8,464 research outputs found
Investigation into laser re-melting of inconel 625 HVOF coating blended with WC
Get PDFHigh velocity oxy-fuel (HVOF) spraying of Diamalloy 1005 powders mixed with WC particles onto steel (304) is considered and laser re-melting of the resulting coatings is examined. Laser re-melting process is modeled to determine the melt layer thickness while temperature increase is formulated using the Fourier heating law. The morphological and metallurgical analyses prior and post laser re-melting process are carried out using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray diffraction (XRD) technique is used to determine the residual stress developed in the coating while the analytical formulation is adopted to predict the residual stress levels at the coating base material interface. The indentation tests are carried out to determine the Young’s modulus and fracture toughness of the coating prior to laser re-melting. Corrosion resistance of coating is measured using potentiodynamic polarization technique prior and post laser treatment process. The predictions of the melt layer thickness are in good agreement with experimental results. The presence of WC particles modifies temperature rise and its gradient in the coating while affecting the Young’s modulus, residual stress levels, and fracture toughness of the coating. The differences in the thermal properties of Inconel 625 powders and WC particles result in formation of small size cellular structure through polyphase solidification. WC dissolution in the central region of the large polycrystalline cells is observed due to the loss of carbon through carbonic gas formation. The results of corrosion tests prevail that significant improvement of corrosion resistance can be achieved after laser treatment process
13.6 mW 79 GHz CMOS Up-Conversion Mixer With 2.1 dB Gain and 35.9 dB LO-RF Isolation
No full text[[abstract]]We report a 79 GHz mixer for direct up-conversion using 90 nm CMOS technology. In the mixer, an enhanced double-balanced Gilbert cell with current injection is used to reduce power consumption, and dual negative resistance compensation (NRC) is used to improve conversion gain (CG). In addition, it also includes two Marchand baluns: the single LO input signal to differential signal is converted by one of the baluns, and the differential RF output signal to single signal is converted by the other. The mixer consumes 13.6 mW, achieving IF-port input reflection coefficient (S-11) of -11.4 dB at 0.1 GHz, LO-port input reflection coefficient (S-22) of -12.2 similar to -28.7 dB for frequencies 75-90 GHz. At IF of 0.1 GHz and RF of 78.1 GHz, the mixer achieves CG of 2.1 dB and LO-RF isolation of 35.9 dB, the best CG and isolation results ever reported for aW-band silicon-based mixer with power consumption lower than 15 mW.[[note]]SC
Obtaining Crack-free WC-Co Alloys by Selective Laser Melting
No full textAbstractStandard hardmetals of WC-Co system are brittle and often crack at selective laser melting (SLM). The objective of this study is to estimate the range of WC/Co ratio where cracking can be avoided. Micron-sized Co powder was mixed with WC nanopowder in a ball mill to obtain uniform distribution of WC over the surface of Co particles. Continuous layers of remelted material on the surface of a hardmetal plate were obtained from this composite powder by SLM at 1.07μm wavelength. The layers have satisfactory porosity and are well bound to the substrate. The chemical composition of the layers matches the composition of the initial powder mixtures. The powder mixture with 25wt.%WC can be used for SLM to obtain materials without cracks. The powder mixture with 50wt.%WC cracks because of formation of brittle W3Co3C phase. Cracking can considerably reduce the mechanical strength, so that the use of this composition is not advised
A 12.1 mW 50-67-GHz CMOS UP-CONVERSION MIXER WITH 6-dB CONVERSION GAIN AND 30.7-dB LO-RF ISOLATION
No full text[[abstract]]A 50-67-GHz double-balanced mixer for direct up-conversion using standard 90-nm CMOS technology is reported. The up-conversion mixer comprises an enhanced double-balanced Gilbert cell with current injection for power consumption reduction, and negative resistance compensation for conversion gain (CG) enhancement, a parallel and differential intermediate frequency (IF) transconductance stage for bandwidth and linearity enhancement, a Marchand balun for converting the single local oscillator (LO) input signal to differential signal, and another Marchand balun for converting the differential radio-frequency (RF) output signal to single signal. The mixer consumes 12.1 mW and achieves IF-port input return loss of -12.8 dB at 0.1 GHz, LO-port input return loss of -9.5 to -11.4 dB and RF-port input return loss of -10.7 to -12.5 dB for frequencies 57-64 GHz. At IF of 0.1 GHz, the mixer achieves CG of 3.1-6 dB and LO-RF isolation of 26.4-30.7 dB for RF of 50-67 GHz. The corresponding 3-dB bandwidth of RF is larger than 17 GHz (the measurement range of 50-67 GHz). To the authors' knowledge, the CG and power consumption are the best results ever reported for a 60-GHz CMOS/BiCMOS up-conversion mixer. In addition, the measured IIP3 is -6.4 dBm at RF of 60 GHz. (c) 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:475-483, 2014[[note]]SC
Characterizing the thermally induced structural transitions to intact porcine eye I: Second harmonic generation imaging of cornea stroma.
No full textThe detailed thermal collagen denaturation process and its association with gross shrinkage revealed by second harmonic generation microscopy
No full textAbrasive wear behaviour of detonation sprayed WC-Co coatings on mild steel
No full textThe main objective of the present investigation is to evaluate the abrasive wear behaviour of detonation sprayed WC-Co coatings and to compare them with plasma sprayed WC-Co coatings and carburised and nitrided surfaces. Mild steel was coated with WC-12Co and WC-17Co using detonation and plasma guns. The abrasive wear rates of these coatings were determined at three different loads and compared with wear rates of as received, carburised, and nitrided mild steel. The abraded surfaces and the surfaces beneath the abraded surfaces were characterised by SEM. The results indicate that the detonation sprayed WC-12Co coating has the best abrasive wear resistance at all loads. Maximum improvement in wear resistance is obtained at an intermediate load (i.e. at 5 kg). The wear of detonation sprayed coatings is by abrasion of the soft Co matrix followed by the pullout of hard WC particles
Toluidine Blue O Photodynamic Inactivation on Multidrug-Resistant Pseudomonas aeruginosa
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Cavitation erosion mechanism of S31600 stainless steel laser surface-modified with unclad WC
No full textLaser surface modification of UNS S31600 stainless steel using coarse unclad WC powder (particle size ≈60 μm) for enhancing cavitation erosion resistance was attempted. WC powder was preplaced on as-received S31600 substrate and irradiated by a high-power CW Nd:YAG laser to form a metal-matrix composite (MMC) layer on the substrate. By varying the laser fluence, MMC layers consisting of 3-28 vol.% of WC particles were formed. The microstructure, composition, and the phases present in the modified layer were studied by optical microscopy (OM), energy-dispersive spectrometry (EDS), scanning electron microscopy (SEM), and X-ray diffractometry (XRD). The cavitation erosion resistance Re in 3.5% NaCl solution was determined using an ultrasonic vibratory facility. Re was found to attain a maximum value (10.7 times that of as-received S31600) at 9 vol.% of WC. The damaged surface after the cavitation erosion test was studied by SEM to identify the damage mechanism. The variation of Re with the volume fraction of WC was explained in terms of the erosion mechanism of the matrix and the WC particles.Department of Industrial and Systems Engineerin
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