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181.
Summary A miniaturized flow cell for an electrical conductivity detector has been made and applied to the ion chromatography of inorganic anions. It consisted of stainless steel tubes (0.13 mm ID×0.31 mm OD) and PTFE tubes (0.25 mm ID×2 mm OD). The detection limit for chloride at S/N=3 was 36 pg or 0.33 ppm for a 0.11 l injection. 相似文献
182.
Hiromi Matsushita Ritsuko Nagao Masayuki Nogami Toshihiro Kasuga Tomokatsu Hayakawa 《Journal of Sol-Gel Science and Technology》2000,19(1-3):559-562
High proton-conducting P2O5-SiO2 glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P2O5·95SiO2 glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region. 相似文献
183.
N. P. Bessonova I. A. Volegova Ye. V. Konyukhova E. A. Flexman Yu. K. Godovsky 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):773-783
Poly(oxymethylene)s with different molecular mass and chemical structure were studied using DSC, dynamic mechanical relaxation, thermomechanical analysis, and thermogravimetry.Molecular mobilities of two types were found in the amorphous phase of poly(oxymethylene). Unconstrained chains of poly(oxymethylene) soften at –70°C and then amorphous chains with different restraints from the crystalline phase are successively activated in a wide temperature interval.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThis work has been supported by DuPont Company 相似文献
184.
A new percolation problem is posed where the sites on a lattice are randomly occupied but where only those occupied sites with at least a given numberm of occupied neighbors are included in the clusters. This problem, which has applications in magnetic and other systems, is solved exactly on a Bethe lattice. The classical percolation critical exponents=gg=1 are found. The percolation thresholds vary between the ordinary percolation thresholdp
c
(m=1)=l/(z – 1) andp
c(m=z) =[l/(z – 1)]1/(z–1). The cluster size distribution asymptotically decays exponentially withn, for largen, p p
c
.Supported in part by National Science Foundation grant DMR78-10813. 相似文献
185.
M. G. Ferreira Da Silva J. M. Fernàndez Navarro 《Journal of Sol-Gel Science and Technology》1994,2(1-3):895-901
The effect of thermal treatment on the structural incorporation of Cr2O3 in xCr2O3·(100 – x)SiO2 and 5R
n
O·xCr2O3·(95 – x)SiO2 (where x=0.01–1 mol.% and R=Li, Na and Ca) gel glasses was studied by optical absorption spectrophotometry, DTA-TG, XRD and electron microscopy.Samples heat treated at 60°C have green color due to the presence of Cr3+ in octahedral coordination. The optical transmission, and color (yellow, orange or ambar), of the samples heat treated between 200 and 700°C prove that Cr3+ (octahedrally coordinated) and Cr6+ (tetrahedrally coordinated) are both present. Segregation of Cr2O3 take place at temperatures above 800°C.In reducing conditions the gel glasses were green due to the presence of a high content of Cr3+ ions. Samples containing Li or Na show crystalline phases at temperatures below 850°C. 相似文献
186.
Fotini Pallikari-Viras Xiaochun Li Terence A. King 《Journal of Sol-Gel Science and Technology》1996,7(3):203-209
Thermal analysis of poly-methylmethacrylate (PMMA) impregnated porous gel silica glasses confirms that the PMMA chains form hydrogen bonds with the pore surface silanol groups. The adopted conditions for the insitu polymerisation result in about 4% of residual monomers trapped in the polymer, most of them in the amorphous structure. The polymer and monomer mixture takes up the whole of the free pore volume. Most of the residual monomer polymerises during the DSC scans above the glass transition temperature providing an excellent probe for the weak glass transition. Polymerisation in the gel silica glass medium affects the glass transition temperature, the length of polymer chains, and the degree of polymerisation. 相似文献
187.
Monodisperse, cationic polymer particles bearing quaternary ammonium groups effectively self-organized on hydrophobic solid substrates such as alkylated glass plates and polymer films to form particle monolayers. With an increase of the particle surface charge density, the surface coverage decreased and the morphology of particle monolayers changed from aggregated type to dispersed type. The dispersed type of particle monolayers having a relatively regular particle distance was formed at higher temperature. The self-organization behaviors on alkylated glass plates were different from those on unmodified glass plates through electrostatic interaction. The formation of particle monolayers on alkylated glass plates occurred only over a certain latex concentration range in contrast with that on unmodified glass plate. The adhesive strength of particle monolayers was enhanced by annealing at temperatures above the glass transition temperature (T
g) of the particles. Lens-shaped particle monolayers were fabricated by annealing the dispersed type of particle monolayers. 相似文献
188.
Rupert B. Hurley 《Journal of separation science》1980,3(3):147-148
This paper describes a design for an all-glass GC/MS interface. The design has advantages due to low dead volume, lack of column effluent adsorption and degradation, simple interface production and installation, and ease of column mounting/dismounting. 相似文献
189.
Thermal lens detection with a 325.0 nm He-Cd excitation laser is used for thermooptical indirect detection in combination with the capillary electrophoretic separation of organic anions. The optimization of indirect thermooptical detection is discussed. With Mordant Yellow 7 (an azo dye) chosen as a probe ion limits of detection for 1-heptane-, 1-pentane-, 1-butane-, 1-propanesulfonic, and acetic acid at a level of n × 10−7 M were achieved with a separation electrolyte containing 50 μM of the probe ion and 5 mM Tris pH 9.90. A further increase in the detection sensitivity (twofold decrease in the limit of detection ) was obtained with a separation electrolyte containing a volume fraction of 20% acetonitrile. 相似文献
190.
Measurement of the degree of crystallinity of the polymer matrix in a composite is complicated by the presence of the reinforcing additive. This is particularly the case in APC-2 in which as much as 70% can be carbon fibre. A First Law procedure, developed for determining the degree of crystallinity of PEEK, which involves direct measurement of the enthalpy changes associated with melting, crystallization and heat capacity changes, has found to be an effective method for the determination of the crystallinity of the PEEK matrix. The procedure has been applied to carbon fibre and glass fibre PEEK composites. 相似文献