Anisotropy of Electrical Resistivity and Hole Mobility in InTe Single Crystals

The temperature dependences of the electrical resistivity and Hall mobility of p-type InTe chain single crystals in parallel and perpendicular directions to c-axis have been investigated in the temperature range of 28–260 K. The high anisotropy between ∂‖ and ∂⟂ which depends on temperature is attributed to high concentration of stacking faults due to weak interchain bonding. The mobility parallel to c-axis was found to vary with temperature asμ α Tⁿ where n = -0.6 due to hole scattering on polar optical phonons. The mobility perpendicular to c-axis above 140 K increases with temperature exponentially with an activation energy of 0.03 eV which is attributed to the hopping mechanism due to the barriers between the chains.     

Annealing effect on electrical and photoconductive properties of Si implanted GaSe single crystal

GaSe single crystals grown by Bridgman method have been doped by ion implantation technique. The samples were bombarded in the direction parallel to c‐axis by Si ion beam of about 100 keV to doses of 1 × 10¹⁶ ions/cm² at room temperature. The effects of Si implantation with annealing at 500 and 600 °C on the electrical properties have been studied by measuring the temperature dependent conductivity and photoconductivity under different illumination intensities in the temperature range of 100–320 K. It is observed that Si implantation increases the room temperature conductivity 10⁻⁷ to 10⁻³ (Ω‐cm)⁻¹ depending on the post annealing temperature. The analysis of temperature dependent conductivity shows that at high temperature region above 200 K, the transport mechanism is dominated by thermal excitation in the doped and undoped GaSe samples. At lower temperatures, the conduction of carriers is dominated by variable range hopping mechanism in the implanted samples. Annealing of the samples at and above 600 °C weakens the temperature dependence of the conductivity and photoconductivity. This indicates that annealing of the implanted samples activates Si‐atoms and increases structural deformations and stacking faults. The same behavior was observed from photoconductivity measurements. Hence, photocurrent‐illumination intensity dependence in the implanted samples obeys the power low I_pc ∝ Φⁿ with n between 1 and 2 which is an indication of continuous distribution of localized states in the band gap. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and Electrical Characterization of Ag3Ga5Te9 and Ag3In5Se9 Crystals

X-ray powder diffraction studies revealed that Ag₃Ga₅Te₉ and Ag₃In₅Se₉ crystallize in orthorhombic and tetragonal systems, respectively. The temperature dependent conductivity and Hall effect measurements have been carried out between 65—480 K. Ag₃Ga₅Te₉ exhibits p-type conduction with a room temperature conductivity of 4.3 × 10^—4 (Ω · cm)^—1 and mobility less than 1 cm²/V · s. Ag₃In₅Se₉ was identified to be n-type with room temperature conductivity 7.2 × 10^—5 (Ω · cm)^—1 and mobility 20 cm²/V · s. From temperature dependence of the conductivity three different impurity ionization energies were obtained for both compounds. The anomalous behavior observed in the temperature dependence of mobility was attributed to the different features of the microstructure.     

New,strong cationic hydrogels: Preparation of N,N,N′,N′‐tetraallyl piperazinium dibromide and its copolymers with N,N‐diallyl morpholinium bromide

N,N,N′,N′‐tetraallyl piperazinium dibromide (TAP) has been prepared in high yields by quaternization of N,N′‐diallyl piperazine with allyl bromide. Herein, we have described preparation of nonhydrolysable, strong, cationic hydrogels by copolymerization of TAP with N,N‐diallyl morpholinium bromide (DAM) in the presence of t‐butyl hydroperoxide as initiator in aqueous solutions. Because the monomer and crosslinker involved consist of quaternary amine functions, these hydrogels are fully cationic and do not carry hydrolysable groups. Contrary to expectations, the quaternary amine hydrogels presented do not show any super absorbency, instead dry gel particles in water undergo spontaneous disintegration with an audible bursting of the particles due to instantaneous, high osmotic pressure. Whereas, in KBr or HBr solutions, the swellings are relatively slow. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1006–1013, 2000     

A thermodynamic model for electrical current induced damage

Electromigration-induced damage, which is in principal an irreversible mass diffusion under high current density, has been a concern for VLSI design for a long time. Miniaturization of electronic device sizes down to nano-scale will make electromigration a concern for all conducting components. This paper uses thermodynamics, statistical mechanics and mass transport (diffusion) principals to propose a model for electromigration process and a damage evolution model to quantify the degradation in microelectronics (and micro electromechanical system) solder joints subjected to high current densities. Entropy production in the system is used as a damage metric. The irreversible thermodynamic damage model utilized in this work has previously been successfully applied to thermo-mechanical fatigue of microelectronic solder joints. In this paper we extend this model to electromigration-induced degradation.Electromigration process is modeled by the atomic vacancy flux (mass diffusion) process. The proposed unified model is compared with several existing analytical and empirical models. A comparison of the damage evolution model proposed in here agrees well with empirical models proposed in the literature.     

Experimental and theoretical NMR study of 4-(3-cyclohexen-1-yl)pyridine

(1)H, (13)C, DEPT, COSY, NOESY and HETCOR NMR spectra of 4-(3-cyclohexen-1-yl)pyridine (4-Chpy) have been reported for the first time. (1)H and (13)C NMR chemical shifts of 4-Chpy (C(11)H(13)N) have been calculated by means of the Hartree-Fock (HF) and Becke-3-Lee-Yang-Parr (B3LYP) density functional methods with 6-311++G(d,p) basis set. Comparison between the experimental and the theoretical results indicate that density functional B3LYP method is superior to the scaled HF approach for predicting NMR properties.     

Preparation of poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes and their application in wastewater treatment

In this study, new poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes were prepared firstly and then characterized. Then they were used in the removal of Fe(III) and Co(II) ions from wastewater with a stirred ultrafiltration cell. Also, alginic acid polymer was used as complexing agent to enhance the retention. In the filtration of Fe(III) and Co(II) solutions, the effects of pH, concentration of solutions, and pressure on the retention percentage were examined. Aqueous solutions of Fe(III) and Co(II) were filtrated at the stirred velocity of 400?rpm. The maximum retention percentage was found as 78.66% for Fe(III) solution at the pH of 3.3, concentration of 0.3?×?10^?4 M Fe(III) solution, pressure of 40?psi by using 2.5 (w/v)% Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes. For Co(II) solutions the maximum retention percentage was found as 77% at the pH of 6, concentration of 0.3?×?10^?4 M Co(II) solution, pressure of 50?psi by using 2.5 (w/v)%Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes.     

Conformational and electronic properties of N-methacryloyl-(L)-glutamic acid

Conformers of N-methacryloyl-(L)-glutamic acid (MAGA, C₉H₁₃NO₅) in the gas phase, benzene or methanol environment were searched by the density functional theory (DFT) and time-dependent DFT. Selected conformational isomers based on potential energy surface analysis were studied by considering the structural and electronic properties. B3LYP functional, and HF and MP2 levels were used with the 6-31+G(d,p), 6-311+G(3df,p) and aug-cc-pVDZ basis sets. We explored the effect of medium on the conformational preferences, UV spectra and frontier molecular orbitals of the conformers. The outcomes of this research will be useful for future studies including moieties analogous to MAGA.     

Dehydroxylation of high-energy ball-milled diasporic bauxite

The review consists of four parts. Part I is about the thermal transformation in clay minerals under firing and about the properties of fired clay. The transformations in the clay are expressed quantitatively with the extent of conversion, α, which is the function of two parameters of firing process, time t and temperature T: α?=?f(t, T). Part II is about the estimation of firing temperature after the analysis of the products of firing clays. All the estimations are speculative, without mathematical equations. It is impossible to derive the value of only one variable T from α?=?f(t,T), the function of two variables. Part III is about the long-term inverse transformation in fired ceramic paste under ambient conditions. The mass gain as a function of time is used for the evaluation of the time elapsed from the ancient firing, t. Part IV is about the visualization of the extent of conversion of the clay in the paste after all direct and reverse reactions, i.e., α.