Improvement of cycle behaviour of SiO/C anode composite by thermochemically generated Li4SiO4 inert phase for lithium batteries

A new anode composite material is prepared by thermal treatment of a blend made of silicon monoxide (SiO) and lithium hydroxide (LiOH) at 550 °C followed by ball milling with graphite. X-ray diffraction pattern confirms the presence of Li₄SiO₄ in the thermally treated (SiO + LiOH) material. The electrode appears to be smooth and glassy as evident from observation with a scanning electron microscope (SEM), possibly due to the presence of nano-silicon and Li₄SiO₄ particles, and exhibits superior performance with a charge capacity of ∼333 mAh g⁻¹ at the 100th cycle with a low-capacity fade on cycling. Cyclic voltammograms of the electrode predict high power capability. On the other hand, the electrode comprising of only SiO and C prepared through ball milling, devoid of Li₄SiO_4, shows hard crust particulates in the electrode exhibiting low charge–discharge capacities with cycling.     

Self-constrained sintering of Al2O3/glass/Al2O3 ceramics by glass infiltration

Though need for precise alignment of interlayer patterning in LTCC application, there have been few reports about zero-shrinkage sintering techniques. In this study, ceramic substrate with minimal x–y shrinkage was prepared by glass infiltration method with ‘Al₂O₃/glass/Al₂O₃’ structure. Glass infiltration into alumina particle layer was observed with variation of both sintering temperature (700?≤?T _sint.?≤?900 °C) and alumina particle size distribution (0.5?≤?D ₅₀?≤?1.8 μm). Since glass had low viscosity enough to infiltrate at 700 °C, infiltration started at that temperature and infiltrated up to 20 μm or so with temperature increase, but infiltration depth did not increase noticeably above 750 °C. Based on these results, when sintered at 900 °C with controlled sheet thickness of both glass and alumina, the shrinkage in x–y direction was calculated as less than 0.2%, with 40% in z direction. Dielectric constant (? _r) measured 6.19 with quality factor (Q) of 552 at 1 GHz of frequency. From these results, it is thought that zero-shrinkage ceramic substrates would be obtained without de-lamination.     

Stable p-type conduction from Sb-decorated head-to-head basal plane inversion domain boundaries in ZnO nanowires

We report that Sb-decorated head-to-head (H-H) basal plane inversion domain boundaries (b-IDBs) lead to stable p-type conduction in Sb-doped ZnO nanowires (NWs) due to Sb and O codoping. Aberration-corrected Z-contrast scanning transmission electron microscopy shows that all of the Sb in the NWs is incorporated into H-H b-IDBs just under the (0001) NW growth surfaces and the (0001) bottom facets of interior voids. Density functional theory calculations show that the extra basal plane of O per H-H b-IDB makes them electron acceptors. NWs containing these defects exhibited stable p-type behavior in a single NW FET over 18 months. This new mechanism for p-type conduction in ZnO offers the potential of ZnO NW based p-n homojunction devices.     

Sensitivities of ozone and fine particulate matter formation to emissions under the impact of potential future climate change

Impact of climate change alone and in combination with currently planned emission control strategies are investigated to quantify effectiveness in decreasing regional ozone and PM2.5 over the continental U.S. using MM5, SMOKE, and CMAQ with DDM-3D. Sensitivities of ozone and PM2.5 formation to precursor emissions are found to change only slightly in response to climate change. In many cases, mass per ton sensitivities to NO(x) and SO2 controls are predicted to be greater in the future due to both the lower emissions as well as climate, suggesting that current control strategies based on reducing such emissions will continue to be effective in decreasing ground-level ozone and PM2.5 concentrations. SO2 emission controls are predicted to be most beneficial for decreasing summertime PM2.5 levels, whereas controls of NO(x) emissions are effective in winter. Spatial distributions of sensitivities are also found to be only slightly affected assuming no changes in land-use. Contributions of biogenic VOC emissions to PM2.5 formation are simulated to be more important in the future because of higher temperatures, higher biogenic emissions, and lower anthropogenic NO(x) and SO2 emissions.     

Effects of Various Transition Metals on the Thermal Oxidative Stabilization of Polyacrylonitrile Nanofibers

Journal of Inorganic and Organometallic Polymers and Materials - In this paper, the polyacrylonitrile (PAN) nanofibers and PAN nanofibers bonded with different transition metal (Fe, Co, Ni, and Cu)...     

A simplified calculation model for the sliding contact boundaries in a hydrostatic piston mechanism

The objective of this study was to discuss simplified calculation models for the piston/cylinder sliding mechanism in which boundary contact partly occurs invariably. An efficient prediction of the boundary leakage and friction is often needed, such as in a swash-plate axial piston machine whose lubrication test is hard to perform due to the mechanism complexity. In order to model this physically uncertain lubrication regime, two calculation models were compared to compute the lubrication behaviors: “rigid boundary model”, whose theoretical concept was previously reported in the literature, and “elastic boundary model”, newly proposed in this study. Developed numerical algorithms commonly facilitated the simultaneous calculation of body motion and fluid film pressure to observe piston motion, reaction forces, and power loss. The results showed that simulations using the elastic boundary model should be more helpful for the prediction in the earlier development stage than the previous model since the methodology provides much less simulation time than full-order calculation, higher accuracy than the rigid model, and useful engineering parameters such as surface stress. The proposed calculation model can be extended to various asymmetrically loaded reciprocating piston mechanisms for efficiently predicting the lubrication behavior.     

High switching performance 0.1-/spl mu/m metamorphic HEMTs for low conversion loss 94-GHz resistive mixers

We report high switching performance of 0.1-/spl mu/m metamorphic high-electron mobility transistors (HEMTs) for microwave/millimeter-wave monolithic integrated circuit (MMIC) resistive mixer applications. Very low source/drain resistances and gate capacitances, which are 56 and 31% lower than those of conventional pseudomorphic HEMTs, are due to the optimized epitaxial and device structure. Based on these high-performance metamorphic HEMTs, a 94-GHz MMIC resistive mixer was designed and fabricated, and a very low conversion loss of 8.2 dB at a local oscillator power of 7 dBm was obtained. This is the best performing W-band resistive field-effect transistor mixer in terms of conversion loss utilizing GaAs-based HEMTs reported to date.     

Optimization of sub-0.1-μm offset Γ-shaped gate MHEMTs for millimeter-wave applications

We examine the effects of device scaling in both vertical and lateral dimensions for the metamorphic high electron mobility transistors (MHEMTs) on the DC and millimeter-wave electrical performances by using a hydrodynamic transport model. The well-calibrated hydrodynamic simulation for the sub-0.1-μm offset Γ-gate In_0.53Ga_0.47As/In_0.52Al_0.48As MHEMTs shows a reasonable agreement with the electrical characteristics measured from the fabricated 0.1 μm devices. We have calibrated all the parameters using the measurement data with various physical considerations to take into account the sophisticated carrier transport physics in sub-0.1-μm devices. Being simulated with these calibrated parameters, the optimum device performance is obtained at a source-drain spacing of 2 μm, a gate length of 0.05 μm, a barrier thickness of 10 nm and a channel thickness of 12 nm.     

Use of polymer nanoparticles as functional nano-absorbents for low-molecular weight hydrophobic pollutants

To use amphiphilic polymer nanoparticles as a new nano-absorbent for improving environmental process, urethane acrylate nonionomer (UAN) chain having hydrophobic polypropylene oxide-based segment and hydrophilic polyethylene oxide-based segment at the same backbone was synthesized and dispersed as nanoparticles at water phase without using a surfactant or dispersion agent. These UAN nanoparticles were converted to crosslinked amphiphilic polymer (CAP) nanoparticles through soap-free emulsion polymerization and suspension agent-free suspension polymerization process. Emulsion polymerization process exhibited higher conversion of polymerization compared to suspension polymerization process. CAP nanoparticles showed interfacial activity and solubilize hydrophobic pollutants (phenanthrene and toluene) like surfactant micelles. This result indicates possible application of CAP nanoparticles as nano-absorbent for improving efficiency of soil washing and micellar-enhanced ultrafiltration (MEUF) process.