多向压缩纯钨烧结体的组织及热稳定性（英文）

对纯度为99.9%的纯钨烧结体在1423 K进行不同压下量的多向压缩(MDC)实验,采用X射线衍射(XRD)、电子背散射衍射(EBSD)及差示扫描量热法(DSC)研究多向压缩前后纯钨试样组织、显微硬度及热稳定性的变化。结果表明,多向压缩后纯钨烧结体位错密度显著增大,压下量50%纯钨试样的位错密度由初始烧结钨的3.08×10^(14)增大至8.08×10^(14) m^(-2),平均晶粒尺寸由83.8μm细化至14.7μm,而显微硬度则由HV0.2 417增大至HV0.2 521。多向压缩后纯钨试样的再结晶温度约为1600 K,近似为常数。纯钨烧结体经多向压缩后由于晶粒尺寸减小以及均匀分布的形核点增多,组织热稳定性得到提高。

粉末冶金法制备Cu/Ag(Invar)复合材料的显微组织与性能（英文）

采用球磨制得的Ag(Invar)复合粉体制备Cu/Ag(Invar)复合材料。研究烧结及形变热处理后复合材料的显微组织结构与性能。结果表明,在球磨过程中,微锻造焊合与加工硬化断裂共同作用导致Ag(Invar)粉体的平均颗粒尺寸先急剧增大,再快速降低,最后趋于稳定。相对于Cu/Invar复合材料,Cu/Ag(Invar)复合材料的烧结性能大大提高,其中的气孔小而少。形变热处理后,该复合材料近乎完全致密,具有最佳的相成分与元素分布,更重要的是,该复合材料中的Cu及Invar合金均呈三维网络状连续分布。Cu/Invar界面扩散被Ag阻挡层有效抑制,使Cu/Ag(Invar)复合材料的力学及热学性能均有明显提高。

Cryoballoon pulmonary vein isolation and left atrial appendage occlusion prior to atrial septal defect closure: A case report

BACKGROUND In patients who suffer from both atrial fibrillation(AF)and atrial septal defect(ASD),cryoballoon pulmonary vein isolation(PVI),sequential left atrial appendage(LAA)occlusion and ASD closure could be a strategy for effective prevention of stroke and right heart failure.CASE SUMMARY A 65-year-old man was admitted to our institution due to recurrent episodes of palpitations and shortness of breath for 2 years,which had been worsening over the last 48 h.He had a history of AF,ASD,coronary heart disease with stent implantation and diabetes.Physical and laboratory examinations showed no abnormalities.The score of CHA2DS2VASc was 3,and HAS-BLED was 1.Echocardiography revealed a 25-mm secundum ASD.Pulmonary vein(PV)and LAA anatomy were assessed by cardiac computed tomography.PV mapping with 10-pole Lasso catheter was performed following ablation of all four PVs with complete PVI.Following the cryoballoon PVI,the patient underwent LAA occlusion under transesophageal echocardiographic monitoring.Lastly,a 34-mm JIYI ASD occlude device was implanted.A follow-up transesophageal echocardiography at 3 mo showed proper position of both devices and neither thrombi nor leakage was found.CONCLUSION Sequential cryoballoon PVI and LAA occlusion prior to ASD closure can be performed safely in AF patients with ASD.

Train probe for beam diagnostics of the SC200 superconducting cyclotron

The SC200 proton therapy system commissioned by the Hefei CAS Ion Medical and Technical Devices Co.,Ltd.(HFCIM;Hefei,China)and the Joint Institute for Nuclear Research(JINR;Dubna,Russia)has made significant progress.A main radial beam diagnostic system(MRBDS)equipped with a new type of train probe was developed to satisfy the requirements of beam diagnosis.In this paper,the detailed design of the mechanical structure and electronics system of the MRBDS is presented.The electronics system,which includes hardware and software components,was tested and calibrated.The results show that measurement errors can be significantly reduced by the designed calibration procedures.The repeatability of the mechanical structure was also verified,and the experimental results indicate that the unidirectional repeatability of the positioning is better than 0.3 mm.Finally,the MRBDS was used to measure the phase lag of the particles in the beam,and the results showed a high degree of agreement with theoretical calculations,which proved the applicability and high efficiency of the MRBDS.

Chloride Assisted Growth of Aluminum Nitride Nanobelts and Their Enhanced Dielectric Responses

铝氮化物(AlN ) nanobelts 成功地通过氯化物在高产量被综合帮助蒸汽固体过程。X 光检查衍射，传播电子显微镜学，和选择区域电子衍射证明同样准备的 nanobelts 是纯的，在结构上制服和单身者水晶，并且能被索引到六角形的 wurtzite 结构。微观察在那里显示出那存在在获得的 nanobelts 的没有缺点。nanobelts 的生长方向沿着[0001 ] 。相对绝缘的常数并且绝缘的损失的频率系列在 50 Hz 的频率范围被测量到 5 MHz。这些系列的分析显示在样品的接口在样品的绝缘的行为上有大影响。作为与 AlN 微粉末相比， AlN nanobelts 有高得多的相对绝缘的常数，特别在在房间温度的低频率。

Integration of urchin-like MnCo_(2)O_(4)@C core–shell nanowire arrays within porous copper current collector for superior performance Li-ion battery anodes

Spinel MnCo_(2)O_(4) is a promising energy storage candidate as anode materials in lithium-ion batteries owing to synergistic effects of two intrinsic solid-state redox couples.However,low conductivity,poor rate capacity and rapid capacity fading have seriously impaired its practical applications.To overcome the inferiorities,urchin-like MnCo_(2)O_(4)@C core–shell nanowire arrays have been fabricated directly within a porous copper current collector via a facile hydrothermal method followed by a chemical vapor deposition carbonization process.In a typical nanowire,the core is composed of interconnected MnCo_(2)O_(4)nanoparticles and the shell shows as a thin amorphous carbon layer.The integrated MnCo_(2)O_(4)@C/Cu structure could act as working anodes without using additives or polymer binders.While MnCo_(2)O_(4)@C/Cu possesses slightly longer Li-ion insertion/desertion pathway than that of MnCo_(2)O_(4)/Cu,the carbon shell could effectively prevent the pulverization of MnCo_(2)O_(4) and lower down charge transfer resistance and actively participate in Li-ion cycles.The rearrangement of carbon atoms during lithiation/delithiation cycling could inhibit the formation of passive solid electrolyte interphase films.As a result,the MnCo_(2)O_(4)@C/Cu electrode presents superior rate capacity(600 mAh·g^(−1) at 1 A·g^(−1)) and better stability(797 mAh·g^(−1) after 200 cycles at 100 mA·g^(−1)).The excellent reversible Li ion storage capacity,cycling stability and rate capacity endow MnCo_(2)O_(4)@C/Cu great potential as stable and high output integrated anode materials in Li-ion batteries.

Tailoring strength and ductility of high-entropy CrMnFeCoNi alloy by adding Al

High-entropy alloys with high strength and acceptable ductility at both room and elevated temperatures for high-temperature structural applications are desired. In this paper, CrMnFeCoNi alloy with outstanding ductility but low strength was selected as baseline alloy to study the formation of hard phase to strengthen this ductile alloy by adding Al into it. The results indicate that there is a phase structure transition from fcc to bcc when adding enough Al into CrMnFeCoNi. The yield strength and hardness increase with the content of Al increasing, due to the formation of hard bcc phase in the ductile CrMnFeCoNi alloy.The CrMnFeCoNiAl alloy with a bcc structure shows a high yield strength and adequate ductility at elevated temperatures. At 400 and 500℃, the yield strength and ductility of CrMnFeCoNiAl alloy are 975.59 MPa and6.39%and 989.48 MPa and 9.15%, respectively. An example of tailoring the strength and ductility of high-entropy alloy is demonstrated in this paper.

One-pot synthesis of nickel-cobalt hydroxyfluorides nanowires with ultrahigh energy density for an asymmetric supercapacitor

A novel and unique nickel-cobalt hydroxyfluorides(NiCo-HF)nanowires material is fabricated by one-pot solvothermal synthesis method for asymmetric supercapacitor.The synthesis mechanism and factors that influence the formation of the Ni Co-HF nanowires have been further discussed.The as-prepared NiCo-HF electrode exhibits a high specific capacitance of 3,372.6 F g^(à1),and the capacitance retention of 94.3%can be achieved at a high current density of 20 A g^(à1)after 10,000 cycles.The outstanding electrochemical performance of the electrode can be attributed to the synergistic effect of the nanowires morphology and complicated redox process of active material.Furthermore,an asymmetric supercapacitor assembled with Ni Co-HF nanowires as positive electrode and activated carbon as the negative electrode shows an ultrahigh energy density of 83.6 Wh kg^(à1)at a power density of 379.4 W kg^(à1)and an excellent cycling stability with 86.3%capacitance retention after 10,000 cycles,indicating that this novel material has great promise for potential application in energy storage device.

Entropy versus enthalpy in hexagonal-close-packed highentropy alloys

The addition of hexagonal-close-packed(hcp)non-rare-earth elements Zr,Ti and Co,to the 10-component hep rare-earth-based high-entropy alloys(HEAs)with a composition of ScYLaNdGdTbDyHoErLuX(X=Zr,Co and Ti)was investigated.The enthalpy of mixing between elements was found to have a significant effect on the formation of phases.The addition of Co combines with elements that had a strong chemical affinity to form intermetallic compounds by the effect of enthalpy.Ti was added with all elements with poor chemical affinity and exhibited rejection to form a phase alone.These were the two terminal manifestations of the role of enthalpy over entropy.Part of Zr was soluble in the matrix under the action of entropy,while the other part had a greater affinity for Sc than the other elements to form a precipitate under the action of enthalpy.This was the result of the local balance between the effect of enthalpy and entropy.The solid solution of the elements had different degrees of strengthening effect,among which Zr had the most excellent strengthening effect from 185 to 355 MPa,so the solid solution strengthening model and precipitation strengthening model were proposed to predict the strength of the alloy with the addition of Zr effectively.

Effects of different alloying elements M(M=Fe,Ni,Mn,Si,Mo,Cu,Y)on Cr_(2)0_(3)with Cl:a first-principles study

Using the first-principles methods,the effects of different alloying elements M(M=Fe,Ni,Mn,Si,Mo,Cu,Y)on Cr_(2)0_(3)with Cl adsorption are studied.The results show that the layer distance of all doped models has been widened to different degrees with Cl adsorption.When Mo or Y is doped into the passive film,the difference of layer distance is reduced to a certain extent.The interaction between alloying elements and Cl is studied by calculating the adsorption height,bond population and electron density difference.The results show that Mo and Y can inhibit Cl erosion and improve the corrosion resistance of passive film.Furthermore,we investigate the CrMoFe and CrMoY co-doped system with Cl adsorption.The calculations point out that when Mo and Y are doped together in the passive film,the corrosion resistance of the system is more prominent than that of CrMo,CrY and CrMoFe co-doping systems.

Direct chemical vapor deposition growth of graphene on Ni particles using solid carbon sources

Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel(Ni)matrix composites in recent years.However,its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni matrix.To overcome these two problems,one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder metallurgy.This work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate(PMMA)as the solid sources for chemical vapor deposition(CVD)process.The results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature,respectively.The optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml^(-1) PMMA and 900℃.A competition mechanism rises from the growth kinetic,and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies.

Microstructure evolutions of the W-TiC composite conducted by dual-effects from thermal shock and He-ion irradiation

Considering that tungsten(W)materials served as the plasma-facing material in the fusion reactor would be exposed to edge-localized modes(ELMs)-like thermal shock loading accompanied with He-ion irradiation,the W-TiC composite produced with a wet-chemical method was conducted by the dual effects from the laser beam thermal shock first and He-ion irradia-tion later in this work.The microstructure changes of the W-TiC composite before and after two tests were characterized by scanning electron microscopy or transmission electron microscopy.After the laser beam thermal shock test,there was an obvious interface on the exposed surface of the W-TiC composite.Several main cracks and melting areas could be found nearby the interface and center,respectively.Furthermore,a mixture of tungsten oxide and TiC was easy to aggregate and form into circle areas surrounding the melting area.The thermal shock tested that W-TiC composite was then subjected to the He-ion irradiation.The typical features of fuzz structures could be detected on the surface of the W-TiC composite apart from the center of the melting area.Notably,several nano-sized He bubbles deeply distributed at grain boundaries in the melting area,owing to the grain boundary functioning as the free path for He diffusion.

Preface to the special issue:applications of tungsten materials

Tungsten(W)and its alloys/compounds possesses several proprietary features,which are applied widely in the fields of defense and military,aerospace,electronic industry,radiation shield,machining,photoelectricity,catalytic and energy,etc.Topics in this special issue contain six contributions with two review papers and four research articles,covering plasma facing materials(PFMs)of W materials in fusion engineering,hardmetals of tungsten carbide(WC)-based composites in machining and electrochromic functional materials of tungsten oxide(WO3)in smart materials.