Three-dimensionally ordered,ultrathin graphitic-carbon frameworks with cage-like mesoporosity for highly stable Li-S batteries

Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur (Li-S) batteries.The ability to engineer the porosity,wall thickness,and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries,such as fast capacity decay and poor high-rate performance.In this work,highly ordered,ultrathin mesoporous graphitic-carbon frameworks (MGFs) having unique cage-like mesoporosity,derived from self-assembled Fe3O4 nanoparticle superlattices,are demonstrated to be an excellent host for encapsulating sulfur.The resulting S@MGFs exhibit high specific capacity (1,446 mAh·g-1 at 0.15 C),good rate capability (430 mAh.g-1 at 6 C),and exceptional cycling stability (～0.049％ capacity decay per cycle at 1 C) when used as Li-S cathodes.The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs.In addition to the interconnected,ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport,the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides,leading to improved capacity retention even at high current densities.     

A simple method of preparing ordered and three-dimensionally-interconnected macroporous carbon with mesoporosity by using silica template

A simple and cost-effective method for the production of porous macro–meso structures is proposed. The approach involves using of monodispersed silica particles and in situ polymerized silica network as a removable template, and using resorcinol-sucrose derivative polymer as a carbon source. The three steps – carbon precursor, silica particles, template – are synthesized simultaneously through sol–gel reaction in one-pot system. The sample prepared by this method was characterized by scanning electron microscopy (SEM) and nitrogen adsorption and desorption, and the results present us a well long-ranged ordered structure and three-dimensionally interconnected macroporous carbon with mesoporosity.     

Highly crystalline WO3 thin films with ordered 3D mesoporosity and improved electrochromic performance

WO3 thin layers with nanometer-scale periodicity were prepared by evaporation-induced self-assembly (EISA) using a novel amphiphilic block-copolymer template (poly(ethylene-co-butylene)-block-poly(ethylene oxide)). The evolution of the mesoporous ordered network and the crystallinity of the framework were monitored by 2D-SAXS, WAXS, SEM, XPS, and porosimetry. By annealing the films, the pore-wall crystallinity is adjusted between fully amorphous and highly crystalline without mesostructural degradation. Thus, the crystalline-film framework is composed of phase-pure monoclinic WO3 nanoparticles (12-14 nm in size). Furthermore, heat treatment transforms the originally spherical mesopores into ellipsoids, resulting in a unidirectionally shrunken, but still well-defined and fully accessible bcc mesopore architecture. The influence of mesoporosity and crystallinity on electrochemical/electrochromic characteristics was addressed by monitoring electrochemical features and the absorption changes during Li insertion/extraction (repetitive potentiostatic cycling). Both the amorphous and crystalline mesoporous films possess electrochromic response times on the order of only seconds, which are attributable to the facilitated insertion of guest ions due to shortening of the diffusion path lengths. Also, the insertion/extraction reversibility of crystalline WO3 layers with 3D mesoporosity is improved compared to amorphous ones and reaches values close to 100%.     

胶体晶体模板法制备有序多孔堇青石材料研究

采用乳液聚合法制备了单分散P(St-AA)微球,经自然沉降法制成胶体晶体模板,再利用胶晶模板法制备了有序多孔堇青石.利用FTIR、SEM、DSC、XRD等方法对P(St-AA)微球单分散性及有序多孔堇青石结构进行了研究.结果表明,当AA用量占单体总量的5.0%时,制备的P(St-AA)微球的单分散性及其胶体晶体微球结构最佳.经烧结去除P(St-AA)微球得到的有序多孔堇青石材料的孔径较单分散P(St-AA)微球稍小,约为200nm左右.当烧结温度为1200℃,多孔材料为堇青石相.     

Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity

Zeolites are a family of crystalline aluminosilicate materials widely used as shape-selective catalysts, ion exchange materials, and adsorbents for organic compounds. In the present work, zeolites were synthesized by adding a rationally designed amphiphilic organosilane surfactant to conventional alkaline zeolite synthesis mixtures. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analyses show that the present method is suitable as a direct synthesis route to highly mesoporous zeolites. The mesopore diameters could be uniformly tailored, similar to ordered mesoporous silica with amorphous frameworks. The mesoporous zeolite exhibited a narrow, small-angle XRD peak, which is characteristic of the short-range correlation between mesopores, similar to disordered wormhole-like mesoporous materials. The XRD patterns and electron micrographs of the samples taken during crystallization clearly showed the evolution of the mesoporous structure concomitantly to the crystallization of zeolite frameworks. The synthesis of the crystalline aluminosilicate materials with tunable mesoporosity and strong acidity has potentially important technological implications for catalytic reactions of large molecules, whereas conventional mesoporous materials lack hydrothermal stability and acidity.     

1D nanofabrication with a micrometer-sized laser spot

A simple laser-assisted procedure for the fabrication of functional organic nanostructures is demonstrated. Native silicon samples are coated with alkylsiloxane monolayers and patterned with a focused beam of an Ar(+) laser (lambda = 514 nm). After patterning, the coating is chemically functionalized following a robust preparation scheme. Despite a laser spot diameter of about 2.5 mum, this routine allows for the fabrication of well-confined organosiloxane stripes with widths below 100 nm. As shown, these structures provide a versatile means for building ordered surface architectures of nanoscopic components. In particular, gold nanoparticles (d = 16 nm) self-assemble into one-dimensional arrangements, such as single chains.     

高中孔率活性炭的制备与表征

以线型酚醛树脂为碳源,通过形成钇-酚醛树脂配合物和水蒸气活化的方法制备了具有较高中孔率的活性炭.利用红外光谱(IR)、热重分析(TG)、氮气吸脱附曲线、扫描电镜(SEM)和X射线衍射(XRD)对所制钇-酚醛树脂配合物及相应活性炭进行了表征.结果表明:钇离子与嫁接了甲基丙烯酸甲酯的酚醛树脂之间形成钇-酚醛树脂配合物,其相应活性炭具有典型中孔炭的特征,且中孔率高达88%.钇-酚醛树脂配合物的形成,明显提高了钇元素的分散程度和钇元素的催化效率.同时,钇-酚醛树脂配合物的形成,有助于改善酚醛树脂基活性炭的孔结构和孔径分布,尤其对提高活性炭的中孔率有显著的作用.     

Preparation and optical property of anatase hollow microsphere with mesoporosity

Anatase hollow sphere with mesoporosity was prepared by sol pyrogenation used TiCl₄ as precursor only. The samples were characterized by X-ray diffraction and scan electron microscopy, their specific surface area was measured by N₂ adsorption. The results show that the sample calcined at 500 °C for 2 h is phase pure anatase, the morphology of the particle of the sample is hollow sphere, and the wall of the hollow sphere is constituted of anatase nanoparticle and mesoporosity. The crystallinity, the crystal size, the pore width, the specific surface area and the crystal phase of the sample are changing along with the calcined temperature. The optical property was measured by ultraviolet radiation vis absorption spectra of the suspension of the samples. The results show that the optical property of the sample is better than that of nanoanatase particle, and the optical property of hollow sphere titania with mesoporosity is related to its crystal phase, specific surface area, crystal size, porosity size and crystallinity.     

Growth of highly ordered colloidal photonic crystals using a modeling approach

Colloidal photonic crystals were grown using a vertical deposition method. The effect of colloidal concentration and deposition rate on crystalline quality and domain size was studied by means of response surface design. The crystalline quality was assessed using the optical reflectance. The results show that a strong negative correlation exists between the reflectance and the full width at half-maximum (FWHM), as illustrated by the close optimal region between maximizing reflectance and minimizing FWHM. For reflectance and FWHM, the quadratic effect of colloidal concentration is highly significant. For domain size, the colloidal concentration-lifting speed interaction effect was found to be significant. The observed colloidal concentration-lifting speed interaction effect explains the controversy that a low deposition rate is desirable at low colloidal concentrations, whereas a high deposition rate is favorable at high colloidal concentrations. Predictive models relating the important factors to the reflectance, FWHM, and domain size are proposed in the paper. The resulting optimal recipe shows a well-ordered structure with good optical reflectance, consistent with the prediction from modeling.     

Deformation of single crystals of the L21 ordered Ag2MgZn

The orientation and temperature dependence of slip geometry and yield stress in single crystals of the L2₁ ordered Ag₂MgZn has been studied in compression in the temperature range 290 to 580 K. The slip direction in Ag₂MgZn is exclusively 1 1 1 in this temperature range, but the slip plane varies with crystal orientations; slip occurs on (¯2 1 1) for orientations near the [0 1 1]-[¯1 1 1] boundary, while for the other orientations in the [0 0 1]-[0 1 1]-[¯1 1 1] unit triangle it occurs on the (¯1 0 1). The critical resolved shear stress (CRSS) for slip on both the (¯1 0 1) [1 1 1] and (¯2 1 1) [1 1 1] systems increases abnormally with increasing temperature and reaches a maximum peak at about 0.92 of the critical temperature T _c, for the L2₁-type order. The peak temperature and the shape of the CRSS versus temperature curve are independent not only of crystal orientation but also of the operative slip system. It is suggested that the strength anomaly in Ag₂MgZn be interpreted in terms of the mechanism based on the transition from unit dislocations to superdislocations.     

Synthesis and characterizations of three-dimensional ordered gold- nanoparticle-doped titanium dioxide photonic crystals

We developed a simple method to prepare gold-nanoparticle-doped titanium dioxide (GTD) sol-gel solution. The optimized GTD sol-gel solutions were a mixture of TEA, titanium (IV) butoxide, HAuCl₄, and deionized water in 0.3:1:0.5:3 volume ratios at room temperature. Using this sol-gel solution, we fabricated the GTD photonic crystal structure by infiltrating this solution by dip-coating into a polystyrene (PS) template. It was found that high quality of thin films was obtained by infiltrating twice the PS templates with the synthesized GTD sol-gel solutions. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectra revealed the doping of TiO₂ and Au in the GTD photonic crystals. X-ray diffraction showed that TiO₂ and Au existed as anatase phase and metallic Au phase, respectively, in the GTD photonic crystals. The results indicated that the gold nanoparticles were doped into the framework of the photonic crystals.     

Transition of MEMS technology to nanofabrication

The transition of MEMS technology to nano fabrication is a solution to the growing demand for smaller and high-density feature sizes in the nanometer scale. Nanoimprint lithography (NIL) techniques for fabricating micro- and nano-features are discussed including hot embossing lithography (HEL), UV Molding (UVM) and micro contact printing (microCP). Recent results in micro and nano-pattern transfer are presented where features ranged from < 100 nm to several centimeters. We also present a comparative study between standard glass microfluidic chips and their HEL counterparts by metrology. Hot-embossed microfluidic chips are shown to be faithful replicates of their parent stamps. NIL is presented as a promising avenue for low-cost, high throughput micro and nano-device fabrication.     

纳米制造和测量技术产业化的研究

从加工尺度的连续性和加工技术的完整性这一新的角度,分析了纳米加工产业化面临的问题,并提出了相应的解决方案一多离子柬聚焦投影技术。多离子柬聚焦投影技术将填补传统微机加工技术和半导体图形技术之间0．5～5μm的加工空白,并会在1～100nm尺度间实现自上至下技术和自下至上技术的有机结合。纳米测量技术产业化的研究中,以提高扫描探针技术的样品质量作为出发点。在聚焦离子束和扫描电镜平台上集成Ar离子束的“三束”显微镜能有效降低样品的损伤,大大推动了纳米测量技术的发展。     

Water intrusion-extrusion in silicalite-1 with tunable mesoporosity prepared in fluoride medium

Experimental water intrusion–extrusion isotherms were performed at room temperature on mesoporous silicalite-1 samples, prepared in fluoride medium and using carbon black or surfactant, [3-(trimethoxysilyl)propyl]hexadecyldimethylammonium chloride, as porogen and templating agents, respectively. The increase of the porous volume observed for the silicalite-1 sample prepared in the presence of carbon black leads to an increase of the water intruded volume at high pressure (100 MPa). Therefore, the amount of stored energy in this water–zeolite system is greater than for a conventional “water–silicalite-1” system. However, the fluoride route appears to be a less effective method than the alkaline route.     

Focused ion beam nanofabrication: a comparison with conventional processing techniques

Focused ion beam and dual platform systems are versatile tools for nanoengineering and nanoscience applications. These systems complement conventional processing methods and can be used to prototype and modify a diverse range of nano-devices and sensors. This article discusses FIB nanofabrication and compares it with other fabrication techniques such as electron beam lithography and reactive ion etching. Aspects such as the minimum feature size and side wall profiles are discussed and compared. In addition, the limitations and detrimental effects of FIB processes are discussed.     

Single-walled carbon nanotube network with bimodal pore structures of uniform microporosity and mesoporosity

We characterized single-walled carbon nanotubes before and after HNO3/H2SO4 treatments for different times by scanning electron microscopy, Raman spectroscopy, and N2 adsorption at 77 K. Single-walled carbon nanotube assembly revealed a bimodal pore structure of microporosity (surface area of 476 m2 g(-1)) and mesoporosity (surface area of 476 m2 g(-1)) with a high total surface area of 1048 m2g(-1). The microporosity increased prominently after HNO3/H2SO4 treatments, whereas the mesoporosity decreased progressively with the treatment time. The HNO3/H2SO4 treatment of nanotubes induced an aggregation and alignment that should transform larger mesopores of nanotube assemblies into smaller ones, and smaller mesopores into micropores, resulting in the decrease of external surface area. This effect was attributed to the presence of abundant defects on the tube wall that were saturated by functional groups during the acid treatment of the single-walled carbon nanotubes.     

Precise control of nanofabrication by atomic force microscopy

With an aim of the precise control of the anodic oxidation process by atomic force microscopy, the technical improvement has been carried out based on the mechanism studies. The accuracy and reliability of the nanofabrication have been improved by the combination of ambient humidity control, improvement of instrumental performance and meniscus lifetime control. In parallel, the mechanism study has been proceeded through the detection of Faradaic current. The in situ Faradaic current detection of the nano-oxidation process can actually work as a sensitive monitor for the nano-oxidation process with a high reliability. From an engineering viewpoint with an eye to practical applications, controllable physical parameters which affect on the product size are enumerated to consider what we should do to raise the precision of nano-oxidation. Then the fast fabrication in a large area by a patchwork method, Faradaic current detection during oxidation-reduction reaction, and nanofabrication by current-control are shown as examples.     

Rational design and nanofabrication of gecko-inspired fibrillar adhesives

Gecko feet integrate many intriguing functions such as strong adhesion, easy detachment, and self-cleaning. Mimicking gecko toe pad structure leads to the development of new types of fibrillar adhesives useful for various applications. In this Concept article, in addition to the design of adhesive mimics by replicating gecko geometric features, we show a new trend of rational design by adding other physical, chemical, and biological principles on to the geometric merits, for enhancing robustness, responsive control, and durability. Current challenges and future directions are highlighted in the design and nanofabrication of biomimetic fibrillar adhesives.