NOPR Collection:

Preparation of dispersed silica by hydrolysis of tetraethyl orthosilicate

1999-12-01T00:00:00Z

Title: Preparation of dispersed silica by hydrolysis of tetraethyl orthosilicate Authors: Singh, T K; Jain, C L; Sharma, S K; Singh, S S Abstract: Colloidal silica particles find innumerable applications in defence and civil , such as binder for refractories, antislip agent, antisoilant, antiblocking agent, reinforcement of adhesives and molecular sieves. The present studies report utilization of monodispersed spherical silica particles for a laser project on defence applications. The material has been developed using the sol-gel technique. Role of various solvent characteristics such as dielectric constant, dipole moment and viscosity on the process are discussed. Page(s): 349-351

Asymptotic behaviour of the laminar boundary layer flow of an incompressible fluid past a flat plate

1999-12-01T00:00:00Z

Title: Asymptotic behaviour of the laminar boundary layer flow of an incompressible fluid past a flat plate Authors: Singh, B B; Verma, S K Abstract: Here the asymptotic behaviour, as the similarity variable ‘η’ tends to infinity, of the solutions of the differential equations governing the laminar boundary layer flow of an incompressible fluid past a flat plate embedded in a saturated porous medium have been studied based on the method of asymptotic integrations of second order linear differential equations. It has been found that the principal solutions exhibit asymptotic behaviour as η→∞, whereas the independent solutions do not. Page(s): 346-348

Effect of flyash addition on dielectric properties of polypropylene

1999-12-01T00:00:00Z

Title: Effect of flyash addition on dielectric properties of polypropylene Authors: Chand, Navin; Khare, Nidhi Abstract: Dielectric properties of flyash filled polypropylene have been measured at different frequencies, and temperatures ranging from ambient to 160°C. It has been found that the dielectric constant of flyash filled and unfilled poly propylene decreases with increasing frequency up to 100 kHz. The dissipation factor of pure polypropylene decreases with increasing frequency. Dielectric constant of flyash filled polypropylene increases as compared to pure polypropylene. With increasing temperature, dielectric constant (ε´) and dissipation factor (tan δ) of flyash filled and unfilled polypropylene have been measured at all frequencies between 4-100 kHz. The β́ peak position has been found to shift towards higher temperature side for flyash filled polypropylene with increase in frequency. It has also been found that incorporation of flyash in polypropylene shifts the α_c peak towards the higher temperature side. Page(s): 342-345

Petrographic study of silica bearing rocks from Assam, India

1999-12-01T00:00:00Z

Title: Petrographic study of silica bearing rocks from Assam, India Authors: Boruah, R K; Neog, A K; Borah, PC; Baruah, G D Abstract: Silica bearing rock samples collected from various locations of the rock from Bihubar, Assam, India were studied using XRD, FT-IR and chemical analysis for assessing the durability of these rocks used for different purposes like building and road constructions. XRD patterns of the rock samples-reddish coloured rock variety (2QPR ) and white coloured rock variety (5QRS) showed that the samples contained the amorphous and crystalline materials, the former being the major one in both the samples. Both the samples contained α-quartz as the major phase with rutile, albite, calcite and illite-2M₁ for 2QPR and muscovite-2M₁, illite and analcime for 5QRS as the minor phases. Microstrains and crystallite sizes of α-quartz associated in the rock samples were derived by using Fourier and integral methods. FT-IR and chemical analysis are also included to supplement the result obtained from XRD method. The presence of the clay minerals and microstrains in both the samples indicate the possibility of degradation of the rocks in environment and hence ultimately effects its durability in utilization. Page(s): 338-341