Browsing by Author "Hussain, Tanvir"

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    Characterization and solderability of cold sprayed Sn-Cu coatings on Al and Cu substrates
    (Elsevier Science B.V., Amsterdam., 2010-12-31T00:00:00Z) Li, J. F.; Agyakwa, P. A.; Johnson, C. M.; Zhang, D.; Hussain, Tanvir; McCartney, D. G.
    Cold sprayed Sn-Cu coatings approximately 40 and 25 μm in average thickness were deposited on aluminium and direct bonded copper (DBC) substrates respectively. Both a statistical analysis of coating thickness and a roughness analysis of the coating/substrate interface and the coating surface were carried out for the as-sprayed coatings using scanning electron microscope images. The results obtained can be related to substrate types and spraying conditions. Tin oxide on the surfaces of the as-sprayed coatings was revealed by employing X-ray photoelectron spectroscopy analyses and transmission electron microscopy. It came from an oxide shell around feedstock powder particles and was only locally broken down during cold spraying. Although the tin oxide inhibited fluxless soldering, flux-supported reflow of cold sprayed Sn on the DBC substrate produced Cu/Sn/Cu solder joints that were acceptable for application in electronic packaging and interconnects. In general, measures which can avoid or remove the tin oxide are needed to achieve improved solder joints using cold sprayed Sn coatings as the solder layers.
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    Corrosion behavior of cold sprayed titanium coatings and free standing deposits
    (Springer Science Business Media, 2011-01-01T00:00:00Z) Hussain, Tanvir; McCartney, D. G.; Shipway, P. H.; Marrocco, T.
    Cold gas dynamic spraying can be used to deposit oxygen-sensitive materials, such as titanium, withoutsignificant chemical degradation of the powder. The process is thus believed to have potential for thedeposition of corrosion- resistant barrier coatings. However, to be effective, a barrier coating must notallow ingress of a corrosive liquid and hence must not have interconnected porosity. This study investigatedthe effects of porosity on the corrosion behavior of cold sprayed titanium coatings onto carbonsteel and also of free standing deposits. For comparative purposes, a set of free standing deposits was alsovacuum heat-treated to further decrease porosity levels below those in the as-sprayed condition.Microstructures were examined by optical and scanning electron microscopy. Mercury intrusion porosimetry(MIP) was used to characterize the interconnected porosity over a size range of micrometers tonanometers. Open circuit potential (OCP) measurements and potentiodynamic polarization scans in3.5 wt.% NaCl were used to evaluate the corrosion performance. The MIP results showed that in coldsprayed deposits a significant proportion of the porosity was sub-micron and so could not be reliablymeasured by optical microscope based image analysis. In the case of free standing deposits, a reduction ininterconnected porosity resulted in a lower corrosion current density, a lower passive current density, andan increase in OCP closer to that of bulk titanium. For the lowest porosity level, ~1.8% achievedfollowing vacuum heat treatment, the passive current density was identical to that of bulk titanium.However, electrochemical measurements of the coatings showed significant substrate influence when theinterconnected porosity of the coating was 11.3 vol.% but a decreased substrate influence with a porositylevel of 5.9 vol.%. In the latter case, the OCP was still around 250 mV below that of bulk Ti. Salt spraytests confirmed these electrochemical findings and showed the formation of surface corrosion productsfollowing 24-h exposure.
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    Corrosion performance of laser post-treated cold sprayed titanium coatings
    (Springer Science Business Media, 2011-06-01T00:00:00Z) Marrocco, T.; Hussain, Tanvir; McCartney, D. G.; Shipway, P. H.
    The recent development of cold spray technology has made possible the deposition of highly reactive,oxygen sensitive materials, such as titanium, without significant chemical reaction of the powder, modificationof particle microstructure and with minimal heating of the substrate. However, the presence ofinterconnected pathways (microscale porosity) within the deposit limits the performance of the metalliccoating as an effective barrier to corrosion and substrate attack by corrosive media is usually inevitable.The aim of the present study was to investigate the effects of processing, including a postspray lasertreatment, on the deposit microstructure and corrosion behavior. Commercially pure titanium (CP Ti)was deposited onto a carbon steel substrate, using a commercial cold spray system (CGTTM Kinetiks4000) with preheated nitrogen as both the main process gas and the powder carrier gas. Selected coatingswere given a surface melting treatment using a commercial 2 kW CO2 laser (505 Trumpf DMD). Theeffect of postdeposition laser treatment on corrosion behavior was analyzed in terms of pore structureevolution and microstructural changes. Optical microscopy, scanning electron microscopy, and x-raydiffraction were employed to examine the microstructural characteristics of the coatings. Their corrosionperformance was investigated using electrochemical methods in 3.5 wt.% NaCl (ASTM G5-94 (2004)).As-sprayed titanium coatings could not provide favorable protection to the carbon steel substrate in theaerated NaCl solution, whereas the coatings with laser-treated surfaces provided barrier-like properties.
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    High-temperature performance of ferritic steels in fireside corrosion regimes: temperature and deposits
    (Springer, 2016-11-17) Dudziak, T.; Hussain, Tanvir; Simms, Nigel J.
    The paper reports high temperature resistance of ferritic steels in fireside corrosion regime in terms of temperature and deposits aggressiveness. Four candidate power plant steels: 15Mo3, T22, T23 and T91 were exposed under simulated air-fired combustion environment for 1000 h. The tests were conducted at 600, 650 and 700 °C according to deposit-recoat test method. Post-exposed samples were examined via dimensional metrology (the main route to quantify metal loss), and mass change data were recorded to perform the study of kinetic behavior at elevated temperatures. Microstructural investigations using ESEM-EDX were performed in order to investigate corrosion degradation and thickness of the scales. The ranking of the steels from most to the least damage was 15Mo3 > T22 > T23 > T91 in all three temperatures. The highest rate of corrosion in all temperatures occurred under the screening deposit.
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    Large-scale manufacturing route to metamaterial coatings using thermal spray techniques and their response to solar radiation
    (Springer, 2021-07-04) Faisal, Nadimul Haque; Sellami, Nazmi; Venturi, Federico; Hussain, Tanvir; Mallick, Tapas; Muhammad-Sukki, Firdaus; Bishop, Alex; Upadhyaya, Hari; Katiyar, Nirmal Kumar; Goel, Saurav
    Metamaterials, an artificial periodic two- or three-dimensional configuration can change propagation characteristics of electromagnetic waves (i.e., reflection, transmission, absorption). The current challenges in the field of metamaterial coatings are their manufacturing in large scale and large length scale. There is a clear need to enhance process technologies and scalability of these. Thermal spraying is a method used to deposit small to large scale coatings where the sprayed layer is typically formed by successive impact of fully or partially molten particles of a material exposed to various process conditions. This work aims to investigate the feasibility to manufacture large scale metamaterial coatings using the thermal spray technique and examine their response to solar radiation. Two types of coatings namely, Cr2O3 and TiO2 were deposited onto various substrates (e.g., steel, aluminium, glass, indium tin oxide (ITO) coated glass) with a fine wire mesh (143 µm and 1 mm aperture sizes) as the masking sheet to manipulate the surface pattern using suspension high-velocity oxy-fuel thermal spraying (S-HVOF) and atmospheric plasma-sprayed (APS) methods, respectively. Post deposition, their responses subjected to electromagnetic wave (between 250 nm to 2500 nm or Ultraviolet (UV)-Visible (Vis)-Infrared (IR) region) were characterised. The additional microstructural characterisation was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), three-dimensional profilometry and optical spectroscopy. It is demonstrated that through novel application of thermal spray techniques, large scale manufacturing of metamaterial coating is possible, and such material can affect the electromagnetic wave propagation. Comparison between Cr2O3 and TiO2 coatings on aluminium substrates showed reduced three orders of reduced reflectance for Cr2O3 coatings (for 1 mm aperture size) throughout the spectrum. It was concluded that for a similar bandgap, Cr2O3 coatings on aluminium substrate will yield improved optical performance than TiO2 coating, and hence more useful to fabricate opto-electronic devices.
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    Resilient and agile engineering solutions to address societal challenges such as coronavirus pandemic
    (Elsevier, 2020-05-28) Goel, Saurav; Hawi, Sara; Goel, Gaurav; Thakur, Vijay Kumar; Agrawal, Anupam; Hoskins, Clare; Pearce, Oliver; Hussain, Tanvir; Upadhyaya, Hari M.; Cross, Graham; Barber, Asa H.
    The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious “Coronavirus Disease 2019” (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19.
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    Trends in fireside corrosion damage to superheaters in air and oxy-firing of coal/biomass
    (Elsevier Science B.V., Amsterdam., 2013-12-01T00:00:00Z) Hussain, Tanvir; Syed, A. U.; Simms, Nigel J.
    This paper compares the laboratory-based fireside corrosion tests on superheater/reheater materials in simulated air-firing combustion conditions with oxy-firing combustion conditions (with hot gas recycling before flue gas de-sulphurisation). The gaseous combustion environment was calculated based on a specific co-firing ratio of CCP with Daw Mill coal. The fireside corrosion tests were carried out using the “deposit recoat” test method to simulate the damage anticipated in specific environments. A synthetic deposit (Na2SO4:K2SO4:Fe2O3 = 1.5:1.5:1 mol.) which has commonly been used in fireside corrosion screening trials and is a mix that forms alkali-iron tri-sulphate (identified in many investigations as a cause of fireside corrosion) was used in these tests. The air-fired tests were carried out at temperatures of 600, 650 and 700 °C and oxy-fired tests were carried out at temperatures of 600, 650, 700 and 750 °C to represent the superheater/reheater metal temperatures anticipated in future power plants with and without synthetic deposits, with four candidate materials: T92, HR3C and 347HFG steels; nickel-based alloy 625 (alloy 625 was only tested with screening deposits). The progress of the samples during their exposures was measured using mass change methods. After the exposures, the samples were examined by SEM/EDX to characterise the damage. To quantify the metal damage, pre-exposure micrometre measurements were compared to the post-exposure image analyser measurements on sample cross-sections. The trends in corrosion damage in both air and oxy-firing conditions showed a “bell-shaped” curve, with the highest metal damage levels (peak) observed at 650 °C for air-firing and 700 °C for oxy-firing tests. However, at 600 and 650 °C similar damage levels were observed in both environments. The shift in peak corrosion damage in oxy-firing condition is believed to be the presence of higher levels of SOx, which stabilised the alkali-iron tri-sulphate compounds. Generally, in both air and oxy-firing conditions the mean metal damage was reduced with increasing the amount of Cr in the alloys. However, at the highest temperatures in both air-firing (700 °C) and oxy-firing conditions (750 °C) the metal damage of nickel based superalloy 625 was higher than HR3C.