Current Smart Materials - Volume 1, Issue 1, 2016

Background: The conventional hydraulic dampers have limited adaptability to the variation frequency and amplitude of incident load for minimisation of the transmissibility to the structures. The active type dampers have the limitations in terms of power pack requirement and stability of control. Therefore the semi active dampers of ER/MR type are attractive contenders for the design of dampers. Method: An overview of ER/MR damper designs and modelling has been presented with an introduction to underlying principles and the key technological challenges. The overview of designs of ER/MR dampers envisages Poiseuille flow type, Couette type and multitube dampers in a morphological manner. As per the published works the optimisation methodology of damper actuators is presently based on volume constrained optimisation. The overview of modelling techniques covers phenomenological models and fluid dynamics models. Results: The phenomenological models predict the damper behaviour with good accuracies however the review paper emphasises the need for further research on transient model as the model gives a closer agreement with the experimental results. Some of the phenomenological models are based on fitting piecewise functions to the experimental data for predicting force velocity damper response. Such models pose difficulty in terms of determining inverse model for the control of ER/MR damper. The stability of phenomenological models in direct and inverse mode for high speed applications needs to be explored. Conclusion: The transient model with improved solution techniques and modelling of body forces can accurately predict the damper response at all operating speeds. The quasi-static and transient models are amenable for their application in direct and inverse mode.

Background: Addition of nonmagnetizable particles to a magnetorheological (MR) suspension causes an increase in the magnetic field-induced yield stress. The goals of this paper are to determine how the suspension microstructure changes when the nonmagnetizable particles are added, and whether or not such changes can cause the changes in rheological properties. Methods: We employed particle-level simulations to investigate the structural and rheological properties of MR suspensions containing a mixture of magnetizable and nonmagnetizable spheres. We demonstrate that nonmagnetizable spheres cause the yield stress to increase in monolayers and three-dimensional simulations, as is observed in three-dimensional experiments. We examine the role of nonmagnetizable spheres in the suspension structure for monolayer and three-dimensional suspensions. Structure measures examined included the fluctuations in volume fraction, the pair distribution functions, and the eigenvalue ratio of the mass moment tensor of clusters. Results: The nonmagnetizable spheres cause only minor changes to the microstructure of the magnetizable sphere component of the suspensions. Furthermore, the nonmagnetizable spheres cause structural changes to monolayers that differ from the changes in microstructure of three-dimensional suspensions. Conclusion: The results suggest that the small structure changes caused by the addition of nonmagnetizable particles do not cause the increase in yield stress.

Background: A major concern of the current concrete structures technology is to develop systems that can monitor their own structural integrity condition in real time. This paper presents the development of a portable and innovative wireless damage monitoring system based on an alternative consideration of electromechanical impedance concept, integrating PZT sensors/actuators transducers into the concrete structures themselves. Methods: The proposed wireless monitoring system for active sensing is designed, built, tested and provided with all capabilities needed to perform an integrity assessment by means of the use of a Raspberry Pi single-board microcomputer as the core hardware element to control the whole system function. Results: It is found that the proposed alternative of the electromechanical impedance (EMI) technique associated with decision boundaries based on extreme value statistics is very sensitive to the damage introduced in concrete structures from their earliest stage. The tests run on the developed prototype prove that the proposed monitoring platform can actually be used to perform damage detection investigation with the required accuracy. Conclusion: Its effectiveness and low cost make this platform a very promising contribution towards the implementation of large-scale wireless structural health monitoring applications.

Background: Polymer gel electrolytes have attracted much intention due to their high ionic conductivity (10-2 - 10-3 S/cm) along with other suitable properties like good thermal stability, compatibility with electrode materials, easy workability, wider control of properties etc. These materials are also called smart materials due to their practical applications in various devices like high energy power devices, electrochromic devices, supercapacitors, devices for Infra-red systems etc. This paper mainly discusses the enhancement of an ionic conductivity with the addition of polymer. No appreciable change in conductivity of gel electrolytes has been observed with temperature, which makes them suitable for device applications. Methods: Liquid electrolytes were prepared by dissolving orto-nitro benzoic acid (o- NBA) in the ternary mixture of ethylene carbonate (EC), propylene carbonate (PC), and dimethylacetamide (DMA) (in 2:2:1 volume ratio). The homogeneous polymer solution of PVdF in acetone is prepared and then added to the liquid electrolyte along with continuous stirring. Polymer gel electrolytes are obtained after the evaporation of acetone. Ionic conductivity of liquid and polymer gel electrolytes is measured by HP4284A precision LCR meter (having frequency range from 20Hz-1MHz) using complex impedance spectroscopy. Results: The conductivity of liquid electrolytes increases by two orders of magnitude with an addition of ortho-nitro benzoic acid (10-6 to 10-4 S/cm) and maximum room temperature conductivity of 1.46 x 10-4 S/cm has been obtained at 2M concentration of o-NBA in ternary mixture of EC, PC and DMA. The conductivity of electrolytes increases with the addition of polymer and maximum conductivity of 5.91 x 10-4 S/cm has been obtained at room temperature. The increase in conductivity has been explained by using “Breathing Polymer Chain Model”. Ionic transference number was calculated and it was found out to be nearly 1, which suggests that gel electrolyte is principally ionic conductor. Conclusion: Maximum conductivity of 5.91 x 10-4 S/cm at room temperature has been observed for gel electrolyte containing 2M ortho-nitrobenzoic acid in EC:PC:DMA (2:2:1) with 8 wt% PVdF. The conductivity of polymer gel electrolytes has been found to increase with the addition of PVdF concentration. The conductivity of gel electrolytes is found to be higher than that of liquid electrolytes at all PVdF concentrations i.e. σ(gel) > σ(liquid). The increase in conductivity has been found to depend upon the concentration of acid, dissociation constant of acid and concentration of PVdF used. No appreciable change in conductivity of gel electrolytes has been observed with temperature, which make them suitable for device applications. Ionic transference number measurements suggest that these electrolytes are principally ionic conductors.

Background: Heterogeneous synthesis of nitrogen containing heterocyclic compounds such as dihydropyrimidin-2(1H)-one/thione derivatives is an important research. Use of nanocrystalline ZnO has demonstrated for heterocyclic compounds which are routinely used in medicinal chemistry due to their therapeutic and pharmacological properties. In this context the solvent free synthesis of pyrimidine derivatives are reported. Methods: Synthesis of ZnO nanomaterials is carried out by precipitation method, which is further used for synthesis of dihydropyrimidin-2(1H)-ones/thiones derivatives. Stoichiometric amount of aromatic aldehydes (1), urea (2) and ethyl acetoacetate (3) were taken in beaker. Then, 10 mmol percent nanocrystalline ZnO powder was added as a catalyst in the reaction mixture which was subjected to heated at 55°C in microwave oven. Results: Microwave assisted synthesis of 3,4-Dihydropyrimidin-2(1H)-ones/thiones has been successfully carried out using eco-friendly ZnO nanoparticles as catalysts. Nanocrystalline ZnO of particle size in the range 60-80nm was prepared by decomposing the Zinc Oxalate intermediate at 500ºC XRD analysis indicates the formation of highly crystalline hexagonal phase of ZnO. Solvent free synthesis using reported method have confer 95% yield which is greater than organic solvents such as DMF, Dioxane, THF, Toluene for heterogeneous synthesis. Conclusion: Successfully accomplished ‘green’ synthesis of dihydropyrimidone/thiones derivatives was demonstrated. Use of nanocrystalline ZnO is found to be an efficient catalyst for heterogeneous Biginelli reaction. Solvent free reactions gave the better yield compared to the use of organic solvents.

Background: Spectroscopic studies in the past have exposed that PbO-B2O3 glasses are mostly classified as non-crystalline materials. These glasses prove to good host for incorporating RE (rare earth) and transition metal oxides due to its low phonon energy, large ion Polarizability and higher covalency. TM’s are widely used in the glass due to their two or more valence states. These states affect optical as well as structural properties. Due to commercial importance, B2O3 is good glass former. It is frequently used as a dielectric material. The transition metals incorporated borate glasses have great importance in the field of luminescent solar energy concentrators, gamma ray shielding materials, opto-acoustical electronics, solid state lasers, optical fibres, UV filters and ultrasonic devices in nonlinear devices for frequency conversion in the ultraviolet region and piezoelectric actuator. In transition metals cadmium oxide incorporated glasses has great importance because it can act both as network former and network modifier. Another important factor of cadmium glass is low electrical resistivity, wide band gap and high transmission in the visible region. It has different applications such as photo transistors, diodes, transparent electrodes, solar cells and gas sensors. Method: Glass samples xCdO-(35-x) PbO–65B2O3 with x varying from 0 to 15 mol % have been formed by the conventional melt quench technique. The raw materials of cadmium oxide (CdO), lead oxide (PbO) and boric oxide (B2O3) of suitable amounts are mixed properly and melted crucible at temperature 1000-1100°C in silica till the formation of bubble free liquid. This melt is then transferred in to a heated steel mould. These samples are annealed at temperature of 380°C for 1 hour so that samples do not break due to remaining internal strains. These samples are grinded with different grades of SiC and polished with CeO2 so as to obtain maximum flatness. The composition of the glass samples is shown in Table 1. The structural and physical properties are examined by using XRD (X-ray diffraction), Fourier transform infrared spectroscopy (FTIR), density and molar volume techniques. Results: Cadmium oxide doped glasses have been synthesized by using melt quench technique. XRD, density, molar volume and FTIR spectroscopy have been used to characterize the glasses. XRD confirms the glassy behaviour of prepared samples. There is a rise in density of glasses (4.11 to 4.94 g/cm3) and consistent decline in molar volume (30.02 to 22.10) of glasses with incorporation of cadmium. FTIR spectroscopy shows that addition of cadmium oxide helps to translate [BO3] units into [BO4] units. Also the corporation of cadmium effect on the ionic/covalent behaviour of glasses; covalency decreases and ionicity increases. Conclusion: (1) Xrd shows the amorphous nature of prepared samples. (2) Results of boron-boron separation show that addition of cadmium oxide makes compaction in glass network which is due to the presence of BO4 groups. These factors help to increase the density and reduce the molar volume. (3) Ionicity and covalency results confirmed that addition of cadmium oxide increased the ionicity of glass sample which may be used to make some ionic applications.