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The gas adsorption/desorption reaction that occurs on a solid surface forms the basic reaction of various catalysts and sensor devices.

In this study, the microwave, i.e. 0.5–10 GHz, transmission characteristics of carbon nanofiber (CNF) with three different micrometer-scale thicknesses were experimentally investigated using a coplanar waveguide transmission line. In the experimental results, when the film of CNF was thick, the signal transmission level (S21-magnitude) was significantly lower and its phase (S21-phase) was shifted toward the low-frequency region. Based on the obtained S21-parameter (S21-magnitude and S21-phase), the electric permittivity (e) of CNF was extracted and showed clear differences depending on the thickness, i.e., ethin = 1.20 (0.28), emiddle = 1.84 (0.60), ethick = 6.30 (1.15) at 0.5 GHz (7.8 GHz). From the analysis of electromagnetic fields, the microwave conductivity (σmw) of CNF linearly increased with the increasing thickness, i.e., σmw/thin = 0.35 (S/m), σmw/middle = 0.58 (S/m), σmw/thick = 0.75 (S/m), due to enhanced electromagnetic field coupling between the film of CNF and the CPW line. As a result, we demonstrated that the film of CNF has a significant attenuation effect on signal transmission in the microwave regime, depending on micrometer-scale changes in film thickness.

The aim of this study is to develop the templateless fabrication of hierarchical porous carbon nanofiber (CNF)/MnO2 composites (PMnCD) derived from polyacrylonitrile (PAN)/cyclodextrin (CD) and investigate their morphological and electrochemical properties to determine the different capabilities of inclusion complexes (ICs) formed by α-CD, β-CD and γ-CD. Among the three CD phases, the PMnCD(β) composite using β-CD exhibits a hierarchical porous structure with large specific surface area of 499 m2g-1, and total pore volume of 0.32 cm3g-1, which helps with adsorption efficiency and accumulation of hydrated molecules for double-layer formation. In addition, the numerous mesopores and nitrogen functionalities of the PMnCD(β) composite provide fast diffusion channels for electrolyte ions and higher attractive interactions with electrolyte ions through the pseudocapacitive character. As a result, the PMnCD(β) electrode has a high specific capacitance of 228 Fg-1 at 1 mAcm−2, maximum energy density of 25.3–16.0 Whkg−1 in the power density range of 400-10,000 Wkg-1, and excellent cycling stability of more than 94% after 10000 cycles in aqueous solution, thereby offering potential applications for supercapacitors.

To develop economical and high-performance supercapacitor electrodes in an aqueous electrolyte, polyacrylonitrile (PAN)/pitch/lignin-based carbon nanofibers (CNFs) with ZnO (PPL-Zn) are successfully fabricated by one-step electrospinning of PAN, pitch, lignin, and zinc acetate. The oxygen-rich lignin in the PPL-Zn electrodes induces porosity on the fiber surface by eliminating many functional groups such carboxylic, carbonyl, hydroxyl and ketone and organic moieties in the simple heat treatment without any activation agent/activation process. Moreover, the many aromatic components, high carbon content, and low glass transition temperature of lignin are excellent precursors to CNF composites. In addition to lignin, pitch is used as a precursor to CNF to reduce the cost and increase the carbon yield and electrical conductivity of the CNFs. These characteristics afford PPL-Zn(5) (5 wt% of zinc acetate relative to PAN and lignin) with good capacitive behavior for application as supercapacitor electrodes with a maximum specific capacitance of 165 Fg-1 at 1 mAcm−2 with a capacitance retention of 88%, high energy densities of 22–18 Whkg−1 in the power density range of 400 to 10,000 Wkg-1, and excellent cycling performance reduced by only ∼6% after 3000 cycles of charge/discharge due to the synergistic effect of the electrical double layer and the pseudocapacitive effect.

Carbon nanofibers (CNFs) with controllable pore sizes are fabricated by a simple electrospinning method with the help of boron trioxide (B2O3), and their electrochemical properties as electrodes are investigated in aqueous electrolyte. The optimized result is obtained with a B2O3 concentration of 10 wt% in a spinning solution, offering a large specific surface area of 1065 m2/g with a mesopore volume fraction up to 35%, pore size range of 2–3 and 20–50 nm, and many heteroatoms. The CNF composite with 10 wt% B2O3 concentration (PMB-10) shows a high gravimetric capacitance of 126.31 F/g with a capacitance retention of 84%, and a high energy density of 12–18 W h/kg in the power density range of 400–10,000 W/kg. Thus, the porous structures and heteroatom contents of the PMB composites can be controlled by varying the B2O3 content as the pore expanding agent, as well as heteroatom generator, to optimize the electrochemical performance in an aqueous electrolyte.

Activated carbon nanofibers (ACNFs) containing oxygen, nitrogen, and silicon are prepared from polyacrylonitrile (PAN) and phenylsilane (PS) by simple electrospinning. The PS introduction into a PAN solution causes a porous structure with functional groups by spontaneous sol-gel reaction without any catalyst of PS in the physical activation process. PS-ACNF electrode shows the highest specific capacitance, 200 F/g, and the highest energy density, 25.6–119.19 W h/kg in the range of 400-10 000 W/kg in a 6 M KOH aqueous solution. Our results suggest that the porosity and functional groups of the supercapacitor electrodes have a strong impact on the enhanced electrochemical properties, resulting from an increased electroactive surface area.

Hierarchically structured carbon nanofiber/graphene/MnO2(CGMn) hybrid with oxygen and nitrogen functionalities was fabricated in the form of a web via electrospinning as an electrode material for supercapacitors. The CGMn electrode exhibited a high capacitance (225 Fg−1 at 1 mAcm−2), enhanced energy and power efficiency (15.8–13.6 Whkg−1 in the power density range of 197–4000 Wkg−1), and excellent capacitance retention (13% of the initial value at a discharge current of 20 mAcm−2) in a 6 M KOH aqueous electrolyte, because of the combination of the double-layer capacitance and the pseudocapacitive character associated with the surface redox-type reactions. The porosity and the number of heteroatoms of the CGMn composite were adjusted by changing the PMMA concentration and carbonization temperature. Therefore, the oxygen- and nitrogen-containing hierarchical porous CGMn hybrid prepared by a simple method is a promising candidate as an electrode material for supercapacitors.

Electrochemical capacitors based on hierarchical porous activated carbon nanofiber (RuO2 /ACNF) composites are fabricated by one-step electrospinning, and then stabilized at different activation temperatures. The effect of the activation temperature on the structural properties and electrochemical behavior of the RuO2 /ACNF composites is intensively investigated in 6 M KOH electrolyte. The RuO2 /ACNF-800 composites activated at high temperature possess abundant mesopores and larger pores, which improve the electrochemical performance, especially at high charge–discharge rates. The energy storage capabilities of the RuO2 /ACNF-800 electrode prepared at high temperature are as follows: a maximum specific capacitance of 150 F/g and an energy density of 14–20 Wh/kg in the respective power density range of 400 to 10 000 W/kg in an aqueous solution. Furthermore, this electrode exhibits high-rate electrochemical performance with a specific capacitance reduction of less than 28% of the initial value at a discharge current of 20 mA/cm2. Therefore, the hierarchical porous RuO2 /ACNF composites with well-developed mesoporous structure provide low resistance for charge diffusion and a short pathway for ion transportation, yielding good capacitive behavior.

The hybridization of carbon nano-materials enhances the efficiency of each function of the resulting structure or composites. Also, the addition of non-carbon elements to nanomaterials modifies the electrochemical properties. Electrodes combining po-rous carbon nanofibers (CNFs) and metal oxides benefit from the combination of the double-layer capacitance of the CNFs and the pseudocapacitive character associated with the surface redox-type reactions. Consequently, they demonstrate superior supercapacitor performance in terms of high capacitance, high energy/power efficiency and high rate capability. This paper presents a comprehensive review of the latest advances made in the development and application of various metal oxide/CNF composites (CNFCs) to supercapacitor electrodes. Keywords : Electrospinning, Carbon nanofiber composite, Metal oxide, Supercapacitor 1. Introduction 1) The increasing demand for clean energy and the growing concern re-garding air pollution and global warming have stimulated intense re-search into energy storage and conversion from alternative energy sources[1-4]. For this reason, electrochemical capacitors (ECs) are con-sidered promising power sources for portable electronic systems and automotive applications, because of their practical applications as high power devices owing to their large capacitance, long cycling life, and lack of toxic materials[5-9]. To obtain satisfactory performance, ECs must display high electrical conductivity, high surface area for optimal charge accumulation, sufficient pore diameter and good pore con

Transmission electron microscopy (TEM) is one of the highest resolution analysis methods of materials. The three dimensional recognition of the materials is difficult by TEM because the observation data is projection images through the materials. In this study, space structure of carbon nanotubes loaded with metal particles was analyzed by three dimensional TEM (3D-TEM) [1] , [2] . The nano structured carbons are also observed by high resolution transmission electron microscopy (HRTEM) with Cs corrector. Cup-stack type carbon nanotubes (CSCNTs) loaded with Pt particles (2–3 nm in diameter) prepared by GSI Creos Corporation were analyzed by these methods. Pt particles are bound selectively to the edges of hexagonal carbon layers of inside and outer surface of CSCNTs efficiently and can be expected to work well as catalysts of electrodes of fuel cell. It is sometimes difficult that the nano sized area is analyzed by selected area electron diffraction (SAD) because the selected area aperture cannot be so small. The HRTEM and image processing technique give similar results of SAD when it works and revealed to be useful to analyze nano structured carbons.

The generation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been facilitated by the addition of sodium tetrachloroaurate or gold(Ill) chloride (< 1 wt% of NaAuCl4 or AuCl3) to the reaction of silver nitrate (AgNO3) with bis(o-phenolpropyl)silicone [BPPS, (o-phenolpropyl)2(SiMe2O)n, n = 2,3,8,236]. TEM and FE-SEM data showed that the silver nanoparticles having the size of < 20 nm are well dispersed throughout the BPPS silicone matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The size of silver nanoparticles augmented with increasing the relative molar concentration of AgNO3 added with respect to BPPS. The addition of gold complexes (1-3 wt%) did not affect the size distribution of silver nanoparticles appreciably. In the absence of BPPS, the macroscopic precipitation of silver by agglomeration, indicating that BPPS is necessary to stabilize the silver nanoparticles surrounded by coordination.

Combinative one-pot Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), mediated by a mixture of AgNO3-AuCl3 (100/1 mole ratio) rapidly produced poly(alkoxysilane)s in reasonably high yield. The addition of small amount of gold complex to the reaction mixture effectively accelerated the coupling reaction compared to the reaction rate with AgNO3 alone. The hydrosilanes include p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols include MeOH, EtOH, iPrOH, PhOH, and CF3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600-8,000 Dalton and 1.4-3.5, respectively. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the Ag-Au complexes gave only triethoxyphenylsilane.

Graphene/carbon composite nanofibers (CCNFs) with attached TiO2 nanoparticles (TiO2–CCNF) were prepared, and their photocatalytic degradation ability under visible light irradiation was assessed. They were characterized using scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible diffuse spectroscopy. The results suggest that the presence of graphene embedded in the composite fibers prevents TiO2 particle agglomeration and aids the uniform dispersion of TiO2 on the fibers. In the photodegradation of methylene blue, a significant increase in the reaction rate was observed with TiO2–CCNF materials under visible light. This increase is due to the high migration efficiency of photoinduced electrons and the inhibition of charge–carrier recombination due to the electronic interaction between TiO2 and graphene. The TiO2–CCNF materials could be used for multiple degradation cycles without a decrease in photocatalytic activity.

Codehydrocoupling (in the presence of various inorganic B, Al-hydrides) followed by borane-capping (with Ph2BCl) of 1,1-dihydrotetraphenylsilole (1) and 1,1-dihydrotetraphenylgermole (2) (9:1 mole ratio) gave electroluminescent poly(silole-co-germole)s containing borane-ends (3) in high yield. The polymerization yield and molecular weight with Selectrides increase in the order L-Selectride < N-Selectride

The one-pot synthesis and characterization of silver nanoparticle-poly(p-Br-phenylsilane) composites have been carried out. The conversion of silver(+1) salt to stable silver(0) nanoparticles is promoted by poly(p-Br-phenylsilane), Br-PPS possessing both possible reactive Si-H bonds in the polymer backbone and C-Br bonds in the substituents. The composites were characterized using XRD, TEM, FE-SEM, and solid-state UV-vis analytical techniques. TEM and FE-SEM data show the formation of the composites where large number of silver nanoparticles (less than 30 nm of size) are well dispersed throughout the Br-PPS matrix. XRD patterns are consistent with that for fcc-typed silver. The elemental analysis for Br atom and the polymer solubility confirm that the cleavage of C-Br bond and the Si-Br dative bonding were not occurred appreciably at ambient temperature. Nonetheless, TGA data suggest that some sort of cross-linking was occurred at high temperature. The size and processability of such nanoparticles depend on the ratio of metal to Br-PPS. In the absence of Br-PPS, most of the silver particles undergo macroscopic aggregation, which indicates that the polysilane is necessary for stabilizing the silver nanoparticles.

The formation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been promoted by the addition of chloroplatinic acid (

To improve the anti-oxidation properties of carbon fibers (CFs), the sol-gel method followed by pyrolysis was used to coat CFs with SiC/SiO2 ceramic coatings. The SiO2 sol-gel coating was performed by dip coating a PAN(polyacrylonitrile)-based stabilized fiber (PSF) in a silica sol prepared by the polycondensation of tetraethylorthosilicate (TEOS) in the presence of an acidic catalyst. The PSF coated with SiO2 sol then underwent heat treatments at high temperatures in an inert atmosphere to deposit the SiC/SiO2 and carbonize the deposited fibers. The surface morphology of the CFs deposited with SiC/SiO2 was characterized using a scanning electron microscope (SEM). The relative oxidation resistance of the SiC/SiO2 layer deposited on the CFs was determined by the weight loss due to the use of a thermogravimetric analyzer (TGA) under flowing air, and the data were used to calculate the activation energies through an Arrhenius plot.

The electron beam (EB) irradiation effects of TiO2 deposited on carbon nanofibers (CNFs) were studied aiming the improvement of the photocatalytic activity. The EB irradiation contributed to an increase in crystallinity of the anatase resulting an improvement of the photocatalytic activity through the oxidation (ionization) of the doped TiO2 and leading to uniform distribution TiO2 particles on the CNFs surface. The photoactivity of the catalyst was measured by the decoloration of the methylene blue (MB) with time under UV irradiation.

The SiC/SiO 2 deposition was performed to improve the oxidation resistive properties of carbon nanofiber (CNF) from electrospinning at elevated temperatures through sol–gel process. The stabilized polyacrylonitrile (PAN) fibers were coated with SiO 2 followed by heat treatment up to 1000 and 1400 °C in an inert argon atmosphere. The chemical compositions of the CNFs surface heat-treated were characterized as C, Si and O existing as SiC and SiO 2 compounds on the surface. The uniform and continuous coating improved the oxidation resistance of the carbon nanofibers. The residual weight of the composite was 70–80% and mixture of SiC, SiO 2 and some residual carbon after exposure to air at 1000 °C.

Polyacrylonitrile (PAN)-based nanocomposite fibers were prepared by co-precipitation of different amounts of Fe(II) and Fe(III) in an alkaline medium to get iron oxide impregnated nanofibers. Nanofibers web were prepared from blend solution of PAN containing different concentrations (1, 2 and 3 wt%) of ferrous (Fe2+)/ferric (Fe3+) solution in the 1:2 molar ratio in an effort to further improvement of the porosity and thereby, electrical properties. Electrospun fibers containing various concentrations of iron salts were then treated with KOH solution to produce nanosized magnetite particles in situ within the PAN nanofibers by precipitating Fe2+ ions or mixture of Fe2+ and Fe3+ ions. Such nanoscale particles homogeneously dispersed in PAN nanofibers to form the three-dimensional network structure. The homogeneously dispersed nanoparticles of iron oxide in and on the PAN carbon nanofibers produced the network structure of reasonably well-aligned configuration. Composite nanofibers morphologies and surface properties were discussed utilizing the combined techniques viz., field emission scanning electron microscope (FE-SEM), particle size analyzer, surface area and pore size distribution measurements.

Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), catalyzed by group VIII metallocenes Cp2M' (M' = Co, Ni) which converted to Co(O)/nickel(O) colloidal nanoparticles, produced poly(alkoxysilane)s in one-pot in high yield. The hydrosilanes include p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols include MeOH, EtOH, 'PrOH, PhOH, and CF3(CF2)2CH2OH. The weight average molecular weight of the poly(alkoxysilane)s were in the range of 600 to 8100. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the nanocolloid catalyst gave only triethoxyphenylsilane as product.

Pt nanoparticle-doped titanium dioxide (Pt/TiO2) thin films were prepared on a silicon wafer substrate by sol-gel spin coating process. The prepared thin films were treated with electron beam (EB at 1.1 MeV, 100, 200, 300 kGy) at air atmosphere. The effect of EB-irradiation on the composition of the treated thin films, optical properties and morphology of thin films were investigated by various analytical techniques such as X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The crystal structure of the TiO2 layer was found to be an anatase phase and the size of TiO2 particles was determined to be about 13 nm. Pt nanoparticles with diameter of 5 nm were observed on surface of the films. A new layer (presumed to be Pt-Ti complex and/or PtO2 compound) was created in the Pt/TiO2 thin film treated with EB (300 kGy). The transmittance of thin film decreased with EB treatment whereas the refractive index increased.

TiO2/SiO2 catalysts were loaded on carbon nanofibers (CNF) support by sol-gel preparation and followed by a dip-coating and heat treatment up to 900 degrees C in inert atmosphere. The photocatalytic activities of the catalysts (TiO2/SiO2)/CNF were tested by the photocatalytic degradation rate of methylene blue (MB) under UV irradiation. It was found that (TiO2/SiO2)/CNF showed a higher photocatalytic activity than TiO2/CNF only. It was analyzed that SiO2 contributed to an increase the photo catalytic activity by suppressing the phase transformation of the TiO2 crystals from anatase to rutile on the heat treatment up to 900 degrees C.

Optimum process conditions were investigated for maximizing the mechanical properties of the carbon fiber by from wet spun polyacrylonitrile (PAN) fiber precursors. The process variables chosen were treatment temperature, applied tension in stabilization process. The temperature profile of the stabilization was set on the basis of exothermic peaks of the differential scanning calorimetry (DSC) result. Both tensile strength and modulus increased with holding at onset temperatures of the exothermic peaks for extended duration, and with a higher heating rate up to the onset temperatures at a given applied tension among the experimental conditions. The increase in load monotonously increased the tensile modulus, on the other hand, the tensile strength was maximum at the load of 15 mg/filament (T15). The load 20 mg/ filament (T20) was considered to be exceeded to form oriented crystal line structure, possibly introducing more defects in the fiber than under load of T15. The sample CP3-T15 O5 H30 showed the best tensile properties among the samples experimented whose tensile properties are compatible with the commercialized grade of general purpose carbon fibers even at low carbonization temperature such as 800 °C (the carbonization temperature in the commercial process. 1300∼1500 °C).

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. Activated carbon fibers (ACFs) derived by stabilization, carbonization and steam activation at 700, 800, and 900 °C of the PAN/pitch electrospun fibers for 60 min were investigated as electrodes for supercapacitors. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m 2 g -1 and the specific capacitance from 75.5 to 143.5 Fg -1 , depending on the activation conditions. Electrodes from the electrospun web activated at 900 °C exhibited a particularly quick response showing a high frequency of 5.5 Hz at a phase angle of-45° of the impedance spectroscopy.

The effect of high pressure radio frequency (RF) plasma treatment on TiO2 surface and photocatalytic property has been investigated. X-ray photoelectron spectroscopy (XPS) measurements have shown the two different oxidation states of oxygen in the untreated TiO2 powder. Its relative proportion changes with the different dose of plasma treatments. The proportion of Ti3+ surface states also changes after plasma treatment and strongly depends on combination of plasma power and treatment time. The photocatalytic activity of plasma-untreated and -treated samples was measured by observing the relative degradation of methylene blue. The result showed about 50% increase in photoactivity at the sample treated with 10 W RF power plasma. Low power plasma treatment is a more efficient process for achieving a photoactive surface. The effect of total dose (power and treatment time) and power has been also studied to modify the surface activity of TiO2 nanoparticles.

The dry sol–gel polycondensation at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to silica p-X-C6H4SiO1.5 in high yield, catalyzed by colloidal nickel nanoparticles in-situ generated from nickelocene(II), nickel(II) acetate, and bis(1,5-cyclooctadiene)nickel(0), is described. Similar catalytic activities were observed for the catalysts. Similarly, the dry sol–gel polyco-condensation p-X-C6H4SiH3 (X = CH3, CH3O, F, Cl):C6H4SiH3 (9:1 mole ratio) at toluene in ambient air atmosphere of was performed to yield co-silicas (p-X-C6H4SiO1.5)9(p-X-C6H4SiO1.5)1 in high yield using nickelocene. The co-gels with higher molecular weights and TGA residue yield were obtained when compared to the homogels. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si—H bonds still remained in the gel matrix because of steric bulkiness. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol–gel reaction was suggested.

The combinative Si–Si/Si–O dehydrocoupling at ambient air atmosphere of 1,1-dihydrotetraphenylsilole 1 with 2 mol% of AgNO3 and Ag2 SO4 in toluene at 90 °C produces optoelectronic polysiloles 2 in high yield. The complexes such as Cp2Co, Cp2Ni, Cp2ZrCl2/Red-Al, and AgCl were found to be ineffective for the dehydrocoupling of 1. The polysiloles mainly have Si—Si bonds along with the small portion of Si—O bonds in the polymer backbone chain. Interestingly, the Si–O linkage increased with increasing the concentration of catalyst AgNO3, implying that while Ag(0) species catalyze the Si–Si dehydrocoupling, Ag(I) species catalyze the Si–O dehydrocoupling along with the simultaneous oxidation of NO3− ion to NO2. The silver complexes transformed to colloidal silver nanoparticles during the catalytic reaction. The Si–Si/Si–O dehydrocoupling of 1 with AgNO3 even at dry nitrogen atmosphere is occurred, supporting that the oxidation of NO3− ion to NO2 is only the possible oxygen source, but not from the adventitious moisture in air. α-, β-, and γ-Cyclodextrins considerably deteriorated the dehydrocoupling of 1 probably due to both the formation of insoluble inclusion complexes in toluene and the encapsulation of SiH2 moiety. The resulting silole polymer 2 emits green light at 520 nm and is electroluminescent at 520 nm.

Biodegradable cationic poly(ester-amide) polymers were synthesized by double-monomer method, that showed excellent solubility in many organic solvents and water. Different degradation patterns were obtained by the regulation of monomer ratios and overall long period of time of DNA protection up to 12 days was shown by PicoGreen reagent assay. Good transfection profiles in the presence of serum and very low toxicity on mammalian cells may allow these polymers to become suitable for long-term gene delivery systems and therapeutic applications.

One-pot Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), promoted by a mixture of AgNO3-H2PtCl6 (150/1 mole ratio) readily gave poly(alkoxysilane)s in good yield (62-91%). The addition of small amount of platinum complex to form nanoparticles facilitated the silicon polymer formation when compared to the reaction rate with AgNO3 alone. The primary/secondary hydrosilanes [p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2] and alcohols [MeOH, EtOH, (i)PrOH, PhOH, and CF3(CF2)2CH2OH] were used for the reaction. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,690-7,100 Dalton and 1.44-3.49, respectively. The reaction of phenylsilane with ethanol (1:3 mole ratio) using the Ag-Pt complexes produced triethoxyphenylsilane only, as expected. The reaction of phenylsilane with Ge-132 produced an insoluble cross-linked gel.

The thermal decomposition of tetrakis(ethylmethylamido) titanium (TEMAT) has been investigated in Ar and H 2 gas atmospheres at gas temperatures of 100-400 °C by using Fourier Transform infrared spectroscopy (FTIR) as a fundamental study for the chemical vapor deposition (CVD) of titanium nitride (TiN) thin film. The activation energy for the decomposition of TEMAT was estimated to be 10.92 kcal/mol and the reaction order was determined to be the first order. The decomposition behavior of TEMAT was affected by ambient gases. TEMAT was decomposed into the intermediate forms of imine (C=N) compounds in Ar and H 2 atmosphere, but additional nitrile (RC≡N) compound was observed only in H 2 atmosphere. The decomposition rate of TEMAT under H 2 atmosphere was slower than that in Ar atmosphere, which resulted in the extension of the regime of the surface reaction control in the CVD TiN process.

Institute of Polymer Chemistry, Nankai University, Tianjin 300071, ChinaReceived April 9, 2002Key Words : Polymerization, Acrylic acid, Chlorocarbon, MetalloceneVinyl monomers undergo addition polymerization byradical, ionic or both initiators, depending on the type ofsubstituent of vinyl derivatives.

In this paper, carbon fibers with improved thermal stability and oxidation resistive properties were prepared and evaluated their physical performances under oxidation condition. Carbon fibers were coated with SiC particles dispersed in a polyacrylonitrile solution and then followed by pyrolyzed at 1400 °C to obtain the SiC nanoparticle deposition on the surface of the carbon fiber. The SiC coated carbon fiber showed extended oxidation resistive property as remaining 80–88% of the original weight even at high temperature 1000 °C under air, as compared with the control of zero weight at 600 °C. The effects of the coating conditions on the oxidation resistive properties of the coated fibers were studied in detail.

Pb(Zr,Ti)O3 film was prepared by dipping–pyrolysis process using metal naphthenates as starting materials. X-ray diffraction θ–2θ scans and β scans (pole figures) showed that a Pb(Zr,Ti)O3 film with a homogeneous and smooth texture was epitaxially grown on LaNiO3/SrTiO3, while a polycrystalline film was formed on LaNiO3/LaAlO3.

The boric oxide deposition was performed to improve the oxidation resistivity of carbon nanofiber (CNF) from electrospinning at elevated temperatures. The stabilized electrospun polyacrylonitrile (PAN) nanofibers were coated with boric oxide, followed by heat treatment up to 1000, 1200, and 1400 degrees C in an inert nitrogen atmosphere. The relative oxidation resistance of boric oxide-coated CNFs showed oxidation resistive property, which was determined by weight loss after running a thermogravimetric analyzer (TGA) under air flow. The data were used for the calculations of activation energies through Arrhenius plot. The oxidation resistance of the boric oxide-coated CNFs was depended on the heat treatment temperature, the higher the temperature more resistive to oxidation. The boric oxide-coated CNFs showed extended oxidation resistivity as remaining 40-83% (w) of the original weight at the high temperature 1000 degrees C under air.

A simple one-step method was used for preparing the beta-cyclodextrin/polyacrylonitrile (PAN) nanofibers deposited with silver nanoparticles by electrospinning and followed by the reduction of the Ag+ ions. The nano-composite fibers were stabilized at 280 degrees C in air and activated at 800 degrees C for 1 h in steam/N2. The structures of nano-composite fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction analysis (XRD). The electrochemical behaviors of the composite of carbon nano-fibers were investigated by cyclic voltammetry and charge/discharge tests.

Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), catalyzed by AgNO3 which converted to Ag(0) colloidal nanoparticles, gave poly(alkoxysilane)s in one-pot in moderate to high yield. The hydrosilanes include p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols include MeOH, EtOH, (i)PrOH, PhOH, and CF3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600 approximately 8,000 Dalton and 1.4 approximately 3.5. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the silver nanocolloid catalyst produced only triethoxyphenylsilane as product.

Silver nanoparticle/bis(o-phenolpropyl)silicone composites have been synthesized by the reduction of silver nitrate with bis(o-phenolpropyl)silicone BPPS [(o-phenolpropyl)2(SiMe2O)n, n = 2, 3, 8, 236]. TEM and FE-SEM data clearly show that the silver nanoparticles with the size of < 20 nm are well dispersed throughout the BPPS matrix in the composites. XRD patterns are consistent with those for multicrystalline silver. The size of silver nanoparticles increased with increasing the relative molar concentration of silver salts added. It was found that in the absence of BPPS, most of the silver nanoparticles undergo macroscopic precipitation by agglomeration, indicating that BPPS is essential to stabilize the silver nanoparticles.

Silver nanoparticles are prepared in an aqueous medium consisting of an inclusion complex beta-CD/PS, formed between beta-cyclodextrin (beta-CD) and phenylsilane (PS). The PS acts as a reducing agent. beta-CD/PS complex stabilizes the Ag nanoparticles preventing agglomeration and provides a self-assembling environment for forming nanostructure around Ag nanoparticles. The TEM (transmission electron microscopy) and FE-SEM (field emission scanning electron microscopy) data suggest the formation of hybrid composites in which large numbers of silver nanoparticles (< 20 nm) are dispersed. SAED patterns are consistent with that for fcc-typed silver. In the absence of the beta-CD/PS inclusion complex, most of the silver particles underwent macroscopic precipitation, which indicates that the beta-CD/PS inclusion complex is essential for stabilizing the silver nanoparticles.

The synthesis and characterization of spherical silver/polyphenylsilane (PPS) hybrid nanocomposites were carried out. A one-step conversion of metallic salts to stable metal nanoparticles was possible by a simple and mild PPS-mediated method. TEM (transmission electron microscopy) and FE-SEM (field emission scanning electron microscopy) data confirm the formation of the hybrid nanocomposites in which large numbers of silver nanoparticles (< 30 nm) are dispersed throughout the PPS matrix. XRD (X-ray diffraction) patterns are consistent with that for fcc-typed silver. The size and processability of such nanoparticles depend on the metal to PPS ratio. The PPS with Si-H functionalities play an important role as a reducing agent and as a stabilizing agent in the formation of the silver nanostructures. In the absence of the polymer, most of the silver particles underwent macroscopic precipitation.

Cyclic-pulsed plasma-enhanced chemical vapor deposition (PECVD) for the formation of antimony (Sb) thin films was investigated using Sb(i-C3H7)3 and H2 plasma at temperatures of 200-275 degrees C. The effects of deposition temperature on the film properties, such as resistivity, surface roughness, and crystallinity were examined. The film growth rate (thickness/cycle) was found to be in the range of 0.10-0.5 nm/cycle. High substrate temperatures tended to promote low resistivity, high purity, and smooth surface morphology of the films, compared to low substrate temperatures. All of the deposited films were polycrystalline, with higher deposition temperatures yielding a higher crystallinity in the Sb films.

The one-pot preparation and structural characterization of silver/poly(p-Cl-phenylsilane) nanocomposites have been performed. The one-step transformation of silver(I) salt to stable silver(0) nanoparticles is mediated by poly(p-Cl-phenylsilane), Cl-PPS having both reactive Si-H bonds in the polymer backbone and C-Cl bonds in the substituents. XRD, TEM, and FE-SEM, and solid-state UV-vis analytical techniques were used to analyze the interesting metal/inorganic polymer hybrid nanocomposites. TEM and FE-SEM data show the formation of hybrid composites in which large number of silver nanoparticles (less than 30 nm of size) are dispersed throughout the Cl-PPS matrix. XRD patterns are consistent with that for fcc-typed silver. The elemental analysis for Cl atom and the polymer solubility confirm that the appreciable cleavage of C-Cl bond and the Si-Cl dative bonding were not occurred. The size and processability of such nanoparticles depend on the ratio of metal to Cl-PPS. In the absence of Cl-PPS, most of the silver particles undergo macroscopic aggregation, which indicates that the polysilane is absolutely necessary for stabilizing the silver nanoparticles.

Catalytic dehydropolymerization and subsequent silane-capping with R2 SiHCl (R = Ph, Me)of 1,1-dihydrotetraphenylsilole (1) using various inorganic hydrides produces electroluminescent silane-capped polysiloles (2)in high yield. The polymerization yield and molecular weight increase in the order LiB[CH(CH3)C2H5]3H < NaB[CH(CH3)C2H5]3H < KB[CH(CH3)C2H5]3H. The molecular weights increase in the order Na[H2Al(OCH2CH2OCH3)2] < KB[CH(CH3)C2H5]3H < LiB(C2H5)3H. The silane-capped polysiloles 2 emit at 521 nm and are electroluminescent at 522 nm. The fluorescence quantum yield of 2 in toluene is (1.67 ± 0.31) × 10−2. The emission color is green and the maximum brightness of the device is 2,900 cd/m2 with a luminous efficiency of 0.69 lm/W. The substituent type of silyl end group showed no appreciable effect on the luminescent properties of polysilole backbone. Thus, the silane-capped polysiloles are found to be a good material for OLED fabrication. A possible mechanism for the formation of 2 was suggested.

The dry sol–gel reaction at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to p-C6H4SiO3 in high yield, catalyzed by nickelocene, is reported. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si–H bonds still remained in the gel because of steric reason. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol–gel reaction was suggested.

The plasma assisted atomic layer deposition (ALD) of tantalum nitride (TaN) thin films were conducted using tert-butylimino-tris-ethylmethylamino tantalum (TBTEMAT) and hydrogen plasma at 250 °C. The effects of H2-plasma pulse time and RF power on the film properties, such as resistivity, surface roughness, step coverage and stability in air, were examined. The film growth rate (thickness/cycle) was in the range of 0.05–0.08 nm/cycle and the resistivity of the films varied from 490 to 70000 μΩ cm, depending on the plasma conditions. Longer plasma pulse times and increasing RF power yielded films of lower resistivity along with improving the stability. The films were smooth and the conformality of the films deposited in 0.28 μm holes with an aspect ratio of 7:1 was 100%.

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. The compositions showing good spinnability are proposed within the soluble concentrations in the ternary phase diagram of the PAN–pitch-solvent, which contains lower concentration of the pitch. Activated carbon fibers were derived by stabilization, carbonization and steam activation at 700, 800, 900 and 1000 °C of the PAN/pitch electrospun fibers. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m 2 /g.