Advanced Materials Research Vols. 123-125

Abstract: WO3 thin film was prepared on glass substrate at room temperature by RF magnetron sputtering deposition with hybrid (Ar+2.5% H2) gas. Effects of RF power on the microstructure, electrical and optical properties of WO3 films are investigated by field emission scanning electron microscopy, X-ray diffraction, Hall measurement and spectrometer. X-ray diffraction analysis reveals that all of the films are amorphous. The minimum resistivity of the WO3 film prepared with RF 70W is 5.74 × 10-3 -cm. The average transmittance in the visible region was decreased with increased RF power from 50W to 150W. The average transmittance was lower than 15% with RF 50W. The electrical and optical mechanisms have been explained in terms of composition and film thickness were changed with RF power.

Abstract: In this work, a smart nano- energy absorption system (nano-EAS) based on the liquid penetration/exudation in/from lyophobic nanoporous solids is proposed and its characteristics are theoretically and experimentally investigated. Damping properties of such smart nano-EAS can be reversibly, rapidly and significantly changed in a controlled fashion by external stimuli such as pressure, electric or magnetic fields, etc. Desired changes of the damping properties are induced by controlled variation of the surface tension of the liquid and/or the associated lyophobic solid, and/or by adjustment of the size of the nanopores. Variation patterns of the energy loss versus the applied pressure and the fluctuation rate of the pore radius are illustrated. Then, sensitivity of the proposed smart nano-EAS is evaluated.

Abstract: In this study, a testing rig in squeeze was designed and developed with the ability to conduct various tests especially for quasi-static squeezing at different values of magnetic field strength. Finite Element Method Magnetics (FEMM) was utilized to simulate the magnetic field distribution and magnetic flux lines generation from electromagnetic coil to the testing rig. Tests were conducted with two types of MR fluid. MRF-132DG was used to obtain the behaviour of MR fluid, while synthesized epoxy-based MR fluid was used for investigating the magnetic field distribution with regards to particle chains arrangement. Simulation results of the rig design showed that the magnetic flux density was well distributed across the tested materials. Magnetic flux lines were aligned with force direction to perform squeeze tests. Preliminary experimental results showed that stress-strain pattern of MR fluids were in agreement with previous results. The epoxy-based MR samples produced excellent metallographic samples for carbonyl iron particles distributions and particle chain structures investigation.

Abstract: The shape memory polymer (SMP) materials are able to change these shape in response to external stimulus such as stress, temperature, solvent, PH, magnetic, electricity or light. The above-mentioned methods are only to recover initial shape of the deformed SMP, could not give the SMP predeformation. In this paper, magnetic field gives the shape memory polymer composite (SMPC) pre-deformation was studied, through on and off of magnetic field the two-way activation of SMPC was achieved. Shape memory effect of shape memory composite in magnetic field was studied. The SMPC was filled by nickel powder, and the nickel powder was treated by silane coupling agent. The Tg of shape memory composite was measured by dynamic mechanical analyzer. The surface element of treated nickel powder was analysized with XPS. The results indicated that the shape of composite filled by untreated nickel powder did not change in the magnetic field, while the composite filled by treated nickel powder was drawn in the magnetic field. The tensile stretch was decrease with the increase of nickel powder content in the shape memory composite. The addition of silane coupling agent onto nickel powder surface was helpful for the dispersion of nickel in polymer.

Abstract: Shape memory polymers are stimuli-responsive materials able to adaptively store a temporary (deformed) shape and recover a ‘memorized’ permanent shape under an external stimulus. In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from NdFeB magnetic particles and crosslinked low density polyethylene (XLDPE) shape memory nanocomposite containing 2 wt% nanoclay is introduced. Various amounts of NdFeB particles (5, 15, 40 wt %) were added to the nanocomposite. Electromagnetically triggered shape memory properties of the formed composites were conducted using an alternative magnetic field with a frequency of 9 kHz and strength of 15 kW. The shape recovery of samples was possible by inductive heating and the shape recovery rates comparable to those obtained by conventional heating methods were demonstrated. It was concluded that the maximum heat generation achievable by inductive heating in the alternative magnetic field depends on magnetic particle content. The sample containing 15wt% NdFeB reached a full shape recovery of 25% extension within 6 minutes remaining in the magnetic field.

Abstract: In this work, ratio of the generated heat relative to the dissipated energy, during the cyclical advancing/receding of water on surface engineered nanoporous silica is evaluated based on a thermographical method. Proposed test rig is a compression-decompression cylinder divided into two chambers, one of constant volume and the other of variable volume. Silica particles are introduced inside the cavity of fixed volume, and a micro-filter is used to separate it by the chamber of variable volume, in which only water is supplied. Using an infrared-camera, the temperature distribution on the external surface of the cylinder is recorded versus the working time, and positions of the main heat sources are identified. Such tests allow evaluation of the dissipated energy and generated heat. One finds that the surface engineered nanoporous silica is able to dissipate large amounts of mechanical energy without significant heating, i.e., maximum 17 % of the dissipated energy is emitted in the infrared frequency range. Such result is surprising since the emissions recorded from traditional frictional dissipaters, such as hydro-pneumatic absorbers, rubber and foam absorbers, etc., are mainly (about 90%) in the infrared range, and only partially in the audio and visible frequency range.

Abstract: A systematic study on the phase transformation of Ni-Ti shape memory and superelastic alloys subjected to Severe Plastic Deformation (SPD) – High Pressure Torsion (HPT) technique has been carried out. Ni-Ti alloys of three compositions were chosen for the study. Specimens of these alloys in as-received (AR) condition and after HPT have been subjected to Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) analyses. In this study, while comparing the results of DSC thermograms and XRD spectra for the same sample conditions, some differences were observed. In the case of NiTi-H alloy after HPT, there appeared one stage phase transformation with DSC both while heating and cooling suggesting Martensite↔Austenite transformation but, with respect to XRD spectra while cooling, at the intermediate temperature of 55°C, the R-phase peaks corresponding to (1 1 2)R and (3 0 0)R planes appeared. In the thermogram obtained for the NiTi-B alloy subjected to HPT, it is observed that, while cooling, the Austenite to R-phase transformation is merged with R-phase to Martensite transformation. The results of the XRD obtained at -180°C show the presence of R-phase along with M-phase. The DSC curve of the NiTi-S alloy subjected to HPT corresponds to one stage phase transformation both while heating and cooling but, the diffractogram of the sample obtained at -180°C corresponds to the presence of both R-phase and M-phase.

Abstract: The porous Cu-11.9Al-2.5Mn (wt %) shape memory alloys with open-cell structure were successfully prepared by Sintering-evaporation Process method. A mixture powders with CuAlMn and NaCl powder were hot pressed at 780°C for 3hrs in the hot-pressing equipment with dynamic vacuum of 0.001Pa, and then pressure force was unloaded and the sintering temperature was heated up to 990°C, the NaCl was melted and evaporated completely at 990°C for 24hrs. The shape and size of the pores among the porous CuAlMn shape memory alloys are almost the same as those of NaCl powders, the pores are interconnected. The microstructure, mechanical property and phase transformation behavior of the sample have been studied. The results show that the porous CuAlMn SMAs with controlling porosity and pores’ structural parameters can be prepared by Sintering-evaporation Process, and their phase transformation behaviors are similar to that of conventional bulk Cu-11.9Al-2.5Mn (wt %) shape memory alloys.

Abstract: Different heat-treatments were carried out on the Ti-Ni shape memory alloy, alloy thread was made to straight line with the self-made alignment on 500 °C and then self-made angle training meter was used to train the alloys. Cement-based smart materials were prepared by the method of rolling agglomeration. Finally, indoor simulation experiment was carried out. The results show that the shape recovery ration becomes lower when quenching medium are hot-oil, hot-water, cold-oil and cold-water. The smart lost-circulation control material response quickly to external environment, the time from contact with external environment to the begin of distortion is less than or equal to five seconds, and to the end of distortion is less than or equal to sixty seconds.The best volume fraction for cement-based smart plugging material in cement slurry is 20%. Furthermore, the lost-circulation control material possesses the characteristics of a short time plugging and a strong pressure-bearing capability after plugging. And it improves the capacity of the ordinary cement-based smart lost-circulation control material.

Abstract: The simulating software ANSYS is applied to analyze the performance of the 1-3 Piezo-composiites under the σ3, σ1 and E3. Then we get the distribution of the internal stress and strain, sensitivity and activation characteristics. The conclusion is that the ceramic/polymer composites are more sensitive but will lead to stress concentration. While the stress distribution of the 1-3 cement based piezoelectric composites is more uniform so it is be propitious to protect the piezoelectric ceramic rods. The active strain of the 1-3 cement based piezoelectric composites is mainly concentrated on the piezoelectric ceramic rods.