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Here we report targeted high-pressure synthesis of two novel high-TC hydride superconductors, P63/mmc-ThH9 and Fm3-m-ThH10, with the experimental critical temperatures (TC) of 146 K ...and 159–161 K and upper critical magnetic fields (μHC) 38 and 45 Tesla at pressures 170–175 Gigapascals, respectively. Superconductivity was evidenced by the observation of zero resistance and a decrease of TC under external magnetic field up to 16 Tesla. This is one of the highest critical temperatures that has been achieved experimentally in any compound, along with such materials as LaH10, H3S and HgBa2CaxCu2O6+z. Our experiments show that fcc-ThH10 has stabilization pressure of 85 GPa, making this material unique among all known high-TC metal polyhydrides. Two recently predicted Th-H compounds, I4/mmm-ThH4 (>86 GPa) and Cmc21-ThH6 (86–104 GPa), were also synthesized. Equations of state of obtained thorium polyhydrides were measured and found to be in excellent agreement with the theoretical calculations. New phases were examined theoretically and their electronic, phonon, and superconducting properties were calculated.
•General introduction about core–shell particles.•Synthetic methods for core–shell silica particles, particularly for HPLC.•Fundamentals on why core–shell particles perform better in HPLC.•Comparison ...of core–shell particles, totally porous particles, and monoliths.•Wide applications of core–shell particles columns.
The challenges in HPLC are fast and efficient separation for a wide range of samples. Fast separation often results in very high operating pressure, which places a huge burden on HPLC instrumentation. In recent years, core–shell silica microspheres (with a solid core and a porous shell, also known as fused-core or superficially porous microspheres) have been widely investigated and used for highly efficient and fast separation with reasonably low pressure for separation of small molecules, large molecules and complex samples. In this review, we firstly show the types of core–shell particles and how they are generally prepared, focusing on the methods used to produce core–shell silica particles for chromatographic applications. The fundamentals are discussed on why core–shell particles can perform better with low back pressure, in terms of van Deemter equation and kinetic plots. The core–shell particles are compared with totally porous silica particles and also monolithic columns. The use of columns packed with core–shell particles in different types of liquid chromatography is then discussed, followed by illustrating example applications of such columns for separation of various types of samples. The review is completed with conclusion and a brief perspective on future development of core–shell particles in chromatography.
High‐pressure packer test (HPPT) is an enhanced constant head packer test for characterizing the permeability of fractured rocks under high‐pressure groundwater flow conditions. The interpretation of ...the HPPT data, however, remains difficult due to the transition of flow conditions in the conducting structures and the hydraulic fracturing‐induced permeability enhancement in the tested rocks. In this study, a number of HPPTs were performed in the sedimentary and intrusive rocks located at 450 m depth in central Hainan Island. The obtained Q‐P curves were divided into a laminar flow phase (I), a non‐Darcy flow phase (II), and a hydraulic fracturing phase (III). The critical Reynolds number for the deviation of flow from linearity into phase II was 25−66. The flow of phase III occurred in sparsely to moderately fractured rocks, and was absent at the test intervals of perfect or poor intactness. The threshold fluid pressure between phases II and III was correlated with RQD and the confining stress. An Izbash's law‐based analytical model was employed to calculate the hydraulic conductivity of the tested rocks in different flow conditions. It was demonstrated that the estimated hydraulic conductivity values in phases I and II are basically the same, and are weakly dependent on the injection fluid pressure, but it becomes strongly pressure dependent as a result of hydraulic fracturing in phase III. The hydraulic conductivity at different test intervals of a borehole is remarkably enhanced at highly fractured zone or contact zone, but within a rock unit of weak heterogeneity, it decreases with the increase of depth.
Key Points:
The Q‐P curves by HPPTs were divided into Darcy, non‐Darcy, and fracking phases
The characteristics of Q‐P curves were correlated with the intactness of rocks
The permeability in different phases was evaluated with an analytical model
The big squeeze: On applying pressure to ZIF‐8 (0.18 GPa), solvent can be squeezed into the porous cavities, initially increasing the pore size and unit‐cell volume. On increasing pressure further to ...1.47 GPa, a phase transition takes place (see picture). This transition allows more solvent to enter the original nanopores and enlarges the narrow channels connecting these pores, resulting in higher porous volume and solvent content.
We present the results of a detailed structural study in the Cycladic Blueschist Unit at Fabrika on Syros Island, Greece, and discuss their significance for tectonic processes at the subduction ...interface. Some samples record top‐to‐the‐west shear reflecting prograde (burial), peak high‐pressure (HP) and initial decompression (exhumation) conditions. Other nearby samples record top‐to‐the‐east shear during HP metamorphism and exhumation. Some rocks re‐equilibrated at greenschist‐facies conditions and record top‐to‐the‐west shear. Greenschist‐facies top‐to‐the‐west shear is also found at the base of non‐HP upper units above the Fabrika HP sequence. We interpret the HP structures to reflect forced return flow and incipient formation of an extrusion wedge in the subduction channel. The HP top‐to‐the‐west structures resulted from thrusting along the base of the wedge and started to form during burial before the rocks reached their deepest point. The HP top‐to‐the‐east structures reflect deformation near the top of the developing extrusion wedge. After considerable exhumation during ongoing subduction, out‐of‐sequence, top‐to‐the‐west thrusts emplaced the non‐HP upper units above the exhuming extrusion wedge ~10 Myr after the wedge initially formed. Our work suggests that the HP rocks were considerably exhumed during sustained lithospheric shortening in the subduction channel by forced return flow. Because return flow is controlled by the velocity of the subducting slab, it may explain why HP rocks can be exhumed at subduction rates. On the regional scale we find that four distinct HP belts were sequentially accreted and exhumed between ~50 and 20 Ma suggesting continuous subduction‐channel return flow in the Hellenic subduction zone.
Key Points
Structures are interpreted to reflect forced return flow in subduction channel
Structures in high‐pressure and greenschist‐facies rocks indicate sustained lithospheric shortening
New and novel interpretation of subduction‐related structures in Cycladic Blueschist Unit
Two hydrogen-rich materials, H3S and LaH10, synthesized at megabar pressures, have revolutionized the field of condensed matter physics providing the first glimpse to the solution of the ...hundred-year-old problem of room temperature superconductivity. The mechanism underlying superconductivity in these exceptional compounds is the conventional electron–phonon coupling. Here we describe recent advances in experimental techniques, superconductivity theory and first-principles computational methods which have made possible these discoveries. This work aims to provide an up-to-date compendium of the available results on superconducting hydrides and explain how the synergy of different methodologies led to extraordinary discoveries in the field. Besides, in an attempt to evidence empirical rules governing superconductivity in binary hydrides under pressure, we discuss general trends in the electronic structure and chemical bonding. The last part of the Review introduces possible strategies to optimize pressure and transition temperatures in conventional superconducting materials as well as future directions in theoretical, computational and experimental research.
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Here we report the high-pressure synthesis of a series of lanthanum–yttrium ternary hydrides obtained at pressures of 170–196GPa via the laser heating of P63/mmc La–Y alloys with ...ammonia borane. As a result, we discovered several novel compounds: cubic hexahydride (La,Y)H6 and decahydrides (La,Y)H10 with a maximum critical temperature TC ∼ 253 K and an extrapolated upper critical magnetic field BC2(0) of up to 135 T at 183GPa. The current–voltage measurements show that the critical current density JC in (La,Y)H10 is 12–27.7 kA/mm2 at 4.2 K, which is comparable with that of commercial superconducting wires such as NbTi and Nb3Sn. (La,Y)H6 and (La,Y)H10 are among the first examples of ternary high-TC superconducting hydrides. Our experiments show that part of metal atoms in the structures of recently discovered Im3¯m-YH6 and Fm3¯m-LaH10 can be replaced with lanthanum (∼70%) and yttrium (∼25%), respectively, with the formation of unique ternary superhydrides containing metal-encapsulated cages La@H24 and Y@H32, which are specific for Im3¯m-LaH6 and Fm3¯m-YH10. This work demonstrates that hydrides, unstable in pure form such as LaH6 and YH10, may nevertheless be stabilized at relatively low pressures in solid solutions with superhydrides having the desired structure.
The application of high pressure favors many chemical processes, providing higher yields or improved rates in chemical reactions and improved solvent power in separation processes, and allowing ...activation barriers to be overcome through the increase in molecular energy and molecular collision rates. High pressures—up to millions of bars using diamond anvil cells—can be achieved in the laboratory, and lead to many new routes for chemical synthesis and the synthesis of new materials with desirable thermodynamic, transport, and electronic properties. On the industrial scale, however, high-pressure processing is currently limited by the cost of compression and by materials limitations, so that few industrial processes are carried out at pressures above 25 MPa. An alternative approach to high-pressure processing is proposed here, in which very high local pressures are generated using the surface-driven interactions from a solid substrate. Recent experiments and molecular simulations show that such interactions can lead to local pressures as high as tens of thousands of bars (1 bar = 1 × 105 Pa), and even millions of bars in some cases. Since the active high-pressure processing zone is inhomogeneous, the pressure is different in different directions. In many cases, it is the pressure in the direction parallel to the surface of the substrate (the tangential pressure) that is most greatly enhanced. This pressure is exerted on the molecules to be processed, but not on the solid substrate or the containing vessel. Current knowledge of such pressure enhancement is reviewed, and the possibility of an alternative route to high-pressure processing based on surface-driven forces is discussed. Such surface-driven high-pressure processing would have the advantage of achieving much higher pressures than are possible with traditional bulk-phase processing, since it eliminates the need for mechanical compression. Moreover, no increased pressure is exerted on the containing vessel for the process, thus eliminating concerns about materials failure.
Herein the ultrafine‐grained (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 high‐entropy diboride ceramics were successfully fabricated by high‐pressure sintering technology for the first time. The results showed ...that the grain size, relative density, and Vickers hardness of the as‐fabricated samples all increased gradually with increasing sintering temperatures from 1373 K to 1973 K. The relative density and mean grain size of the as‐sintered samples at 1973 K were 97.2% and 684 nm, respectively, and simultaneously they exhibited excellent comprehensive mechanical properties, combining a Vickers hardness of 26.2 GPa and a fracture toughness of 5.3 MPa·m1/2, which were primary attributed to the fine grain strengthening mechanism and microcrack deflection toughening mechanism.
The importance and challenges presented by Bacillus spores in the food industry are briefly outlined with a focus on Bacillus cereus. The structure and the mechanism of resistance exhibited by ...Bacillus spores are described, and the steps involved in their germination are included. Novel technologies, using no or only mild heat treatments, to inactivate Bacillus spores are covered, including ultraviolet radiation, pulsed electric field, and high‐pressure processing, both as stand‐alone techniques or techniques as part of a hurdle approach.
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