Two-step Thermal Treatment Research Articles

A direct metal transfer method for cross-bar type polymer non-volatile memoryapplications

Polymer non-volatile memory devices in8 × 8 array cross-bar architecture were fabricated by a non-aqueous direct metal transfer (DMT)method using a two-step thermal treatment. Top electrodes with a linewidth of2 µm were transferred onto the polymer layer by the DMT method. The switchingbehaviour of memory devices fabricated by the DMT method was very similar tothat of devices fabricated by the conventional shadow mask method. Thedevices fabricated using the DMT method showed three orders of magnitude ofon/off ratio with stable resistance switching, demonstrating that the DMT method can be asimple process to fabricate organic memory array devices.

Effect of synthetic conditions on the electrochemical properties of LiMn 0.4Fe 0.6PO 4/C synthesized by sol–gel technique

Carbon-coated LiMn 0.4Fe 0.6PO 4 (LMFP) was synthesized by sol–gel technique using citric acid as foaming agent and carbon precursor. To evaluate the effect of synthetic conditions on the electrochemical properties of LMFP for use as cathode active material, the carbon-coated olivines were synthesized by a two-step thermal treatment at different temperatures. The composites were characterized by elemental analysis, XRD, SEM, TEM, Raman microprobe spectroscopy and their electrochemical properties were also studied. The composite that shows the better electrochemical performance has more porous structure, lower D/G band ratio in Raman spectra, and charge and discharge capacities of same 155 mAh g −1 with higher material utilization of 97% at 0.1 C-rate (0.05 mA cm −2). The material exhibiting the better performance was also incorporated in a polymer electrolyte hosted in an electrospun P(VdF-HFP) membrane. The lithium polymer battery composed of LiMn 0.4Fe 0.6PO 4 cathode and polymer electrolyte showed a good cycling performance with the initial discharge capacity of 146 mAh g −1.

Nonaqueous Nanoscale Metal Transfer by Controlling the Stickiness of Organic Film

Nanoscale metal patterns were successfully reproduced on top of a functional organic layer by a direct metal-transfer technique (DMT). A gold film deposited on the protruding features of a stamp was transferred to the organic layer by controlling its stickiness through a two-step thermal treatment. The process was also suitable for the transfer of highly adhesive metal materials to the stamp surface by using an additional gold layer. Chromium nanowires at 70 nm half-pitch were faithfully produced without any damage to the organic active layer.

Preparation of stationary phases for reversed-phase high-performance liquid chromatography using thermal treatments at high temperature

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 °C for 24 h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4 h at higher temperatures (150–400 °C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, 29Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 °C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 °C and an increase in the resolution of the components, mainly for the phase heated at 300 °C. Such results demonstrate that a two-step thermal treatment (100 °C then 150–300 °C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography.

Three dimensional nanowire networks and complex nanostructures of indium oxide

Elongated In2O3 micro- and nanostructures have been grown by two-step thermal treatments of compacted InN powder, at temperatures between 350 and 700°C. Different thermal treatments have been found to induce the growth of structures with different sizes and morphologies as wires, rods, or arrows. The experimental conditions leading to the different structures, as well as the evolution of the structures during the treatments, have been investigated. Some treatments lead to large scale formation of three dimensional networks of the mentioned structures. The mechanism of network formation is discussed. The structures have been characterized by cathodoluminescence, scanning electron microscopy, and x-ray diffraction.

Improved thermal resistance of spherical BaMgAl 10O 17:Eu blue phosphor prepared by spray pyrolysis

The thermal degradation characteristics of BaMgAl 10O 17:Eu (BAM) blue phosphor with spherical shape were investigated. In this work, we developed a strategy that is very simple, but very effective to minimize the thermal degradation of BAM blue phosphor. In order to improve the thermal degradation properties of BAM particles prepared by spray pyrolysis, the as-prepared particles were treated by a two-step post thermal treatment. That is, the particles were treated under a vacuum atmosphere at 400 °C and successively in situ reduced at 1400 °C. It was found that the two-step treatment effectively reduces the color shift of the BAM particles, which is known as a big problem generally observed in the fabrication processes of plasma display panels (PDPs). According to FT-IR analysis, the vacuum treatment produced a stable hydrophobic surface which was maintained even after the baking process. For further improving the photoluminescence intensity under VUV irradiation, in this work, the surface of BAM particles treated by the above two-step treatment was modified with alkyl and organosilane groups. As a result, the photoluminescence intensity was enhanced. Therefore, it was concluded that removing the water (OH groups) existing on the surface or in the matrix as well as making a hydrophobic surface are promised to minimize the thermal degradation of BAM particles.

Phase formation in iron-containing titanium aluminide during two-step heat treatment

Processes occurring in a γ-base TiAl alloy containing 2 at.% Fe during two-step thermal treatment were investigated. Samples held at 1300 °C for 90 min were transferred to an intermediate temperature (in the range 700–1070 °C), aged for 2 h and water quenched. The decomposition of the high temperature B2 FeTi structure containing 42% Al was in the center of the research. This decomposition occurs by two successive reactions: depletion in Al followed by decomposition of the depleted phase into stable iron-alloyed α 2-Ti 3Al (Ni 3Sn type) and the ternary τ 2-Al 2TiFe (Mn 23Th 6 type). The diffusion required for the depletion reaction is governed by large values of the concentration gradient of the M Fe–Al and M Ti–Al diffusion potentials. It is shown that the diffusion is sufficiently fast to permit the depletion reaction at all the intermediate temperatures used. The driving forces were found for both reactions using the quasi-chemical model for the Gibbs energy. The rate of the τ 2+α 2 nucleation was estimated; it has a maximum in the vicinity of 800 °C. Residual FeTi(Al) depleted in Al was found after aging at all intermediate temperatures, except at 800 °C. At this temperature the depleted phase decomposes completely to a very fine mixture of τ 2 and α 2.

Preparation of LiCoO 2 from spent lithium-ion batteries

A recycling process involving mechanical, thermal, hydrometallurgical and sol–gel steps has been applied to recover cobalt and lithium from spent lithium-ion batteries and to synthesize LiCoO 2 from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt can be concentrated with a two-step thermal and mechanical treatment. The leaching behavior of lithium and cobalt in nitric acid media is investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO 3 solution is found to be an effective reducing agent by enhancing the leaching efficiency. Of the many possible processes to produce LiCoO 2, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO 2 with nitric acid, the molar ratio of Li to Co in the leach liquor is adjusted to 1.1 by adding a fresh LiNO 3 solution. Then, 1 M citric acid solution at a 100% stoichiometry is added to prepare a gelatinous precursor. When the precursor is calcined at 950 °C for 24 h, purely crystalline LiCoO 2 is successfully obtained. The particle size and specific surface-area of the resulting crystalline powders are 20 μm and 30 cm 2 g −1, respectively. The LiCoO 2 powder is found to have good characteristics as a cathode active material in terms of charge–discharge capacity and cycling performance.

Infrared response of oxygen precipitates in silicon: Experimental and simulated spectra

A suitable choice of one sample among several silicon wafers subjected to two-step thermal treatments for oxygen precipitation permits to reveal a complete series of infrared absorption peaks related to the precipitates formed in the crystal. Structured spectra are observed at 7 K and can be interpreted as due to SiO2 precipitates with different shapes and concentrations.

Thermal treatment of sediments as a function of temperature and reacting atmosphere

Samples of polluted sediments were submitted to a two-step thermal treatment either in inert (pyrolysis) or oxidative (combustion) atmosphere. Tests were carried out at 400, 650 and 900°C and a residence time of 2 s. Gaseous effluents were collected on-line and analyzed via GC-MS. A detailed description of the main classes of substances generated as a function of temperature and reacting atmosphere was obtained, and conditions leading to a complete destruction of the evolved pollutants were determined. On increasing the pyrolysis temperature, a cleaner sediment residue was obtained, but the pyrolyzate produced at the highest temperatures was rich in simple and poly aromatic hydrocarbons and other nitrogen-, chlorine- or oxygen-containing products of strong environmental concern. When the thermal treatment was performed in the presence of air, most of these substances were not found in the effluent at 650°C, even though temperatures as high as 900°C, in the presence of a large oxygen excess, were required to achieve a complete destruction of all the organics.

Physical Aging in Amorphous Poly(ethylene terephthalate). 2. Isothermal Volume Recovery After Two Temperature Jumps.

The dependence of physical aging kinetics on glass-forming histories and thermal treatments was examined for amorphous poly (ethylene terephthalate) (PET) glasses. The samples were subjected to two-step thermal treatment : first, temperature drop from equilibrium at 80°C to 60°C and then isothermal annealing ; second, temperature jump to aging temperature Ta. Isothermal volume recovery was measured after the second step to Ta (70°C> Ta>60°C) below the glass transition temperature (T). The volume recovery curves were represented by a plot of normalized fractional free volume (=(V-V∞)/V∞, where V∞ is the equilibrium value of specific volume V) vs. logarithm of aging time. All curves, showing the well known “memory effect” characteristic, could be described nearly by a six-parameter phenomenological model postulating a multiplicity of independent relaxation modes with distinct relaxation times. The model parameters determined to fit the data were found to be greatly dependent on the glass-forming history, but weakly dependent on the thermal treatment conditions. Furthermore, the individual recovery curves could be superimposed by horizontal shifts along the logarithm axis of aging time.

Visible photoluminescence from pressure annealed intrinsic Czochralski-grown silicon

Visible luminescence from thermal treated intrinsic Czochralski-grown silicon is reported. Oxygen precipitates were formed in a nearly oversaturated silicon by a two-step thermal treatment with auxiliary use of high pressures. A wide photoluminescence band peaked at about 2.3 eV is observed in those samples for which the first treatment was performed at a relatively high temperature and which show a higher amount of oxygen precipitates and oxygen related defects. Scanning electron microscopy of the best performing samples show the presence of submicron conglomerates on the surface. We have tentatively attributed the luminescence emission to the defects in the suboxide SiOx phase formed in the oxygen precipitates.

On the two-step ageing of a commercial Al - Zn - Mg alloy; a study by positron lifetime spectroscopy

Formation of Guinier - Preston zones and precipitation, induced by two-step ageing thermal treatments in an age-hardenable commercial Al - Zn - Mg-based alloy, have been studied by positron lifetime spectroscopy and Vickers microhardness measurements. In particular, an initial softening of the specimens, occurring in the early stages of the second ageing step (artificial ageing at ), appears to be correlated with a strong decrease in the positron lifetime, which indicates a partial dissolution of the GP zones. If the treatment at is interrupted at this stage, and the ageing continues at a lower temperature (either room temperature or ), the positron lifetime and the microhardness recover to the values reached at the end of the first ageing step (natural ageing at room temperature for five days). The kinetics of this process is discussed in terms of reconstruction of GP zones; the activation energy value of this process is also obtained.

Oxygen Precipitation Nonuniformity for Thermal History Around 723K During Cz Crystal Growth

ABSTRACTWe investigated phenomena of oxygen precipitation nonuni-formity along crystal growth axis due to different thermal histories during CZ crystal growth. The oxygen precipitation process employed in this paper was two-step thermal treatments consisting of the first annealing in nitrogen ambient at 1073K for 4 hrs and the second annealing in dry oxygen ambient at 1273K for 16 hrs. The amount of the oxygen precipitation at the shoulder of a silicon single crystal was higher than the one at the tail end. We found this nonuniform distribution profile was due to the thermal history around 723K during crystal growth. Such an nonuniformity could be improved remarkably by adding a preannealing in dry oxygen ambient at 723K for 2 hrs before the two-step thermal treatment.

The Effect of D-Defect in Silicon Single Crystal on Oxygen Precipitation

ABSTRACTWe investigated the effect of D-defect in CZ silicon single crystals on the oxygen precipitation by two-step thermal treatments consisting of the first annealing in nitrogen ambient at 1073K and the second annealing in dry oxygen ambient at 1273K. The density of D-defect was measured by counting ‘flow patterns’ using an optical microscope after preferential etching in Secco's solution for 30 minutes. It was found that the amount of oxygen precipitation along the growth axis was not affected by D-defect. The predominant factor of the oxygen precipitation after the two-step thermal process is the nuclei of oxygen precipitation generated around 723K during CZ crystal growth.

Silicon on quartz by solid-state diffusion bonding (SSDB) technology

Silicon wafer and quartz have been successfully bonded together by a two-step thermal treatment process. SIMS measurements shows that after molecular surface activated solvent treatment, the amount of OH on the silicon or quartz surface, which is essential to the first step (low-temperature) bonding strength, is one order of magnitude higher than that on the original silicon or quartz surface. After a high-temperature (850–1250°C) solid-state diffusion process, the bonding strength between silicon and quartz is greatly increased to 150–185 kg/cm2. The material and electrical properties of the silicon on quartz substrate compares favourably with those of the bulk silicon wafer.

A New Method of Preparing θ-Alumina and the Interpretation of Its X-Ray-powder Diffraction Pattern and Electron Diffraction Pattern

Abstract Highly crystallized θ-alumina was obtained by a two-step treatment, by hydrothermal and thermal treatment, of η-alumina. Its X-ray-powder diffraction pattern was interpreted based on the structure of θ-gallia, and least-squares refinements were carried out. The electron diffraction pattern of θ-alumina from boehmite was also interpreted, and the directional relations between the phases were established.