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1.
–SO 3H modified mesoporous silica adsorbent with water sorption capacity and fast desorption kinetics for water sorption was synthesized and studied via a combined experimental and numerical approach. Mesoporous silica was synthesized using sol–gel method in H 2SO 4 medium. The water adsorption isotherms and kinetics over the silica were evaluated by a dynamic water vapor sorption analyzer. Mesoporous silica was modeled using annealing simulation with CVFF forcefield. –SO 3H modified mesoporous silica was modeled by the attachment of –SO 3H to the surface hydroxyl groups and validated. Simulation results show water sorption capacity at low relative humidity (RH) increases with –SO 3H loading on mesoporous silica. Energy distribution of intermolecular interaction and micro-view of water sorption over –SO 3H modified mesoporous silica reveal that although strong interaction (intermolecular interaction of ?40 to ?20 kcal/mol) between hydrophilic groups (–SO 3H) with water can increase water sorption capacity at low RH, weak H 2O–H 2O interaction (intermolecular interaction of ?20 to ?10 kcal/mol) dominated water sorption capacity at both low and high RH. 相似文献
2.
In present work, we describe the synthesis of graphite intercalation compounds with perrhenic acid (HReO4-GIC) through the anodic oxidation of graphite in aqueous perrhenic acid solution and their thermal exfoliation. Due to electrochemical treatment of graphite in perrhenic acid solution, ReO4− ions are intercalated into interlayer spaces of graphite. Anodic oxidation of graphite in HReO4 solution leads to the formation of 3-stage GIC. Simultaneously, some amount of perrhenic acid becomes deposited on the graphite surface and edges. In the next step, thermal treatment of the previously synthesized GIC was performed, causing both the exfoliation of graphitic structure and transformation of perrhenic acid into rhenium oxides on the surface of graphene layers. The yielded product was exfoliated graphite-ReO2/ReO3 composite. The obtained composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Additionally, specific surface area of the exfoliated materials was measured. 相似文献
3.
Exfoliated graphite has been synthesized by first synthesizing H 2SO 4 intercalated compound in a H 2O 2‐H 2SO 4 mixture, followed by exfoliation under microwave irradiation. Poly(arylene disulfide)/graphite nanocomposites were then fabricated by absorbing cyclic(arylene disulfide) oligomers into the pores of exfoliated graphite. Subsequently, the nanocomposite precursor was subjected to heat treatment to carry out the in situ ring‐opening polymerization of the oligomers via free radical mechanism. The as‐prepared nanocomposite exhibited a exfoliated nanostructure as evidenced by transmission electron microscopy (TEM) observation. The nanocomposite with a very small amount of graphite, 5 wt%, possesses a highly electrical conductivity of 4 S/cm, therefore, many applications can be found as conductive materials. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
In this work, we present the application of an exfoliated graphite electrode modified with gold nanoparticles (AuNPs) for the detection of As(III) in acidic media. Gold nanoparticles were deposited on the surface of an exfoliated graphite electrode by electrodeposition at a potential window of ?0.2 V to 1.2 V. This was followed by activation in 0.5 M H 2SO 4 with 10 cycles from 0.6 V to 1.4 V. The modification of exfoliated graphite (EG) showed an increased electroactive surface area of the electrode and improved peak current output in a Fe(CN) 63?/4? redox probe. EG‐AuNPs electrode was used to detect As(III) in 1.0 M HNO 3 using square wave anodic stripping voltammetry (SWASV) technique at optimum conditions of pH 3, deposition potential of ?0.8 V, deposition time of 180 s, frequency of 5 Hz and pulse amplitude of 50 mV. The EG‐AuNPs electrode detected As(III) in solution to a limit of 0.58 ppb with regression of 0.9993. The method reported is simple, cheap and possesses good reproducibility. The developed electrochemical sensor was applied in the detection of As (III) in an industrial real water sample. The results of the real water sample analysis from the developed method are comparable with the inductively coupled plasma – optical emission spectroscopy (ICP‐OES) results. 相似文献
5.
High surface area silicon carbide-derived carbons (Si-CDCs) synthesized by chlorination of beta silicon carbide (βSiC) with two different particle sizes (6 μm and 50 nm) show different porosities with graphitic structure. Transmission electron microscopy, Raman spectroscopy and argon (Ar) and carbon dioxide (CO 2) sorption analyses are used to examine the textural properties of the Si-CDCs. The results show that the particle size of the precursor affects the surface area and porosity of carbons. Furthermore, an additional heat treatment of the Si-CDC with 50-nm particle size for 24 h at 1,000 °C results in a collapse of the pore structure and reduces the surface area. The capacitive behaviours are investigated in H 2SO 4 and in tetraethyl ammonium tetrafluoroborate (TEABF 4)/acetonitrile (AN). The electrochemical performance of the Si-CDCs is influenced by the particle size, surface area, pore volume and pore size distribution. The Si-CDCs exhibit capacitances in 1 M H 2SO 4 of up to 179 F g ?1 and very stable charge–discharge performance over 5,000 cycles. This study shows the crucial importance of ultramicropores less than 1 nm combined with nanosized particles for achieving high capacitance in aqueous electrolyte. Moreover, the graphitic degree at the surface of the Si-CDCs enhances considerably the rate capability and stability in both electrolytes. 相似文献
6.
Adsorption and structural properties of the initial natural mineral sorbent M 45C 20 and the sorbent treated with 2.33 M H 2SO 4 were studied. The sorbent mainly consists of montmorillonite and clinoptilolite. Aluminum, calcium, magnesium, sodium, and potassium ions are removed from the structure under the action of the acid. The specific surface, porosity of the sorbent, and pore size increase during this process. The sorption of ammonium ions in the natural samples predominantly follows the ion-exchange mechanism (exchange to calcium, magnesium, sodium, and potassium ions). The acid treatment changes the composition of the cation-exchange complex and results in an increase in the sorption capacity to ammonium ions by a factor of ??1.3. 相似文献
7.
The objective of this work is to study the influences of silica supports and PEG additive on the sorption performance of molecular basket sorbent(MBS) for CO_2 capture consisting of polyethylenimine and one of the following supports: SBA-15(2-D structure), TUD-1(3-D sponge-like structure) and fumed silica HS-5(3-D disordered structure). Effects of the supports regarding pore structures and pore properties, the PEI loading amount as well as the sorption temperature were examined. Furthermore, polyethylene glycol(PEG) was introduced as an additive into the sorbents and its effect was investigated at different PEI loadings and sorption temperatures. The results suggest that the pore properties of MBS(after PEI loading) play a more important role in the CO_2 sorption capacity, rather than those of the supports alone.MBS with 3D pore structure exhibits higher CO_2 sorption capacity and amine efficiency than those with 2D-structured support. Among the sorbents studied, fumed silica(HS-5) based MBS showed the highest CO_2 sorption capacity in the temperature range of 30-95 °C, probably due to its unique interstitial pores formed by the aggregation of polymer-loaded SiO_2 particles. It was found that the temperature dependence is directly related to the PEI surface coverage layers. The more PEI surface coverage layers, the higher diffusion barrier for CO_2 and the stronger temperature dependence of CO_2 capacity. 3D MBS exceeds 2D MBS at the same PEI coverage layers due to lower diffusion barrier. Adding PEG can significantly enhance the CO_2 sorption capacity and improve amine efficiency of all MBS, most likely by alleviating the diffusion barrier within PEI bulk layers through the inter-molecular interaction between PEI and PEG. 相似文献
8.
Overall kinetic and potentiometric studies of the growth of porous anodic alumina films in saturated H 2SO 4+Al 2(SO 4) 3 electrolyte showed non-saturation conditions inside the pores and supersaturation conditions at the pore surface/electrolyte
interface where the field and the solid surface catalyse the formation of colloidal Al 2(SO 4) 3 micelles. Suitable high-strength field thermodynamically sustained electrochemical and chemical kinetic equations were formulated.
It was shown that the diameter and surface fraction of charge exchange at the pore bases, the real pore wall surface fraction
where oxide dissolution occurs, and its rate are strongly affected by the conditions. The mechanism of growth and structure
of the films are quite different from those in H 2SO 4. A mechanism of regular film growth is imposed and the critical current density, above which pitting appears, strongly increases.
The formulated theory may predict improved or new Al anodizing technologies.
Electronic Publication 相似文献
9.
The kinetics of growth of porous anodic alumina films in pure H 2SO 4, in mixtures of H 2SO 4 and Al 2(SO 4) 3 and in Al(HSO 4) 3, NaHSO 4 and KHSO 4 electrolytes were studied. The latent physicochemical processes at the pore base surface/electrolyte interface, across the
barrier layer, inside the metal/oxide interface and at the pore wall surface/electrolyte interface and their mechanisms were
revealed. High field strength equations were formulated describing the ionic migrations from the pore base surface. These
showed that, at constant current density and temperature, the inverse of the pore base square diameter depends linearly on
the inverse of the H + activity in the anodizing solution and that this diameter increases with H + activity, in agreement with the experimental results. The mechanism of electrolyte anion incorporation inside the barrier
layer and the real distribution of the anion concentration across both the barrier layer and pore walls were deduced. The
effects of the different kinds and concentrations of the electrolyte anions and cations on both the above processes and their
mechanisms were also examined.
Electronic Publication 相似文献
10.
Sorption of industrial oil by expanded graphite prepared from residual graphite hydrosylfate at 300-900°C was studied. The sorption isotherms of both neat oil and oil from its aqueous suspension were measured. The sorption capacity for oil was studied as influenced by the specific surface area and specific volume of expanded graphite sorbent. 相似文献
11.
Nanocomposites based on PtPd nanoparticles with chemical ordering like disordered solid solution on surface of multilayer graphene have been prepared through thermal shock of mechanically obtained mixture of double complex salt [Pd(NH 3) 4][PtCl 6] and different carbon materials–exfoliated graphite, graphite oxide and graphite fluoride. An effect of original carbon precursors on formation of PtPd bimetallic nanoparticles was studied using X-ray absorption spectroscopy (XAFS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was shown that the distribution of bimetallic nanoparticles over the multilayer graphene surface as well as the particles size distribution is controlled by the graphene precursors. For all nanocomposites, the surface of the nanoparticles was found to be Pd-enriched. In case when the thermal exfoliated graphite and graphite oxide were used as the graphene precursors a thin graphitized layer covered the nanoparticles surface. Such a graphitized layer was not observed in the nanocomposite, which used the fluorinated graphite as the precursor. 相似文献
12.
The sorption of methylene chloride in neat PEEK was investigated as a function of temperature, sample thickness, surface treatment, and thermal history. The solubility of H 2CCl 2 in neat PEEK is 23 wt.% and is independent of thickness. Both surface treatment and thermal annealing strongly affect the rate of penetration; the as-Received material sorbs H 2CCl 2 more rapidly than abraded or annealed samples; however, the bulk solubility is independent of surface treatment. The sorption and desorption processes are considerably different, and the diffusion process is not simple Fickian Case I. The penetrant advances as a sharp front, suggesting a two-step, relaxation-controlled diffusion mechanism. 相似文献
13.
A method of preparing nanoporous polymer networks containing N-vinylpyrrolidone units via the crosslinking radical copolymerization in bulk performed in the presence of amphiphilic N-vinylpyrrolidone copolymers with the branched morphology and different physicochemical characteristics is developed. It is shown that macromolecular nanoobjects may be extracted from polymer composites using good solvents, such as chloroform and isopropyl alcohol. The physicomechanical, thermal, and diffusion–sorption properties of polymer composites before and after their extraction are compared. SEM and low-temperature nitrogen adsorption measurements reveal that nanosized pores are contained in the network copolymers after extraction of the polymer additives. The specific surface area, total pore volume, pore size, and pore-size distribution are determined. The maximum specific surface area of polymer networks attains ~26 m 2/g, and mesopores compose the main type of pores. 相似文献
14.
The effect of the type of the silica gel pore structure on the surface properties of the Ni-silica gel catalyst precursors
for the vegetable oil hydrogenation process has been examined applying N 2 sorption and X-ray photoelectron spectroscopy techniques. The nickel catalyst precursors with identical composition (SiO 2/Ni = 1.0) has been synthesized by precipitation of Ni(NO 3) 2 · 6H 2O solution with Na 2CO 3 solution on the three types of silica gel with different pore structures. It is shown that the usage of the silica gel supports
with different texture as source of SiO 2 causes different location of Ni-species into the support pores and on the external surface area. The XPS data confirm the
formation of surface species with different strength of interaction and different dispersion. These surface characteristics
of the precursors will predetermine the formation of the active nickel metallic phase as well as the mass transfer of the
reactants and products to and from the catalytic sites. 相似文献
15.
以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H 2SO 4环境与H 2SO 4+H 3PO 4混酸环境和KMnO 4与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明:GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H 2SO 4 H 3PO 4混酸环境下制备的GO含氧官能团较多,并且(KMnO 4)与鳞片石墨的最佳比例是1:4。 相似文献
16.
Experimental results on the physico-chemical properties of ambiently dried sodium silicate based aerogels catalyzed with various
acids are reported. The aerogels were prepared by hydrolysis and polycondensation of sodium silicate followed by subsequent
washings, surface chemical modification and ambient pressure drying using 10 various acid catalysts consisting of strong and
weak acids. The strength and concentration of acids have the major effect on the gelation of sol and hence the physico-chemical
properties of the silica aerogels. Strong acids such as HCl, HNO 3 and H 2SO 4 resulted in shrunk (70–95%) aerogels whereas weak acids such as citric and tartaric acids resulted in less shrunk (34–50%)
aerogels. The physical properties of silica aerogels were studied by measuring bulk density, volume shrinkage (%), porosity
(%), pore volume, thermal conductivity, contact angle with water, Transmission Electron Microscopy (TEM), Atomic Absorption
Spectroscopy (AAS), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric-Differential Thermal (TG-DT) analyses
and N 2 adsorption–desorption BET surface analyzer. The best quality silica aerogels in terms of low density (0.086 g/cm 3), low volume shrinkage (34%), high porosity (95%), low thermal conductivity (0.09 W/m K) and hydrophobic (148°) were obtained
for molar ratio of Na 2SiO 3:H 2O:citric acid:TMCS at 1:146.67:0.72:9.46 with 20 min gelation time. The resulting aerogels exhibited the thermal stability
up to around 420 °C. 相似文献
17.
We present in this paper the thermal analysis (calorimetry, TG and DSC) of the first stage P 2O 3F 4 graphite intercalate compound in atmospheric pressure and high pressure. By heating we obtain always exfoliation phenomenon. The heating of exfoliated, graphite shows an important oxidation resistance in comparison with another exfoliated graphite. This oxidation resistance has been studied also by thermal analysis like TG, in oxygen atmosphere. Carbon foil rebuilding from exfolied graphite keeps these interesting antioxidation properties. 相似文献
18.
Overall kinetic and chronopotentiometric studies were performed during Al anodising in H 2SO 4, 0–5% w/v, bath solutions pure and saturated by Al 2(SO 4) 3. Peculiarities in film growth mechanism and nanostructure in these cases appeared, like significant differences of porosity
and its dependence on film thickness, different critical current density above which pitting appears, salt deposition on pitted
surface regions in saturated bath, etc. The different conditions inside pores are responsible for this behaviour like almost
depletion of H + during a long initial transient stage in the first case, supersaturation and formation of Al 2(SO 4) 3 nanoparticle micelles on pore surface in the second case, etc. Differences in film growth mechanism also appeared between
these and alike baths at higher acidity. Anodising in low acidity saturated baths shows superiority for growing low porosity
films at specific conditions. New technologies may be suggested to produce optimal films of desired structure. 相似文献
19.
Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors.
The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance
in aq. H 2SO 4, the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3·5 V (instead of
1 V in the case of aq. H 2SO 4), the specific capacitance and energy density being 75 F/g and 31·9 Wh kg −1 respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics
of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior
to that of single-walled and multi-walled carbon nanotubes. 相似文献
20.
Sorption of heavy oil by swollen graphites obtained from residual graphite hydrosulfate at 300- 900°C was studied. The dependence of the sorption capacity for oil on the specific surface area and specific volume of the swollen graphite sorbent was analyzed. 相似文献
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