Spin distillation cooling of ultracold Bose gases

We study the spin distillation of spinor gases of bosonic atoms and find two different mechanisms in $${}^{52}$$ 52 Cr and $$^{23}$$ 23 Na atoms, both of which can cool effectively. The first mechanism involves dipolar scattering into initially unoccupied spin states and cools only above a threshold magnetic field. The second proceeds via equilibrium relaxation of the thermal cloud into empty spin states, reducing its proportion in the initial component. It cools only below a threshold magnetic field. The technique was initially demonstrated experimentally for a chromium dipolar gas (Naylor et al. in Phys Rev Lett 115:243002, 2015), whereas here we develop the concept further and provide an in-depth understanding of the required physics and limitations involved. Through numerical simulations, we reveal the mechanisms involved and demonstrate that the spin distillation cycle can be repeated several times, each time resulting in a significant additional reduction of the thermal atom fraction. Threshold values of magnetic field and predictions for the achievable temperature are also identified.

Recalculations between different expressions of stable HCNOS isotope results – is it easy?

<p>The stable HCNOS isotope compositions can be reported in various ways depending on scientific domain and needs. The most common notations are 1) the isotope ratio of two stable isotopes; 2) isotope delta value, and 3) atom fraction of one or more of the isotopes. Frequently recalculations between these notations are required for certain applications, particularly when merging different data sets. All these recalculations require using the absolute isotope ratio for the zero points of the stable isotope delta scales (<em>R<sub>std</sub></em>). However, several <em>R<sub>std</sub></em> with very contrasting values have been proposed over time and there is no common agreement on which values should be used word-wide (Skrzypek and Dunn, 2020a).</p><p>Differences in the selection of <em>R<sub>std</sub></em>value may lead to significant differences between different data sets recalculated from delta value to other notations. These differences in R<sub>std</sub> have a significant influence also on the normalization of raw values but only when the normalization is conducted versus the working standard gas value. We proposed a user-friendly EasyIsoCalculator (http://easyisocalculator.gskrzypek.com) that allows recalculation between the main expressions of isotope compositions using various <em>R<sub>std</sub></em> and aids for identification of potential inconsistencies in recalculations (Skrzypek and Dunn, 2020b).</p><p> </p><p>Skrzypek G., Dunn P. 2020a. Absolute isotope ratios defining isotope scales used in isotope ratio mass spectrometers and optical isotope instruments. Rapid Communications in Mass Spectrometry 34: e8890.</p><p>Skrzypek G., Dunn P., 2020b. The recalculation of the stable isotope expressions for HCNOS – EasyIsoCalculator. Rapid Communications in Mass Spectrometry 34: e8892.</p>

Laser Sealing for Vacuum Plate Glass with PbO-TiO2-SiO2-RxOy Solder

Laser sealing for vacuum plate glass is a key step in developing the cost-effective smart vacuum-glass window for the drive towards net-zero energy buildings. In this paper, the pores, cracks, and interface with laser welding are analyzed in depth using PbO-TiO2-SiO2-RxOy system sealing solder to prepare vacuum flat glass. The microstructure of the sealing layer was analyzed by a BX41M-LED metallographic microscope, and the interfacial bonding characteristics were observed by thermal field emission scanning electron microscopy (SEM). The solder was analyzed by an energy spectrometer, and the influence of laser power, sealing temperature, and sealing speed on the gas holes and the crack sand interface separation of the sealing layer are reported. The results show that when the laser power reached 80 W at the welding speed of 2 mm/s, the bulk solder disappeared to most of the quantity and the sealing surface density was higher, due to which negligible pores and micro cracks were found. Thus, the sealing quality of the sealing layer is considered to be suitable when the temperature of 470 °C was maintained and the solder has 68.93% of Pb and 3.04% Si in the atom fraction to achieve the wet the glass substrate surface whilst improving the bonding quality.

Effect of Compositions, Crystal Structures and Morphologies on Photo-Luminescent Property of LaPO4:Gd3+

Various LaPO4:Gd3+ samples were synthesized by the hydrothermal method under different conditions to investigate the influence of crystalline structures, compositions and morphologies on the photo-luminescence. The compositions, crystal structures and morphologies were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and photo-luminescence emission spectrum (PL). The results revealed that the emission intensity of LaPO4:Gd3+ reached the maximum value as the mass percentage concentration of Gd3+ ions ascended to 3%. Monoclinic LaPO4:Gd3+ had stronger emission intensity than hexagonal sample which had more zeolitic water, higher symmetry and lower crystallinity. The nanospheres which dispersed better and had higher uniformity and surface atom fraction had the stronger PL intensity than the nanorods. It has been found that the La0.97Gd0.03PO4, which was prepared under the condition of pH=1, T=20 °C and excess PO43-, performed the best PL property after heat treatment at 900 °C for 4h.

Effect of Homogenization Annealing on Microstructure and Property of Cu-7.5Ni-5Sn Alloy

The microstructure and properties of Cu-7.5Ni-5Sn alloy after homogenization treatment was investigated. The research results show that homogenization treatment can obviously eliminate dendritic segregation in Cu-7.5Ni-5Sn alloy. The temperature of homogenization annealing has a great influence than the effect of holding time. The ingots of Cu-7.5Ni-5Sn alloy which were homogenization treated at 780°C for 24 hours can be rolled up to 30% deformation by cold-rolling. Some tiny white matter is still remaining in dendrite boundary, but atom fraction of Ni and Sn of the dendritic segregation is decreased by 12.04% and 4.73% respectively compare with casting state. The electrical conductivity and Brinell hardness of Cu-7.5Ni-5Sn alloy homogenization treated at 800°C for 24 hours is 12.8%IACS and 132Hv, and increases 18.5% and 29.9% respectively.

Atomic-Scale Computer Simulation for early Precipitation Process of Ni75AlXV25-X Alloy with Middle Al Composition

The microscopic phase field approach was applied for modeling the early precipitation process of Ni75AlxV25-xalloy. Without any a prior assumption, this model can be used to simulate the temporal evolution of arbitrary morphologies and microstructures on atomic scale. Through the simulated atomic pictures, calculated order parameters and volume fraction of the θ (Ni3V) and γ′ (Ni3Al) ordered phases, Ni75AlxV25-xalloys with Al composition of 0.05, 0.053 and 0.055 (atom fraction) were studied. Results show: For these alloys, θ and γ′ precipitated at the same time. With the increase of Al content, the amount of γ′ phase is increasing and that of θ phase is decreasing; the precipitation characteristic of γ′ phase transforms from Non-Classical Nucleation and Growth (NCNG) to Congruent Ordering + Spinodal Decomposition (CO+SD) gradually, otherwise, the precipitation characteristic of θ phase transforms from Congruent Ordering + Spinodal Decomposition (CO+SD) to Non-Classical Nucleation and Growth (NCNG) mechanism gradually. Both θ and γ′ has undergone the transition process of mixture precipitation mechanism with the characteristic of both NCNG and CO+SD mechanism. No incontinuous transition of precipitation mechanism has been found.

Oxidation Behavior of Fe-Y Coatings Deposited by Magnetron Sputtering

By means of magnetron sputtering, the Fe-Y coatings containing 15.4%, 20.7% and 32.7% Y (atom fraction), were deposited on stainless steels. The sputtered coatings were investigated by discontinuous weigh measurement. The results indicate that the oxidation kinetics can be divided into three stages, of which the first and second stages obey the parabolic rate law, while the oxidation kinetic curves of the last stage nearly exhibits horizontal lines. With the increase of the content of Y, the oxidation rate obviously increases. The external scale of the three kinds of alloys is substantially similar. After 24-h oxidation at 800 °C under 1 atm of air, the surface of sputtered coating is mainly transformed into three types of oxide scales, of which the thin outermost layer was Fe2O3, the innermost is YFeO3 mixed with double oxides including FeO or Fe3O4. Single Y2O3 layer was not formed on the surface or in the alloys. The results were disscussed by taking into account the defects in the metal oxide, the self-diffusion of the elements in the alloys, and the low diffusion of yttrium in iron.

Early-Stage Oxidation Behavior of γ'-Ni3Al-Based Alloys with and without Pt Addition

The early-stage oxidation behavior of γ '-Ni3Al-based alloys of composition (in at.%) Ni-22Al and Ni-22Al with 10, 20, and 30Pt was investigated in terms of oxidation kinetics, scale evolution and resulting composition profiles during heating to 1150°C in air. Platinum addition did not appear to affect the nature of the native oxide layer present on the γ '-based alloys at room-temperature; however, it was found that the presence of increasing Pt content aided in promoting the establishment of a continuous Al2O3 scale during heating the γ '-based alloys through to about 700°C. This beneficial effect can be primarily ascribed to the fact that Pt is non-reactive and its addition decreases the chemical activity of aluminum in γ '. Related to the latter, Pt partitions almost solely to the Ni sites in the ordered L12 crystal structure of γ ', which has the effect of increasing the Al:Ni atom fraction on a given crystallographic plane containing both Al and Ni. Such an effective Al enrichment at the γ ' surface would kinetically favor the formation of Al2O3 relative to NiO. A further contributing factor is that the Pt-containing γ '-based alloys showed subsurface Pt enrichment during the very early stages of oxidation. This enrichment would reduce Ni availability and increase the Al supply to the evolving scale, thus kinetically favoring Al2O3 formation.

Alloy Corrosion

The corrosion properties of alloys are of enormous practical importance: modern life would be very different without stainless steels. Alloy corrosion is also an intriguing field of scientific study that combines electrochemical kinetics with fashionable aspects of the morphological evolution of surfaces and even a dash of ancient history, via the studies of Forty and Lechtman on “depletion gilding” practiced by Early Andeans during pre-Columbian times in South America.The basic alloy corrosion process, as used by the metalsmiths to gold-coat artifacts, is de-alloying. This is defined as the selective electrolytic dissolution of one or more components from a metallic solid solution. For this to happen, there must be a significant difference in the equilibrium metal/metal-ion electrode potentials for the two metals, taking into account any complex ions that might be formed in the electrolyte. For example, we can expect de-alloying in Au-Cu alloys, but not in Au-Pt alloys.De-alloying shows sharp parting limits, expressed as critical atom percentages of the more reactive component above which that component can be removed from the alloy by electrochemical dissolution in an oxidizing environment such as nitric acid. Parting limits range from about 20 at.% to 60 at.%. This concept is still used in noble metal technology to separate noble metals from base metals. For example, an alloy of 55 at.% gold and 45 at.% silver does not de-alloy, but if it is re-melted with additional silver so that the atom fraction of Ag is greater than 60%, the gold can be separated almost completely by nitric acid immersion.