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[en] A method is described for welding tubes to tube sheets etc. without leaving gaps, which is easy to carry through. Inserting a centering busk, a ceramic ring, or a centering pin serves as an auxiliary means. The method is explained by the example of a heat exchanger. (GSC)
[de]Es wird ein Verfahren zum spaltlosen Einschweissen von Rohrer an Rohrplatten etc. beschrieben, das leicht durchfuehrbar ist. Als Hilfsmittel dient das Einsetzen einer Zentrierbuchse, eines Keramikringes oder eines Zentrierdorns. Das Verfahren wird am Beispiel eines Waermeaustauschers erlaeutert. (GSC)
[en] A device rendering it possible to weld pipes on pressurized elements like tube sheets, pressure vessels etc. (according to patent application no. 2452598.2-24), is described. It is characterized by the centering bush forming the guidance for a welding apparatus with exchangeable welding torch for welding the root seam, consisting of the lip and the outer lip of the pipe. Additional details of the apparatus are described. The device permits satisfactory gapless through-welding of the root seam with simple engineering means. (UWI)
[de]Es wird eine Vorrichtung beschrieben, die ermoeglicht Rohre an druckfuehrende Elemente wie Rohrplatten, Druckbehaelter etc. (nach Patentanmeldung 2452598.2-24) anzuschweissen, und die dadurch gekennzeichnet ist, dass die Zentrierbuechse die Fuehrung fuer eine Schweissvorrichtung mit auswechselbarem Schweissbrenner zum Verschweissen der Wurzelnaht - bestehend aus der Lippe und der Aussenlippe des Rohres - bildet. Weitere apparative Einzelheiten sind beschrieben. Die Vorrichtung ermoeglicht eine einwandfreie spaltlose Durchschweissung der Wurzelnaht mit konstruktiv einfachen Mitteln. (UWI)
[en] A series of mesoporous anatase-type TiO2 doped with zirconium (0-50 mol% Zr) was synthesized by combining the sol-gel process with the inverse miniemulsion technique. Nanoparticles between 100 and 300 nm were directly prepared from acidic precursor solutions of titanium glycolate (EGMT) and zirconium isopropoxide. The miniemulsion technique is a simple and convenient method to synthesize nanoparticles of homogeneous size because the reactions (here hydrolysis and condensation) take place in the confined space of nanodroplets (several hundreds of nanometres) and therefore in a highly controlled manner. For low doping levels (0-7.1 mol% Zr), ZrxTi1-xO2 solid solutions were formed where Zr was uniformly dispersed into the anatase framework. For higher amounts of zirconium (Zr ≥ 7.1 mol%), the crystallization of zirconium titanate (ZrTiO4) occurred at a low temperature of 650 deg. C and it was obtained as a pure material for 47.4 mol% ≤ Zr ≤ 50 mol%. The influence of the amount of zirconium on the crystallinity, crystallite size, phase composition and stability, morphology and specific surface area was investigated. For the characterization transmission electron microscopy (TEM), x-ray diffraction (XRD), nitrogen sorption (BET) and inductively coupled plasma-optical emission spectrometry (ICP-OES) were used. The photocatalytic activity of the crystalline mixed oxides (0-9.4 mol% Zr) was examined for the degradation of methylene blue under UV irradiation.
[en] The effect of oxidation state on phase separation was studied for 13Na2O, 49B2O3, 38SiO2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo4+ ions have a great tendency to precipitate MoO2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)
[en] Cerium(IV) oxide nanoparticles were synthesized using an inverse miniemulsion technique with cerium nitrate hexahydrate as precursor. The resulting nanocrystallites are as small as 5 nm with a specific surface area of 158 m2 g-1 after calcination at 400 deg. C. With the addition of cetyltrimethylammonium bromide (CTAB) or (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)) triblock copolymers (PEO-PPO-PEO) as template in the miniemulsion droplets, the specific surface area can be increased up to 255 m2 g-1. The miniemulsions were characterized by dynamic light scattering (DLS) and the obtained oxides were examined by x-ray diffraction (XRD), nitrogen sorption (BET and BJH), and transmission electron microscopy (TEM). The catalytic activity of the resulting ceria was investigated for the temperature-programmed oxidation (TPO) of methane.