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.

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.

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.

Mn调控NiFe LDH/rGO活性位点的电子结构作为高效水氧化催化剂

发展廉价、高效的水氧化(OER)催化剂对发展可持续能源具有重要意义.杂原子掺杂调节活性位点的电子结构提高催化剂的OER性能被认为是一种高效的策略.本文通过水热法制备得到Mn掺杂的层状镍铁氢氧化物/还原氧化石墨烯(Mn-NiFe LDH/rGO)作为高效、稳定的水氧化催化剂.实验和模拟计算研究都表明Mn能调整活性位点的电子结构,改善其对水氧化反应中中间产物的吸附能垒,从而减小OER反应中决速步骤的反应势垒.具体而言,最优的Mn-NiFe LDH/rGO复合材料在过电位仅为240 mV就能驱动10 mA cm^(-2)的电流密度,Tafel斜率低至40.0 mV dec^(-1),并且具有良好的稳定性.该催化剂优异的活性优于最近报道的OER电催化剂.本工作为制备用于能源转换领域的高活性、廉价的电催化剂提供了新的思路.

铜基硫族化合物热电材料（英文）

铜基硫族化合物因其高性能、可调的输运性质、高丰度和低毒性,被认为是很有前景的新型热电材料,引起了研究者的广泛关注.本文总结了近年来铜基热电材料的研究进展,包括类金刚石结构材料、声子液体二元及多元化合物等.本文首先总体介绍了两套亚晶格的基本特征及其对热学、电学性质的影响:一方面,复杂晶体结构和无序、甚至液态化的亚晶格导致极低的热导率;另一方面,刚性亚晶格构成电荷传输通道,保证了较高的电学性能.然后,本文针对特定的几类材料体系,详细介绍了其典型结构特征与"结构-性能"构效关系,以及掺杂、固溶、能带结构调控和纳米结构设计等多尺度优化手段.最后,本文从材料研发和器件研制的角度评述了铜基硫族化合物作为热电材料的应用前景及相关进展.

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.

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.

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.

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）.