M. M. Abou Sekkina

Mechanism of thermal dehydrochlorination

Co(II), Ni(II), Cu(II) and Zn(II) complexes ofo-hydroxyacetophenone Girard-P hydrazone were prepared by using the organic ligand and the corresponding transition metal chlorides. The protonation and formation constants were evaluated for the organic ligando-hydroxyacetophe-none Girard-P hydrazone and its transition metal complexes, respectively. The thermal behaviour of the test materials was established by means of DTA. Their semiconducting parameters were evaluated through DC-conductivity measurements, and their thermodynamic parameters were evaluated, assigned and interpreted. The mechanism of thermal dehydrochlorination of the metal chloride complexes was proposed.

Thermo-chemical behavior of solid nicotinic hydrazide metal complexes in correlation with their stoichiometry

Abstract New solid metal complexes of nicotinic hydrazides with strong biological activity have been prepared in neutral and alkaline media having 1:1 and 1:2 metal/ligand ratios. The materials obtained were subjected to careful programs of elemental analysis, quantitative thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Interesting results were obtained in agreement with each other leading to a better understanding of the exact molecular formulae of the solid complexes and their thermal stability in relation to the mode of preparation, medium of precipitation and various substitutions in the organic ligand molecules. Finally, metal chelates with an M/L ratio of 1:2 seemed to have lower thermal stabilities.

Further investigation on the effects of temperature and energetic ionizing radiation on monoclinic zirconia refractory

Several measurements have been undertaken on monoclinic zirconia refractory comprising the temperature dependence of DC electrical conductivity, infrared (IR absorption spectra) and Cu–K α X-ray diffraction patterns (XRDP) before and after exposure to various absorbed gamma doses (10 5 –10 8 rad). Promising results are obtained which hold good with one another explaining the interaction mechanism of ionizing radiation with monoclinic zirconia investigated. From conductivity measurements, the activation energies for carrier liberation are evaluated. The IR absorption spectra measurements are proved to be more sensitive and fast tool to detect the radiation damage than by X-ray diffraction method.

Thermoelectric and dielectric investigations of the thermochromism of various Na-acetylacetonate phases and intermediates

Abstract Sodium acetylacetonate was prepared by the interaction of sodium metal with acetylacetone. A fresh sample and various samples preheated at various temperatures were carefully prepared. Measurements were made by x-ray diffraction, IR absorption spectroscopy and differential thermal analysis (DTA). The temperature dependence of the electrical and dielectric properties of selective batches of Na-acetylacetonate phase and intermediates was measured.

Novel studies on the thermoelectro-mechanical properties of tantala-doped zirconia refractories

Abstract Samples of single doped zirconia refractories have been prepared and sintered at different temperatures according to the ceramic procedure. Comprehensive measurements have been made on these samples including dynamic hardness and DC-electrical conductivity before and after gamma irradiation (5·26 → 10 7 rad). Results obtained have been explained, interpreted, correlated and discussed in detail as functions of mole% tantala and sintering temperature.

Effects of temperature and non-stoichiometry on the electrical conductivity of some related perovskite ferrites

Abstract Several samples of di-lead ferrites as well as various alkaline earth and lanthanum partially substituted lead ferrites have been prepared and identified. Comprehensive measurements of true density, bulk density and the temperature dependence of electrical conductivity were undertaken on these samples. Density measurements indicated the attainment of well-sintered ferrite bodies for all samples prepared. Conductivity measurements proved the semiconducting character of materials investigated. At relatively low temperatures, some samples show inversion from the electronic to ionic conduction mechanism as well as metallic conduction mechanism. The extent of lead substitution by alkaline earth elements can be used as a rapid tool for controlling the desired semiconducting parameters during ferrite synthesis. Finally, best quality di-lead ferrite semiconductors were obtained by lead substitution by alkaline earths. This has been explained in detail and correlated with the induced ferrimagnetic paramagnetic phase inversion as a result of substitution interaction.

Effect of temperature and absorbed ionizing radiation doses on the electric and electronic properties of copper(II) complexes

Abstract A large number of copper(II) complexes derived from their related pyridine derivatives were prepared, crystallized and their characteristics established. The temperature dependence of d.c. electronic (electrical) conductivity and the electronic absorption properties of the materials under investigation were studied before and after exposure to various absorbed gamma does up to 10 7 rads using a 60 Co gamma cell. The effect of gamma absorbed doses on the d.c. electrical conductivity and electronic absorption spectra of γ-irradiated samples are discussed on the basis of the effect of ionizing radiation firstly on metal—oxygen, and secondly on CC bonds regarding the substituent effect on their electronic delocalization and their geometrical structures.

Effects of temperature and frequency changes on the dielectric properties of modified chalcogenides

Abstract Antimony oxide (Sb 2 O 3 ), antimony sulphide (Sb 2 S 3 ) and antimony selenide (Sb 2 Se 3 ) were prepared from high purity materials. Mixes of (I) Sb 2 O 3 (25%)+Sb 2 S 3 (75%) and (II) Sb 2 S 3 (25%)+Sb 2 Se 3 (75%) were prepared by mechanical mixing of the two components. Cylindrical blocks of the compressed powder were formed at a saturated pressure of 200 kg/cm −2 . The dielectric constant, ϵ′, a.c. electrical resistance, R x , and dielectric loss, ϵ″, were determined in the frequency range 0.2–10 MHz and in the temperature range 30–100 °C. The frequency dependence of the dielectric loss of each sample demonstrates the ohmic nature of the loss. Further discussion is put forward on the basis of the interaction of the dielectric dipoles of the two components of the mix and the partial ionic nature of the bond for the materials investigated.

Effects of temperature, and single and double dopings on the electromechanical properties of quaternary glasses

Abstract Pure, single doped (Cr 2 O 3 ) and double doped (Cr 2 O 3 /MnO 2 ) quaternary (alkali alumino—borosilicate) glasses have been prepared. Several measurements of the temperature dependence of the DC electrical conductivity and the corresponding activation energies for conduction were evaluated in each case. Furthermore, the Vickers hardness numbers were examined as a function of glass composition and extent of doping. The results obtained were discussed and correlated in detail. Finally, a correlation between the electrical and mechanical properties of the test glasses was deduced, and the optimum composition was recommended for the electronic glass industry.

Kinetics of the thermal behaviour of hot-pressed silicon nitride in the temperature range 1250 to 1400°C

Abstract The isothermal oxidation behaviour of silicon nitride hot-pressed with magnesia (0.2–0.8 wt.%) was studied in air at 1250–1400°C. Reaction was followed by measuring the weight-changes of the specimens at intermittent periods of exposures. The surfaces of oxidized specimens were examined by X-ray diffraction analysis. The oxidation rate follows the classical parabolic behaviour with an apparent activation energy of 98–235 kJ mol −1 depending on the MgO content. The scales consist of a mixture of unoxidized silicon nitride, crystalline phases (SiO 2 , Mg- and MgCa-silicates) and a glass phase containing other elements. The data suggest that impurities greatly lower the oxidation resistance of Si 3 N 4 in air. The oxidation results are discussed with regard to the chemical composition of the starting material.