New organic metal (BEDO-TTF)4Pt(CN)4·H2O

A new charge transfer salt of (BEDO-TTF)₄Pt(CN)₄·H₂O (BEDO-TTF = bis(ethylenedioxo)tetrathiafulvalene) composition has been prepared. X-ray analysis shows that the conducting donor layers of new θ″-type packing alternate with anion sheets composed of [Pt(CN)₄]⁻² anions, which are associated with H₂O molecules via hydrogen bonds. Temperature and magnetic field dependences of the resistance are presented.     

The preparation of (BEDO-TTF)2Cl·3H2O salt in Bu4NHgX3 + Bu4NX + 1,2-dichloroethane system. Shubnikov-de Haas oscillations

Electrochemical oxidation of BEDO-TTF (bis(ethylenedioxo)tetrathiafulvalene) in 1,2-dichloroethane in the presence of Bu₄NHgX₃ + Bu₄NX (X = I, Br, Cl) as a supporting electrolyte at low current density results in the isolation of (BEDO-TTF)₂Cl · 3H₂O salt. Its composition has been established by a chemical analysis (Cl, C, H), electron probe microanalysis and X-ray analysis. The temperature dependence of the resistance has been studied down to 1.5 K at a pressure up to 30 kbar and at room temperature up to 80 kbar. Field and angular dependences of magnetoresistance have been investigated.     

Spectral studies of highly conducting organic composites (BEDO-TTF)x/iodine

Infrared and Raman spectral properties of the organic composites obtained by direct solid–solid charge-transfer (CT) reaction between bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF) and iodine are investigated for the first time. The band attribution, an evaluation of the average charge on the donor molecule, changes of the BEDO-TTF spectra after composite formation and an analysis of the plasma-edge-like dispersion are presented and discussed.     

Study of new conducting organic composites based on BEDO-TTF molecule

Preparation of new organic composites by direct solid–solid charge-transfer reaction between bis(ethylenedioxy)tetrathiafulvalene (BO) and iodine is described. We present also dc electrical conductivity investigation of composites: (BO)_x/I, where 0.5<x<1.5. In the best case, corresponding to x=1, a metallic behaviour is observed down to 200 K prior to any annealing stage with a room temperature conductivity as high as 12.8 S cm⁻¹.     

Electrical transport properties of highly conducting charge-transfer organic composites formed by BEDT-TTF and gold iodides

Preparation and electrical properties of organic composites formed by direct charge-transfer (CT) reaction in the solid state of general formulae (BEDT-TTF)_x/(AuI) and (BEDT-TTF)_x/(AuI₃), where BEDT-TTF means bis-(ethylenedithio)tetrathiafulvalene, are presented. It is stated, that under appropriate conditions, composites show metal-like behavior with high and stable dc electrical conductivity.     

Conducting radical salts of the new electron donor bis(1.3-cyclobutylenedithio)tetrathiafulvalene

The new π-electron donor bis(1.3-cylobutylenedithio)tetrathiafulvalene (1.3-CBDT-TTF), which is only slightly different in the periphery of the molecule with respect to the well-known donor BEDT-TTF, was synthesized. The molecular structure has been characterized and the electrochemical behavior of this new donor was investigated. New cation radical salts were prepared by electrocrystallization methods. The structures of (1.3-CBDT-TTF)I₂, (1.3-CBDT-TTF)₂[AuI₂], (1.3-CBDT-TTF)_x(ReO₄)_y and (1.3-CBDT-TTF)₂PF₆·THF were characterized by X-ray analyses. The room temperature electrical resistivities of the radical salts are low and range between 0.5 and 5 Ω cm.     

A mixed κ-(ET)2Cu[N(CN)2]Br0.9I0.1 salt: synthesis,structure and superconductivity

Crystals of κ-(ET)₂Cu[N(CN)₂]Br_0.9I_0.1 (ET = bis(ethylenedithio)tetrathiafulvalene) salt have been prepared, and their structure and conducting properties have been studied. The crystals have been found to undergo a superconducting transition at 3.5 K (T_c) when coated with Apiezon N grease to provide a very low pressure (about 0.3 kbar). With the application of quasihydrostatic pressure, the T_c increases up to 5.9 K at about 3.0 kbar.     

Microwave and d.c. conductivity of α-ET2I3 and βt-ET2I3 microcrystals in polymer films

Electrical properties of conducting polymer films containing an ET₂I₃ (ET=bis(ethylenedithiolo)tetrathiafulvalene) polyiodide crystalline network have been investigated. It is shown that the conditions of preparation of these films, i.e., time of exposition to solvent iodine vapours, concentration of iodine in solvent, time and temperature of annealing, have a very strong influence on the conducting properties of the films. By choosing proper preparation conditions one can obtain conducting composites showing the conductivity behaviour characteristic of α-ET₂I₃ or β_t-ET₂I₃ single crystals.     

Coronoelectrets based on polypropylene composites dispersed by a TlIn x Ce1 − x Se2 semiconductor filler

The electret properties in the heterogeneous polymer-semiconductor system have been investigated by the method of the electret-thermal analysis (ETA) of the PP composites with TlInSe₂ and TlIn _x Ce_{1 ? x} Se₂ semiconductor fillers. It is shown that a small change in the filler structure causes a significant alteration of the spectrum of the thermostimulated depolarization currents. As the investigation shows, the TlInSe₂ and TlIn _x Ce_{1 ? x} Se₂ fillers having the p-type conductivity play the role of the structure-forming agent in the polypropylene matrix changing the structure of the polymer and the near-boundary layer of the polymer and the filler.     

High strength Ni–Zr–(Al) nanoeutectic composites with large plasticity

Micrometer-sized γ−Ni dendrite reinforced nanoeutectic matrix composites have been developed in (Ni_0.92Zr_0.08)_100–xAl_x (0 ≤ x ≤ 4) by arc melting. The eutectic matrix is composed of alternate nano-lamellae of intermetallic Ni₅Zr and fcc–Ni solid solution phases. All these composites exhibit very high strength, large compressive plasticity ∼25% and strain-hardening up to 1780 MPa. Al dissolves in γ−Ni(Zr) solid solution phase, decreases its hardness/strength, and increases the volume % of γ−Ni dendrite from 20% (x = 0) to 29% (x = 4). Whereas, refinement of the eutectic lamellae thickness from 275 nm (x = 0) to 160 nm (x = 4) increases the matrix hardness and retains the global strength of the composites. The effect of Al addition on the microstructure formation, volume fraction as well as the length scale of the constituent phases, and mechanical properties, have been discussed using an analytical model.     

N-doped carbon nanotubes synthesized in high yield and decorated with CeO2 and SnO2 nanoparticles

Nitrogen doped multiwalled carbon nanotubes (CN_xNTs) with high yield and purity have been successfully prepared from n-propylamine precursor with Co_xMg_1−xMoO₄ catalyst. The maximum yield of the CN_xNTs is 920%. SnO₂ and CeO₂ nanoparticles are decorated on the surface of CN_xNTs without any acid treatment due to the inherent interface activity. The TEM images reveal that SnO₂ and CeO₂ nanoparticles were anchored on the surface of the CN_xNTs uniformly, and the XPS results indicate that the doped nitrogen atoms of CN_xNTs play significant roles in immobilizing SnO₂ and CeO₂ nanoparticles, and the mechanism of the composite process has been discussed. The electrooxidation performance of the composites for NO at the modified electrodes was investigated. The CN_xNTs-based composites show greater activity and sensitivity than the conventional CNTs-based composites for NO electrooxidation, which render them excellent electrode materials for NO detection and other potential applications.     

Composite of polyaniline containing iron oxides with nanometer size

A composite of polyaniline (PANI) containing iron oxides with nanometer size was synthesized by a chemical method. The structure, electrical and magnetic properties of the resulting PANI-Fe_xO_y composites depend on the pH value of the reaction medium and temperature. For the basic preparation conditions (e.g. pH 14), the resulting PANI-Fe_xO_y, composite can be attracted by a magnet at room temperature, and its magnetization with the applied magnetic field exhibits a hysteresis loop with H_c = 0. It has been demonstrated that nanocrystalline ferromagnetic particles of Fe₃O₄ with 14.0 nm size correspond to super-paramagnetic properties observed from PANI-Fe_xy composites. For the acidic conditions (e.g. pH1), on the other hand, the electrical properties of the resulting PANI-Fe_xO_y composite show a semiconducting behavior. By comparison with PANI-Cl⁻¹, the lower conductivity (about 10⁻⁴ S/cm) for PANI-Fe_xO_y composite may be due to the presence of iron oxides in the composite, although its doping degree is the same as that of PANI-Cl⁻.     

Synthesis and electrical conductivities of charge-transfer complexes of bis(vinylenedithio)tetrathiafulvalene and its methyl derivatives with strong acceptors

Charge-transfer complexes of bis(vinylenedithio)tetrathiafulvalene (VT), bis(methylvinylenedithio)tetrathiafulvalene (DMVT) or bis(dimethylvinylenedithio)t tetrathiafulvalene (TMVT) with several strong acceptors, such as TCNQ, F₄TCNQ, DDQ, TCNE, Bu₄NBr₃ and I₂, were synthesized by leaving the mixed solution of a donor and an acceptor to stand at ambient temperature. Not only the usual 1:1 (donor:acceptor) complexes but also 2:1, 1:2, 3:1, 3:2 and 5:2 ones were obtained. Unfortunately, a single crystal of good quality was not obtained. The electrical conductivities of the compressed pellet samples were measured by van der Pauw's method. Most of them showed high conductivities of 10⁰–10⁻¹ S cm⁻¹ at room temperature. However, the TCNQ complexes were insulators. The electrical conductivities could be explained on the basis of the i.r. spectra of the complexes and the redox potentials of the donor and acceptor molecules.     

Si-W-Mo coating for SiC coated carbon/carbon composites against oxidation

In order to prevent carbon/carbon (C/C) composites from oxidation at 1773 K, a Si-W-Mo coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructures and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. It was seen that the compact multi-coating was composed of α-SiC, Si and (W_xMo_1 − x)Si_2. Oxidation behaviour of the SiC/Si-W-Mo coated C/C composites was also studied. After 315 h oxidation in air at 1773 K and thermal cycling between 1773 K and room temperature for 17times, no weight loss of the as-coated C/C composites was measured. The excellent anti-oxidation ability of the multi-coating is attributed to its dense structure and the formation of the stable glassy SiO₂ film on the coating surface during oxidation.     

Mechanical and corrosion properties of Ti-35Nb-7Zr-xHA composites fabricated by spark plasma sintering

To improve the bioactivity of Ti-Nb-Zr alloy, Ti-35Nb-7Zr-xHA (hydroxyapatite, x=5, 10, 15 and 20, mass fraction, %) composites were fabricated by spark plasma sintering. The effects of the HA content on microstructure, mechanical and corrosion properties of the composites were investigated utilizing X-ray diffraction (XRD), scanning electron microscope (SEM), mechanical tests and electrochemical tests. Results show that all sintered composites are mainly composed of β-Ti matrix, α-Ti and metal–ceramic phases (CaO, CaTiO₃, CaZrO₃, Ti_xP_y, etc). Besides, some residual hydroxyapatites emerge in the composites (15% and 20% HA). The compressive strengths of the composites are over 1400 MPa and the elastic moduli of composites ((5%–15%) HA) present appropriate values (46–52 GPa) close to that of human bones. The composite with 15% HA exhibits low corrosion current density and passive current density in Hank's solution by electrochemical test, indicating good corrosion properties. Therefore, Ti-35Nb-7Zr-15HA composite might be an alternative material for orthopedic implant applications.     

Attachment of poly[(ethoxyhexylsilylene)oligothienylene]s to inorganic oxide surface

Poly[(ethoxyhexylsilylene)quarter- and -quinquethienylene]s (EHSxT, x = 4 and 5) were prepared by Stille-coupling reactions of bis(bromothienyl)ethoxyhexylsilane and bis(tributylstannyl)bi- and -terthiophenes, respectively. Treatment of indium tin oxide (ITO) and TiO₂ electrodes with solutions of EHSxT in chloroform at 40 °C led to the formation of the polymer-attached electrodes. An application of the EHS5T-attached TiO₂ electrode to dye-sensitized solar cell was examined.     

Correlation of microstructure with high-temperature hardness of (TiC,TiN)/Ti–6Al–4V surface composites fabricated by high-energy electron-beam irradiation

Correlation of microstructure with high-temperature hardness of (TiC,TiN)/Ti–6Al–4V surface composites fabricated by high-energy electron-beam irradiation was investigated in this study. TiC, TiN and TiC+TiN powder mixtures containing 50% CaF₂ flux were deposited on the surface of a Ti–6Al–4V alloy substrate, and irradiated by high-energy electron beam to form 1-mm-thick, defect-free surface composite layers. The surface composite layers contained a large amount (over 30 vol.%) of precipitates such as TiC, TiN, (Ti_xAl_1−x)N and Ti(C_xN_1−x) in the martensitic or N-rich acicular α-Ti matrix. This microstructural modification including the formation of hard precipitates and hardened matrices in the surface composite layers improved hardness and high-temperature hardness two to four times greater than that of the substrate. In particular, the surface composite fabricated with TiN powders had the highest hardness because of the highest volume fraction of TiN and (Ti_xAl_1−x)N distributed in the hardened N-rich acicular α-Ti matrix. These findings suggest that the (TiC,TiN)/Ti–6Al–4V surface composites can be used for structural materials requiring excellent thermal resistance.     

The new salt κ-ET2[Hg(SCN)2I]: crystal structure and physical properties

The structure, resistivity and ESR of a new organic conductor κ-ET₂[Hg(SCN)₂I](ET=bis(ethylenedithio) tetrathiafulvalene) are studied. Its main crystallographic parameters are found to be: M-1213.2, a-38.03(1), b= 11.80(1), c = 8.329(9) Å; γ=98.1(2)°; V-3700(2) ų; space group P2₁Ib; Z = 4. It is shown that the radical cations are packed according to the κ-type in the organic sheets, and the anions form polymerized chains. Two different radical cation layers with different amounts of shortened S···S contacts and distinct interaction between anionic and cationic sheets are found. ESR linewidth is found to be 9-11G (300 K), which is substantially narrower than a typical linewidth for ET-based radical cation salts of the κ-type. Based on temperature dependences of the resistance anisotropy and ESR parameters, we suggest that a structure rearrangement with electron localization may take place around 50 K. The comparison of crystal structure and properties of the title compound with other salts of the family ET₂[Hg(SCN)_3−nX_n], where X=Cl, Br, and n = 1.2, is camed out.     

Studies on magnetic,dielectric and magnetoelectric behavior of (x) NiFe1.9Mn0.1O4 and (1 − x) BaZr0.08Ti0.92O3 magnetoelectric composites

In the present research work, the magnetoelectric (ME) composites of ferrite and ferroelectric phases with (x) NiFe_1.9Mn_0.1O₄ and (1 ? x) BaZr_0.08Ti_0.92O₃ (where x = 0.10, 0.20 and 0.30) respectively were synthesized by the conventional ceramic method. The X-ray diffraction pattern of the composite reveals a spinel phase formation for the ferrite and perovskite phase formation for the ferroelectric phase without any other phase. The SEM micrographs of composites were taken to determine the average grain size and also to study the surface morphology. The effect of constituent phase variation on the B–H hysteresis behavior and the dielectric properties was examined. The dielectric constant shows usual dielectric dispersion behavior with increasing frequency which is due to the Maxwell–Wagner type surface interfacial polarization. From the ac conductivity study, it is confirmed that the conduction in the present composites is of small polaron type. The static magnetoelectric (ME) voltage coefficient developed on the surface of magnetoelectric material was measured as a function of applied dc magnetic field. The maximum ME conversion factor of 1.18 mV/cm Oe was observed for x = 0.10 composite. Such composites may be useful to fabricate the magnetic field sensors and applicable in many linear ME devices.     

Corrosion-electrochemical properties of α-Fe + Fe3C + TiC nanocomposites in neutral environments

The corrosion-electrochemical properties of α-Fe + Fe₃C + TiC three-phase nanocrystalline composites in borate solutions with pH 6.3–9.0 both with and without NaCl are studied. α-Fe + Fe₃C + TiC composites are found to have heightened resistances at active-oxidation potentials of α-Fe and cementite due to the formation of xFeO · yTiO₂ mixed surface oxides. The protective properties of passive films based on xFeO · yTiO₂ and their resistance to local activation are worse than those of Fe₃O₄/γ-Fe₂O₃ (γ-FeOOH) passive films formed on iron and α-Fe + Fe₃C composites.