Preparation of sphere-shaped nanoscale carbon nitride polymer

The carbon nitride polymer of the previously unknown sphere-shaped structure was prepared both by a template-directed solid-state and solution phase syntheses from cyanuric chloride or fluoride and lithium nitride. The obtained polymer powder was characterized by SEM/EDAX, TEM, XRD, TGA, XPS, (¹³C) MAS NMR, LD/MS, FTIR, UV-visible, and Raman spectroscopy. Modification of the surface area of the template used demonstrated the possibility of producing the carbon nitride spheres with the particle sizes ranging from 20 m to 50 nm. According to TEM data, the spheres are hollow and the material is shown to be essentially amorphous by powder XRD.     

Control of superhydrophilicity/superhydrophobicity using silicon nanowires via electroless etching method and fluorine carbon coatings

Surface roughness is promotive of increasing their hydrophilicity or hydrophobicity to the extreme according to the intrinsic wettability determined by the surface free energy characteristics of a base substrate. Top-down etched silicon nanowires are used to create superhydrophilic surfaces based on the hemiwicking phenomenon. Using fluorine carbon coatings, surfaces are converted from superhydrophilic to superhydrophobic to maintain the Cassie-Baxter state stability by reducing the surface free energy to a quarter compared with intrinsic silicon. We present the robust criteria by controlling the height of the nanoscale structures as a design parameter and design guidelines for superhydrophilic and superhydrophobic conditions. The morphology of the silicon nanowires is used to demonstrate their critical height exceeds several hundred nanometers for superhydrophilicity, and surpasses a micrometer for superhydrophobicity. Especially, SiNWs fabricated with a height of more than a micrometer provide an effective means of maintaining superhydrophilic (<10°) long-term stability.     

Characterisation of the interface of sputter-deposited copper coatings on nitrogen plasma-treated carbon substrates

The adhesion of copper coatings to carbon substrates is very poor, because of lack of diffusion or reaction between the constituents. Because there is technological interest in enhancing the adhesion and improving the interface between copper and carbon, plasma treatment of the carbon substrate was employed in this study. For modification of the carbon surface a nitrogen plasma was used. It was confirmed by pull-off tests that the strength of adhesion of the copper coating can be improved by a factor of more than 10 by plasma pretreatment, even after treatment for a very short time (1 min). To obtain more information about the mechanisms of the processes occurring at the interface SIMS investigations were performed on samples which had been treated for different times (between 1 and 60 min). These measurements confirmed that nitrogen is located on the interface. With increasing pretreatment time the amount of nitrogen detected on the interface increased. Besides characterisation of as-deposited samples, another focus was to study the mechanisms of diffusion of nitrogen if the samples are heat treated at 500°C.     

Preparation of micron-sized, monodispersed, anomalous polymer particles by utilizing the solvent-absorbing/releasing method

 About 2-μm-sized polystyrene (PS) particles having uneven surfaces were prepared by a posttreatment in which toluene-swollen PS particles were thrown into a methanol bath to release toluene therefrom rapidly. The posttreatment was named the “solvent-absorbing/releasing method”. The PS particle had large dents at the surface. The size of the dents was changed by the conditions of the posttreatment. Received: 3 August 1999/Accepted: 1 March 2000     

流变相法制备包覆型零价纳米铁及其表征

以FeSO4.7H2O∶KBH4=1∶2(摩尔比)为固相介质,0.06 g/ml羧甲基纤维素水溶液为液相介质,固液比1∶2,调制成流变相体系反应2 h制备出包覆型纳米零价铁;采用XRD、TEM等手段对合成的纳米零价铁进行表征。     

C掺杂ZrO_2四方纯相粉体的甲醇溶剂热制备及热稳定性研究

在ZrO(NO_3)_2·2H_2O-CO(NH_2)_2-CH_3OH溶剂热过程中,水的缺乏使得甲醇通过其甲氧基与Zr~(4+)发生亲核取代或以分子配位,直接参与锆盐的水解-缩聚反应,形成具有[ZrO_z(OH)_p(OCH_3)_q·rCH_3OH]_n结构的无机聚合物;同时,甲醇对聚合物低的溶解能力强烈抑制了Ostwald熟化过程,阻碍了溶剂热产物的晶化与热力学支持的结构重排。尿素通过其水解作用与锆盐竞争体系中的水及锆物种骨架上的羟基,这不仅导致无机聚合物中Zr-O-Zr键合相对Zr-OH键合的比例增加,使得溶剂热产物发生结构重排的几率进一步下降;而且也一定程度上增加了溶剂热产物中甲氧基的含量。含有大量甲氧基团的溶剂热产物经400℃焙烧后,形成C掺杂ZrO_2。C掺杂与溶剂效应共同稳定了ZrO_2的四方相。在500-600℃中等温度、空气气氛焙烧过程中,C掺杂ZrO_2四方相结构显示了良好的热稳定性;提高焙烧温度至700℃,游离于颗粒表面的C被完全氧化去除,固溶于晶格中的C也部分脱溶,导致了部分四方相失稳转变成单斜相。     

Preparation and lithium storage performance of silicon and carbon microrods by chemical vapor co-deposition

Silicon/carbon microrods are co-deposited on copper substrate and graphite spheres surface using dimethyl dichlorosilance as carbon and silicon precursor. The obtained composites are characterized by X-ray diffraction and scanning electron microscopy. The experimental results show that silicon/carbon microrods deposited on the copper substrate, whose diameter is about 500 nm, are accumulated into sisallike morphology, those deposited on the graphite spheres surface form hedgehog-like feature, whose diameter is about 200 nm and whose top is like cauliflower. When current density of 50 mA/g is applied, charge capacity of silicon/carbon microrods is 1492 mA h/g (deposited on copper substrate) and 693 mA h/g (deposited on the graphite spheres surface). Moreover, silicon/carbon microrods deposited on the graphite spehres and copper substrate respectively deliver the capacity of 592, 985 mA h/g, and display no capacity decay at all after the 20 cycles, when cycled under current density of 500 mA/g.     

Preparation of nano-sized polybenzimidazole and carbon particles via poly(amino-amide) particles

Poly(amino-amide; PAA) particles consisting of p-phthalyl chloride and 3,3′-diaminobenzidine and 4,4′-diphenyldicarbony chloride and 3,3′-diaminobenzidine were prepared. The particles were then transformed by treatment with heat into poly(p-phenylenebenzimidazole; PPC–PAA) and poly(4,4′-diphenylenebenzimidazole; DPC–PAA) particles, respectively. The number ratio of ring-closing of the obtained product was found to be dependent on the processing temperature. However, the morphology and diameter of the products were not found to be temperature dependent. PPC–PAA particles were amorphous and DPC–PAA particles had a high degree of crystallinity. Further, upon heating up to 1,000 °C, poly(p-phenylenebenzimidazole) and poly(4,4′-diphenylenebenzimidazole) particles were transformed into carbon particles and carbon bulk, respectively. The poly(amino-amide), polybenzimidazole and carbon particles obtained were nano-sized spherical particles with narrow size distributions.     

Stable containment of radionuclides on the nanoscale by cut single-wall carbon nanotubes

The physisorption of radiolabeled (125)I(-) ions from aqueous solution and the Brunauer-Emmett-Teller (BET) surface areas of various carbonaceous materials [HiPco single-wall carbon nanotubes (SWNTs), F-SWNTs, cut SWNTs, charcoal, graphite, F-graphite and C(60)] have been measured and compared. By far, cut SWNTs (mainly 20-50 nm lengths) displayed the largest surface area of the materials (1180 m(2).g(-1)), being approximately double that of uncut SWNT and charcoal. At low concentrations of (125)I(-), nearly all of the (125)I(-) was adsorbed from aqueous solution within 1 min at room temperature by the cut SWNTs, uncut SWNTs, and charcoal; the other materials showed much less adsorption under the same conditions. Once adsorbed, the (125)I(-) wash-off rate by pure water was highly variable but was especially slow for cut SWNTs (t(1/2) approximately 2720 h) compared to the other materials; wash-off of (125)I(-) by an aqueous H(2)O(2) solution was even slower (t(1/2) approximately 14 300 h). Taken together, these data demonstrate the greatly increased surface area and dramatically enhanced retention properties of cut SWNTs over uncut SWNTs.     

Electropolymerized coatings of polyaniline on copper by using the galvanostatic method and their corrosion protection performance in HCl medium

The synthesis of polyaniline coatings on the copper (Cu) surface has been investigated by using the galvanostatic method. The synthesized coatings were characterized by Fourier transform infrared spectroscopy, UV–visible absorption spectrometry and scanning electron microscopy. The anticorrosion performances of polyaniline coatings were investigated in 0.5 M HCl medium by the potentiodynamic polarization technique and electrochemical impedance spectroscopy. The corrosion rate of polyaniline‐coated Cu was found to be ～27 times lower than bare Cu, and potential corrosion increased from ?0.21 V versus Ag/AgCl for uncoated Cu to ?0.19 V versus Ag/AgCl for polyaniline‐coated Cu electrodes. Electrochemical measurements indicate that polyaniline coating has good inhibiting properties with a mean efficiency of ~96% at 10 mAcm^?2 current density applied on Cu corrosion in acid media. The results of this study clearly ascertain that the polyaniline has an outstanding potential to protect Cu against corrosion in an acidic environment. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of carbon impurities in epitaxial layers from semiconductor silicon by means of charged particles

The energy-dependent range of charged particles in activation analysis according to the reaction¹²C(d,n)¹³N permits the method to be applied to carbon determination in model epitaxial layers of sufficient thickness. We investigated 100 μm epitaxial layers of the n-type and undoped 50 μ layers as to p⁻ Czochralski substrates. Deuterons were slowed down with Cu and Ta foils having a limiting energy of 13.5 MeV, to 4.2 MeV and 2.9 MeV, respectively. In the resulting activation depths of 52 and 102 μm, the sensitivity of the method, which is 3·10¹⁴ at ·cm⁻³C at E_d=10 MeV in silicon, is reduced to 25% and 10%, respectively. An optimal flux of 0.9 μA·cm⁻² was maintained. After irradiation, 20 or 10 μm were etched off. The sample was inductively fused at 1500 K in a Pb₃O₄/B₂O₃ mixture.¹³N was passed with He as carrier gas into an absorption vessel kept at 77 K, and its activity was measured in γ, γ-coincidence.     

Preparation and photoelectric properties of organoinorganic polymer nanocomposites on the basis of ultradispersed molybdenum disulfide particles

Photoconducting nanocomposites were prepared by incorporating nanoparticles obtained by monolayer dispersion of crystalline molybdenum disulfide into various polymer matrices (nonconducting and p-or n-type conducting). The shift of the absorption spectrum caused by changes in the concentration of MoS₂ nanoparticles demonstrated that such particles exhibit a quantum-size effect, the characteristics of which were found to be determined by the efficiency of their stabilization in each of the polymer matrices. Studying the photoelectric sensitivity of films of n-type-conduction composites on the basis of polymethylphenylsiloxane modified with 2,4,7-trinitrofluorenone (an electron acceptor) units demonstrated that molybdenum disulfide nanoparticles possess acceptor properties (characterized by an electron affinity energy of E _a > 2 eV, in agreement with the observation that composite films based on poly(N-epoxypropylcarbazole (a p-type-conduction matrix) doped with p-diethylaminobenzaldehyde-N,N-diphenylhydrazone (an effective donor), exhibit an enhancement in the proper photosensitivity of the p-type-conduction matrix in its absorption band (λ < 400 nm). For large molybdenum disulfide particles capable of absorbing light with λ > 600 nm (formed at a MoS₂ concentration of > 2.0 wt %), a weakening of the acceptor properties was observed, a feature responsible for decreases in the photosensitivity and the quantum yield of the photogeneration of holes and for the capture of holes in traps. A mechanism of the photogeneration of charge carriers with the participation of the phototransfer of electrons leading to the formation of electron-hole pairs was discussed.     

Study of the quality of Gaussian basis sets for carbon and silicon: Calculations on methane and silane

A number of Gaussian basis sets for carbon and silicon have been examined in terms of the one-electron properties of methane and silane. The convergence of the properties to their limiting values is not monotonic but, in general, a representation that involves five Gaussian functions per occupied atomic orbital on the heavy atom is sufficient to closely approach the limits. A relationship between the sizes and partitioned electronic energies is shown to hold to a good approximation for the Boys spatially localized molecular orbitals employed in this study.     

Preparation of micron-sized, monodispersed, monomer-adsorbed polymer particles utilizing the dynamic swelling method with loosely cross-linked seed particles

Influence of the water-addition rate (R _w ) (ml/h) on the monodispersity of monomer-adsorbed polymer particles prepared by utilizing the dynamic swelling method (DSM) with 1.9-μm-sized, monodispersed, loosely cross-linked polystyrene/styrene-divinylbenzene copolymer [1/(47.5–2.5), w/w] composite particles was examined theoretically and experimentally. The thermodynamic simulation under a kinetic control state indicates that, at the R _w values below 4, the cross-linked composite particles adsorb all styrenes separated from ethanol/water media. The experimental result at the R _w value of 2.66 supported it. At the R _w values above 5.32 and below 1.33, polydispersed styrene-adsorbed particles were prepared. The former depended on the formation of some pure styrene droplets not containing the composite particle. The latter depended on coalescence among the adsorbed particles by DSM. Received: 5 April 2000 Accepted: 5 October 2000     

Preparation of cationic nanoparticles by the particle dissolution method from submicron-sized,styrene-butyl acrylate-dimethylaminoethyl methacrylate terpolymer particles

Cationic nanoparticles were prepared from submicron-sized styrene-butyl acrylate-dimethylaminoethyl methacrylate terpolymer (59.2/20.8/20.0, molar ratio) particles in a polyoxyethylene nonylphenylether nonionic emulsifier aqueous solution at pH 2.0 above 150 °C.     

Simultaneous determination of nickel and copper,on the basis of complex-formation kinetics

This paper reports the analysis of mixtures of nickel and copper, by means of a complex formation reaction and use of the following differential kinetic methods: logarithmic extrapolation, single-point, and reaction rate. All three methods give similar relative standard deviations, but the concentration ratio range in the logarithmic extrapolation method is wider than in the other two. The logarithmic extrapolation method allows determination of nickel and copper in ratios ranging from 1.51 to 16.     

Deposition of thin antireflection coatings based on mesoporous silicon dioxide by the sol-gel method in the presence of carbochain polymers and statistical copolymers

Antireflection coatings with a low refractive index (1.25–1.34) were prepared from mesoporous silicon dioxide by using carbochain polymers and statistical copolymers, instead of ionogenic and noionogenic surfactants and amphiphilic block-copolymers in a sol-gel process. The optimal concentration of the organic additive in the sol, at which a transparent film with the maximum antireflection effect is formed in the sol-gel process followed by heating of a sample, was determined.