Consequence Of Annealing Research Articles

Consequences of Annealing on Metal–Insulator–Semiconductor Water Splitting Photoelectrocatalysts

Consequences of Annealing on Metal–Insulator–Semiconductor Water Splitting Photoelectrocatalysts

Comparative study of GaAs nanostructures synthesized in air and distilled water by picosecond pulsed laser ablation and application in hazardous molecules detection

This work explored the fundamental differences/mechanisms between the GaAs substrates ablated in two different media of air and distilled water (DW). A scan area of 5 × 5 mm2 was ablated by a picosecond laser with a pulse duration of 30 ps, a repetition rate of 10 Hz, a wavelength of 1064 nm, and a pulse energy of 2 mJ. The spacing between raster scan lines was varied (0.05–0.35 mm), keeping the scan speed (0.15 mm/s) constant. The obtained GaAs nanostructures (NSs) were thoroughly analyzed using microscopy techniques. A clear increase in separation between the raster scan lines was observed with an increase in the scan spacing for the GaAs NSs fabricated in air, whereas the same result was not observed in DW. Moreover, structures with debris were formed in air irrespective of the spacing, unlike the formation of uniform quasiperiodic GaAs NSs throughout the sample in the case of DW ablation. To the best of our knowledge, there are no reports on the detailed studies involving DW in the fabrication of quasiperiodic NSs of GaAs. Further, these quasiperiodic GaAs NSs formed in DW were coated with a thin layer of gold using the thermal evaporation method, annealed at 400 °C for 1 h in an ambient atmosphere. As a consequence of annealing, Au NPs were uniformly decorated on the quasiperiodic NSs of GaAs imparting plasmonic nature to the whole structures. Subsequently, the Au NPs decorated GaAs NSs were utilized as surface enhanced Raman scattering substrates for the detection of methylene blue (dye molecule) and Thiram (pesticide molecule) at low concentrations.

Unraveling absorptive and refractive optical nonlinearities in CVD grown graphene layers transferred onto a foreign quartz substrate

Absorptive and refractive optical nonlinearities in chemical vapor deposited graphene layers, transferred onto a foreign quartz substrate was studied by performing Z-scan experiment under continuous wave excitation. Open aperture Z-scan results exhibit two shoulder peaks along with a valley at the focal plane and is interpreted in terms of combined effect of saturation absorption (SA) and reverse saturation absorption (RSA). Self-defocusing effect and hence negative nonlinear refraction was observed from the closed aperture Z-scan experiment. Optical nonlinearity is found to decrease upon annealing of graphene layers at 250 °C. Reduction in optical nonlinearity as a consequence of annealing is attributed to the variation of sp2/sp3 fraction and higher crystallite size (decreased structural disorderness) as revealed from the Raman spectroscopy. sp3 carbon atoms support two photon absorption, leading to RSA behavior while sp2 structure displays SA behavior. Our study suggests that annealing paves a way to manipulate sp2/sp3 fraction which can alter the structural disorderness in graphene layers and hence the optical nonlinearities.

Structural and Hydrophilic Characteristics of N-doped TiOx Films Deposited by RF-Magnetron Sputtering

Nitrogen doped titanium oxides (N-doped TiO x ) films were deposited by sputtering the TiO 2 target in N 2 /Ar gas mixture to control the doping amount of nitrogen accurately. In order to modify the resultant films, the samples were annealed in air in a temperature range of 300 ∼ 600 ° C, and then they were irradiated under visible-light (VIS) after being placed in dark. X-ray photoelectron spectroscopy (XPS) spectra show that N-Ti-O ( β -N) and hydroxyl form in the films due to nitrogen doped into TiO x lattice. And the content of hydroxyl increases with annealing temperatures increasing, which leads to the better hydrophilicity. X-ray diffraction (XRD) was used to investigate the crystallinity of the films annealed at different temperatures and the results indicate that the amorphous films transform into crystalline phase as a consequence of annealing. Scanning electron microscopy (SEM) results reveal that the particle size becomes bigger at the higher temperature. Hydrophilicity was tested by contact angle meter. The results show that the water contact angle decreases with raising heat treatment temperature due to the change of particle size and the content of −OH. Hydrophilicity is also influenced by the storing process, and the water contact angles increase with time. Furthermore, the hydrophilicity of N-doped TiO x films increases under visible light (VIS) irradiation.

Orange dye—polyaniline composite based impedance humidity sensors

This study presents the fabrication and investigation of humidity sensors based on orange dye (OD) and polyaniline (PANI) composite films. A blend of 3 wt.% OD with 1 wt.% PANI was prepared in 1 ml water. The composite films were deposited on glass substrates between pre-deposited silver electrodes. The gap between the electrodes was 45 μm. The sensing mechanism was based on the impedance and capacitance variations due to the absorption/desorption of water vapor. It was observed that with the increase in relative humidity (RH) from 30% to 90%, the impedance decreases by 5.2×104 and 8.8×103 times for the frequencies of 120 Hz and 1 kHz, respectively. The impedance—humidity relationship showed a more uniform change compared to the capacitance—humidity relationship in the RH range of 30% to 90%. The consequence of annealing, measuring frequency, response and recovery time, and absorption—desorption behavior of the humidity sensor were also discussed in detail. The annealing resulted in an increase in sensitivity of up to 2.5 times, while the measured response time and recovery time were 34 s and 450 s, respectively. The impedance—humidity relationship was simulated.

Does Thermal Annealing Affect the Mechanical Properties of Silkworm (Bombyx mori) Cocoon Silk?

ABSTRACTIt has been reported [1] that microwave radiation can enhance many of the mechanical properties of Bombyx mori silkworm cocoon silk, as measured in constant strain rate tensile tests to failure and in stress relaxation tests. The consequences of microwave radiation will affect decisions about the use of silk in settings subjected to significant microwave exposure – for example, as a reinforcing fiber in an epoxy matrix composite that may be microwave cured, or as a component in aircraft radomes.There are two possible mechanisms by which microwave radiation may affect a material [2]: (i) the radiation may enable chemical and/or microstructural changes – and therefore property changes – in the same way that conventional heating would, or (ii) the high heating rates that are achievable by microwaving may selectively favor changes that would be masked under conventional conditions, where heating rates are low enough to give preference to changes that have a lower activation energy. Here we explore the former possibility for silk.We characterized several mechanical properties of degummed and subsequently annealed B. mori silk, and compared them to the corresponding properties of degummed B. mori silk that was not annealed. The annealing treatment was carried out at 140 °C for 7 hours (conditions that optimally increased crystal size in an unrelated study of B. mori silk [3]), and then the fibers were allowed to cool gradually to room temperature over the course of an hour. Comparison of mechanical properties revealed no differences between the materials that we tested. Thus, for annealed silk, we do not observe the enhancements that can be achieved by microwaving. We conclude that in cases where microwaving affects the properties of silk, those changes are not a simple consequence of annealing by the microwaves.

Effects of boron addition on mechanical alloying and ordering behaviors of Fe–Al–(B) alloy powders

In this paper, mechanical alloying (MA) of Fe–50Al, Fe–49.5Al–1B, and Fe–47.5Al–5B (at.%) powders and their ordering behavior during annealing were investigated. The results showed that the alloying process was completed after 50 h of milling and disordered Fe–Al–(B) solid solutions were developed. In addition, by increasing the boron content, more considerable crystallite refinement occurred in the course of MA. The ordering behavior of the powders milled for 80 h was evaluated by annealing at various temperatures. The transformation of the disordered solid solutions to ordered Fe–Al–(B) intermetallics was a consequence of annealing. It was also found that the annealing temperature had no meaningful effect on the long-range order parameter. However, by increasing the boron content, the long-range order parameter decreased. It was also notable that the nanoscale structure of the powders was retained even after annealing, suggesting their thermal stability.

Optical characterization of phase changing Ge2Sb2Te5 chalcogenide films

AbstractThe variable angle spectroscopic ellipsometry and spectroscopic reflectometry is used for the optical characterization of the as‐deposited and annealed Ge2Sb2Te5 (GST) films. The dispersion model of the GST films is based on the parameterization of the density of electronic states. As a consequence of annealing, roughness of the upper boundaries of the GST films originates. This annealing also causes the evident redistribution of the density of electronic states from the higher energies to lower energies. The roughening and redistribution of the electrons are explained by means of the phase change of the GST films from amorphous to polycrystalline structure. This phase change is accompanied by changing the conductivity of the films that was proved by introducing the terms of the free carriers in the dispersion model of the GST films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrodeposition and optical characterisation of CdS thin films on ITO-coated glass

Cadmium sulfide thin films have been deposited by electrodeposition using the potentiostatic method on indium tin oxide (ITO)-coated glass substrates from aqueous solution containing CdCl 2 · 2H 2O and Na 2S 2O 3 at 90 °C. The depositions were carried out for various cathodic potentials. Good quality films were obtained at a cathodic potential of −0.6 V. Voltammograms have been recorded to optimize the co-deposition region of CdS on ITO-coated glass substrates at 90 °C. The structural and optical characterisations have been carried out using an X-ray diffractometer and UV—Vis spectrophotometry. Annealing the samples at 350 °C in H 2 for 30 min resulted in increase in intensity as well as a shift towards lower scattering angles due to the lattice parameter increase from enlarged CdS cell. A bandgap narrowing was also observed as a consequence of annealing.

Effect of annealing on the structure and electrical properties of sulfur-doped amorphous c-BN layers

Undoped and sulfur doped amorphous cubic boron nitride (a-cBN) layers were deposited on to silicon substrates by reactive pulse plasma (RPP) method. Subsequently they were annealed at 475, 500 and 700 K for 1 h in pure nitrogen atmosphere. In this study structural and electronic properties of unannealed and annealed layers were investigated. The results show that a consequence of annealing is formation of microstructural stable nanocrystalline cubic boron nitride film as well as substitutional location of introducedin situ donor impurities. This resulted in creation of a-cBN(n-type)-Si(p-type) heterojunction.

Circumferential magnetization processes in CoFeBSi wires

The total impedance, Z, of low magnetostriction wires (Co0.94Fe0.06)72.5B15Si12.5 was measured at 100 kHz under ac currents of various amplitudes, i, for as-cast and current annealed samples. We show that curves Z vs i can represent circumferential permeability curves and that the features observed on these curves as a consequence of annealing can be interpreted due to the induced magnetic anisotropy by the effect of the current annealing.

Microstructural and Vibrational Characterization of the Hydrogenated Amorphous Silicon Powders

Hydrogenated nanophase silicon powders prepared by low pressure and low temperature rf plasma using pure silane gas, have been characterized by transmission electron microscopy (TEM), Fourier transform IR spectroscopy (FTIR) and thermal desorption spectrometry (TDS) of hydrogen. By means of these analysis, the evolution of the hydrogen bonds and the oxidation processes as a consequence of annealing of the silicon powders under vacuum or atmospheric conditions have been investigated. The TDS results reveal the fundamental differences between the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon films, and the FTIR spectra evidence the oxidation process taking place in the silicon powders as a consequence of the annealing. These results along with the TEM analysis show that silicon powder particles present intergrain linkage. We also study the silicon powder particles considering their microstructure and vibrational characteristics as well as their degree of polymerization.

Importance of annealing on the order-disorder phase transition in alkali cyanides

Abstract Contrary to monocrystals powdered KCN displays, after grinding and without annealing, an intermediate monoclinic phase between the high-temperature pseudocubic and the low-temperature orthorhombic phases. The consequence of annealing is the total disappearance of this intermediate phase. A further effect of the annealing process is the reduction of the cubic distortion at the transition. In this paper, we analyse this effect on the intermediate rhombohedral phase observed in the (KCN) x (KBr)1−x mixed system.

Transport properties of phases belonging to the PbF 2TaF 5 system

The transport properties of the disordered fluorite-type solid solution Pb 1− x Ta x F 2+3 x (0≤ x ≤ 0.14) and of the ordered Pb 3TaF 11 phase ( x = 0.25) have been determined. For x = 0.14 the conductivity is shown to decrease when with diminishing disorder as a consequence of annealing. The disordered Pb 0.86Ta 0.14F 2.42 phase is an exceptionally good anionic conductor.

The effect of annealing on structural defects in bulk InP

It has previously been shown that large rectangular prismatic dislocation loops are sometimes present in LEC-grown InP. The present study shows how these defects are affected by annealing. Material containing these loops (both nominally undoped and Fe-doped) has therefore been annealed at 760°C for 15 min both with and without a silicon dioxide capping layer. The defects were then examined by chemical etching and transmission electron microscopy which revealed that substantial rearrangement had occurred even for defects lying 125 μm beneath the surface. A further consequence of annealing was the creation of a high density of microdefects which were present in all annealed samples but were confined to the surface.

Etude des proprietes de conductivite ionique des phases appartenant au systeme PbF 2-InF 3

A detailed study of the transport properties of the disordered fluorite-type solid solution Pb 1-xIn xF 2+x (0 < × < 0.25) and of the ordered fluorite-type related Pb 2InF 7 (x = 0.333) and Pb 7In 5F 29 (x = 0.417) has been carried out. For x = 0.25 the conductivity is shown to decrease when disordering diminishes as a consequence of annealing. The disordered Pb 0.88In 0.12F 2.12 phase is a fairly good anionic conductor.