负载型氧电极PtRuIr/TiC催化剂的制备、结构及CV研究

以TiC纳米粉作载体,超声波分散?共还原沉积方法制备以Pt、Ru和Ir为活性组分的负载型催化剂PtRuIr/TiC.BET比表面积、扫描电子显微镜(SEM)、X光衍射(XRD)及循环伏安(CV)等测试表明:该负载型催化剂活性组分Pt、Ru、Ir微晶(组成2.6%Pt,1.3%Ru,16%Ir和80%TiC,by mass)在载体TiC上趋于无定型化结构,主要分散在载体的外表面上,其析氧性能约是相同成分无负载催化剂的3倍,经过120次CV扫描,PtRuIr/TiC在电解质溶液中几乎不溶解.实验证实,这一电极具有良好的电化学催化性能和稳定性.     

An Effective Synthesis of β- Selenium and β- Tellurium Carbonyl Compounds Via Reaction of Diaryldiselenides Or Diarylditellurides with α,β- Unsaturated Carbonyl Compounds Induced by Low-Valent Titanium

P-Selenium and β-tellurium carbonyl compounds have been prepared in good yield by reaction of diaryldiselenides or diarylditelluride with α,β-unsaturated carbonyl compounds induced by TiC1₄ / Sm /THF system under mild reaction conditions.     

稀土对AlTiC细化剂组织及细化效果的影响

应用自蔓延高温合成法制备出含稀土及不含稀土两种AlTiC细化剂. 应用扫描电镜及X射线衍射等手段分析了中间合金及细化剂的成分、组织和形貌. 结果表明: 稀土对反应合成TiC微细颗粒具有重要的促进作用, 添加稀土明显加快反应速度; 在AlTiCRE细化剂中, 由于稀土的作用, 改变了TiAl3和TiC的形态和分布, 减小了TiC的聚集倾向, 细化了TiC颗粒尺寸, 从而增加了形核基底数. AlTiCRE细化晶粒的效果优于AlTiC, 而且稀土还具有明显细化枝晶组织的作用.     

Flux-assisted wetting and spreading of Al on TiC

The effect of a K-Al-F-based flux on the spreading of Al on TiC, at temperatures up to 900 degrees C, in Ar and in air has been studied. Whilst obtuse contact angles were observed without flux, the flux facilitated rapid spreading to a perfect wetting condition, in both Ar and in air. The atmosphere was found to have a weak effect on the spreading kinetics as the liquid flux provides a locally protective atmosphere by spreading over the TiC surface and also on the solid surface of Al. The flux dissolves the aluminium oxide, covering Al, so that when Al melts, and the oxide layer has been removed or weakened, intimate contact occurs between liquid Al and the TiC substrate facilitating spontaneous spreading and instantaneous wetting of liquid Al on TiC. Since flux-assisted spreading is very rapid and occurs without the formation of a reaction layer at the Al/TiC interface, this process is very different to the reactive wetting behaviour previously reported in the Al-TiC system.     

Surface and in-depth characterization of TiC/C and Ti(C,N) layers by means of AES and Factor Analysis

Magnetron sputtered TiC/C multilayers and Plasma Vapour Deposited Ti(C,N) layers have been investigated by AES. The carbon sensivity factor has been calibrated for the correct composition of a TiC standard sample. Nitrogen has been measured indirectly based on the Ti(L3M23M23)/Ti(L3M23V) peak area ratio in the direct E.N(E) spectrum using Ti, TiC and TiN standard samples. The influence of Tougaard background removal has been tested. As the less accurate method taking the Ti peak-to-peak ratio has been found to give adequately good results. It has been possible to recalculate AES depth profiles, where only peak-to-peak values and no peak areas in the direct spectrum are available. Factor Analysis has been applied to AES depth profiling results. The data matrix in each column contains the linked experimental spectra of the measured elements. Based on the standard spectra the main components of a TiN layer on silicon have been identified by Factor Analysis. The structure of a TiC/C multilayer system has been resolved by the characteristic C(KLL) peak shape in C and TiC. Factor Analysis enables to calculate the individual profiles for Ti, TiC and C.     

Surface and in-depth characterization of TiC/C and Ti(C,N) layers by means of AES and Factor Analysis

Magnetron sputtered TiC/C multilayers and Plasma Vapour Deposited Ti(C,N) layers have been investigated by AES. The carbon sensivity factor has been calibrated for the correct composition of a TiC standard sample. Nitrogen has been measured indirectly based on the Ti_L3M23M23/Ti_L3M23V peak area ratio in the direct EN(E) spectrum using Ti, TiC and TiN standard samples. The influence of Tougaard background removal has been tested. As the less accurate method taking the Ti peak-to-peak ratio has been found to give adequately good results. It has been possible to recalculate AES depth profiles, where only peak-to-peak values and no peak areas in the direct spectrum are available. Factor Analysis has been applied to AES depth profiling results. The data matrix in each column contains the linked experimental spectra of the measured elements. Based on the standard spectra the main components of a TiN layer on silicon have been identified by Factor Analysis. The structure of a TiC/C multilayer system has been resolved by the characteristic C_KLL peak shape in C and TiC. Factor Analysis enables to calculate the individual profiles for Ti, TiC and C.     

Studies on the kinetics of synthesis of TiC by calciothermic reduction of TiO<Subscript>2</Subscript> in presence of carbon

Reaction kinetics of the formation of TiC by calciothermic reduction of TiO₂ in presence of carbon have been investigated using thermal analysis (TG-DTA) of a powder mixture of TiO₂, Ca, and C in argon atmosphere at different heating rates. Both the reaction initiation and the peak temperatures are found to increase with heating rates. The appearance of exothermic peaks in the DTA plots after Ca melting indicates the reduction of TiO₂ by liquid calcium and formation of TiC by in-situ reaction of Ti with C. The apparent activation energy of the process has been found to be 170.8±0.5 kJ mol^–1.     

Gas Phase Polymerisation of Ethylene with Supported Titanium-Nickel Catalysts

Olefins gas phase polymerization uses generally supported titanium catalyst systems inindustrial production. The polymerization of olefins with late transition metal catalysthas recently attracted considerable interestl-2. The new catalyst family shares many ofthe advantages of metallocene catalysts in terms of activity and control of polymerproperties and, in addition, the new catalysts yield homopolymer of ethylene with veryhigh branching degrees and branching degree can be controlled.A new …     

The preparation of highly flexible mesoporous TiC/CNF film for flexible dye-sensitized solar cells

Journal of Solid State Electrochemistry - The flexible TiC/carbon nanofiber (TiC/C NF) film was prepared by electrospinning, stabilization, and carbonization. All the obtained TiC/CNFs had rough...     

ARXPS-analysis and morphology of sputtered nanocrystalline TiC/SiC coatings

ARXPS (angle resolved X-ray photoelectron spectroscopy) measurements are used to obtain informations about surfaces and grain boundaries. Data acquired from nanocrystalline carbidic hard coatings have been employed to establish structural models. Magnetron-sputtered coatings of TiC, SiC and TiC/SiC were examined. In such coatings, partly defective TiC nanocrystallites are surrounded by interfacial carbide. This excess carbon shows a binding state similar to that of doped graphite or fullerenes. X-ray amorphous SiC is found in the residue. On top of sputtered SiC coatings, less oxide and graphite is found as compared to TiC/SiC or TiC coatings.     

Ti^＋离子和C2H4分子自旋禁阻反应中C—H键活化机理的理论研究

用密度泛函B3LYP方法,研究了二重态和四重态势能面自旋禁阻反应Ti^＋（^4F,3d^24s^1）＋C2H4→TiC2H2^＋（^2A2）＋H2的微观机理．通过自旋．轨道耦合的计算讨论了势能面交叉点和可能的自旋翻转过程．中间体IM1-^4B2处,四重态和二重态间的旋-轨耦合值为59．3cm^-1．自旋多重度必将发生变化,从四重态系间穿越到二重态势能面形成共价型复合物IM1-^2A1,同时导致四重态势能面的势垒明显降低．到插入中间体IM2后,二重态势能面上有两条不同的反应路径,即分步和协同路径,后者在二重态势能面上得到放热产物TiC2H2^＋（^2A2）＋H2具有较低的活化势垒,4．52kcal／mol,其主反应路径为：Ti^＋＋C2H4→^4IC→IM1—^4B2→4.2ISC→IM1—^2A1→[^2TSins]→IM2-^2A”→[^2TSMCTS]→IM5→TiC2H2^＋（^2A2）＋H2．     

A constitutional diagram of the system TiC−HfC−WC

The system TiC?HfC?WC was investigated by means of melting point, differential thermoanalytical, X-ray diffraction and metallographic techniques on hot pressed and heat treated as well as melted alloy specimens and a complete constitutional diagram from 1500°C through the melting range established. According to the peritectic melting of hexagonal WC both isopleths, TiC?WC as well as HfC?WC show a class II reaction at 2760°C in Ti?W?C and at 2730°C in Hf?W?C. The phase behaviour within the TiC?HfC?WC system is characterized by the presence of a (binary) miscibility gap within TiC?HfC [T _c=1780°C, (TiC)_0.55(HfC)_0.45] which extends into the ternary forming a closed ternary miscibility gap at higher temperatures with an isolated ternary critical point:T _c=1800°C, (TiC)_0.55(HfC)_0.45(WC)_0.05. Interaction of the solvus (boundary of the cubic-B 1 monocarbide solid solution) and the ternary miscibility gap was established at 1540°C and (TiC)_0.27(HfC)_0.41(WC)_0.32: Alloys of this composition enter a decomposition reaction on cooling into two isotypic cubic B 1 phases and hexagonal WC. Isothermal sections were calculated assuming regular solutions.     

Solvent free reactions

Reactions of nitrophenols have been studied in the eutectic melt of 8-hydroxyquinoline–benzoic acid, where it reacted with 8-hydroxyquinoline. The reactions were also carried out in solution. The reaction products obtained from both the methods were characterized by FT-IR, differential scanning calorimetry, X-ray diffraction technique and microstructural investigations. The reaction products obtained from eutectic melt were analyzed for C, H, N. The results showed that reaction products obtained from both the methods are same. An attempt has been made to propose the overall mechanism of the reaction in the eutectic melt.     

Synthesis and characterization of silicon nanowires on mesophase carbon microbead substrates by chemical vapor deposition

Silicon nanowires (SiNWs) have been fabricated by chemical vapor deposition at ambient pressure using SiCl(4) as a silicon source and mesophase carbon microbead powder as a substrate without any templates and/or metal catalysts. The SiNWs have a crystalline core with a very thin amorphous SiO(x) sheath. The obtained SiNWs are homogeneous with average diameters below 50 nm and lengths up to micrometers. Temperature and time effects on the growth of SiNWs were systematically studied. Higher reaction temperatures and longer reaction times resulted in larger diameters and higher yields of SiNWs. SiNWs with a better crystallinity can be obtained at higher temperatures and longer reaction times. The obtained SiNWs were characterized by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy.     

Activation of noble metals on metal-carbide surfaces: novel catalysts for CO oxidation, desulfurization and hydrogenation reactions

This perspective article focuses on the physical and chemical properties of highly active catalysts for CO oxidation, desulfurization and hydrogenation reactions generated by depositing noble metals on metal-carbide surfaces. To rationalize structure-reactivity relationships for these novel catalysts, well-defined systems are required. High-resolution photoemission, scanning tunneling microscopy (STM) and first-principles periodic density-functional (DF) calculations have been used to study the interaction of metals of Groups 9, 10 and 11 with MC(001) (M = Ti, Zr, V, Mo) surfaces. DF calculations give adsorption energies that range from 2 eV (Cu, Ag, Au) to 6 eV (Co, Rh, Ir). STM images show that Au, Cu, Ni and Pt grow on the carbide substrates forming two-dimensional islands at very low coverage, and three-dimensional islands at medium and large coverages. In many systems, the results of DF calculations point to the preferential formation of admetal-C bonds with significant electronic perturbations in the admetal. TiC(001) and ZrC(001) transfer some electron density to the admetals facilitating bonding of the adatom with electron-acceptor molecules (CO, O(2), C(2)H(4), SO(2), thiophene, etc.). For example, the Cu/TiC(001) and Au/TiC(001) systems are able to cleave both S-O bonds of SO(2) at a temperature as low as 150 K, displaying a reactivity much larger than that of TiC(001) or extended surfaces of bulk copper and gold. At temperatures below 200 K, Au/TiC is able to dissociate O(2) and perform the 2CO + O(2)→ 2CO(2) reaction. Furthermore, in spite of the very poor hydrodesulfurization performance of TiC(001) or Au(111), a Au/TiC(001) surface displays an activity for the hydrodesulfurization of thiophene higher than that of conventional Ni/MoS(x) catalysts. In general, the Au/TiC system is more chemically active than systems generated by depositing Au nanoparticles on oxide surfaces. Thus, metal carbides are excellent supports for enhancing the chemical reactivity of noble metals.     

A theoretical study of the TiC5 cluster

The geometric and electronic properties of the titanium carbide TiC(5) cluster in its neutral and anionic charge states have been investigated using density functional theory (DFT) at the B3LYP level. The nonplanar six-membered ring-type or "butterflylike" structures are found to be the equilibrium geometric structures of TiC(5) and TiC(5) (-). Time-dependent DFT is used in the calculation of the excited states. The theoretical assignment at the B3LYP level for the features in the photoelectron spectrum is given. All results obtained are in good agreement with the available experimental data.     

Growth of TiC films by Pulsed Laser Evaporation (PLE) and characterization by XPS and AES

Summary Thin films of TiC with a thickness of some 100 nm have been grown on Si(100) substrates by Pulsed Laser Evaporation (PLE). Advantages of PLE in comparison with more conventional growth methods e. g. PVD or CVD are reported. The feasibility of growing stoichiometric thin films of TiC by PLE was investigated. These films produced have been analysed in situ by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). XPS results and Auger sputter depth profiles indicate that the films grown between RT and 500°C are stoichiometric TiC. Film/substrate interdiffusion is observed at 600°C substrate temperature and higher.     

Kupfer(II)-Komplexe von N-Benzoyl-O-methyl-N′-phenyl-isoharnstoffen

Copper(II) Complexes of N-Benzoyl-O-methyl-N′-phenyl-isoureas By reaction of N-benzoyl-N′-(p-nitro/p-bromphenyl)thioureas with copper(II)acetate-monohydrate in methanole insoluble copper(I)precipitates have been obtained, from which filtrates bis[N-benzoyl-O-methyl-N′-(p-nitrophenyl)-isoureato]copper(II) 1 and bis[N-benzoyl-O-methyl-(p-bromphenyl)-isoureato]copper(II) 2 were isolated. The moleculare structure of 1 with planar trans coordination has been determined by single crystal X-ray diffraction methods. The N-benzoyl-O-methyl- N′-(o-nitrophenyl)-isourea 3 and N-benzoyl-O-methyl-N′-(p-bromphenyl)-isourea 4 have been prepared by reaction of the corresponding N-benzoyl-N′-phenyl-thioureas with mercury(II)acetate in methanolic solution. The molecular structure of 3 has been determined by single crystal X-ray diffraction methods. The NH-tautomeric form is stabilized by a bifurcated intramolecular hydrogen bond to an oxygen atom of the o-nitro group and the benzoyl oxygen atom. XPS, NMR and mass-spectrometric investigations also confirm the structures.     

TiC nanocrystal formation from carburization of laser-grown Ti/O/C nanopowders for nanostructured ceramics

Refractory carbide ceramics (TiC and ZrC) raise interest as promising materials for high-temperature applications such as structural materials for the future generation of nuclear reactors. In this context, nanostructured ceramics are expected to exhibit improved thermomechanical properties as well as better behavior under irradiation when compared to conventional materials. It is therefore necessary to synthesize carbide nanocrystals of such materials to elaborate the ceramics. We report here the formation study of TiC nanocrystals through the direct carburization of Ti/O/C nanopowders grown by laser pyrolysis. A spray of titanium tetraisopropoxide was laser pyrolyzed with ethylene as the sensitizer, leading to Ti/O/C nanopowders with various C contents controlled by the synthesis conditions. Annealing treatments performed on these nanopowders under an inert atmosphere without any C addition enabled the formation of TiC grains through the carburization of the oxide phase by free C incorporated during the synthesis. The powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The final TiC grain size was about 80 nm, and the grains were monocrystalline. The influence of the free C content on the grain growth during the annealing step, together with its effects on the densification of the ceramics after sintering by high-pressure flash sintering, was examined. A 93% densification was finally achieved.     

TiN和TiC涂层对碳氢燃料裂解结焦的影响

采用化学气相沉积(CVD)法,在304型不锈钢管道内壁分别沉积了TiN和TiC涂层,并采用SEM、EDS、金相显微镜和热冲击等方法对其进行了性能表征和测试。结果表明,两种涂层均匀致密,TiN涂层厚度为7.24μm,TiC涂层为11.52μm,且均具有良好的结合强度。为评价涂层抑制结焦效果,选用某碳氢燃料A,采取程序升温法进行超临界裂解实验,当反应管前后压差超过1 MPa时停止实验,结果表明,304空白管由于严重结焦,在650℃只运行了180 s;而TiC和TiN涂层管分别在780℃运行了275和1560 s。通过压差、产气组成和积炭微观形貌的综合分析表明,TiN、TiC涂层均呈现出优良的抑焦效果,且TiN涂层抑焦效果更优。