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Electrochemical conversion of oxide spinels into high-entropy alloy
Sure, Jagadeesh,Sri Maha Vishnu,Schwandt, Carsten
, p. 133 - 141 (2019)
Single-phase equiatomic CoCrFeNi high-entropy alloy has been synthesised by direct electrochemical reduction from oxide precursors according to the concept of the FFC-Cambridge process. Metal oxide mixtures were heat treated in air to provide a blend of spinels, which was then employed as the cathode in the electro-deoxidation process. Melts of eutectic CaCl2-NaCl and pure CaCl2 were used as the electrolytes. Varying the experimental conditions in terms of processing temperature and time yielded CoCrFeNi alloys of diverse morphologies, ranging from fine dispersed powders to solid three-dimensional objects, as they are of relevance for additive manufacturing and near-net-shape fabrication. Notably, all solid alloy samples exhibited a higher hardness than calculated by the rule of mixture, despite the presence of significant residual porosity. The results highlight the versatility of the FFC-Cambridge process for alloy preparation and suggest the possibility of economically viable large-scale manufacture of steel-type high-entropy alloys.
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Venable, F. P.,Clarke, T.
, p. 306 - 310 (1895)
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Richards, T. W.,Hoenigschmid, O.
, p. 28 - 35 (1911)
Attenuated total reflectance powder cell for infrared analysis of hygroscopic samples
Lekgoathi,Le Roux
, p. 529 - 531 (2011)
An attenuated total reflectance (ATR) sample cell has been designed, manufactured and subsequently used for the mid-infrared analysis of hygroscopic samples. This sample cell was installed as a simple drop-in replacement for the cell supplied with our commercially available Harrick Mvp-Pro FTIR-ATR accessory. Calcium chloride, a well-known desiccant that has a propensity to absorb water into its crystal lattice, was selected as non-infrared active substrate to accentuate the efficacy of the cell in preserving the anhydrous state of the sample by straightforward monitoring of the water bands. In contrast, mid-infrared spectra are presented that qualitatively demonstrate the rapid rate at which atmospheric moisture is incorporated into the anhydrous sample when analyzed using the conventional ATR cell assembly.
Richards, T. W.,Hoenigschmid, O.
, (1911)
The crystal chemistry of ca10-y(sio4) 3(so4)3cl2-x-2yfx ellestadite
Fang, Yanan,Ritter, Clemens,White, Tim
, p. 12641 - 12650 (2011)
Fluor-chlorellestadite solid solutions Ca10(SiO 4)3(SO4)3Cl2 -xFx, serving as prototype crystalline matrices for the fixation of hazardous fly ash, were synthesized and characterized by powder X-ray and neutron diffraction (PXRD and PND), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The lattice parameters of the ellestadites vary linearly with composition and show the expected shrinkage of unit cell volume as fluorine (IR = 1.33 A) displaces chlorine (IR = 1.81 A). FTIR spectra indicate little or no OH- in the solid solutions. All compositions conform to P63/ m symmetry where F- is located at the 2a (0, 0, 1/4) position, while Cl- is displaced out of the 6h Ca(2) triangle plane and occupies 4e (0, 0, z) split positions with z ranging from 0.336(3) to 0.4315(3). Si/S randomly occupy the 6h tetrahedral site. Ellestadites rich in Cl (x ≤ 1.2) show an overall deficiency in halogens (a result of CaCl2 volatilization, with charge balance achieved by the creation of Ca vacancies (Ca2+ + 2Cl- →□Ca+ 2□lC) leading to the formula Ca10-y(SiO 4)3(SO4)3Cl2- x-2yFx. For F-rich compositions the vacancies are found at Ca(2), while for Cl-rich ellestadites, vacancies are at Ca(1). It is likely the loss of CaCl2 which leads tunnel anion vacancies promotes intertunnel positional disorder, preventing the formation of a P21/b monoclinic dimorph, analogous to that reported for Ca10(PO 4)6Cl2. Trends in structure with composition were analyzed using crystal-chemical parameters, whose systematic variations served to validate the quality of the Rietveld refinements.
ION SENSOR
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, (2016/07/05)
Provided is a compound useful as a polyvalent metal ion sensor for calcium ions or the like which is capable of reversible sensing and of being integrated into a device, and an ion sensor using the compound. A copolymer comprising: a repeating unit (A) ha