SURFACE REARRANGEMENTS OF OXYGEN PLASMA TREATED POLYSTYRENE： SURFACE DYNAMICS AND HUMIDITY EFFECT

The time evolution of oxygen plasma treated polystyrene(PS)surfaces was investigated upon storing them in theair under controlled humidity conditions.The methods of water contact angle,X-ray photoelectron spectroscopy(XPS),sumfrequency generation(SFG)vibrational spectroscopy,and atomic force microscopy(AFM)were used to infer the surfaceproperties and structure.Chemical groups containing oxygen were formed on the PS surface with the plasma treatment,demonstrated by water contact angle and XPS.The surface polarity decayed markedly on time,as assessed by steady increasein the water contact angle as a function of storage time,from zero to around 60°.The observed decay is interpreted as arisingfrom surface rearrangement processes to burying polar groups away from the uppermost layer of the surfaces,which is incontact with air.On the other hand,XPS results show that the chemical composition in the first 3 nm surface layer isunaffected by the surface aging,and the depth profile of oxygen is essentially the same with time.A possible change of PSsurface roughness was examined by AFM,and it showed that the increase of water contact angle during surface aging couldnot be attributed to surface roughness.Thus,it is concluded that surface aging is attributable to surface reorganization andthe motion of oxygen containing groups is confined within the XPS probing depth.SFG spectroscopy,which is intrinsicallyinterface-specific,was used to detect the chemical structure of PS surface at the molecular level after various aging times.The results are interpreted as follows.During the aging of the plasma treated PS surfaces,the oxygen containing groupsundergo reorientation processes toward the polymer bulk and/or parallel to the surface,while the CH_2 moiety stands up onthe PS surface.Our results indicate that the surface configuration changes do not require large length scale segmentalmotions or migration of macromolecules.Motions that are responsible for surface configuration changes could be relativelysmall rotational motions.The aging behaviors under different relative humidity conditions were shown to be similar from18% to 91%,whereas the kinetics of surface polarity decays were faster in higher relative humidity.Here,the surfacerearrangement of polystyrene films that were previously treated by oxygen plasma and aged,and was investigated in terms ofcontact angle after the water immersion.The contact angles of the water-immersed samples were found to change andapproach the initial values before the immersion asymptotically.     

非晶碳纳米球的低温石墨化(英文)

The investigation by SEM/TEM, porosity, and X-ray diffraction measurements of the graphitization process starting from amorphous carbon nanospheres, prepared by glucose carbonization, is reported. Aspects studied are the annealing temperature in the 750–1000 °C range, the type of inert carrier gas, and time of treatment in the 2–6 h range. It is investigated how these parameters influence the structural and morphological characteristics of the carbon materials obtained as well as their nanostructure. It is shown that it is possible to maintain after graphitization the round-shaped macro morphology, a high surface area and porosity, and especially a large structural disorder in the graphitic layers stacking, with the presence of rather small ordered domains. These are characteristics interesting for various catalytic applications. The key in obtaining these characteristics is the thermal treatment in a flow of N2. It was demonstrated that the use of He rather than N2 does not allow obtaining the same results. The effect is attributed to the presence of traces of oxygen, enough to create the presence of oxygen functional groups on the surface temperatures higher than 750 °C, when graphitization occurs. These oxygen functional groups favor the graphitization process.     

Metal-organic-framework-derived formation of Co–N-doped carbon materials for efficient oxygen reduction reaction

Non-precious metal nitrogen-doped carbonaceous materials have attracted tremendous attention in the field of electrochemical energy storage and conversion. Herein, we report the designed synthesis of a novel series of Co-N-C nanocomposites and their evaluation of electrochemical properties. Novel yolkshell structured Co nanoparticles@polymer materials are fabricated from the facile coating polymer strategy on the surface of ZIF-67. After calcination in nitrogen atmosphere, the Co–N–C nanocomposites in which cobalt metal nanoparticles are embedded in the highly porous and graphitic carbon matrix are successfully achieved. The cobalt nanoparticles containing cobalt metal crystallites with an oxidized shell and/or smaller(or amorphous) cobalt-oxide deposits appear on the surface of graphitic carbons. The prepared Co–N–C nanoparticles showed favorable electrocatalytic activity for oxygen reduction reactions,which is attributed to its high graphitic degree, large surface area and the large amount existence of Co–N active sites.     

Core-shell meso/microporous carbon host for sulfur loading toward applications in lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and the shuttling of highly dissoluble lithium polysulfides generated during the cycles.Loading sulfur into porous carbons has been proved to be an effective approach to alleviate these issues.Mesoporous and microporous carbons have been widely used for sulfur accommodation,but mesoporous carbons have poor sulfur confinement,whereas microporous carbons are impeded by low sulfur loading rates.Here,a core-shell carbon,combining both the merits of mesoporous carbon with large pore volume and microporous carbon with effective sulfur confinement,was prepared by coating the mesoporous CMK-3 with a microporous carbon(MPC) shell and served as the carbon host(CMK-3 @MPC) to accommodate sulfur.After sulfur infusion,the as-obtained S/(CMK-3@MPC) cathode delivered a high initial capacity of up to 1422 mAh·g~(-1) and sustained 654 mAh·g~(-1) reversible specific capacity after 36 cycles at 0.1 C.The good performance is ascribed to the unique core-shell structure of the CMK-3@MPC matrix,in which sulfur can be effectively confined within the meso/microporous carbon host,thus achieving simultaneously high electrochemical utilization.     

Preparation and Characterization of Nano-Structured SiO2 Thin Films on Carbon Steel

Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed by AFM. The thin films were constituted by compact particles of SiO2, and there was no Fe in the films. In the process of film forming, the SiO2 colloid particles were deposited or absorbed directly onto the surface of carbon steel substrates that were activated by acid solution containing inhibitor, and corrosion of the substrates was avoided. The nano-structured SiO2 thin films that were prepared had excellent protective efficiency to the carbon.     

Experimental and Theoretical Study of the Effect of Moisture on Methane Adsorption and Desorption by Activated Carbon at 273.5 K

Adsorption and desorption of methane by activated carbon (AC) at constant temperature and at various pressures were investigated. The effect of moisture was also studied. A volumetric method was used, up to 40 bar, at a temperature of 273.5 K. Results of a dry AC sample were compared with those obtained from a moist sample and two different ACs with different physical and surface properties were used. As expected, the results showed that the existence of moisture, trapped in the AC pores, could lead to a decrease in the amount of methane adsorbed and a decrease in the amount of methane delivered during desorption. To model the experimental results, a large variety of adsorption isotherms were used. The regressed parameters for the adsorption isotherms were obtained using the experimental data generated in the present study. The accuracy of the results obtained from the different adsorption isotherms was favorably compared.     

The Effect of Gelatin on the Preparation of Silica Coated Iron Particles

A method is described for coating fine iron particles(～1μm) with a uniform silica layer,produced by the hydrolysis of tetraethyl orthosilicate.The presence of a small amount of gelatin on the surface of the iron particles facilitates this process.The X-ray photoelectron measurements indicated that the gelatin interacted with the surface of the iron particles by means of both nitrogen(in -NH2 groups) and oxygen(in -COOH groups) and then bound to the silica.The silica coating increases the resistance of the iron particles to oxidation on heating in air,which makes the temperature at which an observable oxidization occurs from 330 ℃ to 400 ℃ raised.     

乳液催化剂存在下空气辅助甲酸氧化法使油品脱硫(英文)

Catalytic oxidative desulfurization(ODS) of model oil and commercial oil samples was investigated using an air-assisted performic acid oxidation system with a phase transfer or emulsion catalyst comprising a quaternary ammonium salt-based heteropolyoxometalate.Different emulsion catalysts with a Keggin type heteroployoxometalate anion(containing W,Mo,and V) and cetyltrimethylammonium bromide cation were prepared and characterized by X-ray fluorescence,Fourier transform infrared spectroscopy,and scanning electron microscopy.[C16H33N(CH3)3]3[PW9Mo3O40] was the most effective catalyst in the current oxidation system,which reduced the sulfur content of the model oil from 1275 μg/g to 57 μg/g.The reactivity order of different model sulfur compounds was thiophene < dibenzothiophene < 4,6-dimethyldibenzothiophene. The ODS of model sulfur compounds followed first order kinetics with apparent activation energy from 29 to 27 kJ/mol.The catalysts also performed efficiently in the ODS of the industrial oil samples,including untreated naphtha,light gas oil,heavy gas oil,and Athabasca oil sands derived bitumen,for which sulfur removal rates were 83%,85%,68% and 64%,respectively.     

Pore size effects of nanoporous carbons with ultra-high surface area on high-pressure hydrogen storage

In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores(0.65-0.85 nm) could be the most effective pores on excess H2 uptake at 1 bar, however, micropores(0.85-2 nm) would play a more important role in excess H2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H2 uptake at room temperature, which was clearly different from that at 77 K.For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H2 uptake capacity at room temperature.     

SURFACE-ENHANCED RAMAN SCATTERING OF WATER IN HIGHLY CONCENTRATED NaClO_4 SYSTEMS

A highly concentrated NaClO_4 as a main supporting electrolyte was used to break hydrogen-bonded water structure in systems studied, by which strong surface-enhanced Raman scattering (SERS) signals of water from silver electrodes were detected in the system having a ten times lower halide concentration than the ordinary one; and a similar phenomenon was also observed in a system containing pseudo-halide SCN~- ions. The SERS spectra obtained in 0.1 mol/L LiCl and 3.0 mol/L LiClO_4 indicate the presence of two kinds of water molecules with very different behaviors on the surface. This peculiar phenomenon is discussed in details. It is achievable to extend SERS study on adsorbed water by adequate choice of electrolyte and control of surface treatment to the electrode in order to have a deeper insight into the complex structure of the electrochemical interface.     

易化输运过程的简单化学模型及其在Wyman-Murray扩散中的应用(英文)

A simple chemical kinetic model is developed which describes the behavior of small ligands that can bind reversibly with large carrier molecules with slower intrinsic rates of transport. Under certain conditions, which we describe, the presence of the slower carriers in fact enhances the transport of the ligand. This is the chemical version of Wyman-Murray′ s facilitated diffusion. The simple model illuminates the driven nature of the enhancement of the transport by the carrier molecules: we show that the facilitated transport depends crucially on a"grand canonical" setting in which the free ligand concentrations are kept constant in the presence of the facilitating protein, in contrast to a canonical setting with constant total ligand concentrations. Results from the simple model are compared to previous experimental and theoretical results for Wyman-Murray facilitated diffusion of oxygen and carbon monoxide in muscle. A relation is established between the association-dissociation rates and the down-stream ligand concentration, or back pressure for oxygen, required for the facilitation effect to occur.     

POROUS MEMBRANE TEMPLATED SYNTHESIS OF POLYMER PILLARED LAYER

The anodic porous alumina membranes with a definite pore diameter and aspect ratio were used as templates tosynthesize polymer pillared layer structures. The pillared polymer was produced in the template membrane pores, and thelayer on the template surfaces. Rigid cured epoxy resin, polystyrene and soft hydrogel were chosen to confirm themethodology. The pillars were in the form of either tubes or fibers, which were controlled by the alumina membrane pore surface wettability. The structural features were confirmed by scanning electron microscopy results.     

CNTs tuning and vertical alignment in anodic aluminium oxide membrane

Anodic aluminium oxide (AAOM) membranes were used for template growth of carbon nanotubes (CNT) inside their pores by chemical vapour deposition (CVD) of different hydrocarbons, in the absence of transition metal catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and the external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity, and quality of CNTs in terms of diameter (up to very thin CNT), carbon order, length, arrangement (i.e. number of tubes for each channel), purity, that are critical requisites for several applications were optimized by investigating the effect of changing the hydrocarbon feedstock gas, also in the presence of hydrogen. The samples produced using methane as a feedstock have a well ordered structure. The role of the alumina channels surface during the CNT growth has been investigated and its catalytic activity has been proved for the first time.     

Selective Oxidation of Propane by Lattice Oxygen of Vanadium-Phosphorous Oxide in a Pulse Reactor

Selective oxidation of propane by lattice oxygen of vanadium-phosphorus oxide (VPO) catalysts was investigated with a pulse reactor in which the oxidation of propane and the re-oxidation of catalyst were implemented alternately in the presence of water vapor. The principal products are acrylic acid (AA),acetic acid (HAc), and carbon oxides. In addition, small amounts of C1 and C2 hydrocarbons were also found, molar ratio of AA to HAc is 1.4-2.2. The active oxygen species are those adsorbed on catalyst surface firmly and/or bound to catalyst lattice, i.e. lattice oxygen; the selective oxidation of propane on VPO catalysts can be carried out in a circulating fluidized bed (CFB) riser reactor. For propane oxidation over VPO catalysts, the effects of reaction temperature in a pulse reactor were found almost the same as in a steady-state flow reactor. That is, as the reaction temperature increases, propane conversion and the amount of C1 C2 hydrocarbons in the product increase steadily, while selectivity to acrylic acid and to acetic acid increase prior to 350℃ then begin to drop at temperatures higher than 350℃, and yields of acrylic acid and of acetic acid attained maximum at about 400℃. The maximum yields of acrylic acid and of acetic acid for a single-pass are 7.50% and 4.59% respectively, with 38.2% propane conversion. When theamount of propane pulsed decreases or the amount of catalyst loaded increases, the conversion increases but the selectivity decreases. Increasing the flow rate of carrier gases causes the conversion pass through a minimum but selectivity and yields pass through a maximum. In a fixed bed reactor, it is hard to obtainhigh selectivity at a high reaction conversion due to the further degradation of acrylic acid and acetic acid even though propane was oxidized by the lattice oxygen. The catalytic performance can be improved inthe presence of excess propane. Propylene can be oxidized by lattice oxygen of VPO catalyst at 250℃, nevertheless, selectivity to AA and to HAc are even lower, much more acetic acid was produced (molar ratio of AA to HAc is 0.19:1-0.83:1) though the oxidation products are the same as from propane.     

Evolution of Gold Species in an Au/CeO2 Catalyst and Its Impact on Activity for CO Oxidation

An Au/ceria(0.44%, mass fraction) catalyst containing gold ions was prepared by a modified deposition precipitation method, and the evolution of gold ions in the catalyst and its influence on the catalysis of CO oxidation were investigated. It was found that the as-prepared catalyst containing gold ions with high valence could fully oxidize CO at –10 °C initially but was deactivated gradually at low temperatures during the reaction with CO or treatment by unpurified air. The deactivation of the catalyst during CO oxidation or treatment of it by unpurified air was independent and progressive at low temperatures while the activity of the catalyst at relatively high temperatures was maintained well. During the reaction with CO or treatment by unpurified air, the XPS results indicate that gold species evolved from high valence to low valence and the diffuse reflectance UV-Vis spectra show that high valence gold was reduced to charged gold clusters, gold clusters grew to small gold crystals and small gold crystals grew to large gold particles. Accordingly, the high valence gold corresponded to the activity at low temperatures and the metallic gold was active and relatively stable at high temperatures. The turnover frequencies(TOF) of the catalysts treated by different methods at 273 K decreased with the evolution of gold species from high valence to low valence, no maximum of TOF was observed although gold particles in the catalyst attained to about 2―3 nm during the treatment. An Au/ceria catalyst with a gold load of 0.87% (mass fraction) maintained a good activity for CO oxidation within 18 h at room temperature. The catalysts were characterized via transmitted electronic microscopy(TEM), inductively coupled plasma optical emission spectrometry(ICP-OES), X-ray diffraction(XRD) and BET specific surface area and UV-Vis DRS as well.     

Electrolessly Plated Ni-Zn（Fe）-P Alloy and Its Corrosion Resistance Properties

The autocatalytic deposition of Ni-Zn(Fe)-P alloys has been carried out on substrate of carbon steel from a bath containing nickel sulfate, zinc sulfate, sodium hypophosphite, sodium citrate and boric acid. The effects of pH and the molar ratio of NiSO4/ZnSO4 on the deposition rate and the composition of deposits have been studied. It was found that the presence of zinc sulfate in the bath has an inhibitory effect on the alloy deposition. The structure and the surface morphology of Ni-Zn(Fe)-P coatings were characterized with XRD and SEM, respectively. The alloys plated under the experimental conditions consisted of an amorphous phase coexisting with a crystalline cubic Ni phase (poly-crystalline). The surface morphology of the coating is dependent on the deposition parameters. The corrosion resistance of the Ni-Zn(Fe)-P deposits was examined via mass loss tests and anodic polarization measurements, respectively. The results show that the surface morphologies of the deposits and the corrosion resistance of the deposits have been improved. The results of mass loss tests almost accord with those of anodic polarization measurements. The corrosion mechanisms of Ni-Zn(Fe)-P alloys in NaCl and NaOH solutions were investigated by means of EDX. The deposit immersed in an NaCI or an NaOH solution contains more content of oxygen and less contents of the metals(except Fe) than that placed in air, which shows that the NaCl or NaOH solution can accelerate the oxidation of the deposit.     

Solid state reactions of nitrogenous heterocyclic compounds (Ⅱ)——Solid state reactions of indole with carbonyl compounds

Solid state Michael addition reaction of indole with α,β-unsaturaled carbonyl compounds was carried out,by which a series of compounds containing three different heterocyclic groups binding to one carbon atom were obtained.In the presence of Lewis acid,indole could undergo the solid state condensation reaction with aromatic ketones and aldehydes or quinones.The solid state reaction showed higher selectivity and yield than solution reaction The structures of products were identified by IR,1H NMR,MS,elemental analysis and X-ray crystal analysis.The reaction mechanism was also proposed.     

Microporous carbon nanofibers prepared by combining electrospinning and phase separation methods for supercapacitor

Microporous carbon nanofibers(MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone(PVP).PVP together with a mixed solvent of N,N-Dimethylformamide and dimethyl sulfoxide was used as poreforming agent.The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated.The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g.The good performance was owing to the high specific surface area and the large amount of micro-pores,which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process.This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance.     

Preparation and Characterization of Carbon Nanotubes-Coated Cordierite for Catalyst Supports

The carbon nanotubes-coated cordierite (CNTs-cordierite) was fabricated by pyrolysis of ethine on cordierite with iron catalyst, which was penetrated into the cordierite substrate by vacuum impregnation. The cordierite substrate, carbon naontubes, and CNTs-cordierite were characterized by SEM. TEM/HREM. BET, and TGA. The results show that the carbon nanotubes were distributed uniformly on the surface of cordierite. A significant increase in BET surface area and pore volume was observed, and a suitable pore-size distribution was obtained. On the CNTs-cordierite, carbon nanotubes penetrated into the cordierite substrate, which led to a remarkable stability of the CNTs against ultrasound maltreatment. Growth time is an important factor for thermostability and texture of the sample. The mass increased but the purity decreased with the growth time, which caused the exothermic peak shift to low temperature, and the corresponding full width half maximum (FWHM) of the peak in DTG increased.     

多分支中性受体的合成及αω-二羧酸阴离子识别研究

Two new multi-armed neutral receptors 1 and 2 containing thiourea and amide groups were synthesized by simple steps in good yields. Receptors 1 and 2 have a better selectivity and higher association constants for malonate anion than other anions examined by the present work. In particular, distinct color changes were observed upon addition of dicarboxylate anions to the solution of 1 in DMSO. The UV-Vis and fluorescence spectra data indicate that a 1 ： 2 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of shorter carbon chain, and a 1 ： 1 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of longer carbon chain through hydrogen bonding interactions.