Understanding of mineral change mechanisms in coal mine groundwater reservoir and their influences on effluent water quality:a experimental study

This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.

Optimization of the average figure-of-merit zT in medium-entropy GeTe-based materials via entropy engineering

Entropy engineering has emerged as an effective strategy for improving the figure-of-merit zT by decelerating the phonon transport while maintaining good electrical transport properties of thermoelectric materials.Herein,a high average zT of 1.54 and a maximum zT of 2.1 are achieved in the mid-entropy GeTe constructed by Ag,Sb,and Pb alloying.At room temperature,the mid-entropy GeTe tends to be a cubic structure.And the power factor is improved from 7.7μW·cm^(-1)·K^(-2) to 16.2μW·cm·cm^(-1)·K^(-2) due to the large increase in effective mass and the optimized carrier concentration.The increasing disorder created by heavy and off-centering Ag,Sb,and Pb atoms induces strong mass/strain fluctuations and phonon scattering to decelerate the phonon transport in GeTe.A low lattice thermal conductivity is obtained in the medium-entropy GeTe-based material.Moreover,a GeTe-based thermoelectric cooler is fabricated with the cooling temperature difference of 66.6 K with the hot end fixed at 363 K.This work reveals the effectiveness of entropy engineering in improving the average zT in GeTe and shows potential application of GeTe as a thermoelectric cooler.

熵稳定热电材料

Thermoelectric technologies,which generate electricity directly from waste heat,have received considerable attention because of their potential to improve overall energy efficiency[1].The energy conversion efficiency is evaluated by a dimensionless figure-of-merit,defined as ZT=α^(2)σT/κ,whereα,σ,T,andκare the Seebeck coefficient,electrical conductivity,absolute temperature,and thermal conductivity,respectively.

Cu_(1)-B dual-active sites catalysts for the efficient dehydrogenative coupling and CO_(2)electroreduction

Dual-active sites(DASs)catalysts have positive potential applications in broad fields because of their specific active sites and synergistic catalytic effects.Therefore,the controllable synthesis and finely regulating the activity of such catalysts has become a hot research area for now.In this work,we developed a pyrolysis-etching-hydrogen activation strategy to prepare the DASs catalysts involving single-atom Cu and B on N-doped porous carbon material(Cu_(1)-B/NPC).Numerous systematic characterization and density functional theoretical(DFT)calculation results showed that the Cu and B existed as Cu-N4 porphyrinlike unit and B-N_(3)unit in the obtained catalyst.DFT calculations further revealed that single-atom Cu and B sites were linked by bridging N atoms to form the Cu_(1)-B-N6 dual-sites.The Cu_(1)-B/NPC catalyst was more effective than the single-active site catalysts with B-N_(3)sites in NPC(B/NPC)and Cu-N4 porphyrin-like sites in NPC(Cu_(1)/NPC),respectively,for the dehydrogenative coupling of dimethylphenylsilane(DiMPSH)with various alcohols,performing the great activity(>99%)and selectivity(>99%).The catalytic performances of the Cu_(1)-B/NPC catalyst remained nearly unchanged after five cycles,also indicating its outstanding recyclability.DFT calculations showed that the Cu_(1)-B-N6 dual-sites exhibited the lowest energy profile on the potential energy surface than that of sole B-N_(3)and Cu-N4 porphyrin-like sites.Furthermore,the rate-limiting step of dehydrogenation of DiMPSH on Cu_(1)-B-N6 dual-sites also showed a much lower activation energy than the other two single sites.Benefitting from the superiority of the Cu_(1)-B-N6 dual-sites,the Cu_(1)-B/NPC catalyst can also be used for CO_(2)electroreduction to produce syngas.Thus,DASs catalysts are promising to achieve multifunctional catalytic properties and have aroused positive attention in the field of catalysis.

片层组织钛合金中相界面诱导保载疲劳裂纹形成

钛合金具有比强度高、抗疲劳性能好和耐腐蚀性优异等特点,已广泛应用于航空、能源、化工和医药等领域,特别适合于制造航空发动机的压气机盘、风扇盘和叶片等部件.然而,在飞机运行过程中航空发动机部件通常受保载疲劳的影响,这会显著降低部件的使用寿命并威胁到航空安全,因此研究钛合金的保载疲劳行为至关重要.本文研究了片层组织钛合金(α板条和β板条交替排列)在室温保载疲劳过程中的裂纹形核过程.集束中的α板条和β板条变形不匹配,α板条中的位错滑移容易造成在片层界面处产生大量残余位错.界面残余位错引起的局部拉应力促进集束中微孔的形成和连接,从而产生保载疲劳裂纹.这项工作提供了片层组织钛合金在保载疲劳过程中的裂纹形核机制,同时也有助于认识片层材料的开裂行为,对材料的组织发展有指导意义.

Recipes for the Derivation of Water Quality Parameters Using the High-Spatial-Resolution Data from Sensors on Board Sentinel-2A,Sentinel-2B,Landsat-5,Landsat-7,Landsat-8,and Landsat-9 Satellites

Satellites have provided high-resolution(<100 m)water color(i.e.,remote sensing reflectance)and thermal emission imagery of aquatic environments since the early 1980s;however,global operational water quality products based on these data are not readily available(e.g.,temperature,chlorophyll-a,turbidity,and suspended particle matter).Currently,because of the postprocessing required,only users with expressive experience can exploit these data,limiting their utility.Here,we provide paths(recipes)for the nonspecialist to access and derive water quality products,along with examples of applications,from sensors on board Landsat-5,Landsat-7,Landsat-8,Landsat-9,Sentinel-2A,and Sentinel-2B.We emphasize that the only assured metric for success in product derivation and the assigning of uncertainties to them is via validation with in situ data.We hope that this contribution will motivate nonspecialists to use publicly available high-resolution satellite data to study new processes and monitor a variety of novel environments that have received little attention to date.

Fluoride removal from coal mining water using novel polymeric aluminum modified activated carbon prepared through mechanochemical process

Defluoridation of coal mining water is of great significance for sustainable development of coal industry in western China.A novel one-step mechanochemical method was developed to prepare polymeric aluminum modified powder activated carbon(PAC)for effective fluoride removal from coal mining water.Aluminum was stably loaded on the PAC through facile solid-phase reaction between polymeric aluminum(polyaluminum chloride(PACl)or polyaluminum ferric chloride(PAFC))and PAC(1:15 W/W).Fluoride adsorption on PACl and PAFC modified PAC(C-PACl and C-PAFC)all reached equilibrium within 5 min,at rate of 2.56 g mg^(-1)sec^(-1)and 1.31 g mg^(-1)sec^(-1)respectively.Larger increase of binding energy of Al on C-PACl(Al–F bond:76.64 eV and Al–FOH bond:77.70 eV)relative to that of Al on C-PAFC(Al–F bond:76.52 eV)explained higher fluoride uptake capacity of C-PACl.Less chloride was released from C-PACl than that from C-PAFC due to its higher proportion of covalent chlorine and lower proportion of ionic chlorine.The elements mapping and atomic composition proved the stability of Al loaded on the PAC as well as the enrichment of fluoride on both CPACl and C-PAFC.The Bader charge,formation energy and bond length obtained from DFT computational results explained the fluoride adsorption mechanism further.The carbon emission was 7.73 kg CO_(2)-eq/kg adsorbent prepared through mechanochemical process,which was as low as 1:82.3 to 1:8.07×10^(4)compared with the ones prepared by conventional hydrothermal methods.

Regulating the electronic structure of NiFe layered double hydroxide/reduced graphene oxide by Mn incorporation for high-efficiency oxygen evolution reaction

The development of highly efficient and costeffective oxygen evolution reaction(OER)electrocatalysts for renewable energy systems is vitally essential.Modulation of the electronic structure through heteroatom doping is considered as one of the most potential strategies to boost OER performances.Herein,a rational design of Mn-doped NiFe layered double hydroxide/reduced graphene oxide(Mn-NiFe LDH/rGO)is demonstrated by a facile hydrothermal approach,which exhibits outstanding OER activity and durability.Experimental results and density functional theory(DFT)calculations manifest that the introduction of Mn can reprogram the electronic structure of surface active sites and alter the intermediate adsorption energy,consequently reducing the potential limiting activation energy for OER.Specifically,the optimal Mn-NiFe LDH/rGO composite shows an enhanced OER performance with an ultralow overpotential of 240 mV@10 mA cm^(-2),Tafel slope of 40.0 mV dec^(-1) and excellent stability.Such superior OER activity is comparable to those of the recently reported state-of-the-art OER catalysts.This work presents an advanced strategy for designing electrocatalysts with high activity and low cost for energy conversion applications.

A stepwise-designed Rh-Au-Si nanocomposite that surpasses Pt/C hydrogen evolution activity at high overpotentials

Hydrogen evolution by electrocatalysis clean energy. However, it is challenging is an attractive method of supplying to find cheap and efficient alternatives to rare and expensive platinum based catalysts. Pt provides the best hydrogen evolution performance, because it optimally balances the free energies of adsorption and desorption. Appropriate control of these quantities is essential for producing an efficient electrocatalyst. We demonstrate, based on first principles calculations, a stepwise designed Rh-Au-Si ternary catalyst, in which adsorption （the Volmer reaction） and desorption （the Heyrovsky reaction） take place on Rh and Si surfaces, respectively. The intermediate Au surface plays a vital role by promoting hydrogen diffusion from the Rh to the Si surface. Theoretical predictions have been explored extensively and verified by experimental observations. The optimized catalyst （Rh-Au-SiNW-2） has a com- position of 2.2：28.5：69.3 （Rh：Au：Si mass ratio） and exhibits a Tafel slope of 24.0 mV.dec-L Its electrocatalytic activity surpasses that of a commercial 40 wt.% Pt/C catalyst at overpotentials above 0.19 V by exhibiting a current density of greater than 108 mA-cm-2. At 0.3 V overpotential, the turnover frequency of Rh-Au-SiNW-2 is 10.8 times greater than that of 40 wt.% Pt/C. These properties may open new directions in the stepwise design of highly efficient catalysts for the hydrogen evolution reaction （HER）.

Biomass-assisted approach for large-scale construction ofmulti-functional isolated single-atom site catalysts

In recent years,the isolated single-atom site(ISAS)catalysts have attracted much attention as they are cost-effective,can achieve 100%atom-utilization efficiency,and often display superior catalytic performance.Here,we developed a biomass-assisted pyrolysis-etching-activation(PEA)strategy to construct ISAS metal decorated on N and B co-doped porous carbon(ISAS M/NBPC,M=Co,Fe,or Ni)catalysts.This PEA strategy can be applied in the universal and large-scale preparation of ISAS catalysts.Interestingly,the ISAS M/NBPC(M=Co,Fe,or Ni)catalysts show multi-functional features and excellent catalytic activities.They can be used to conduct different types of catalytic reactions,such as O-silylation(OSI),oxidative dehydrogenation(ODH),and transfer hydrogenation(THG).In addition,we used the transfer hydrogenation of nitrobenzene as a typical reaction and revealed the difference between ISAS Co/NBPC and ISAS Co/NPC(N-doped porous carbon)catalysts by density functional theory(DFT)calculations,and which showed that the decreased barrier of the ratedetermining step and the low-lying potential energy diagram indicate that the catalytic activity is higher when ISAS Co/NBPC is used than that when ISAS Co/NPC is used.These results demonstrate that the catalytic performance can be effectively improved by adjusting the coordination environment around the ISAS.

Copper chalcogenide thermoelectric materials

Cu-based chalcogenides have received increasing attention as promising thermoelectric materials due to their high efficiency,tunable transport properties,high elemental abundance and low toxicity.In this review,we summarize the recent research progress on this large family compounds covering diamond-like chalcogenides and liquid-like Cu2X (X=S,Se,Te)binary compounds as well as their multinary derivatives.These materials have the general features of two sublattices to decouple electron and phonon transport properties.On the one hand,the complex crystal structure and the disordered or even liquid-like sublattice bring about an intrinsically low lattice thermal conductivity.On the other hand, the rigid sublattice constitutes the charge-transport network, maintaining a decent electrical performance.For specific material systems,we demonstrate their unique structural features and outline the structure-performance correlation. Various design strategies including doping,alloying,band engineering and nanostructure architecture,covering nearly all the material scale,are also presented.Finally,the potential of the application of Cu-based chalcogenides as high-performance thermoelectric materials is briefly discussed from material design to device development.

Rationally engineered Co and N co-doped WS_(2) as bifunctional catalysts for pH-universal hydrogen evolution and oxidative dehydrogenation reactions

In the field of electrolysis of water,the design and synthesis of catalysts over a wide pH range have attracted extensive attentions.In this paper,Co and N are co-introduced into the structural unit of tungsten disulfide(WS_(2)),and the hydrogen evolution reaction(HER)performances of different WS_(2)-based catalysts are theoretically predicted and systematically studied by density functional theory(DFT)calculations.With the guidance of DFT calculations,an evaporation-pyrolysis strategy is applied to prepare Co and N co-doped WS_(2)(Co,N-WS_(2))flower-like nanosheets,which exhibits excellent HER performance over a wide pH range.In addition,the DFT calculations show that the active sites in Co,N-WS_(2) have a good ability of hydrogen adsorption after the introduction of Co and N,suggesting that such a co-doping system will be an ideal catalyst for oxidative dehydrogenation(ODH).The following experiment results indeed evidence that the Co,N-WS_(2) catalyst displays a high activity in the ODH of 1,2,3,4-tetrahydroquinoline(4H-quinoline)and its derivatives.Therefore,this work provides a good example for the rational design and accurate preparation of functional catalysts,which enables it possible to develop other efficient catalysts with multiple functions.

Growth and optical properties of ytterbium and rare earth ions codoped CaF2-SrF2 eutectic solid-solution(RE=Y^(3+),Gd^(3+),La^(3+))

Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF_(2)-SrF_(2)single crystals(3 at%Yb,6 at%RE:CaF_(2)-SrF_(2))were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF_(2)-SrF_(2).The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y^(3+)<Gd^(3+)<La^(3+).The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF_(2)-SrF_(2)and Yb,Gd:CaF_(2)-SrF_(2),which are larger than 0.85 in Yb,Y:CaF_(2)-SrF_(2)and 0.80 in Yb:CaF_(2)-SrF_(2).Absorption spectra in the range of 200 and 400 nm were analysed with Yb^(2+)contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF_(2)-SrF_(2)has a relatively higher optical parameter(δem×t,0.52×10^(20)cm^(2)·ms),lower Isat(3.68 kW/cm^(2))and^min(0.50 kW/cm^(2))at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF_(2)-SrF_(2)is 302 cm^(-1)which is located between those of CaF_(2)and SrF_(2)as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y^(3+),Cd^(3+),La^(3+))codoped CaF_(2)-SrF_(2)eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.

Geochemical characteristics and metal element enrichment in crusts from seamounts of the Western Pacific

Elemental geochemistry is an essential part of understanding mineralization mechanisms. In this paper, a data set of 544 cobalt crust samples from seamounts of the Western Pacific are used to study the enrichment characteristics of metal elements. REE normalization is utilized to reveal the origin of the crusts; effects of water depth on Co enrichment and impacts ofphosphatization on mineral quality are discussed to obtain the evolution of these marine mineral deposits, which gives support to further resource assessment. Conclusions are reached as follows： 1） Elemental abundances, inter-element relation- ships, and shale-normalized REE patterns for phosphate- poor crusts from different locations reflect hydrogenetic origin of the crusts. EFs （enrichment coefficients） of REE exhibit exponential increase from surface sediments to phosphorite to polymetallic nodules to crusts, suggesting that the improved degree of hydrogeneous origin induces the enrichment of REE. 2） The crusts in the Western Pacific, formed through hotspot produced guyots trails, have relatively lower REE than those in the Mid-Pacific. The latter could be attributed to the peculiar submarine topography of seamounts formed by intraplate volcanism. 3） The non-phosphatized younger crust layers have 40% higher Co than the phosphatized older layers. This indicates the modification of the elemental composition in these crusts by phosphatization. A general depletion of hydroxide-dominated elements such as Co, Ni, and Mn and enrichment of P, Ca, Ba, and Sr is evident in phosphatized crusts, whereas non-phosphatized younger generation crusts are rich in terrigenous aluminosilicate detrital matter. 4） Co increases above the carbonate compensation depth （CCD） from less than 0.53% to over 0.65% in seamount regions with water depth of less than 2,500 m, suggesting the significance of the dissolution of carbonate in the sea water column to the growth and composition of crusts.