isotropic carbons can be satisfactorily explained by this model.