An attempt to prepare carbon nanotubes by carbonizing polyphosphazene nanotubes with high carbon content

Polyphosphazene nanotubes with about 20 nm in inner diameter and 100-200 nm in outer diameter were fabricated easily and then carbonized at 800 °C in a nitrogen atmosphere. Scanning electron microscopy and transmission electron microscope results showed that the bulk morphology of polyphosphazene nanotubes was retained after carbonization. The carbon content of the carbonized samples reached 93.28%. X-ray diffraction and Raman spectrum showed that the carbonized samples had low graphitization state. The present method can be used for a mass production of carbon nanotubes.     

超声微乳液法制备Ag/AgCl复合纳米颗粒及其光催化性能研究

设计了一种全新的微乳液体系,以十二烷基磺酸钠(SDS)、乙醇、正丁醇和异辛烷的混合物作为复合乳化剂,采用超声微乳液法制备了Ag/AgCl复合纳米颗粒.利用SEM和EDS研究样品的形貌、尺寸及表面组成,通过研究样品对甲基橙降解过程的催化作用证明了样品在可见光下的催化活性.重点研究了反应物浓度对Ag/AgCl颗粒尺寸及形貌的影响,结果表明,Ag/AgCl复合纳米颗粒尺寸主要由微乳液尺寸决定,受反应物浓度的影响较小,反映出本工作提出的超声微乳液制备技术具有较高的工艺稳定性.     

Li2O-SiO2-V2O5-P2O5体系的锂快离子导体的研究

运用混料均匀设计方法,设计了四元体系Li2O-SiO2-V2O5-P2O5的实验配方,找出其中电导率最佳的区域以及电导率随配方的分布变化规律.试验验证点的实测值与预测值相当,得到的室温电导率达到10-5S/cm.     

The thermodynamics of the divalent metal fluorides. II. Heat capacity of the fast ion conductor BaSnF4 from 7 to 345 K

The heat capacity of the fast ion conductor BaSnF₄ was measured over the temperature range 7<T<345 K using adiabatic calorimetry. Our results show that a phase transition is not present. However, an anomalous rise in the molar heat capacity,C _p,m, occurs in the region 210<T<310 K; the entropy change of this rise amounts toS/R=0.112. This anomaly coincides with the temperature range where a break in the slope of the electrical conductivity has been observed, which results in a threefold decrease in the activation energy required in the temperature region above the break at 272 K. Standard molar thermodynamic functions are presented at selected temperatures from 5 to 345 K.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

An attempt to reduce training

Training, more or less tolerated in small superconducting magnets, is unacceptable for large coils. A simulation experiment was performed in which the influence of large conductor volume on training was substituted by high strain. Following this principle, the influence of warm cyclic prestrain on training was investigated. Optimal pretreatment reduces training by a factor of two according to the defined weighting and training numbers.     

Application of a new Cl-plasma-treated Ag/AgCl reference electrode to micromachined glucose sensor

Micromachined glucose sensors were fabricated and integrated with the plasma-treated Ag/AgCl reference electrodes for the first time. The surface of the Cl-plasma exposed AgCl layers was of granule-shaped morphology and showed the favorable long-term stability with a 13-mV potential drift after 5 h over a commercial liquid-junction Ag/AgCl reference electrode in phosphate buffered saline. The fabricated devices showed a typical behavior of an amperometric glucose sensor and a successful operation as a three-electrode system. Due to the integrability of the reference electrode and the use of low-temperature steps only, the new micromachined process can allow easy mass production of the device and the monolithic integration of signal processing circuitry in the future.     

Diffusion-controlled size-selective chloride ion sensing in the presence of bromide ion using a thin, nanoporous, plasma-polymerized coating on an Ag/AgCl electrode

We have developed a diffusion-controlled size-selective method for sensing chloride ion in the presence of bromide ion, based on a thin, nanoporous, plasma-polymerized coating of hexamethyldisiloxane on an Ag/AgCl electrode. Sub-nanometer-sized pores responsible for a highly cross-linked polymer network in the plasma-polymerized coating allowed diffusion-controlled permeation of chloride ion while blocking the larger bromide ion. An electrode coating of thickness greater than 70 nm enabled chloride detection in the concentration range 1-10 mM in the presence of 0.63 mM bromide ion. Advantages of this approach are: (1) simple design compared with ionophore-based strategies and (2) compatibility with microfabrication and mass production processes.     

An attempt to extract common behaviour from heterogeneous results about mechanical alloying

The first stages of the mechanical alloying process, fragmentation and welding, are analysed. In order to clarify the mechanisms of milling-induced diffusion, different interstitial solid solutions are examined. It is shown that diffusion of interstitial is mainly controlled by the stress field. In case of a substitutional solid solution, the mechanism of atomic transport is controlled by shear deformation. The consequence of the corresponding diffusion models are discussed.     

The structures of Ag55+ and Ag55- : trapped ion electron diffraction and density functional theory

We report the experimental structure determination of cold, mass selected Ag(55)(+/-) cluster ions using the recently developed technique of trapped ion electron diffraction. By comparison of experimental and theoretical molecular scattering functions and consideration of computed total energies, we show that Ag(55)(+) constitutes an ideal Mackay icosahedron, whereas Ag(55)(-) is a weakly Jahn-Teller distorted icosahedron. Isomers of other structural types, for example, decahedral or close-packed, could be ruled out. The candidate structures were obtained by density functional theory calculations.     

Studies on ionic transport properties of a new Ag+ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO2

A new Ag⁺ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO₂ using a quenched/annealed [0·75 AgI: 0·25 AgCl] as host compound in place of conventional host AgI, has been investigated. The effects of various preparation methods and soaking time are reported. The composition 0·8[0·75 Agl: 0·25 AgCl]:0·2SnO₂ exhibited optimum conductivity (σ = 8·4 × 10⁻⁴S/cm) with conductivity enhancement of ∼ 10¹ from the annealed host at room temperature. Transport property studies such as electrical conductivity (σ) as a function of temperature using impedance spectroscopy technique, ionic transference number (t _ion) using Wagner’s d.c. polarization method and ionic mobility (μ) by transient ionic current technique were carried out on the optimum conducting composition. The mobile ion concentration (n) was calculated from ‘σ’ and ‘μ’ data.     

Planar waveguides formed by Ag+-Na+ ion exchange in nonlinear optical glasses: diffusion and optical properties

All-optical communication systems are the subject of intense research related to the integration of nonlinear optical materials. In sodiocalcic borophosphate glasses that contain niobium oxide and exhibit high nonlinear optical indices, planar waveguides have been formed by a Ag(+)-Na(+) ion-exchange technique. WKB analysis has been used to characterize the diffusion profiles of silver ions exchanged in glass substrate samples chemically by an electron microprobe technique and optically by an M-line technique. These methods permit the Ag(+) penetration depth and diffusion profile shape and index profiles to be determined. The results are analyzed and discussed in relation to Ca(2+) concentration and exchange conditions in glasses. The Ag(+) diffusion in these glasses can be almost entirely controlled for index-profile engineering.     

一次烧成SrTiO3复合功能陶瓷中掺杂Ag+离子的行为及其机制

采用一次烧成工艺制备掺施主杂质Nb2O5和受主杂质Ag2O的SrTiO3电容－压敏复合功能陶瓷,分析了Ag2O掺杂对SrTiO3电容－压敏复合功能陶瓷,分析了Ag2O掺杂对SrTiO3陶瓷电学性能的影响,采用XPS和EPMA分析方法确定了Ag的结构状态。研究结果表明,Ag^ 离子存在于烧结助剂形成的晶界非晶相中,对SrTiO3晶粒的半导化状况未产生显著影响,吕Ag^ 离子低价取代晶粒表面的Sr^2 离子而形成晶界受主态,是产生晶界Schottky势垒及复合功能效就原重要原因。     

An attempt to produce both thick and thinned flowing superfluid films

As discussed in the preceding paper by Graham, a controversy has arisen over conflicting reports of whether a superfluid film becomes thinned when it is set into motion. We have performed an experiment designed to reproduce as nearly as possible two previous measurements giving opposite results. Our experiment is also designed to test directly a theory proposed by Goodstein and Saffman which would have reconciled the apparently contradictory observations. We are unable to reproduce the thick-film result, finding kinetic thinning in all cases, even where the Goodstein-Saffman theory would lead us to expect a thick film. We conclude, in agreement with Graham, that the film is always thinned when it flows, and that the theory is therefore unnecessary.Supported in part by NSF Grant No. DMR71-01819, and by the Caltech President's Fund.     

Ag nanoparticles enhanced near-IR emission from Er3+ ions doped glasses

Vitreous materials containing rare-earth (RE) ions and metallic nanoparticles (NPs) attract considerable interest because the presence of the NPs may lead to an intensification of luminescence. In this work, the characteristics of 1.54 μm luminescence for the Er³⁺ ions doped bismuthate glasses containing Ag NPs were studied under 980 nm excitation. The surface plasmon resonance (SPR) band of Ag NPs appears from 500 to 1500 nm. Transmission electron microscopic (TEM) image reveals that the Ag NPs are dispersed homogeneously with the size from 2 to 7 nm. The strength parameters Ω_t(t = 2, 4, 6), spontaneous emission probability (A), radiative lifetime (τ) and stimulated emission section (σ_em) of Er³⁺ ions were calculated by the Judd–Ofelt theory. When the glass contains 0.2 wt% AgCl, the 1.54 μm fluorescence intensity of Er³⁺ reaches a maximum value, which is 7.2 times higher than that of glass without Ag NPs. The Ag NPs embedded glasses show significantly fluorescence enhancement of Er³⁺ ions by local field enhancement from SPR.     

Conductivity of Zr-doped Na3PO4: A new Na+ ion conductor

Na₃PO₄ forms an extensive range of solid solutions with the replacement mechanism, 4Na⁺ ? Zr⁴⁺ and formula Na_3–4xZr_xPO₄:0 < x < 0.20. With increasing x, the conductivity increases markedly and passes through a maximum at $\text{x ? 0.13}$ with a value of 2.5 × 10^?2 ohm^?1cm^?1 at 300°C. The solid solutions are thermodynamically stable, easily prepared and sinter into dense ceramics at ～1000°C.