Investigation of the influence of thermostat configurations on the mechanical properties of carbon nanotubes in molecular dynamics simulations

The effect of thermostat configurations on the mechanical behavior of empty and butane (n-C4H10) filled (10, 10) carbon nanotubes (CNTs) is examined using classical, atomistic, molecular dynamics (MD) simulations. In particular, the influence of different types of thermostats, relative numbers of thermostat atoms, and rates of deformation are considered. The compressive forces on the atoms are calculated using the second generation reactive empirical bond-order potential. The results indicate that use of a Langevin thermostat leads to a substantial dependency of the results of CNT compression on the number of thermostat atoms and the rate of deformation. On the other hand, the Nosé-Hoover and the velocity rescaling thermostats exhibit consistent mechanical responses during CNT compression regardless of the relative number of thermostat atoms. However, the Nosé-Hoover thermostat fails to maintain the system temperature at a constant value during the compression process. Thus, this study indicates that the Langevin and velocity rescaling thermostats are more appropriate for use in classical MD simulations of CNT systems than the Nosé-Hoover thermostat, and reveals the conditions under which these thermostats should be used for optimal consistency.     

Decrease in work function of boron ion-implanted ZnO thin films

We have fabricated boron ion-implanted ZnO thin films by ion implantation into sputtered ZnO thin films on a glass substrate. An investigation of the effects of ion doses and activation time on the electrical and optical properties of the films has been made. The electrical sheet resistance and resistivity of the implanted films are observed to increase with increasing rapid thermal annealing (RTA) time, while decreasing as the ion dose increases. Without any RTA process, the variation of the carrier density is insensitive to the ion dose. With the RTA process, however, the carrier density of the implanted films increases and approaches that of the un-implanted ZnO film as the ion dose increases. On the other hand, the carrier mobility is shown to decrease with increasing ion doses when no RTA process is applied. With the RTA process, however, there is almost no change in the mobility. We have achieved the optical transmittance as high as 87% within the visible wavelength range up to 800 nm. It is also demonstrated that the work function can be engineered by changing the ion dose during the ion implantation process. We have found that the work function decreases as the ion dose increases.     

Effects of substrate temperature on the magnetic and electrical properties of cobalt ferrite/metal composite thin films

The magnetic and electrical properties of the cobalt ferrite/metal composite thin films, prepared by reactive sputtering, were studied as a function of substrate temperature. With increasing substrate temperature, the saturation magnetization of the thin films increased owing to precipitation of the Co_0.67Fe_0.33 phase. Also, the electrical resistivity of the thin films decreased. From Hall experiments, the decrease of electrical resistivity of the composite thin films was mainly attributed to the increase of electron concentration. The Seebeck coefficient measurement shows that the electrical conduction mechanism of the thin films containing 37.8 and 33.7 at % Co changes from p-type to n-type and that of the thin films containing 28.5 at % Co remains n-type with increasing substrate temperature. This might be attributed to the change in composition of the cobalt ferrite matrix to Fe-excess with precipitation of Co-rich Fe alloy. ©1999 Kluwer Academic Publishers     

Effect of Direct Reduced Iron (DRI) on Dephosphorization of Molten Steel by Electric Arc Furnace Slag

Metallurgical and Materials Transactions B - We investigated the effect of direct reduced iron (DRI) addition on dephosphorization of molten steel by electric arc furnace (EAF) slag at...     

Use of Industrial Waste (Al-Dross,Red Mud,Mill Scale) as Fluxing Agents in the Sulfurization of Fe-Ni-Cu-Co Alloy by Carbothermic Reduction of Calcium Sulfate

The use of industrial waste [mill scale (MS), red mud (RM), Al-dross (AD)] as fluxing agents in the sulfurization of Fe-Ni-Cu-Co alloy to matte (Fe-Ni-Cu-Co-S) by carbothermic reduction of CaSO₄ was investigated at 1673 K (1400 °C). The sulfurization efficiency (SE) was 76 (± 2) pct at RM or AD single fluxing. However, SE drastically increased to approximately 89 pct at a ‘5AD + 5MS’ combination, which was equivalent to reagent-grade chemical ‘5Al₂O₃ + 5Fe₂O₃’ fluxing (SE = 88 pct). The present results can be used to improve the cost-effective recovery of rare metals (Ni and Co) from deep sea manganese nodules.     

Reflective color display using thermochromic pigments

A reflective thermochromic display fabricated by a very simple method using three kinds of thermochromic pigments is produced and its thermo-optical characteristics are investigated. The display exhibits maximum red, green, and blue reflectances of 38%, 30%, and 35%, respectively. The reflective display cell shows continuous gray color with changing temperature, which is crucial for multicolor displays. It also shows an excellent viewing angle above 80° without any of the additional optical components that are required in liquid crystal displays. We expect that this display technology will be used for outdoor billboard information display applications.     

Electrochemical properties of magnesium doped LiFePO4 cathode material prepared by sol–gel method

Magnesium doped Li_1?2xMg_xFePO₄/C (x = 0.00, 0.01, 0.03, 0.05) cathode materials were synthesized by sol–gel method, and the effect of magnesium doping as well as its content on the electrochemical properties for lithium batteries was also investigated_. Their morphology was studied with field emission scanning electron microscope and Li_1?2xMg_xFePO₄ materials showed the olivine phase without impurities. The thin carbon layer of Li_1?2xMg_xFePO₄/C was confirmed by high resolution transmission electron microscopy. The magnesium doped Li_1?2xMg_xFePO₄/C particles were smaller than those undoped. The Li_1?2xMg_xFePO₄/C materials showed better cycling behavior than undoped LiFePO₄, especially at high C-rate in which Li_0.94Mg_0.03FePO₄/C composition exhibited the best electrochemical properties.     

Nanotube-bridged wires with sub-10 nm gaps

We report a simple but efficient method to synthesize carbon nanotube-bridged wires (NBWs) with gaps as small as 5 nm. In this method, we have combined a strategy for assembling carbon nanotubes (CNTs) inside anodized aluminum oxide pores and the on-wire lithography technique to fabricate CNT-bridged wires with gap sizes deliberately tailored over the 5-600 nm range. As a proof-of-concept demonstration of the utility of this architecture, we have prepared NBW-based chemical and biosensors which exhibit higher analyte sensitivity (lower limits of detection) than those based on planar CNT networks. This observation is attributed to a greater surface-to-volume ratio of CNTs in the NBWs than those in the planar CNT devices. Because of the ease of synthesis and high yield of NBWs, this technique may enable the further incorporation of CNT-based architectures into various nanoelectronic and sensor platforms.     

Synthesis of TaZnO thin films using combinatorial magnetron sputtering and its electrical, structural and optical properties

The structural, electrical, and optical properties of tantalium zinc oxide (TaZnO) thin films grown using combinatorial magnetron sputtering system were investigated. To explore the effects of film thickness and post annealing treatment on the properties of the films, we have fabricated TaZnO sample libraries having different thicknesses and carried out post annealing treatment. Sample libraries fabricated at room temperature showed the resistivity ranged 2.1 to approximately 7.1 x 10(-3) Omega cm, while the films post annealed at 200 degrees C under 1 mTorr exhibited the resistivity as low as 1.2 x 10(-3) Omega cm. XRD measurements revealed that the film structure was strongly depended on the film thickness, showing that the structure was changed from amorphous to polycrystalline with increasing the film thickness. Furthermore, it was found that figure of merit (0TC), which was determined by T% and Rs of the TaZnO films, showed maximum value as the films with a thickness of 230 nm was post-annealed at 200 degrees C under vacuum of 1 mTorr.     

Magnesium-doped zinc oxide electrochemically grown on fluorine-doped tin oxide substrate

Nanostructures of magnesium (Mg) doped Zinc oxide (ZnO) were successfully deposited on conducting fluorine-doped tin oxide (FTO) coated glass plates by cathodic electrochemical deposition method at different potentials and temperature conditions. The deposited samples were characterized by XRD and SEM techniques to confirm their structures, morphologies and optical properties. These measurements show that Mg doped ZnO has a wurtzite structure and that the strongest intensity of the (002) peak is found at 60 degrees C and -1.0 V. Tunable transmittance of Mg doped ZnO has a band gap energy from 3.45 eV to 3.82 eV, which is the direct evidence of doping.