Fabrication of a tungsten master stamp using self-ordered porous alumina

We describe the preparation of a tungsten pillar nanoimprint stamp without the use of lithography and etching techniques. Structures with heights of 15 nm were prepared on the basis of self-ordered porous alumina templates and this was followed by DC sputtering of tungsten. The stamp was successfully used to prepare an aluminium surface to obtain highly ordered porous anodic alumina films after a single anodization step. The preparation efficiency for highly ordered porous alumina was dramatically improved as compared to the more conventional two-step anodization–strip-anodization method, as a sacrificial layer with a thickness of a few hundred micrometres was not required. In addition, by fractal calculations, we have evaluated the degree of ordering of the asperities on the nanoimprint master stamp

Low-temperature synthesis of LiFePO4 nanocrystals by solvothermal route

LiFePO4 nanocrystals were synthesized at a very low temperature of 170°C using carbon nanoparticles by a solvothermal process in a polyol medium, namely diethylene glycol without any heat treatment as a post procedure. The powder X-ray diffraction pattern of the LiFePO4 was indexed well to a pure orthorhombic system of olivine structure (space group: Pnma) with no undesirable impurities. The LiFePO4 nanocrystals synthesized at low temperature exhibited mono-dispersed and carbon-mixed plate-type LiFePO4 nanoparticles with average length, width, and thickness of approximately 100 to 300 nm, 100 to 200 nm, and 50 nm, respectively. It also appeared to reveal considerably enhanced electrochemical properties when compared to those of pristine LiFePO4. These observed results clearly indicate the effect of carbon in improving the reactivity and synthesis of LiFePO4 nanoparticles at a significantly lower temperature

Improvement of Heat Transfer Properties through TiO₂ Nanosphere Monolayer Embedded Polymers as Thermal Interface Materials

A thermal interface material (TIM) is a substance that reduces the thermal resistance between a heat source and heat sink, which facilitates heat conduction towards the outside. In this study, a TiO2 nanosphere (NS)-filler based TIM was fabricated via facile processes such as spin-coating and icing methods. Thermal conductivity of the fabricated TiO2 NS-based TIM was enhanced by increasing the loading contents of the TiO2 NS-filler and successfully cooling down the GPU chipset temperature from 62 °C to 50 °C. Moreover, the TIM with the TiO2 NS-monolayer additionally lowered the GPU temperature by 1–7 °C. The COMSOL simulation results show that the TiO2 NS-monolayer, which was in contact with the heat source, boosts the heat transfer characteristics from the heat source toward the inside of the TIM. The suggested metal oxide monolayer-based TIM is an effective structure that reduces the temperature of the device without an additional filler loading, and it is expected to have a wide range of applications for the thermal management of advanced devices

Reconstruction of the Paleo‐Ocean Environment Using Mineralogical and Geochemical Analyses of Mixed‐Type Ferromanganese Nodules From the Tabletop of Western Pacific Magellan Seamount

Abstract Variations in the geochemistry and mineralogical compositions of ferromanganese (Fe‐Mn) nodules are closely related to variations in environmental parameters. Therefore, analysis of Fe‐Mn nodules can reconstruct the paleo‐ocean environment. Here, three differently shaped Fe‐Mn nodules were collected from the open seamount 9‐1 of the western Pacific Magellan Seamount. Geochemical and mineralogical analyses were conducted using micro X‐ray fluorescence (μ‐XRF) and Synchrotron X‐ray powder diffraction to reconstruct the paleo‐ocean environment. We found that the shape of the three nodules was different; however, the variations in their geochemical and mineralogical properties were similar. For all three nodules, the μ‐XRF elemental distribution revealed a distinct alternation between the Mn‐rich and Fe‐rich layers. The Mn‐rich and Fe‐rich layers surrounded the nuclei and appeared as concentric circles. Fe‐rich and Mn‐rich layers exhibited low Mn/Fe ratios (2.5) were dominated by todorokite, respectively. These findings suggest an early diagenesis process at tabletop of the Magellan Seamount. The high contents of Ca and P and the existence of carbonate fluorapatite in the center of Fe‐Mn nodules indicate that the formation of these nodules began during the Miocene phosphatization event (19–16 Ma). In the early stages of nodule formation, a diagenetic process drove Fe‐Mn nodule formation. Because of global cooling from 9 Ma, early diagenesis was weakened, after which the formation of hydrogenetic Fe‐Mn nodules became dominant. As a result, variations in oxygen minimum zones and oxic‐suboxic fronts were recorded in Fe‐Mn nodules from tabletop of the seamount

Efficient Propylene Carbonate Synthesis from Urea and Propylene Glycol over Calcium Oxide–Magnesium Oxide Catalysts

A series of calcium oxide–magnesium oxide (CaO–MgO) catalysts were prepared under the effects of different precipitating agents and using varied Mg/Ca ratios. The physiochemical characteristics of the prepared catalysts were analyzed using XRD, FE-SEM, BET, FTIR, and TG/DTA techniques. Quantification of basic active sites present on the surface of the CaO–MgO catalysts was carried out using the Hammett indicator method. The as-prepared mixed oxide samples were tested for propylene carbonate (PC) synthesis through the alcoholysis of urea with propylene glycol (PG). The effects of the catalyst composition, catalyst dose, reaction temperature, and contact time on the PC yield and selectivity were investigated. The maximum PC yield of 96%, with high PC selectivity of 99% and a urea conversion rate of 96%, was attained at 160 °C using CaO–MgO catalysts prepared using a Mg/Ca ratio of 1 and Na2CO3 as a precipitating agent. The best-performing catalysts also exhibited good reusability without any significant loss in PC selectivity. It is expected that the present study will provide useful information on the suitability of different precipitating agents with respect to the catalytic properties of the oxides of Ca and Mg and their application in the synthesis of organic carbonates

Liquefied-Natural-Gas-Derived Vertical Carbon Layer Deposited on SiO as Cost-Effective Anode for Li-Ion Batteries

International audienceDeposition of a carbon layer on silicon monoxide (SiO) is an attractive method for mitigating the inherent low electrical conductivity and significant volume expansion of SiO, which is a promising anode candidate for Li-ion batteries with high energy density. Herein, we report a method for coating SiO with a vertically grown carbon layer via chemical vapor deposition using low-cost liquefied natural gas (LNG), which is 13 times less expensive than commonly used high-purity CH4. The physical and chemical properties of the carbon-coated samples obtained using CH4 (C-SiO-CH4) and LNG (C-SiO-LNG) were identical, and their electrochemical performances were superior to that of pristine SiO. This low-cost, high-volume manufacturing method promotes the industrialization of Si-C materials for next-generation Li-ion batteries