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Annealing Conditions (annealing + condition)
Selected AbstractsCompetitive Abnormal Grain Growth between Allotropic Phases in Nanocrystalline NickelADVANCED MATERIALS, Issue 10 2010L. N. Brewer Electron backscatter diffraction-generated phase map showing the distribution of the abnormally grown grains for both the face centered cubic (red) and hexagonal close packed (blue) phases. Annealing condition was 17,h at 548,K. [source] Time-Dependent Morphology Evolution by Annealing Processes on Polymer:Fullerene Blend Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Jang Jo Abstract Changes in the nanoscale morphologies of the blend films of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), for high-performance bulk-heterojunction (BHJ) solar cells, are compared and investigated for two annealing treatments with different morphology evolution time scales, having special consideration for the diffusion and aggregation of PCBM molecules. An annealing condition with relatively fast diffusion and aggregation of the PCBM molecules during P3HT crystallization results in poor BHJ morphology because of prevention of the formation of the more elongated P3HT crystals. However, an annealing condition, accelerating PCBM diffusion after the formation of a well-ordered morphology, results in a relatively stable morphology with less destruction of crystalline P3HT. Based on these results, an effective strategy for determining an optimized annealing treatment is suggested that considers the effect of relative kinetics on the crystallization of the components for a blend film with a new BHJ materials pair, upon which BHJ solar cells are based. [source] Impurity free vacancy disordering of self-assembled InGaAs quantum dots by using PECVD-grown SiO2 and SiNx capping filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003J. H. Lee Abstract Impurity free vacancy disordering (IFVD) of InGaAs self-assembled quantum dots (SAQDs) grown by metal organic chemical vapor deposition (MOCVD) method has been carried out at 700,°C for the time range from 1 min to 4 min by using SiO2 and SiNx,SiO2 dielectric capping layers. The photoluminescence (PL) peak was blue shifted up to 157 meV and its full width at half maximum (FWHM) was narrowed from 76 meV to 47 meV as the annealing time increased. The integrated PL intensity was increased after the thermal annealing, which may be attributed to a defect quenching. There was an optimum annealing condition to get the largest integrated PL intensity for each dielectric capping. SiNx,SiO2 double capping layers have been found to induce larger integrated PL intensity and better carrier confinement after the thermal annealing of SAQDs compared to SiO2 single capping layer, even though SiNx,SiO2 double capping induced larger blue-shift than SiO2 single capping. [source] Depth profile of thermal donors in NTDCZSiPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2003Y. X. Li Abstract The depth profile of thermal donors (TDs) produced by annealing neutron transmutation-doped Czochralski silicon (NTDCZSi) at high temperatures above 1000 °C first and then at 450,°C has been studied by means of the thermal conversion spreading resistance (TCSR). The concentration of the TDs increases with the distance from the surface of the sample, and its depth profile can be described by the error function when the annealing temperature is low or the annealing time is short. A peak is formed in the depth profile under the annealing condition of 1100,°C for 4 h. Combining with an infrared absorption study, it is found that the curves of the diffusivity coincide with the loss of interstitial oxygen. These results indicate that the distribution of the TDs depends on both the out-diffusion and the precipitation of oxygen. Neutron irradiation accelerates the out-diffusion of the oxygen in the surface region of the silicon and the oxygen precipitation in the bulk. [source] Optimization of the Magnetic Properties of FePd Alloys by Severe Plastic Deformation,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Abdelahad Chbihi Abstract A FePd alloy was nanostructured by severe plastic deformation following two different routes: ordered and disordered states were processed by high pressure torsion (HPT). A grain size in a range of 50 to 150,nm is obtained in both cases. Severe plastic deformation induces some significant disordering of the long range ordered L10 phase. However, transmission electron microscopy (TEM) data clearly show that few ordered nanocrystals remain in the deformed state. The deformed materials were annealed to achieve nanostructured long range ordered alloys. The transformation proceeds via a first order transition characterized by the nucleation of numerous ordered domains along grain boundaries. The influence of the annealing conditions (temperature and time) on the coercivity was studied for both routes. It is demonstrated that starting with the disorder state prior to HPT and annealing at low temperature (400,°C) leads to the highest coercivity (about 1.8,kOe). [source] Defect-Related Emissions and Magnetization Properties of ZnO NanorodsADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Bharati Panigrahy Abstract A clear correlation between defect-related emissions and the magnetization of ZnO nanorods synthesized by a one-step aqueous chemical method is demonstrated. The relative contribution of the emission bands arising from various types of defects is determined and found to be linked with the size of the nanorods and annealing conditions. When the size of the nanorods and the annealing temperature are increased, the magnetization of pure ZnO nanorods decreases with the reduction of a defect-related band originating from singly charged oxygen vacancies (). With a sufficient increase of annealing temperature (at 900,°C), the nanorods show diamagnetic behavior. Combining with the electron paramagnetic resonance results, a direct link between the magnetization and the relative occupancy of the singly charged oxygen vacancies present on the surface of ZnO nanorods is established. [source] Blue Luminescence of ZnO Nanoparticles Based on Non-Equilibrium Processes: Defect Origins and Emission ControlsADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Haibo Zeng Abstract High concentrations of defects are introduced into nanoscale ZnO through non-equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420,nm (2.95,eV,<,Eg,=,3.26,eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488,nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial-zinc-related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as-prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co-emission of blue and green emissions and peak adjustment from blue to yellow. [source] Cover Picture: Tuning the Dimensions of C60 -Based Needlelike Crystals in Blended Thin Films (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 6 2006Mater. Abstract A new ordered structure of the C60 derivative PCBM is obtained in thin films based on the blend PCBM:P3HT, as detailed by Swinnen, Manca, and co-workers on p.,760. Needlelike crystalline PCBM structures, whose dimensions and spatial distribution ca be tuned by adjusting the blend ratio and annealing conditions, are formed. In typical solar-cell applications of these blended films, these results indicate that during long-term operation under normal conditions (50,70,°C) morphology changes and a decrease in cell performance could occur. A new ordered structure of the C60 derivative PCBM ([6-6]-phenyl C61 -butyric acid methyl ester) is obtained in thin films based on the blend PCBM:regioregular P3HT (poly(3-hexylthiophene)). Rapid formation of needlelike crystalline PCBM structures of a few micrometers up to 100,,m in size is demonstrated by submitting the blended thin films to an appropriate thermal treatment. These structures can grow out to a 2D network of PCBM needles and, in specific cases, to spectacular PCBM fans. Key parameters to tune the dimensions and spatial distribution of the PCBM needles are blend ratio and annealing conditions. The as-obtained blended films and crystals are probed using atomic force microscopy, transmission electron microscopy, selected area electron diffraction, optical microscopy, and confocal fluorescence microscopy. Based on the analytical results, the growth mechanism of the PCBM structures within the film is described in terms of diffusion of PCBM towards the PCBM crystals, leaving highly crystalline P3HT behind in the surrounding matrix. [source] Effect of wood flour loading and thermal annealing on viscoelastic properties of poly(lactic acid) composite filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010M. Hrabalova Abstract Poly(lactic acid) (PLA) films filled with up to 50 wt % softwood flour were prepared by melt compounding and thermocompression. Thermal annealing of the melt was performed at temperatures from 90°C to 120°C, for 45 min. Responses on polymer-filler interactions, viscoelastic properties, crystallinity of PLA as well as PLA-wood flour-filled films were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The effectiveness of fillers on the storage moduli (C) was also calculated. The results reveal that wood flour (WF) in conjunction with thermal annealing affected the melting behavior of PLA matrix, and the glass transition temperature. It was further found that the effectiveness of the wood filler in biocomposites widely improved with thermal annealing as well as with higher WF concentration. Finally, it was found that the compatibility between WF and the PLA matrix can be improved when suitable annealing conditions are applied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Perfluorosulfonic acid,Tetraethoxysilane/polyacrylonitrile (PFSA-TEOS/PAN) hollow fiber composite membranes prepared for pervaporation dehydration of ethyl acetate,water solutionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Hai-Kuan Yuan Abstract Preparation of organic-inorganic composite membranes and their pervaporation (PV) permeation and separation characteristics for the aqueous solution of ethyl acetate were described. Polyacrylonitrile (PAN) hollow fiber ultrafiltration membrane as support membrane, the mixtures of perfluorosulfonic acid (PFSA) and tetraethoxysilane (TEOS) by the sol-gel reaction as the coating solution, the PFSA-TEOS/PAN hollow fiber composite membranes by the different annealing conditions were prepared. The swelling of PFSA in ethyl acetate aqueous solutions was inhibited with addition of TEOS. The PFSA-TEOS/PAN composite membranes containing up to 30 wt % TEOS in coating solution exhibited high selectivity towards water, then the selectivity decreased and permeation flux increased with increasing the TEOS concentration more than 30 wt %. When the PFSA-TEOS/PAN composite membranes were annealed, the separation factor increased with increasing annealing temperature and time. Higher annealing temperature and longer annealing time promoted the crosslinking reaction between PFSA and TEOS in PFSA-TEOS/PAN composite membranes, leading to the enhanced selectivity towards water. For the PFSA/PAN and PFSA-TEOS/PAN composite membrane with 5 and 30 wt % TEOS annealed at 90°C for 12 h, their PV performance of aqueous solution 98 wt % ethyl acetate were as follows: the separation factors were 30.8, 254 and 496, while their permeation flux were 1430, 513 and 205 g/m2 h at 40°C, respectively. In addition, the PV performance of PFSA-TEOS/PAN composite membranes was investigated at different feed solution temperature and concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Comprehensive Linkage of Defect and Phase Equilibria through Ferroelectric Transition Behavior in BaTiO3 -Based Dielectrics: Part 1.JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Defect Energies Under Ambient Air Conditions Defect and phase equilibria have been investigated via the ferroelectric phase transition behavior of pure and equilibrated nonstoichiometric BaTiO3 powder samples. Through fabricating the BaTiO3 materials under highly controlled conditions to preserve the equilibrium conditions with respect to Ba/Ti ratio, annealing temperature (T), and oxygen partial pressure (PO2), systematic variations in the phase transition temperature can be noted with respect to Ba/Ti ratio and T. From the data extracted, we can then determine solubility limits. Equilibrating the defect reactions at the solubility limits provides a direct approach to identify and calculate the defect energetics. The phase transition temperature decreased with increasing concentration of the TiO2 partial-Schottky defects (BaTi1,,O3,2,) and the BaO partial-Schottky defects (Ba1,,TiO3,,), and showed discontinuous changes in the two-phase region. The formation enthalpy and entropy for the partial-Schottky defect reactions was evaluated to be 2.32±0.1 eV and 10.15±0.7 kB for the BaO partial-Schottky defect, and 2.89±0.1 eV and 8.0±1.5 kB for the TiO2 partial-Schottky defects equilibrated under air annealing conditions. [source] Formation of ohmic contacts to ultra-thin channel AlN/GaN HEMTsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Tom Zimmermann Abstract AlN/GaN-based high electron mobility transistors with ultra-thin AlN barriers of 2.3 - 5 nm are attractive candidates for very high speed applications owing to the aggressive scalability such structures afford. We report the first study on formation of ohmic contacts to these high quality ultra-thin channel heterostructures (ns > 1x1013 cm,2 and , > 900 cm2/Vs) with systematically varying barrier thicknesses. While the conventional ohmic contacts to AlGaN/GaN structures generally require high temperature annealing, these ohmic contacts were found to behave ohmic or near ohmic as-deposited. Annealing (400-860 0C) improves the contact resistance to a range of 0.8 - 2 ohm-mm but the annealing conditions strongly depend on the AlN thickness as well as the heterostructure quality (,). All alloyed contacts show smooth morphology, making them suitable for e-beam lithographically defined gate patterning. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Metalorganic Chemical Vapor Deposition Growth of a GaN Epilayer on an Annealed GaN Buffer LayerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003F. Degave Abstract We investigated the growth of an epitaxial layer deposited on an annealed buffer layer using transmission electron microscopy. It is shown that crystalline quality of the epitaxial layer depends on the annealing conditions of the buffer layer. Dislocations and formation of V-shaped defects are observed and may originate from the structure and morphology of the buffer layer. [source] Preparation and characterization of nylon 6/organoclay nanocomposite filament fibersPOLYMER COMPOSITES, Issue 3 2009Kap Jin Kim A series of nylon 6 (NY6)/organoclay nanocomposites were prepared via in situ polymerization of ,-caprolactam in the presence of 1,2-aminododecanoic acid-intercalated montmorillonite (ADA-MMT) organoclay (1,5 wt%) using 6-aminocaproic acid as polymerization catalyst. The extent of organoclay dispersion in NY6 matrix was analyzed using WAXD and SEM measurements. DSC studies revealed marginal shift in melting and melt-crystallization peaks toward lower temperature with increasing clay content. Melt viscosity studies for NY6/ADA-MMT exhibited higher shear-thinning behavior than neat NY6 probably due to the slip between NY6 matrix and exfoliated organoclay platelets during shear flow. The prepared nanocomposites were melt-spun and studied for their property improvements against varying clay content, draw ratios, and annealing conditions. Birefringence and sonic velocity values increased initially at lower draw ratios (,2.5) due to increased orientation of molecular chains along the drawing direction but saturated at higher draw ratio (3.0) for all the samples. At the same draw ratio; compared to neat NY6, NY6/organoclay fibers showed increased chain orientation along the drawing direction which can be attributed to the "tethering effect" of organoclay on NY6 matrix. The initial modulus and stress at break were sensitive to factors such as draw ratio, clay content, and annealing conditions. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Crystallization and melting behavior of multi-walled carbon nanotube-reinforced nylon-6 compositesPOLYMER INTERNATIONAL, Issue 1 2006In Yee Phang Abstract The crystallization and melting behavior of neat nylon-6 (PA6) and multi-walled carbon nanotubes (MWNTs)/PA6 composites prepared by simple melt-compounding was comparatively studied. Differential scanning calorimetry (DSC) results show two crystallization exotherms (TCC, 1 and TCC, 2) for PA6/MWNTs composites instead of a single exotherm (TCC, 1) for the neat matrix. The formation of the higher-temperature exotherm TCC, 2 is closely related to the addition of MWNTs. X-ray diffraction (XRD) results indicate that only the ,-phase crystalline structure is formed upon incorporating MWNTs into PA6 matrix, independently of the cooling rate and annealing conditions. These observations are significantly different from those for PA6 matrix, where the increase in cooling rate or decrease in annealing temperature results in the crystal transformation from ,-phase to ,-phase. The crystallization behavior of PA6/MWNTs composites is also significantly different from those reported in PA6/nanoclay systems, probably due to the difference in nanofiller geometry between one-dimensional MWNTs and two-dimensional nanoclay platelets. The nucleation sites provided by carbon nanotubes seem to be favorable to the formation of thermodynamically stable ,-phase crystals of PA6. The dominant ,-phase crystals in PA6/MWNTs composites may play an important role in the remarkable enhancement of mechanical properties. Copyright © 2005 Society of Chemical Industry [source] | ||||||||||||||||||||||