Comparison of Properties of Carbon Particles Formed by Pyrolysis of C3O2 and C2H2 behind Shock Waves

Various carbon particles formed by the pyrolysis of C₃O₂ and C₂H₂ behind shock waves in the temperature range 1200–3800 K are studied. The formation of the condensed carbon particles is observed directly by the multichannel detection of the time profiles of the extinction of the medium in the UV, visible, and near-IR spectral regions. The samples of carbon material deposited on the walls of a shock tube after an experiment are analyzed using transmission electron microscopy with different resolutions and electron microdiffraction. Particles formed from C₃O₂ and C₂H₂ at 1500–2000 K are 10–30 nm in size and look like usual soot. The absence of molecular hydrogen in C₃O₂ only results in faster formation and graphitization. At 2100–2600 K, the formation of particles is retarded, and the yield of the carbon particles decreases for both substances. After experiments on pyrolysis of C₃O₂ at these temperatures, giant spherical particles up to 700 nm in size are found on the walls of the shock tube. Carbon particles formed at the highest temperatures (2700–3200 K) in C₃O₂ pyrolysis have the high degree of crystallinity of particles.     

碳前驱体CH3ArCH2NH2的热解性能及动力学研究

通过密闭压力容器法、常压DSC、高压DSC及紫外分光光度定量分析法等实验手段,对液相沉积法制碳／碳复合材料用碳前驱体CH3ArCH2NH2的热裂解行为进行了研究,获得不同温度、不同压力下该碳前驱体的热分解温度和残碳率,用等温动力学和非等温动力学方法获得了热裂解反应的表观活化能,实验结果表明,常压热裂解温度大约为530．15－556．55K,1－3MPa的高压范围内的热裂解温度大约在618．34－675．49K,密闭压力容器中的残碳率为56．23％,常压下的残碳率为28．96％－36．47％,而高压下残碳率可达59．11％,根据基辛格等方法获得了等温条件下和非等温条件下热裂解反应的表观活化能Ea分别为206．78kJ/mol和183．93kJ/mol, 反应级数N~1.     

Kinetics of Structure Formation of YBa2Cu3O7-y

The kinetics of the synthesis of YBa₂Cu₃O_7-y (YBCO) was studied in situ on an X-ray diffractometer using the time vs temperature dependences of the concentration of the phase. The highest rate of YBCO synthesis was observed at 750-780°C. The effective activation energy was minimal at 700°C, E _a = 20-30 kJ/mole. The structural nonhomogeneity parameters and the dimensions of coherent scattering regions were determined for the YBCO product.     

碳前驱体CH3ArCH2NH2热解反应的热力学和动力学DFT研究

在实验研究基础上 ,通过量子化学理论计算对碳前驱体 CH3 Ar CH2 NH2 的热裂解机理作了进一步的研究 .利用 Gaussian98程序包中 AM1方法及 DFT UB3 LYP/3 -2 1 G*方法 ,对化合物 5种可能热裂解路径的热力学和动力学计算结果表明 ,CH3 Ar CH2 NH2 热裂解的主反应路径为生成自由基 CH3 Ar CH2 ·和 NH2 · ,其主反应路径 AM1计算的活化能 Ea=2 3 0 .78k J/mol,DFT计算的活化能 Ea=3 2 1 .1 8k J/mol;比较键焓计算的数据与相应的实验数据 ,发现 DFT计算结果与实验结果吻合得较好 ;通过分析优化的反应物及产物自由基的部分结构参数 ,了解了理论支持主反应的原因 ;计算的产物自由基的空间构型表明主反应路径生成的产物自由基相互间若进行稠环缩合反应 ,将获得分子平面取向性很好的稠环芳烃产物     

Cu/La2O3 催化裂解乙炔制备碳纳米纤维

用沉淀法制备了Cu/La2O3催化剂,将其用于催化裂解乙炔制备了碳纳米纤维(CNFs).考察了反应温度和反应时间对CNFs产率的影响.用SEM和微机差热天平分别对CNFs的形貌和抗氧化性能进行了研究.实验结果表明:于650 ℃反应3 h, CNFs产率为1.4 g·(g Cat.)-1;CNFs形态规则,表面光滑,直径300 nm～700 nm,长度达几十微米;CNFs燃烧温度515 ℃～544 ℃.     

催化裂解C2H2制备空心碳球

在高岭土负载的镍催化剂上,于850 ℃催化裂解乙炔制备了直径约500 nm 的空心碳球.用XRD、TEM、SEM和显微激光Raman光谱对所得的碳球及催化剂进行了表征,并初步探讨了反应机理.     

On the gas-phase reaction of C3O2+. with C3O2

The gas-phase, ion molecule reaction between C₃O₂^+. and C₃O₂ has been studied by both double-focusing and ion trap mass spectrometry, rationalized by the formation of a dimeric, odd electron cation [C₆O₄]^+. which decomposes extensively through sequential CO losses giving rise to [C₅O₃]^+. and [C₄O₂]^+. ions. The thermodynamics of this process have been investigated by means of ab initio calculation performed on the above species using different basis sets (STO-3G, 3-21G and 6-31G^*).     

The Structure of Carbon Suboxide,C3O2, in the Solid State

Carbon suboxide, C₃O₂, is crystallized from the melt. According to the X‐ray structure determination the crystal contains two non‐crystallographically equivalent molecules in the asymmetric unit: a = 986.9(2), b = 1206.0(2), c = 516.0(1) pm, space group Pnma. Both molecules are linear. A close inspection of the vibrational amplitudes indicates some systematic deviations from linearity.     

Theoretical Study on the Pyrolysis Mechanism and Kinetics of 3-Hydroxy-3-Methyl-2-Butanone

Thethermolysisofpyruvicacid2Ieadstotheeliminationofcarbondioxideandacetaldehydeisformedasanotherproduct.Hong'hasstudiedthemechanismofthereactionintheMINDO/3molecularorbitaltheory.Al-AwadiandEL-Dusouqui'havestudiedthepyrolysisofthe3-hydroxy-3-methyl-2-butanoneinordertoexaminetheinfluenceofthehydrogenatominvolvedintheTransitionStateoftheeliminationprocessandtoassessitscontributiontotherate-controllingstep.TheygaveoutthethermalrateconstantsandhypothesizedthatthereactionmightproceedthroughafO…     

模糊聚类分析评价炭纤维裂解色谱图重现性

利用模糊聚类分析评价了炭纤维表面裂解色谱图的重现性。结果表明,模糊聚类分析可以综合评价谱图重现性,从而为定量计算中谱图的选取提供依据。     

CnD-m簇离子的结构特性和形成动力学研究

对较小碳原子簇负离子Ｃ－ｎ结构的研究是从直链向单环乃至双环构型发展的．氢原子在碳原子簇中起着电子给予体的作用［１,２］．但以往的研究未发现碳原子数的奇偶性和氢原子数目对簇离子构型的影响．我们以激光溅射氘代蒽样品,产生了丰富的碳／氢团簇负离子ＣｎＤ－ｍ...     

Formation of solid phases in the ZrO2-SO3-KF-H2O system at 20°C

Conclusions Various fluorosulfatozirconates and fluorozirconates were crystallized, some for the first time, from solutions of the ZrO₂-SO₃-H₂O system upon the introduction of KF.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 967–972, May, 1982.     

Formation of Carbon Filaments from 1,3-Butadiene on Fe/Al2O3 Catalysts

The formation of carbon filaments with different crystallographic and morphological characteristics in the course of 1,3-butadiene decomposition on Fe/Al₂O₃ catalysts at low (500–600°C) and high (700–800°C) temperatures was considered in terms of a carbide cycle mechanism. The conditions of formation and decomposition of an iron carbide phase in the course of formation of graphite nanotubes in the low-temperature region were studied.     

Kinetics of the thermal decomposition of [Co(NH3)6]2(C2O4)3·4H2O

The thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O was studied under isothermal conditions in flowing air and argon. Dissociation of the above complex occurs in three stages. The kinetics of the particular stages thermal decomposition have been evaluated. The R_N and/or A_M models were selected as those best fitting the experimental TG curves. The activation energies,E, and lnA were calculated with a conventional procedure and by a new method suggested by Kogaet al. [10, 11]. Comparison of the results have showed that the Arrhenius parameters values estimated by the use of both methods are very close. The calculated activation energies were in air: 96 kJ mol^–1 (R_1.575, stage I); 101 kJ mol^–1 (Ain1.725 stage II); 185 kJ mol^–1 (A _2.9, stage III) and in argon: 66 kJ mol^–1 (A _1.25, stage I); 87 kJ mol^–1 (A _1.825, stage II); 133 kJ mol^–1 (A _2.525, stage III).     

Kinetics of Ruddlesden-Popper Phase Formation: III. Mechanism of Gd2SrAl2O7 Formation

Studies on phase formation in the system Gd₂O₃-SrO-Al₂O₃ in the range 900-1530°C showed that the synthesis of Gd₂SrAl₂O₇ occur by a mechanism differing from the mechanism of Ln₂SrAl₂O₇ formation (Ln = La, Nd, Sm), and the limiting stage is reaction between Gd₂O₃ and SrAl₂O₄.     

碳前驱体CH3ArCH2NH2的热解性能及动力学研究

通过密闭压力容器法、常压DSC、高压DSC及紫外分光光度定量分析法等实验手段，对液相沉积法制碳/碳复合材料用碳前驱体CH     

Kinetics of Ruddlesden-Popper Phase Formation: II. Mechanism of Nd2SrAl2O7 and Sm2SrAl2O7 Formation

Phase formation in the Ln₂O₃-SrO-Al₂O₃ system (Ln = Nd, Sm) was studied in the range 900-1530°C. Comparative examination of the kinetics of the synthesis of Ln₂SrAl₂O₇ oxides (Ln = La, Nd, Sm) showed that this reaction proceeds by a common mechanism and is substantially faster for neodymium and samarium complex aluminates than for lanthanum aluminate.     

Ca-Tb4O7-Fe体系中生成TbFe2的动力学研究

高纯TbFe2 可以作为生产 (TbDy)Fe2 的一种中间合金原料。开发低成本、无污染、直接从氧化铽还原制备高纯TbFe2 的方法具有非常重要的实际意义。本文在已有关于Ca Tb4O7 Fe体系 ,还原扩散法制备TbFe2 合金在热力学上可能的基础上 ,进一步研究了其动力学可行性。XRD物相鉴定证明生成物是TbFe2 ;应用收缩核模型得知 :扩散是反应的控制步骤 ,表观活化能Ea=39kJ·mol- 1 。