Material processing and surface reaction studies in free piston driven shock tube

Recently established moderate size free piston driven hypersonic shock tunnel HST3 along with its calibration is described here. The extreme thermodynamic conditions prevalent behind the reflected shock wave have been utilized to study the catalytic and non-catalytic reactions of shock heated test gases like Ar, N2 or O2 with different material like C60 carbon, zirconia and ceria substituted zirconia. The exposed test samples are investigated using different experimental methods. These studies show the formation of carbon nitride due to the non-catalytic interaction of shock heated nitrogen gas with C60 carbon film. On the other hand, the ZrO2 undergoes only phase transformation from cubic to monoclinic structure and Ce0.5Zr0.5O2 in fluorite cubic phase changes to pyrochlore (Ce2Zr2O7±δ) phase by releasing oxygen from the lattice due to heterogeneous catalytic surface reaction.

Combustion and Thermal Decomposition of Ammonium Perchlorate-Aluminium Composite Pellets: Mechanism for Aluminium Participation

Thermal behaviour of ammonium perchlorate-aluminium composites is studied using differential thermal analysis, thermogravimetry and differential scanning calorimetry. Electrical resistivity studies throw light on the mechanism of ammonium perchlorate decomposition at different aluminium contents. The differences observed in burning behaviour by earlier authors is explained in terms of porosity and thermal conductivity of the composite.

Thermal Decomposition Studies on Ammonium Perchlorate—Polybutadiene Composite Propellant

The thermal decomposition of ammonium perchlorate based solid composite propellant using carboxyl terminated polybutadiene as binder has been studied employing thermogravimetry and differential thermal analysis techniques. The thermal decomposition characteristics of the propellant have been found to be quite similar to those of pure ammonium perchlorate with activation energy, 32 Kcal/mole and 60 Kcal/mole respectively in the low and high temperature regions. The effect of the sample size and shape on the thermal decomposition has also been evaluated.

Rapid synthetic routes to prepare LiNi1/3Mn1/3Co1/3O2 as a high voltage, high-capacity Li-ion battery cathode material

LiNi1/3Mn1/3Co1/3O2, a high voltage and high-capacity cathode material for Li-ion batteries, has been synthesized by three different rapid synthetic methods. viz. nitrate-melt decomposition, combustion and sol-gel methods. The first two methods are ultra rapid and a time period as small as 15 min is sufficient to prepare nano-crystalline LiNi1/3Mn1/3Co1/3O2. The processing parameters in obtaining the best performing materials are optimized for each process and their electrochemical performance is evaluated in Li-ion cells. The combustion-derived LiNi1/3Mn1/3Co1/3O2 sample exhibits large extent of cation mixing (10%) while the other two methods yield LiNi1/3Mn1/3Co1/3O2 with cation mixing <5%. LiNi1/3Mn1/3Co1/3O2 prepared by nitrate-melt decomposition method exhibits superior performance as Li-ion battery cathode material.

Combustion and thermal decomposition characteristics of composite solid propellants

The role of thermal decomposition of the binder and the oxidiser in the thermal decomposition, ageing and combustion of composite solid-propellants has been investigated. The present study shows that the burning rate and ageing of polystyrene and ammonium perchlorate propellant are related to the thermal decomposition of the propellant itself and ammonium perchlorate.

Decomposition technique for composite signals

A new method for decomposition of compo,.~itsei gnals is presented. It is shown that high freyuency portion of composite signal spectrum possesses information on echo structure. The proposed technique does not assume the shape of basic wavelet and does not place any restrictions on the amplitudes and arrival times of echoes inm the composite signal. In the absence of noise any desirrd resolution can he obtained The effect of sampling rate and jFequency window function on echo resolutio.~ are di.wussed. Voiced speech segment is considered as an example of conzpxite sigrnl to demonstrate the application of the decomposition technique.

Mechanistic Studies on Composite-Solid Propellants

Abstract is not available.

Cooling of a composite slab

A mixed boundary value problem associated with the diffusion equation, that involves the physical problem of cooling of an infinite parallel-sided composite slab, is solved completely by using the Wiener-Hopf technique. An analytical expression is derived for the sputtering temperature at the quench front being created by a cold fluid moving on the upper surface of the slab at a constant speed v. The dependence of the various configurational parameters of the problem under consideration, on the sputtering temperature, is rather complicated and representative tables of numerical values of this important physical quantity are prepared for certain typical values of these parameters. Asymptotic results in their most simplified forms are also obtained when (i) the ratio of the thicknesses of the two materials comprising the slab is very much smaller than unity, and (ii) the quench-front speed v is very large, keeping the other parameters fixed, in both the cases.

Vibrations of Multifiber Composite Shells-Some Numerical Results

A study of vibrations of multifiber composite shells is presented. Special attention is paid to the effect of composition of different fibers on the frequency spectrum of a freely vibrating cylindrical shell. The numerical results indicate clustering of frequency spectrum of a freely vibrating cylindrical composite shell as compared with the isotropic shell, and the spectrum varies considerably with the composition of the constituent materials.

Comprehensive view of the combustion models of composite solid propellants

Abstrat is not available.

Nd2O3 : Eu3+ nanocrystalline phosphor - a new potential thermoluminescing material for dosimetry

Nanoparticles of trivalent Eu3+-doped Nd2O3 phosphors have been prepared using a low-temperature solution combustion method with metal nitrate as precursor and oxalyldihydrazide as a fuel at a fairly low temperature (<500 degrees C) and in a very short time (<5 min). A powder X-ray diffraction pattern reveals that cubic Nd2O3 : Eu3+ crystallites are directly obtained without the requirement of further calcinations. The crystallite size, evaluated from Scherer's formula, was found to be in the range of 20-30 nm. The microstructure and morphology were studied by scanning electron microscopy, which showed the phosphor to be foamy and fluffy in nature. Thermoluminescence characteristics of the Nd2O3 : Eu3+ have been studied using gamma irradiation. These demonstrate that the phosphor is suitable for use as a dosimeter.