共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Gañán J.F. González C.M. González-García A. Ramiro E. Sabio S. Román 《Applied Surface Science》2006,252(17):5993-5998
Activated carbons were prepared from almond tree pruning by non-catalytic and catalytic gasification with carbon dioxide and their surface characteristics were investigated. In both series a two-stage activation procedure (pyrolysis at 800 °C in nitrogen atmosphere, followed by carbon dioxide activation) was used for the production of activated samples. In non-catalytic gasification, the effect of the temperature (650-800 °C for 1 h) and the reaction time (1-12 h at 650 °C) on the surface characteristics of the prepared samples was investigated. Carbons were characterized by means of nitrogen adsorption isotherms at 77 K. The textural parameters of the carbons present a linear relation with the conversion degree until a value of approximately 40%, when they come independent from both parameters studied. The highest surface area obtained for this series was 840 m2 g−1. In the catalytic gasification the effect of the addition of one catalyst (K and Co) and the gasification time (2-4 h) on the surface and porosity development of the carbons was also studied. At the same conditions, Co leads to higher conversion values than K but this last gives a better porosity development. 相似文献
2.
S. Román J.F. González J. Gañán E. Sabio C.M. González-García A. Ramiro V. Mangut 《Applied Surface Science》2006,252(17):6036-6041
Activated carbons were prepared by air and carbon dioxide activation, from almond tree pruning, with the aim of obtaining carbons that reproduce the textural and mechanical properties of the carbons currently used in the filtering system of the condenser vacuum installation of a Thermonuclear Plant (CNA; Central Nuclear de Almaraz in Caceres, Spain), produced from coconut shell. The variables studied in non-catalytic gasification series with air were the temperature (215-270 °C) and the time (1-16 h) and the influence of the addition of one catalyst (Co) and the time (1-2 h) in catalytic gasification. In the case of activation with CO2, the influence of the temperature (700-950 °C) and the time (1-8 h) was studied. The resulting carbons were characterized in terms of their BET surface, porosity, and pore size distribution. The N2 adsorption isotherms at 77 K for both series showed a type I behaviour, typical of microporous materials. The isotherms showed that with both gasificant agents the temperature rise produced an increase in the carbon porosity. With regards to the activation time, a positive effect on the N2 adsorbed volume on the carbons was observed. The best carbons of each series, as well as the CNA (carbon currently used in the CNA), were characterized by mercury porosimetry and iodine solution adsorption isotherms. The results obtained allowed to state that several of the carbons produced had characteristics similar to the carbon that is target of reproduction (which has SBET of 741 m2 g−1, Vmi of 0.39 cm3 g−1 and a iodine retention capacity of 429.3 mg g−1): carbon C (gasification with CO2 at 850 °C during 1 h), with SBET of 523 m2 g−1, Vmi of 0.33 cm3 g−1 and a iodine retention capacity of 402.5 mg g−1, and carbon D (gasification with CO2 at 900 °C during 1 h), whose SBET is 672 m2 g−1, Vmi is 0.28 cm3 g−1 and has a iodine retention capacity of 345.2 mg g−1. 相似文献
3.
M. Olivares-Marín C. Fernández-González V. Gómez-Serrano 《Applied Surface Science》2006,252(17):5980-5983
Using cherry stones, the preparation of activated carbon has been undertaken in the present study by chemical activation with potassium hydroxide. A series of KOH-activated products was prepared by varying the carbonisation temperature in the 400-900 °C range. Such products were characterised texturally by gas adsorption (N2, −196 °C), mercury porosimetry, and helium and mercury density measurements. FT-IR spectroscopy was also applied. The carbons prepared as a rule are microporous and macroporous solids. The degree of development of surface area and porosity increases with increasing carbonisation temperature. For the carbon heated at 900 °C the specific surface area (BET) is 1624 m2 g−1, the micropore volume is 0.67 cm3 g−1, the mesopore volume is 0.28 cm3 g−1, and the macropore volume is 1.84 cm3 g−1. 相似文献
4.
Abdel-Nasser A. El-Hendawy 《Applied Surface Science》2005,252(2):287-295
A number of activated carbons were prepared from a locally available by-product, corncobs, under currently established activation schemes. Obtained carbons were characterized by N2 adsorption at 77 K and the isotherms were analyzed by BET and αs methods. Steam-activation at 900 °C produced a microporous carbon having the highest Sα of 788 m2 g−1, whereas activation with air at 350 °C produced a carbon of Sα = 321 m2/g and possess wider pores. KOH impregnation with char in ratio 1:1 (w/w) and impregnated in the same ratio with the raw material prior to pyrolysis at 700 °C for 1 h, gave CK700, K700 respectively. An additional sample was obtained by oxidizing part of K700 with conc. HNO3. All three KOH carbons show pore structures much close to char itself which may be due to potassium salt left in pores and is not easily leached with repeated water washings. In addition, KOH is more effective on the precursor itself than on its char of already developed porosity. FT-IR spectra show an increase in oxygen functionalties on the carbon surface as a result of activation process and the bands become stronger in the spectra of the acid-treated sample. The oxidized carbon sample showed relatively higher uptake of Pb2+ and MB and its surface chemistry plays the key role in their adsorption, while sharp decrease was observed in the uptake of phenol and mono-nitrophenols from aqueous solutions. An SEM study showed that air activation produce obvious voids reflecting its erosive effect on the external carbon surface. 相似文献
5.
Ni-Co films with different compositions and microstructures were produced on ITO glasses by electrodeposition from sulphate bath at 25 °C. Cyclic voltammograms give a result that the increase in the Co2+ concentration displaces Ni-Co alloy oxidation peaks to negative potential with high Co current distributions. It is observed that the content of cobalt in the films increases from 22.42% to 56.09% as the molar ratio of CoSO4/NiSO4 varying from 0.015/0.085 to 0.045/0.055 in electrolyte. XRD patterns reveal that the structure of the films strongly depends on the Co content in the deposited films. The saturation magnetization (Ms) moves up from 144.84 kA m−1 to 342.35 kA m−1 and coercivity (Hc) falls from 15.27 kA m−1 to 7.27 kA m−1 with the heat treatment temperature increasing from 25 °C to 450 °C. The saturation magnetization (Ms) and coercivity (Hc) move up from 340.97 kA m−1 and 7.98 kA m−1 to 971.58 kA m−1 and 18.62 kA m−1 with the Co content increasing from 22.42% to 56.09% after annealing at 450. 相似文献
6.
M. Olivares-Marín C. Fernández-González V. Gómez-Serrano 《Applied Surface Science》2006,252(17):5967-5971
Cherry stones (CS), an industrial product generated abundantly in the Valle del Jerte (Cáceres province, Spain), were used as precursor in the preparation of activated carbon by chemical activation with ZnCl2. The influence of process variables such as the carbonisation temperature and the ZnCl2:CS ratio (impregnation ratio) on textural and chemical-surface properties of the products obtained was studied. Such products were characterised texturally by adsorption of N2 at −196 °C, mercury porosimetry and density measurements. Information on the surface functional groups and structures of the carbons was provided by FT-IR spectroscopy. Activated carbon with a high development of surface area and porosity is prepared. When using the 4:1 impregnation ratio, the specific surface area (BET) of the resultant carbon is as high as 1971 m2 g−1. The effect of the increase in the impregnation ratio on the porous structure of activated carbon is stronger than that of the rise in the carbonisation temperature, whereas the opposite applies to the effect on the surface functional groups and structures. 相似文献
7.
Rui Zheng 《Journal of Molecular Spectroscopy》2011,265(2):102-105
The rovibrational spectrum of the N2-N2O van der Waals complex has been recorded in the N2O ν1 region (∼1285 cm−1) using a tunable diode laser spectrometer to probe a pulsed supersonic slit jet. The observed transitions together with the data observed previously in the N2O ν3 region are analyzed using a Watson S-reduced asymmetric rotor Hamiltonian. The rotational and centrifugal distortion constants for the ground and excited vibrational states are accurately determined. The band-origin of the spectrum is determined to be 1285.73964(14) cm−1. A restricted two-dimensional intermolecular potential energy surface for a planar structure of N2-N2O has been calculated at the CCSD(T) level of theory with the aug-cc-pVDZ basis sets and a set of mid-bond functions. With the intermolecular distance fixed at the ground state value R = 3.6926 Å, the potential has a global minimum with a well depth of 326.64 cm−1 at θN2 = 11.0° and θN2O = 84.3° and has a saddle point with a barrier height of 204.61 cm−1 at θN2 = 97.4° and θN2O = 92.2°, where θN2(θN2O) is the enclosed angle between the N-N axis (N-N-O axis) and the intermolecular axis. 相似文献
8.
B. Corcho-Corral C. Fernández-González V. Gómez-Serrano 《Applied Surface Science》2006,252(17):5961-5966
An abundant and low-cost agricultural waste as vine shoots (Vitis vinifera) (VS), which is generated by the annual pruning of vineyards, has been used as raw material in the preparation of powder activated carbon (AC) by the method of chemical activation with phosphoric acid. After size reduction, VS were impregnated for 2 h with 60 wt.% H3PO4 solution at room temperature, 50 and 85 °C. The three impregnated products were carbonised at 400 °C. The product impregnated at 50 °C was heated either first at 150-250 °C and then at 400 °C or simply at 350-550 °C in N2 atmosphere. The time of isothermal treatment after each dynamic heating was 2 h. The carbons were texturally characterised by gas adsorption (N2, −196 °C), mercury porosimetry, and density measurements. FT-IR spectroscopy was also applied. Better developments of surface area and microporosity are obtained when the impregnation of VS with the H3PO4 solution is effected at 50 °C and for the products heated isothermally at 200 and 450 °C. The mesopore volume is also usually higher for the products impregnated and heated at intermediate temperatures. 相似文献
9.
Liang-Chiun Chao Yu-Ren Shih Yao-Kai Li Jun-Wei Chen Jiun-De Wu Ching-Hwa Ho 《Applied Surface Science》2010,256(13):4153-8926
Nitrogen-doped ZnO thin films have been prepared by reactive ion beam sputtering deposition utilizing a capillaritron ion source. X-ray diffraction (XRD) analysis of the as-deposited film exhibits a single strong ZnO (002) diffraction peak centred at 34.40°. Post-growth annealing causes increase of grain size and decrease of c-axis lattice constant. Micro-Raman spectroscopy analysis of the as-deposited film shows strong nitrogen-related local vibration mode at 275, 582, 640 and 720 cm−1, whereas the E2 mode of ZnO at 436 cm−1 can barely be identified. Annealing at 500-800 °C causes decrease of 275, 582, 640 and 720 cm−1 and increase of 436 cm−1 intensity, indicating out-diffusion of nitrogen and improvement of ZnO crystalline quality. Unlike un-doped ZnO, the surface roughness of nitrogen-doped ZnO deteriorates after annealing, which is also attributed to the out-diffusion of nitrogen. A nitrogen concentration of ∼1021/cm3 was observed while type conversion from n-type to p-type was not achieved, which is likely due to the formation of ZnI-NO or (N2)O that act as donor/double donors. 相似文献
10.
Juan F. González José M. Encinar E. Sabio José L. Canito 《Applied Surface Science》2006,252(17):5999-6004
Activated carbons were prepared from waste tyres by gasification with steam and carbon dioxide and their characteristics were investigated. A two-stage activation procedure (pyrolysis at 800 °C in N2 atmosphere, followed by steam or carbon dioxide activation) was used for the production of activated samples. The effect of the activation temperature (750-900 °C) and the activation time (1-3 h) on the surface characteristics of the prepared carbon was investigated. Carbons produced to different degrees of burn-off were characterized by means of their nitrogen adsorption isotherms at 77 K. In both sets of experiments, the mesopore, micropore volume, and BET surface area increased almost linearly with the degree of activation. For burn-off values lower than 53%, the steam activation produced carbons with a narrower and more extensive microporosity and higher BET and external surface area than the carbon dioxide activation. As the activation proceeds (burn-off > 53%), a strong development of the mesoporosity in the carbons was observed and the micropores size distribution revealed broader micropores, that is, a more heterogeneous distribution. 相似文献
11.
Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl2 activation 总被引:1,自引:0,他引:1
In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl2. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m2 g−1. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m2 g−1 and 0.329 cm3 g−1. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature. 相似文献
12.
Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-FER results in hydrogen bonding of the adsorbed N2 molecules with the zeolite Si(OH)Al Brønsted acid groups. This hydrogen bonding interaction leads to activation, in the IR, of the fundamental NN stretching mode, which appears at 2331 cm−1. From the infrared spectra taken over a temperature range, while simultaneously recording integrated IR absorbance, temperature and nitrogen equilibrium pressure, the thermodynamics of the adsorption process was studied. The standard adsorption enthalpy and entropy resulted to be ΔH° = −20(±1) kJ mol−1 and ΔS° = −131(±10) J mol−1 K−1, respectively. 相似文献
13.
MgB2 was successfully fabricated through diffusion-controlled three-layered (B-Mg-B) technique under high pressure. Due to melting temperature of Mg, the material was pre-heat treated at 600 °C between 1 and 48 h. Optimum pre-heat treatment condition was found to be 600 °C for 48 h. Then, the compacted material was grinded and pelletized under pressure of 2 ton. The pellets were heat treated at 600-900 °C for 1-48 h. Optimum heat treatment condition was determined to be 800 °C for 1 h for formation of almost pure MgB2. Diffusion coefficient was determined with Fick's law and EDX data. Diffusion coefficient value for B in Mg matrix and Mg in B matrix was determined to be 1.66×10−7 and 3.14×10−8 cm2/sn, respectively. Best Tc value (39.4 K) was obtained for material heat treated at 800 °C for 1 h. A symmetric hysteresis was obtained for the best MgB2 material and magnetization decreased with increase in the temperature and the applied magnetic field. 相似文献
14.
Effect of combined activation on the preparation of high porous active carbons from granulated post-consumer polyethyleneterephthalate 总被引:1,自引:0,他引:1
Activated carbons were prepared from granulated post-consumer PET by combined activation including heat treatment with sulphuric acid (chemical activation) followed by steam activation. The effect of activation time, temperature, impregnation coefficient in the activation process was studied in order to optimize those reception parameters. One of the most important parameter in combined activation of crushed PET was found to be impregnation coefficient. It was defined that the optimal impregnation coefficient is equal 28%. Activation temperature is another variability which has a significant effect on the pore volume evolution. The increasing of activation temperature enhances the surface area and pore volumes of active carbons. The yield of final product which composes of nearly 15% is the factor limited the activation temperature above 800 °C. Textural characteristics of the samples were carried out by performing N2 adsorption isotherm at −196 °C. The obtained active carbons were mainly micro- and mesoporous and with BET apparent surface areas of up to 1030 m2/g. The adsorption capacity on methylene blue reaches 1.0 mmol/g, the sorption activity on iodine comes to 77%. 相似文献
15.
Hongqiang Wang Jianhong Yang Qifa Dai 《Journal of Physics and Chemistry of Solids》2008,69(10):2420-2425
Three activated carbons (ACs) for the electrodes of supercapacitor were prepared from cationic starch using KOH, ZnCl2 and ZnCl2/CO2 activation. The BET surface area, pore volume and pore size distribution of the ACs were evaluated using density functional theory method, based on N2 adsorption isotherms at 77 K. The surface morphology was characterized with SEM. Their electrochemical performance in prototype capacitors was determined by galvanostatic charge/discharge characteristics and cyclic voltammetry, and compared with that of a commercial AC, which was especially prepared for use in supercapacitors. The KOH-activated starch AC presented higher BET surface area (3332 m2 g−1) and larger pore volume (1.585 cm3 g−1) than those of the others, and had a different surface morphology. When used for the electrodes of supercapacitors, it exhibited excellent capacitance characteristics in 30 wt% KOH aqueous electrolytes and showed a high specific capacitance of 238 F g−1 at 370 mA g−1, which was nearly twice that of the commercial AC. 相似文献
16.
M.M. Socías-Viciana J. Tévar de Fez M.D. Ureña-Amate E. González-Pradas M. Fernández-Pérez F. Flores-Céspedes 《Applied Surface Science》2006,252(17):6053-6057
The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on natural and ammonium kerolite samples from aqueous solution at 10, 25 and 40 °C has been studied by using batch experiments. The experimental data points were fitted to the Langmuir equation in order to calculate the adsorption capacities (Xm) of the samples; two straight lines were obtained, which indicates that the adsorption process takes place in two different stages. Values for Xm1 (first stage) ranged from 1.1 × 10−2 mol kg−1 for natural kerolite at 40 °C up to 5.1 × 10−2 mol kg−1 for ammonium kerolite at 10 °C and the values for Xm2 (second stage) ranged from 9.1 × 10−2 mol kg−1 for natural kerolite at 40 °C up to 14 × 10−2 mol kg−1 for natural kerolite at 10 °C. The adsorption experiments showed on the one hand, that the ammonium kerolite is more effective than natural kerolite to adsorb chloridazon in the range of temperature studied and on the other hand, that the lower temperature, the more effective the adsorption of chloridazon on the adsorbents studied. 相似文献
17.
Improvement of electrical and optical properties of Ga and N co-doped p-type ZnO thin films with thermal treatment 总被引:1,自引:0,他引:1
Ga and N co-doped p-type ZnO thin films were epitaxially grown on sapphire substrate using magnetron sputtering technique. The process of synthesized Ga and N co-doped ZnO films was performed in ambient gas of N2O. Hall measurement shows a significant improvement of p-type characteristics with rapid thermal annealing (RTA) process in N2 gas flow, where more N acceptors are activated. The film rapid thermal annealed at 900 °C in N2 ambient revealed the highest carrier concentration of 9.36 × 1019 cm−3 and lowest resistivity of 1.39 × 10−1 Ω cm. In room and low temperature photoluminescence measurements of the as grown and RTA treated film, donor acceptor pair emission and exciton bound to acceptor recombination at 3.25 and 3.357 eV, respectively, were observed. 相似文献
18.
Nobutoshi Arai Hiroshi Tsuji Masayuki Ohsaki Toyotsugu Ishibashi Junzo Ishikawa 《Applied Surface Science》2009,256(4):954-957
We have investigated cathodeluminescence (CL) of Ge implanted SiO2:Ge and GeO2:Ge films. The GeO2 films were grown by oxidation of Ge substrate at 550 °C for 3 h in O2 gas flow. The GeO2 films on Ge substrate and SiO2 films on Si substrate were implanted with Ge-negative ions. The implanted Ge atom concentrations in the films were ranging from 0.1 to 6.0 at%. To produce Ge nanoparticles the SiO2:Ge films were thermally annealed at various temperatures of 600-900 °C for 1 h in N2 gas flow. An XPS analysis has shown that the implanted Ge atoms were partly oxidized. CL was observed at wavelengths around 400 nm from the GeO2 films before and after Ge−-implantation as well as from SiO2:Ge films. After Ge−-implantation of about 0.5 at% the CL intensity has increased by about four times. However, the CL intensity from the GeO2:Ge films was several orders of magnitude smaller than the intensity from the 800 °C-annealed SiO2:Ge films with 0.5 at% of Ge atomic concentration. These results suggested that the luminescence was generated due to oxidation of Ge nanoparticles in the SiO2:Ge films. 相似文献
19.
S. Giménez 《Applied Surface Science》2007,253(7):3547-3556
The chemical reactivity of CrN, ZrN, TiCxN1−x and naCo® PVD coatings on a WC-Co cemented carbide substrate with steel has been evaluated by means of the static interaction couples technique. Diffusion experiments with coated and uncoated tools were carried out at 900, 1100 and 1300 °C in order to establish the maximum temperature at which the substrate-coating-workpiece combinations are chemically stable. Computational equilibrium thermodynamics was used to identify the interaction products formed at elevated temperature and the chemical solubility of the different coating materials into iron. A metallic (Fe, Co) fcc solid solution was identified at the steel side of the interface from 1100 °C on for all the coated tools and from 900 °C for the uncoated carbide. In addition to this interaction product, the ?-carbide was identified at 1300 °C on the WC-Co side of the interface. Both of the experimental findings and thermodynamic equilibrium solubility calculations demonstrated that the PVD-coated WC-Co tools exhibit a lower chemical reactivity with respect to the uncoated tools. 相似文献
20.
M. Deepa 《Applied Surface Science》2005,252(5):1568-1580
A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO3) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV-vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film characterization. The as-deposited and the film annealed at 60 °C are composed of nanosized grains with a dominant amorphous phase, as well as open structure which ensues from a nanoporous matrix. This ensures a greater number of electroactive sites and a higher reaction area thereby manifesting in electrochromic responses superior to that of the films annealed at higher temperatures. The films annealed at temperatures ≥250 °C are characterized by a prominent triclinic crystalline structure and a hexagonal phase co-exists at temperatures ≥400 °C. The deleterious effect on the electrochromic properties of the film with annealing is ascribed to the loss of porosity, densification and the increasing crystallinity and grain size. Amongst all films under investigation, the film annealed at 60 °C exhibits a high transmission modulation (ΔT ∼ 68%) and coloration efficiency (η ∼ 77.6 cm2 C−1) at λ = 632.8 nm, charge storage capacity (Qins ∼ 21 mC cm−2), diffusion coefficient (6.08 × 10−10 cm2 s−1), fast color-bleach kinetics (tc ∼ 275 s and tb ∼ 12.5 s) and good electrochemical activity, as well as reversibility for the lithium insertion-extraction process upon cycling. The remarkable potential, which the film annealed at 60 °C has, for practical “smart window” applications has been demonstrated. 相似文献