Papers by Keyword: Room Temperature

Abstract: A gas sensor based on a multi-walled carbon nanotube (MWCNTs-OH) network was fabricated by filtration from the suspension method (FFS), and its properties were improved by coating the network with a polypyrrole conductive polymer. The polymer was prepared using the chemical oxidation method. Metallic nanoparticles of silver and copper were added separately to the polymer by the in situ chemical oxidation method. The fabricated networks were characterized using an X-ray diffractometer (XRD) and a Photoluminescent spectrometer. For the networks of (MWCNTs) with polypyrrole (PPy), (PPy: Cu), the (002) peak's widening diminishes, and the broadening increases when silver (PPy:Ag) is added to the MWCNTs networks. The crystalline size decreases for the networks coated by (PPy) as well as silver NPs (PPy:Ag), while it increases with the network coated by (PPy:Cu). Photoluminescence spectra of the networks were measured at different excitation wavelengths (340-380) nm and the networks gave the emission spectra in the range of (765-855) nm. The analysis revealed that the energy gap becomes larger for the networks coated with (PPy: Ag), (PPy: Cu) networks than for pure MWCNTs. A homemade sensing device was used to evaluate the sensitivity of the fabricated networks for gas concentration of 20 ppm at room temperature. The sensitivity of the fabricated sensor was (56.17%). After modifying the surface of the fabricated network by coating with the polypyrrole conductive polymer and polypyrrole composite with silver and copper metallic nanoparticles, the sensitivity became (59.29, 64.5, and 65.3) % respectively.

Abstract: In this paper, in order to explore the development of a titanium-based superalloy with a working temperature of 700°C to 750°C and good ductility at room temperature, using Ti+Al+Ti2AlNb ternary powder as the raw material, the temperature is 1200°C to 1300°C, 30MPa, 1.5h Directly mixed and sintered under hot pressing conditions, a new type of titanium-based superalloy (TiAl+Ti2AlNb) samples were prepared. The fracture morphology of hot-pressed sintered samples and tensile samples used scanning electron microscope (Scanning electron microscope, referred to as SEM) and Electron backscattered diffraction (EBSD) for observation. Discuss the room temperature tensile fracture behavior of a new type of high temperature titanium alloy Ti-Al-Nb, and lay a technical foundation for the development of a new type of high temperature titanium-based alloy with low brittleness at room temperature.

Abstract: NH₃ gas sensor was fabricated based on deposited of Functionalized Multi-Walled Carbon Nanotubes (MWCNTs-OH) suspension on filter paper substrates using suspension filtration method. The structural, morphological and optical properties of the MWCNTs film were characterized by XRD, AFM and FTIR techniques. XRD measurement confirmed that the structure of MWCNTs is not affected by the preparation method. The AFM images reflected highly ordered network in the form of a mat. The functional groups and types of bonding have appeared in the FTIR spectra. The fingerprint (C-C stretch) of MWCNTs appears in 1365 cm^-1, and the backbone of CNTs observed at 1645 cm^-1. A homemade sensing device was used to evaluate the fabrication network toward NH₃ gas at ppm levels as well as the response to sensitivity by changing the concentration. MWCNTs-OH network of 8mm thickness showed an increase in resistance upon exposure to the NH₃ gas. The sensor exhibits a good sensitivity for low concentration of NH₃ gas at room temperature. The sensitivities of the network were 2.5% at 14ppm, 5.3% at 27ppm and 17.6% at 68ppm. Further investigations showed that the network was specific sensitive to NH₃ gas in the environment and not affected by the amount of ambient air.

Abstract: Functionalized Multi-Walled Carbon Nanotubes (MWCNTs-OH) network with thickness 4μm was made by the vacuum filtration from suspension (FFS) method. The morphology, structure and optical properties of the MWCNTs film were characterized by SEM and UV-Vis. spectra techniques. The SEM images reflected highly ordered network in the form of ropes or bundles with close-packing which looks like spaghetti. The absorbance spectrum revealed that the network has a good absorbance in the UV-Vis. region. The gas sensor system was used to test the MWCNT-OH network to detect NH₃ gas at room temperature. The resistance of the sensor was increased when exposed to the NH₃ gas. The sensitivities of the network were 1.3% at 14ppm, 3.3% at 27ppm and 6.13% at 68ppm. The sensor is specifically sensitive to NH₃ gas and does not affect by the amount of ambient air.

Abstract: High-quality nanocrystalline (NC) SnO₂ thin films were grown on SiO₂/Si and Al₂O₃ substrates using sol–gel spin coating method. The structural properties, surface morphologies and gas sensing properties of the NC SnO₂ were investigated. XRD measurements showed a tetragonal rutile structure and the diffraction peaks for NC SnO₂ thin films grown on Al₂O₃ substrates outperformed those of NC SnO₂ films grown on SiO₂/Si substrates. The surface morphology of the annealed SnO₂ thin films at 500 °C appeared as polycrystalline with uniform nanoparticle distribution. Hydrogen (H₂) gas sensing performance of the NC SnO₂ was examined for H₂ concentrations ranging from 150 ppm to 1000 ppm at different temperatures (room temperature, 75 and 125 °C) for over 50 min. The room temperature sensitivities for H₂ gas sensors based on NC SnO₂ thin films grown on Al₂O₃ and SiO₂/Si substrates was 2570% and 600%, respectively upon exposure to 1000 ppm of H₂ gas. While the sensitivity values at 125 °C increased to 9200% and 1950%, respectively.

Abstract: The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hardfacing with the stainless steel (DIN X3CrNiMo18-13-3) matrix, reinforced with WC/W₂C, under the room and elevated temperature. The hardfacing was produced, applying the optimized set of parameters (current – 55 A, reciprocating speed – 1.0 mm/s, oscillation frequency – 0.6 Hz). The average reinforcement content was 29.3 ± 4.0 vol %. The reinforcement consisted of W₂C and WC, while M₇C₃- and M₂₃C₆-type (M = Fe, Cr, Mo, W) carbides were the main phases in the matrix. Universal hardness and Young’s modulus were approximately 5.3 and 1.9 times higher, than those of the reference steel (DIN X2CrNiMo18-14-3). The sliding wear of the hardfacing was 4.9 times lower under 20 °C and 3.1 times lower under 300 °C, but 1.8 times higher under 500 °C than the wear of the reference steel. Galling was the wear mechanism of the hardfacing under 20 °C, scoring – under 300 °C and combination of scoring and binder extrusion – under 500 °C

Abstract: As one of the key components of non-ballast slab track in high speed railway, cement asphalt emulsion mortar (CAM) has low compressive strength and low elastic modulus. This makes CAM possible to be served as supporting, height-adjusting, vibration-dissipating and deformation-fitting sandwich-layer between pre-stress slab and concrete roadbed. To study the fatigue behavior of the CAM, fatigue tests were conducted at room temperature and negative temperature, respectively. The permanent strain, elastic modulus and yield strength of fatigue-tested specimens were compared to the reference one. The results showed that the small permanent deformation lead to very little displacement differences among the slab track system. Secondly, the elastic modulus and yield strength of fatigue test specimens were both higher than that of reference one. Because the fatigue process might strengthen the CAM by compacting micro-cracks. Additionally, arising from the temperature sensitivity of asphalt, viscosity behavior of asphalt mortar at room temperature is changed to brittleness behavior at negative temperature.

Abstract: Natural sand-based magnetite nanoparticles have been succesfully synthesized by coprecipitation method at room temperature. Magnetite nanoparticles were investigated by X-ray Diffractometer (XRD) and Vibrating Sample Magnetometer (VSM). The morphology of magnetite nanoparticles has been evaluated by Transmission Electron Microscopy (TEM). Qualitative analysis of XRD data reveals that the structure of magnetite nanoparticles have the same phase of ICSD No. 82237. On the other hand, quantitative analysis shows that the crystallite size of magnetite nanoparticles have ranges between 8.89 nm to 12.49 nm. The average diameter of magnetite nanoparticles increase with the increase the stirring rate of reaction when the stirring rate is lower than 1000 rpm, while the crystallite size of magnetite particles decrease with the increase the stirring rate when the stirring rate is higher than 1000 rpm. The stirring rate of reaction influence the the magnetic properties of magnetite nanoparticles. The results of the best magnetic respon are revealed for the stirring rate of 1000 rpm with the larger the crystallite size of magnetite nanoparticles due to its stronger saturation magnetization.

Abstract: An in-expensive way of fabricating PDMS microfluidic using room temperature curing process is presented which can be used for both laboratory and commercial scale. The microfluidic was designed using AutoCAD for master mold preparation and subsequently created with SU8 for rapid prototyping process; the micro mixer and the whole mixer were fabricated in less than without using costly fabrication steps. The device profiles were observed for structural integrity and evaluation by dropping two food coloring dyes through the two inlets and collecting the sample at outlet. Flow rate and mixing efficiency were quantitatively measured by analyzing the recorded flow profiles and values of the image collected from the high powered microscope at inlet and outlet locations is fully obtained and will be presented in our next publication

Abstract: An attempt has been made to study the dry sliding wear behaviour of Aluminium based hybrid composites in room temperature.Al 2219 is used as base material with B₄C and MoS₂ as reinforcements. The hybrid composite were prepared by conventional stir casting technique. The dry sliding wear test were carried out for various parameters like sliding distance, applied load and sliding speed. The Optical Microscope and SEM results showed the presence of B₄C and MoS₂, which are fairly uniform and randomly dispersed on matrix material.XRD analysis, shown the presence of B₄C and MoS₂ phases in the prepared composites.The incorporation of reinforcement particles B₄C and MoS₂ reduces the specific wear rate of composites. The addition of MoS₂ as a secondary reinforcement has significant effect on reducing specific wear rate of prepared composites. By using SEM worn surface of hybrid composites were studied.