NOPR Collection:

Transport properties of ferroelectric (lead titanate) doped zinc - borate glasses

Wed, 01 Aug 2001 00:00:00 GMT

Title: Transport properties of ferroelectric (lead titanate) doped zinc - borate glasses Authors: Ubale, S K; Adgaonkar, C S Abstract: Ferroelectric doped zinc-borate glasses of the composition (1-x) [40 ZnO-60 B₂O₃] + x PbTiO₃ with = 0,0.05,0.1,0.15 ,0.2 were prepared. Physical properties such as density (d), molar volume (V), hopping distance (R), number of zinc ions per cc (N), and polaron radius (r_p) were reported. DC-conductivity was measured between 443 K to 573 K. From this, two graphs (a) -log σ versus 1/T and (b)- log μ versus 1/T were plotted. Activation energy W was determined from the plots. Effect of ferroelectric doping on the hopping conduction was studied. Polaron bandwidth (J) was found to satisfy the inequality for all samples thus suggesting adiabatic hopping conduction mainly governed by the activation energy. Page(s): 215-218

Effect of temperature and air feed rate on adiabatic gasification of Okaba sub-bituminous coal in Nigeria

Wed, 01 Aug 2001 00:00:00 GMT

Title: Effect of temperature and air feed rate on adiabatic gasification of Okaba sub-bituminous coal in Nigeria Authors: Adeyinka, J Soji; Akinbode, F O Abstract: The present investigations deal with, gasification of Okaba sub-bituminous coal (OSB) of Nigeria at varying temperatures and air feed rates. Analysis of gaseous product showed that the best yield of CO (80%) was recorded at 90% stoichiometric air feed, while the least CO yield (55%) was recorded at 110% stoichiometric air demand. It was observed that CO yield followed a pattern above 850 K thereby stabilising CO and increasing CO₂ yield at air variation. This study will help in evaluating both thermal efficiency and product distribution of OSB coal gasification. Page(s): 239-242

Hydration of rice husk ash blended portland cement

Wed, 01 Aug 2001 00:00:00 GMT

Title: Hydration of rice husk ash blended portland cement Authors: Singh, N B; Singh, Neelam; Rai, Sarita; Singh, Namwar Abstract: Effect of different concentrations of lactic acid on the hydration of rice husk ash blended portland cement has been studied by employing different experimental techniques. Lactic acid has been found to accelerate the hydration of blended cement. Page(s): 235-238

Effect of silica fume on the chloride and sulphate attack of sulphate resisting and high alumina cement composite

Wed, 01 Aug 2001 00:00:00 GMT

Title: Effect of silica fume on the chloride and sulphate attack of sulphate resisting and high alumina cement composite Authors: Helmy, I M; El-Didamony, H; Ali, A H; El-Sokkary, T M Abstract: The present investigation aims to study the chloride as well as sulphate attack on the composite of 85% SRC and 15% HAC. The effect of substitution of HAC with silica fume on the aggressive attack was also studied. The results indicate that the free lime contents decrease with silica fume and curing time in sulphate as well as chloride solution. The XRD results are in a good agreement with the compressive strength and chemical analysis. The substitution of HAC with SF improves the attack of chloride and sulphate ions on cement pastes. It can be concluded that superplastecizer must be added to the silica fume blended cements. Page(s): 228-234