Low-S train and High-Energy KVPO_(4)F Cathode with Multifunctional Stabilizer for Advanced Potassium-Ion Batteries

KVPO_(4)F with excellent structural stability and high operating voltage has been identified as a promising cathode for potassium-ion batteries(PIBs),but limits in sluggish ion transport and severe volume change cause insufficient potassium storage capability.Here,a high-energy and low-strain KVPO_(4)F composite cathode assisted by multifunctional K_(2)C_(4)O_(4)electrode stabilizer is exquisitely designed.Systematical electrochemical investigations demonstrate that this composite cathode can deliver a remarkable energy density up to 530 Wh kg^(-1)with 142.7 mAh g^(-1)of reversible capacity at 25 mA g^(-1),outstanding rate capability of 70.6 mAh g^(-1)at 1000 mA g^(-1),and decent cycling stability.Furthermore,slight volume change(~5%)and increased interfacial stability with thin and even cathode-electrolyte interphase can be observed through in situ and ex situ characterizations,which are attributed to the synergistic effect from in situ potassium compensation and carbon deposition through self-sacrificing K_(2)C_(4)O_(4)additive.Moreover,potassium-ion full cells manifest significant improvement in energy density and cycling stability.This work demonstrates a positive impact of K_(2)C_(4)O_(4)additive on the comprehensive electrochemical enhancement,especially the activation of high-voltage plateau capacity and provides an efficient strategy to enlighten the design of other high-voltage cathodes for advanced high-energy batteries.

Low-cyclic fatigue properties of electrolytic low-titanium A356 alloys

The low-cycle fatigue (LCF) behavior of two kinds of A356 alloys produced by different titanium alloying methods was investigated and compared. The effect of titanium content and titanium alloying methods on LCF behavior is analyzed with plastic strain energy density. The results show that all alloys exhibit the cyclic hardening behavior. Raising Ti content can obviously increase the cyclic hardening ability. But the effect of Ti alloying method isn't distinct. Whether for the EA356 alloys or for MA356 alloys, the alloys with low titanium content have longer low-cycle fatigue life than that of the alloys with high titanium content. This is because that the alloys with low titanium content can consume higher cyclic plastic strain energy during cyclic deformation compared with alloys with high titanium content.

ATB30沥青稳定碎石基层低温抗裂性研究

为了确保沥青稳定碎石基层的低温抗裂性,对3种ATB30级配进行了冻融后低温(-15℃、-5℃、5℃、15℃)劈裂试验和低温(-15℃、-10℃、-5℃、0℃、5℃、10℃、15℃)弯曲试验,全面评价了ATB30的低温抗裂性。结果表明:采用韩国SK-70号A级沥青的ATB30脆化点温度在-5—0℃之间,其弯曲应变能与温度的关系曲线接近4次抛物线,可用于ATB30的弯曲应变能的预测和沥青路面低温抗裂设计;采用级配中值的ATB30的低温抗裂性最好。

Fabrication of nano-crystalline W-Ni-Fe pre-alloyed powders by mechanical alloying technique

Nano-crystalline pre-alloyed powders of W-Ni-Fe were fabricated by high energy ball milling mechanical alloying (MA) technique. The change of appearances and the crystallite sizes of powders before and after high energy ball milling were investigated by XRD, TOPAS P software, SEM and EDS. The results show that the nano-crystalline pre-alloyed powders can be fabricated by 5 h high energy ball milling. During the MA process, the diffusion of W, Ni and Fe happens in the process of repeated welding and fracturing. As a result, nano-crystalline supersaturated solid solutions are formed. The crystallite sizes won't be refined after 10 h ball milling. The crystallite sizes of different compositions are almost the same under the same MA condition. Due to the toughening mechanism of rare earth element, the powders of 90W-4Ni-2Fe-3.8Mo-0.2RE alloy are seriously agglomerated after ball milling compared with the other alloys. It can be concluded that the optimal sintering temperature of 90W-4Ni-2Fe-3.8Mo-0.2RE pre-alloyed powders after 15 h mechanical alloying is 1 300-1 350 ℃.

基于小冲杆试验评价钛合金的高温拉伸性能

基于能量密度等效理论,提出依据塑性弯曲阶段载荷-位移曲线,获取均匀连续、各向同性的钛合金圆片试样应力-应变曲线的小冲杆试验新方法;采用该方法预测得到不同名义屈服强度和硬化指数组合工况下假想材料的应力-应变数据,并与有限元预设曲线进行对比;基于小冲杆试验获得的TC4合金在室温、高温(400℃)下的载荷-位移曲线,采用上述方法获得该合金的真应力-真应变曲线,并与单轴拉伸真应力-应变曲线进行对比。结果表明:预测得到的假想材料应力-应变数据与有限元预设曲线之间的符合优度均高于0.96;预测获得的室温和400℃下TC4合金的真应力-真应变曲线与单轴拉伸曲线之间的符合优度均高于0.97,屈服强度和抗拉强度的最大相对误差分别为4.86%和4.63%,验证了该新方法的有效性。

卷取温度对冷轧结构级产品组织和性能的影响

本文通过产线试制和实验室模拟相结合的方式,研究了卷取温度对350 MPa级结构级镀锌产品退火后组织和性能的影响。结果表明:卷取温度从560℃提升至600℃,热轧基料第二相组织比例降低19.5%,性能下降约20 MPa,冷硬组织退火过程中的性能转变趋势温度降低20℃,使得退火工艺窗口左移。低温卷取钢卷的冷硬强度更高,且随着退火温度升高,其强度降低梯度更大,这是由于低温卷取钢卷积累了更高的位错密度和形变能,在退火初期再结晶速率更快。随着退火温度升高,第二相纤维组织逐渐消失,两种卷取温度钢卷的强度和延伸率趋于一致。基于试验结果进行的产线试制表明,提高卷取温度可以有效改善热轧基料的板形,减少边部浪形,降低冷轧生产风险,并使退火后产品性能分布范围收窄,性能控制稳定性增强。

On the calculation of the electron temperature flowfield in the DSMC studies of ionized re-entry flows

Currently available procedures of electron temperature calculations in studying ionized flows around reentry spacecraft by the direct simulation Monte Carlo(DSMC)method are analyzed.It is shown that the heat conduction of electrons is not taken into account in these procedures.The contributions of various effects to the electron energy balance are calculated by an example of the RAM-C II capsule,and a numerical solution of the electron energy conservation equation is obtained,which refines the electron temperature distribution used in the DSMC computations.A method of coupled calculation of the electron temperature within the framework of the continuum approach and modelling of ionized gas flow by the DSMC method is proposed.

An energy-based low-cycle fatigue life evaluation method considering anisotropy of single crystal superalloys

The crystal orientation significantly affects the low-cycle fatigue (LCF) propertiesof single crystal (SC) superalloys. However, the orientation-dependent LCF life model withprecise mechanisms and strong applicability is still lacking. This investigation aims at establishing an energy-based LCF life evaluation method that could consider the orientation effect. First,the influencing factors of anisotropy were identified through the literature review. Secondly, themultiaxial formula of the Ramberg-Osgood (ReO) equation was established to describe theanisotropic cyclic deformation characteristics. Furthermore, the strain energy density of SC superalloys was determined based on this equation, and the effective strain energy density wasintroduced to account for the effect of orientation. Finally, the energy-based method was validated by its application to several SC superalloys. Results showed that the crystallographicorientation with a lower Young’s modulus usually exhibits better LCF resistance. This phenomenon could be attributed to the different values of strain energy density dissipated in one cycle.The multiaxial ReO relationship could capture the anisotropic cyclic deformation response ofDD6. Compared with the classical methods, the energy-based model is favored by its precisemechanism and strong applicability. And it also exhibited better prediction accuracy. Most datapoints of different crystallographic orientations lay within the
3 error band.

High-voltage,low-temperature supercapacitors enabled by localized“water-in-pyrrolidinium chloride”electrolyte

Aqueous electrolytes offer superior prospects for advanced energy storage.“Water-in-salt”(WIS)electrolytes exhibit a wide electrochemical stability window(ESW),but their low conductivity,high viscosity,and precipitation at low temperatures restrict their application.Herein,we report a novel localized“water-in-pyrrolidinium chloride”electrolyte(LWIP;1 mol/L,N-propyl-N-methylpyrrolidinium chloride/(water and N,Ndimethylformamide,1:4 by molality))enabling high-voltage,low-temperature supercapacitors(SCs).The greatly improved ESW(3.451 V)is mainly attributed to the strong solvation between Cl-and water molecules,which broadens the negative stability.This water-binding mechanism is very different from that of a WIS electrolyte based on alkali metal salt.SCs using LWIP electrolytes not only yield a high operating voltage of 2.4 V and excellent capacity retention(82.8%after 15,000 cycles at 5 A g^(-1))but also operate stably at-20℃.This work provides new approaches for the design and preparation of novel electrolytes.

Energy absorption potential of concrete floors containing secondary （shrinkage and temperature） reinforcements

This paper experimentally investigates the namely, normal density concrete and structural low-density energy absorption potential of two types of concrete floors, concrete, containing secondary （shrinkage and temperature） reinforcements. The test program considered the following secondary reinforcements： 1） traditional welded-wire steel mesh, 2） steel fiber and 3） poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete- secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a ＂work index＂ value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.

生物质低温热解炭化特性的实验研究

采用固定床和螺旋式2种实验装置,以稻秆、桑树枝、杨树枝和竹子等4种生物质为研究对象,在热解温度为250～300℃、停留时间为10～30min条件下进行生物质低温热解炭化特性的实验研究。结果表明:与生物质原料相比,生物质炭的表观体积缩小,外形收缩,颜色有不同程度加深,O/C质量比下降,热值得到大幅度提高,疏水性和研磨特性得到显著改善。随着热解温度和停留时间的增加,固体产物质量收率不断降低,较高的热解温度有利于气体的生成。桑树枝炭和稻秆炭的质量收率和能量收率随着热解温度的升高不断降低,且在相同热解条件下,生物质的能量收率始终高于质量收率。随着热解温度和停留时间的增加,生物质炭的能量密度不断增加;较低热解温度时,停留时间越长,生物质炭的能量密度增幅越大,但在较高热解温度下,停留时间对生物质炭能量密度增加的效果并不明显。

花岗岩样品高温后损伤的试验研究

对河南省某地产25块花岗岩样品进行高温预热处理,测量了加温前后弹性纵波波速,并对样品进行单轴压缩应力-应变全过程试验。通过以上试验,给出如下结果:温度对岩石损伤变化的作用;温度对岩石裂隙密度和损伤应变能释放率的影响。实验结果验证了花岗岩的塑性应变主要与偏斜应力产生的形状改变比能有关,而与体积改变比能的关系不大。

沥青混合料低温抗裂性能评价指标

为了确保沥青路面在低温下的抗裂稳定性 ,就必须用实验方法来评定它在低温条件下的性能 ,然而到目前为止仍未有统一方法 ,因此尽快找到一种科学而又实际的评价指标 ,对于沥青路面低温缩裂问题的解决有着深远的意义。以沥青混合料低温抗裂性评价指标作为研究对象 ,在分析目前一些评价方法的基础上 ,通过对不同品种沥青混合料试验结果进行分析总结 ,发现沥青混合料的低温压缩应变能指标 ,更能反映不同沥青混合料的低温性能 ;对于低温蠕变试验 ,采用 0℃、10 %破坏荷载应力水平更适用于不同沥青混合料 ,利用 0℃压缩应变能作为沥青混合料低温抗裂性能评价指标 ,方法简便易于推广。

沥青混合料低温抗裂性评价方法研究

一般评价沥青混合料低温抗开裂性能可从两方面进行 ,一方面看其在低温下的变形能力 ;另一方面看其在低温断裂时所能承受的断裂拉力的大小 .但以往多以其变形能力这一单一指标来衡量沥青混合料的抗开裂能力是不全面的 .为此从如何综合反应沥青混合料断裂时的应力、应变大小的角度出发 ,提出了评价沥青混合料低温抗开裂性能的压缩应变能指标及计算方法 ,并对两种改性沥青混合料进行了冻断试验和压缩应变能试验 ,比较了它们的试验结果 .

Ti6Al4V合金的低温超塑性拉伸变形行为

在700℃-850℃的温度范围内对Ti-6%AL-4%V(质量分数)合金板材进行超塑性拉伸试验,研究了应变速率为3×10^(-4)-5×10^(-3)_S^(-)1条件下的拉伸变形行为.结果表明:Ti6Al4V合金在空气中表现出良好的低温超塑性变形能力.在800℃初始应变速率(?)=5×10^(-4)S^(-1)条件下,延伸率达到536%.在较低的700℃下变形((?)=5×10^(-4)s^(-1),延伸率仍然超过了300%.在整个变形温度区间内,应变速率敏感性指数m均为0.3左右,最大值为0.63.在850℃变形激活能与晶界自扩散激活能十分相近,表明晶界扩散控制的晶界滑动是超塑性变形的主要机制.在700-750℃,变形激活能远大于晶界自扩散激活能,位错运动是激活能升高的原因.在800℃变形的激活能介于两者之间,表明随着温度的降低变形机制逐渐发生改变.

动静组合加载下岩石破坏的应变能密度准则及突变理论分析

阐述了岩石在动静组合载荷作用下使用应变能密度定义破坏准则的适用性。分析认为,岩石破坏的应变能密度的临界值与岩石破坏之前的不可逆变形过程和外界条件有关,而不可逆变形过程主要是由于岩石的非弹性变形、损伤和其他内部耗散机制引起的,且反映静水压力的体积变形能在某些应力状态条件下的岩石破坏中是不能忽略的。提出用机械模型来反映动静组合加载下岩石单元体弹性的劣化和非弹性变形的产生以及加载速率的影响,并以机械模型为基础,求出受一维静载岩石在动载作用下破坏应变能密度的临界值。同时,根据静力预加载结构的冲击屈曲突变模型,建立了静加载岩石系统的冲击破坏模型,进一步分析了动静组合加载下岩石的破坏。最后,采用低周疲劳加载方法在Instron电液饲服控制材料试验机上进行了红砂岩中应变率下的动静组合加载破坏试验,对应变能密度准则和突变理论模型进行了验证。结果表明,理论模型与试验结果有较好的一致性。

用弯曲应变能方法评价沥青混合料的低温抗裂性能

通过对沥青混合料低温开裂机理的分析和对大量试验结果的总结 ,以弯曲应变能密度临界值为指标来评价沥青混合料的低温抗裂性能 .首先 ,分析了沥青混合料低温开裂机理 ;其次 ,在MTS81 0材料试验系统上进行了 0℃下的沥青混合料的低温弯曲试验 ;最后 ,用灰关联的方法分析了沥青混合料的弯拉强度、临界弯拉应变、油石质量比、表观密度及所用沥青的针入度等指标对混合料的应变能密度临界值的影响程度 .研究表明 ,一般情况下 ,沥青混合料储存的弹性应变能越多 ,沥青混合料的低温抗裂性能就越好 ;由于沥青混合料的应变能密度临界值指标是混合料临界弯拉应变和弯拉强度 2个指标的综合 ,用它来评价沥青混合料的低温抗裂性能更加科学 ;低温时沥青混合料的允许变形能力较差 。

Superpave沥青混合料低温抗裂性评价方法

采用低温弯曲破坏试验和约束试件温度应力试验,评价了Superpave沥青混合料的低温抗裂性,并对两种试验方法及其评价指标进行对比分析。研究结果表明:约束试件温度应力试验中的冻断温度和转折点温度可以较好的评价Superpave沥青混合料的低温抗裂性;弯曲破坏试验中用弯曲应变能密度作为评价指标可以很好表征Superpave沥青混合料的低温性能,并且与约束试件温度应力试验结果基本吻合。

基于低温性能的橡胶颗粒环氧沥青混合料研究

为了分析橡胶颗粒对环氧沥青混合料低温性能的改善作用,在选择形状特征及硬度合适的橡胶颗粒的前提下,基于抗弯拉强度、最大弯拉应变、弯曲劲度模量、脆化点温度及应变能密度对不同橡胶颗粒体积掺量下的环氧沥青混合料的低温性能进行研究,并通过室内试验对不同橡胶颗粒体积掺量下的环氧沥青混合料的水稳定性及高温性能进行验证.结果表明:橡胶颗粒的细长扁平颗粒含量越小、邵尔A型硬度越大,橡胶颗粒环氧沥青混合料的压实效果及抗松散性越好;体积掺量合适的橡胶颗粒对环氧沥青混合料的抗弯拉强度、水稳定性及高温性能影响不大,但能显著提高其低温变形能力,降低其脆化点温度,改善其低温性能;在-15℃时,5%橡胶颗粒体积掺量下的环氧沥青混合料相对未掺加橡胶颗粒的环氧沥青混合料,应变能密度提高了108.0%.

纤维沥青混合料最佳纤维掺量的确定

为确定纤维沥青混合料中纤维的最佳掺量,通过对不添加纤维和各添加0.3%时的4种纤维沥青混合料进行高温车辙试验、水稳定性试验、低温弯曲试验和疲劳试验,对同一纤维不同含量的纤维沥青混合料进行低温弯曲试验,并对纤维沥青混合料破坏时的应变能进行分析,同时分析抗弯拉强度、弯拉应变和弯曲劲度模量是否在正常使用范围。结果表明:沥青混合料在添加纤维后高温性能和低温性能明显提高,并且各纤维都存在最佳掺量;应变能可以较为明显地反映纤维变化对混合料整体性能的影响,确定的纤维最佳掺量更精确,并且在应变能确定的最佳纤维掺量下,混合料的其他技术指标均处于较为理想的状态。