bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, Crystallization Behavior and Surface Modification of Ni-Cr-Si-Fe Amorphous Alloy
Authors: Iqbal Muhammad , Akhter J.I. , Rajput M.U. , Mahmood K. , Hussain Z. , Hussain S. , Rafiq M.
Published: May 2012

A quaternary Ni86Cr7Si4Fe3 amorphous alloy was synthesized by melt spinning technique. Surface modification was done by electron beam melting (EBM), neutron irradiation and γ-rays. Microstructure of as cast, annealed and modified samples was examined by scanning electron microscope. Crystallization behavior was studied by annealing the samples in vacuum at different temperatures in the range 773-1073 K. Techniques of X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for characterization. Differential scanning calorimetry (DSC) was conducted at various heating rates in the range 10-40 K/min. Thermal parameters like glass transition temperature Tg, crystallization temperature Tx, supercooled liquid region ΔTx and reduced glass transition temperature Trg were measured. The Ni86Cr7Si4Fe3 alloy exhibits wide supercooled liquid region of 60 K indicating good thermal stability. The activation energy was calculated to be 160±4 kJ/mol using Kissinger and Ozawa equations respectively which indicates high resistance against crystallization. The XRD results of the samples annealed at 773 K, 923 K, 973 K and 1073 K/20 min show nucleation of Ni2Cr3 and NiCrFe crystalline phases. Vickers microhardness of the as cast ribbon was measured to be 680.. About 30-50 % increase in hardness was achieved by applying EBM technique.
Acoustic Properties of Ho2Si2O7 Single Crystal Investigated by Brillouin Light Scattering
Authors: Shabbir Ghulam , Maqsood Asghari , Izhar-ul-Haq Izhar-ul-Haq
Published: May 2012

Micro-Brillouin light scattering experiments were performed on flux grown D-type (monoclinic, P21/c) Ho2Si2O7 single crystal from room temperature to 850 K. Both the hypersonic velocity (VLA) and related elastic constant (c33) of the longitudinal acoustic phonons propagating along 001-direction showed a small dispersion at T565 K whereas the same could not be observed clearly in attenuation/damping. The overall temperature dependent behavior of elastic constant and hypersonic velocity was attributed to the lattice anharmonicity of the crystal in the investigated temperature range.
Characterization of Physical Properties of Thermally Evaporated Doped CdS Thin Films for Photovoltaics
Authors: Tariq G.H. , Anis-ur-Rehman Muhammad
Published: May 2012

Polycrystalline thin films of Cadmium Sulfide (CdS) have been extensively studied for application as a window layer in CdTe/CdS and CIGS/CdS thin film solar cells. Higher efficiency of solar cells is possible by a better conductivity of a window layer, which can be achieved by doping these films with suitable elements. CdS thin films were deposited on properly cleaned glass substrate by thermal evaporation technique under vacuum2×10-5mbar. Films were structurally characterized by using X-ray diffraction. The X-ray diffraction spectra showed that the thin films were polycrystalline in nature. Aluminum was doped chemically in as deposited and annealed thin films by immersing films in AlNO33.9H2O solutions respectively. Comparison between the effects of different doping ratios on the structural and optical properties of the films was investigated. Higher doping ratios have improved the electrical properties by decreasing the resistivity of the films and slightly changed the bandgap energy Eg. The grain size, strain, and dislocation density were calculated for as-deposited and annealed films.
Synthesis and Thermoelectric Studies in Cr Doped Cobalt Ferrites Nano Particles
Authors: Anis-ur-Rehman Muhammad , Ansari Mariam , Mughal Zeb Un Nisa , Awan M.S. , Maqsood Ashari
Published: May 2012

Samples of Cr doped cobalt ferrite were prepared by co-precipitation route. These particles were characterized by X-ray diffraction (XRD) at room temperature. The structural properties were observed before and after sintering. The FCC spinel structure was confirmed by XRD patterns of the samples. The crystallite sizes lie in the range of 37-60 nm. DC electrical properties as a function composition were measured. Scanning electron microscopy was used in order to investigate the surface morphology of the prepared samples. The system for thermoelectric power measurement was designed, developed and calibrated in the laboratory. The room temperature thermoelectric power was measured for the prepared samples. The magnitude of Seebeck coefficient depends on the composition and resistivity of the samples. The obtained values of Seebeck coefficient for CoFe2O4 are in good agreement to the reported values. Determined values of Seebeck coefficient for other studied compositions are an addition to the literature.
Role of Synthesis Parameters on Structural and Electrical Properties of M-Type Hexa-Ferrites
Authors: Asghar G. , Nasir S. , Awan M.S. , Tariq G.H. , Akram M. , Anis-ur-Rehman Muhammad
Published: May 2012

Phase purity, particle size and its distribution contributes a lot to the physical properties of M-type hexa-ferrites. These parameters are strongly influenced by the variation in synthesis parameters. In the present work, effect of synthesis parameters such as molar ratio (Fe/Sr) and volume rate of addition of precipitating agent on M-type hexa-ferrite (SrFe12O19) prepared by co-precipitation method have been investigated systematically. The molar ratio (Fe/Sr) in SrFe12O19 was varied as 12, 11, 10, 09, and 08. X-ray diffraction analysis revealed that molar ratio does not affect the phase purity. X-ray diffraction analysis of the samples prepared with different volume rate of addition of precipitating agent indicated that phase purity and micro-structural properties of SrFe12O19 are greatly influenced by the above synthesis parameter. High volume rate of addition of precipitating agent resulted in high phase purity, smaller particle size, and narrow particle size distribution.
Effect of Heat Treatment on Deformation Induced Martensite in Austenitic Stainless Steel
Authors: Nusair Khan Aamer , Shah Syed Khalid , Mehmood Khalid
Published: May 2012

Austenitic stainless steel with submicron gain size has been attracted due to fine structural control of mechanical properties. In order to achieve a submicron grain size, meta-stable austenitic steel AISI 304 is severely cold deformed and then annealed to different heat treatment cycles. The heat treated samples were then tested for metallurgical phase change, texture components and hardness. It was observed that at 750°C, all the martensite transformed completely into austenite. Further, at the same temperature, it was observed that the texture component {221}<232> was the dominant texture component.
Viscoelastic Response of HTPB Based Solid Fuel to Horizontal and Vertical Storage Slumping Conditions and it's Affect on Service Life
Authors: Nawaz Qamar , Nizam F.
Published: May 2012

Frequent use of solid fuels as thrust generating energy source in modern day space vehicle systems has created a need to assess their serviceability for long term storage under various conditions. Solid fuel grain, the most important part of any solid fuel system, responds viscoelastically to any loading condition. For the assessment of the service life of any solid fuel system, the solid fuel grain has to be structurally evaluated in applied storage conditions. Structural integrity of the grain is exceptionally significant to guarantee the successful operation of the solid fuel system. In this work, numerical simulations have been performed to assess the mechanical stresses and strains induced in an HTPB based solid fuel grain during service life employing ABAQUS standard FEA software using 4-node bilinear quadrilateral elements. For finite element analysis (FEA), typical 2-D and π/nth axisymmetric section of 5-point (n) star grain geometry is considered. Mechanical loads include the horizontal or vertical 1-g (solid fuel weight) storage condition. The simulation results are compared with the analytical results for the same grain geometry. Analytically measured slump deflections in grain segment at various storage times have been found in good relation with the FEA based simulation results. This proves the validity of the procedure adopted and is helpful in assessment of the service life of solid fuel systems.
Microstructures, Electrical and Magnetic Properties of Zn Doped Co Nanoferrites
Authors: Akram M. , Anis-ur-Rehman Muhammad , Mubeen M. , Ali M.
Published: May 2012

Non toxicity, bio compatibility and nanometer sizes regime which is comparable to the size of a cell, makes nanocrystalline Co ferrites particles very proficient. In the present research Zn doped cobalt ferrites were prepared by the chemical co-precipitation method and characterized by X-ray diffraction (XRD) at room temperature for structural analysis. X-ray diffraction patterns confirmed the FCC spinel structure of synthesized particles. Crystallite sizes were calculated from the most intense peak (311) using the Debye-Scherrer formula. The obtained crystallite sizes were in nanometer range for all the samples synthesized at reaction temperature of 70°C. Then samples were sintered at 550°C for 2 hours, characterized again by X-ray diffraction at room temperature. The crystallite sizes and lattice constants for all the samples were calculated again from the data obtained by XRD. DC electrical resistivity and AC electrical transport properties were analyzed. The magnetic properties such as coercivity (Hc) and remanence (Mr) of Co1-xZnxFe2O4 for x = 0.0, 0.2, 0.4 were measured at room temperature by vibrating sample magnetometer. Coercivity and remanence were found maximum with minimum value of Zn in Co1-xZnxFe2O4. Observed structural and conduction properties of synthesized nanomaterials were correlated.
Preparation, Structural and Electrical Properties of Nanocrystalline Zr-Mn Cobalt-Ferrite Synthesized by the Co-Precipitation Method
Authors: Khan K.
Published: May 2012

The present study describes the preparation, structural and electrical characterization of nanosized Zr-Mn cobalt-ferrites. The nominal compositions CoFe2-2xZrxMnxO4 (0.10.4) have been synthesized by the co-precipitation method. These nanopowder products were sintered in furnace at temperature of 800 °C for 8 hour with a heating rate of 10οC/min to obtain these ferrites. The nanopowder was evaluated using XRD, FT-IR and SEM. The XRD data showed that all the samples are of single phase and the crystallite size is found in the range of 2630 nm. The lattice constant (a), X-ray density (dx), porosity (P) and bulk density (dm) are also calculated from XRD data. FT-IR study confirms the presence of ferrite functional groups. The IR spectra of Zr-Mn ferrite system have been analyzed in the frequency range 400650 cm-1. It revealed two prominent bands υ1 and υ2 which are assigned to tetrahedral and octahedral metal complexes, respectively. The position of the highest frequency band is around 550 cm-1 while the lower frequency band is around 425 cm-1. The structural properties are also analyzed on scanning electron microscopy (SEM) at room temperature. Additionally, the dc electrical resistivity decreased with the rise in temperature for all the samples, showing a semiconductor like behavior. From the dc electrical resistivity the activation energy and drift mobility are determined. Both the drift mobility and activation energy increase with a rise in x.
Structural and Thermal Characterization of Polymorphic Er2Si2O7
Authors: Maqsood Ashari
Published: May 2012

The first measurement of thermal transport properties on the polycrystalline D-Er2Si2O7 have been made in the temperature range 77-300K. Both the thermal conductivity and the thermal diffusivity follow modified Euckens law in this temperature region. The Transient Plane Source technique (TPS) has been used to measure thermal conductivity and thermal diffusivity simultaneously.
Laser Induced Backside Dry Etching of BK-7 and Quartz in Vacuum
Authors: Hamdani A.H. , Ansar A. , Akhter R. , Aslam M.
Published: May 2012

Laser Induced Plasma Assisted Ablation (LIPAA) has been used to carry out back side dry etching/ablation of different optical glasses under vacuum. It is observed that etching depth increases with decrease in target-substrate gap and becomes maximum (50 μm) at zero gap size for steel-quartz pair. The maximum ablation depth for brass-quartz pair was 25 μm. The effects of laser power on etching depth and laser scan speed has also been reported.
Comparative Study of Temperature Dependent Barrier Heights of Pd/ZnO Schottky Diodes Grown along Zn- and O-Faces
Authors: Asghar M. , Mahmood Khalid , Ali Adnan , Hasan M.A.
Published: May 2012

In this study, the effect of polar face on Schottky barrier diodes has been investigated. Two samples of ZnO were grown hydrothermally under similar growth conditions. The Palladium (Pd) metal contacts of area 0.78 mm2 were fabricated on both faces and were studied comprehensively using DLS-83 Deep Level Spectrometer over temperature range of 160K330K. The current-voltage (IV) measurements revealed that the ideality factor n and barrier height ϕB were strongly temperature dependent for both faces (Zn and O-face) of ZnO, indicating that the thermionic emission is not the dominant process, which showed the inhomogenity in the barrier heights of grown samples. This barrier height inhomogenity was explained by applying Gaussian distribution model. The extrapolation of the linear ϕap verses n plot to n = 1 has given a homogeneous barrier height of approximately 0.88±0.01 eV and 0.76±0.01 eV for Zn and O-faces respectively. ϕap versus 1/T plot was drawn to obtain the values of mean barrier height for Zn and O-face (0.88±0.01 eV, 0.76±0.01 eV) and standard deviation (δs) (0.015±0.001 V, 0.014±0.001 V) at zero bais respectively. The value of δs for the Zn-face is larger than O-face, showing that inhomogenity in the barrier heights is more in the sample grown along Zn-face as compared to the sample grown along O-face.
A Comparison of the Electrical and Thermal Behavior of ZrO2-Ni Interpenetrating Phase Composite Produced by Microwave and Conventional Sintering
Authors: Kanwal Tehreem , Shahid Rub Nawaz , Tariq Naeem Ul Haq , Ali Fahad , Rafiq M. A. , Iqbal Muhammad , Akhter J.I. , Hasan Bin Awais
Published: May 2012

The ceramic-metal composites that have all phases continuous throughout the structure are known as Interpenetrating Phase Composites (IPCs) and they have many applications in various fields. In this investigation ZrO2-Ni IPCs of varied compositions were synthesized using tubular furnace and microwave furnace routs. Samples were Characterized using BET surface area, Pycnometer density, dilatometry and scanning electron microscopy. The Electrical parameters of the composites were measured using impedance spectrometer. Results indicate that threshold percolation reached at 40 volume percent of Ni in both cases. Moreover, no significant difference was observed in BET surface area and CTE of composites prepared by conventional and microwave sintering processes.
Single Step Heat Treatment Cycle for Development of Isotropic Fe-Cr-Co Magnets
Authors: Akbar Shakeel , Ahmad Z. , Awan M.S. , Sarwar M.N. , Farooque M.
Published: May 2012

This study is focused on the development of isotropic Fe-Cr-Co based permanent magnets. Two compositions Fe-25Co-30Cr-3.5Mo-0.8Ti-0.8 and Fe-24 Co-32Cr-0.5Si-0.8V-0.8Ti were tried to optimize by adjusting heat treatment cycle. A modified single step heat treatment cycle was established which made processing easy and quick. Alloys were prepared in tri-arc melting furnace under inert atmosphere of Argon. Samples were solution treated at 1250 °C for 5 hours followed by water quenching. Then a spinodal decomposition heat treatment cycle in the temperature range 620 645 °C was applied in order to produce magnetism in this material. Samples were characterized for metallographic, chemical, structural and magnetic properties using Optical microscope, Scanning electron microscope equipped with Energy dispersive spectrometer, X-ray diffractometer and DC magnetometer. This study reveals that magnetic properties are sensitive to the spinodal decomposition temperature. Only + 5 °C change in temperature from optimum temperature can cause remarkable attenuation in magnetic properties. Magnetic properties of the alloys were achieved by controlling the spinodal decomposition temperature and subsequent cooling rate. The best magnetic properties in Mo and V containing alloys were obtained as 880 Oe (Hc), 7960 G (Br), 2.3 MGOe (BHmax) and 700 Oe (Hc), 7750 G (Br), 1.8 MGOe (BHmax), respectively.
High Temperature Oxidation Behaviour of Nickel Based Nanostructured Composite Coatings
Authors: Farrokhzad M.A. , Khan T.I.
Published: May 2012

The electrodeposition of nanostructured composite coatings involves the co-deposition of nanosized oxide particles such as TiO2, Al2O3 and Y2O3 into a corrosion resistant metal matrix such as nickel to improve the high temperature oxidation and erosion resistance of nickel coatings. The technique has several advantages over other methods for producing nanostructured composite coatings such as thermal metal spraying. Some of the main advantages are lower cost for equipment setup and lower material cost and the ease with which the process can be controlled. Although electrodeposited nanostructured coatings are being developed for various aerospace and marine applications, they have not yet been considered for protecting surfaces of components and piping that is used in technologies for the oil sands industry such as the In-Situ Combustion (ISC) process. The challenge with in-situ combustion oil production is that the combination of high temperature combustion gases and the presence of moving sand particles create an extremely severe environment in which high oxidation and erosion rates are expected. As a result there is a need to develop function specific coatings that can withstand both high temperatures and erosive environments in the oil sands industry. This paper presents results of high temperature oxidation behaviour of nickel coatings containing two types of nanosized oxide dispersions (TiO2 and Al2O3). High temperature oxidation tests were conducted in dry air for 500°C and 700°C. The oxidized specimens were examined by metallographic surface analysis and surface composition techniques such as Scanning Electron Microscopy (SEM), Wavelength Dispersive X-Ray Spectroscopy (WDS). The effects of nanosized oxide particles on high temperature oxidation behavior of nickel coatings have been studied. The results show an improvement in the high temperature oxidation resistance of nickel coatings dispersed with Al2O3 and TiO2.
Influence of Contact Materials on Phenomena in a Short Electrical Arc
Authors: Kharin S.N. , Sarsengeldin M.
Published: May 2012

Investigation of transition phenomena accompanying the evolution of metallic phase of electric arc into gaseous phase is very important for the further progress in such fields as plasma technologies, electrical apparatus, plasmatrons and other technical applications. Some aspects of this transition are considered in presented paper on the base of mathematical model described dynamics of phenomena in the arc column, near-electrode zones, anode and cathode solids. Cathode and anode phenomena such as ion bombardment, thermionic emission, inverse electron flux, evaporation, radiation, heat conduction etc. are considered in dependence on time, current, opening velocity, parameters of the gas and contact materials. The conditions of the arc transition from one phase to another are formulated in terms of above characteristics and increasing of gas ionization level. Special experiments with two contacts materials, and have been carried to verify the mathematical model. The results of calculation and experimental data enables us to conclude that in metallic arc phase (short arc length), which is characterized by material transfer from the anode to the cathode, the erosion of contacts is considerably small than erosion of contacts both for resistive and inductive circuits, while in gaseous arc phase (long arc length) with opposite material transfer the rate of erosion depends on the inductance. If the inductance, then contacts have smaller erosion in comparison with contacts, however for inductive circuits situation is quite different, thus use of contacts in the case of long arcs burning in gaseous phase is more preferable. It was found also that the addition of niobium diselenide (1%) and tantalum (5%) into silver contact material which are sublimating into arc plasma enables to change ionization potential, that leads to decreasing of the arc temperature, arc duration and contact erosion.
Proficient Ni-Zn-Cr Ferrites: Synthesis and Characterization
Authors: Nasir S. , Malik M.A. , Asghar G. , Tariq G.H. , Akram M. , Anis-ur-Rehman Muhammad
Published: May 2012

Ni-Zn ferrite nanoparticles with Cr doping, having the general formula Ni0.5Zn0.5CrxFe2-xO4 (x = 0.1, 0.3, 0.5) were prepared by simplified sol-gel method and sintered at 750±5°C. The structural and magnetic properties of the samples sintered at 750±5°C were studied. From X-ray diffraction (XRD) patterns, it was confirmed that the samples have single phase spinel structure. The crystallite size was calculated from the most intense peak (3 1 1) using the Debye Scherrer formula and was found to be in the range of 29-34 nm. The scanning electron microscope images showed that the particle size of the samples were in the range 60-120nm. Quantum design PPMS model 6700 was used to study magnetic properties of these samples. The effect of Cr doping on the magnetic properties was explained on the basis of cations distribution in the crystal structure.
Effect of Sintering Temperature on Nanostructured Multiferroic BiFeO3 Ceramics
Authors: Shami M.Y. , Awan M.S. , Anis-ur-Rehman Muhammad
Published: May 2012

Nanostructured multiferroic BiFeO3 (BFO) powders were synthesized by using the co-precipitation method. Calcination of acquired powder was carried out at 400°C for 3h. Uniaxially pressed pellets were sintered at 500°C, 600°C, 700°C and 800°C for 2 hours in air. These samples were characterized for structural, thermal, electrical and magnetic properties. X-ray diffraction (XRD) confirmed the amorphous nature of the as driven powder and phase purity of the calcined BFO sample. The crystallite size varied with the sintering temperature from 52 to 70 nm. Sintering above 500°C induced impure phases due to oxygen vacancies and volumetric strain in crystal structure. Ferroelectric to paraelectric transition temperature TC~815°C was verified by the differential scanning calorimetry (DSC). Surface morphology and grain growth was observed using scanning electron microscopy (SEM). Electrical ac measurements were performed in the frequency range from 20 Hz to 3 MHz at room temperature. For a particular sample, capacitance decreased and susceptance increased with the increase of applied frequency signal. These parameters were increased with the increase of sintering temperature. Vibrating sample magnetometer (VSM) revealed the diverse weak ferromagnetic behavior for the samples sintered at different temperatures. Maximum coercivity (Hc~119.2 Oe) and maximum remnant magnetization (MR~2.1x10-3 emu/g) were obtained for the sample sintered at 700°C for 2hr.
Improved Hydrogen Desorption Kinetics of MgH2 Nanoparticles by Using TiC Nanocatalyst
Authors: Niaz N.A. , Hussain S.T. , Nasir S. , Ahmad I.
Published: May 2012

Magnesium hydride (MgH2) is considered to be a promising hydrogen storage material because of its high gravimetric and volumetric storage capacities. However, its slow kinetics and high desorption temperature (> 300 °C) limit the practical applications. We have selected TiC nanoparticles to modify the hydrogen storage properties of MgH2. First, Mg nanoparticles were synthesized by thermal desorption of bipyridyl complex of Mg and then MgH2 nanoparticles were obtained by hydriding the Mg nanoparticles. Composite mixtures (MgH2 + TiC) were prepared using high-energy ball milling. Structural analysis, morphology and particle size were investigated by X-rays diffractometer (XRD) and scanning electron microscopy (SEM) respectively. Hydrogen desorption properties of MgH2 was investigated with various amount of TiC nanocatalyst using differential scanning calorimetry (DSC) and seivertz type apparatus (PCT). Desorption kinetics were also studied by pressure composition isotherm (PCI). Results show that the product reveals good reversible hydrogen absorption-desorption cycles even at >150 °C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH2 could be understood by a modified first-order reaction model, in which the surface condition was taken into account.
Software Development for Specific Geometry and Safe Design of Isotropic Material Multicell Beams
Authors: Tariq M. Mushtaq , Ahmed Malik
Published: May 2012

Comparison of analytical results with finite element results for analysis of isotropic material multicell beams subjected to free torsion case is the main idea of this paper. Progress in the fundamentals and applications of advanced materials and their processing technologies involves costly experiments and prototype testing for reliability. The software development for design analysis of structures with advanced materials is a low cost but challenging research. Multicell beams have important industrial applications in the aerospace and automotive sectors. This paper explains software development to test different materials in design of a multicell beam. Objective of this paper is to compute the torsional loading of multicell beams of isotropic materials for safe design in both symmetrical and asymmetrical geometries. Software has been developed in Microsoft Visual Basic. Distribution of Saint Venant shear flows, shear stresses, factors of safety, volume, mass, weight, twist, polar moment of inertia and aspect ratio for free torsion in multicell beam have been calculated using this software.
The software works on four algorithms, these are, Specific geometry algorithm, material selection algorithm, factor of safety algorithm and global algorithm. User can specify new materials analytically, or choose a pre-defined material from the list, which includes, plain carbon steels, low alloy steels, stainless steels, cast irons, aluminum alloys, copper alloys, magnesium alloys, titanium alloys, precious metals and refractory metals. Although this software is restricted to multicell beam comprising of three cells, however future versions can have ability to address more complicated shapes and cases of multicell beams. Software also describes nomenclature and mathematical formulas applied to help user understand the theoretical background. User can specify geometry of multicell beam for three rectangular cells. Software computes shear flows, shear stresses, safety factors etc in all members of three cell beam, analyzes safety of proposed design and provides output with highlighted comments and graphics, in cases where safety factor in any element of multicell beam falls below 1.5. Results of this software were compared and verified with analytical calculations and Microsoft Excel spreadsheet. Development and use of this software provides an easy to use tool, for quick verification of different design cases in three cell beams composed of advanced isotropic materials. Furthermore, the methodology proposed is also useful for similar cases of research in reliable design studies and material analysis.
Material Selection for Design, Manufacturing and Application
Authors: Zaid A.I.O.
Published: May 2012

Developing a new engineering material product or changing an existing one requires new design selecting material and choosing appropriate and economical manufacturing processes.
These three main factors play a great role on the performance of the product in service. These items are independent and should not be performed in isolation from each other. With the great advancement of technology in the last decade and with the greater number of engineering materials which are now available, together with the increasing pressure to produce more economic and get reliable products an integrated approach which considers design, material selection and the appropriate manufacturing process makes it easier to achieve the optimum product that combines the functional requirements with the reliability at competitive cost.
These diverse activities or items are interdependent; therefore should not be considered in isolation from each other, for example, it is not sufficient that design of the product should satisfy the technical, safety and legal requirements, it must also be possible to be manufactured economically and to be sold at a competitive price and easily disposed at the end of its working life cycle. In this paper, the interaction of these items together in order to arrive to the optimum solution for a particular application are given and discussed.
Failure Analysis of a Helicopter's Main Rotor Bearing
Authors: Shahzad M. , Qureshi A.H. , Waqas H. , Hussain N. , Ali L.
Published: May 2012

Presented results report some of the findings of a detailed failure analysis carried out on a main rotor hub assembly, which had symptoms of burning and mechanical damage. The analysis suggests environmental degradation of the grease which causes pitting on bearing-balls. The consequent inefficient lubrication raises the temperature which leads to the smearing of cage material (brass) on the bearing-balls and ultimately causes the failure. The analysis has been supported by the microstructural studies, thermal analysis and micro-hardness testing performed on the affected main rotor bearing parts.
Combustion Characteristics of the Mustard Methyl Esters
Authors: Bannikov M.G. , Vasilev I.P.
Published: May 2012

Mustard Methyl Esters (further biodiesel) and regular diesel fuel were tested in direct injection diesel engine. Analysis of experimental data was supported by an analysis of fuel injection and combustion characteristics. Engine fuelled with biodiesel had increased brake specific fuel consumption, reduced nitrogen oxides emission and smoke opacity, moderate increase in carbon monoxide emission with essentially unchanged unburned hydrocarbons emission. Increase in fuel consumption was attributed to lesser heating value of biodiesel and partially to decreased fuel conversion efficiency. Analysis of combustion characteristics revealed earlier start of injection and shorter ignition delay period of biodiesel. Resulting decrease in maximum rate of heat release and cylinder pressure was the most probable reason for reduced emission of nitrogen oxides. Analysis of combustion characteristics also showed that cetane index determined by ASTM Method D976 is not a proper measure of ignition quality of biodiesel. Conclusion was made on applicability of mustard oil as a source for commercial production of biodiesel in Pakistan. Potentialities of on improving combustion and emissions characteristics of diesel engine by reformulating biodiesel were discussed.
Role of Equiaxed Primary Alpha (α׳) and Mechanical Properties of Ti-6Al-4V Alloy
Authors: Ahmad A. , Ali Amjad , Awan G.H. , Ghauri Khalid Mehmood , Aslam R.
Published: May 2012

The paper presents the role of equiaxed α׳ in the bimodal microstructure to attain an optimal combination of ductility and strength. The study revealed that the production of bimodal microstructure and volume fraction of equiaxed α׳ were reliant on the forging temperature and subsequent heat treatment. The Ti-6Al-4V alloy was forged in the two phase region and different heat treatment cycles were employed to get the desired bimodal microstructure and thus the combination of strength and ductility. The mechanical properties of fully lamellar microstructure were compared with bimodal microstructure containing equiaxed α׳. The experimental results showed that the amount of equiaxed α׳ in the bimodal microstructure was critical for achieving a well-balanced profile of mechanical properties.
Comparison of Structural Properties of Thermally Evaporated CdTe Thin Films on Different Substrates
Authors: Tariq G.H. , Anis-ur-Rehman Muhammad
Published: May 2012

The direct energy band gap in the range of ~1.5eV and the high absorption coefficient (~105cm-1) makes Cadmium Telluride (CdTe) a suitable material for fabrication of thin film solar cells. Thin film solar cells based on CdTe (~ 1cm area) achieved efficiency of 15.6% on a laboratory scale. CdTe thin films were deposited by thermal evaporation technique under vacuum 2×10-5mbar on glass and stainless steel (SS) substrates. During deposition substrates temperature was kept same at 200C for all samples. The structural properties were determined by the X-ray Diffraction (XRD) patterns. All samples exhibit polycrystalline nature. Dependence of different structural parameters such as lattice parameter, micro strain, and grain size and dislocation density on thickness was studied. Also the influence of the different substrates on these parameters was investigated. The analysis showed that the preferential orientation of films was dependent on the substrate type.
Surface Modification and Characterization of Bulk Amorphous Materials
Authors: Iqbal Muhammad , Akhter J.I. , Qayyum A. , Javed Y. , Rafiq M. , Khurram Aqeel Ahmed
Published: May 2012

Bulk metallic glasses (BMGs) are well known for their promising properties. Surface properties can be further improved by using certain techniques such as electron beam melting (EBM), laser beam melting (LBM), ion irradiation, ion implantation and neutron irradiation. BMGs especially Zr-based BMGs have numerous applications as structural materials. In this manuscript, the results are presented on microstructural investigations and phase formations in Zr-based BMGs modified by using above mentioned techniques. Microstructure was studied by scanning electron microscopy (SEM). Phase analysis was done by X-ray diffraction (XRD) and confirmed by energy dispersive spectroscopy (EDS). Vickers hardness was measured and correlated with the microstructure. The phases identified in Zr-Cu-Al-Ni alloy samples modified by EBM, LBM and ion irradiation are Ni-Zr, NiZr2, CuZr2, Cu10Zr7 and Al2NiZr6. ZrSi2 phase was detected in Zr55Cu30Al10Ni5 and Zr65Cu17Ni10Al8 BMGs irradiated with Si+ (ions). About 20-35 % increase in hardness and elastic moduli was achieved by surface modification. Modifications of BMGs by electron and laser beams melted the materials surfaces while ion irradiation improved the mechanical properties of localized zones without melting.
Synthesis of Phase Pure Strontium Doped Lead Zirconate Titanate Nano Crystalline Powder by Sol-Gel Approach
Authors: Nawaz H. , Aftab S. , Shuaib Muhammad , Siddiq M.
Published: May 2012

Phase pure Strontium doped PZT (Pb0.96Sr0.04Zr0.53Ti0.47O3) was synthesized by sol gel process. Zirconium and Titanium alkoxides were used as starting materials and Lead (II) Acetate trihydrate was used as Pb source. The alkoxides mixture was stabilized by acetylacetonate. The vacuum dried gel was calcined at different temperatures to study the calcination temperature and the resulting samples were analyzed by DSC, TG and XRD. The powder remained amorphous until a temperature of 550°C. The morphology and composition of the powder was studied using EDX, stereomicroscope and high resolution SEM.
Effect of Post-Deposition Annealing Treatment on the Structural, Optical and Gas Sensing Properties of TiO2 Thin Films
Authors: Haidry A.A. , Durina P. , Tomasek M. , Gregus J. , Schlosser P. , Mikula M. , Truhly M. , Roch T. , Plecenik T. , Pidik A. , Zahoran M. , Kus P. , Plecenik A.
Published: May 2012

One of the potential applications of TiO2 is its use in gas sensor technology. The aim of this work was to study the gas sensing properties of TiO2 thin films in combination with the effect of post-deposition annealing treatment. Titanium dioxide thin films with thickness 100 nm were prepared by the reactive dc magnetron sputtering. The thin films were deposited on sapphire substrate from a titanium target in an oxygen atmosphere. The samples were then post-annealed in air in the temperature range 600 °C 1000 °C. Crystal structure, surface topography and absorption edge of the thin films have been studied by X-ray Diffraction technique, Atomic Force Microscopy and UV-VIS Spectroscopy. It was found that the phase gradually changed from anatase to rutile, the grain size and roughness tended to increase with increasing post-annealing temperature. The effect of these factors on gas sensing properties was discussed. For electrical measurements comb-like Pt electrodes were prepared by standard photolithography and the films were exposed to different concentrations of H2 gas up to 10000 ppm in synthetic air at various operating temperatures from 200 °C to 350 °C.
Characterization of Cold Rolled Austenitic Stainless Steel by Ultrasonic Longitudinal Velocity
Authors: Khan S.H. , Nusair Khan Aamer
Published: May 2012

Ultrasonic testing has a strong application in defect detection. An efficient tool for characterizing and life assessment of material structure and components by nondestructive ultrasonic velocity was developed about thirty years ago. Cold rolling results in increase in strength and hardness. The work discussed here is to study quantitative ultrasonic longitudinal velocity for characterizing a change in microstructure due to cold rolling in austenitic stainless steel samples. Samples were cold rolled upto 80 percent in 10 percent step. It was found that the use of velocity measurements is a useful quantitative and non-destructive tool for characterizing amount of cold rolled austenitic stainless steel.
Influence of Solid Particle Size on Burning and Mechanical Properties of AP/Al/HTPB Composites
Authors: Mehmood Z. , Khan Mohammad Bilal , Abbas T. , Ahmad Nasir M.
Published: May 2012

Mechanical and ballistics properties are a measure of the performance of AP/Al/HTPB composites. These properties are influenced by the characteristics of inorganic crystalline oxidizer and aluminum particles. This paper reports the effect of the particle size distribution on mechanical and burning properties of 87% solid loaded composites. Composites were fabricated by mixing the ingredients in the planetary mixer followed by curing at an elevated temperature for several days. Multimodal particle size distribution was used in which coarse to fine ratio was varied proportionally. The burning rate was measured using strand burner at various pressures. Mechanical properties of the composites were investigated by using tensile tester. Results revealed that tensile strength and the burning rate increased while elongation at maximum stress decreased with the increase in the quantity of fines oxidizer. Whereas the variation in the particle size of the aluminum do not have any pronounced effect on the burning as well as mechanical properties of the composite.
Development of Fe-Cr-Co Permanent Magnets by Single Step Thermo-Magnetic Treatment
Authors: Akbar Shakeel , Ahmad Z. , Awan M.S. , Farooque M. , Ali Amjad
Published: May 2012

The present work is focused on a new approach for the development of Fe-Cr-Co based permanent magnets. Fe-Cr-Co alloy was prepared by using tri arc melting technique under inert atmosphere of Argon. Solution treatment was done at a temperature of 1250°C for five hours followed by water quenching and then a single step thermo-magnetic treatment (TMT) was applied at predetermined cooling rates. The influence of TMT and cooling rates on the final magnetic properties of the alloy were investigated. The results reveal that microstructure and magnetic properties were sensitive to both cooling rates & TMT and can be optimized by controlling the processing conditions. The optimum magnetic properties in the alloy with two different cooling rates of 1°C per minute and 2°C per minute were obtained as (i) 1010 Oe (Hc), 9400 G (Br), 3.4 MGOe (BHmax) (ii) 810 Oe (Hc), 10590 G (Br), 3.6 MGOe (BHmax) respectively. The above method provides a quick and low cost manufacturing route for the Fe-Cr-Co based permanent magnets with comparable magnetic properties to that of Alnico with added advantage of having high ductility.
Failure Analysis of Engine Bearing
Authors: Qureshi I.N. , Ejaz Noveed , Rizvi S.A. , Farooque M.
Published: May 2012

An engine bearing was failed during service. During inspection, ball and races of rear bearing were found with wear marks. The bearing was subjected to metallurgical failure analysis. Inclusion level in the balls of bearing was observed higher; these inclusions were rich in Mo and V. The inclusions being the potential sites of the stress concentration caused the subsurface fatigue cracks in the bearing balls. The bearing was failed due to the severe spalling produced under subsurface fatigue leading to the subsequent wear of the raceways.
Piezoelectricity in 0-3 PZT-PVDF Nano Composites Prepared via a Modified Solution Casting Process
Authors: Aftab S. , Nawaz H. , Mirza M.S. , Shuaib Muhammad , Siddiq Muhammad
Published: May 2012

0-3 nanocomposites of PVDF with varying volume percents of strontium doped PZT have been synthesized using a combination of a modified solution casting process and the hot press technique. The nanocrystalline PZT used prepared from the sol gel route and was in the calcined state. An increase in the volume percent of PZT caused an increase in the dielectric constant, dielectric loss and piezoelectric charge coefficients. The experimental dielectric constants gave a perfect fit to the theoretical Furukawa model. However, no significant trend is perceived for the dielectric loss. SEM and XRD aided in determining the morphology and the crystalline phases in PVDF, PZT and PVDF/PZT composite. TG/DSC was done to confirm the percentage crystallinity of PVDF. A comparison with samples prepared from the conventional solution casting process has also been given. Composites prepared from the modified solution casting process using nanocrystalline strontium doped PZT give better piezoelectric properties as compared to earlier works.
Synthesis and AC Electrical Characterization of Co Doped Bismuth Manganite Nanoparticles
Authors: Akram Khush Bakhat , Dar M.S. , Faheem-ul-Hassan Faheem-ul-Hassan , Anis-ur-Rehman Muhammad
Published: May 2012

Multiferroic bismuth manganites (BiMnO3) possess both ferromagnetic and ferroelectric properties. Their electrical properties can be controlled by doping for useful applications. In this work single-phase cobalt doped bismuth manganite nanoparticles having general formula BiMn1-xCoxO3 (x=0, 0.2, 0.4, 0.6) were synthesized by co-precipitation method. Structural properties like lattice parameters and crystallite size of samples were determined by the data obtained by X-rays diffraction. The dielectric constant (ε) and dielectric loss tangent (tanδ) of samples were investigated as a function of frequency from 20Hz-3MHz using ac measurement data. For all the compositions dielectric constant was decreased with increasing frequency, however it increased with the increase in cobalt content. However cobalt addition causes a decrease in loss tangent as compared to pure BiMnO3 composition. The origin of this behavior is discussed in terms of Maxwell-Wagner and Koops model. Substitution of Mn with Co, in BiMnO3-based compounds is supposed to cause better properties in terms of tangent loss.
Effect of Air Plasma Spraying Parameters on WC-Co Cermet Coating
Authors: Afzal M. , Ajmal M. , Nusair Khan Aamer , Mehmood Khalid
Published: May 2012

WC-Co cermet coatings were produced on AISI 321 stainless steel samples by air plasma spraying system. In this regard, the coatings were deposited by varying the spraying distance i.e. 80 mm and 100 mm. It was observed that spraying distance play an important role on the final properties of the WC-Co cermet coating. The coatings were characterized by optical and electron microscopy, microhardness testing and X-Ray Diffractometry. A remarkable micro-structural difference was observed between the two coatings. It was observed that the coatings produced at 80 mm having more porosity and un-melted particles as compared to that produced at higher distance. Similarly, the change in concentration of metallurgical phases was also observed.
Influence of Degree of Deformation on Anisotropy in Mechanical Properties in Wrought Magnesium Alloy ZK60
Authors: Shahzad M. , Qureshi A.H. , Waqas H. , Hussain N.
Published: May 2012

A direct-chill (DC) cast magnesium alloys ZK60 has been forward-extruded at 300 °C in a single pass at two extrusion ratios (ER) 12 and 44, which correspond to a total degree of deformation (φ) of 2.5 and 3.8, respectively. The as-extruded microstructure in both cases consists of two colonies of grain sizes, i.e. about 15 µm and <5 µm, and highly deformed original grains which have not recrystallized. The crystallographic texture at both extrusion ratios consists of a predominant component accompanied by a relatively weaker component in the extrusion direction. Although, the qualitative crystallographic texture at both extrusion ratios remains fairly similar, a higher extrusion ratio gives a relatively weaker basal texture. A relatively higher degree of DRX and much lesser volume fraction of coarse grains (>25 µm) at higher extrusion ratios give significantly weaker strength differential effect (difference in tensile yield stress and compressive yield stress).
Measurement of Loose Powder Density
Authors: Akhtar S. , Ali A. , Haider Ali , Farooque M.
Published: May 2012

Powder metallurgy is a conventional technique for making engineering articles from powders. Main objective is to produce final products with the highest possible uniform density, which depends on the initial loose powder characteristics. Producing, handling, characterizing and compacting materials in loose powder form are part of the manufacturing processes. Density of loose metallic or ceramic powder is an important parameter for die design. Loose powder density is required for calculating the exact mass of powder to fill the die cavity for producing intended green density of the powder compact. To fulfill this requirement of powder metallurgical processing, a loose powder density meter as per ASTM standards is designed and fabricated for measurement of density. The density of free flowing metallic powders can be determined using Hall flow meter funnel and density cup of 25 cm3 volume. Density of metal powders like cobalt, manganese, spherical bronze and pure iron is measured and results are obtained with 99.9% accuracy.