Supergravity Fields Research Articles

E theory in seven dimensions

We construct the nonlinear realisation of the semi-direct product of [Formula: see text] and its vector representation in its decomposition into the subalgebra [Formula: see text] to find a seven-dimensional theory. The resulting equations of motion essentially follow from the Dynkin diagram of [Formula: see text] and if one restricts them to contain only the usual fields of supergravity and the derivatives with respect to the usual coordinates of space–time then these are the equations of motion of seven-dimensional supergravity.

Rapid fabrication of W–Cu composites via low-temperature infiltration in supergravity fields

Herein, we propose a novel method for fabricating tungsten–copper (W–Cu) composites via a supergravity technique that mainly consists of three steps: briquetting, sintering, and supergravity-enhanced infiltration. Through this approach, W–20 wt% Cu composites with a homogeneous microstructure and fascinating properties were successfully fabricated in only 5 min at a relatively low temperature of 1150 °C. The effects of the gravity coefficient, centrifugation time, and infiltration atmosphere on the infiltration process and quality of the composites were investigated individually, and the relevant optimized parameters were determined. The infiltration mechanism in supergravity fields was also discussed in detail. As a result, it is discovered that the penetration of the liquid copper into the porous tungsten skeleton was significantly accelerated in supergravity fields. Full infiltration was obtained in a short time of 5 min when the gravity coefficient was over 500. An increase in the gravity coefficient effectively improved the densities, hardness values, and thermal conductivities of the obtained W–Cu composites. Overall, we believe that our findings can assist the development of high-quality W–Cu composites that can be useful for various applications.

Efficient separation of lead and antimony metals from the Pb-Sb alloy by super-gravity technology

The Pb-Sb alloy was obtained during the pyrometallurgical processing of jamesonite (Pb4FeSb6S14). To effectively separate lead and antimony metals from the Pb-Sb alloy, an innovative approach of super-gravity technology was introduced in the current study. The super-gravity technology plays a significant role in enhancing mass transfer and phase migration of heterogeneous phases as the interfacial tension between different phases will become insignificant. The theoretical calculation of separating efficiencies based on the lever principle of Pb-Sb phase diagram was investigated. The effect of the super-gravity field on Pb-Sb alloys and the corresponding mechanism of filtrating were discussed. With the help of scanning electron microscopy-energy dispersive spectroscopy, metallographic microscopy and X-ray diffraction methods, it demonstrated that the lead phase migrated to the bottom of the sample along the super-gravity direction, whereas almost all of the antimony-rich phase accumulated along the opposite direction. As a step further, the Pb-Sb alloy was separated effectively by the filter in the super-gravity field, and the separating efficiency increased with the increasing of the gravity coefficient (G) within the range of G ≥ 50. With an optimized separation condition T = 533K (260 °C), G = 450, dpore = 48 μm and t = 210 s, the mass fraction of Pb in the filtrated lead phase reached 85 wt%, which was close to the theoretical separation value 88.8 wt% based on the phase diagram of the Pb-Sb alloy, and the mass fraction of Sb in the residue antimony-rich phase exceeded 91 wt%.

Supergravity process for enriching and separating Ag from Sn–Ag–Zn melts

The feasibility of applying supergravity technology to enhance desilverization of crude Sn with Zn was studied using the model Sn–1.5Ag–xZn alloys. The solidification characteristics of the alloys were examined using differential scanning calorimetry and scanning electron microscopy. In addition, the effect of the supergravity field on the enrichment and separation behavior of Ag in the alloy samples was investigated. Upon cooling, Ag–Zn compounds crystallized first from the alloy melts, followed by the proeutectic Sn phase and Sn–Zn eutectic phase. A greater number of Ag–Zn compounds were formed with increasing Zn content. After supergravity enrichment, the Ag–Zn compounds were concentrated at the bottom of the samples. The Ag content gradually increased along the supergravity direction, and the distribution gradient of Ag in the sample became steeper with increasing gravity coefficient (G). The Ag–Zn compounds were effectively separated from the alloy melt by filtration under supergravity fields. After separating the Sn–1.5Ag–7.5Zn alloy at 230 °C and G = 400, Ag content of molten Sn which passed through the filter was decreased by 15.6 times to 0.102 wt%, while the majority of the Ag–Zn compounds were retained by the filter, resulting in a 93.6% separation rate of Ag.

Effect of super gravity on successive precipitation and separation behaviors of rare earths in multi-components rare-earth system

Re-concentrate is a complex multi-components Re-system consisting of Ce, La, Pr and Nd, which brings great difficulties for investigating the transformation and separation behaviors of REEs. The effect of super-gravity field on the mass transfer and phase separation behaviors of REEs was investigated in this paper, and the phenomenon of successive precipitation and separation of REEs was discovered. The Re3+ was firstly precipitated into Re-oxyfluoride phase with OF3-, which overcame the interface tension to be evidently separated into the bottom layer under the action of super gravity. Subsequently, the Re3+ were successively precipitated with FeO33-, SiO44- and PO43- into Re-ferrate phase and britholite phase, which were separated further into the middle and top layers along the super gravity direction. Moreover, various REEs were efficiently recovered into the different Re-phases, respectively. The theoretical and experimental results verified the significant enhancement of super gravity on the mass transfer and phase separation of REEs, and its efficient application in REEs recovery from multi-component Re-system.

Enhanced electrodeposition and separation of metallic Cr from soluble K2CrO4 on a liquid Zn cathode

Abstract Carbon contamination and the formation of low-valence oxides limit the preparation of refractory metals by molten salt electrolysis. In this paper, a liquid Zn cathode is adopted for the electrochemical reduction of soluble K2CrO4 to metallic Cr in CaCl2-KCl molten salt. It is found that CrO42- can be directly electrochemically reduced to Cr via a six-electron-transfer step and low-valence Cr oxides is hardly produced. The reduction rate is obviously increased from 16.7 mgCr h−1 cm−2 on the solid Mo cathode to 58.7 mgCr h−1 cm−2 on liquid Zn cathode. The electrodeposited Cr is distributed in liquid Zn cathode. Carbon contamination is effectively avoided due to the negligible solubility of carbon in the liquid Zn cathode. Furthermore, Cr can be effectively separated and enriched to the bottom of liquid Zn under super-gravity field, realizing the efficient acquisition of metallic Cr and recycling of liquid Zn. The method herein provides a promising route for the preparation of refractory metals with high-purity by molten salt electrolysis.

A Kaluza–Klein Approach to Double and Exceptional Field Theory

AbstractWe examine the challenge of viewing all the fields in supergravity as arising from a Kaluza–Klein like dimensional reduction of some higher‐dimensional theory. This gives rise to what is known as exceptional field theory or double field theory. A particular emphasis is placed on following the Kaluza–Klein intuition leading to the identification of charged states and a reinterpretation of the central charges. We further give a description of the novel extended geometry as a generalised phase space and the relationship to string and M‐theory theory and the notion of quantization.

Effect of current density and cobalt concentration on the characteristics of Ni[sbnd]Co coatings prepared by electrodesposition with a supergravity field

A supergravity field offers several advantages during electrodeposition. Electrodeposition assisted by a supergravity field was employed to produce nickel–cobalt (NiCo) alloy coatings. The grain size, surface morphology, preferred crystal orientation, microhardness and wear resistance of the deposited NiCo coatings were studied systematically, and all were found to be dependent on the Co concentration in the plating bath and current density. Under a supergravity field, the surface morphology was found to be smoother than that obtained in a normal gravity field. Grain sizes of the as-prepared NiCo coatings were refined, and an average grain size of 15 nm was obtained. A Co content of 40.56 wt% was obtained using a low Co concentration in the bath. NiCo alloy coatings with a maximum microhardness of 660 HV were prepared, and the hardness value was significantly higher than that for coatings prepared by conventional electrodeposition. A minimum friction coefficient of 0.14 and a very low wear weight loss of 2.5 mg were achieved in our experiments.

Effects of Electrodeposition Time on Ni/rGO Composite Electrode as an Efficient Catalyst for Hydrogen Evolution Reaction in Alkaline Media

Background: Ni/rGO composite electrode has been fabricated by facile supergravity electrodeposition as a low-cost catalyst for efficient hydrogen evolution in alkaline media. In this paper, the electrodeposition time is the main research variable. When the electrodeposition time is 100 minutes, the Ni/rGO-100 catalyst manifests the highest electrocatalytic activity toward the hydrogen evolution reaction (HER). In 1.0 M NaOH solution, the overpotential at a current density of 100 mA cm-2, Tafel slope and charge transfer resistance of Ni/rGO-100 catalyst is 184 mV, 77 mV dec-1 and 4.173 Ω, respectively. In addition, Ni/rGO-100 catalyst shows a long-term durability at a constant current density of 100 mA cm-2 for 10 h. The outstanding HER electrocatalytic performance of the Ni/rGO-100 is mainly related to the synergetic combination of Ni and rGO, as well as the enlarged exposure of catalytically active sites and improved transport of electrons arising from the good conductivity of graphene. Method: In a classic experiment, GO was prepared by modified Hummers method. The Ni/rGO composite electrodes were prepared by supergravity electrodeposition, which has been reported in detail in our published paper. Firstly, a ø10 cm × 2 cm Ni foam circle was cleaned sequentially in HCl solution (15%), acetone and DI water for 5 min with ultrasonication to be used as a cathode. And a pure nickel pipe was used as anode. The Ni/rGO composite cathodes were electrodeposited in a blackish green plating bath which contained 350 g L-1 Ni(NH2SO3)2·6H2O, 10g L-1 NiCl2·6H2O, 30 g L-1 NH4Cl , 1.0 g L-1 GO colloidal solution with different electrodeposition time, 10min, 30min, 60min, 80min, 100min, respectively. The pH value of the plating bath is 3.5-3.8. The above five electrodes were respectively denominated as Ni/rGO-10, Ni/rGO-30, Ni/rGO-60, Ni/rGO-80, Ni/rGO-100. All composite electrodes were performed under the strength of the supergravity with G=350 g at a current density of 3 A dm-2 at 318 K. Afterwards the Ni foam coated with Ni/rGO hybrid was taken out of the reaction vessel, followed by washing with deionized water to remove physical adsorption residua, and then dried at 80°C. Results: In this paper, the electrodeposition time is the main research variable. When the electrodeposition time is 100 minutes, the Ni/rGO-100 catalyst manifests the highest electrocatalytic activity toward the hydrogen evolution reaction (HER). In 1.0 M NaOH solution, the overpotential at a current density of 100 mA cm-2, Tafel slope and charge transfer resistance of Ni/rGO-100 catalyst is 184 mV, 77 mV dec-1 and 4.173 Ω, respectively. Conclusion: In summary, we have synthesized a class of composite electrodes (Ni/rGO) for HER in alkaline solution by electrodeposition under supergravity field. We studied the effect of electrodeposition time on electrode performance in detail. With the increase of electrodeposition time, the number of active sites is enlarged provided by the electrode. When the electrodeposition time is 100 min, we fabricate the best electrode (Ni/rGO-100). The η100, Tafel slope and charge transfer resistance of Ni/rGO-100 is 184 mV, 77 mV dec-1 and 4.173 Ω, respectively. The introduction of graphene and supergravity field plays a key role in improving the performance of the electrodes. This work is a pivotal part of the development of Ni/rGO as a non-precious HER catalyst for green energy field.

A green method for selective crystallization and extraction of suanite (Mg2B2O5) crystals from boron bearing slag under super-gravity

A green method was proposed for selective crystallization and extraction of suanite crystals from boron bearing slag for ceramics reinforced phase under super-gravity. Through investigating crystallization behavior of boron bearing slag melt, olivine (Mg2SiO4) and suanite (Mg2B2O5) crystals were precipitated successively at various temperature ranges of 1623-1473 K and 1473-1323 K. Hence, selective crystallization conditions for the last precipitated suanitie crystals were investigated and two-step separation of suanite crystals from boron bearing slag was conducted in a super-gravity field. Firstly, the mixture of suanite and olivine crystals was separated from slag melt at crystallization temperature of suanite. Subsequently, the molten suanite phase was separated further from olivine crystals at melting temperature of suanite, which precipitated further into suanite crystals after cooling process. Accordingly, high-purity suanite crystals were efficiently attained from boron bearing slag, providing an essential ceramics reinforced phase for ceramic-metallic composite material and glass ceramic.

Phase Separation of Fe-Cu-Pb Alloy and Recycling of Mixed Metals in Waste Printed Circuit Boards

The pyrolysis experiment was carried out on the waste printed circuit boards (WPCBs) of mobile phones to obtain the mixed metals which contains more than ten valuable metals. The main components in the mixed metals are elements Fe, Cu, Pb, Sn. The liquid-liquid phase separation behavior of (Fe0.4Cu0.6)100-xPbx ternary alloy has been studied. The introduction of Pb into the metastable immiscible Fe-Cu alloy can result in a stable liquid-liquid phase separation into L(Fe) and L(Cu,Pb) liquids. With the increasing of Pb content, the second phase separation in the residual L(Cu,Pb) liquid was detected, resulting in the formation of three-zone-separation structure. On this basis, a hierarchical separation system was designed to recycle mixed metals in super gravity field. The results show that the metals Cr, Co, Ni, Si are mainly enriched in the Fe-rich zone, the precious metals Au, Ag and a small amount of Zn are concentrated in the Cu-rich zone, while the low-melting-point metals Sn, Bi, Cd, and In are collected in the Pb-rich zone.

Classical Yang-Baxter equation from \u03b2-supergravity

Yang-Baxter deformations of superstring σ-models have recently inspired a supergravity solution generating technique. Using the open/closed string map and a Killing bi-vector as a deformation parameter, new solutions can be built, such that the (generalised) supergravity field equations were conjectured to always reduce to the classical Yang-Baxter equation (CYBE) [1]. In this work we provide a proof of this conjecture, using a systematic approach based on the so-called β-supergravity, which is a dynamical theory for the field βmn instead of the NSNS 2-form bmn.

Liquid-liquid hierarchical separation and metal recycling of waste printed circuit boards.

Waste electrical and electronic equipment is rapidly increasing worldwide, resulting in a large quantity of waste printed circuit boards (WPCBs). There is a great challenge on how to efficiently separate mixed metals in WPCBs, which consists of more than 10 elements including hazardous Cr, Pb and Cd. In this work, based on atomic interactions, a method of liquid-liquid hierarchical separation is developed to separate the mixed metals dissociated from the pyrolyzed WPCBs of mobile phones. The hierarchical separation of L→LFe-rich + LCu,Pb-rich, LCu,Pb-rich→LCu-rich + LPb-rich and LPb-rich→SCu-dendritical + L'Pb-rich produces four immiscible Fe-rich, Cu-rich, Cu-dendritical and Pb-rich substances. The separation rate between these substances can reach more than 96% in a super-gravity field of G = 1000g. Other metals selectively distribute in the four substances. The Fe-rich substance collects Cr, Co, Ni and Si. Almost all of Au and Ag are trapped in the Cu-rich and Cu-dendritical substances. The low-melting-point metals, i.e. Bi, Cd, In and Sn, are located in the Pb-rich substance. This work provides a green shortcut for efficiently separating and recycling overall metals in WPCBs.

Ten-dimensional lifts of global supersymmetry on curved spaces

Admissible curved space backgrounds for four-dimensional supersymmetric field theories are determined by solving Killing spinor equations of four-dimensional off-shell supergravities. These can be obtained by combining ten-dimensional type IIB supersymmetry with D-brane kappa-symmetry and identifying auxiliary fields of the four-dimensional supergravity fields in terms of type IIB fields. In this paper we show how to extend a number of solutions of four-dimensional Killing spinor equations with four or less supercharges to solutions of the ten-dimensional supersymmetry constraints.

Unifying Type-II Strings by Exceptional Groups.

We construct the exceptional sigma model: a two-dimensional sigma model coupled to a supergravity background in a manifestly (formally) E_{D(D)}-covariant manner. This formulation of the background is provided by exceptional field theory (EFT), which unites the metric and form fields of supergravity in E_{D(D)} multiplets before compactification. The realization of the symmetries of EFT on the world sheet uniquely fixes the Weyl-invariant Lagrangian and allows us to relate our action to the usual type-IIA fundamental string action and a form of the type-IIB (m, n) action. This uniqueness "predicts" the correct form of the couplings to gauge fields in both Neveu-Schwarz and Ramond sectors, without invoking supersymmetry.

Ni(OH)2/CNTs/graphene composite with 3D hierarchical structure for supercapacitors with high performance

After twice heat-treating and ball-milling, the dimension of CNTs is shorter and the ends are open. By using the treated CNTs, graphene, and Ni(NO3)2, Ni(OH)2/CNTs/graphene ternary composites were synthesized through galvanostatic electrodeposition under supergravity field. The ternary composite presents a 3D hierarchical structure, in which graphene as the substrate primarily plays a role of external connection and conduction, while CNTs mainly have an effect on internal conduction. Ni(OH)2 flower spheres are distributed on the graphene nanosheets. The composite shows excellent performance of supercapacitance due to its special structure. The specific capacitance of Ni(OH)2/CNTs/graphene is 2868.5 F g−1 at a current density of 0.5 A g−1, which is much higher than Ni(OH)2, Ni(OH)2/graphene, and Ni(OH)2/CNTs. In addition, it still could reach 1247.9 F g−1 at a current density of 4 A g−1. This approach will be significant for the development of energy storage materials with high performance.

Type IIB 7-branes in warped AdS6: partition functions, brane webs and probe limit

We study Type IIB supergravity solutions with spacetime of the form AdS6×S2 warped over a Riemann surface Σ, where Σ includes punctures around which the super-gravity fields have non-trivial SL(2, R) monodromy. Solutions without monodromy have a compelling interpretation as near-horizon limits of (p, q) 5-brane webs, and the punctures have been interpreted as additional 7-branes in the web. In this work we provide further support for this interpretation and clarify several aspects of the identification of the supergravity solutions with brane webs. To further support the identification of the punctures with 7-branes, we show that punctures with infinitesimal monodromy match a probe 7-brane analysis using κ-symmetry. We then construct families of solutions with fixed 5-brane charges and punctures with finite monodromy, corresponding to fully back-reacted 7-branes. We compute the sphere partition functions of the dual 5d SCFTs and use the results to discuss concrete brane web interpretations of the supergravity solutions.

Rapid Separation of Copper Phase and Iron-Rich Phase From Copper Slag at Low Temperature in a Super-Gravity Field

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

AdS2 \xd7 S6 versus AdS6 \xd7 S2 in Type IIB supergravity

We obtain the complete local solutions with 16 supersymmetries to Type IIB supergravity on a space-time of the form AdS2 × S6 warped over a Riemann surface Σ in terms of two locally holmorphic functions on Σ. We construct the general Ansatz for the bosonic supergravity fields and supersymmetry generators compatible with the SO(2, 1) ⊕ SO(7) isometry algebra of space-time, which extends to the corresponding real form of the exceptional Lie superalgebra F (4). We reduce the BPS equations to this Ansatz, obtain their general local solutions, and show that these local solutions solve the full Type IIB supergravity field equations and Bianchi identities. We contrast the AdS2 × S6 solution with the closely related AdS6 × S2 case and present our results for both in parallel. Finally, we present a preliminary analysis of positivity and regularity conditions for AdS2 × S6, but postpone the construction of globally regular solutions to a subsequent paper.

Supergravity separation of Pb and Sn from waste printed circuit boards at different temperatures

Printed circuit boards (PCBs) contain many toxic substances as well as valuable metals, e.g., lead (Pb) and tin (Sn). In this study, a novel technology, named supergravity, was used to separate different mass ratios of Pb and Sn from Pb–Sn alloys in PCBs. In a supergravity field, the liquid metal phase can permeate from solid particles. Hence, temperatures of 200, 280, and 400°C were chosen to separate Pb and Sn from PCBs. The results depicted that gravity coefficient only affected the recovery rates of Pb and Sn, whereas it had little effect on the mass ratios of Pb and Sn in the obtained alloys. With an increase in gravity coefficient, the recovery values of Pb and Sn in each step of the separation process increased. In the single-step separation process, the mass ratios of Pb and Sn in Pb–Sn alloys were 0.55, 0.40, and 0.64 at 200, 280, and 400°C, respectively. In the two-step separation process, the mass ratios were 0.12 and 0.55 at 280 and 400°C, respectively. Further, the mass ratio was observed to be 0.76 at 400°C in the three-step separation process. This process provides an innovative approach to the recycling mechanism of Pb and Sn from PCBs.