Thermopower and transport properties of AsF5-doped polyacetylene

Measurements of thermoelectric power versus temperature of (CH)_x doped with various concentrations of AsF₅ are reported. These reflect the semiconductor-metal transition at ～ 1% doping. The “pristine” thermopower is consistent with the conductivity-derived activation energy of 0.35 eV, and a residual defect/impurity carrier concentration of 0.1%. An analysis of the conductivity based on these data indicates that, while the disorder is certainly important, it is not the cause of the transition.     

Mo的掺杂方式对TiO2光催化活性的影响

通过溶胶凝胶法制备了以不同方式和不同浓度掺Mo的TiO2薄膜.通过X射线衍射(XRD)、UV-VIS透射光谱、电化学阻抗谱分析了Mo对TiO2薄膜晶粒结构、光吸收性能、阻抗的影响.甲基橙光催化降解实验表明,钼的最佳掺杂方式为在薄膜底层掺杂,在表层及体相掺杂的效果均比未掺杂的TiO2差;其中以Mo的摩尔分数为1.0%、在薄膜底层掺杂时TiO2薄膜的光催化活性最佳.并从载流子分离效率方面讨论了掺杂方式及掺杂浓度对光催化活性的影响.     

Electrical properties and spectroscopic studies of HClO4-doped poly(p-diethynylbenzene)

Electrical properties of poly(p-diethynylbenzene) (PDEB), chemically doped with perchloric acid (HClO₄), were investigated as a function of dopant concentration and relative humidity. The doped polymer was characterized by X-ray photoelectron spectroscopy (XPS), UV—Vis, IR, electron spin resonance (ESR) and scanning electron microscopy (SEM). A possible structure of the HClO₄-doped PDEB was proposed on the basis of spectroscopic studies. In the presence of humidity, HClO₄-doped PDEB follows the proton conduction mechanism.     

Photoelectron spectroscopy of [CH(AsF5)0.1]x

We have studied pure and various stages of AsF₅-doped polyacetylenes by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), as well as X-ray-induced Auger electron spectroscopy (XAES). Spectra on the doped polymers are analyzed by comparison with corresponding spectra on the model molecules AsF₃ and AsF₅ in both the gaseous and condensed phases. The chemical composition of the dopant species can be addressed by interpretation of spectra on the basis of escape depths of the photoelectrons. The degree charge transfer from the host polymer to the dopant molecules results from an analysis of the chemical shifts of the C(1s) spectra of the doped polymers.     

Chemical structure and mechanical properties of Si-containing a-C:H and a-C thin films and their Cr- and W-containing derivatives

Si-containing a-C:H and a-C thin films with nitrogen, oxygen and transition metal (Cr and W) additives were deposited on polished single crystalline silicon substrates at room temperature by plasma activated CVD, magnetron-sputtering PVD and also by combined PACVD-PVD techniques.In particular Si-, Si-O- and Si-N-containing a-C:H films (denoted as a-C-Si, a-C-Si-O and a-C-Si-N) were deposited respectively from tetramethylsilane (TMS), hexamethyldisiloxane and hexamethyldisilazane vapourised precursors in He carrier gas by electron cyclotron wave resonance RF plasma. Cr-containing a-C:H films, further denoted as a-C-Si-Cr, were deposited with combined PVD-PACVD by sputtering chromium and carbon targets in argon and introducing TMS vapour. Wcontaining a-C films (denoted as a-C-Si-W) were deposited by PVD with simultaneous sputtering of the constituents in Ar. Detailed characterisation of the composition and chemical state of the elements present in the films were done by X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy. Mechanical properties, hardness (H), reduced modulus (E) and scratch behaviour were studied by depth-sensing nanoindentation and scratch tests.In the a-C:H films, the C/Si ratio varied between 1.5 and 3.5 showing a significant deficiency of C as compared to the composition of the precursors. The Cr and W content in the a-C-Si-Cr and a-C-Si-W films varied in a very broad 2-50 at.% range.The chemical state of carbon was primarily of sp² and partly of sp³ type C-C with XPS chemical shifts for C 1s at 284.3 eV and 285.0 eV, respectively. The Si in the films is bonded predominantly to carbon (Si 2p at 100.8 eV BE) or to nitrogen in N-containing films (Si 2p at 101.3 eV BE). In the a-C-Si-Cr films Cr-C bonding states were determined (Cr 2p_3/2 at 574.5 eV and C 1s at 282.8 eV). Si formed predominantly Si-C and also Si-Cr bonds. In the a-C-Si-W, films C-Si and C-W (W 4f_7/2 at 32.3 eV) chemical bonds could be identified.It was discovered that the modified Auger parameter for silicon, α_Si (derived from the Si 2p electron and Si KLL Auger line energy), sensitively reflects the entire chemical structure of these films, including crosslinking and densification. These spectroscopic data, supported further by the increase of the bulk plasmon loss energy of the C 1s peak, were directly connected with the mechanical properties of these films. The amorphous nature of the films was deduced from the chemical state analysis and was verified also by transmission electron microscopy (TEM) and electron diffraction (ED) studies.Hardness and elastic modulus of the a-C-Si-(O,N) films could be adjusted in a wide range of approx. 5-15 GPa and 40-140 GPa, respectively. Systematic alteration of these values with the composition (C/Si, O/Si and N/Si atomic ratio) and with the chemical structure (α_Si?) was established and their interrelations are discussed. Whilst incorporation of Cr does not alter the mechanical properties, the addition of W increases H and E up to 19 GPa and 210 GPa, respectively.     

Electrically conducting poly[3-(ω-hydroxyalkyl)thiophenes]

A series of poly[3-(ω-hydroxyalkyl)thiophenes] was synthesized by chemical oxidative polymerization using FeCl₃ and characterized by FT-IR, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Upon doping with iodine the polymers attained electrical conductivities of between 0.5 and 38 S cm⁻¹. Electrical conductivities of doped samples were found to increase with alkyl chain lengths, being optimum for the octyl pendant moiety. Thereafter, the conductivity decreased, as the doping and dedoping for the polymers became more difficult. Increasing the hydrocarbon chain length of the pendant substituent also resulted in decreased thermal stability of the polymers. XPS results showed that some C–OH groups in the polymers were oxidized to CO in the polymerization process.     

XPS studies of MoS2 formation from ammonium tetrathiomolybdate solutions

Preparation of MoS₂ by acidification of ammonium tetrathiomolybdate solution has been studied by X-ray photoelectron spectroscopy (XPS). The precipitates formed from the solution are mainly composed of MoS₃, the Mo 3d chemical shift of which is approximately 4.2eV. Heat treatments of the above product at 450 and 850°C, in a vacuum of 1.33 × 10⁻⁴ Pa, lead largely to formation of MoS₂, with typical chemical shifts of abouth 1.2eV. The MoS₂ formed consists of nano-sized, crystalline particles of hexagonal (2H-type) structure. The validity of MoS₂ formation by this route is confirmed by comparative study, namely the decomposition of ATT solids under the same respective heat treatment conditions. Apart from these main aspects, origins of minor XPS peaks are also considered.     

Formation of MoSi2 and Al doped MoSi2 coatings on molybdenum base TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy

Formation of aluminium (Al) doped molybdenum di-silicide (MoSi₂) coatings was studied to improve the high temperature oxidation behavior of TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy. The pack composition of the halide activated pack cementation process was successfully optimized to form silicide and Al doped silicide coatings on the TZM alloy substrates. Mo(Si, Al)₂ phase was found to form at the outer layer of the coating prepared by doping Al in MoSi₂. A change in composition of the phases with increase in coating temperature was detected with Al doping, whereas un-doped silicide coating process was dominated by the formation and growth of MoSi₂ phase. Oxidation test and the characterization studies using SEM, EDS, XRD, and micro-hardness measurements indicated the improved performance of Al doped silicide coating during high temperature oxidation in dry air due to the formation of the protective alumina scale.     

LiFePO4/C via fluoride doping

Non-stoichiometric compound fluoride-doped LiFePO4/C cathode materials were synthesized via solid-state reaction using MgF2 and AlF3 as dopant. The fluoride-doped LiFePO4/C samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical testing. The results show that the materials are well crystallized and fluoride doping cannot change the space structure of LiFePO4. Slight amounts of Fe2O3 with no fluoride impurity were ...     

The study of electrical and magnetic properties of LiPF6 doped polyaniline

The results of temperature dependent dc conductivity, EPR magnetic susceptibility, and X-ray photoelectron spectroscopy experiments (XPS) are reported for polyaniline (PAN) doped with lithium hexafluorophosphate (LiPF₆), PAN-LiPF₆. DC conductivity (σ_dc) and its temperature dependence of PAN-LiPF₆ samples vary with the average molecular weight (Mw) of polyaniline used and the composition of doping solution. The EPR linewidth and Pauli susceptibility (χ^P) depend on the Mw of PAN used. The σ_dc and the χ^P of the intermediate Mw PAN-LiPF₆ samples are higher than those of the low Mw PAN samples, indicating more highly conducting state of the intermediate Mw PAN samples. Based on the results of XPS and EPR experiments, some portions of quinoid rings in emeraldine base form of PAN are transformed into benzenoid rings through LiPF₆ doping process, indicating the formation of polarons. However, the existence of some portions of quinoid rings in PAN-LiPF₆ samples after doping suggests an inhomogeneous doping or a pseudo doping.     

Electronic properties and structure of stage-4 MoCl5 GICs prepared from highly crystallized graphite films

Films of stage-4 MoCl₅ graphite intercalation compound (GIC) were synthesized from laboratory-prepared high-quality graphite films and their electronic properties such as electrical conductivity, Hall coefficient and transverse magnetoresistance were measured at 300, 77 and 1.3 K. The graphite films were prepared from polyimide films of Kapton (25 μm thick) and pyromellitic dianhydride-p-phenylenediamine-3,3′,4,4′-tetraaminobiphenyl (PMDA-PPD-TAB, molar ratio 100/92/4, hereafter called PPT) (45 μm thick) by heating them up to 3200 °C. The stage-4 MoCl₅ GICs were made by heating the graphite films in a glass tube with a mixture of natural graphite flakes and MoCl₅ powder at 450 °C for 7 days. Majority carriers in GICs were holes, the density of which was estimated to be about 5.2 × 10²⁶ m⁻³ at 1.3 K. A Shubnikov-de Haas oscillation with a period of 7.84 × 10⁻³ T⁻¹ and slight modulation of the amplitude was observed in the dependence of the transverse magnetoresistance on magnetic field at 1.3 K for both GIC films. The electronic and structural parameters suggested that the GIC film from a polyimide PPT has less perfect crystallinity than that from a polyimide Kapton, even though the pristine graphite film from PPT has better crystallinity.     

热喷涂法制备的La3+掺杂纳米TiO2粉末的表征

采用等离子热喷涂法以钛酸四丁酯为主要原料制备出稀土离子掺杂的纳米TiO2光催化剂.通过XRD,XPS,TEM,UV-Vis等检测手段对样品进行表征,同时检测了其光催化性能,并分析了掺杂对TiO2的影响机理.结果表明,所制备的La3 掺杂纳米TiO2是锐钛矿相和金红石相混晶结构,粒径分布在10～50nm之间;La3 掺杂能够促进锐钛矿向金红石的转变,同时抑制TiO2晶粒的长大;La3 掺杂使TiO2紫外-可见吸收光谱发生红移;适量La3 掺杂能显著提高TiO2的光催化活性,最佳掺杂浓度为0.5%(与Ti原子摩尔比),甲基橙降解率在90min内可达到82.4%.比纯TiO2高出13.2%.     

Microstructure and tensile properties of Mo alloy synthetically strengthened by nano-Y2O3 and nano-CeO2简

Nano-Y2 O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid–solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo–0.3Y, Mo–0.3Ce, and Mo–0.15Y–0.15Ce were prepared through reduction, isostatic pressing, sintering, and drawing. Tensile properties, second phase microstructure and fracture surface appearance of wires were analyzed. The better refining effect for Mo alloy powder can be gotten after two kinds of nanoparticle oxide doped into MoO2 than only one doped. Nano-Y2 O3 and nano-CeO2 have different influences on sintering process. For nano-CeO2, the constraining effect of grain growth focuses on the initial sintering stage, nanoY2 O3 plays refining grains roles in the later densification stage. Nano-Y2 O3 is undistorted and keeps intact in the process of drawing; and nano-CeO2 is elongated and broken into parts in the drawing direction. The strengthening effect of nano-Y2 O3 and nano-CeO2 keeps the finer grains and superior tensile properties for Mo–0.15Y–0.15Ce wire.     

碱钨青铜粉体的溶胶-凝胶法合成与表征

采用溶胶-凝胶法合成了碱钨青铜(M_xWO_3,M=Cs,Rb中的1种或2种)粉体,探究了铯、铷分别单掺杂和铯、铷共掺杂对钨青铜粉体晶相、形貌的影响。利用X射线衍射仪(XRD)、X射线能谱仪(EDS)、扫描电子显微镜(SEM)、X射线光电子能谱仪(XPS)、紫外可见近红外光谱(UV-Vis-NIR)、隔热膜温度测试仪对所合成碱钨青铜粉体的物相、形貌、光学性能和隔热性能进行了表征。结果表明:溶胶-凝胶法所合成的碱钨青铜粉体结晶性较好、粒径较小;Cs、Rb共掺杂的透明绝热指数K=157.34比Rb单掺杂提高了23.92,改善了Cs单掺杂在1076 nm处透过率突变的情况;Cs、Rb共掺杂的温差(与起始温度相比)为4.9℃,比Rb单掺杂的温差下降了5.7℃。     

New synthetic routes to poly (isothianaphthene) I. Reaction of phthalic anhydride and phthalide with phosphorus pentasulfide

A new route for the formation of the low bandgap polymer poly(isothianaphthene) is presented. The route comprises the reaction of phthalic anhydride or phthalide with phosphorus pentasulfide at elevated temperatures (T ⩾ 120 °C), and leads to the formation of poly(isothianaphthene) in one single step. The product obtained was analysed by elemental analysis, IR, Raman and solid state NMR spectroscopy. Chemical doping and dedoping of the material were investigated, and the maximum conductivity obtained was 10 S cm⁻¹ by doping with NOSbF₆. Both doped and undoped samples of poly(isothianaphthene) prepared by this new route were thermally very stable in air or in an inert helium atmosphere as shown by thermogravimetric analysis. Furthermore, the conductivity of a doped sample remained unchanged up to 250 °C in air. Preliminary results showed that the reaction with phosphorus pentasulfide can also be used to obtain nitrogen analogues of poly(isothianaphthene).     

Influence of indium doping on the properties of spray deposited CdS0.2Se0.8 thin films

Polycrystalline indium doped CdS_0.2Se_0.8 thin films with varying concentrations of indium have been prepared by spray pyrolysis at 300 °C. The as deposited films have been characterized by XRD, AFM, EDAX, optical and electrical resistivity measurement techniques. The XRD patterns show that the films are polycrystalline with hexagonal crystal structure irrespective of indium doping concentration. AFM studies reveal that the RMS surface roughness of film decreases from 34.68 to 17.76 with increase in indium doping concentration up to 0.15 mol% in CdS_0.2Se_0.8 thin films and further it increases for higher indium doping concentrations. Traces of indium in CdS_0.2Se_0.8 thin films have been observed from EDAX studies. The optical band gap energy of CdS_0.2Se_0.8 thin film is found to decrease from 1.91 eV to 1.67 eV with indium doping up to 0.15 mol% and increase after 0.15 mol%. The electrical resistivity measurement shows that the films are semiconducting with minimum resistivity of 3.71 × 10⁴ Ω cm observed at 0.15 mol% indium doping. Thermoelectric power measurements show that films exhibit n-type conductivity.     

Improvement of cyclic oxidation resistance of a NiAl-based alloy modified by Dy

The effect of the rare-earth-element dysprosium on the cyclic oxidation behavior of NiAl-31Cr-3Mo alloy at 1300 and 1400 K in static air atmosphere was investigated in this paper. The results revealed that doping 0.1.% atom fraction of Dy greatly improved the cyclic oxidation resistance at 1300 and 1400 K. The microstructure and composition of the oxidation layer were studied by means of X-ray diffractometer (XRD), scanning electron microscopy (SEM) with EDAX unit. The oxidation scale, which is located on the surface of NiAl-31Cr-3Mo alloy, mainly consisted of α-Al₂O₃ and a little Cr₂O₃. While the continuous and sole α-Al₂O₃ scale formed on the surface of the alloys doped with the dysprosium. The adherency of scale improved due to a Cr-rich phase decreased the internal stress by thermal cycling and transformation of Al₂O₃ or transverse growing induced for the testing alloy modified by Dy. The oxidation mechanism was discussed from phase constitution.     

Electrical properties of Cu(II)-N,N′-dimethyldithiooxamide polymers

Cu(II)-dithiooxamide polymers were prepared by a direct deprotonation of the ligand with a Cu(II) salt. The polymers had a chain length of about 13 units. The undoped polymers showed low electrical conductivity with an Arrhenius-type temperature dependence. Doping of Cu(II)-N,N′-dimethyldithiooxamide was performed by iodine in the vapour phase and by FeCl₃ in solution. In both cases, the oxidative doping resulted in highly increased conductivities. A thermopower measurement indicated p-type conduction. The infrared spectra of the undoped material and the one doped with FeCl₃ were completely identical, indicating that charge transfer from the ligand to the dopant is small. The conductivity curves of the doped polymer did not show an Arrhenius-type behaviour. In order to find an explanation for the conduction mechanism different models were tested. The best fit of the experimental conductivity data of the FeCl₃-doped polymers was obtained with the theoretical prediction of a variable-range hopping model.     

基于镍基固溶体催化的氢化镁储氢性能

采用高能球磨制备Ni?25％X(X=Fe,Co,Cu,摩尔分数)固溶体,然后将其掺杂于MgH2体系中.与球磨纯MgH2相比,MgH2/Ni?25％X复合体系初始放氢温度降低近90℃,其中,Ni?25％Co固溶体呈最佳催化效果.球磨MgH2/Ni?25％Co复合体系在300℃、10 min内可释放5.19％(质量分数)氢...