activation temperature
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Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 334
Author(s):  
Rostislav Velichko ◽  
Yusaku Magari ◽  
Mamoru Furuta

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.


Author(s):  
Chenglin Liu ◽  
Linlin Liang ◽  
Xiuli Han ◽  
Chun Chang ◽  
Junying Chen ◽  
...  

Abstract Furfural residue (FR), a solid waste, was applied as the precursor to prepare activated carbon by steam activation. The Box-Behnken design (BBD) approach-based response surface methodology (RSM) was utilized to optimize the preparation conditions to evaluate their effects on the performance of activated carbon from furfural residue (FRAC). The optimum preparation conditions of FRAC were found as follows: activation temperature of 922 °C, activation time of 62 min, and the mass ratio of char to H2O of 1:4.5, resulting in 1,501.84 mg/g of iodine adsorption capacity and 1,662.41 m2/g of specific surface area. The FRAC was characterized and then the adsorption performance of BPS on FRAC was investigated. Langmuir and Koble-Corrigan isotherm models were well fitted to the experimental data, and the adsorption kinetics process was perfectly described by the pseudo-second-order model. Thermodynamic parameters showed that the adsorption of BPS was a spontaneous exothermic process. Besides, the regeneration efficiency of FRAC was over 97% after five consecutive cycles. The maximum monolayer adsorption capacity of FRAC for BPS was 3.2848 mmol/g at 298 K, indicating that the FRAC was an excellent adsorbent for the removal of BPS from aqueous solutions.


Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1524
Author(s):  
Seul-Yi Lee ◽  
Ji-Hye Park ◽  
Young-Jung Heo ◽  
Eun-Sang Lee ◽  
Soo-Jin Park

Significant efforts have been directed toward the identification of carbonaceous materials that can be utilized for hydrogen uptake in order to develop on-board automotive systems with a gravimetric capacity of 5.5 wt.%, thus meeting the U.S. Department of Energy technical targets. However, the capacity of hydrogen storage is limited by the weak interaction between hydrogen molecules and the carbon surface. Cigarette butts, which are the most abundant form of primary plastic waste, remain an intractable environmental pollution problem. To transform this source of waste into a valuable adsorbent for hydrogen uptake, we prepared several forms of oxygen-rich cigarette butt-derived porous carbon (CGB-AC, with the activation temperature range of 600 and 900 °C). Our experimental investigation revealed that the specific surface area increased from 600 to 700 °C and then decreased as the temperature rose to 900 °C. In contrast, the oxygen contents gradually decreased with increasing activation temperature. CGB-AC700 had the highest H2 excess uptake () of 8.54 wt.% at 77 K and 20 bar, which was much higher than that of porous carbon reported in the previous studies. We found that the dynamic interaction between the porosity and the oxygen content determined the hydrogen storage capacity. The underlying mechanisms proposed in the present study would be useful in the design of efficient hydrogen storage because they explain the interaction between positive carbonaceous materials and negative hydrogen molecules in quadrupole orbitals.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7458
Author(s):  
Karolina Kiełbasa ◽  
Adrianna Kamińska ◽  
Oliwier Niedoba ◽  
Beata Michalkiewicz

Activated carbons with different textural characteristic were derived by the chemical activation of raw beet molasses with solid KOH, while the activation temperature was changed in the range 650 °C to 800 °C. The adsorption of CO2 on activated carbons was investigated. Langmuir, Freundlich, Sips, Toth, Unilan, Fritz-Schlunder, Radke-Prausnitz, Temkin-Pyzhev, Dubinin-Radushkevich, and Jovanovich equations were selected to fit the experimental data of CO2 adsorption. An error analysis (the sum of the squares of errors, the hybrid fractional error function, the average relative error, the Marquardt’s percent standard deviation, and the sum of the absolute errors) was conducted to examine the effect of using various error standards for the isotherm model parameter calculation. The best fit was observed to the Radke-Prausnitz model.


Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1922
Author(s):  
Aiyuan Ma ◽  
Xuemei Zheng ◽  
Lei Gao ◽  
Kangqiang Li ◽  
Mamdouh Omran ◽  
...  

Given the shortage of zinc resource, the low utilisation efficiency of secondary zinc resource, and the crucial problem that the synchronous dissolution of zinc from different mineral phases, an activation pretreatment method merged with calcium activation and microwave heating approach was proposed to enhance the zinc leaching from complex encapsulated zinc-containing metallurgical residues (ZMR). Results indicated that under the optimal pretreatment conditions, including microwave activation temperature of 400 °C, CaO addition of 25% and activation time of 20 min, the zinc leaching rate reached 91.67%, which was 3.9% higher than that by conventional roasting pretreatment. Meanwhile, microwave heating presents excellent treatment effects, manifested by the zinc leaching rates, all exceeding that of conventional roasting under the same conditions, while the process temperature is decreased by 200 °C. In addition, XRD and SEM-EDS analysis denoted that microwave calcification pretreatment can effectively promote the transformation of the refractory zinc minerals like Zn2SiO4 and ZnFe2O4 into the easily leachable zinc oxides. The distinctive selective heating characteristics of microwave heating strengthened the dissociation of mineral inclusion, and the generated cracks increased the interfacial reaction area and further enhancing the leaching reaction of zinc from ZMR.


2021 ◽  
Author(s):  
Nesrine Abderrahim ◽  
Ibtissem Boumnijel ◽  
Hédi Ben Amor ◽  
Ridha Djellabi

Abstract The scientific community gave a lot attention to prepare adsorbents from different natural agriculture-based materials to be used alternative to commercial activated carbon. However, less studies on the optimization of fabrication parameters to obtain activated carbon with highly surface area and adsorption capacity. Herein, we report the synthesis conditions optimization of adsorbent based on date stone and modified with ZnCl2. To obtain a highly adsorption ability of the materials, three systematic parameters were evaluated such as the activation temperature, activation time and the functionalization ratio by ZnCl2. The optimization study showed that the best factors to fabricate an adsorbent from date stone are 700°C, 120 min and 2.0 (g/g), wherein, the specific surface area was found to be 1036 m2/g. While, the iodine and phenol numbers were 928.5 mg/g and 2.1 mmol/g, respectively. To further understand the effect of synthesis parameters, the raw and the as-synthesized activated carbon were characterized via Fourier transmission infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Batch sorption tests to remove MB from water showed a maximum adsorption capacity of 384.6 mg/g using the prepared activated carbon at pH 6 and room temperature (25±2 °C). It was found also that the kinetic adsorption data obeyed the pseudo-second order and, both external diffusion and intra-particle diffusion control the adsorption. Based on the obtained results, the optimization of synthesis conditions through experimental and mobilization studies may help the transfer of technology in terms of agriculture-based materials valorisation towards the environmental remediation.


2021 ◽  
Author(s):  
R.A. Abdulvaliyev ◽  
◽  
A. Akcil ◽  
◽  
◽  
...  

As a result of separation of a fine fraction of gibbsite-kaolinite low-quality bauxite from the Krasnogorsky deposit, it is possible to increase its silicon module. When bauxite is chemically activated in a solution of sodium bicarbonate, the fine fraction is effectively separated from the large one and the phase composition changes – the calcium silicate phase disappears and the calcite phase is formed. With an increase in the activation temperature, the content of kaolinite and siderite decreases, the content of quartz and hematite increases. Studies have shown that at chemical activation temperatures of 120 oC, lasting more than 120 minutes and 200 oC, lasting more than 40 minutes, a dawsonite phase is formed in bauxite, which compacts the mineral structure. When determining the mode of chemical activation, it is necessary to take into account the negative possibility of the formation of dawsonite.


2021 ◽  
Vol 22 (4) ◽  
pp. 711-716
Author(s):  
V.I. Mandzyuk ◽  
I.F. Mironyuk ◽  
N.Ya. Ivanichok ◽  
B.I. Rachiy

The electrochemical processes in capacitor systems based on porous carbon materials (PCMs) derived from glucose, lactose, and saccharose at activation temperature of 800 and 1000°C are explored using impedance spectroscopy method. An equivalent electric circuit, which allows modeling of the impedance spectra in the frequency range from 10-2 to 105 Hz, is proposed, and a physical interpretation of each element of the electrical circuit is presented. It is set that in capacitor systems on the basis of the explored materials the accumulation of capacitance occurs due to the formation of a double electric layer at the electrode/electrolyte boundary, and Faradaic processes are minimized. The specific capacity of supercapacitors based on PCMs obtained at 800°C is 91-154 F/g due to the developed microporous structure of materials.


2021 ◽  
Vol 18 (4) ◽  
pp. 109-118
Author(s):  
Kalpana Patidar ◽  
Manish Vashishtha ◽  
Sonal Rajoria ◽  
Tarun Kumar Chaturvedi

The present work is focussed on treating dye-laden polluted water by using a mustard straw-based activated carbon prepared using ZnCl2 and H3PO4 activation methods. The activation conditions based on the parameters reported in the literature are taken as follows: 700 °C activation temperature, impregnation ratio 2.0, and heating time 2 h. The textural and surface properties of mustard stalk activated carbon (MSAC) were studied by using SEM, nitrogen adsorption, and FT-IR, whereas its adsorption capacity was obtained using the methylene blue (MB) adsorption method. Activation of ZnCl2 and H3PO4 resulted in a BET surface area of 402 and 496 m2/g, respectively. The average pore diameter of the MSAC was found to be 2.13 and 2.59 nm for ZnCl2 and H3PO4 activation respectively. The Langmuir and Freundlich models were applied to evaluate the equilibrium parameters of MB adsorption. The monolayer adsorption capacity of MSAC by ZnCl2 and H3PO4 for MB removal from the Langmuir model were 122.25 and 213.21 mg/g respectively. Activation with H3PO4 was found to be more effective in modifying the structure of the mustard straw when compared with ZnCl2 and also it resulted in a higher adsorption capacity of MB. The present work highlights that the MSAC produced using H3PO4 activation is a low-cost bio-based adsorbent using abundant agricultural by-product namely mustard straw, and this adsorbent can be used in numerous industrially important applications.


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