Platinum thermal properties

Thermal Properties. The thermal stabiUty of cellulose esters is deterrnined by heating a known amount of ester in a test tube at a specific temperature a specified length of time, after which the sample is dissolved in a given amount of solvent and its intrinsic viscosity and solution color are deterrnined. Solution color is deterrnined spectroscopically and is compared to platinum—cobalt standards. Differential thermal analysis (dta) has also been reported as a method for determining the relative heat stabiUty of cellulose esters (127). 

To reveal the thermal properties of aerogels, stationary hot-plate measurements are usually employed [45]. In such a measurement two equal aerogel specimens are sandwiched between a hot plate and two cold plates. If the electrical power fed into the hot plate and the temperature difference between the hot and the cold plates, as well as the thickness of the specimens, are known, the thermal conductivity can be derived. For the thermal characterization of opacified aerogels, the faster nonstationary hot-wire method can also be used. In this case a thin platinum wire is embedded into the aerogel specimen and a constant power is delivered into the wire, which also serves as a temperature sensor. From the temperature increase in the wire as a function of time, the thermal conductivity of the aerogel specimen can be determined [49]. 

In 1994, Dinwiddie and PyUdd [34,35] described the first combined SThM/AFM probes that employed resistance thermometry to measure thermal properties. These were fashioned from Wollaston process wire. This consists of a thin platinum/5% rhodium core (about 5 pm in diameter) surrounded by a thick (about 35 pm) silver sheath. The total diameter of the wire is thus about 75 pm. A length of wire is formed into a V and the silver is etched away at the apex to reveal a small loop of Pt/Rh which acts as a miniature resistance thermometer (Figure 2(a)). A bead of epoxy resin is added near the tip to act... 

RTDs are used in a great variety of applications. At one extreme, carefully-designed platinum RTDs are used in the very definition of temperature between 13.8033 K and 961.78 °C [2], because of their potential for extreme stability and accuracy (uncertainties of better than 1 mK). At a more practical level, commercial RTDs are widely used for industrial and research applications from 14 K to around 600 - 700 C, with typical absolute accuracies of around 0.15 K to 2 K uncalibrated, or 0.1 K or better after calibration. Bare platinum RTDs also have a long and illustrious history as velocity sensors for fluid flow, a technique known as hot-wire anemometry. More recently, special RTD configurations have also been developed to measure the thermal properties of fluids and solids [7-9]. 

The second form consists of Pt metal but the iridium is present as iridium dioxide. Iridium metal may or may not be present, depending on the baking temperature (14). Titanium dioxide is present in amounts of only a few weight percent. The analysis of these coatings suggests that the platinum metal acts as a binder for the iridium oxide, which in turn acts as the electrocatalyst for chlorine discharge (14). In the case of thermally deposited platinum—iridium metal coatings, these may actually form an intermetallic. Both the electrocatalytic properties and wear rates are expected to differ for these two forms of platinum—iridium-coated anodes. 

Durable changes of the catalytic properties of supported platinum induced by microwave irradiation have been also recorded [29]. A drastic reduction of the time of activation (from 9 h to 10 min) was observed in the activation of NaY zeolite catalyst by microwave dehydration in comparison with conventional thermal activation [30]. The very efficient activation and regeneration of zeolites by microwave heating can be explained by the direct desorption of water molecules from zeolite by the electromagnetic field this process is independent of the temperature of the solid [31]. Interaction between the adsorbed molecules and the microwave field does not result simply in heating of the system. Desorption is much faster than in the conventional thermal process, because transport of water molecules from the inside of the zeolite pores is much faster than the usual diffusion process. 

The ruthenium(II) polypyridyl complexes are also popular but the brightnesses do not exceed 15,000 and thermal quenching is rather significant. This property can be utilized to design temperature-sensitive probes providing that the dyes are effectively shielded from oxygen (e.g., in polyacrylonitrile beads). Despite often very high emission quantum yields the visible absorption of cyclometallated complexes of iridium(III) and platinum(II) is usually poor (e < 10,000 M-1cm-1), thus,... 

Elemental composition Pt 85.91%, O 14.09%. The oxide may be characterized by its physical properties and by x-ray diffraction. The compound may be thermally decomposed at elevated temperatures or reduced by hydrogen to form platinum metal which may be digested with aqua regia and HCl, diluted, and analyzed by flame AA, ICP/AES or ICP/MS. 

Thermal, Combustion and Explosion Properties. Ign temperatures of 85% hydrazine hydrate in pyrex and air was found to be 292°C. Oxygen lowered the ignition point to 218°C. On platinum foil an air atmosphere gave an ignition... 

C6o fullerene surfaces were thermally functionalized with perfluoro-(3-oxo-penta-4-ene)sulfonyl fluoride and then converted into sulfonic acid derivatives by basic hydrolysis. The product mimiced the electroconductive properties of perfluorosulfonyl Nation 1100 resins. When the modified fullerence was blended with platinum nanoparticles imbedded in Nation 1100 the material was effective as electrodes in fuel cells. 

The structure of platinum dioxide and its reactions with some di, tri, and tetravalent metal oxides have been investigated. Ternary platinum oxides were synthesized at high pressure (40 kUobars) and temperature (to 1600°C). Properties of the systems were studied by x-ray, thermal analysis, and infrared methods. Complete miscibility is observed in most PtO2-rutile-type oxide systems, but no miscibility or compound formation is found with fluorite dioxides. Lead dioxide reacts with Pt02 to form cubic Pb2Pt207. Several corundum-type sesquioxides exhibit measurable solubility in PtOz. Two series of compounds are formed with metal monoxides M2PtOh (where M is Mg, Zn, Cd) and MPt306 (where M is Mg, Co, Ni, Cu, Zn, Cd, and Hg). 

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