On the Evaluation of the Elastic Modulus of Soft Materials Using Beams with Unknown Initial Curvature

A non‐linear optimization procedure is established to determine the elastic modulus of slender, soft materials using beams with unknown initial curvature in the presence of large rotations. Specifically, the deflection of clamped‐free beams under self‐weight – measured at different orientations with respect to gravity – is used to determine the modulus of elasticity and the intrinsic curvature in the unloaded state. The approach is validated with experiments on a number of different materials – steel, polyetherimide, rubber and pig skin. Because the loading is limited to self‐weight, the strain levels attained in these tests are small enough to assume a linear elastic material behaviour. This non‐destructive methodology is also applicable to engineered tissues and extremely delicate materials in order to obtain a quick estimate of the material's elastic modulus.     

Enhancement in ethanol sensing response by surface activation of ZnO with SnO2

A surface functionalized gas sensing material convincingly giving enhanced response to ethanol is demonstrated by SnO₂ activated ZnO. Zinc oxide was synthesized by a chemical route, deposited on an alumina substrate and activated by tin dioxide obtained by on-site oxidation of tin chloride. The XRD study of samples confirmed wurtzite hexagonal structure of zinc oxide and FESEM investigation revealed that surface of activated ZnO microrods was covered by nanoparticles of tin dioxide. Sensing response of sensing elements activated with different concentrations of tin chloride solution has been investigated. It was found that response to ethanol vapor significantly enhanced (eight times) by surface activation with tin dioxide, which optimized at a concentration of 3 wt.%.     

Computation of feed-paths for casting solidification using level-set-method

The aim of the present work is to compute feed-paths and hot-spots by combining level-set-method based sharp interface and feed-path model. The model is based on the solution of energy and level-set equations in solid and liquid, with Stefan condition on the interface. The energy and level-set equation are discretized using finite-volume and finite-difference method, respectively. Feed-path is computed by tracking mass-less particles along the liquid-solid interface during solidification using combined Eulerian-Lagrangian framework. The proposed model is benchmarked on six test cases, where temperature contours and solidification time are compared with a finite-element-method based commercial software. The capability to predict the temporal evolution of interface and to identify multiple hot-spots is validated with an industrial aluminum-alloy lug casting. The numerical as well as experimental validations demonstrate the effectiveness of level-set-method for feed-path calculation.     

Morphological, structural, and functional properties of maranta (Maranta arundinacea L) starch

Starch isolated from maranta (Maranta arundinacea) tuber and studied for its various physicochemical characteristics. The amylose content of the starch was 24.8%. SEM showed that the granules were small indented and spherical. Maranta starch granule size has a range of 2.92–6.42 μm, (mean of 4.84 μm), length/degree of 1.20, and roundness of 0.73. Maranta starch has a gelatinization temperature of 74.8°C, peak viscosity of 498 BU, and cold paste viscosity of 669 BU. It also possessed higher freeze-thaw stability. Dynamic rheological properties of maranta starch, measured using parallel plate geometry showed increased storage modulus (G’) values, while loss modulus (G″) values were decreased with increasing frequency values (0–100 Hz). The low gelatinization temperature and high freeze thaw stability of starch indicates its potential for application as a thickener in food industries.     

A study of external mass transfer effect on biodegradation of phenol using low‐density polyethylene immobilized Bacillus flexus GS1 IIT (BHU) in a packed bed bioreactor

The impact of external mass transport on the biodegradation rate of phenol in a packed bed bioreactor (PBBR) was studied. A potential bacterial species, Bacillus flexus GS1 IIT (BHU), was isolated from the petroleum‐contaminated soil. Low‐density polyethylene (LDPE) immobilized with the B. flexus GS1 IIT (BHU) was used as packing material in the PBBR. The PBBR was operated by varying the inlet feed flow rate from 4 to 10 mL/min, and the corresponding degradation rate coefficients were found to be in the range of 0.119–0.157 L/g h. In addition, the highest removal rate of phenol was obtained to be 1.305 mg/g h at an inlet feed rate of 10 mL/min. The external mass transfer was studied using the model . A new empirical correlation for the biodegradation of phenol in the PBBR was developed after the evaluation at various values of K and n.     

Synthesis and phase stability of precursor derived HfO2/Si-C-N-O nanocomposites

Hafnium alkoxide modified polysilazane was synthesized by the drop-wise addition of hafnium tetra(n-butoxide) to polysilazane. The solid state thermolysis (SST) temperature and the ceramic yield for both the polysilazane and modified polysilazane were determined by performing thermogravimetry. Fourier transform infrared spectroscopy was performed to understand the polymer to ceramic conversion as well as the bonding characteristics of the ceramics. The modified polymer after crosslinking was subjected to SST at 800 °C at a constant heating rate of 5 °C/min for a dwell time of 2 h in atmospheric ambience. From the X-ray diffractograms, the as-thermolysed ceramics were observed to remain X-ray amorphous and on heat-treatment resulted in the crystallization of tetragonal hafnia. However, on heat-treatment at 1500 °C, reverse phase transformation from tetragonal to monoclinic hafnia was observed. Raman spectroscopy and transmission electron microscopy were employed to further understand the phase evolution. The thermal stability and the influence of amorphous matrix on the coarsening of HfO₂ were also evaluated.     

Impact of interfacial solubility on penetration of metals into dielectrics and the mechanism of failure

Copper solubility in low-k dielectrics has been shown to be a major factor in decreasing the useful lifetime of an interconnect. A number of groups have shown experimentally that increased surface oxygen concentration, increased moisture content in the dielectric, and an increase in interfacial copper concentration from chemical–mechanical polishing all contribute to accelerated failure. Here, we assumed that all these processes led to an increase in the solubility of metal at the SiO₂/metal. We systematically varied the value of the interfacial solubility, C_e over a wide range and showed that the solubility strongly affects the distribution of copper and the local electric field within the dielectric. This changes the mechanism by which failure occurs from one where copper must penetrate all the way through the dielectric to one where copper penetration is limited to a thin layer near the surface. The solubility levels required to alter the failure mechanism, 10²⁶–10²⁷ atoms/m³, are within the realm of possibility and have been reported in the context of fabricating Cu-SiO₂ resistive switching elements for memory applications.     

Interdiffusion study in the Pd–Pt system

Interdiffusion, intrinsic, tracer and impurity diffusion coefficients are calculated in the Pd–Pt system. Interdiffusion coefficients are more or less insensitive to composition change. Activation energy varies in the range of 324–353 kJ/mol. Impurity diffusion coefficients calculated in this study and available tracer diffusion coefficients in pure elements indicate that Pd has higher diffusion rate compared to Pt in pure Pd, whereas, both the elements have similar diffusion rates in Pt. Kirkendall marker experiments indicate that Pd has much higher diffusion rate in Pd3.5at.%Pt compared to Pt.