An ionic liquid-assisted strategy for enhanced anticorrosion of low-energy PEO coatings on magnesium–lithium alloy

A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid(ILs)during the LePEO process for LA91 magnesium-lithium(Mg-Li)alloy.Results show that the ionic liquid BmimBF_(4)participates in the LePEO coating formation process,causing an increment in coating thickness and surface roughness.The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process(LePEO-IL).After adding BmimBF_(4),corrosion current density decreases from 1.159×10^(−4)A·cm^(−2)to 8.143×10^(−6)A·cm^(−2).The impedance modulus increases to 1.048×10^(4)·cm^(−2)and neutral salt spray remains intact for 24 h.The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid.The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.

Cation-doped LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode with high rate performance

The nickel-rich layered cathode material LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)has high energy density,lower cost and is a promising cathode material currently under development.However,its electrochemical and structural stability is poor during cycling.Among the many modification methods,cation doping has been consistently proven to be an effective strategy for enhancing electrochemical performance.Herein,the NCM811 cathode material was modified by solid-phase reactions with Mg and Al doped.In addition,the corresponding mechanism of NCM811 cathode material-doped modification is explored by density functional theory(DFT)calculations,and we have extended this approach to other ternary cathode materials with different ratios and obtained universal laws.Combined with DFT calculations,the results show that Mg2+occupies the Li+site and reduces the degree of Li^(+)/Ni^(2+) mixture;Al^(3+) acts as a structural support during charging and discharging to prevent structural collapse.The electrochemical properties were tested by an electrochemical workstation and the LAND system,and the results showed that the capacity retention rate increased to varying degrees from 63.66%to 69.87%and 89.05%for NCM811-Mg and NCM811-Al at room temperature after 300 cycles,respectively.This study provides a theoretical basis and design strategy for commercializing cationic-doped modification of nickel-rich cathode materials.

Study on metal recovery process and kinetics of oxidative leaching from spent LiFePO_(4)Li-batteries

A green environmental protection and enhanced leaching process was proposed to recover all elements from spent lithium iron phosphate(LiFePO_(4)) lithium batteries.In order to reduce the influence of Al impurity in the recovery process,NaOH was used to remove impurity.After impurity removal,the spent LiFePO_(4) cathode material was used as raw material under the H_(2)SO_(4) system,and the pressure oxidation leaching process was adopted to achieve the preferential leaching of lithium.The E-pH diagram of the Fe-P-Al-H_(2)O system can determine the stable region of each element in the recovery process of spent LiFePO_(4)Li-batteries.Under the optimal conditions(500 r·min^(-1),15 h,363.15 K,0.4 MPa,the liquid-solid ratio was 4:1 ml·g^(-1)and the acid-material ratio was 0.29),the leaching rate of Li was 99.24%,Fe,Al,and Ti were 0.10%,2.07%,and 0.03%,respectively.The Fe and P were precipitated and recovered as FePO_(4)·2H_(2)O.The kinetic analysis shows that the process of high-pressure acid leaching of spent LiFePO_(4) materials depends on the surface chemical reaction.Through the life cycle assessment(LCA)of the spent LiFePO_(4) whole recovery process,eight midpoint impact categories were selected to assess the impact of recovery process.The results can provide basic environmental information on production process for recycling industry.

Highly Thermally Conductive and Structurally Ultra‑Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management

Highly thermally conductive graphitic film(GF)materials have become a competitive solution for the thermal management of high-power electronic devices.However,their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety.Here,we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks(LNS),which reveals a bubbling process characterized by“permeation-diffusion-deformation”phenomenon.To overcome this long-standing structural weakness,a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film(GF@Cu)with seamless heterointerface.This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K.Moreover,GF@Cu maintains high thermal conductivity up to 1088 W m^(−1)K^(−1)with degradation of less than 5%even after 150 LNS cycles,superior to that of pure GF(50%degradation).Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

A novel approach of jet polishing for interior surface of small-grooved components using three developed setups

It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.

Optimization on microstructure,mechanical properties and damping capacities of duplex structured Mg–8Li–4Zn–1Mn alloys

Optimizing the mechanical properties and damping capacity of the duplex-structured Mg–Li–Zn–Mn alloy by tailoring the microstructure via hot extrusion was investigated.The results show that the Mg–8Li–4Zn–1Mn alloy is mainly composed ofα-Mg,β-Li,Mg–Li–Zn and Mn phases.The microstructure of the test alloy is refined owing to dynamic recrystallization(DRX)during hot extrusion.After hot extrusion,the crushed precipitates are uniformly distributed in the test alloy.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of as-extruded alloy reach 156 MPa,208 MPa,and 32.3%,respectively,which are much better than that of as-cast alloy.Furthermore,the as-extruded and as-cast alloys both exhibit superior damping capacities,with the damping capacity(Q^(-1))of 0.030 and 0.033 at the strain amplitude of 2×10^(-3),respectively.The mechanical properties of the test alloy can be significantly improved by hot extrusion,whereas the damping capacities have no noticeable change,which indicates that the duplex-structured Mg–Li alloys with appropriate mechanical properties and damping properties can be obtained by alloying and hot extrusion.

Microstructure characteristics and mechanical properties of Al/Mg joints manufactured by magnetic pulse welding

The effective connection of 1050 Al and AZ31 Mg was realized by magnetic pulse welding.The maximum tensile-shear force of the dissimilar Al/Mg metal lap joint reached 97%of that of the 1050 Al alloy base material by optimizing the process parameters.The microstructure of dissimilar Al/Mg welded joints was analysed by Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS)and Electron Backscattered Diffraction(EBSD).The results show that the key to obtaining high shear strength of Al/Mg dissimilar metal joints is mainly due to the following two reasons.On the one hand,grain refinement and element interdiffusion occur at the interface.On the other hand,no intermetallic compounds are formed at the interface.

Preparation of highly efficient antibacterial non-woven by facile plasma-induced graft polymerizing of DADMAC

The development of surface modification technology for temperature sensitive fibers has been a huge challenge.In this work,a novel technique based on cold plasma treatment was developed for the preparation of anti-bacterial polypropylene(PP)fibers.The results showed that plasma treatment introduced a rough surface and polar groups,which acted as the anchor point and initiators for diallyldimethyl ammonium chloride(DADMAC)graft-polymerization.The fabricated PP membranes presented a high bacterial sterilization rate,as well as excellent adhesion force and washing durability.After ultrasonic treatment for 30 min,the physical coating sample had lost anti-bacterial effect,while the plasma grafted sample still showed a sterilization rate of 91.67%.This work provided a clean and novel DADMAC grafting method and it is also applicable for anti-bacterial material fabrication.

Oxidation mechanism of high-volume fraction SiCp/Al composite under laser irradiation and subsequent machining

Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles(hereinafter referred to as an SiCp/Al composite)faces problems such as rapid tool wear,high specific cutting force,and poor surface integrity.Instead,a promising method for solving these problems is laser-induced oxidation-assisted milling(LOAM):under laser irradiation,the local workpiece material reacts with oxygen,thus forming loose and porous oxides that are easily removed.In the present work,the oxidation mechanism of SiCp/Al irradiated by a nanosecond pulsed laser is studied to better understand the laser-induced oxidation behavior and control the characteristics of the oxides,with laser irradiation experiments performed on a 65%SiCp/Al composite with various laser parameters and auxiliary gases(oxygen,nitrogen,and argon).With increasing laser pulse energy density,both the ablated groove depth and the width of the heat-affected zone increase.When oxygen is used as the auxiliary gas,an oxide layer composed of SiO_(2)and Al2O3 forms,and CO_(2)is produced and escapes from the material,thereby forming pores in the oxides.However,when nitrogen or argon is used as the auxiliary gas,a recast layer is produced that is relatively difficult to remove.Under laser irradiation,the sputtered material reacts with oxygen to form oxides on both sides of the ablated groove,and as the laser scanning path advances,the produced oxides accumulate to form an oxide layer.LOAM and conventional milling are compared using the same milling parameters,and LOAM is found to be better for reduced milling force and tool wear and improved machined surface quality.

Applications of magnesium alloys for aerospace:A review

With the increasingly excellent performance of magnesium alloy materials, magnesium alloys are increasingly widely used under the urgent need for weight reduction in aerospace applications. However, due to the severe aviation environment, the strength, corrosion resistance and electrical conductivity of magnesium alloy materials need to be further improved. Many scholars are committed to studying higher comprehensive mechanical properties. Besides, they have studied surface treatment processes with space application characteristics, such as high emissivity oxidation and high anti-corrosion electroplating. To further improve the safety and reliability of magnesium alloys and expand their applications, this paper discusses several kinds of magnesium alloys and summarizes their research progress. The whole manuscript should be revised by an expert who has more experience on English writing. At the same time, the surface treatments of magnesium alloy materials for aerospace are analyzed. Besides, the application of magnesium alloy in aerospace field is summarized. With the in-depth research of many scholars, the improvement of material properties and the development of surface protection and functional technology, it is believed that magnesium alloys will be used in more and more aerospace applications and make more contributions to the aerospace field.

Evolution and Development Trend Prospect of Metal Milling Equipment

The world is currently undergoing profound changes which have never happened within the past century.Global competition in the technology and industry fields is becoming increasingly fierce.The strategic competition of the major powers further focuses on the manufacturing industry.Developed countries such as the United States,Germany,and Japan have successively put forward strategic plans such as“re-industrialization”and“return of manufacturing industry”,aiming to seize the commanding heights of a new round of global high-end technology competition and expand international market share.Standing at the historic intersection of a new round of scientific and technological revolution and China's accelerated high-quality development,the“14th Five-Year Plan”clearly pointed out that intelligent manufacturing is the main development trend to promote China's manufacturing to the medium-high end of the global value chain.This reflects the importance of advanced manufacturing for national strategic layout.To better grasp the development direction of advanced manufacturing equipment,the development process and current application status of manufacturing equipment are summarized,and thereafter the characteristics of manufacturing equipment in different development stages of the manufacturing industry are analyzed.Finally,the development trend of advanced milling equipment is prospected.

Research on the microstructure and properties of a multi-pass friction stir processed 6061Al coating for AZ31 Mg alloy

A 6061 Al coating for AZ31 Mg alloy was prepared by multi-pass friction stir welding(FSW)with different travel speeds.The mi-crostructure,mechanical properties of the interfacial region and the corrosion behavior of the coating were investigated systematically.The results indicate that the interfacial intermetallic compounds formed in the stir zone(SZ)consist of mainly Al12Mg17 and Al3Mg2.The inter-metallic compounds in the SZ are significantly increased when the travel speed is increased from 30 mm/min to 60 mm/min.Microhardness measurements and results of shear-tensile tests show that the mechanical properties are influenced by the intermetallic compounds formed in the SZ during FSW.Corrosion tests indicate that the 6061 Al coating can significantly improve the corrosion resistance of AZ31 plate.The 6061 Al coating obtained with a travel speed of 30 mm/min has a maximum corrosion potential E corr of-0.503 V VSE.

Finite Element Analysis and Experiment on Viscous Warm Pressure Bulging of AZ31B Magnesium Alloy

Aiming at overcoming the low plasticity of magnesium alloy at room temperature, we researched viscous warm pressure bulging（VWPB） of AZ31B magnesium alloy based on the excellent thermal stability of viscous medium under the warm forming condition. The potential improvements of plastic deformation ability and forming quality of AZ31B magnesium alloy are expected with the aid of thermal characteristics of viscous medium. During bulging process the velocity field variation and pressure stress field distribution of viscous medium are observed at different temperatures through which the effect of temperature on the mechanical property of viscous medium and AZ31B magnesium alloy are analyzed. The results show that the formability of AZ31B magnesium alloy increases first and then decreases as the temperature increases and it is the best at 200 ℃. On the other hand, the viscous medium which can build non-uniform pressure stress field also exhibits a good flow property at elevated temperature, and it is helpful to improving the formability of AZ31B magnesium alloy.

Belief reliability modeling and analysis for planetary reducer considering multi-source uncertainties and wear

The planetary reducer is a common type of transmission mechanism,which can provide high transmission accuracy and has been widely used,and it is usually required with high reliability of transmission characteristics in practice.During the manufacturing and usage stages of planetary reducers,uncertainties are ubiquitous and wear is inevitable,which affect the transmission characteristics and the reliability of planetary reducers.In this paper,belief reliability modeling and analysis considering multi-uncertainties and wear are proposed for planetary reducers.Firstly,based on the functional principle and the influence of wear,the performance margin degradation model is established using the hysteresis error as the key performance parameter,where the degradation is mainly caused by the accumulated wear.After that,multi-source uncertainties are analyzed and quantified separately,including manufacturing errors,uncertainties in operational and environmental conditions,and uncertainties in performance thresholds.Finally,the belief reliability model is established based on the performance margin degradation model.A case study of a planetary reducer is applied and the reliability sensitivity analysis is implemented to show the practicability of the proposed method.The results show that the proposed method can provide some suggestions to the design and manufacturing phases of the planetary reducer.

Surface Modification with Carbon Fiber for the Metallization of Polyether-ether-ketone

The poly-ether-ether-ketone(PEEK)polymer is a semi-crystalline aromatic thermoplastic with outstanding features,such as superior mechanical properties,thermal stability,radiation resistance and excellent chemical and hydrolysis resistance.However,PEEK exhibits a high volume resistivity(1014Ω·m)and surface resistance(1015Ω).This limits its use in the electronics and electromagnetic field.To decrease the resistivity and reduce the thermal expansion of composite materials,this paper modified the PEEK with carbon fiber(CF)and metalized the composites with the electroless Ni-P alloy plating through self-catalyzed deposition,which brings about high conductivity,thermal conductivity,high-temperature weldability resistance and high-low temperature resistance property.The composites and metal coatings were characterized by metallurgical microscope,SEM,and resistance tester.The metal coatings have a uniform surface and low surface resistance less than 10 mΩ~20 mΩ.The thermal shock test at 250°C and the-70°C^100°C high-low temperature environment test were measured.Compared with the electroless plating on unmodified peek,there is no bump and crack,etc.after testing,which shows a good adhesion between the metal coatings and PEEK-CF,high-low temperature resistance as well as high temperature weldability.The researches on the modification of PEEK by carbon fiber and its surface metallization provide technical support for the application of PEEK Composites in radar antenna and other electronic fields.

Accuracy evaluation for in-situ machining reference points binocular measurement based on credibility probability

Passive binocular measurement systems are being increasingly utilized in the in-situ industries of automobiles,aviation,and aerospace,etc.due to their excellent qualities of accuracy,efficiency,and cost performance.Whereas the barrier of evaluating the accuracy of measured objects resulted from the unequal equivalent focal length and quantization of pixels,has limited their further development and application of high requirements for in-situ machining,e.g.,the measurement of machining reference points for the positioning of robotic drilling in aerospace manufacturing.In this paper,an accuracy evaluation method is proposed to address the problem.Firstly,the unequal equivalent focal length is considered to improve the accuracy of 3D reconstruction.Next,the credibility probability model is developed to calculate the probability of the observed error in the public view of the binocular measurement system and indicates the direction of improvement.Finally,the in-situ experiment is carried out to validate the method within the effective public view range of 300 mm×300 mm.The experiment results show that the RMSs of observed errors are superior to 0.035 mm,and the credibility probabilities are all higher than 0.91;the maximum 3D reconstruction accuracy improvement is 60.3%,with the error reduced from 0.078 mm to 0.031 mm.

Analysis of Chang’e-5 lunar core drilling process

Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface.This study analyzed the lunar core drilling process based on the telemetry data,image information,and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith.In particular,a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before,during,and after sampling.The results revealed that the drilling dip angle of Chang’e-5 was approximately2.3.,and the deviation of the drilling length and depth was less than 2 mm.For continuous drilling,a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil.The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil,thereby lagging the action of the force response.Additionally,a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil.Furthermore,the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm,as the drilling encountered several rocky regions.Moreover,the drilling point exhibited two prominent stratification variations at~28.7 cm and~70 cm below the lunar surface.Ultimately,the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed.The segmented estimation results can support research on subsurface lunar soil.

Influence of lunar regolith compressibility on sampling performance of thick wall spiral drills

A 2 m class robotic drill was sent to the Moon and successfully collected and returned regolith samples in late 2020 by China.It was a typical thick wall spiral drill(TWSD)with a hollow auger containing a complex coring system to retain subsurface regolith samples.Before the robotic drill was launched,a series of laboratory tests were carried out to investigate and predict the possible drilling loads it may encounter in the lunar environment.This work presents how the sampling performance of the TWSD is affected by the regolith compressibility.Experiments and analysis during the drilling and sampling process in a simulated lunar regolith environment were conducted.The compressibility of a typical lunar regolith simulant(LRS)was measured through unidirectional compression tests to study the relationship between its inner regolith stress and bulk density.A theoretical model was established to elucidate the cutting discharge behavior by auger flights based on the aforementioned relationship.Experiments were conducted with the LRS,and the results show that the sampling performance is greatly affected by the flux of the drilled cuttings into the spiral flight channels.This work helped in scheduling reasonable drilling parameters to promote the sampling performance of the robotic drill in the Chinese Chang’E 5 mission.

Illumination and regolith temperature at China's next candidate lunar landing site Shackleton crater

This study focuses on the illumination and temperature at China’s next lunar candidate landing site Shackleton crater.We used the NASA’s SPICE system to evaluate the terrain obscuration effect on real-time illumination;the resulting illumination map resembles previous studies,validating the methodologies used in our study.In addition,we estimated an accumulated illumination map for the period of likely rover movement.The map indicates the illuminated inner wall of the Shackleton crater is close to 27%of the whole,meaning that the rover will likely receive solar radiation during its movement.Using the real-time illumination and the distributed 1-D thermal diffusion model,we continuously evaluated the regolith temperature for more than 20 years to stabilize the temperature,and selected the temperature of the end time as the initial value used in a thermal study set for July 20,2023 and May 8,2027.Our results indicate the temperature in the permanent shadow region remains nearly constant,thus validating the stability of our estimated initial temperature.Our results also indicate that the surface temperature is more sensitive to transient illumination,but the subsurface temperature is more likely to be associated with the accumulated illumination.This difference indirectly implies that the conductivity of the lunar regolith is inefficient.The locations receiving more solar radiation show a temperature larger than the threshold(~112 K)of ice stability.The permanently shadowed regions can be as cold as 25 K,and such extreme coldness is a hazard to the rover.There are suitable temperature locations which have a warm surface but cold subsurface to preserve water ice.To further ensure normal rover movement,we provided a map of suitable temperature sites and found that these locations exist not only in the Shackleton crater’s inner wall,but also outside the crater.We suggested four trade-off sampling sites with suitable temperatures and gradual slopes.

Achieving Excellent Electromagnetic Interference Shielding Effectiveness in High Rare Earth Mg-12Gd-3Y alloy via Nd Addition Combined with Hot Rolling and Aging

Achieving excellent electromagnetic interference(EMI)shielding effectiveness(SE)in high rare earth(RE)-content Mg alloys is currently a significant technical challenge.This work systematically investigated the effects of different Nd elements on the electrical conductivity and EMI SE of Mg-12Gd-3Y-xNd alloy by adding Nd elements to the high RE content Mg-12Gd-3Y alloy,followed by a combined process of hot rolling and aging(R-A).The results indicate that the addition of Nd elements leads to reduced solid solubility of Gd and Y,resulting in a large amount of precipitation.The Mg-12Gd-3Y-2.0Nd alloy has the optimum EMI SE after 63%R-A treatment,reaching 88-118 dB at 30-1500 MHz.The Mg-12Gd-3Y-xNd alloy has acicular and granular forms of the Mg5(Gd,Y,Nd)(abbreviated as Mg5RE)phase after R-A treatment.The granular Mg5RE phase gradually breaks up and refines into more minor scales with increasing rolling reduction and is diffusely distributed in the matrix.The acicular Mg5RE phase is densely arranged,with cross-distribution in some areas.The cross-distributed acicular Mg5RE phase,the delicate granular Mg5RE phase,and the denseβ′phase provide more interfaces for reflecting electromagnetic waves and increase the multiple reflection loss of incident electromagnetic waves.In addition,the Mg-12Gd-3Y-xNd alloy deflects most of the c-axis of the grains parallel to the normal direction(ND)as the rolling reduction increases,making the impedance difference between the plate surface and air larger.The increased impedance makes the material reflect more loss to incident electromagnetic waves.The combined use of these two leads to an excellent EMI SE of Mg-12Gd-3Y-xNd with high RE content after R-A treatment.