X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber have revealed that for the catalysts obtained by the reduction of preactivated samples, no complete reduction of platinum takes place.

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, , , .

     

X-ray diffraction studies of reforming platinum-alumina catalysts in a high-temperature chamber

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber indicate that in a stream of hydrogen starting from 550–600 K, platinum is practically completely reduced. In several cases at higher temperatures a platinum hydride is also formed.

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, , 550–600 ; .

     

Catalytic decomposition of hydrogen peroxide by a flow-through self-regulating platinum black heater

A flow-through reactor where a fine platinized platinum wire (Pt black wire) runs through the entire length of the PTFE tube was fabricated for the rapid decomposition of hydrogen peroxide (H₂O₂) at concentrations up to 1 M. Since the Pt black wire is directly electrically heated and the exterior of the tubular reactor is well insulated, the energy efficiency of this heater reactor is excellent. The temperature coefficient of resistance of the wire is significant (3280±40 ppm/°C). This provides a means to ascertain the mean temperature by measuring the resistance of the wire. The concentration of residual H₂O₂ was determined by the hematin-catalyzed oxidation of nonfluorescent thiamine to fluorescent thiochrome by H₂O₂. Essentially, quantitative (99.997%) decomposition of 1 M H₂O₂ could be achieved at a mean reactor temperature of 108 °C from a neutral aqueous solution with a mean residence time of ∼270 s.     

TPD studies of ethylene adsorption over platinum black

TPD studies of ethylene adsorption over Pt-blacks of various dispersity with and without hydrogen at 298 K indicate that the metal dispersity and the presence of hydrogen on the surface influence the direction of hydrocarbon transformation on platinum.

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298 Pt- . .

     

Needle-type glucose biosensor with an electrochemically codeposited enzyme in a platinum black matrix

In this study we report the development of a needle-type glucose biosensor for the management of hemorrhagic shock. The immobilization technique depends on the electrophoretic deposition of the glucose oxidase enzyme in an electrochemically grown platinum black matrix. The sensor was coated with Nafion to decrease the effect of interferents. Preliminary tests were carried out to evaluate the sensor performance in vitro. These tests included the measurement of glucose levels in buffer solutions containing various potential physiological interferents, as well as in bovine serum. The preliminary results show the sensor to have inearity up to 33 mM and a diminished response to interferents. The advantages of this technique are its simplicity and high controllability.     

Hydrogenation of nitric oxide on platinum black in acidic solution

By comparison of the catalytic hydrogenation and electrochemical reduction of NO on platinum black catalysts it has been shown that the hydrogenation of NO to ammonia and to hydroxylamine occurs in the diffusion controlled region only.

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NO , NO .

     

Studies of bulk and supported Cu?Cr catalysts in a high-temperature X-ray chamber

Bulk and -Al₂O₃-supported Cu–Cr catalysts have been studied in a high-temperature X-ray chamber in air, inert (He) and reducing (He+5% H₂) media. The different course of solid-phase reactions is due to the gas phase composition and the presence of a support.

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-Al₂O₃ , () (He+5%H₂) . , .

     

CF2HCl在铂黑上的催化解离动力学

本文研究了CF2HCl在铂黑表面上的单分子反应,在压力较高时为零级,压力较低时为一级,表明此反应为典型的催化反应,测定了CF2HCl在铂黑表面上催化反应的活化能为36.2kcal/mol.     

Reactivity of hydrogen adsorbed on platinum black towards ethylene

TPD studies of the reactivity of hydrogen adsorbed on dispersed Pt-black towards ethylene at –90, 30 and 200°C indicate that molecular forms of hydrogen with E_des from 3 to 16 kcal/mol are reactive species.

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Pt- –90, 30, 200°C . , . 3 16 /.

     

Determination of platinum in ores by a combined fire assay—X-ray fluorescence method

A combined fire assay—x-ray fluorescence procedure for the determination of platinum in ores is described. Silver beads obtained by cupellation in the classical fire assay process are flattened to constant thickness before placement in the x-ray beam. A standard plot of platinum—silver intensity ratio versus platinum concentration is used to measure the platinum content of ore samples.     

X-ray scattering by black foam films

The x-ray scattering by the three types of black foam films (common black, Newton black, and stratified black films) was experimentally studied. A special device in which flat black films with an area of ca. 2 cm² can be produced was developed and x-ray diffraction patterns were obtained by a vertical diffractometer. The three types of films differ significantly in their x-ray reflections, which proves that they have different structure. For common black films, the comparison of observed and calculated intensities lead to a model, which corresponds to the three-layer model. The Newton black films exhibit diffraction trace with only one highly asymetric peak and there is, as of yet, no unambigous interpretation. The patterns of the stratified black films have several pronounced sharp peaks corresponding to the areas of different films with a given thickness.     

Analysis of high-temperature superconducting films by X-ray fluorescence analysis

Radionuclide X-ray fluorescence analysis was used for the determination of Cu, Y and Ba in very thin high-temperature superconducting films. The precision of the method is better than 3% for about 1 m thick films. The atomic emission ICP spectrometry was used to testify results of XRF analysis. An acceptable agreement of both methods was obtained.     

X射线荧光光谱法测定重整铂催化剂中氯

建立重整铂催化剂中氯的X射线荧光光谱测定方法。通过研磨机将铂催化剂研磨至粒径小于75 μm的颗粒,采用仪器压片制样,通过测量不同氯含量样品的计数率,建立铂催化剂中氯含量与计数率的线性关系。氯的质量分数在0.85%~1.04%范围内与计数率成良好的线性关系,相关系数为0.9995,检出限为0.0076%。样品加标回收率为96.2%~104.2%,测定结果的相对标准偏差小于2%(n=6)。该法测定结果与电位滴定法相吻合。该方法精密度高,分析速度快,满足重整装置生产调整的要求。     

Thermal analysis and high-temperature X-ray diffraction study of BiNbO4

Journal of Thermal Analysis and Calorimetry - Phase transformations of bismuth orthoniobate BiNbO4 were studied by the methods of differential scanning calorimetry and high-temperature X-ray...     

Thermal analysis and high-temperature X-ray diffraction of nano-tricalcium phosphate crystallization

Calcium phosphate biomaterials have long ago attracted the interest of world-wide scientists because they form the main inorganic constituent of the human bones and teeth. Classical approaches to synthesize this ceramic material did not give satisfactory results until present, so new approaches are required. In this article the tricalcium phosphate achievement by a method which is a combination of sol–gel and classic precipitation from solution is presented, starting from CaCl₂ as calcium precursor and H₃PO₄ as phosphorus precursor, without pH adjustment. The reaction mixture was allowed to maturate for 2 months, the time influence on the precipitated material being presented in previous articles. Present studies aimed at the influence of temperature on the structural characteristics of precipitated and maturated material, by means of thermal analysis, X-ray diffraction, infrared spectroscopy, and high-temperature X-ray diffraction. A complex type thermal decomposition takes place while heating the sample to 1000 °C, with superposed and parallel processes. The sample goes through alternative amorphous and crystalline stages before final crystallization of β-tricalcium phosphate takes place. The high-temperature XRD studies offered the great advantage of being both a synthesis and a physico-chemical characterization technique, which along with thermal analysis and infrared spectroscopy, gave a lot of useful information in a very short time.     

Strong electron correlation effects in X-ray and photoelectron spectra of high-temperature superconductors

This review is a detailed analysis of the literature (161 references) dealing with experimental and theoretical investigations of the electronic structure of high-temperature superconductors. Special attention is paid to the sudden perturbation model, which was effectively used to describe and interpret a series of X-ray and photoelectron experiments.     

X-ray characteristics of iridium and platinum blacks of various dispersity

X-ray and structural characteristics of iridium and platinum blacks of various dispersity in the coherent scattering region from 40 to 700 Å have been studied. High dispersity blacks are shown to contain crystalline and X-ray amorphous particles with a disordered structure and decreased coordination number. For such blacks a 0.003 Å increase in the unit cell parameter is observed.

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40 700 Å. , , . 0.003 Å.