Applicability of Precipitation-Flotation Method for Differential Separation of Cadmium from Zinc in Synthesized Waste Cyanide Water

The removal of heavy metal from synthesized waste cyanide water is achievable by a precipitation-flotation method. However, the differential separation of constituting metals by this method has been thought to be very difficult. The authors found that the addition of some decomposing reagents to the synthesized waste cyanide water of cadmium and zinc can improve the separation characteristics of these metals. The present study deals with the applicability of the precipitation-flotation method for the differential separation of cadmium from zinc in synthesized waste cyanide water. The proposed method was to use sodium sulphide as a decomposing reagent in the first stage of flotation and hydrogen peroxide in the second stage in order to decompose the Cd-CN and Zn-CN complexes, respectively. Furthermore, the use of such a cation flocculant as FC-80 was considerably effective for the removal of the Cd-CN complex. Based on a series of fundamental flotation tests, actual differential flotation tests were made. The separation of cadmium from zinc in synthesized waste cyanide water was found to be satisfactory. This method can be effective for the differential separation of difficult-to-sepa-rate colloidal precipitates from liquids by the sedimentation method

Superconducting zinc heat switch for continuous nuclear demagnetization refrigerator and sub-mK experiments

We have developed and tested a zinc superconducting heat switch suitable for magnetic refrigeration and calorimetric experiments at sub-millikevin (sub-mK) temperatures. The specific application here is an adiabatic demagnetization refrigerator with two PrNi$_{5}$ nuclear stages, which can keep a temperature of 0.8 mK continuously, (CNDR) proposed by Toda et al. (J. Phys.: Conf. Ser. 969, 012093 (2018). The switch consists of six high-purity zinc foils of 0.25 mm thick which contact seven silver foils by diffusive bonding. The silver foils are electron beam welded to silver rods that are thermal links to other components. The choice of the thin zinc foils is due to reduce the magnetic latent heat on switching and the contact thermal resistance under a constraint on the aspect ratio of the switch element. The measured thermal conductance of the whole switch assembly in the normal (closed) state, $K_\mathrm{closed}$, agrees very well down to 70 mK with the value estimated from the residual electrical resistance 114 n$\mathrm{\Omega}$ at 4.2 K, indicating the validity of the Wiedemann-Franz law for zinc. The measured thermal conductance in the superconducting (open) state, $K_\mathrm{open}$, follows nicely the prediction from the BCS theory and approaches the value expected from the Debye model for thermal phonons near 70 mK. The heat leak through the HSW from the higher temperature side of 30 mK at most is estimated to be less than 0.5 nW, which is much lower than the expected cooling power ($= 10$ nW) of the CNDR at 0.8 mK . The switching ratio $K_\mathrm{closed}/K_\mathrm{open}$ extrapolated to 30 mK, is as high as 5$\times10^4$. All the test results meet the requirements for the CNDR and, for example, heat capacity measurements at sub-mK.Comment: 15 pages, 5 figure

Near-Infrared Extinction in The Coalsack Globule 2

We have conducted J, H, and Ks imaging observations for the Coalsack Globule 2 with the SIRIUS infrared camera on the IRSF 1.4 m telescope at SAAO, and determined the color excess ratio, E(J-H)/E(H-Ks). The ratio is determined in the same photometric system as our previous study for the rho Oph and Cha clouds without any color transformation; this enables us to directly compare the near-infrared extinction laws among these regions. The current ratio E(J-H)/E(H-Ks) = 1.91 +- 0.01 for the extinction range 0.5 < E(J-H) <1.8 is significantly larger than the ratios for the rho Oph and Cha clouds (E(J-H)/E(H-Ks) = 1.60-1.69). This ratio corresponds to a large negative index alpha = 2.34 +- 0.01 when the wavelength dependence of extinction is approximated by a power law which might indicate little growth of dust grains, or larger abundance of dielectric non-absorbing components such as silicates, or both in this cloud. We also confirm that the color excess ratio for the Coalsack Globule 2 has a trend of increasing with decreasing optical depth, which is the same trend as the rho Oph and Cha clouds have.Comment: 13 pages, 5 figures, and 2 tables, Ap

Exfoliation of single layer BiTeI flakes

Spin orbit interaction can be strongly boosted when a heavy element is embedded into an inversion asymmetric crystal field. A simple structure to realize this concept in a 2D crystal contains three atomic layers, a middle one built up from heavy elements generating strong atomic spin-orbit interaction and two neighboring atomic layers with different electron negativity. BiTeI is a promising candidate for such a 2D crystal, since it contains heavy Bi layer between Te and I layers. Recently the bulk form of BiTeI attracted considerable attention due to its giant Rashba interaction, however, 2D form of this crystal was not yet created. In this work we report the first exfoliation of single layer BiTeI using a recently developed exfoliation technique on stripped gold. Our combined scanning probe studies and first principles calculations show that SL BiTeI flakes with sizes of 100 $\mu$m were achieved which are stable at ambient conditions. The giant Rashba splitting and spin-momentum locking of this new member of 2D crystals open the way towards novel spintronic applications and synthetic topological heterostructures.Comment: 20 pages, 5 figure