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Structural Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
The reactor-grade zirconium metal is produced by the well-known Kroll process, which is essentially a batch process involving reduction of anhydrous zirconium chloride with magnesium. The reduction reaction, ZrCl4(g) + MG (l) → Zr (s) + MgCl2(l), is carried out in a specially designed stainless stell vessel heated externally by a three-zone resistance furnace. Zirconium chloride and clean magnesium pigs are loaded in separate containers into the reduction retort. Zirconium chloride, which has a sublimation point of 331°C, is distilled off and allowed to react with liquid magnesium maintained at a reduction temperature of about 850°C. During distillation of zirconium chloride, its in situ purification takes place with respect to oxygen (in the form of Zr0Cl2) picked up during the handling of the highly hygroscopic chloride powers. At the distilling temperature, zirconium oxychloride breaks up to yield volatile zirconium tetrachloride and zirconium oxide, which being nonvolatile, is retained in the chloride container. In the course of reduction, zirconium settles on the bottom and side walls of the crucible because of its being heavier than both magnesium chloride and reductant magnesium. Between them, the latter is heavier, which means the reductant magnesium always remains floating at the top, thereby making itself physically available for reaction with the incoming vapors of zirconium chloride. The reduction results in sintered zirconium sponge covered with magnesium chloride and excess magnesium. Zirconium sponge is separated from the reacted charge by pyrovacuum distillation in another heavy-walled retort capable of evacuation down to less than 10–3 mmHg at 900°C.
Major Melt—Crucible Systems
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
As preparation methods, heating a compound precursor in the vapour of a reducing agent or melting the metallic reducing agent in the vapour of the compound precursor often make their appearance, not only in exploratory experiments but also in industrial processes. Molten magnesium (b.p. 1091°C) reduces zirconium tetrachloride vapour in the well-known Kroll process. Lithium (b.p. 1330°C) and sodium (b.p. 883°C) are also used in chloride reductions (Jamrack 1963; Hampel 1961).
Organic and Inorganic Supramolecular Catalysts
Published in Jubaraj Bikash Baruah, Principles and Advances in Supramolecular Catalysis, 2019
UiO-66 is a robust MOF; it is formed by the reaction of zirconium tetrachloride with 1,4-benzenedicarboxylic acid. This MOF is modified through exchange of the benzene dicarboxylate by reacting with [FeFe](bdt)(CO)6 (bdt = benzenedithiolate) (2.79c). The MOF 2.79c is a good catalyst for reduction of protons. The linker-modified Fe-UiO-66 catalyses transformation of H+ to H2 under heterogeneous conditions (Figure 2.79).
Performance of Fire Extinguishing Gel with Strong Stability for Coal Mine
Published in Combustion Science and Technology, 2022
Kaili Dong, Junfeng Wang, Yulong Zhang, Zewen Liang, Qi Shi
The specific operation process is shown in Figure 1, a 20.0 wt% zirconium tetrachloride solution was prepared, and citric acid was added in a 2:1 ratio to form ZrCit solution. The ZrCit solution was then titrated with 5.0 wt% sodium hydroxide solution, producing a white precipitate. Clarifying the solution raises the pH; the target value was about 7. Once reached, the titration was stopped. Different volumes of titrated solutions were added to 1.5 wt%, 2.0 wt%, 2.5 wt% and 3.0 wt% CMC solutions. Variable mass fractions of GDL were subsequently added to the solutions and mixed evenly, resulting in a gel. Gelation time is an important parameter of polymeric gel systems. A ‘pass-funnel-time’ method is used to determine the gelation time (Hu and Xue 2011). The amounts of each component used for each experiment and gelation time are listed in Table 1.
Fabrication of ZrN Barrier Coatings for U-Mo Microspheres Via Fluidized Bed Chemical Vapor Deposition Using a Metalorganic Precursor
Published in Nuclear Technology, 2018
L. Sudderth, D. Perez-Nunez, D. Keiser, S. McDeavitt
Chemical vapor deposition (CVD) has been studied as a candidate process to create ZrN coatings on U-Mo powders.10 Achieving a uniform coating across U-xMo microspheres requires that the precursor gas has sufficient interaction with the entire surface of each particle. This may be accomplished using fluidized bed chemical vapor deposition11 (FB-CVD). A common method for producing ZrN via CVD utilizes a zirconium tetrachloride precursor with a N2/H2 mixture at a reaction temperature of 1170°C (Ref. 12). The high-temperature requirement makes this method incompatible with thermally sensitive substrates.13 The major issue with this process on uranium substrates is the corrosion of uranium metal. The metal halide reacts with uranium metal to produce uranium chloride starting at temperatures lower than the deposition reaction temperature.14
The effect of trace amount of Zr-doped TiO2 on photocatalytic activity in degradation of organic waste
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Tania Bigdeli, Shahram Moradi Dehaghi
TiO2 sample was prepared by using the sol-gel method. At first, TTIP was dissolved in absolute ethanol with molar ratio of TTIP to ethanol (1:75) and then stirred for 15 min in order to get a precursor solution; following that, 0.1 g HPC was added as a stabilizer, and the mixture was continuously stirred for 15 min to obtain a yellow transparent sol (Sol 1). After that, a mixture of absolute ethanol, Nitric acid, and CTAB (Sol 2) with molar ratios of (0.47, 0.0044, and 0.00028, respectively) was added dropwise during 30 min into the (Sol 1) by fast stirring to get a transparent sol. This sol was aged at room temperature for 48 h to form a gel. Then, it was heat treated for 30 min at 100°C to remove the solvents. Subsequently, it was calcinated in an electric furnace at the 525°C for 4 h. TiO2 nanoparticles were prepared. TiO2/Zrx(X = 0.0001, 0.0002, 0.0003, and 0.0004 mole) nano photocatalyst synthesized as the same method, but the difference is that in the preparation of (Sol 2), in this step zirconium tetrachloride (ZrCl4) dissolved in absolute ethanol with the trace molar ratios of Zr to ethanol (0.0001:1.52, 0.0002:1.52, 0.0003:1.52, and 0.0004:1.52, respectively) added to (Sol 2). After that, the process is repeated as mentioned before. Synthesized samples are summarized in Table 1).