Investigation of Crystal Structure,Electrical and Magnetic Properties of Spinel Mn-Cd Ferrite Nanoparticles

Journal of Inorganic and Organometallic Polymers and Materials - Cd1 ? xMnxFe2O4 (x?=?0, 0.25, 0.5, 0.75, 1) spinel ferrite nanoparticle samples were synthesized...     

Grafting of vinyl acetate onto chitosan and biocidal activity of the graft copolymers

The reaction process of polycarbosilane (PCS) fiber cured by cyclohexene vapor has been studied and compared with that of PCS fiber cured by air. The influence of curing temperature on Si? H bond reaction degree and gel content, the structure and composition of PCS were investigated by FTIR, EA, TGA, NMR, and GC‐MS. The results showed that, Si? H bond in the molecular structure of PCS reacted during cyclohexene curing process and the reaction degree increased when the curing temperature increases. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. Si? H radical and Si? CH₂ radicals formed Si? CH₂? Si crosslinking of PCS molecules through the agency of cyclohexene. Some cyclohexyls linked to principal chain of PCS, which was proven by ¹³C‐CPMAS‐NMR, and broke off, and cyclohexane and some monosilane are generated as byproducts when temperature increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The effect of temperature and humidity on interdiffusion of gold and titanium in thin films

Gold-titanium thin films are frequently used in a number of devices where gold is the conductor and titanium the bonding agent between gold and glass or ceramic substrates. Exposed to the corrosive environments, gold-titanium metallizations deteriorate and lead to failure of the devices. In this work, a preliminary study, the effect of humidity and temperature on interdiffusion of gold and titanium films was investigated. It was found that during the initial exposure period of gold-titanium thin film samples, the electrical resistance decreased. This decrease of electrical resistance occurs at temperatures as low as 70° C and can probably be ascribed to annealing processes in the samples. Exposure of the samples to higher temperatures results in the diffusion of titanium along the grain boundaries of the gold to the surface of the sample and in an increase of electrical resistance. It was observed that at 325° C titanium diffuses from grain boundaries into the gold grains and forms a gold-titanium alloy. An addition of the water vapour to the agron atmosphere does not noticeably affect the diffusion process. Optical microscope observations, of the titanium diffusion to the sample surface were confirmed by scanning electron microscopy and by X-ray fluoroscence counts in a scanning electron microscope.     

A.c. conductivity for amorphous TeO2-P2O5 glass system

The a.c. conductivity for the TeO₂-P₂O₅ glassy system was measured in the temperature range 300–573 K and in the frequency range 100 Hz to 10 kHz. The a.c. conductivity () increased with frequency according to the relation ()^s. The frequency exponent s was found to decrease with increasing temperature. The composition dependence of the conductivity was also investigated. The density of states was also calculated using the Elliott model. The a.c. conductivity increased over the studied temperature range. The obtained experimental data have been analysed with reference to various theoretical models. The analysis shows that the correlated barrier hopping (CBH) model is the most appropriate mechanism for conduction in the TeO₂-P₂O₅ glass system.     

Frequency and temperature dependencies of a.c. conductivity of polyvinyl alcohol (PVA)-CoCl2 composites

The a.c. conductivity for polyvinyl alcohol (PVA)-CoCl₂ composites prepared by a casting method has been measured at different frequencies (0.1–10 kHz) in the temperature range 300–450 K. At constant temperature, the frequency dependence of a.c. conductivity, (), was found to fit the established equation () = A ^s quite well. On the other hand, the temperature dependence of a.c. conductivity suggested an electronic hopping conduction mechanism in a thermally assisted electric field. Various theoretical mechanisms have been discussed to clarify the conduction processes in these samples. The correlated barrier hopping (CBH) mechanism, proposed by Elliott, was found to be the most appropriate one.     

Thermoluminescence dosimetry in the μGy range of neodymium-doped tellurite-phosphate glass

Thermoluminescence (TL) of tellurite-phosphate glass of the composition of (TeO_20.81-P₂O_50.19) doped with different concentrations of Nd₂O₃ was prepared. The optimum concentration of Nd₂O₃ was experimentally determined as 10^–3 wt% Nd₂O₃ in this glass. TL showed a single, isolated glow curve which peaked at approximately 498–513 K (depending on the Nd concentration). This peak is very suitable for radiation dosimetry, and obeys second-order kinetics. The TL response against the irradiation dose was found to be linear in the low-dose region (11.2–224.2 Gy), indicating the high sensitivity of our glass samples to low-dose rays. Finally, the trap depth was also calculated, using methods concerning the second-order kinetics.     

Resistivity and magnetic susceptibility studies of TlmCan?1Ba2CunOy before and after doping with LiF

Measurements of the superconducting resistance as a function of temperature were performed using the conventional four-probe method. The transition to complete superconductivity was recorded for samples of (Tl₂Ca₂Ba₂Cu₃O₁₀)_100–xLiF _x (2223) mixed with different LiF ratiosx=0, 2, 4, 5, 6, 8, 10, and 12 wt.%. It was found that the transition temperatureT _c was increased up to 5 wt.% of LiF. Further addition of LiF decreasesT _c . Therefore, 5 wt.% LiF is the optimum concentration giving a transition temperature of 130 K. Measurements of the superconducting resistance of all the samples except the (1111) compound show that the addition of 5 wt.% LiF increasesT _c and decreases the metastable phases. The real part of the a.c. magnetic susceptibility _a.c. is studied using a zero-field cooled mechanism. The temperature dependence of _a.c. for the prepared TlBaCaCuO having stoichiometric composition of (1111), (2223), (2234), and (3245) and that after doping with 5 wt.% LiF showed a broad feature. The transition to the complete diamagnetic state takes place in a broad transition region containing many transition steps, indicating the presence of metastable phases. The addition of LiF decreases the fluctuation in the transition region and its effect in reducing the number of multiphases.     

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile,methyl methacylate and indene

Terpolymer samples were prepared by free radical polymerization of methyl methacrylate (MMA), indene (In) and acrylonitrile (AN) in bulk. The samples were chosen so that the molar ratio of AN to MMA varied from 1.00:4.39 to 1.00:0.83, while the molar ratio of In was kept almost unchanged. The glass transition temperatures (T_g) of the samples were determined using differential scanning calorimetry. Moreover, isochronal dynamic mechanical measurements of the complex bending modulus as well as the complex dielectric permittivity were carried out over wide temperature ranges, namely from 50 to 190 °C, depending on the material investigated. All samples exhibited a single common T_g value, which increased to higher temperature upon increasing the content of AN. In addition, the results were investigated quantitatively in the framework of a molecular model. Copyright © 2006 Society of Chemical Industry     

Chemical and electrochemical inhibition studies of corrosion and hydrogen surface embrittlement. I. Fe0.78B0.13Si0.09 amorphous alloy in molar HCl

Diorthoaminophenoldisulfane (DOAPD) was synthesized for use as a corrosion inhibitor and in order to test its effect on the hydrogen surface embrittlement of Fe_0.78B_0.13Si_0.09 alloy. Results of electrochemical and gravimetric measurements were consistent and confirmed the beneficial role of this inhibitor. The amorphous state of the alloy was confirmed by X-ray measurements and differential thermal analysis. The maximum inhibition of corrosion was attained in the presence of 10^–4 M DOAPD. This inhibitor concentration also gave rise to a diminution of metal hydrogenation. A mechanism explaining the mixed role of the disulfane was confirmed.     

Application studies on red-light emitting ZnS-CdS and Y2O2S:Eu3+ phosphors used in cathode-ray tube screens for television

The (Zn_0.27, Cd_0.73)S:Ag, Cl, (Zn_0.77, Cd_0.23)S:Cu, Cl and Y₂O₂S:Eu³⁺ red-light emitting phosphors have been used in the preparation of cathode-ray tube screens for television. The dependence of screen brightness on both electron-beam accelerating voltage and current densities has been studied. The theoretically calculated intrinsic efficiencies are compared with the experimental efficiencies. The chromaticity of the cathode-ray tube screens was also studied as a function of accelerating high tension and current density. Cathodoluminescence emission spectra for these phosphors at room temperature are also measured.