Ajay Vasishth

Study of Rheological Properties of Industrial Lubricants

The most important rheological parameter for lubricants is viscosity as it also affects the tribological properties like friction between interacting surfaces and wear. This research intends to study the relationship between viscosity and temperature at different shear rates for multiple grades of three different categories of lubricants used for different applications viz. L1: MG20W50 (engine oil), L2: SAE20W50 (engine oil), L3: MC20W50 (mineral engine oil), L4: EP90 (gear oil), and L5: DXTIII (steering fluid). Constant high dynamic viscosity, shear stress, and low compressibility at different temperatures in multigrade as well as single grade industrial oil will help to maintain the surface film over the period of time and hence the reduction in wear. The dynamic viscosity of these chosen samples has been measured experimentally in temperature range of 20 to 50°C. The measurements have been extended to observe the dependence of shear rate, time, and temperature on the dynamic viscosity. All the samples are observed to behave like Newtonian fluids in the entire temperature range of study. Further, all samples seem to obey the Arrhenius relationship with temperature. Shear stress shows linear variation with shear rate exhibiting uniform viscosity which is substantiated by almost no variation in dynamic viscosity with shear rate for value above 5 per second.

A review on tungsten bronze ferroelectric ceramics as electrically tunable devices

ABSTRACT Ferroelectric ceramics are the most promising material for electrically tunable devices and found its application in microwave devices such as phase shifters, varactors and tunable oscillators and detectors. It has been reported that various non-ferroelectric compound such as carbon nanotubes (CNT), ferrites and microwave dielectrics are used for electrically tunable dielectric materials. This review paper gives overall summary of tungsten bronze ferroelectric ceramics on developing electrically tunable ferroelectric material and improving performance of dielectric material for various applications in microwave devices.

Synthesis and characterization of polycrystalline Ba5CaTi2-xMxNb8O30 (M=Cu) tungsten bronze electro ceramics

ABSTRACT The polycrystalline electro ceramic of composition Ba5CaTi2-xCuxNb8O30 (x = 0.0, 0.02) is synthesized using high-temperature solid state reaction technique. The synthesized ceramics studied for their structural and ferroelectric properties. X-ray diffraction (XRD) analysis reveals the formation of single-phase compound structure at room temperature with tetragonal tungsten bronze structure. Scanning electron microscope (SEM) depicts that the compound has well defined grains. The average grain size of the compound is observed in range (∼5 to 8 μm). The ferroelectric nature has been confirmed by recording polarization–electric field hysteresis loop. Raman Spectra at room temperature used to study the internal lattice properties of the ceramics.

Investigation of room temperature ferromagnetic behaviour in dilute magnetic oxides

ABSTRACT Manipulating the ferromagnetic interactions on the introduction of 3d and 4f orbital ions in semiconducting host material is essential for the growth of new generation spin based electronic devices. In this article we discuss about electronics which is based on the spin degree of freedom of the electron. In last few years there is tremendous work on introduction of magnetism in semiconducting devices. In this article we discussed the effect of doping and the cause of origin of magnetism in the dilute magnetic oxides.

Interdependence between electrical and magnetic properties of polycrystalline cobalt-substituted tungsten bronze multiferroic ceramics

Polycrystalline cobalt-substituted tungsten bronze ferroelectric ceramics with chemical composition Ba5CaTi2−xCoXNb8O30 (x=0.00, 0.02, 0.04 and 0.08) were synthesized by solid state reaction technique. X-ray diffraction (XRD) technique was used to confirm the phase formation and it revealed the formation of single phase tetragonal structure with space group P4bm. The surface morphology of the samples was studied by using the scanning electron microscopy (SEM) technique. The dielectric properties such as dielectric constant and dielectric loss have been investigated as a function of temperature and frequency. The P–E and M–H studies confirmed the coexistent of ferroelectricity and magnetism at room temperature. The P–E loop study indicated an increase in the coercive field while the M–H study depicted a decrease in the magnetization with the incorporation of cobalt ions.

Dielectric, ferroelectric and piezoelectric properties of Ca0.5Sr0.5Bi4Ti4O15 prepared by solid state technique

ABSTRACT The processing conditions, microstructure and dielectric properties of strontium bismuth calcium titanate (SCBT) were studied. SCBT was prepared by solid state reactive technique. X-ray diffraction analysis showed the formation of a single-phase layered perovskite structure. Morphological studies were carried out by SEM analysis. Dielectric measurements in the frequency 100 Hz – 1 MHz were made using an Impedance Analyzer (HP4192A) interfaced to a computer and the measurements were carried out from room temperature to 600°C. A variation in the dielectric constant was observed by the incorporation of calcium into the layered perovskite structure. The hysteresis loop revealed a variation in remnant polarization with the substitution of calcium in strontium.