Charge transport processes in polypyrrole nanoscale composites

Polypyrrole molecular composites were prepared by in situ deposition in poly(ethylene oxide) complexes with copper chloride blended with polystyrene. The electrical conductivity of these materials showed some peculiar features such as anisotropy, sharp change with temperature and nonlinear I-V characteristics which were enhanced at a particular composition or certain deposition condition. These various results have been explained on the basis of phase-segregated morphology and a Poole-Frenkel type of conduction process, and are confirmed by detailed studies of the I-V characteristics.     

Conducting polypyrrole by chemical synthesis in water

Bulk quantities of polypyrrole (PP) can be obtained as fine powders using the oxidative polymerization of the monomer by selected transition metal ions in water. Short-term polymerization and low temperatures gave the best results as far as the electrical conductivity of the resulting PP powders is concerned.Positive effects on both conductivity and stability to aging were found when oxidations were carried out in the presence of selected organic compounds.     

Conducting polymer composites of polypyrrole and polyindene

Polypyrrole-polyindene composites were prepared via electrochemical methods. Two different approaches were utilized. In the first, the electro-initiated polymerization of indene on a platinum electrode was achieved at 2.0 V versus Ag/Ag⁺ in acetonitrile. Then the polyindene-coated electrode was used for the electrochemical polymerization of pyrrole at 1.0 V versus Ag/Ag⁺. In the second case, electrochemical coating of platinum electrode with polypyrrole at 1.0 V versus Ag/Ag⁺ was carried out and indene was polymerized on the conducting polymer at 2.0 V versus Ag/ Ag⁺ in acetonitrile medium. The characterizations of these composites were done by FT-IR, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). Electrical conductivities were evaluated by two-probe and four-probe methods.     

One-step fabrication of hierarchical polypyrrole microspheres with nanofibers as building blocks

Hierarchical polypyrrole microspheres, which have nanofibers as building blocks, the size of several microns and a conductivity of 0.8 S cm^?1, were prepared simply and directly via a one-step self-assembly approach in the presence of (NH₄)₂S₂O₈ (APS), cetyltrimethylammonium bromide (CTAB) and sulfonated polyaniline (SPANI). It was found that the formation probability of hierarchical polypyrrole microspheres depended on the (NH₄)₂S₂O₈/CTAB and SPANI/CTAB molar ratio. Bulk quantities of hierarchical polypyrrole microspheres can be obtained readily under the optimal conditions such as (NH₄)₂S₂O₈/CTAB molar ratio >2.8 and SPANI/CTAB molar ratio >4.7 × 10^?3. The precipitate [(CTA)₂S₂O₈] of CTAB and (NH₄)₂S₂O₈ was proposed to act as a “template” to promote the formation of PPY nanofibers, while the dopant SPANI was suggested to play a “rope-like” or “bridge-like” role in the subsequent self-assembly of nanofibers into PPY hierarchical microspheres. The experimental results and our investigation for the formation of PPY hierarchical microspheres may shed some light on preparing of other conductive hierarchically materials by proper molecular design and experimental condition optimization.     

Conducting organic polymers with electroactive dopants. Synthesis and electrochemical properties of hexacyanoferrate-doped polypyrrole

A systematic study of the synthesis of heacyanoferrate-doped polypyrrole (PPy/HCF) is reported. In addition to the electrochemical growth of films, we report three different modifications of a novel chemical synthesis for the preparation of bulk powdered materials by oxidative polymerization of pyrrole by the acid derivative of HCF. The effect of temperature and duration of the reaction, doping level and aging of the materials obtained on their conductivity has been systematically studied. Higher conductivities are obtained for materials prepared at lower temperatures (0°C). This is associated to a higher content of the doping HCF anion for these lower temperature materials. With time the conductivity of all samples decreases proportionally to the corresponding initial values. Finally, we report the electrochemical properties of these hybrid materials, the cyclic voltammograms of chemical and electrochemical derivatives and their intercalation behavior, which shows a deintercalation of the electroactive HCF anion in aqueous electrolytes but not in organic (propylene carbonate, dimethoxyethane) media.     

主从式数控系统中的数据通讯

本文针对一种由工业控制计算机和步进电机控制卡构成的主从式车床数控系统，介绍了该系统的通讯协议，并重点阐述了在Ｗｉｎｄｏｗｓ９５平台下工业控制计算机和步进电机驱动卡之间双向并行数据通讯的实现方法。     

Electrodeposited PEDOT films on ITO with a flower-like hierarchical structure

Poly(3,4-ethylenedioxythiophene) (PEDOT) films with a flower-like nanostructure have been electrochemically deposited on indium tin oxide (ITO) electrode simply by a one-step cyclic voltammetry (CV) method in an aqueous media in the absence of any surfactant. The PEDOT films deposited on the substrates were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results indicate that the flower-like hierarchical structure of the PEDOT film is composed of nanosheets with a thickness of even less than 2 nm at the edge. The resulted porous structure of the PEDOT coating leads to a two-order increase of magnitude in the electrochemical capacitance-current. The growth process of the electrodeposited PEDOT as well as the effect of polymerization potential on the properties of products was studied.     

Facile fabrication of nanoscale hierarchical porous zeolitic imidazolate frameworks for enhanced toluene adsorption capacity

The development of a simple and facile synthesis route is a highly desirable but challenging process in the fabrication of nanoscale hierarchical porous zeoliti...     

液相法制备超疏水ZnO微纳米阶层结构薄膜

利用简单的低温液相技术,通过氢氟酸(HF)调控反应溶液的pH值制备了具有微/纳米阶层结构的ZnO薄膜.对其接触角进行测量,结果表明该微纳米阶层结构不仅具有超疏水性,而且在真空紫外光照和暗窄保存的循环作用下具有超疏水/超亲水可逆转变的特征.对HF不同加入量的ZnO形貌观察表明,反应溶液中的H 和F-对ZnO的形貌均具有重要作用:H 主要抑制ZnO沿c轴方向生长,F-能够促使ZnO从"棒"状变为"花球"形,从而使ZnO具有微/纳米结构相结合的阶层结构.当HF的浓度比较低时,H 起主要作用;浓度比较高时,F-起主要作用.这种新颖的微纳米结构及其特异的润湿学特性,将有助于该薄膜在微流体器件上的应用.     

模板法-脱合金制备低密度、分级多孔金及其电催化性能

本文提出了以模板法-脱合金复合方法制备低密度分级多孔金。在该方法中,以直径为700 nm的二氧化（SiO2）微球作为模板,通过化学镀的方法依次制备了Ag@SiO2和Au@ Ag@ SiO2核壳粒子,并通过冷压-烧结方法制备了Au@ Ag@ SiO2合金块材。通过连续改变腐蚀溶液,SiO2模板以及Ag元素从Au@ Ag@ SiO2合金中完全去除。将SiO2从Au@ Ag@ SiO2微球完全去除从而得到了大尺寸空心球壳（直径约为675 nm）,将Ag元素脱合金去除从而在球壳表面形成了许多小尺寸的孔结构（直径约为75nm）。TEM图像表明,块状金样品中的韧带由具有多晶特性的纳米晶粒组成。这种具有低密度1.1 g/cm3（相对密度为5.7%）和高表面积4.24 m2/g的分级纳米多孔金材料在碱性溶液中对甲醇电氧化具有优良的催化活性以及快速的传质速率,表明其在催化领域具有广阔的应用前景。     

Study of lithium/polypyrrole secondary batteries with Lithium as cathode and polypyrrole anode

Lithium/polypyrrole (Li/PPy) batteries were fabricated using lithium sheet as cathode, PPy as anode, microporous membrane polypropylene/polyethylene/polypropylene (PP/PE/PP) composite as separator and LiPF6/ethylene carbonate-dimethyl carbonate-methyl ethyl carbonate (EC-DMC-EMC) as electrolyte. Polypyrrole was prepared by chemical polymerization. Certain fundamental electrochemical performances were investigated. Properties of the batteries were characterized and tested by SEM, galvanostatic charge/discharge tests, cyclic voltammetry (CV), and a.c. impedance spectroscopy. The influences of separator, morphology, and conductivity of PPy anode, cold-molded pressure, and electric current on the performances of the batteries were studied. Using PP/PE/PP membranes as separator, the battery showed good storage stability and cycling property. The conductivity of materials rather than morphology affected the behavior of the battery. The higher the conductivity, the better performances the cells had. Proper cold-molded pressure 20 MPa of the anode pellet would make the properties of the cells good and the fitted charge/discharge current was 0.1 mA. The cells showed excellent performance with 97%-100% coulombic efficiency. The highest discharge capacity of 95.2 mAh/g was obtained.     

Preparation of polypyrrole film with well-ordered corrugation

Polypyrrole (PPy) films with well-ordered corrugations were produced using the following three-step procedure. First, an elastic silicone sheet was stretched by 20% and fixed on a frame. Second, it was coated with gold using an ion sputtering technique. In this step, the gold coating spontaneously corrugated. Finally, PPy was synthesized by an electrochemical reaction on the gold coating that was used as the electrode. The obtained PPy film was corrugated because the corrugated gold coating worked as a template. The wavelength of the controlled corrugation ranged from 7.3 to 41.0 μm by controlling the thickness of the gold coating from 10 to 100 nm.     

Microstructure and texture evolution during annealing a cryogenic-SPD processed Al-alloy with a nanoscale lamellar HAGB grain structure

The grain structure and texture evolution during annealing a Al–0.13% Mg submicron-grained alloy, deformed by plane-strain compression (PSC) at cryogenic temperatures, has been investigated by transmission electron microscopy and electron backscatter diffraction. After deformation the alloy contained a lamellar grain structure with a high-angle grain boundary (HAGB) spacing of 190 nm and an area fraction of ～80%. On annealing the grain structure coarsened and transformed from lamellar to equiaxed. Remarkably, the fraction of low-angle grain boundaries (LAGBs) progressively increased during annealing, to ～50% above 300 °C, leading to instability and discontinuous recrystallization at higher temperatures. This resulted in a “bimodal grain structure” comprised of bands of coarser grains and fine subgrains, arising as a result of the increase in proportion of lower-mobility LAGBs. The surprisingly large increase in LAGB fraction on annealing is shown to be related to orientation impingement, originating from the strong texture present after PSC in liquid nitrogen.     

Electrochemical studies of polypyrrole doped with ferrocyanide anions

Thin films of polypyrrole-ferrocyanide have been characterized using a rotating ring-disk electrode. It has been shown that the total amount of ferrocyanide is removed from the system in the first reduction-oxidation cycle if an appropriately low potential is applied during polypyrrole polymerization. If the polymerization potential reaches higher values than 0.6 V versus SCE in aqueous solutions, a significant irreversibility of the redox reaction results, leading in turn to the existence of non-removable anions in the polymer film. The linear relationship between the amount of released dopant registered at the ring and the film thickness indicates a homogeneous distribution of the dopant within the polypyrrole matrix.     

The effect of polypyrrole coatings on the adhesion and structure properties of UHMWPE fiber

To improve the adhesion between ultrahigh molecular weight polyethylene (UHMWPE) fiber and polymer matrix, pyrrole is oxidatively polymerized on the UHMWPE fiber surface continuously. The micro-composite of polypyrrole (PPy)-coated fiber/epoxy was prepared and the fiber was studied by interfacial shear strength (IFSS) through a single fiber pull-out method. Compared with the UHMWPE fiber as-received, the mean value of IFSS between PPy-coated UHMWPE and epoxy increased from 1.06 MPa to 5.72 MPa. In addition, the surface morphology and structure of PPy-coated UHMWPE fiber were studied by SEM, FT-IR, DSC and DMA. The results showed that PPy-coated UHMWPE fiber surface was observed with some particles attached. Although there is no chemical interaction between PPy and UHMWPE chains, PPy has some interaction with UHMWPE molecular chains according to the results of DMA. The PPy coatings have an effect on the adhesion may be associated with the roughened surface of the fiber and upon intermolecular interaction.     

CO sensor based on polypyrrole functionalized with iron porphyrin

Polypyrrole (PPy) was chemically functionalized with 5,10,15,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride (FeTPPCl) with special interest on noxious carbon monoxide (CO) gas in ppm level. Controlled functionalization of PPy was achieved with incorporation of various concentrations of porphyrin. The resulted semiconducting material was well characterized by different techniques such as UV–vis spectroscopy, FTIR, GFAAS, XRD, and EDAX. The functionalized polypyrrole material on interdigitated electrode was experienced an immediate increase in resistance when exposed to carbon monoxide gas at very low concentration. The CO gas interacted very fast with the FeTPPCl functionalized PPy at room temperature (RT) and then slowly saturated. The response of these materials was not unidirectional, but reverses to the original resistance level when CO was removed from the test chamber. The highest response factor (ΔR/R₀ × 100) and lowest response time (t₅₀) obtained are 12 and 169 s, respectively. An optimum level of doping (1 mol% of FeTPPCl) was established for the highest sensitivity and the detection level is as low as 100 ppm.     

SPS制备多级孔结构钨骨架压缩性能及致密化行为研究

以粒径分布为15～106μm多孔球形团聚W粉为原料,采用放电等离子体烧结(SPS)在不同烧结温度(1450、1500、1550℃),轴向恒压40 MPa,保温5 min下分别制备出高强度(347.8±10.6 MPa、407.4±14.2 MPa、543.9±8.7 MPa)、多级孔结构(3～10μm/200～500 nm)W骨架。结合XRD、SEM、万能试验机等检测技术,对SPS烧结过程中粉末致密化行为、显微组织变化及力学性能进行了系统研究。结果表明:SPS可制得烧结前后物相无明显变化、孔隙率介于30%～40%、烧结颈发育完全多级孔结构钨骨架。该多级孔W骨架SPS烧结致密化过程可分为4个阶段,第1阶段为升压阶段,烧结试样相对密度随压力升高而迅速升高;第2阶段为典型的颗粒重排阶段;第3阶段烧结温度高于1000℃,烧结试样相对密度随温度的升高而增加,属于典型的烧结中期;第4阶段为烧结末期,烧结体内部高温蠕变引起致密化程度进一步提高。利用高温蠕变模型研究了该多孔球形W粉的致密化机理为纯扩散致密化,通过颈长方程确定该多孔球形钨粉在整个SPS烧结过程中的致密化机理是以体积扩散为主,晶界扩散为辅。     

Hydrogen evolution on microstructured polypyrrole films modified with nickel

Enhancement of electrocatalytic activity of polypyrrole (PPy) for hydrogen evolution reaction (HER) has been carried out by the deposition of Ni layer of different thickness. By formation of three-dimensional microcontainers on the PPy surface an increase in surface area of the PPy/Ni catalytic layer could be obtained, providing an increased overall electrocatalytic activity. The PPy/Ni layers offer a significantly higher electrocatalytic activity in the HER than PPy or Ni electrode. The best catalytic activity was detected for composite PPy/Ni electrodes produced by electrodeposition of Ni on pre-deposited microstructured PPy substrate in 2 cycles.