Robust T_c in element molybdenum up to 160 GPa

Element superconductors with the single atoms provide clean and fundamental platforms for studying superconductivity.Although elements with d electrons are usually not favored by conventional BCS,the record superconducting critical temperature(T_(c))in element scandium(S_(c))has further ignited the intensive attention on transition metals.The element molybdenum(M_o)with a half-full d-orbital is studied in our work,which fills the gap in the study of Mo under high pressure and investigates the pressure dependence of superconductivity.In this work,we exhibit a robust superconductivity of Mo in the pressure range of 5 GPa to 160 GPa via high-pressure electrical transport measurements,the T_(c) varies at a rate of0.013 K/GPa to 8.56 K at 160 GPa.Moreover,the superconductivity is evidenced by the T_(c) shifting to lower temperature under applied magnetic fields,and the upper critical magnetic fields are extrapolated by the WHH equation and GL equation;the results indicate that the maximum upper critical magnetic field is estimated to be 8.24 T at 137 GPa.We further investigate the superconducting mechanism of Mo,the theoretical calculations indicate that the superconductivity can be attributed to the strong coupling between the electrons from the partially filled d band and the phonons from the frequency zone of 200-400 cm^(-1).

High-pressure synthesis of a ternary yttrium-sulfur hydride superconductor with a high T_(c) of approximately 235 K

Ternary hydrides have attracted considerable worldwide attention owing to their potential high-temperature superconducting phases.In contrast to previously reported alloy-based ternary hydrides,we selected the rare earth metal yttrium and light element sulfur to form new yttrium-sulfur hydride superconductors as the target at high pressure,which also linked the two categories of binary clathrate YH_(6) and covalent H_(3)S high-temperature superconductors.The rare earth metal ions served as carrier donors for the dissociation of H_(2) molecules and the formation of clathrate-like cage structures,while the light elements helped stabilize the materials.By applying high-pre ssure and high-temperature conditions,two possible ternary hydride s,i.e.,Im3m-(Y,S)H_(6+δ) and I4/mmm-(Y,S)H_(4+δ),were discovered.Im3m-(Y,S)H_(6+δ) is a ternary hydride with a record superconducting transition temperature(T_(c)) of 235 K belonging to the single-metal hydride system,exhibiting an 11% increment in T_(c) compared with binary Im3m-YH_(6).In the pressure range of 199-249 GPa,the T_(c) of this phase displayed a decreasing tendency but with an apparent slope change,indicating the possible structural distortions or electronic structure changes at 227 GPa.Concurrently,the extrapolated upper critical magnetic field H_(c2) was determined to be 85 T using the Werthamer-Helfand-Hohenberg formula at199 GPa,with a 37% increment compared with Im3m-YH6.The slight volume expansion(~3 %) of Im3m-(Y,S)H_(6+δ) compared with that of binary Im3m-YH_(6) signified the possible interstitial sites of sulfur atoms filling into the hydrogen cages.The size expansion of the center atoms might attract more hydrogen atoms to stabilize the hydrogen cages,contributing to the enhancement of T_(c) and H_(c2) in Im3m-(Y,S)H_(6+δ).The present study demonstrates that introduction of light elements is an effective way for enhancing T_(c) by forming larger hydrogen cages.

Effect of ozone on the performance of a hybrid ceramic membrane-biological activated carbon process

Two hybrid processes including ozonation-ceramic membrane-biological activated carbon （BAC） （Process A） and ceramic membrane-BAC （Process B） were compared to treat polluted raw water. The performance of hybrid processes was evaluated with the removal efficiencies of turbidity, ammonia and organic matter. The results indicated that more than 99% of particle count was removed by both hybrid processes and ozonation had no significant effect on its removal. BAC filtration greatly improved the removal of ammonia. Increasing the dissolved oxygen to 30.0 mg/L could lead to a removal of ammonia with concentrations as high as 7.80 mg/L and 8.69 mg/L for Processes A and B, respectively. The average removal efficiencies of total organic carbon and ultraviolet absorbance at 254 nm （UV254, a parameter indicating organic matter with aromatic structure） were 49% and 52% for Process A, 51% and 48% for Process B, respectively. Some organic matter was oxidized by ozone and this resulted in reduced membrane fouling and increased membrane flux by 25%-30%. However, pre-ozonation altered the components of the raw water and affected the microorganisms in the BAC, which may impact the removals of organic matter and nitrite negatively.

Spatial distribution of phosphorus forms in sediments with different distances to the estuary of the Dianchi Lake,China

Effects of human activity on the distribution of phosphorus(P)forms were investigated for the sediments and porewaters in Daqinghe Estuary of Dianchi Lake,China.The concentrations of total P(TP),inorganic-P(IP),and organic-P(Org-P),and the ratio of iron-bound P(Fe-P)/calcium-bound P(Ca-P)in the sediments decreased with the increasing distance from the sampling site to the estuary.This is probably due to the flocculant materials,e.g.,ferric and aluminous salts,usually being added in the wastewater treatment processes.The concentration of ammonia in the sediment porewaters significantly decreased with the increasing distance from the sampling site to the estuary.Both concentrations of total nitrogen and nitrogen in the sediment porewaters decreased to some content with the increasing distance from the sampling site to the estuary.However,the concentrations of nitrate,dissolved total P(DTP),and TP did not have strong relationship with the distances from the sampling sites to the estuary.Pollution load and water quantity also had an important influence on the concentrations of P in sediments and its interstitial water in estuary sedimentary area.