Effects of nanotalc inclusion on mechanical,microstructural, melt shear rheological,and crystallization behavior of polyamide 6‐based binary and ternary nanocomposites

The objective of the study is to investigate the effect of inclusion of nanotalc on the strength properties of polyamide 6 (PA6)‐based binary and ternary nanocomposites. Binary nanocomposites were prepared by melt compounding of PA6 with varying content of nanotalc (1, 2, and 4 wt%). Ternary nanocomposites were prepared by melt compounding of compatibilized blend of PA 6 and ethylene‐co‐butyl acrylate (EBA elastomer) with varying content of nanotalc (1, 2, and 4 wt%). Both the binary and ternary nanocomposites registered a very high improvement in the strength/stiffness‐related properties at lower filler loading of 1 wt%. Phase morphology of the composites studied by SEM, TEM, and XRD revealed the formation of extended brane‐like structures and delaminated talc layers in the binary nanocomposites. The modulus predicted by Halpin‐Tsai and Mooney equation suggests that the composites retained a very good aspect ratio after melt mixing. Orientation effects of nanotalc enhanced the melt flow behavior in the composites. POLYM. ENG. SCI., 50:1978–1993, 2010. © 2010 Society of Plastics Engineers     

Evolutionary sensitivity-based conceptual design and tolerance allocation for mechanical assemblies

This paper presents a new method based on evolutionary algorithms—Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Differential Evolution (DE)—for the sensitivity-based conceptual design and the tolerance allocation for mechanical assemblies. The approach I of this paper moves the nominal values of non-critical dimensions to a less sensitive portion, and the approach II deals with the allocation of cost-based optimal tolerances. An improved optimization model that considers three objective functions (minimization of the deviation of critical dimensions, manufacturing cost, and the quality loss), eight constraints, and six variables is proposed. To show the effectiveness of the proposed methods, the stepped bar assembly is considered as a numerical example. The results obtained from NSGA-II and DE are compared and analyzed. The results show that the proposed methods are much effective, cost, and time saving than the ones considered in literature.     

Enhancement in gas holdup in bubble columns through use of vibrating internals

Including internals in bubble columns is known to enhance the gas holdup. In this paper, a method to achieve this objective substantially has been proposed via the use of vibrating helical spring internals. Experimental observations on effect of vibrating internals such as vibrating helical springs on gas holdup in bubble columns are presented. Effects of superficial gas velocity, H/D ratio (height of the static liquid to column diameter ratio), volume fraction of helical springs, and thickness of the helical spring wires on hydrodynamics parameters are studied. Increase in gas holdup up to 135% is observed by using vibrating helical spring internals in bubble columns compared to bubble columns without internals. This method offers a simple, cost‐effective, and easy way to enhance gas holdup even at high gas fluxes. It has been reported that this enhancement stems from the fact that the vibrating springs breakup the gas into fine bubbles, which effectively reduces their rise velocity and enhances their average residence time in the liquid column.     

Detailed Physical Characterizations of Cu-rich and Ru-poor (Ru0.9Cu0.1)Sr2YCu2O7.9

The optimized nominal composition, (Ru_0.9Cu_0.1) Sr₂YCu₂O_7.9 sample, has been prepared through high-pressure and high-temperature solid-state densification method. The obtained material has been studied by X-ray (laboratory) diffraction powder technique, magnetization and detailed magneto-transport measurements. The title compound indicates bulk magneto-superconducting properties under field strengths of H=10, 100, 500 and 1000 Oe. It shows diamagnetic transition at T _d=54, 38, 20 and 8 K for H=10, 100, 500 and 1000 Oe, respectively, in the zero-field-cooled susceptibility measurements. The high-field (H=5 and 10 kOe) molar susceptibility measurements show sharp ferromagnetic transition at ∼150 K with reduced molar susceptibility values. The various field dependence of magnetization, M(H), isotherm curves recorded at constant temperatures (5, 10, 25, 50, 100 and 150 K) indicate ferromagnetic saturation, whereas the MH curves measured at 200 and 300 K conditions reveal the paramagnetic state of the compound. Though the sample showed onset transition temperature, T_c^onsetT_{\mathrm{c}}^{\mathrm{onset}}, at ∼34 K under different field strengths (H=0, 10, 30, 50, 70 and 90 kOe), no T_c^R=0T_{\mathrm{c}}^{R=0} is seen down to 2 K. Even under relatively low applied field (ΔH=10 kOe) the title compound shows large negative magnetoresistance (MR) of about 68% at 2 K and increases with increasing the field strength up to ΔH=90 kOe (MR=77% at 2 K). This value is amazing and probably higher than other 1212 type ruthenocuprates. The title compound which shows little negative MR (about 1%) in the high temperature regions (125–300 K) is not affected much by different field strengths. Among the different fixed temperature MR(H) isotherms, the MR(H) curve measured at 5 K shows maximum negative MR of about 47% at 90 kOe compared to other four (T=50, 100, 200 and 300 K) MR(H) curves.     

Synthesis and characterisation of sol gel derived bioactive glass for biomedical applications

Bioactive glasses have been used successfully as bone-filling materials in orthopaedic and dental surgery, but their poor mechanical strength limits their applications in load-bearing positions. Approaches to strengthen materials decrease their bioactivity. In order to realize the optimal matching between mechanical and biological properties, the sol-gel-self propagating method is adopted to prepare gel-derived bioglass bulk: 58S in the system SiO₂–CaO–P₂O₅. The obtained glass was analysed for its composition, crystalinity and morphology through FT-IR, Raman, XRD, STEM and X-ray microanalysis.     

Magnetization Studies of Mercury-Cuprates and Its Precursors

The mercury-cuprates such as (Hg, Cr)/Sr-1201 and (Hg, Re)/Sr-1201 were synthesized by encapsulation-technique at 880–920 °C for 12–16 h, and characterized by power XRD, M(T) and M(H). All the precursors (Sr₂CuO₃, Cr_0.30Sr₂CuO _y or Re_0.10Sr₂CuO _y ) were found to be non-superconducting. The samples with optimal composition (Hg_0.70Cr_0.30)Sr₂CuO_4+δ [(Hg, Cr)/Sr-1201] and (Hg_0.90Re_0.10)Sr₂CuO_4+δ [(Hg, Re)/Sr-1201] are superconducting with T_c^onset ~ 58T_{\rm c}^{{\rm onset}} \sim 58 and ∼54 K, respectively. At low temperatures (below 10 K), on cooling in D.C.-magnetic field of 4 kOe, the sample (Hg, Re)/Sr-1201 shows a dramatic decrease in diamagnetic signal. Further, this effect is also faintly reflected in the M(H) curve. Such a behaviour was not observed in the (Hg, Cr)/Sr-1201 cuprates. We ascribe this effect to a field enhanced paramagnetic contribution possibly arising from mixed valent (6+, 7+ dominant) Re ions in the (Hg, Re)/Sr-1201 cuprates.     

Analytical modeling and simulation of germanium single gate silicon on insulator TFET

This paper proposes a new two dimensional（2D） analytical model for a germanium（Ge） single gate silicon-on-insulator tunnel field effect transistor（SG SOI TFET）. The parabolic approximation technique is used to solve the 2D Poisson equation with suitable boundary conditions and analytical expressions are derived for the surfacepotential,theelectricfieldalongthechannelandtheverticalelectricfield.Thedeviceoutputtunnellingcurrent is derived further by using the electric fields. The results show that Ge based TFETs have significant improvements inon-currentcharacteristics.Theeffectivenessoftheproposedmodelhasbeenverifiedbycomparingtheanalytical model results with the technology computer aided design（TCAD） simulation results and also comparing them with results from a silicon based TFET.     

A novel simulation methodology for full chip-package thermo-mechanical reliability investigations

A methodology for simulating the accurate 3D structural details of a non-planarized technology chips is presented. FEM is a powerful tool used for electrical, thermal and mechanical analysis in the microelectronics industry. Manual geometry and finite element mesh generation of a 3D non-planar chip topology is extremely tedious and time consuming. Therefore, a new method, which is automatic or semi-automatic, is required to drastically reduce the pre-processing effort required for finite element simulations. Our proposed approach uses a virtual semiconductor fabrication technique to create geometry and finite element mesh on complex chip topology features. A microscopic power metal stack of a power IC was simulated to demonstrate this new simulation methodology and the results are presented. These numerical simulations, which included the non-linear behavior in the matrix, show that the detailed information of the large stress and strain gradients in the micro-fields can be obtained.     

Impact of Tuning Molar Ratio in the Starting Materials: <Emphasis Type="Italic">Magneto</Emphasis>-Transport Features of Hybrid YSr<Subscript>2</Subscript>Ru<Subscript>0.9</Subscript>Cu<Subscript>2.1</Subscript>O<Subscript>7.9</Subscript>

The impact of slightly tuning molar ratio in the starting materials on the physical properties of 1212-type rutheno-cuprate, YSr₂Ru_0.9Cu_2.1O_7.9 (nominal) samples prepared under four synthesis approaches are reported. Interestingly, all samples clearly show the differences in the physical properties of the samples prepared under different synthetic protocols. However, neither XRD nor EDX reveal any notable differences in the crystal structure or sample composition. All the samples exhibit magneto-superconducting properties (H _ext=5 Oe) which are slightly varied with synthetic approaches. The high field (H _ext=10 kOe) temperature dependence of magnetization data shows a sharp ferromagnetic transition around 150 K and all the samples obey Curie–Weiss linear behavior above 180 K. The experimental effective paramagnetic moment for the various samples is in the range of 2.5 and 2.7μ _B/Ru which are in line with the literature report. The magnetization, M(H) isotherm curves measured at 5 K and −10 kOe≤H≤10 kOe conditions reveal weak ferromagnetic-like hysteresis loops for all samples with returning moment (M _r) and coercive field (H _c), whereas the high field M(H) loops indicate soft ferromagnetic behaviors with magnetic saturation. The saturation moment of the samples is slightly varied with the synthesis approaches. None of the samples showed bulk superconductivity (T_c^{R = 0})T_{\mathrm{c}}^{R = 0}) down to 2 K, while all samples show onset transitions (T_c^onsetT_{\mathrm{c}}^{\mathrm{onset}}) except the sample prepared by approach-3. The latter approach sample shows semiconducting behavior down to 2 K. The T_c^onsetT_{\mathrm{c}}^{\mathrm{onset}} noticed at 34 K, 12 K, and 6 K for the sample prepared by approach-1, 2, and 4, respectively. The nearly linear dependence suggests that hopping conduction is dominant in certain temperature range for all samples. The magneto-transport features of these samples exhibit maximum magnetoresistance (MR) at low temperatures. Remarkably, the sample prepared by approach-1 shows largest −MR about 77% at low temperature 2 K and H=90 kOe which stimulates for further investigations. Among the four synthesis approaches employed in the present study, we can probably suggest that the approach-1 (0.5Y₂O₃+0.5SrO₂+1.5SrCuO₂+0.9RuO₂+0.6CuO) is the preferable method to achieve the best sample (in terms of magneto-transport features).