George Liviu Popescu

TiO2 thin films prepared by sol ? gel method

There is a growing awareness that titania (TiO2) and TiO2-based oxide systems are the most promising candidates for the development of photoelectrodes for photoelectrochemical cell (PEC) for solar-hydrogen production [1]. The PEC is equipped with a single photoelectrode (photoanode) and cathode, both of which are immersed in an aqueous electrolyte. In this work we present a sol-gel method to prepare TiO2 thin films on ITO using tetraisopropoxides of titanium, acetylacetone, 1-butanol and Tween 80 as surfactant. The films were deposited on ITO coated glass slides by spray pyrolysis. UV-VIS spectra and fluorescence measurements were made for the solutions and films. X-ray diffraction was used for structural investigations and the morphology of the film was studied by Scanning Electron Microscopy.

Obtaining and Characterizing Alginate/k-Carrageenan Hydrogel Cross-Linked with Adipic Dihydrazide

The aim of this paper is obtaining and characterizing hydrogels based on different ratios of oxidized alginate (oA) and k-carrageenan (C), chemically cross-linked with adipic dihydrazide (adh). The alginate (A) was first oxidized with sodium metaperiodate in order to transform it into the dialdehyde derivative, a more reactive compound than alginate. A known procedure for oxidation of alginate with sodium metaperiodate in ethanol-water in order to improve alginate reactivity by transforming the hydroxyl end-groups into dialdehyde was used, preceded by a partially cleavage of the alginate chains. In the second stage, the mixture of dialdehydic derivative of oxidized alginate, k-carrageenan and glycerol subjected to reaction with adipic dihydrazide leads to a Semi-Interpenetrated Network covalently cross-linked alginate/k-carrageenan hydrogel (oACadh), based on the dihydrazone compound which is responsible for the chemical cross-linking. Pure alginate, k-carrageenan, oxidized alginate, adipic dihydrazide and the cross-linked hydrogel were characterized by: FTIR, XRD, and SEM.

Hydrolytic Degradation of Dental Composites

This study evaluated the hydrolytic degradation of two experimental (C1, C2) and two commercial composite (Tetric EvoCeram and Premise) prepared to be used in dental restorations. Two experimental composites and two commercial composites were undergoing hydrolytic degradation in three different medium: distilled water, artificial saliva and alcoholic solution (50/50). The samples were investigated immediately after polymerisation with halogen lamp Optilux 501 and after 33 days of immersion in all three medium, using Fourier transforms infrared analysis (FTIR). FT-IR spectra of samples from the same composite immersed in distilled water, artificial saliva and alcoholic solution, revealed mostly reducing the intensity of the characteristic peaks of Si-O-Si bond less Tetric composite immersed in artificial saliva, which peak intensity remains unchanged.

The Effects of a Diesel-Ethanol Blend Without Additives on Diesel Engine Operation

The objective of this study is to establish the influence that a blend of 90 % v/v Diesel and 10 % v/v Ethanol without additives has on the operation of a Diesel engine. In order to address the blend stability issue, the temperature of the fuel was maintained at 35 °C. For the comparison with pure Diesel operation the same test conditions were applied. The acquired data showed an increase in engine performances (power, torque) due to an increased indicated mean effective pressure. The higher values of the pressure come from an improved combustion, a conclusion which is supported by the pollutants measured in the exhaust gas: lower CO and O2, higher CO2 and higher NOx (as a result of the increased combustion temperature). The engine efficiency increases slightly.

Research Aiming Simultaneously Recycling of Waste Polyolefins by Pyrolysis, in Order to Obtain Some Fuels for Compression Ignition Engines

This paper presents the undertaken research for the establishment of the compatibility of some polyolefin waste to be recycled by pyrolysis. Polyolefin are materials produced by a polymerization process of unsaturated aliphatic hydrocarbons and represents the most important group of plastic materials. It is important to mention that among polyolefin, polyethylene (PE) and polypropylene (PP) own the first places as quantity of produced waste. Due to the common origin of the two plastic materials (PE and PP) and the relatively close melting points, we chose them for the obtaining of some fuels which are compatible with compression ignition engines. Starting from 100 % PE, the weight concentration of PP was increased up to 100%, the results of the undertaken experiments and measurements allowed us, in the final, to draw the chart of the variation of the yield of solid-liquid conversion as a function of weight concentration of the two chosen materials subjected to the process of recycling by pyrolysis.

CdS Powders Obtained by Chemical Bath Deposition

We studied the influence of the mixing on the properties of CdS powders obtained by Chemical Bath Deposition. The powders were obtained from baths containing cadmium chloride, thiourea, and ammonia. The obtained powders were characterized using FT-IR, in order to evaluate the purity of the obtained powder. Granulometric studies were made in order to establish the grain size distribution of the particles, and X ray diffraction in order to determine the structure of nanostructured CdS.

Optical properties of Fe 2 O 3 films obtained by spray pyrolysis

Nanostructured multilayered Fe2O3 films have been deposited onto commercial glass slides by spray pyrolysis using FeCl3 solution and nitrogen as carrier gas. The influences of thermal treatment and of the number of layers on the optical properties of the films have been studied. Structural investigations on the films were performed using X-ray diffraction.

Optical properties of Felinfg2l/infgOlinfg3l/infg films obtained by spray pyrolysis

Nanostructured multilayered Fe2O3 films have been deposited onto commercial glass slides by spray pyrolysis using FeCl3 solution and nitrogen as carrier gas. The influences of thermal treatment and of the number of layers on the optical properties of the films have been studied. Structural investigations on the films were performed using X-ray diffraction.