New Advances in Materials Science and Engineering Vol. 1

MEMS devices are now used in many of engineering applications. To provide maximum applications of devices, more precise materials are required to design the devices. As micromachining processes are technology dependant so materials should be selected with proper research. Silicon is most suitable material for micromachining processes, so maximum of silicon compounds are used to fabricate MEMS devices. Research is ongoing with experimentation of other application specific materials. MEMS-VLSI integration adds another application field in MEMS industry. More materials are now required to design devices with MEMS-VLSI integration.

Complexes are biologically useful compounds and they have many biological activities. Many different inorganic and organic compounds can form stable complexes. Complexes of organic compounds, in which ligands are biologically active part, for example alkaloids, are especially interesting for researchers. Alkaloids: Colchicine and colchiceine can form stable complexes with alkali metals. A series of complexes of both alkaloids have been obtained and studied by ESI MS, MALDI MS, ¹H and ¹³C NMR, FT IR, DFT and PM5/PM7 calculations and molecular modelling. These complexes also have been tested against fungicidal and cytotoxic activity.

The colchicine complexes with Li⁺, Na⁺, K⁺ cations of different salts have been studied in details by MALDI and ESI mass spectra. In the ESI MS mass spectra has been shown that colchicine forms stable complexes of 1:1 stoichiometry with monovalent and divalent metal cations. Also formation of complexes of various stoichiometry has been detected. Colchicine complexes have not been characterised by modern mass spectra methods such as MALDI MS. The aim of this study was to summarize ESI MS study on colchicine and colchiceine complexes and check fragmentation pathways of colchicine complexes with alkali metals by MALDI MS mass spectra.

Pure zinc oxide (ZnO) and copper (Cu) doped ZnO thin films were synthesised from the precursor’s concentrations (zinc acetate and copper acetate) onto glass substrate via electrostatic spray pyrolysis (ESP) deposition technique at 350°C in air ambient with different Cu doping concentrations (0%, 5%, 10%, 15% and 20%). The thin films were analysed with regards to its morphological, optical, and electrical properties before and after annealing. The results indicate that the annealing of the thin films leads to improved surface morphology and better crystallinity quality. Nanofibers were observed around the nucleation centre in the pure ZnO thin films. The absorbance was recorded in the wavelength range of 230 nm to 1100 nm, and the optical transmission of the films was found to increase for increasing doping concentration of Cu up to 370 nm and then decreased for higher wavelengths. ZnO:Cu films displayed high optical transparency which is around 86% - 98% in the visible and infrared regions but minimum in the ultraviolet region. The band gap energy value of the pure ZnO films was found to be 3.20 eV, whereas the doped films revealed a continuous decreases for higher doping of Cu concentration, reaching a value of 2.66 eV. The refractive index of the films significantly changes with the deposition parameter and increases sharply from 1.4597 to 1.7865 and the highest electrical resistivity was found to be 8.83 μΩm, and the lowest optical conductivity of 0.113 MƱm^-1 was observed in the films with 20% Cu doped film, which indicates that the deposited films are highly suitable for photovoltaic cells and other optoelectronic device applications.

The present research focuses to evaluate a complete outlook of virgin high density polyethylene (HDPE) and polypropylene (PP) polyblends. Virgin PP of 10, 20, 30, 40 and 50 weight % is compounded with virgin HDPE. Tensile, Flexural and impact test specimens of virgin HDPE, Virgin PP and HDPE-PP composites are prepared via twin screw extruder and injection moulding methods as per ASTM D638-02a (Type-I), ASTM D790 and ASTM D256-A standards respectively. The mechanical properties like tensile strength, flexural strength, Izod impact strength are examined. Polymer sheets are fabricated using a two roll milling machine and compression moulding; and its electrical properties like dielectric strength, surface resistivity, volume resistivity are examined according to ASTM-D 257 standard. The study also includes effect of strain rate on tensile properties of the prepared composite at a cross head speed of 30, 40, 50, 60 and 70 mm/min. Design of experiment is conducted to find parameters dominating the tensile strength. All experiments are carried out at room temperature of 23°C and absolute humidity of 54%. Scanning electron microscopy (SEM), Atomic force microscopy (AFM) and polarised light microscopy (PLM) are used to observe the surface and crystal morphology. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) tests verify the non compatibility of both polymers. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques are used to study the thermal behaviour of composites. The results manifest dielectric strength and volume resistivity decreases with addition of PP to HDPE; whereas surface resistivity increases. Co-occurring spherulites are seen for polyblends; indicating the composite to be a physical blend of continuous and dispersed phases, but on the other hand PP improves the tensile and flexural properties of HDPE.

Ternary telluride alloys of Ge–Se(Sb)–Te and Si–Ge(Ga)–Te systems are synthesized in glassy and crystalline states for use in the terahertz frequency range. The transmission spectra of the obtained alloys are measured and studied in a wide wavelength range from 0.75 to 300 μm. The possible mechanisms of their formation are discussed. A comparative analysis of the results shows that the Ge₁₄Sb₂₈Te₅₆ alloy of the GST system is most promising. Its phonon spectrum is in the range of 40–280 cm^–1, limiting the long-wavelength transmission window of this alloy by 35 μm. Optimization of the Ge₁₄Sb₂₈Te₅₆ composition, the removal of impurities, and heat treatment will promote a further decrease in the absorbance in the far-infrared spectrum of this alloy.

A theoretical study on the effects of a moderate amount of sulfur when used as substituent impurity in place of oxygen in zinc oxide at its crystal form using Density Functional Theory (DFT). S-substituent amounts in percent go from 0.1% up to 1.0% and we analyze modifications in the crystal properties such as lattice characteristics, total energy, and gap energy. Lattice parameter c increased slightly as S-substituent percent increased, lattice parameter a had an opposite behavior because it decreased as the S-substituent increased and c/a rate had ups and downs but with very slight variation between consecutive values. Total energy calculations showed an increasing trend at all times and binding energy showed a decreasing trend at all times as the substituent percent increase but the variation between consecutive points was small. Gap energy had a decreasing trend with a maximum variation of 6.57% at 1.0% S-substituent from pristine ZnO. In order to correct the DFT underestimation of gap energy we applied a correction factor and found a decreasing trend as the substituent percent increase and observed the highest difference from undoped ZnO was 1.42% at 1.0% S-substituent. We study the effects on the ZnO structure occurring when moderate S-substituent amounts from 0.1% to 1.0% are used and provide new knowledge to predict if the geometric and electronic structure changes may be suitable for new applications of ZnO in optoelectronics.

Nanostructured thin films have been prepared by using various deposition techniques. The obtain films showed unique physical, optical and electrical properties. Therefore, these materials could be used in solar cell, optoelectronic, laser and sensor devices. In this work, the preparation of metal chalcogenide thin films by using electrodeposition method was reported. Electrodeposition method has many advantages such as low temperature is required, low cost investment, can produce desired film over large surface area and can control the thickness of the film. Characterization of obtained films was investigated by using various tools. The band gap values are in the range of 1.15 to 2.19 eV. Annealed films indicated excellent crystallinity if compared to as-deposited films.

This book chapter describes the production of dye sensitized solar cell by using different types of photo electrodes. This type of solar cell has been widely employed due to some unique properties such as high absorbance coefficient, chemical stability and electrochemical activity at nanoscale. Here, various types of adsorbing materials such as TiO₂, ZnO, NiO, CuO and tin oxide were highlighted. Summary of cell components of dye sensitized solar cells with their photovoltaic characteristics were reported also. The power conversion efficiency of more than 10% was obtained for dye sensitized solar cells based on literature.