Shahida Begum

Whiskers and Particulates

In this chapter an overview of whisker, platelet, and particulate reinforcements for composites with actual or potential use in structural, thermal, or electronic applications are presented. The reinforcements can be used in different reinforcing phase, such as, polymer, ceramic or metal matrix. Enhancement in mechanical, magnetic, thermal, electrical, or other properties can be achieved with the use of reinforcing materials. Whiskers, particulates and flakes are advantageous in terms of processing and cost than that of continuous fiber. Whiskers have superior specific mechanical properties for elevated temperature performance than that of fibers. Particulates are comparatively cheap and can produce isotropic properties.

Hot Corrosion by Fused Salts

Hot corrosion is the oxidation of a material at high temperature accelerated by the presence of a fused salt film. The most important corrosive hot salt film is based on sodium sulfate and its solutions, because sodium is present everywhere, especially as an aerosol near seawater, and sulfur is a common impurity in fuels. A fused salt film is deposited either when a vapor-laden gas contacts a solid surface below its dew point, or else when a solid deposit (e.g., collected on an air filter) detaches and impacts on hot hardware. In many aspects, hot corrosion is an analog to atmospheric corrosion by aqueous films near room temperature, but several important physical properties are different: for example, dissolved SO 3 is the principal oxidant and not dissolved O 2 . As proven experimentally, only fused salts are very corrosive, as they isolate the substrate from the oxidant so that the formation of passive protective surface oxides is prevented. Generally, if fused Na 2 SO 4 contacts a base-metal alloy (e.g., Fe–Ni–Cr), sulfides of the protective component (e.g., chromium) are formed, especially along grain boundaries, and the oxidation attack is rapid.

Use of Oil Palm Waste as a Renewable Energy Source and Its Impact on Reduction of Air Pollution in Context of Malaysia

One of the most efficient and effective solutions for sustainable energy supply to supplement the increasing energy demand and reducing environment pollution is renewable energy resources. Malaysia is currently the worlds second largest producer and exporter of palm oil and 47% of the worlds supply of palm oil is produced by this country. Nearly 80 million tonnes of Fresh Fruit Bunches (FFB) are processed annually in 406 palm oil mills and are generating approximately 54 million tonnes of palm oil mill effluent (POME), known to generate biogas consisting of methane – a Green House Gas (GHG) identifiable to cause global warming. This is 21 times more potent GHG than CO2. These two major oil palm wastes are a viable renewable energy (RE) source for production of electricity. If the two sources are used in harnessing the renewable energy potential the pollution intensity from usage of non-renewable sources can also be reduced significantly. This study focused on the pollution mitigation potential of biogas as biogas is a renewable energy. Utilization of this renewable source for the production of electricity is believed to reduce GHG emissions to the atmosphere.

NDT Techniques: Ultrasonic

This article describes the use of ultrasonic techniques in the nondestructive testing of structural materials. In a discussion of history and general principles, the physical issues that govern ultrasonic inspection are presented. This is followed by a discussion of the types of instrumentation used to implement these principles and of the types of applications in which they are deployed. The capabilities of these techniques and the limitations that they face are considered, along with technological advances aimed at overcoming these limitations. The article concludes with a discussion of future directions of research.

Physical Characterization and Microstructure Evaluation of Titanium Dioxide Semiconductor Discs Processed with Binders

The processing of TiO2 semiconducting materials has a long route with numerous contributing variables. The binder plays an important role in the development of this electro-ceramic material. Higher density and strength of a green body are critical not only for handling at its green state but also to avoid the causes of flaw formation during sintering. Use of appropriate binder can lead to improve characteristics of powder which will reduce density gradient in the green body during compaction. Enhanced green properties can consequently lead to higher fired strength of the varistor discs. The binder system is anticipated to have an influence on the grain growth and microstructure which in turn affect the electrical performance. To investigate this phenomenon, TiO2 powder doped with 0.2% of Ta2O5 was processed with and without binder polyvinyl alcohol. The prepared samples were characterized by evaluating the physical properties like green density, fired density, axial and radial shrinkage, micro hardness and compressive strength. It was observed that TiO2 processed with binder exhibited better properties compared to powder processed without binder. The higher percent of binder enhanced the properties further. XRD revealed that the diffraction angle peak was similar to that of pure TiO2. SEM analysis indicated that the average grain size was larger for discs prepared with higher percent of binder. It is anticipated that the larger grain size will improve varistor properties in terms of low voltage applications.

Role of Surface to Volume Ratio of Zinc Oxide Arrester Blocks on the Energy Absorption Capability

The functional life of a zinc oxide arrester block is largely dependent on its energy absorption capability. This capability is an important performance characteristic of a lighting arrester which leads to enhanced reliability of a surge protection system. An arrester block is usually cylindrical in shape with two flat surfaces. Injected energy of transient electrical surge into the arrester body is transformed into heat and dissipated through the surface of the disc body. This study has been conducted to observe whether the higher surface to volume (S/V) ratio of an arrester block enhances the capability of energy absorption or not. The round side or C-surface of the cylindrical disc was ground by diamond wheel to transform into hexagonal shape. By making the modification of the geometrical shape an increase of about 11% in S/V ratio was achieved. ZnO arrester blocks of both shapes were tested for energy. The average energy absorption capability for the hexagonal discs was found to be 483 J.cm−3 compared to that of 357 J.cm−3 for the discs having the cylindrical shape. Thus, about 35% increase in energy absorption capability is observed for the hexagonal discs. This knowledge can be useful in designing the geometry of the device for improved functional reliability of electrical system.

Investigation on Wall Thinning and Creep Damage in Boiler Tube due to Scale Formation

Boiler is a closed vessel in which the water is heated up to convert it from the liquid phase to superheat steam at specified pressure by addition of heat. The tubes are operated continuously at high temperature due to the formation of scale which has lower conductivity than that of steel. The scale can be formed for various reasons of which tube geometries, flue gas and steam temperature are prominent. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. In this investigation an iterative technique was used to determine the temperature distribution across the tube with the increase of operating time. The operating time was considered up to 160,000 hours. The remaining life of the steam generator tube was found by finding hoop stress and Larson Miller Parameter from the Larson Miller Parameter curve for SA213-T22 material. The remaining life of the steam generator tube was used to find cumulative creep damage. By utilizing finite element modelling software, ANSYS 9/ ANSYS 11 the temperature distribution across the steam generator tube was evaluated. The temperature distribution along with Larson Miller Parameter predicted the oxide scale thickness. It was also observed that different input parameters have pronounced affect on the formation of oxide scale inside the steam generator tube. By increasing the heat transfer rate across the wall, the oxide scale thickness was increased more rapidly than normal condition. It was also observed that due to formation of scale the thermal conductivity in the boiler tubes was affected and the remaining life of boiler tubes was decreased and accelerated creep damage.

Hydrogen–Metal Systems: Fluorinated Metal Hydrides

In this review article the electrochemical hydrogen storage properties, the activation rate, and kinetic properties of different hydrogen storage alloys like AB 5 , AB 2 , AB and A 2 B are investigated when fluorinated. Fluorination can improve the surface structure and catalytic activity according to the requirements for the practical use. However, fluorination can improve only the kinetic problems related to the surface of alloys of AB 5 , AB 2 , and A 2 B but not the thermodynamic properties. The major general features of fluorination are: the removal of oxide layers, fluoride formation, enhanced specific surface area, stable surface against impurities and alkaline electrolyte, low surface reaction.

Corrosion of Metals: Overview

Abstract Corrosion is the deterioration of materials due to chemical reaction with the environment. It is reverse extractive metallurgy, which is dependent on temperature and concentration of environment. Other factors such as stress and erosion also affect the corrosion rate. This article is limited on reviewing different types of corrosion for metals and its alloys. The annual corrosion costs range from 1 to 5% of GNP for any nations. The impact of corrosion is not only related with cost but also with safety hazards and life losses. Hence, proper action must be taken to control and prevent corrosion.

Energy Efficiency of Biogas Produced from Different Biomass Sources

Malaysia has different sources of biomass like palm oil waste, agricultural waste, cow dung, sewage waste and landfill sites, which can be used to produce biogas and as a source of energy. Depending on the type of biomass, the biogas produced can have different calorific value. At the same time the energy, being used to produce biogas is dependent on transportation distance, means of transportation, conversion techniques and for handling of raw materials and digested residues. An energy systems analysis approach based on literature is applied to calculate the energy efficiency of biogas produced from biomass. Basically, the methodology is comprised of collecting data, proposing locations and estimating the energy input needed to produce biogas and output obtained from the generated biogas. The study showed that palm oil and municipal solid waste is two potential sources of biomass. The energy efficiency of biogas produced from palm oil residues and municipal solid wastes is 1.70 and 3.33 respectively. Municipal solid wastes have the higher energy efficiency due to less transportation distance and electricity consumption. Despite the inherent uncertainties in the calculations, it can be concluded that the energy potential to use biomass for biogas production is a promising alternative.