Effect Of Thermal Annealing Temperature Research Articles

Effect of thermal annealing on kaolin from the Amazon region, aiming at the production of geopolymer

In the focus of environmental problems and climate change, research for alternative materials becomes essential. In this sense, research on geopolymers is very relevant, due to its sustainability characteristics linked to mechanical and physical properties. Metakaolin is a geopolymer precursor and obtained from kaolin, whose characteristics, which are specific to each region, impact on the characteristics of metakaolinite, which in turn influences the production of geopolymer. Characteristics of metakaolin from the Amazon region are not well known, with few publications, despite the importance of the region in the international context in terms of natural resources and environmental. In order to contribute to this research, the present investigation analyses the effect of thermal annealing temperature on kaolin and verifies the suitability of metakaolin as a precursor of geopolymer products. The kaolin in natura was benefited by wet sieving and thermally treated in the range 600 °C to 800 °C. Samples were characterized by XRD, with phases quantification and amorphous fraction obtained by Rietveld method, XRF, TG/DTG, specific surface area, laser granulometry, FTIR, SEM and EDS. An average specific surface area of 1.32 m2/g was identified for kaolin treated at 700 °C, where the amorphous fraction is 91.6% which has almost reached saturation, varying slightly to 800 °C as thermal annealing temperature. Considering environmental aspects and the energy savings, one may state that samples treated at 700 °C may efficiently be used as geopolymer precursor material. The vibration of the O–H bond in kaolinite treated at temperatures greater than 650 °C was not identified. Results suggest that the metakaolinite obtained from Amazon kaolin is indicated for geopolymer production.

The effect of Cu doping on structural, optical properties and photocatalytic activity of Co3O4 nanoparticles synthesized by sonochemical method

This research article describes pure and different concentrations (2%, 4%, 6%, 10%) of Cu-doped Co3O4 nanoparticles synthesized by sonochemical method and subsequent calcination at high temperature. The synthesized nanoparticles were further characterized using X-ray diffraction, UV–vis spectroscopy, FT-IR spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The analysis results showed that nanoparticle size, band gap and photocatalytic activity of CuxCo3-xO4 compounds can be tuned by changing the Cu doping content. The XRD study reveals no impurity peaks associated with copper or copper oxide phases in the diffractograms of doped samples. The highest degradation of methylene blue dye under visible light was observed in the presence of 2% Cu-doped Co3O4 nanoparticles annealed at 500 °C and found to be 87.51% after 330 min. In addition, the effect of thermal annealing temperature on structural and optical properties of undoped and different concentrations of Cu-doped Co3O4 nanoparticles was investigated in detail.

Study of the Effects of Thermal Annealing Temperature to Electrochemical Cycling of Mg2+ and Structure of Spinel MgV2O4 Crystals

Spinel vanadium oxides are a promising candidate material for multivalent battery cathodes due to the various possible valence states of V within the spinel framework, which allows for pathways in Mg2+ ion deintercalation [1]. In recent work, Hu et al. experimentally demonstrated that spinel vanadium oxides nanocrystals have a high capacity for Mg2+ electrochemical cycling [2]. While they reported capacities above 200mAh/g at 110 °C, thus outperforming counterparts such as Cr and Mn oxide spinels, it was noted that these capacities are limited by complex defect structures, as suggested by peak pair distances that cannot be explained in the spinel framework in X-ray diffraction measurements.Here, we will utilize atomic-resolution scanning transmission electron microscopy to characterize the structural defects in spinel V2O4 nanocrystals and their possible effect on Mg2+ intercalation. Additionally, we will report the effects of thermal annealing on the structure as a function of temperature and explore the stability of the MgV2O4 nanocrystals. We find that the effects of electron beam exposure can be used as a proxy for damage incurred on the crystals during electrochemical cycling, on the structure of the crystals. The atomic-resolution characterization will be conducted with an aberration-corrected cold field emission JEOL ARM200CF operated at 200kV primary electron energy and emission current of 15μA. The electron probe will be operated at 24mrad convergence semi-angle. High angle annular dark field, low angle annular dark field and annular bright field detectors will be set to the following inner angles: 75 mrad, 30 mrad, 11mrad. X-ray energy dispersive spectroscopy measurements will be conducted using a large solid-angle Oxford XMAX100TLE detector. Additionally, the ARM200CF is equipped with a post-column Gatan Continuum GIF spectrometer providing capabilities for electron energy loss spectroscopy measurements.In this contribution, we will demonstrate that thermal annealing at higher temperatures increases the crystal size of the MgV2O4 crystals while simultaneously decreasing the presence of defect structures. Additionally, we will characterize a variety of defect structures, similar to those shown in Figure 1, present in crystals annealed at lower temperatures using atomic resolved images and electron spectroscopy techniques. [3]Figure 1. LAADF Image showing a grain boundary defect in a spinel MgV2O4 nanocrystal thermally anneal at 400 degrees Celsius.[1] Computer Modeling Investigation of MgV2O4 for Mg-ion Batteries. Navaratnarajah Kuganathan, Konstantinos Davazolglou, Alexander Chroneos; Journal of Applied Physics 2020 127, 035106.[2] High Capacity for Mg2+ Deintercalation in Spinel Vanadium Oxide Nanocrystals. Linhua Hu, Jacob R. Jokisaari, Bob Jin Kwon, Liang Yin, Soojeong Kim, Haesun Park, Saul H. Lapidus, Robert F. Klie, Baris Key,Peter Zapol, Brian J. Ingram, John T. Vaughey, and Jordi Cabana; ACS Energy Letters 2020 5 (8), 2721-2727.[3] This work is solely supported by the Joint Center for Energy Storage Research (JCESR) and Energy Innovation Hub funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences. Figure 1

热褪火温度对ZnO纳米棒阵列/活性炭纤维复合材料催化性能的影响

热褪火温度对ZnO纳米棒阵列/活性炭纤维复合材料催化性能的影响

Structural, linear and non-linear optical properties of annealed As47.5Se47.5Ag5 thin films for optoelectronic applications

The effect of thermal annealing temperature on both structural and optical properties of amorphous As47.5Se47.5Ag5 thin films was studied. The XRD studies showed that the crystallinity of the studied films is improved by increasing the annealing temperature. Furthermore, the crystallite size increase whereas dislocation density and strain decrease with increasing the annealing temperature. The optical constants of the as-prepared and annealed As47.5Se47.5Ag5 thin films were calculated using the envelope method. The optical absorption data of these films was successfully described by Tauc's relation. The optical absorption mechanism was found to follow the allowed direct and indirect transitions. In addition, it was found that the optical band gap decreases while band width Ee increases as the annealing temperature increases. The data of the refractive index n was analyzed and discussed in terms of the single oscillator model proposed by Wemple-DiDomenico. Besides that, the non-linear optical parameters χ(1), χ(3) and n2 were determined as a function of the annealing temperature.

ZnO QDs Deposited on Si by Sol-Gel Method: Role of Annealing Temperature on Structural and Optical Properties

Zinc acetate, propanol, and ethanolamine are used to synthesize ZnO quantum dots (QDs) via the sol–gel method. Spin coating at 220°C is then employed to prepare ZnO thin films consist of QDs. The effects of thermal annealing temperature on the structural and optical properties of the samples are investigated. The prepared QDs are characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy (PL). XRD patterns reveal the crystalline nature of samples existing in the hexagonal wurtzite phase. Increasing annealing temperatures bring about changes to the crystal orientation through the c-axis and increase the size of the QDs from ~10 nm to ~22 nm; this increment can be explained by a coarsening mechanism and the Ostwald ripening process. The observed broadening of X-ray peaks confirms the evolution of crystalline phases in the ZnO QDs. Quantitative analysis of size-dependent strain effects is performed through the Williamson-Hall model. The QD mean size estimated from FESEM and XRD displays high consistency. Room-temperature PL peaks of 3.37ev are attributed to the radiative recombination of electrons and holes from the ZnO QDs/Si interface.

Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases.

A one-step electrochemical method based on sacrificial anode electrolysis (SAE) was used to deposit stabilized gold nanoparticles (Au NPs) directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C) on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO) was investigated. Transmission and scanning electron microscopy (TEM and SEM), as well as X-ray photoelectron spectroscopy (XPS), revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

Effect of Thermal Annealing Temperatures on MSM Photo Detector Based on Ge-like Micro Flowers in the Dark Mode

In this research , a current density of J = 7.5 mA/cm2 was applied over a constant duration of 2 h to grow Ge-like microflowers on Si. To fabricate a photodetector, Pd was deposited by RF-sputtering as metal contact with Ge. The samples were subjected to rapid thermal annealing (RTA) in ambient N2 at 100,200° and 300°C for 10 min. By screening the samples from electrical noise, the electrical characteristics through current-voltage measurements were carried out at room temperature before and after annealing. The measurements were performed in the dark, white light and UV illuminations. The forward I-V characteristics were analyzed using standard thermionic emission relation for electron transport from Metal-semiconductor-metal(MSM)with low doping concentration .The saturation current was obtained as the intercept from the straight line of ln I versus V, T. It was found that at 5V, these currents were 2.45 × 10-5, 5.77× 10-5, 6.12× 10-4 A, respectively. Also characteristics of the MSM photodetector, linear and logarithmic forward and reverse bias, at different annealing temperatures: as-deposited, 100°C, 200°C and 300°C in the dark mode.

Effect of Thermal Annealing Temperatures on MSM Photo Detector Based on Ge-like Micro Flowers in the Dark Mode

In this research , a current density of J = 7.5 mA/cm2 was applied over a constant duration of 2 h to grow Ge-like microflowers on Si. To fabricate a photodetector, Pd was deposited by RF-sputtering as metal contact with Ge. The samples were subjected to rapid thermal annealing (RTA) in ambient N2 at 100,200° and 300°C for 10 min. By screening the samples from electrical noise, the electrical characteristics through current-voltage measurements were carried out at room temperature before and after annealing. The measurements were performed in the dark, white light and UV illuminations. The forward I-V characteristics were analyzed using standard thermionic emission relation for electron transport from Metal-semiconductor-metal(MSM)with low doping concentration .The saturation current was obtained as the intercept from the straight line of ln I versus V, T. It was found that at 5V, these currents were 2.45 × 10-5, 5.77× 10-5, 6.12× 10-4 A, respectively. Also characteristics of the MSM photodetector, linear and logarithmic forward and reverse bias, at different annealing temperatures: as-deposited, 100°C, 200°C and 300°C in the dark mode.

Ferromagnetic mechanism for Zn0.98Ni0.02O nanoparticles

Zn0.98Ni0.02O nanoparticles have been synthesized successfully by the sol–gel method. Effects of thermal annealing temperature (400, 500 and 600°C) and atmosphere (argon and air) on the structural, magnetic and optical properties of the samples were investigated. Results indicated that Ni ions were successfully incorporated into the ZnO matrix and replaced Zn ions. By varying temperature and atmosphere of the thermal annealing treatment, we found that Zn0.98Ni0.02O nanoparticles exhibited ferromagnetism at room temperature and this behavior was believed to be from oxygen vacancies.

Non-toxic selenization using thermal annealing for CuGa/In bi-layer precursors deposited by sputtering

Cu(InxGa1−x)Se2 (CIGS) thin films were produced using a two-step sputtering process consisting of precursor formation and selenization. In the first stage, we prepared Cu0.75Ga0.25/In bi-layer precursors by direct current sputtering on Mo/soda-lime glass substrates. In the second stage, the stacked precursors were selenized using non-toxic Se pellets in a graphite box in which the temperature was controlled at 475–680 °C during rapid thermal annealing. We investigated the effect of thermal annealing temperature on Ga distribution and the crystallinity of the Cu(InxGa1−x)Se2 films. Thermal annealing significantly affected the distribution of Ga atoms. At low temperatures, segregation of Ga atoms into the CIGS/Mo interface and an absence of Ga content on the surface were observed. In addition, a phase-separated CuInSe2/CuGaSe2 structure and incomplete selenization phases were observed. At high temperatures, CIGS films were formed with the proper distribution of Ga content.

Luminescence Properties of Europium Ions-Doped Yttrium Silicate (Y2SiO5:Eu3+) Nanocrystalline Phosphors: Effect of Eu3+ Ion Concentration and Thermal Annealing

The trivalent europium ions-doped yttrium silicate (Y2SiO5:Eu3+) nanocrystalline phosphors were synthesized via a sol-gel method, followed by post thermal annealing. The effects of thermal annealing temperature and doping concentration on the structural and luminescent properties of Y2SiO5:Eu3+ nanocrystalline phosphors were systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence measurements. The nanocrystalline phosphors with a high crystallinity were obtained at an annealing temperature of 1300 degrees C. The luminescent spectra were affected strongly by the Eu3+ ion concentration and annealing temperature. The Eu3+ ion concentration was optimized at 5 mol%, exhibiting excellent red emission (-612 nm) corresponding to the 5D0 --> 7F2 transition of Eu3+ ions at the excitation wavelengths of 262 and 396 nm. For the optimized Y2SiO5:Eu3+ nanocrystalline phosphors, the lifetimes were also estimated from the decay curves under the ultraviolet excitations.

Evaluation of the effects of thermal annealing temperature and high-k dielectrics on amorphous InGaZnO thin films by using pseudo-MOS transistors

The effects of annealing temperatures and high-k gate dielectric materials on the amorphous In-Ga-Zn-O thin-film transistors (a-IGZO TFTs) were investigated using pseudo-metal-oxide-semiconductor transistors (Ψ-MOSFETs), a method without conventional source/drain (S/D) layer deposition. Annealing of the a-IGZO film was carried out at 150–900 °C in a N2 ambient for 30 min. As the annealing temperature was increased, the electrical characteristics of Ψ-MOSFETs on a-IGZO were drastically improved. However, when the annealing temperature exceeded 700 °C, a deterioration of the MOS parameters was observed, including a shift of the threshold voltage (Vth) in a negative direction, an increase in the subthreshold slope (SS) and hysteresis, a decrease in the field effect mobility (µFE), an increase in the trap density (Nt), and a decrease in the on/off ratio. Meanwhile, the high-k gate dielectrics enhanced the performance of a-IGZO Ψ-MOSFETs. The ZrO2 gate dielectrics particularly exhibited excellent characteristics in terms of SS (128 mV/dec), µFE (10.2 cm−2/V·s), Nt (1.1 × 1012 cm−2), and on/off ratio (5.3 × 106). Accordingly, the Ψ-MOSFET structure is a useful method for rapid evaluation of the effects of the process and the material on a-IGZO TFTs without a conventional S/D layer deposition.

Solution-processed organic UV photodetectors based on polyfluorene and naphthalene diimide

Organic ultraviolet (UV) photodetectors with bulk-heterojunction structure were fabricated via a simple spin-coating method by using blend films of poly(9,9-dihexylfluorene) (PFH) and a soluble naphthalene diimide derivative, N,N′-Bis(phenylmethyl)naphthalene-1,4,5,8-tetracarboxylic diimide (NDI-BA), which respectively act as the donor and acceptor. The effect of thermal annealing temperature together with the components blend ratio on the morphology of the composite films, and further the performance of the devices was investigated. The results indicate that balanced charge transfer and transportation can be achieved by controlling the extent of phase separation. By optimization, the device with the 1:1 (by weight) blend layer annealed at 80 °C for 15 min demonstrates obvious photoresponse under UV radiation. A photo-to-dark current ratio of over two orders of magnitude, fast response with decay time (decay to 1% of the value before removing of the radiation) of less than 200 ms, and a responsivity of 224 mA/W at −4 V can be obtained under 1 mW/cm 2 UV radiation at 365 nm. The spectral response covering the region from 300 to 420 nm endows the device potential application in near-UV region as low-cost optical switches or photodetectors.

The effects of annealing temperature on structural and optical properties of S-doped ZnO nanobelts

In this study, the effects of thermal annealing temperature on the structural and optical properties of S-doped ZnO nanobelts were investigated. The XRD pattern shows that the crystallinity of S-doped ZnO nanobelts improves with increased annealing temperature. Room temperature photoluminescence spectroscopy of the as-grown S-doped ZnO nanobelts shows no detectable ultraviolet peak with the broad peaks in the visible emission region at 480, 505, and 518 nm. A weak peak in the ultraviolet region at 383 nm appears after annealing at 400 and 600 °C. Raman spectroscopy of the sample also shows a significant change with an increase in the annealing temperature.

Effects of annealing temperature on amorphous GaN films formed on Si(1 1 1) by pulsed laser deposition

GaN thin films were grown on Si(1 1 1) substrates using a pulsed KrF excimer laser-deposition system, and post-annealing was examined to improve the films' quality. In order to investigate the effect of thermal annealing temperature on the crystalline quality, optical properties and surface morphology of the samples, after deposition, the samples were subsequently annealed at different temperatures in ammonia (NH3) ambience for 15 min. The annealed films were characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), Raman spectra and photoluminescence spectra. The measured results show that annealing temperature plays an important role in improving the quality of GaN films, polycrystalline wurtzite structure GaN thin films with c-axis preferred orientation were successfully obtained by annealing, and the optimum annealing temperature is 1100 °C.

Effects of thermal annealing temperature and duration on hydrothermally grown ZnO nanorod arrays

In this study, the effects of thermal annealing temperature and duration on ZnO nanorod arrays fabricated by hydrothermal method were investigated. The annealed ZnO/Si(1 1 1) substrate was used for ZnO nanorod array growth. The effects of annealing treatment on the structural and optical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature photoluminescence measurements. With the annealing temperature of 750 °C and the annealing duration of 10 min, both the structural and optical properties of the ZnO nanorod arrays improved significantly, as indicated in the X-ray diffraction and photoluminescence measurement.

Effect of annealing temperature on electrical and structural properties of transparent indium tin oxide electrode to n-type GaN

The effects of thermal annealing temperature on electrical, structural and surface morphology characteristics of transparent indium tin oxide (ITO) electrode to n-type gallium nitride (GaN) have been investigated. The Schottky barrier height of as-deposited ITO/n-GaN is found to be 0.61 eV ( I– V) 0.64 eV ( C– V). The extracted barrier heights of ITO/n-GaN annealed contacts are 0.67 eV ( I– V) 0.71 eV ( C–V) at 200 °C, 0.70 eV ( I–V) 0.75 eV ( C–V) at 300 °C, and 0.72 eV ( I–V) 0.78 eV ( C–V) at 400 °C, respectively. Annealing at 500 °C for 1 min in the nitrogen ambient, increases the barrier height and the corresponding values are 0.74 eV ( I–V) 0.83 eV ( C–V). The Norde method was also used to extract the barrier height of ITO/n-GaN Schottky contacts. From the above observations, it is clear that the electrical properties of annealed ITO contacts are improved compared to the as-deposited films. Based on the Auger electron spectroscopy and X-ray diffraction results, the formation of gallide phases at the ITO/n-GaN interface could be the reason for the improvement of electrical properties upon annealing at various temperatures. The measured transmittance of ITO films between 380 nm and 450 nm is above 90% for a sample annealed at 500 °C. Atomic force microscopy results showed that the surface morphology of a contact annealed at 500 °C is fairly smooth with a RMS roughness of 2.37 nm.

Annealing temperature effect of hole-collecting polymeric nanolayer in polymer solar cells

Recent pronounced global warming has attracted keen interest in solar cells due to their renewable feature exploiting tremendous solar energy (89 PW) during sun’s lifetime of ~5 billion years. Of the solar cells invented so far, inorganic solar cells are now in market but they have a demerit such as high fabrication cost and hard characteristics of inorganic materials which restrict the spreading of solar cells. In this regard organic solar cells have been studied as a contingency because of their potential for cheaper manufacturing cost and variety of applications owing to flexible and semitransparent features. To date, the most widely used polymer as a light-absorbing material is regioregular poly(3-hexylthiophene) (P3HT) which does also act as an electron-donating (i.e., holeaccepting) component in a bulk heterojunction layer inside corresponding solar cell geometry. Here we note that the bulk heterojunction film is, broadly speaking, a mixture of electron-donating and electron-accepting materials, whilst in more specific terms it has integrated and randomly distributed p-n junctions in the bulk polymeric film. As an electron-accepting material, soluble fullerenes such as 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) are widely used. Considering the principle of electron flows in the bulk heterojunction polymer solar cells, it is not necessary to insert a low work function metal in between the bulk heterojunction layer and the electron-collecting electrode, which has been proven in our previous report. However, the direct hole collection from the bulk heterojunction layer to transparent conducting oxide, mostly indium tin-oxide (ITO), was not efficient owing to the insufficient interfacial contact between the bulk heterojunction layer and the ITO surface. Hence most of efficient organic solar cells employ a buffer layer, in most cases poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), between the bulk heterojunction layer and the ITO layer. However, the influence of thickness and thermal annealing conditions of PEDOT:PSS layer was not much studied. In this work, we have briefly investigated the effect of thermal annealing temperature on the performance of polymer solar cells with the PEDOT:PSS nanolayer of which thickness is 20 nm. The result showed that about 40% power conversion efficiency was improved by thermal annealing of the PEDOT:PSS layer at 120 C.

Thermal Stability of Nitrogen Expanded Austenite Formed by Plasma Nitriding on AISI304 Austenitic Stainless Steels

The effect of thermal annealing temperature on the microstructure and phase composition of nitrided layer formed on AISI 304 stainless steel by plasma nitriding were investigated. The phase composition and structure of the nitrided have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis of nitrided samples at 420oC showed the presence of γN phase in the nitrided layer. The temperature at which the nitrogen expanded austenite started to decompose was about 450oC. Above this critical temperature the γN phase transformed into a mixture of CrN and α-phase. The surface hardness of nitrided layer also slightly changed with annealing temperature.