Effect of precursor preoxidation on the structure of phenolic resin-based activated carbon spheres

Activated carbon spheres with 3D hierarchical porous structure were prepared from phenol-formaldehyde resins with oxidation treatment in air and physical activation in an inert atmosphere. Based on the results of thermogravimetric analysis, infrared spectrometer (IR), scanning electron microscopy (SEM) and nitrogen adsorption/desorption, the effect of preoxidation on the morphology and structure of activated carbon spheres was investigated. The results show that decomposition and crosslinking reactions occur during the preoxidation and the structural changes of precursor generated by the preoxidation lead to differences in the pore structure of activated carbon spheres. The carbon spheres exhibit the unique 3D hierarchical porous structure, high specific surface area of 1897 m²/g and high pore volume of 2.22 cm³/g.     

Porous structure, permeability, and mechanical properties of polyolefin microporous films

Microporous films of polyolefins, namely, polyethylene and polypropylene, have been prepared using the process based on the extrusion of the melt with the subsequent annealing, uniaxial extension, and thermal fixation. The influence of the conditions used for preparation of the films on their morphology, porosity, number and sizes of through-flow channels, and mechanical properties has been investigated. It has been found that a significant influence on the characteristics of the porous structure of the films is exerted by the degree of orientation of the melt at extrusion, the annealing temperature, and the degree of uniaxial extension of the films. The threshold values of these parameters, at which through-flow channels are formed in the films, have been determined. It has been shown using filtration porosimetry that polyethylene films have a higher permeability to liquids as compared to the polypropylene samples (240 and 180 L/(m² h atm), respectively). The porous structure of the polyethylene films is characterized by larger sizes of through pores than those of the polypropylene samples (the average pore sizes are 210 and 160 nm, respectively), whereas the polypropylene films contain a larger number of through-flow channels.     

Morphology and Pore Size Distribution of Biocompatible Interconnected Porous Poly(L-lactic acid) Foams with Nanofibrous Structure Prepared by Thermally Induced Liquid–Liquid Phase Separation

Biocompatible, highly interconnected microporous poly(L-lactic acid) (PLLA) foams with nanofibrous structure, containing pores with average diameter below 1 μm and fibers with diameters of 10² nm scale, were prepared through the thermally induced liquid–liquid phase separation (TIPS) method consisting of quenching of the PLLA solution, freeze extraction with ethanol, and vacuum drying. Diverse foam morphologies were obtained by systematically changing parameters involved in the TIPS process, such as polymer concentration, solvent composition, and quenching temperatures. The morphology of different foams was examined by scanning electron microscopy to characterize the pore size and the pore size distribution. The results showed that most porous foams had a nanofibrous structure with interconnected open pores. In the case of using tetrahydrofuran (THF) as solvent, the higher the PLLA concentration, the smaller the average pore diameter and the narrower the pore size distribution. In the case of using the mixed solvents of THF/DOX (1,4-dioxane) with higher than 6/4 volume ratio, there appeared a maximum value of average pore diameter and a widest pore size distribution at 0.09 g/mL PLLA concentration. The average pore diameter of the foams increased with increasing DOX content in the mixed solvent and ranged from 0.2 to 0.9 μm depending on the process parameters. When the DOX content reached 60% by volume, the morphology of the foams contained some large closed pores with diameter ranging from 1 to 10 μm. By decreasing the quenching temperature, the average pore diameter of foams decreased and the pore size distribution became narrower. All the pore size distribution fit F-distribution equations.     

Morphology,Structure, and Crystallization of LaCl Modified Hollow Glass Microspheres/ Poly(vinylidenefluoride) Composites

Poly(vinylidene fluoride)/hollow glass microspheres (PVDF/HGMs) composites were prepared by using lanthanum chloride surface modified HGMs. The morphology, structure, and crystallization of the PVDF/HGMs composites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), respectively. The results showed that the interaction between the HGMs and the PVDF was improved by lanthanum chloride modification. The crystal structure of the PVDF was not changed by the HGMs, but the crystallinity was decreased. In addition, the Jeziorny and the Mo methods were used to analyze the non-isothermal crystallization kinetics. The results showed that the HGMs decreased the crystallization rates and extended the crystallization time of the PVDF.     

Synthesis,characterization, and electrochemical properties of lithium-based fluorosulfate nanoparticles as cathode for lithium-ion batteries

Lithium-based fluorosulfate nanoparticles were synthesized by a simple and fast solid state reaction from the precursors FeSO₄?7H₂O and LiF ground by high energy ball milling. Through the introduction of excess of LiF, relatively pure LiFeSO₄F phase with polycrystalline structure was obtained. The structure, morphology, and element valence state were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). The results demonstrate uniformly distributed particles and larger particles consisted of single crystalline structure, besides the valence states for different elements were analyzed and Fe²⁺ was confirmed. The cyclic voltammograms (CV) and charge-discharge cycling performances were employed to characterize electrochemical properties of prepared cathode material. It is very interesting that double redox peaks appeared reversibly. Meanwhile, it exhibited a relatively higher first-discharge capacity of 115 mAh/g at 0.05C and it still maintained above 60 mAh/g capacity after experiencing 30 times cycles at final 2C rate.     

Morphology and transmittance of porous alumina on glass substrate

The porous optical film has higher threshold of laser-induced damage than densified films, for the study of mechanism of laser-induced damage of porous optical film with ordered pore structure. Porous anodic alumina (PAA) film with high transmittance on glass substrate has been prepared. Aluminum film was deposited on glass substrate by means of resistance and electron beam heat (EBH) evaporation. Porous alumina was prepared in oxalic acid solution under different anodizing conditions. At normal incidence, the optical transmittance spectrum over 300-1000 nm spectra region was obtained by spectrophotometer. SEM was introduced to analysis the morphology of the porous alumina film. The pore aperture increased with the increase of anodizing voltage, which resulted in a rapid decrease of the pore concentration and the optical thickness of porous alumina film. Damage morphology of porous alumina film is found to be typically defects initiated, and the defect is the pore presented on the film.     

Structural and energetic heterogeneities of pyrocarbon/silica gel systems and their adsorption properties

Two series of pyrocarbon/silica gel (CS) samples were prepared using pyrolysis of different amounts of glucose adsorbed onto silica gel under dynamic conditions in a rotary reactor and a high-pressure autoclave. The structural characteristics and the morphology of the CS samples studied by means of the AFM, TG, nitrogen and p-nitrophenol (PNP) adsorption and quantum chemical methods depend not only on the amounts of pyrocarbon deposits but also on the synthesis methods, since the autoclave process gives a stronger effect of the pore wall hydrolysis by water formed on the carbonization of glucose. A displacement of the main peak of the pore size distribution of CS samples depends on pyrocarbon content. CS samples prepared in the autoclave possess larger microporosity and adsorb greater amounts of PNP in comparison with the samples synthesized in the rotary reactor.     

Synthesis,structure, and electrochemical properties of CdMoO<Subscript>4</Subscript> nanorods

In this paper, a novel nanocrystalline cadmium molybdate with nanorod morphology has been successfully prepared via hydrothermal method at relatively low temperature. The structure, composition, morphology of the prepared material was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectrometry (XPS), and transmission electron microscopy (TEM), respectively. The XRD data shows that the nanorods may have grown preferentially along the (001) axis. The diameters of these nanorods are within 30–50 nm in the TEM. The electrochemical intercalation of lithium into this compound and the cycling performance were first tested as the cathode material of lithium rechargeable battery. At the same time, the nanorod morphology presented here can also be helpful for the other property studies of CdMoO₄.     

Surface modification of PVDF membrane via AGET ATRP directly from the membrane surface

This contribution demonstrates a method for PVDF microporous membrane modification via surface-initiated activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly from the membrane surface. Three hydrophilic polymers, poly(2-(N,N-dimethylamino) ethyl methacrylate) (PDMAEMA), poly(2-oligo (ethylene glycol) monomethyl ether methacrylate) (POEGMA), and poly(2-hydroxyethyl methacrylate) (PHEMA), were grafted from the PVDF membrane surface in aqueous solution at room temperature. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the successful covalent tethering of the polymer chains onto the PVDF membrane surface. The gravimetry results indicated an approximately linear increase of the graft yields, up to about 330 μg/cm² for DMAEMA and 470 μg/cm² for both HEMA and OEGMA, with the polymerization time. Block copolymer brushes were prepared by chain extension. Water contact angle decreased over 50% for high yields, indicating improved surface hydrophilicity. The effects of the graft polymerization on membrane surface morphology, pore structure and permeability were investigated. It was found that the surface roughness was decreased and the pore size distribution was narrowed. The membrane permeability increased at low graft yields due to the enhanced hydrophilicity and decreased at high graft yields due to the overall reduction of the pore diameters.     

Preparation of activated carbons by microwave heating KOH activation

Activated carbons with high surface areas were prepared via KOH activation process by microwave (MW) heating. As a comparison, activated carbons were also prepared by conventional heating (EF) method. The influences of KOH/Mesocarbon microbeads (MCMB) weight ratio and activation time on the pore properties of the activated carbons were investigated. For both MW and EF heating methods, the surface area and pore volume increase to a maximum and then decrease with the KOH/MCMB ratio increasing. The effects of activation time on the pore properties depend on the KOH/MCMB ratio. The activated carbons prepared by MW heating have higher surface area and larger pore volume than those by EF heating when KOH/MCMB ratio is the same. The MW heating method shortens the activation time considerably. Activated carbons prepared by MW heating show low content of oxygen containing groups.     

Performance of C/C electric double layer capacitors with coal-based active carbon electrodes

Coal-based active carbon was prepared and used as electrodes of electric double-layer capacitors (EDLCs). The performance of EDLCs using active carbon electrodes with different pore structure was studied, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. With an increase of sodium hydrate/coal ratio, the pore structure of active carbon is greatly improved, resulting in larger double-layer capacitance. The capacitance of asymmetric EDLC is up to 65.98 F/g. Moreover, it is found that different pore structure of active carbon is necessary for positive and negative electrodes. Asymmetric EDLC not only exhibits high capacitance but also shows excellent charge-discharge performance, suggesting that it is very suitable and promising to design electrode materials for supercapacitors.     

Comparison of coating properties obtained by MAO on magnesium alloys in silicate and phytic acid electrolytes

Anodic coatings were prepared by using microarc oxidation (MAO) on AZ91HP in silicate containing solution (Si-solution) and phytic acid containing solution (P-solution), respectively. The influence of the electrolytes on coating structure, morphology and composition was studied by using X-ray diffraction (XRD), environmental scanning electron microscope (ESEM) and energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization test and immersion test were employed to evaluate the corrosion resistance of anodic coatings. Different electrolytes caused the differences in the MAO process and coating properties. The breakdown voltage and the final voltage in P-solution were higher than those in Si-solution. The pore uniformity of anodic coatings obtained in Si-solution (Si-film) was worse than that in P-solution (P-film). XRD analyses indicated that Si-film was amorphous, while P-film consisted of MgO. The corrosion resistance of the sample coated with P-film was better than that with Si-film.     

Gelatin/Montmorillonite and Gelatin/Polyvinyl Alcohol/Montmorillonite Bionanocomposite Hydrogels: Microstructural,Swelling and Drying Properties

Abstract

Gelatin/montmorillonite bionanocomposite hydrogels containing 0, 5 and 10?wt.% of montmorillonite were prepared via two different techniques, either a cooling or drying method. In addition, gelatin/polyvinyl alcohol/montmorillonite bionanocomposite hydrogels having gelatin/polyvinyl alcohol ratios of 1/1, 1/2 and 2/1, loaded with 0, 5 and 10?wt.% of montmorillonite, were prepared via a cyclic freezing-thawing technique. The microstructural properties of both types of the prepared bionanocomposite hydrogels were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The gel fraction, swelling behavior and drying kinetics of all prepared bionanocomposite hydrogels were also studied. The XRD and SEM results showed a porous structure with a possible exfoliated morphology for both types of the prepared bionanocomposite hydrogels. In addition, the gel fraction of the bionanocomposite hydrogels increased and a more entangled and crosslinked network with a decreased pore size was obtained by increasing the loading level of montmorillonite for both types of the bionanocomposite hydrogels. The swelling ratio and drying rate of both types of the bionanocomposite hydrogels could be increased by decreasing the PVA portion or MMT loading level, while the swelling and drying ability of the gelatin/montmorillonite bionanocomposite hydrogels prepared via the cooling method was higher than those of the corresponding samples prepared via the drying method.     

Fabrication of superhydrophobic silica-based surfaces with high transmittance by using tetraethoxysilane precursor and different polymeric species

The preparation of superhydrophobic silica-based surfaces via the sol-gel process through the addition of different polymeric species into the precursor solution was done in this study. The surface roughness of the films was obtained by removing the organic polymer at a high temperature, and then the hydrophobic groups were bonded onto the films with a monolayer by chemical reaction with hexamethyldisilazane (HMDS). The characteristic properties of the as-prepared films were analyzed by contact angle measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption, and UV-vis scanning spectrophotometer. The experimental results revealed that the superhydrophobic thin films with high transmittance could easily be prepared using polypropylene (PPG), polyethylene (PEG), and poly(vinylpyrrolidone) (PVP). Surface roughness and pore size were enhanced using PPG polymeric species. The distribution of pore size was from the microporous to the mesoporous and marcoporous regions. In addition, the contact angles of the rough surfaces prepared at 500 °C without modification of HMDS were smaller than 5° but larger than 156° after modified by HMDS.     

陶寺、殷墟白灰面的红外光谱研究

采用傅里叶变换红外光谱(FTIR)对天然石灰石、模拟白灰面以及采自陶寺遗址和殷墟遗址的白灰面进行了分析检测,以探明陶寺和殷墟遗址白灰面所用原料。结果显示,人工烧制石灰碳化后所形成的方解石,其ν₂/ν₄比值高达6.31,明显高于天然石灰石中的方解石,从而表明人工烧制石灰碳化所形成的方解石较之天然石灰石中的方解石具有较高的晶体无序度;随着研磨程度的增加,天然石灰石中的方解石和人工烧制石灰碳化形成的方解石,其ν₂和ν₄值逐渐减小,人工烧制石灰碳化形成方解石的ν₂-ν₄特征趋势线斜率较高,从而为考古出土人工烧制石灰的判定提供了一种简便、有效的方法。根据此判别方法,陶寺和殷墟遗址的白灰面很可能是采用人工烧制石灰所制备的,表明中国古代先民在距今4300多年的新石器时代晚期已掌握了石灰烧制技术。     

Template synthesis of well-aligned titanium dioxide nanotubes

TiO₂ nanotubes of the anatase form have been synthesized by sol-gel chemical method using anodic aluminum oxide (AAO) as a template. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction were used to investigate the structure and morphology of the TiO₂ nanotubes. The results showed that TiO₂ nanotubes obtained are highly ordered and uniform. The diameter and length of the obtained nanotubes were determined by the pore size and the thickness of AAO template. It was found that through control of immersion time of AAO membrane in sol, both tubules and fibrils can be prepared. PACS 61.46.+w     

Poly(vinylidene fluoride) membranes by an ultrasound assisted phase inversion method

Poly(vinylidene fluoride) (PVDF) membranes were prepared by an ultrasound assisted phase inversion process. The effect of ultrasonic intensity on the evolution of membrane morphology with and without the addition of pore former LiCl during precipitation process was comprehensively investigated. Besides the inter-diffusion between the solvent and nonsolvent, the ultrasonic cavitation was thought to have significant influences on phase inversion and the resultant membrane morphology. The mutual diffusion between water and solvent during the ultrasound assisted phase inversion process was measured. The crystalline structure was detected by wide angle X-ray diffractometer (WAXD). The thermal behavior was studied by differential scanning calorimeter (DSC). The mechanical strength, forward and reverse water flux, rejection to bovine serum albumin (BSA) and pepsin were also investigated. By the ultrasound assisted phase inversion method, ultra-filtration membrane was successfully prepared, which exhibited more preferable morphology, better mechanical property and more favorable permeability without sacrificing the rejection and thermal stability.     

真空冷冻干燥结合微乳液法制备纳米ZnO

真空冷冻干燥技术结合反相微乳液法制备了纳米ZnO粉体。利用XRD、TEM及表面积分析仪对制备过程、粉体的结构、形貌、比表面积、孔容进行了表征。探讨了煅烧温度、干燥方式及真空冷冻干燥的主要参数对纳米ZnO的影响。结果表明:该方法较常规方法制备的纳米ZnO粒径小(平均19nm)、分散性好、比表面积大(567.9m2.g-1),对亚甲基蓝溶液的降解(降解率98.6%)具有较高的光催化活性。     

Cationic starch as a precursor to prepare porous activated carbon for application in supercapacitor electrodes

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.     

Cr,Ag共掺杂ZnS纳米材料的制备及其对活性染料的吸附性能

通过水热法制备了纤锌矿ZnS∶Cr,Ag共掺杂纳米材料,考察了不同反应时间以及不同Cr和Ag掺杂比例对ZnS纳米材料光学性能的影响。分别采用荧光分光光度计、红外光谱仪、X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对Cr和Ag共掺杂ZnS纳米材料的光学性能和结构等进行了表征,探讨了ZnS∶Cr, Ag共掺杂纳米材料分别对甲基紫(MV)、丁基罗丹明B(BRB),四氯四溴荧光素(TCTBF)以及曙红B(EB)四种活性染料的吸附性能。结果表明,Cr3+和Ag+取代和嵌入到了Zn2+的位置,掺入到了ZnS的晶格中。由光学表征和扫描电镜(SEM)发现,掺杂后ZnS纳米材料的光学性能和形貌发生了改变。掺入Cr和Ag后,使得Zn纳米材料的荧光强度降低,且其形貌较规则,表面蓬松,呈绒球形状。当反应时间为12 h,Cr和Ag掺杂比例分别为1%时,掺杂ZnS纳米材料的形貌和光学性能最佳。运用N₂等温吸脱附分析技术计算了Cr和Ag共掺杂ZnS材料的比表面积和孔径分布,将其用于对MV,BRB,TCTBF以及EB四种活性染料的吸附研究,并分别从吸附时间、温度、pH值等因素考察了掺杂ZnS对几种活性染料吸附性能的影响,得出了Cr和Ag共掺杂ZnS材料在pH 7,室温下,分别经9,11,9和9 h吸附时间后对四种活性染料的吸附效果达到最佳。