Microstructure and mechanical properties of Fe/NbC composite layer prepared by in-situ reaction

NbC ceramic surface-reinforced steel matrix composites were prepared by an in-situ reaction method at different temperatures(1,050℃,1,100℃and 1,150℃)for different times(1 h,2 h and 3 h).The phase constitution,microstructure and fracture morphology of NbC ceramic surface-reinforced steel matrix composites were analyzed by XRD,SEM and EDS,and the effects of the in-situ reaction temperature and time on the mechanical properties were systematically studied.The results indicate that the NbC reinforcement layer is formed through the reaction between Nb atoms and carbon atoms diffused from the steel matrix to the Nb plate.The thickness of this reinforcement layer increases as the reaction time prolongs.Additionally,an increase in reaction temperature results in a thicker reinforcement layer,although the rate of increase gradually decreases.The relationship among the thickness of the Nb C reinforcement layer,the reaction time and temperature was established by data fitting.The optimal tensile performance is achieved at 1,100℃for 1 h,with a tensile strength of 228 MPa.It is also found that the defects between the reinforcement layer and the steel matrix are related to reaction temperature.At 1,100℃,these defects are minimal.Fracture mostly occurs in the NbC reinforced layer of the composites,and the fracture mode is characterized by typical intergranular brittle fracture.

Dense copper azide synthesized by in-situ reaction of assembled nanoporous copper microspheres and its initiation performance

Copper azide with high density was successfully synthesized by in-situ reaction of nanoporous copper(NPC)precursor with HN_(3) gaseous.NPC with pore size of about 529 nm has been prepared by electroless plating using polystyrene(PS)as templates.The copper shells thickness of NPC was controlled by adjusting the PS loading amount.The effects of copper shell on the morphology,structure and density of copper azide were investigated.The conversion increased from 87.12%to 95.31%when copper shell thickness decrease from 100 to 50 nm.Meanwhile,the density of copper azide prepared by 529 nm NPC for 24 h was up to 2.38 g/cm^(3).The hollow structure of this NPC was filled by swelling of copper azide which guaranteed enough filling volume for keeping the same shape as well as improving the charge density.Moreover,HNS-IV explosive was successfully initiated by copper azide with minimum charge thickness of 0.55 mm,showing that copper azide prepared has excellent initiation performance,which has more advantages in the application of miniaturized explosive systems.

Microstructure and Properties of A IN Coating/Graphite Fabricated via In-situ Reaction

A novel method was used to fabricate AlN coating on graphite substrate. This approach included two steps： firstly, the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate; secondly, AlN coating was formed through the in-situ reaction of Al with the sprayed BN. The reaction was investigated by thermogravimetric-differential thermal analysis （TG-DTA）, and the phase composition in the synthetic process was characterized by X-ray diffraction （XRD）. Scanning electronic microscopy （SEM） was used to observe the morphology, and electron probe microanalysis （EPMA） was used to observe the distribution of the elements. The experimental results show that the AlN coating is dense and bonded with graphite tightly.

Microstructure and Mechanical Property of (TiNbTaZrHf)C Synthesized by In-situ Reaction

The(TiNbTaZrHf)C high entropy carbide(HEC)was successfully synthesized by complete commercial transition metal powders,obtained fine sintered bulks without additives by in-situ reaction element synthesis method.(TiNbTaZrHf)C bulk shows a face centered cubic rock salt structure with homogeneous single-phase FCC structure in composition and structure.The optimum sintering temperature is about 1900℃at which the best mechanical properties are obtained.The mechanical properties of(TiNbTaZrHf)C ceramic block are better than those of binary transition metal carbides,and it has obvious high entropy effect.Adding a small amount of Al as sintering additive,the mechanical properties of(TiNbTaZrHf)C ceramics continue to improve,the bending strength of the samples at each temperature is increased by at least 38%,and the highest is 486 MPa.The elastic modulus and hardness of the sample at 1900℃are also slightly increased by 4%and 14%,respectively.The above conclusions illustrate that the properties of high entropy ceramics are greatly improved by in-situ reaction sintering.

PARTICLES ANALYSIS OF Al_2O_3 PARTICLE REINFORCED ZL202 MATRIX COMPOSITES PREPARED BY IN-SITU REACTION

ZL202 matrix composite reinforced by Al2O3 particles was prepared by combining in-situ reaction and casting techniques. Particles' size in the composites was from 1 to 5 microns in diameter. X-ray diffraction analysis verified that the reinforcing particleswere δ-Al2O3 which belong to γ-Al2O3 series. The wetting angle between matrix andreinforcement was less than 90°. Energy spectrum analysis indicated that the reactionin bell cover pressing process took place not so completely as in flouring stir process. When the reaction was finished, the matrix was still ZL202 alloy in both.processes.

Oxidation of Dibenzothiophene in Model Diesel Using Hydroperoxide Generated via In-Situ Reaction of Octane with Oxygen

The potential of carrying out oxidative desulfurization(ODS) using oxygen as an oxidant was explored in this work. n-Octane firstly reacted with oxygen to produce hydroperoxides in-situ, which were then used as oxidants to oxidize the dibenzothiophene(DBT) in the absence of catalysts. The hydroperoxides generated in-situ were effective in oxidizing DBT to its corresponding dibenzothiophene sulfone(DBTO_2) which was characterized by FT-IR and ~1H-NMR. The removal rate of DBT could reached 98.4% under conditions covering a temperaure of 140℃, a rection duration of 4 h, and an oxygen partial pressure of 0.4 MPa. The influences of different hydrocarbon components in diesel on DBT removal were investigated. The results showed that cyclohexane and n-dodecane had no effect on the removal of DBT, but xylene had a slight negative effect on DBT removal. A possible oxidation mechanism was proposed and the concentration of hydroperoxides in both O_2-oxidized octane and model diesel were detected.

Layered structure of Ni-Al multi-layered metal-intermetallic composites fabricated by in-situ reactions

Systematical experiments were done at five temperature levels: （500 ℃,） （630 ℃,） （900 ℃,） （1 000 ℃） and （1 100 ℃） to illuminate the layer structure of the multi-layered metal-intermetallic composites of Ni-Al system that were fabricated by a previously reported simple and cost-effective method. The analysis of back scattering photos and XRD examination of specimens reveal that the look like single compound layer is composed of several different components. The primary phase produced during reaction is Ni2Al3 and there exists a like two-phase field between NiAl3 and Ni2Al3. The high temperature phases like NiAl and Ni3Al are also found at low temperature. The results indicate that the key driving force of in-situ reaction is not temperature, but the atom concentration.

Effects of hot-pressing parameters on microstructure and mechanical properties of composites synthesized by Al-TiO_(2) in-situ reaction

As a classic in-situ reaction, the Al-TiO_(2) reaction is expected to prepare aluminum matrix composites with high thermal stability.In this study, it was found that the preparation method of ensuring sufficient reaction using higher temperatures in previous studies was not conducive to acquiring optimized high-temperature strength. With the increase of hot-pressing temperature and the extension of holding time, the in-situ reaction became more thorough, but the strength of the composites first increased and then decreased. Coarsening of the microstructure at high temperatures would lead to degradation of strength and controlling the in-situ reaction process by the hot-pressing parameters could optimize the mechanical properties of the composites. Strengthening mechanisms at room and high temperatures were studied, and it was found that the load-transfer and Orowan strengthening mechanisms are the main strengthening effects at room temperature, while the pinning effect of fine particles became more crucial at elevated temperatures. As a result, the coarsening of the reinforcing phases was more detrimental to the hightemperature strength. Therefore, an insufficient in-situ reaction led to more excellent mechanical properties, and the composite hot-pressed at 605℃ and held for 2 h exhibited the highest strength, which was 367 MPa at room temperature and 170 MPa at 350℃.

Reaction视频中用户弹幕信息交互行为的情感反应生成机理研究

深入挖掘Reaction视频中弹幕信息交互行为的情感反应机理有助于理解用户弹幕创作背后的情感生成原因及情感变化过程。本文基于情感反应模型,利用定向内容分析法对哔哩哔哩网站中11个热门视频的弹幕信息资源、视频内容以及reactor反应情况展开编码研究,构建了Reaction视频中用户弹幕信息交互行为的情感反应生成机理模型。研究发现,Reaction视频弹幕信息交互行为中的情感反应生成机理总体上遵循“信息刺激-情感反应”的路径,信息刺激有时会独立唤醒情绪或特定情感态度,有时也会通过唤醒特定情感态度进而影响情绪或内化情感态度的生成。该模型有助于提升情感反应理论在计算机协助交流中的情境化探索,也将为社交媒体中用户与信息交互提供优化建议。

Eutectic Solution Enables Powerful Click Reaction for In-Situ Construction of Advanced Gel Electrolytes

Thiol-ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity,atom economy and less side reaction.However,the explosive reaction rate and the use of non-electrolytic amine catalyst hamper its application in in-situ batteries.Herein,a nitrogen-containing eutectic solution is designed as both the catalyst of the thiol-ene reaction and the plasticizer to in-situ synthesize the gel polymer electrolytes,realizing a mild in-situ gelation process and the preparation of high-performance gel electrolytes.The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4×10^(−4)S cm^(−1)and lithium-ion transference number(t_(Li)^(+))of 0.51 at 60°C.The as-assembled Li/LiFePO_(4)(LFP)cell delivers a high initial discharge capacity of 155.9 mAh g^(-1),and a favorable cycling stability with the capacity retention of 82%after 800 cycles at 1 C is also obtained.In addition,this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g^(-1)at 5 C and 10 C,respectively,and the cell can steadily work at various charge–discharge rate for 200 cycles.This powerful and efficient strategy may provide a novel way for in-situ preparing gel polymer electrolytes with desirable comprehensive performances.

Tuning electronic structure of RuO_(2)by single atom Zn and oxygen vacancies to boost oxygen evolution reaction in acidic medium

The poor stability of RuO_(2)electrocatalysts has been the primary obstacles for their practical application in polymer electrolyte membrane electrolyzers.To dramatically enhance the durability of RuO_(2)to construct activity-stability trade-off model is full of significance but challenging.Herein,a single atom Zn stabilized RuO_(2)with enriched oxygen vacancies(SA Zn-RuO_(2))is developed as a promising alternative to iridium oxide for acidic oxygen evolution reaction(OER).Compared with commercial RuO_(2),the enhanced Ru–O bond strength of SA Zn-RuO_(2)by forming Zn-O-Ru local structure motif is favorable to stabilize surface Ru,while the electrons transferred from Zn single atoms to adjacent Ru atoms protects the Ru active sites from overoxidation.Simultaneously,the optimized surrounding electronic structure of Ru sites in SA ZnRuO_(2)decreases the adsorption energies of OER intermediates to reduce the reaction barrier.As a result,the representative SA Zn-RuO_(2)exhibits a low overpotential of 210 mV to achieve 10 mA cm^(-2)and a greatly enhanced durability than commercial RuO_(2).This work provides a promising dual-engineering strategy by coupling single atom doping and vacancy for the tradeoff of high activity and catalytic stability toward acidic OER.

Deformable Catalytic Material Derived from Mechanical Flexibility for Hydrogen Evolution Reaction

Deformable catalytic material with excellent flexible structure is a new type of catalyst that has been applied in various chemical reactions,especially electrocatalytic hydrogen evolution reaction(HER).In recent years,deformable catalysts for HER have made great progress and would become a research hotspot.The catalytic activities of deformable catalysts could be adjustable by the strain engineering and surface reconfiguration.The surface curvature of flexible catalytic materials is closely related to the electrocatalytic HER properties.Here,firstly,we systematically summarized self-adaptive catalytic performance of deformable catalysts and various micro–nanostructures evolution in catalytic HER process.Secondly,a series of strategies to design highly active catalysts based on the mechanical flexibility of lowdimensional nanomaterials were summarized.Last but not least,we presented the challenges and prospects of the study of flexible and deformable micro–nanostructures of electrocatalysts,which would further deepen the understanding of catalytic mechanisms of deformable HER catalyst.

“Buckets effect”in the kinetics of electrocatalytic reactions

In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.

Progress in in-situ electrochemical nuclear magnetic resonance for battery research

A thorough understanding of the fundamental electrochemical and chemical processes in batteries is crucial to advancing energy density and power density.However,the characterizations of such processes are complex.In-situ electrochemical nuclear magnetic resonance(EC-NMR)offers the capability to collect real-time data during battery operation,furnishing insights into the local structures and ionic dynamics of materials by monitoring changes in the chemical environment around the nuclei.EC-NMR also has the advantages of being both quantitative and non-destructive.This paper systematically reviews the design of EC-NMR approach,and delves into the applications and progress of EC-NMR concerning battery reaction mechanisms,failure mechanisms,and overall battery systems.The review culminates in a comprehensive summary of the perspective and challenges associated with EC-NMR.

Assessing the conservation impact of Chinese indigenous chicken populations between ex-situ and in-situ using genome-wide SNPs

Conservation programs require rigorous evaluation to ensure the preservation of genetic diversity and viability of conservation populations. In this study, we conducted a comparative analysis of two indigenous Chinese chicken breeds, Gushi and Xichuan black-bone, using whole-genome SNPs to understand their genetic diversity, track changes over time and population structure. The breeds were divided into five conservation populations(GS1, 2010, ex-situ;GS2, 2019, ex-situ;GS3, 2019, in-situ;XB1, 2010, in-situ;and XB2, 2019, in-situ) based on conservation methods and generations. The genetic diversity indices of three conservation populations of Gushi chicken showed consistent trends, with the GS3 population under in-situ strategy having the highest diversity and GS2 under ex-situ strategy having the lowest. The degree of inbreeding of GS2 was higher than that of GS1 and GS3. Conserved populations of Xichuan black-bone chicken showed no obvious changes in genetic diversity between XB1 and XB2. In terms of population structure, the GS3 population were stratified relative to GS1 and GS2. According to the conservation priority, GS3 had the highest contribution to the total gene and allelic diversity in GS breed, whereas the contribution of XB1 and XB2 were similar. We also observed that the genetic diversity of GS2 was lower than GS3, which were from the same generation but under different conservation programs(in-situ and ex-situ). While XB1 and XB2 had similar levels of genetic diversity. Overall, our findings suggested that the conservation programs performed in ex-situ could slow down the occurrence of inbreeding events, but could not entirely prevent the loss of genetic diversity when the conserved population size was small, while in-situ conservation populations with large population size could maintain a relative high level of genetic diversity.

In-situ AFM and quasi-in-situ studies for localized corrosion in Mg-9Al-1Fe-(Gd) alloys under 3.5 wt.% NaCl environment

Revealing the localized corrosion process of Mg alloy is considered as one of the most significant ways for improving its corrosion resistance.The reliable monitor should be high distinguishability and real-time in liquid environment.Herein,Mg-9Al-1Fe and Mg-9Al-1Fe-1Gd alloys were designed to highlight the impact of intermetallic on the corrosion behaviour.In-situ AFM with a special electrolyte circulation system and quasi-in-situ SEM observation were used to monitor the corrosion process of the designed alloys.SEM-EDS and TEM-SAED were applied to identify the intermetallic in the designed alloys,and their volta potentials were measured by SKPFM.According to the real-time and real-space in-situ AFM monitor,the corrosion process consisted of dissolution of anodicα-Mg phase,accumulation of corrosion products around cathodic phase and shedding of some fine cathodic phase.Then,the localized corrosion process of Mg alloy was revealed combined with the results of the monitor of corrosion process and Volta potential difference.

An in-situ study of static recrystallization in Mg using high temperature EBSD

It has been a common method to improve the mechanical properties of metals by manipulating their microstructures via static recrystallization,i.e.,through heat treatment.Therefore,the knowledge of recrystallization and grain growth is critical to the success of the technique.In the present work,by using in-situ high temperature EBSD,the mechanisms that control recrystallization and grain growth of an extruded pure Mg were studied.The experimental results revealed that the grains of priority for dynamic recrystallization exhibit fading competitiveness under static recrystallization.It is also found that grain boundary movement or grain growth is likely to show an inverse energy gradient effect,i.e.,low energy grains tend to swallow or grow into high energy grains,and grain boundaries of close to 30°exhibit superior growth advantage to others.Another finding is that{10-12}tensile twin boundaries are sites of hardly observed for recrystallization,and are finally swallowed by adjacent recrystallized grains.The above findings may give comprehensive insights of static recrystallization and grain growth of Mg,and may guide the design of advanced materials processing in microstructural engineering.

A continuous and long-term in-situ stress measuring method based on fiber optic. Part I: Theory of inverse differential strain analysis

A method for in-situ stress measurement via fiber optics was proposed. The method utilizes the relationship between rock mass elastic parameters and in-situ stress. The approach offers the advantage of long-term stress measurements with high spatial resolution and frequency, significantly enhancing the ability to measure in-situ stress. The sensing casing, spirally wrapped with fiber optic, is cemented into the formation to establish a formation sensing nerve. Injecting fluid into the casing generates strain disturbance, establishing the relationship between rock mass properties and treatment pressure.Moreover, an optimization algorithm is established to invert the elastic parameters of formation via fiber optic strains. In the first part of this paper series, we established the theoretical basis for the inverse differential strain analysis method for in-situ stress measurement, which was subsequently verified using an analytical model. This paper is the fundamental basis for the inverse differential strain analysis method.

Metal-organic-framework-derived copper-based catalyst for multicomponent C-S coupling reaction

Copper-based metal-organic frameworks(Cu-MOFs)are a promising multiphase catalyst for catalyzing C-S coupling reactions by virtue of their diverse structures and functions.However,the unpleasant odor and instability of the organosulfur,as well as the mass-transfer resistance that exists in multiphase catalysis,have often limited the catalytic application of Cu-MOFs in C-S coupling reactions.In this paper,a Cu-MOFs catalyst modified by cetyltrimethylammonium bromide(CTAB)was designed to enhance mass transfer by increasing the adsorption of organic substrates using the long alkanes of CTAB.Concurrently,elemental sulfur was used to replace organosulfur to achieve a highly efficient and atom-economical multicomponent C-S coupling reaction.

The reaction mechanism and interfacial crystallization of Al nanoparticle-embedded Ni under shock loading

The shock-induced reaction mechanism and characteristics of Ni/Al system,considering an Al nanoparticle-embedded Ni single crystal,are investigated through molecular dynamics simulation.For the shock melting of Al nanoparticle,interfacial crystallization and dissolution are the main characteristics.The reaction degree of Al particle first increases linearly and then logarithmically with time driven by rapid mechanical mixing and following dissolution.The reaction rate increases with the decrease of particle diameter,however,the reaction is seriously hindered by interfacial crystallization when the diameter is lower than 9 nm in our simulations.Meanwhile,we found a negative exponential growth in the fraction of crystallized Al atoms,and the crystallinity of B2-NiAl(up to 20%)is positively correlated with the specific surface area of Al particle.This can be attributed to the formation mechanism of B2-NiAl by structural evolution of finite mixing layer near the collapsed interface.For shock melting of both Al particle and Ni matrix,the liquid-liquid phase inter-diffusion is the main reaction mechanism that can be enhanced by the formation of internal jet.In addition,the enhanced diffusion is manifested in the logarithmic growth law of mean square displacement,which results in an almost constant reaction rate similar to the mechanical mixing process.