Abstract: As a novel porous functional material, metal rubber (MR) had many advantages of high loading capacity, high anti-blocked capacity and adjustable porosity with outside pressure made the MR more suitable as filtration material. However, there was no related study and successful application nowadays except in Russia. This study detailed investigated the filtration performance of MR including the influence of wire line diameter, porosity and molding thickness on initial pressure drop under clean liquid condition and their effects on pressure drop-flow rate property and filtration efficiency under contaminated liquid condition. The results indicate that the initial pressure drop increased with the decrease of porosity and wire line diameter, however decreased with the decrease of molding thickness when the flow was constant. Filtration drop increased significantly with the decrease of porosity. MR material made of small diameter wires showed a high filtration efficiency and large pressure drop because of its’ fine micro-pore. Filtration drop rose with the increase of molding thickness however, the filtration efficiency was little affected. These results provide a suitable guideline for further MR filter appliance and MR material research.
Abstract: This paper presents temperature control of engine cooling system using a controllable magnetorheological (MR) fan clutch. An appropriate size of MR fan clutch is devised and modeled on the basis of Bingham model. Subsequently, an optimization to determine design parameters such as width of housing is undertaken by choosing the reciprocal of the controllable torque as an objective function. This has been performed using a finite element analysis. A sliding mode controller is then designed to control the angular velocity of the MR fan clutch using experimentally determined parameters. The designed controller is implemented and control performances of the MR fan clutch system are evaluated.
Abstract: This experimental investigation presents wear characteristics of magnetorheoloigcal (MR) fluid under boundary lubrication contact condition. Three different specimens; aluminum, copper and steel pins are prepared and wear test is performed under consideration of several operational factors such as normal load, sliding distance, and sliding speed by using pin-on-disk test equipment. Wear rate and friction coefficients of the MR fluid are experimentally evaluated with respect to the sliding ranges. Microscopic surface and roughness changes of the worn surface of pin specimens are also analyzed by using the scanning electron microscope (SEM). In addition, Energy Dispersive X-ray Spectroscopy (EDS) analysis is conducted and chemical changes are investigated.
Abstract: Moisture/liquid transport in textile fabric is one of the critical factors affecting physiological comfort. Here we investigate the water transport properties of plant structures textile fabric, which was formed by mimicking the tree structure network. Our work shows that the water transport properties of the new type of material depend on its geometric structures, including the branching level and the diameter and length of the 0th branching level, and the structure fractal dimension. The more the length and the branching level, the lower the water transport capacity. A comparison of the plant structured textile fabric with the general fabric indicates that the plant structured fabric can provide higher moisture transport capacity and its maximum water transport capacity approach 1.707 times higher than that of the general fabric.
Abstract: Transition between Wenzel and Cassie states on superhydrophobic surface has attracted substantial interest from various research communities. The transition between the two states is realized by the methods of changing surface structure in micron scale, or changing the surface tension between a droplet and a solid surface through external electric field, temperature, light, etc. In this paper we design a rough surface on aluminum substrate with the etching processes, on which a large superhydrophobic surface is achieved easily and economically. On this surface, a drop of saline solution water forms a nearly perfect spherical pearl with the apparent contact angle over than 160°. By applying external voltage between the substrate and the solution, we observe a different electrowetting phenomenon from the case on other superhydrophobic surfaces, i.e. on silicon nanowires coated with hydrophobic fluoropolymer C4F8. This difference is discussed and explained by asymmetry of the superhydrophobic surface which increases the hysteresis. A saturated apparent contact angle is also observed as the applied voltage increased to a specific value.
Abstract: An electrodeless resistivity measurement system developed recently can provide a reliable method for monitoring the hydration process of cement-based materials continuously and accurately. Phosphoaluminate cement (PAC) sets quickly and develops high early strength. In order to understand the mechanism, the hydration products and microstructure formation of PAC in early age need to be studied. In the study, early hydration process of PAC with different dosage of retarder was investigated by the electrodeless resistivity equipment. According to resistivity-time curve, resistivity of freshly mixed PAC paste decreases sharply and then rises slowly, some characteristic peaks appear at different hydration stages of PAC. Heat evolution of PAC was also measured. The hydration mechanism and structure formation were studied according to these results. Depending on the dosage of retarder, the hydration process of PAC includes four stages which are dissolution, induction, acceleration and deceleration.
Abstract: Penetration and diffusion of chloride ions in concrete can lead to the corrosion of steel bar and shorten the service life of concrete structures. Phosphoaluminate cement (PAC) is a new cementitious material which has many special properties compared to Portland cement (PC). In the study, chloride ion diffusion in PAC concrete was tested with RCM method. The phase composition and morphology of hydration products, pore volume of hardened paste cured for 28d were analyzed with X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that chloride ion diffusion coefficient of PAC concrete is much lower than that of Portland cement concrete under the same test conditions. The hydration products of PAC are main micro-crystalline phase and gel of phosphate and/or phophoaluminate, which formed a dense microstructure. There is no calcium hydroxide produced in the PAC hydration system. In hardened PAC paste, chloride ions might replace the atom group [OH] - and [PO4]3- of hydrates and become stable compounds. The resistance to chloride ion diffusion of PAC concrete will increase with the hydration age, because its microstructure becomes denser with the hydration age increasing.
Abstract: Accurate modeling and computer aided simulation is advantageous during the design stage of a piezoelectric energy harvesting system. In this paper, system-level finite element modeling (FEM) of a cantilevered piezoelectric energy harvester with a resistor is conducted using ANSYS. Considering that practical energy harvesting circuit includes nonlinear electrical elements, which is beyond the modeling capability of ANSYS, an equivalent circuit modeling (ECM) method is proposed to address the problem. After the parameters of equivalent circuit are identified, system-level simulation is conducted in SPICE software.
Abstract: Nanostructured Lanthanum hexaboride (LaB6) powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS). The average size of LaB6 nanoparticles is about 35nm, which are well crystallized with ball or ellipsoid with inconspicuous corners and covered by a 3-5nm thick amorphous layer containing oxygen and carbon. The absorption of LaB6 nanoparticles in visible and near infrared spectrum (NIR) was measured and compared with micron scale particles. The surface plasmon responance (SPR) of nanoparticles was very efficient at NIR blocking, which almost covered the whole NIR region. The influence of nanoparticles concentration on spectrum absorption was comparatively evident. Meanwhile, micron particles almost haven’t NIR blocking function.
Abstract: Micron, sub-micron and nanometer sized MgO•Al2O3 ultra-fine powders were prepared by gel precipitation, solid-phrase synthesis, sol-gel and flame throwing pyrogenation methods. XRD analysis shows that the all of the ultra-fine powder is pure with a single MgO•Al2O3 spinel phase. The size is measured by laser granularity analyzer and the average size is 60, 505 and 1780 nm with quite uniform distribution. MgO•Al2O3 spinel powder with different granularity were sprayed into molten medium carbon steel in MgO crucible and MoSi2 furnace at 1873 K. Quantitative microscopic examination shows that big particle inclusions are reduced and small particle inclusions increased, and the average size is reduced. Data comparison from spraying different size powders shows that spraying MgO•Al2O3 of nanometer tends to cause more small inclusions. The sprayed steel samples were rolled and heat treated for the mechanical properties tests, which shows spraying nanometer MgO•Al2O3 is the best way to improve mechanical property.