Interaction of crack with twins in hot-rolling AZ31 magnesium alloys during in-situ TEM straining experiments

In-situ straining experiments in transmission electron microscopy were performed to investigate the propagation of crack,twinning and interaction of crack with twins. Lots of micro-twins were observed in the deformation band near the tip of crack. The stress is relaxed by the formation of micro-twins and the densely developed micro-twins prevent the growth of crack from the deformation band,subsequently the cracks extend into adjacent grains across grain boundaries,and grow along cleavage plane. Multiple twins are observed in hot-rolling AZ31 magnesium alloys,when cracks propagate into twins through twin grain boundaries(GBs),the direction of growth deviates. It is concluded that twins,especially multiple twins effectively baffle the development of crack.

In situ TEM investigation of electron irradiation and aging-induced high-density nanoprecipitates in an Mg-10Gd-3Y-1Zn-0.5Zr alloy

In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr(GWZ1031K,wt.%)alloy to improve the hardness.The results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250℃ is 1.64 GPa,which is approximately 64% higher than that of the samples before being treated.It is mainly attributed to γ'precipitates on the basal plane after irradiation and the high-density nanoscale β'precipitates on the prismatic plane after aging,which should be closely related to the irradiation-induced homogenous clusters.The latter plays a key role in precipitation hardening.This result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging.

In-situ electrochemical study on the eff ects of Fe(Ⅲ)on kinetics of pyrite acidic pressure oxidation

Fe(Ⅲ)has been proved to be a more eff ective oxidant than dissolved oxygen at ambient temperature,however,the role of Fe(Ⅲ)in pyrite acidic pressure oxidation was rarely discussed so far.In this paper,in-situ electrochemical investigation was performed using a flow-through autoclave system in acidic pressure oxidation environment.The results illustrated that increasing Fe(Ⅲ)concentrations led to raising in redox potential of the solution,and decreased passivation of pyrite caused by deposition of elemental sulfur.Reduction of Fe(Ⅲ)at pyrite surface was a fast reaction with low activation energy,it was only slightly promoted by rising temperatures.While,the oxidation rate of pyrite at all investigated Fe(Ⅲ)concentrations increased obviously with rising temperatures,the anodic reaction was the rate-limiting step in the overall reaction.Activation energy of pyrite oxidation decreased from 47.74 to 28.79 kJ/mol when Fe(Ⅲ)concentration was increased from 0.05 to 0.50 g/L,showing that the reaction kinetics were limited by the rate of electrochemical reaction at low Fe(Ⅲ)concentrations,while,it gradually turned to be diffusion control with increasing Fe(Ⅲ)concentrations.

In-situ TEM observation of the evolution of helium bubbles in Mo during He^(+)irradiation and post-irradiation annealing

The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy(TEM)during 30 keV He^(+)irradiation(at 673 K and 1173 K)and post-irradiation annealing(after 30 keV He^(+)irradiation with the fluence of 5.74×10^(16)He^(+)/cm^(2)at 673 K).Both He^(+)irradiation and subsequently annealing induced the initiation,aggregation,and growth of helium bubbles.Temperature had a significant effect on the initiation and evolution of helium bubbles.The higher the irradiation temperature was,the larger the bubble size at the same irradiation fluence would be.At 1173 K irradiation,helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size,which would induce the formation of microcracks.At the same time,the geometry of helium bubbles changed from sphericity to polyhedron.The polyhedral bubbles preferred to grow in the shape bounded by{100}planes.After statistical analysis of the characteristic parameters of helium bubbles,the functions between the average size,number density of helium bubbles,swelling rate and irradiation damage were obtained.Meanwhile,an empirical formula for calculating the size of helium bubbles during the annealing was also provided.

用TEM分析材料在实验教学中的实践

透射电子显微镜的快速发展使人类对客观世界的认识深入到了原子尺度。目前,透射电子显微镜的分辨率已经达到了亚埃级别,是材料研究领域十分重要的测试表征手段。针对材料类本科专业实验教学的特点,以分析金纳米颗粒的微观结构为实例,从理论讲解、实验观摩到结果分析与讨论三个方面开展了透射电子显微分析的实验教学工作,使学生理解透射电子显微镜的基本原理、功能和应用。

IN-SITU OBSERVATION OF S'PHASE IN Al-Li BASE ALLOY USING TEM SERIAL ROTATION TECHNIQUE

An in situ observation of the s'phase morphology and its orientation with the matrix in an Al-Li base alloy was carried out by means of double-tilt rotating around[220]a in a transmission electron microscope(TEM).The results show that the s'phase precipitates in the form of bundles.The units of s'phase are lath-shaped,grow along the<100>,orientation,and have habit planes of{210}*.Many units of the s'phase grow in the same orientation and get together to form a plate-shaped bundle of s'phase laths which lie on the{110}a planes.

国产矿井瞬变电磁仪的性能试验研究——与进口Terratem仪器对比

为评价国产本安型矿井瞬变电磁仪YCS40(A)的稳定性及对异常体的分辨能力,特将其同井下使用较频繁的进口仪器TERRATEM做了试验对比。试验中,进行了二款仪器使用各自的常规装置展开单点背景值实验对比、对异常体的分辨能力实验对比和抗干扰能力等模拟实验对比。并在同一感应电动势-衰减时间(V-T)的坐标下考察二者的关断时间、感应电动势的幅值、光滑程度及衰减速率和尾期信号的抗干扰度等衡量仪器性能的硬性指标。最后通过井下实际工程实例剖面测量对比,表明国产YCS40(A)矿井瞬变电磁仪具有稳定性较好、抗干扰能力强、对异常体具有较强的分辨能力等优点,同时也感到该仪器探测窗口较少、感应时间短,当井下异常体埋深超过120 m时其分辨力的不足。

跨季节土壤蓄冷-土壤源热泵系统长期运行特性实验研究

为解决土壤源热泵在长期运行条件下土壤热失衡导致的运行效率下降问题,针对夏热冬冷地区的特点,提出一种利用室外风机盘管将冬季或过渡季室外空气中的冷量存储于土壤中的跨季节蓄冷-土壤源热泵系统。利用地埋管换热系统的相似模型实验台,进行了系统运行3年的供冷、供暖、蓄冷工况实验,综合分析了埋管进出口水温、气温、土壤温度、土壤及埋管换热量、单位埋深换热量等参数,研究系统的长期运行特性。研究显示:3年的土壤平均温度分别上升0.14℃、0.22℃、0.20℃,总体来说升高幅度较小;蓄冷时的室外气温越低、土壤与室外空气的温差越大,蓄冷效果越好;埋管进出口平均温差、土壤平均温度变化、土壤换热量、埋管换热量、单位埋深换热量的大小关系一致。研究结果表明,跨季节蓄冷维持了土壤的长期热平衡,系统的长期运行效果较好。

Coupling Sb_(2)WO_(6)microflowers and conductive polypyrrole for efficient potassium storage by enhanced conductivity and K^(+) diffusivity

Although metal oxide compounds are considered as desirable anode materials for potassium-ion batteries(PIBs)due to their high theoretical capacity,the large volume variation remains a key issue in realizing metal oxide anodes with long cycle life and excellent rate property.In this study,polypyrroleencapsulated Sb_(2)WO_(6)(denoted Sb_(2)WO_(6)@PPy)microflowers are synthesized by a one-step hydrothermal method followed by in-situ polymerization and coating by pyrrole.Leveraging the nanosheet-stacked Sb_(2)WO_(6)microflower structure,the improved electronic conductivity,and the architectural protection offered by the PPy coating,Sb_(2)WO_(6)@PPy exhibits boosted potassium storage properties,thereby demonstrating an outstanding rate property of 110.3 m A h g^(-1)at 5 A g^(-1)and delivering a long-period cycling stability with a reversible capacity of 197.2 m A h g^(-1)after 500 cycles at 1 A g^(-1).In addition,the conversion and alloying processes of Sb_(2)WO_(6)@PPy in PIBs with the generation of intermediates,K_(2)WO_(4)and K_(3)Sb,is determined by X-ray photoelectron spectroscopy,transmission electron microscopy,and exsitu X-ray diffraction during potassiation/depotassiation.Density functional theory calculations demonstrate that the robust coupling between PPy and Sb_(2)WO_(6)endues it with a much stronger total density of states and a built-in electric field,thereby increasing the electronic conductivity,and thus effectively reduces the K^(+)diffusion barrier.

In-situ isothermal aging TEM analysis of a micro Cu/ENIG/Sn solder joint for flexible interconnects

Sn/ENIG has recently been used in flexible interconnects to form a more stable micron-sized metallurgical joint,due to high power capability which causes solder joints to heat up to 200℃.However,Cu_(6)Sn_(5)which is critical for a microelectronic interconnection,will go through a phase transition at temperatures between 186 and 189℃.This research conducted an in-situ TEM study of a micro Cu/ENIG/Sn solder joint under isothermal aging test and proposed a model to illustrate the mechanism of the microstructural evolution.The results showed that part of the Sn solder reacted with Cu diffused from the electrode to formη´-Cu_(6)Sn_(5)during the ultrasonic bonding process,while the rest of Sn was left and enriched in a region in the solder joint.But the enriched Sn quickly diffused to both sides when the temperature reached 100℃,reacting with the ENIG coating and Cu to form(Ni_(x)Cu_(1-x))_(3)Sn_(4),AuSn_(4),and Cu_(6)Sn_(5)IMCs.After entering the heat preservation process,the diffusion of Cu from the electrode to the joint became more intense,resulting in the formation of Cu_(3)Sn.The scallop-type Cu_(6)Sn_(5)and the seahorse-type Cu_(3)Sn constituted a typical two-layered structure in the solder joint.Most importantly,the transition betweenηandη’was captured near the phase transition temperature for Cu_(6)Sn_(5)during both the heating and cooling process,which was accompanied by a volume shifting,and the transition process was further studied.This research is expected to serve as a reference for the service of micro Cu/ENIG/Sn solder joints in the electronic industry.

利用TEM研究叶蛇纹石晶胞参数随温压条件的变化特征

对不存在特征变质矿物的蛇纹岩进行温压条件的限定是一个难题,因为其中的主要矿物叶蛇纹石可以在约400~700℃,1.0~5.0 GPa以上的温压范围内稳定存在。天然样品观察和高压实验结果都表明,叶蛇纹石的a轴晶胞参数与温度、压力相关,对温度、压力条件具有一定的指示意义。本文使用TEM测量全岩体系(各种化学成分都含有的体系)下通过高压实验得到的叶蛇纹石的晶体结构,与前人在Mg O-SiO_2-H_2O(MSH)体系下高压合成的叶蛇纹石的晶体结构进行对比,探讨全岩体系下叶蛇纹石的a轴晶胞参数对应的m值与温度、压力的相关关系。本次研究表明:(1)叶蛇纹石的m值随着压力的升高而升高;(2)叶蛇纹石中铝含量的升高使得m值往高温方向迁移;(3)温度升高,叶蛇纹石的m值变小,含水量相对升高。

Al基非晶合金原位TEM拉伸塑性形变研究

为探究Al基非晶合金小尺度变形行为,首次用热双金属片拉伸装置实现Al_(86)Ni_(7)Er_(5)Co_(1)La_(1)非晶合金纳米线原位TEM拉伸观察。结果表明:Al_(86)Ni_(7)Er_(5)Co_(1)La_(1)非晶合金纳米线室温下表现出明显尺寸效应,拉伸断裂应变高达14.6%;选区电子衍射分析表明,该成分非晶合金纳米线在变形过程中始终保持非晶状态,未发生形变诱发纳米晶现象。

Interface charges boosted ultrafast lithiation in Li_4Ti_5O_12 revealed by in-situ electron holography

It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.

Assessment of recoverable oil and gas resources by in-situ conversion of shale——Case study of extracting the Chang 7_(3) shale in the Ordos Basin

The purpose of this study is to investigate the entire evolution process of shales with various total organic contents(TOC)in order to build models for quantitative evaluation of oil and gas yields and establish methods for assessing recoverable oil and gas resources from in-situ conversion of organic matters in shale.Thermal simulation experiments under in-situ conversion conditions were conducted on Chang 7_(3) shales from the Ordos Basin in a semi-open system with large capacity.The results showed that TOC and R_(o) were the key factors affecting the in-situ transformation potential of shale.The remaining oil and gas yields increased linearly with TOC but inconsistently with R_(o).R_(o) ranged 0.75%—1.25%and 1.05%—2.3%,respectively,corresponding to the main oil generation stage and gas generation stage of shale in-situ transformation.Thus a model to evaluate the remaining oil/gas yield with TOC and R_(o) was obtained.The TOC of shale suitable for in-situ conversion should be greater than 6%,whereas its R_(o) should be less than 1.0%.Shales with 0.75%(R_(o))could obtain the best economic benefit.The results provided a theoretical basis and evaluation methodology for predicting the hydrocarbon resources from in-situ conversion of shale and for the identification of the optimum“sweet spots”.The assessment of the Chang 7_(3) shale in the Ordos Basin indicated that the recoverable oil and gas resources from in-situ conversion of organic matters in shale are substantial,with oil and gas resources reaching approximately 450×10^(8) t and 30×10^(12)m^(3),respectively,from an area of 4.27×10^(4) km^(2).

Thermal and saline tolerance of Antarctic krill Euphausia superba under controlled in-situ aquarium conditions

As a key species of the Southern Ocean ecosystem,the thermal and saline tolerances of Antarctic krill(Euphausia superb a Dana)are relatively unknown because of the challenging environment and complicated situations needed for observation have inhibited in-situ experiments in the field.Hence,the thermal and saline tolerance of krill were examined under in-situ aquarium conditions with different controlled scenarios.According to the experiments,the critical lethal times of krill were 24h,2h and 0.5h under 9℃,12℃,and 15℃,respectively,and the estimated 50%lethal times were about 17.1 h and 1.7 h under 12℃and 15℃,respectively.Additionally,the critical lethal times(the estimated 50%lethal times)of krill were approximately 14h and 0.5h(about 22.9 h and 1.7 h)of salinity under 19.7 and 15.9,respectively.The observed critical and 50%lethal times of krill were 0.5 h and approximately 1.4 h,respectively,salinity under 55.2.The critical and 50%lethal temperatures of krill were 13℃and approximately 14.2℃,respectively.Additionally,the critical and 50%lethal salinity was 19.6 and approximately 17.5 for the lower saline(below normal oceanic salinity[34.4])environment and 50.3 and approximately 53.2 for the higher saline(above 34.4)environment,respectively.The upper thermal and saline preferences of krill can be considered 6℃and 26.8 to 41.2,respectively.These results can provide potential scenarios for predicting the possible fate of this key species in the Southern Ocean.

Determination of the Coreactant Level in Crosslinked Polyurethane System by FTIR

Infrared spectrum is a general quantitation method which can be used to determine the concentration of a certain component in mixture.We proposed that it could also be used to determine the coreactant level of a reactive system.A two-part polyurethane film was used as a model system.The results showed that the height ratio of ring mode signal in urea and C—O signal in polyester polyol can be used to calculate the ratio of the two reactants.The assignments of the peaks were studied by in-situ reaction monitoring with moisture level changes and deuteration methods.The applicable conditions of this calibration curves were also discussed.

An Over-Moded TEM Cell System for <i>in vivo</i>Exposure at 2.45 GHz

A TEM cell designed to operate at 900 MHz for exposing small-restrained animals (e.g. mice) has been theoretically, numerically and experimentally characterized at 2.45 GHz, which is the central frequency of the WiFi protocol. This study aims at evaluating the influence of higher order modes on the field homogeneity. The results demonstrate the superimposition of a tolerable standing wave, due to reflections at the cell terminations, and a slight beat wave due to the interference between different modes. Nevertheless, the final outcome is that the system can still be efficiently used to expose small animals in specific WiFi channels, provided they are properly placed in correspondence to the maxima of the electric field along the guide length.

Improved Methods for In-situ Measurement Railway Noise Barrier Insertion Loss

Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ experiments.However,there are no universally acknowledged receiver positions for the evaluation of the barrier performance,a fact which may be leading to uncertainty over the noise reduction capabilities of available barriers.In terms of the descriptor of the barrier performance,the general recommendation is the A-weighted sound pressure level,although the latter is considered to underestimate low frequencies for railway noise barrier.Thus,in this study,the comparison of receiver positions and the descriptors among existing Chinese,ISO and European standards were investigated.Based upon a combination of diffraction theory and standards,a rearrangement of receiver positions and one-third-octave-band analysis were proposed.In addition,in line with improved methods,an in-situ measurement of insertion loss for a 1.5 mhigh railway noise barrier was designed and conducted.The results of the experiment validate as effective and applicable the new receiver positions.These results also suggest that one-third-octave-band analysis is indispensable.

A full-scale field experiment to study the thermal-deformation process of widening highway embankments in permafrost regions

As one of the widely used upgrading way in road engineering, the widening embankment(WE) has suffered evident differential deformation, which is even severer for highway in permafrost regions due to the temperature sensitivity of frozen soil and the heat absorption effect of the asphalt pavement. Given this issue, a full-scale experimental highway of WE was performed along the Qinghai-Tibet Highway(QTH) to investigate the differential deformation features and its developing law. The continuous three years' monitoring data taken from the experimental site, including the ground temperature and the layered deformation of WE and original embankment(OE), were used to analyze the thermal-deformation process. The results indicate that the widening part presented the remarkable thermal disturbance to the existing embankment(EE). The underlying permafrost was in a noteworthy degradation state, embodying the apparent decrease of the permafrost table and the increase of the ground temperature. Correspondingly, the heat disruption induced by widening led to a much higher deformation at the widening side compared to the original embankment, showing a periodic stepwise curve. Specifically, the deformation mainly occurred in the junction of the EE and the widening part, most of which was caused by the thawing consolidation near the original permafrost table. In contrast, the deformation of EE mainly attributed to the compression of the active layer. Furthermore, it was the deformation origination differences that resulted in the differential deformation of WE developed gradually during the monitoring period, the maximum of which reached up to 64 mm.

中心回线TEM勘探中的野外试验要点

电磁勘探施工前的野外试验,对完成地质任务、评估解释结果具有重要意义。使用V8多功能电法测量系统,以王家岭煤田水文地质勘探为例,首先利用地层电性参数,给出了达到预定勘探深度需要的观测时间估算方法;再根据测区噪声电平,决定发射回线边长和电流;波形检测后,经孔旁地质效果试验确认观测时间。信噪比,一致性、稳定性经过试验符合探测精度的要求。