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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

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1013-9826

Key engineering materials/Journal Key engineering materials
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    Role of Combustion Energy in Laser Cutting of Austenitic Stainless Steel

    A. RaufA. HussainR. AkhterW.A. Farooq...
    P.81-87页
    查看更多>>摘要：Cutting of austenitic stainless steel of 0.5mm and 2mm thickness with CO_2 laser has been carried out using oxygen, nitrogen and compressed air as assist gases. It has been observed that when oxygen is used as assist gas, the contribution of combustion energy was found to be 60 to 80 % more as compared to the other two types of assist gases. The cutting speed for 0.5 mm sheet was about 11 times where as for 2 mm stainless steel it was around 16 times. The role of combustion energy were theoretically calculated and compared with experimental results and found to be in good agreement.
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    • NETL
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    To Study the Mechanical Properties of Unidirectionally and Cross Rolled Ni-Cu Alloy Produced in VIM

    M. AfzalM. AjmalT.Z. Butt
    P.88-95页
    查看更多>>摘要：Ni-Cu alloy was developed by melting in a vacuum induction furnace using pure elements i.e., Ni, Cu, Fe, Si, Mn and Cr. Four heats of approximately 4 kg each were prepared. All the heats have been casted in an ingot of 10 cm long and 5 cm in diameter in vacuum. These ingots were hot forged at a temperature of 900℃ to break down the cast dendritic structure. All forged plates were cut into two halve. One half was rolled in unidirectional while other was rolled in multiple directions (cross rolling). During rolling after every 25 % reduction, the cold rolled samples were annealed at a temperature of 900℃ for one hour. Each plate was cold rolled to a final thickness of 0.345 mm. Half of these rolled plate produced either by cross rolling or unidirectional rolling were annealed at 900℃ for 20 minutes. The mechanical properties of each rolled plate in cold reduction and in annealed were also measured.Unidirectional rolling and cross rolling has almost similar mechanical properties. The annealing of cross rolled and unidirectional rolling drastically reduced the yield strength. It was observed that the Ni-Cu alloy produced has slightly lower yield and ultimate tensile strength compared to the values reported in standards of Monel-400. However, it is within the acceptable range to be used for the various applications.
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    Substrate Temperature Effect on Optical Constants of Gd_2O_3 Thin Films

    M.F. WasiqM.Y. NadeemF. CholletS. Atiq...
    P.96-101页
    查看更多>>摘要：Effect of substrate temperature on lanthanide oxide material Gd_2O_3 thin films deposited by e-beam evaporation has been reported in the present work. Optical properties and surface morphology of as deposited films have been measured using spectrophotometry and atomic force microscopy respectively. Optical constants such as refractive index, extinction coefficient, band gap and Urbach energy have been determined by analysis of experimentally recorded absorption, transmittance and reflection data in wavelength range 200-800nm. Optical band gap energy shows decreasing while Urbach energy shows increasing behavior with increasing temperature. Extinction coefficient and refractive index with varying wavelengths are also calculated. Surface topographies of all samples are studied by atomic force microscope (AFM) and root mean square (RMS) value of roughness is observed increasing with increasing substrate temperature.
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    Tailoring of Multiferroic Properties of BiFeO_3 Thin Films by Cation Substitution

    M.S. AwanA.S. BhattiS. QingC.K. Ong...
    P.102-108页
    查看更多>>摘要：Mn-doped multiferroic BiFeO_3 (BFMO) thin films were deposited on LaNiO_3(LNO)/SrTiO_3(STO)/Si(100) substrates by pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) showed that films were bicrystalline single phase with (110) preferential orientation. Multiferroic top layer and oxide bottom electrode (LNO) epitaxially followed the buffer layer (STO). Oxygen partial pressure during deposition proved to be critical for phase formation, crystallinity and resistivity of the films. Atomic force microscopic (AFM) studies revealed the smooth, dense and crack free surfaces of the films. Cross-section view of the multilayers by field emission scanning electron microscope (FE-SEM) gave their thickness. Mn substitution resulted in the increase of magnetization saturation, coercive field and clarity of hysteresis loop. The magneto-electric (ME) effect was demonstrated by measuring the dielectric response in a varying magnetic field. Optimally deposited BFMO films show saturated P-E loop.
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    An Investigation into the Effects of Substrate Temperature on Magnetic Properties of RF Sputtered NiFe Films

    P. AkhtarT.J. AliR. Mahmud
    P.109-115页
    查看更多>>摘要：The paper describes results of investigation on sputtered NiFe Films to determine the sputter deposition condition that could produce magnetic field sensors with the desired magnetic properties. The magnetic materials used in such devices should have a low coercive force, a low anisotropy field and a low magnetization dispersion, alpha_(50) .The results of systematic investigation of radio-frequency (RF) sputtered, RF biased, 82-18 % NiFe films showed (ⅰ) Improved Kobelev methods were applied to magneto-optic measurement techniques, suppress the magnetization ripples when subjected under the application of dc field, (ⅱ) Anisotropy field results indicated an inverse trend with increasing substrate temperature (ⅲ) the experimental measurements on magnetization dispersion relatively constant up to 200 ℃ with alpha_(50) approximately 1.2°, it then increases more sharply to about 3.5° at 400 ℃ substrate temperature. The work also provide understanding of the effects on the magnetic properties of sputtered magnetic films that is very limited as current literature is almost entirely limited to evaporated magnetic films.
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    Synthesis of Multiwall Carbon Nanotube and Their Thin Films for Infrared Sensor Applications

    M. MansoorS. SiddiqueM.M. Asim
    P.116-122页
    查看更多>>摘要：Catalytic synthesis of carbon multiwall nanotubes (MWCNT) was carried out by chemical vapor deposition. Synthesis temperature was 750℃, whereas, iron nitrate and ethanol was used as catalyst and carbonaceous source, respectively. The carbon nanotubes produced were multiwall and tangled in nature with nominal diameter of 50nm and length ～2.5μm. These MWCNTs were purified by an acidic treatment and subsequently functionalized by chemical oxidation.After synthesis and functionalizing, a thin film of MWCNT was deposited on quartz substrates which were coated with copper electrodes. Investigations showed that during film preparation a bridging of CNTs was established between the copper electrodes which were further revealed to be semi-conductive by current Vs voltage testing. The discernable characteristics included batter conduction and infrared photocurrent responses.
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    Structural and Texture Studies of PbS Thin Film

    S.K. MehmoodS. ZamanK. AhmedM.M. Asim...
    P.123-129页
    查看更多>>摘要：In this study, we report on the structural parameters and texture development which occurred during deposition and annealing of PbS films and their effect on optical properties. The films under study were deposited on glass substrates through chemical bath method. The reactive substances used to obtain the PbS layers were lead accetae trihydrated, thiourea and hydrazine hydrate. The films were prepared with one molar bath concentration and for various deposition times. The data showed that as-prepared and annealed thin films are polycrystalline with cubic structure and predominantly textured along <100>. Results showed that thinner films are more prone to post deposition heat treatments as compared to thicker ones. Deposition parameters and thermal treatment strongly influence the optical properties of PbS films.
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    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Laser Surface Hardening of GCr15 Bearing Steel Ring

    R. AkhterA. HussainW.A. FarooqM. Aslam...
    P.130-136页
    查看更多>>摘要：Surface hardening of GCr15 bearing steel ring was carried out using CW CO_2 laser. The laser power used was in the range of 300 to 500 Watts. A rectangular beam shape was used to cover the area to be hardened. A three fold increase in the hardness of the transformed zone was achieved. The depth of hardness attained was around 1mm. The depth and width of the laser treated zone were studied as function of laser power and working speed for specific spot size. The microstructure of the transformed zone is also discussed. Subzero cooling technique was applied to convert the retained austenite to martensite.
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    • NETL
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    • Trans Tech Publications Ltd

    Laser Surface Alloying of Ni-Co Electroplated Low Carbon Steel

    A. HussainR. AkhterW.A. FarooqM. Aslam...
    P.137-143页
    查看更多>>摘要：Laser surface alloying of Ni-Co electroplated steel using 900 W CW CO_2 laser to develop Fe-Ni-Co alloy on the surface is reported. Fe-Ni-Co alloys of different compositions are produced by varying the working speed from 0.25 m/min to 3m/min and laser spot size from 0.6 mm to 5mm. The development of microstructure in the melted zone is analysed in terms of composition variation and cooling rate. The microhardness of newly formed alloys reported here are three times higher as compared to base metal. Martensite is observed in the laser modified zone.
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    Effect of Deposition Parameters and Annealing on the Morphology and Optical Properties of Pbs Thin Films

    S. ZamanM.M. AsimS. SiddiqueS.K. Mahmood...
    P.144-151页
    查看更多>>摘要：Polycrystalline PbS thin films are being potentially used in different optical applications. Optimization of their optical response is always an area of interest. In the current paper, we report on the effect of deposition parameters such as concentration of reactants, dipping time and post deposition heat treatment on the grain size, structure, resistivity and optical response. Spontareous reaction of lead acetate and thiourea in aqueous hydrazine hydrate was used for depositing PbS thin films on glass substrates. The deposition temperature was kept close to 100℃. Deposition of PbS films at such a high temperature and strong reactant concentrations has not been much emphasized in literature. The characterization of physical and optical properties was done by using XRD, SEM, DSC, dual beam spectrophotometer and two probe methods for resistivity measurement. Mean grain size and surface disorder increased with increasing reactant concentrations and dipping time. However, the effect was less prominent with increasing concentration of reactants than the deposition time. The structural features such as crystallite size, structure and film thickness directly correspond to photosensitivity and optical properties of thin films. Annealing affected the electronic properties considerably and lowered the band gap of material but did not cause any appreciable change in structure except smoothening of the grain boundaries to certain extent.
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