Effect Of Annealing Conditions Research Articles

Recrystallization behavior of a co-cast AA3xxx–AA6xxx aluminum alloy laminate — Effect of annealing conditions and cold reduction levels

The annealing behavior of a laminated AA3xxx–AA6xxx alloy system is investigated at temperatures and conditions which represent fine particle presence or dissolution in the AA6xxx (i.e. core) layer, as well as 60 or 80% cold reduction levels. The through-thickness microstructural characteristics of the cold rolled and annealed laminates are analyzed using various methods. It is found that the average grain size of the AA3xxx (i.e. clad) layer is generally finer than that of the core layer and the grains are more equiaxed in that layer for all conditions studied. The annealed microstructure of the core layer is also more strongly affected by the change in the annealing conditions. The dependencies of the average grain size and grain size aspect ratio on the annealing conditions are dictated by the presence, size, distribution and thermal stability of particles. A higher level of cold reduction results in reversing the trend of change in the grain size aspect ratios of both layers with annealing temperature in the range of 380 to 420°C (1h), while it yields characteristics similar to that obtained by 60% reduction when annealing is conducted for 30s at 540°C. These results are explained through the microstructural evolution parameters that are affected by cold rolling and annealing conditions.

The impact of new crystalline lamellae formation during annealing on the properties of polypropylene based films and membranes

Cast films, based on polypropylene (PP), were prepared via melt extrusion and, then, annealed below the melting temperature. The effect of annealing conditions on the properties of the films and the microporous membranes formed by stretching was investigated. It is shown that annealing is an effective method to improve the physical properties of semi-crystalline polymers by promoting chain rearrangement and creating secondary lamellae in the amorphous region. DSC results for annealed samples revealed the appearance of a shoulder endothermic peak and a new peak in the correlation function from the SAXS patterns was observed. The annealed films exhibited double yield points in the tensile deformation curves. A direct linear relationship was found between the strength of the second yield point and the fraction of the lamellae. From mercury porosimetry and SEM images of the membranes larger pore sizes and porosity were observed as the annealing time and temperature increased.

Chemical compatibility and properties of suspension plasma-sprayed SrTiO3-based anodes for intermediate-temperature solid oxide fuel cells

La-doped strontium titanate (LST) is a promising, redox-stable perovskite material for direct hydrocarbon oxidation anodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, nano-sized LST and Sm-doped ceria (SDC) powders are produced by the sol–gel and glycine–nitrate processes, respectively. The chemical compatibility between LST and electrolyte materials is studied. A LST–SDC composite anode is prepared by suspension plasma spraying (SPS). The effects of annealing conditions on the phase structure, microstructure, and chemical stability of the LST–SDC composite anode are investigated. The results indicate that the suspension plasma-sprayed LST–SDC anode has the same phase structure as the original powders. LST exhibits a good chemical compatibility with SDC and Mg/Sr-doped lanthanum gallate (LSGM). The anode has a porosity of ∼40% with a finely porous structure that provides high gas permeability and a long three-phase boundary for the anode reaction. Single cells assembled with the LST–SDC anode, La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte, and La0.8Sr0.2CoO3–SDC cathode show a good performance at 650–800 °C. The annealing reduces the impedances due to the enhancement in the bonding between the particles in the anode and interface of anode and LSGM electrolyte, thus improving the output performance of the cell.

Enhanced Ionic Conductivity of Microwave Processed LiO2-Al2O3-TiO2-P2O5 Glass Ceramics

Glass-ceramics with a NASICON crystal structure are of great interest as solid state electrolytes because of their thermal stability and high room temperature ionic conductivities. It has been shown that the crystallization kinetics can greatly affect the activation energy and ionic conductivity of glass ceramic electrolytes. In this work, the effect of annealing conditions on the crystallization and ionic conductivity of glass ceramics will be presented. LiO2-Al2O3-TiO2-P2O5 (LATP) was prepared by melt quenching methods, and crystallization was induced by both microwave and conventional heating for comparison. Results from broadband impedance spectroscopy analysis combined with microstructural characterization will be discussed and processing avenues for enhanced conductivity via microwave heating will be demonstrated.

Templated Thermal Dewetting Process by Utilizing Nano Plastic Forming Technology

A new nano manufacturing method to fabricate minute metal elements on a quartz substrate is reported in this paper. Such minute metal elements are useful to develop optical metamaterials, which have artificial optical properties that have not existed in nature. Proposed fabrication method in this paper is a kind of templated thermal dewetting, in which the Nano Plastic Forming technique is employed to fabricate templated patterns. Firstly, gold thin film is deposited on a quartz glass substrate by using a spatter coater. Then, an adequate groove pattern is fabricated using specially designed diamond tools. Finally, the substrate is annealed in an electric furnace to induce thermal dewetting. In this experiment, effects of annealing conditions and thickness of gold thin film on morphology of the aggregated gold film are studied. In addition, physical modeling of gold separation by thermal dewetting is studied. Through the experiments, possibility of Nano Plastic Forming technique on fabrication of nano metal element is discussed.

Wrinkling of the metal–polymer bilayer: the effect of periodical distribution of stresses and strains

The viscoelastic wrinkling of aluminium films formed on silicon substrates with polystyrene interlayers (aluminium–polystyrene bilayers) is studied under thermal annealing. Compressive thermal stresses induced by the difference in thermal expansions of the bilayer and the silicon substrate are shown to lead to wrinkling instability of the Al film. The effects of annealing conditions and film thickness on the wrinkling regularities are investigated. The evolution of wrinkles, which has a three-stage character, is found to be controlled by the sign and value of in-plane stresses and those normal to the metal–polymer interface. On increasing temperature and duration of annealing, lateral extension of the aluminum–polystyrene bilayer inhibits wrinkle growth and results in smoothening of the film surface.

Efficient CO2 capture by humidified polymer electrolyte membranes with tunable water state

Polymer electrolyte membranes containing alkali or alkaline-earth metal salts were designed and utilized for CO2 capture. These membranes showed higher CO2 permeability than the un-doped control membrane due to the increase of water content, and CO2/gas selectivity was simultaneously enhanced due to the “salting-out” effect, which was strongly dependent on the content of bound water. More specifically, water content, water state and separation performance of polymer electrolyte membranes were strongly dependent on the salt type: (1) membranes containing alkaline-earth metal salts displayed a higher amount of bound water than those containing alkali cations, because the hydration energy of the alkaline-earth cation is relatively larger than that of the alkali cation; (2) the salts (KCl and CaCl2) that can efficiently interrupt chain packing by metal–polymer complexation facilitated the diffusion of water molecules into the polymer matrix and thus increased the total amount of absorbed water. As a consequence, CaCl2-doped membranes showed the highest CO2 permeability (2030 Barrer) and a high separation factor (108 for CO2/N2 and 31 for CO2/CH4) at 2 bar (gage pressure) and 298 K for fully humidified gas streams. The effects of annealing conditions and feed pressure were also explored to elucidate the relevant separation mechanism of the polymer electrolyte membrane.

Effects of Annealing Conditions on the Dielectric Properties of Solution-Processed Al<SUB>2</SUB>O<SUB>3</SUB> Layers for Indium-Zinc-Tin-Oxide Thin-Film Transistors

In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated.

Enhanced photoluminescence of Eu2+–Mn2+ co-doped chalcohalide glasses by controlled crystallization

Effects of the crystallization treatment on visible photoluminescence properties of the Eu2+–Mn2+ co-doped chalcohalide glass have been studied. A broad yellow emission at 560nm from Mn2+ ions is significantly enhanced by a factor of more than 25 via the controlled crystallization. X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman scattering spectroscopy studies demonstrate the precipitation of Ga2S3 nano-crystals (80–100nm) after the proper heat treatment. The effects of annealing conditions on the crystal size and photoluminescence behaviors are investigated.

Effect of annealing conditions on the physio-chemical properties of spin-coated As_2Se_3 chalcogenide glass films

Thin film selenide glasses have emerged as an important material for integrated photonics due to its high refractive index, mid-IR transparency and high non-linear optical indices. We prepared high-quality As2Se3 glass films using spin coating from ethylenediamine solutions. The physio-chemical properties of the films are characterized as a function of annealing conditions. Compared to bulk glasses, as-deposited films possess a distinctively different network structure due to presence of Se-Se homo-polar bonds and residual solvent. Annealing partially recovers the As-Se3 pyramid structure and brings the film refractive indices close to the bulk value. Optical loss in the films measured at 1550 nm wavelength is 9 dB/cm, which was attributed to N-H bond absorption from residual solvent.

Comparative study: the effect of annealing conditions on the properties of P3HT:PCBM blends

This paper presents a detailed study on the role of various annealing treatments on organic poly(3-hexylthiophene) and [6]-phenyl-C61-butyric acid methyl ester blends under different experimental conditions. A combination of analytical tools is used to study the alteration of the phase separation, structure and photovoltaic properties of the P3HT:PCBM blend during the annealing process. Results showed that the thermal annealing yields PCBM “needle-like” crystals and that prolonged heat treatment leads to extensive phase separation, as demonstrated by the growth in the size and quantity of PCBM crystals. The substrate annealing method demonstrated an optimal morphology by eradicating and suppressing the formation of fullerene clusters across the film, resulting in longer P3HT fibrils with smaller diameter. Improved optical constants, PL quenching and a decrease in the P3HT optical bad-gap were demonstrated for the substrate annealed films due to the limited diffusion of the PCBM molecules. An effective strategy for determining an optimized morphology through substrate annealing treatment is therefore revealed for improved device efficiency.

The effect of annealing conditions on the adhesive properties of TiN coatings

The effect of low-temperature annealing on the adhesion strength and coefficient of friction of TiN coatings deposited on austenitic stainless steel by the vacuum-arc method is studied. The behavior of the coefficient of friction of titanium nitride upon annealing in air is discussed. It is shown that the adhesion strength of TiN coatings does not depend on annealing conditions.

Study of High Temperature Microwave Annealing on the Performance of 4H-SiC MOS Capacitors

The strong covalent bond of SiC imposes harsh post implantation annealing condition requirement for SiC MOS devices. As a consequence the effect of the annealing conditions on the channel region of the MOS devices becomes critical. High temperature microwave annealing has been shown to be an attractive alternative to conventional thermal annealing techniques. The effect of high temperature rapid microwave annealing on the performance of 4H-SiC MOS capacitors has been studied in this paper. Annealing temperatures ranging from 1600°C up to 2000°C for 30secs is used and the effect of annealing conditions is studied via C-V measurements on MOS capacitors.

Effect of annealing conditions on structural and magnetic properties of laser ablated copper ferrite thin films

The effect of annealing conditions on structural and magnetic properties of copper ferrite thin films on (100) Si substrates was examined in detail. After deposition, the ferrite thin films were post-annealed in vacuum and in oxygen atmosphere for several hours. It is found that the crystal structure of CuFe2O4 thin films changed drastically depending on different heating process. A maximum magnetization was achieved in the film that was vacuum annealed and it decreased remarkably after oxygen annealing.

Comparative studies on thermal and laser sintering for highly conductive Cu films printable on plastic substrate

Compound-based Cu paste was synthesized to prepare electrically conductive films on plastic substrate. The Cu pastes screen-printed onto polyimide were annealed inside a furnace and also by an ultraviolet laser beam and the effects of annealing conditions on the microstructures and electrical properties were investigated. Both of thermal and laser processes were carried out under N2 gas flow, which was very effective in preventing oxidation. The minimum resistivity available with thermal sintering was 1.30×10−5Ωcm and a slightly higher resistivity was obtained by laser sintering. This value is several orders of magnitude lower than that reported for the copper nanoparticle paste thermally sintered under N2 atmosphere. The variation of microstructure and electrical property with the laser power was very similar to the temperature dependence of these factors in thermal sintering.

The effect of processing conditions on the structural morphology and physical properties of ZnO and CdS thin films produced via sol–gel synthesis and chemical bath deposition techniques

Cadmium sulfide (CdS) and zinc oxide (ZnO) are used in thin film solar cells as buffer layer and transparent conducting oxide, respectively. The effect of annealing conditions on the morphology and physical properties of CdS and ZnO films prepared using chemical bath deposition and sol–gel synthesis techniques, respectively, was investigated. CdS films obtained from the chemical bath deposition (CBD) process were found to be polycrystalline with dense granular morphology. Electrical characterization of the films annealed at 400 °C for 10 min yielded values of 2.2×10−3 Ω cm and 8.3×1012 cm −3 for resistivity and carrier concentration, respectively. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) studies of intrinsic zinc oxide (i-ZnO) films revealed flake-like morphology and transformation of the as-deposited amorphous structure into a hexagonal wurtzite crystal structure upon annealing at 500 °C for 2 h. Optical and electrical characterization results showed that such films had ∼80% transmittance and resistivity values as low as 6.4×102 Ω cm. These films are being explored for fabrication and testing of copper-indium-gallium-(di)selenide (CIGS) thin film solar cells obtained from simple, cost-effective, solution-based synthesis routes.

Effects of annealing conditions and thickness ratio of Si/Al films on the Hall carrier mobility, Al carrier concentration, and nanovoids formed in the metal-induced Si crystallization of Si/Al/Si/SiO2/glass specimens

In the present study, a-Si/μc-Al/a-Si/SiO2/glass specimens were prepared with various combinations of thicknesses of the μc-Al layer and the two a-Si layers. The effects of μc-Al film thickness, a-Si film thickness, the thickness ratio of Al film to Si films, and the annealing temperature on the metal-induced Si crystallization and void defects formed in the sandwich composite specimens were investigated. A transmission electron microscope (TEM) and an X-ray photoelectron spectroscope (XPS) were used to investigate the diffusion mechanism and efficiency of Si crystallization. When the annealing temperature was sufficiently high, the μc-Al grains diffused into the two adjacent Si layers with a fairly even distribution over the entire sandwich structure. Si crystallization was thus significantly enhanced by the sandwich structure. The Hall carrier mobility of the specimen with a structure of a-Si(500nm)/μc-Al(50nm)/a-Si(500nm) was 80.1cm2/Vs and the Al carrier concentration was 1.5×1018/cm3 at an annealing temperature of 600°C; no voids were found in the sandwich structure. An increase in the top layer (a-Si) thickness is advantageous for Si crystallization; however, an increase in the third layer (a-Si) thickness degrades Si crystallization. For a given Al film thickness, an excessive increase in the thicknesses of the two a-Si layers degrades Si crystallization even at high annealing temperatures. A thick Al film in combination with two thick a-Si layers leads to a high Hall carrier mobility when the annealing temperature is sufficiently high. An increase in the Si/Al thickness ratio increases the Hall carrier mobility and decreases the Al carrier concentration.

The effect of annealing conditions on the intercalation and exfoliation of layered silicates in polymer nanocomposites

Layered silicate nanocomposites based on polyamide 6 and polypropylene have been prepared via static annealing experiments. The evolution of clay dispersion into the polymer matrices was monitored by wide angle X-ray diffraction analysis and transmission electron microscopy. The results have evidenced that the polymer diffusion inside the organoclay galleries is spontaneous and have elucidated the mechanism of nanostructured system formation under static conditions. Indeed, the exfoliation mechanism turned to be a two-step process consisting of polymer intercalation into the clay galleries and progressive layer delamination. Both steps have turned out to depend on thermodynamic and kinetic parameters. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010

Effects of annealing conditions on the properties of TiO 2/ITO-based photoanode and the photovoltaic performance of dye-sensitized solar cells

Photovoltaic performance of dye-sensitized solar cell (DSSC) is enhanced by a two-step annealing process of the photoanode. The 1st-step of annealing is performed in oxygen at 450 °C for 30 min which effectively removes the residual organics originated from the TiO 2 precursor pastes. This enhances the dye adsorption on the TiO 2 nanoparticles and raises the short-circuit current density ( J SC). The 2nd-step of annealing is performed in nitrogen at 450 °C for 10 min which removes extra oxygen atoms resulted from the incorporation of oxygen atoms into the tin-doped indium oxide (ITO) film during the 1st-step of annealing. This reduces the sheet resistance of ITO and thereby enhances the fill factor (FF). With the enhanced J SC of 15.9mAcm −2 and FF of 0.65, the AM1.5 solar to electric conversion efficiency ( η) of DSSC reaches 6.7% which is better than that based on the conventional one-step air annealing ( η = 5.53%, J SC = 14.08 mA cm −2, FF = 0.6).

Effects of annealing conditions on the photoelectrochemical properties of dye-sensitized solar cells made with ZnO nanoparticles

Dye-sensitized solar cells (DSSCs) were fabricated by using porous ZnO electrodes derived from home-made ZnO nanoparticles. Electrochemical impedance spectra and open-circuit photovoltage decay curves measurements were performed to investigate the photoelectrochemical characteristics of ZnO films annealed at different temperatures. The experimental results indicate that the effects of the bulk traps and the surface states within the ZnO films on the recombination processes of the photoinjected electrons in DSSCs depend on the annealing temperature. The DSSC based on the ZnO electrode annealed at 400 °C exhibits an optimal energy conversion efficiency of 3.92% under the illumination of one sun simulated sunlight because the farthest decrease in the effects of both bulk traps and surface states at this film can maintain a lower charge recombination probability. This result indicates that the ZnO film electrode has promising application in the field of DSSCs, and the optimization of porous film fabrication condition is efficient for the improvement of ZnO-based DSSC’s performances.