Gagan Anand

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.

AC and DC Conductivity Studies on Lead-Free Ceramics: Sr1–xCaxBi4Ti4O15(x = 0, 0.2, 0.4, 0.6, 0.8)

Sr1–xCaxBi4Ti4O15 [x = 0, 0.2, 0.4, 0.6, 0.8] ceramics are synthesized by solid-state reactive technique. Structural analyses are done by x-ray diffraction data. Morphological studies were carried out by scanning electron microscope, and the data showed plate-like structures. To understand the conductivity mechanism, frequency and temperature dependency of AC and DC conductivity studies are carried out. The conductivity measurements are done using an impedance analyzer (Wayn–Kerr) in the temperature range 100–600°C. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process follows the universal power law, and the hopping frequency shifts toward higher frequency side with increase in temperature, below which the conductivity is frequency independent. The variation of DC conductivity confirms that the ceramics exhibit negative temperature coefficient of resistance behavior at high temperature. DC conductivity values do not show any linearity with doping concentration; for a particular composition SCBT06, the DC conductivity was low.

Dielectric and Polarization Studies of Ca Substituted in Bi4SrTi4O15 Ceramics

The processing conditions, microstructure and dielectric properties of strontium bismuth titanate (SBT) were studied by means of Ca substitution in the strontium site referred to hereinafter as SCBT. The mechano-chemical activation method permits one to reduce the particle size of the initial products, so the surface area of the powder is increased, improving in most cases its reactivity. X-ray diffraction analysis showed the formation of a single-phase layered perovskite structure of SCBT. 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. Resonance studies were made on poled sample using an Impedance Analyzer. Elastic compliance [s33, s11] and coupling factor [k33, k31] were also obtained.

Rheology of Karanja (Pongamia) Oil Based Biolubricant

Rheology is the science of flow and deformation of liquids and semi-solid materials under the effect of an applied force. Rheological characterization of lubricating oils is important to predict their flow behaviour in each stage starting from preparation to processing up to application. Vegetable oils with high oleic acid content are considered the best candidate to substitute conventional mineral oil based lubricating oils and synthetic esters. The present article discusses the synthesis of biolubricant from non-edible Karanja oil in a two-stage transesterification process followed by reaction with branched neopentyl polyol to form polyol esters as the desired biolube product. The viscosity of synthesized biolubricant is measured at increasing temperatures using Rheometer model MCR302 by Anton Paar, Austria. The same apparatus was used for measuring shear stress, speed and torque. The study undertaken here intends to reveal relationship between viscosity and temperature, shear stress and shear rate; viscosity and shear rate and torque with shear rate of Karanja oil biolubricant. Variations in coefficient of viscosity with temperature, shear stress (τ) and shear rate (ϒ) are plotted accordingly. The synthesized biolubricant depicts Newtonian behaviour in hydrostatic regime.

Experimental and theoretical investigation of viscosity, density and sound velocity of jatropha diesel and pure diesel blends

ABSTRACT Production of biodiesel from the chemically extracted oil of Jatropha curcas was investigated. Jatropha oil biodiesel was blended with pure diesel and the rheological properties were studied. The viscoelastic properties studied included viscosity, stress and strain, and torque and density measurements with the variation in temperature from room temperature to 90°C. Significant differences were revealed between the viscoelastic properties of biodiesel and that of pure diesel. Additionally, an empirical relationship between the dependence of viscosity and density on temperature and fraction of biodiesel was also studied. Sound velocity was measured with variation in temperature. Regression analysis explained the dependency of sound velocity on temperature. J20 and pure diesel had the same approximate values making it convenient to use as an alternative to pure diesel.

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.