High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys for Advanced Die-Materials Applications

In this study, we report on advanced Ni3Al based high temperature structural alloys with Zr and B addition in order to apply in the fields of die-casting and high temperature press forming as die materials. Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting were investigated in terms of phase analysis by using a scanning electron microscope （SEM） equipped with an X-ray energy dispersive spectrometer （EDS）, an X-ray diffractometer （XRD） and tensile test. The duplex microstructural feature consisting of γ＇ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure. The ultimate tensile strength of the present alloy was superior to commercial iron-based and Ni-based die-materials especially in the high temperature region.

In-situ electrochemical functionalization of carbon materials for high-performance Li–O2 batteries

The development of effective synthetic routes is important to manifest proper nature of specific materials.In-situ electrochemical functionalization possesses great advantages over conventional routes,especially facile way and leading to reaching elaborate sites of functional group.Here,we demonstrate the preparation of functionalized carbons by in-situ electrochemical reduction in an argon atmosphere for application in low-cost,environmentally benign,and high-performance oxygen-electrodes for non-aqueous Li-O2 batteries.A Li-O2 battery with functionalized carbon shows a high discharge capacity(100 times that of pristine carbon),high power and cycling stability.The outstanding performance is attributed to the high O2 affinity of the functionalized carbon surface that facilitates the formation of soluble and diffusible superoxide intermediates by the reduction of the remaining O2 competing with surface growth for Li2O2 formation.

MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

A lightweight flexible thermally stable composite is fabricated by com-bining silica nanofiber membranes(SNM)with MXene@c-MWCNT hybrid film.The flexible SNM with outstanding thermal insulation are prepared from tetraethyl orthosilicate hydrolysis and condensation by electrospinning and high-temperature calcination;the MXene@c-MWCNT_(x:y)films are prepared by vacuum filtration tech-nology.In particular,the SNM and MXene@c-MWCNT_(6:4)as one unit layer(SMC_(1))are bonded together with 5 wt%polyvinyl alcohol(PVA)solution,which exhibits low thermal conductivity(0.066 W m^(-1)K^(-1))and good electromagnetic interference(EMI)shielding performance(average EMI SE_(T),37.8 dB).With the increase in func-tional unit layer,the overall thermal insulation performance of the whole composite film(SMC_(x))remains stable,and EMI shielding performance is greatly improved,especially for SMC_(3)with three unit layers,the average EMI SET is as high as 55.4 dB.In addition,the organic combination of rigid SNM and tough MXene@c-MWCNT_(6:4)makes SMC_(x)exhibit good mechanical tensile strength.Importantly,SMC_(x)exhibit stable EMI shielding and excellent thermal insulation even in extreme heat and cold environment.Therefore,this work provides a novel design idea and important reference value for EMI shielding and thermal insulation components used in extreme environmental protection equipment in the future.

Incorporation of Ionic Conductive Polymers into Sulfide Electrolyte-Based Solid-State Batteries to Enhance Electrochemical Stability and Cycle Life

Sulfide-based inorganic solid electrolytes are promising materials for high-performance safe solid-state batteries.The high ion conductivity,mechanical characteristics,and good processability of sulfide-based inorganic solid electrolytes are desirable properties for realizing high-performance safe solid-state batteries by replacing conventional liquid electrolytes.However,the low chemical and electrochemical stability of sulfide-based inorganic solid electrolytes hinder the commercialization of sulfide-based safe solid-state batteries.Particularly,the instability of sulfide-based inorganic solid electrolytes is intensified in the cathode,comprising various materials.In this study,carbonate-based ionic conductive polymers are introduced to the cathode to protect cathode materials and suppress the reactivity of sulfide electrolytes.Several instruments,including electrochemical spectroscopy,X-ray photoelectron spectroscopy,and scanning electron microscopy,confirm the chemical and electrochemical stability of the polymer electrolytes in contact with sulfide-based inorganic solid electrolytes.Sulfide-based solid-state cells show stable electrochemical performance over 100 cycles when the ionic conductive polymers were applied to the cathode.

Superplasticized vs. Conventional Concrete: A Comparative Review

The global awareness and utilization of superplasticizers (SPs) in concrete have significantly contributed to developing resilient and sustainable infrastructure. Despite this, many developing nations face limited adoption of SPs in construction practices due to a lack of knowledge. This study provides a concise overview of concrete’s mechanical and durability properties, comparing formulations with and without superplasticizers. The focus is on compressive and flexural strengths, modulus of elasticity, water sorptivity, and chloride penetration. The results underscore the considerable improvement in both mechanical and durability properties when SPs are incorporated. The study recommends the widespread use of SPs, particularly in developing countries, to enhance the longevity of concrete structures.

A356/SiC_P与列车实用中的有机闸片的滑动摩擦磨损特性

以铝基复合材料作为列车制动盘材料的实用化为目的，选用A356／SIC 20％（体积分数，下同）复合材料和AISI D2工具钢为摩擦材料，以中速列车实用中的有机闸片为对偶材料，进行对比干摩擦磨损试验，并分析比较了磨损特性。结果表明：铝基复合材料在小于200Y（3．98MPa）的低载荷下，只存在轻微的氧化磨损，耐磨性比实用中的铁合金材料更好；而超过该载荷时。开始发生磨削磨损，磨损量逐步超过铁合金材料，当载荷达到400N（7．96MPa）时，由于严重的磨削磨损，磨损量剧增。而铁合金材料则随载荷和滑动速度增加，磨损率缓慢增加；磨损过程中的复合材料的摩擦系数平均值与载荷、滑动速度无关，始终保持0．3～0．4，同时随磨损距离的波动也非常小，而工具钢的摩擦系数平均值则对试验参数的敏感度相对大些，且摩擦系数平均值也比复合材料略小，即摩擦系数方面复合材料具有更好的特性。

热处理工艺对A356/SiCp性能及干滑动摩擦磨损特性的影响

研究分析热处理工艺对A356/SiCp复合材料的硬度、导电率及微观组织的影响,在此基础上研究复合材料的干滑动摩擦磨损特性。结果表明:固溶和T6热处理可显著提高复合材料的硬度,但降低导电率,而低温退火却比较显著地提高导电率;导电率高的低温退火态磨损特性基本与铸态一致,固溶处理及时效处理虽可有效提高硬度,但不提高耐磨性能,这表明T6热处理是否作为制动盘材料时的最佳热处理工艺,有待进一步研究;复合材料的磨损率随载荷的增加而增加,但低载荷时增加缓慢,高载荷时增加迅速;摩擦因数随着热处理工艺而变化,但对载荷变化不敏感,都在较小的范围内波动,基本是稳定的。

铸态铝基复合材料与半金属衬片摩擦副的干滑动摩擦磨损特性研究

采用铸态A356/SiC复合材料与高速列车制动盘偶件半金属衬片材料摩擦副进行干摩擦磨损试验,并用扫描电子显微镜、X射线衍射仪和能谱仪等手段分析了复合材料的磨损机制.结果表明:复合材料表现出良好的磨损特性,在滑动速度3.0m/s以下,载荷达到600N(12MPa)时的磨损量仍很小;复合材料的磨损率随pv(压力与速度的积)值的增加而增大,摩擦系数则随pv值增加而小幅度减少;磨损过程中磨损表面很快形成以氧化物和以石墨为主的润滑膜,起到了减摩和耐磨作用.在pv值较低时复合材料的磨损机制为轻微的氧化磨损机制,随着pv值增加出现剥层磨损,在复合材料与半金属衬片间的接触表面,由于塑性流动挤出片状磨屑而使磨损量降低.

Behavior of CaO and Calcium in pure Magnesium

Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity. The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis. With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined. As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg. Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.

2,5-Furandicarboxylic acid production via catalytic oxidation of 5-hydroxymethylfurfural:Catalysts,processes and reaction mechanism

Biomass conversion to value-added chemicals has received tremendous attention for solving global warming issues and fossil fuel depletion.5-Hydroxymethylfurfural(HMF)is a key bio-based platform molecule to produce many useful organic chemicals by oxidation,hydrogenation,polymerization,and ring-opening reactions.Among all derivatives,the oxidation product 2,5-furandicarboxylic acid(FDCA)is a promising alternative to petroleum-based terephthalic acid for the synthesis of biodegradable plastics.This review analytically discusses the recent progress in the thermocatalytic,electrocatalytic,and photocatalytic oxidation of HMF into FDCA,including catalyst screening,synthesis processes,and reaction mechanism.Rapid fundamental advances may be possible in non-precious metal and metal-free catalysts that are highly efficient under the base-free conditions,and external field-assisted processes like electrochemical or photoelectrochemical cells.

Effects of Mo and Zr on Microstructure,Mechanical Properties and Wear Resistance of Fe-Al Based Alloys

In this work the microstructure, mechanical properties and wear resistance of Fe-Al based alloys with various alloying elements were studied. The microstructures were examined by optical and scanning electron microscopy （SEM） equipped with an energy dispersive X-ray spectroscope （EDS）. Two types of alloys were prepared by vacuum arc melting. One is Fe-28Al based alloys （D03 structured） with and without alloying elements such as Mo and Zr. The other one is Fe-35Al based alloys （B2 structured） produced with the same manner. For both types of alloys, Mo addition had found to exhibit an equiaxed microstructure, while dendritic structure was observed to show the effect of Zr addition. These microstructural features were more evinced with increasing content of alloying element. Concerning the mechanical properties and wear resistance, Fe-35Al based alloys were superior to Fe-28Al based alloys over the whole temperature range investigated.

Vertically Aligned Silicon Carbide Nanowires/Boron Nitride Cellulose Aerogel Networks Enhanced Thermal Conductivity and Electromagnetic Absorbing of Epoxy Composites

With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel(CA) with highly enhanced thermal conductivity(TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires(SiC NWs)/boron nitride(BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m^(-1) K^(-1) at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy(EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 10^(11) Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of-21.5 dB and a wide effective absorption bandwidth(<-10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications.

Microstructure and texture evolution of Ti-Nb-Si based alloys for biomedical applications

Microstructure and texture of Ti-Nb-Si based alloys, prepared by water quenching from β-phase field, cold rolling and recrystallization heat treatment followed by water quenching, were investigated in terms of optical microstructure and analysis of X-ray pole figure result. In as-quenched sample, relatively random distribution of pole figure was detected without showing a specific texture component. In as-cold rolled sample, however, it is found well-developed several texture components consisting of rotated cube, α-fiber and γ-fiber texture components which are frequently observed in bcc-structured metals and alloys were found. Therefore, texture components developed in the present alloys are closely related to the deformation of β-phase even though small amount of α″ phase co-exist in the microstructure. In recrystallized sample, α-fiber texture component is weakly detected while the other texture components, rotated cube and γ-fiber components, appears to be relatively unchanged. No additional texture components were detected besides those texture components observed in the cold rolled samples.

One-step wet-spinning assembly of twisting-structured graphene/carbon nanotube fiber supercapacitor

Graphene fiber-based supercapacitors hold great promise as flexible energy-storage devices. However, simultaneously achieving high ion-transport ability in electrode and electrolyte layer, which is crucial for realizing the high electrochemical performance, still remains challenging. Here, a facile and effective strategy to solve the problem was proposed by developing a twisting-structured graphene/carbon nanotube(CNT) fiber supercapacitor via one-step wet-spinning process with customized multi-channel spinneret.The remarkable structure features of the resulting fiber supercapacitor with wrinkled and thin electrolyte layer, and well-developed porosity of fiber electrode favored the rapid infiltration and transport of electrolyte ions inside the electrode, as well as between electrode and electrolyte, thus boosting high specific capacitance of 187.6 mF cm^(-2) and energy density of 30.2 μWh cm^(-2), and featuring long cycling life(93%capacitance retention after 10,000 cycles) and excellent flexibility. Moreover, the specific capacitance and energy density could be further improved to 267.2 m F cm^(-2) and 66.8 μWh cm^(-2), respectively, when Mn O2 was incorporated into the fiber.

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.

Interface Engineered Microcellular Magnetic Conductive Polyurethane Nanocomposite Foams for Electromagnetic Interference Shielding

Lightweight microcellular polyurethane(TPU)/carbon nanotubes(CNTs)/nickel-coated CNTs(Ni@CNTs)/polymerizable ionic liquid copolymer(PIL)composite foams are prepared by non-solvent induced phase separation(NIPS).CNTs and Ni@CNTs modified by PIL provide more heterogeneous nucleation sites and inhibit the aggregation and combination of microcellular structure.Compared with TPU/CNTs,the TPU/CNTs/PIL and TPU/CNTs/Ni@CNTs/PIL composite foams with smaller microcellular structures have a high electromagnetic interference shielding effectiveness(EMI SE).The evaporate time regulates the microcellular structure,improves the conductive network of composite foams and reduces the microcellular size,which strengthens the multiple reflections of electromagnetic wave.The TPU/10CNTs/10Ni@CNTs/PIL foam exhibits slightly higher SE values(69.9 dB)compared with TPU/20CNTs/PIL foam(53.3 dB).The highest specific EMI SE of TPU/20CNTs/PIL and TPU/10CNTs/10Ni@CNTs/PIL reaches up to 187.2 and 211.5 dB/(g cm^(−3)),respectively.The polarization losses caused by interfacial polarization between TPU substrates and conductive fillers,conduction loss caused by conductive network of fillers and magnetic loss caused by Ni@CNT synergistically attenuate the microwave energy.

High-loading Co-doped NiO nanosheets on carbon-welded carbon nanotube framework enabling rapid charge kinetic for enhanced supercapacitor performance

Developing high power and energy supercapacitors(SCs)is a long-pursued goal for the application in transportation and energy storage station.Herein,a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded carbon nanotube foam(Co-doped NiO@WCNTF)as freestanding electrode is successfully prepared for high power and energy SCs.The WCNTF framework with high specific surface area provides three dimensional highly conductive network for fast charge transport and ensures high loading of active materials(9.2 mg/cm2).Moreover,porous Co-doped NiO nanosheets uniformly anchored on the WCNTF framework enable rapid charge kinetics due to the high intrinsic conductivity of Co-doped Ni O nanosheets and their good contact with conductive WCNTF substrate.As a result,the unique integrated electrode with 3D architecture exhibits an ultrahigh specific capacitance of 11.45 F/cm2 at 5 mA/cm2,outstanding rate capability(11.45 F/cm2 at 5 mA/cm2 and a capacitance retention of 86.2%at 30 mA/cm2)and good cycling stability,suggesting great potential for high performance supercapacitor.

Effects of Precipitation Temperature on Nanoparticle Surface Area and Antibacterial Behaviour of Mg(OH)₂and MgO Nanoparticles

A series of MgO nanoparticles were prepared by first precipitating and isolating Mg(OH)2 nanoparticles from Mg(NO3)2 at three different temperatures using NaOH followed by their thermal decomposition also at three temperature settings. The effects of temperature at which precipitation and thermal decomposition of the hydroxide occurred were studied to assess their influence on nanoparticle size and surface area. The synthesised nanoparticles were characterized using a suite of techniques including Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscope (SEM) analysis. The average diameter range of MgO nanoparticles ranged between 15 and 35 nm, while for the precursor Mg(OH)2 it varied between 28 and 45 nm. The nanoparticle surface area obtained from BET studies was found in all cases to increase from 77 to 106.4 m2/g with increasing temperature of precipitation. Antibacterial activities of the prepared Mg(OH)2 and MgO nanoparticles were evaluated against the Gram-negative bacteria, Escherichia coli, and the Gram-positive bacteria, Staphylococcus aureus, using agar diffusion method. A correlation between surface area and antibacterial activity supported the mechanism of bacterial inactivation as the generation of reactive species. The Mg(OH)2 and MgO nanoparticles both exhibited pronounced bactericidal activity towards the Gram positive bacteria than Gram negative bacteria as indicated by the extend of the zone of inhibition around the nanoparticle.

Hollow Gradient-Structured Iron-Anchored Carbon Nanospheres for Enhanced Electromagnetic Wave Absorption

In the present paper,a microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance.The inorganic-organic competitive coating strategy was employed,which can effectively adjust the thermodynamic and kinetic reactions of iron ions during the solvothermal process.As a result,Fe nanoparticles can be gradually decreased from the inner side to the surface across the hollow carbon shell.The results reveal that it offers an outstanding reflection loss value in combination with broadband wave absorption and flexible adjustment ability,which is superior to other relative graded distribution structures and satisfied with the requirements of lightweight equipment.In addition,this work elucidates the intrinsic microwave regulation mechanism of the multiscale hybrid electromagnetic wave absorber.The excellent impedance matching and moderate dielectric parameters are exhibited to be the dominative factors for the promotion of microwave absorption performance of the optimized materials.This strategy to prepare gradient-distributed microwave absorbing materials initiates a new way for designing and fabricating wave absorber with excellent impedance matching property in practical applications.

Novel hole transport layer of nickel oxide composite with carbon for high-performance perovskite solar cells

A depth behavioral understanding for each layer in perovskite solar cells （PSCs） and their inter[acial interactions as a whole has been emerged for further enhancement in power conversion efficiency （PCE）. Herein, NiO@Carbon was not only simulated as a hole transport layer but also as a counter electrode at the same time in the planar heterojunction based PSCs with the program wxAMPS （analysis of microelectronic and photonic structures）-lD. Simulation results revealed a high dependence of PCE on the effect of band offset between hole transport material （HTM） and perovskite layers. Meanwhile, the valence band offset （AEv） of NiO-HTM was optimized to be -0.1 to -0.3 eV lower than that of the perovskite layer. Additionally, a barrier cliff was identified to significantly influence the hole extraction at the HTM/absorber interface. Conversely, the AEv between the active material and NiO@Carbon-HTM was derived to be -0.15 to 0.15 eV with an enhanced efficiency from 15% to 16%.