Rattling-like behavior and band convergence induced ultra-low lattice thermal conductivity in MgAl_(2)Te_(4) monolayer

Inspired by the excellent stability exhibited by experimentally synthesized two-dimensional(2D)MoSi_(2)N_(4) layered material,the thermal and electronic transport,and thermoelectric(TE)properties of MgAl2Te4 monolayer are systematically investigated using the First-principles calculations and Boltzmann transport theory.The mechanical stability,dynamic stability,and thermal stability(900 K)of the MgAl_(2)Te_(4) monolayer are demonstrated,respectively.The MgAl_(2)Te_(4) monolayer exhibits a bandgap of 1.35 eV using the HSE06 functional in combination with spin-orbit coupling(SOC)effect.Band convergence in the valence band is favorable to improve the thermoelectric properties.The rattling thermal damping effect caused by the weak bonding of Mgsingle bondTe bonds in MgAl2Te4 monolayer leads to ultra-low lattice thermal conductivity(0.95/0.38 W/(m·K)@300 K along the x-/y-direction),which is further demonstrated by the phonon group velocities,phonon relaxation time,Grüneisen parameters,and scattering mechanisms.The optimal zT of 3.28 at 900 K is achieved for the p-type MgAl_(2)Te_(4) monolayer,showing the great promising prospect for the excellent p-type thermoelectric material.Our current work not only reveals the underlying mechanisms responsible for the excellent TE properties,but also elaborates on the promising thermoelectric application of MgAl_(2)Te_(4) monolayer material at high temperature.

Variations induced in human erythrocytes by ultra-low X-ray doses

In this work, the effect of different ultra-low doses of X-ray on human erythrocytes was investigated. Also, the effect of ascorbic acid added to erythrocyte suspension before X-rays was studied. The mean X-ray exposure level was about 10 μGy/h. Samples of erythrocytes suspension with and without ascorbic acid was exposed to X-ray doses in the range from 2.5 to 20 μGy. The obtained results showed pronounced radio-hemolysis of erythrocytes at doses starting from nearly 7.5 μGy. The effect was enhanced, for low doses, when ascorbic acid of relatively high concentration was added to erythrocyte samples. The changes may be attributed to a dose-dependent damage by oxidative stress at the level of the whole cell and to the production of reactive oxygen species, which can cause this damage. It may be concluded that X-rays, even at low levels of exposure, can induce oxidizing effect on erythrocytes. Accordingly, such results should be taken into account for workers operating on X-rays equipments.

Ester-based anti-freezing electrolyte achieving ultra-low temperature cycling for sodium-ion batteries

With the continuous advancement of industrialization,sodium-ion batteries(SIBs)need to operate in various challenging circumstances,particularly in extremely cold conditions.However,at ultra-low tem-peratures,the reduced ionic conductivity and sluggish Na+migration of commonly carbonate-based elec-trolytes will inevitably lead to a sharp decrease in the capacity of SIBs.Herein,we design a carboxylate ester-based electrolyte with excellent ultra-low temperature performance by straightforward cosolvent strategy.Due to the low viscosity,melting point,and sufficient ionic conductivity of the designed elec-trolyte,the resulting Na||Na_(3)V_(2)(PO_(4))_(2)O_(2)F can achieve the capacity retention of 96%(100 cycles at 0.1 C)at-40℃ and can also operate stably even at-50℃.Besides,galvanostatic intermittent titration tech-nique(GITT),ex-situ X-ray photoelectron spectroscopy(XPS),and high-resolution transmission electron microscopy(TEM)tests are employed to analyze and confirm that the carboxylate ester-based electrolyte promotes robust and uniform cathode/electrolyte interface layer formation and accelerates ion diffusion kinetics,which collectively facilitates the better low-temperature performance.In addition,the assembled hard carbon||NVPOF full cells further prove the practicability of the carboxylate ester-based electrolyte at low-temperature,which delivers high discharge capacity of 108.4 and 73.0 mAh g^(-1) at-25 and-40℃.This work affords a new avenue for designing advanced low-temperature electrolytes for SIBs.

运动感应涡流磁场检测中的激励磁场优化设计方法

在生产或使用过程中,薄金属板中会产生微缺陷(微颗粒或气孔),这些微缺陷的数目及尺寸决定了薄金属板的品质,影响其使用寿命和安全系数.因此,对微缺陷进行定量和准确的表征是保证薄金属板产品品质与使用安全的必要条件.电磁检测中的运动感应涡流磁场检测可应用于检测导电非导磁材料中的缺陷.本文通过模拟和实验结果显示,当提离距离、永磁体表面剩磁确定时,永磁体尺寸与缺陷检测信号幅值正相关.另外,提出一种运动感应涡流磁场检测中激励磁场的优化方法,由该方法产生的两种永磁体阵列相比于同体积、同表面剩磁的简单永磁体,产生的缺陷检测信号幅值更高,因而可以提高检测的灵敏度.

碳纤维复合材料涂层厚度涡流法测量的研究

基于涡流法对碳纤维复合材料涂层厚度的测量进行研究,结合材料属性及组织特点,利用ANSYS软件对非磁性超低电导率基体材料上涂层厚度的涡流法测量作二维仿真,然后采用电导率混合分块赋值的方法来模拟材料电导率不均匀性并进行有限元分析和实验验证,仿真计算与实验结果吻合较好。分析结果表明通过选择合适的检测频率可以使探头线圈阻抗与涂层厚度有很好的线性相关性和检测分辨率。该方法很好地反映了材料属性的特点,提高了碳纤维复合材料涂层涡流测厚仿真的准确性,为碳纤维复合材料涂层厚度的涡流法高精度测量提供了可靠的理论依据和技术支持。

锰系无磁铸铁的研制

对锰系无磁铸铁的形成机理进行了分析,指出了锰及其它元素在无磁铸铁中的作用,并对锰系无磁铸铁的成分进行了优选,确定了锰系无磁铸铁的金相组织特征、力学性能和电工性能。

混合电磁结构磁性部分元等效电路建模技术

磁性材料在电磁结构中广泛应用,而传统(标准)部分元等效电路(partial element equivalent circuit,PEEC)方法对包含磁性材料的各种结构进行分析已无能为力。该文提出了基于几何平均距离和空间磁介质均匀化处理的磁性PEEC建模方法(magnetic PEEC,MagPEEC),根据磁性材料边界单元切向磁通密度在边界两边的关系得到了载流磁性材料表面磁化面电流和传导电流的耦合系数矩阵,给出了仅用传导电流表示的系统方程。对矩形单元之间、矩形单元与线单元之间、线单元与线单元之间的各种几何平均距离(geometrical mean distance,GMD)进行了分析,得到了相应的计算公式,在此基础上导出了平均切向磁感应强度的计算公式,并应用于磁性材料的MagPEEC建模。通过有限元(finite element method,FEM)方法对两邻近金属板的新型MagPEEC建模方法进行了验证。

具有有限铁磁层厚度的磁性双隧道结中的隧穿电导和磁电阻

在FM/I/NM/I/FM磁性双隧道结研究的基础上,进一步考虑了外加有限厚的非磁金属(NM)覆盖层的情况,这时磁性双隧道结的结构变为NM/FM/I/NM/I/FM/NM.此处,FM、I和内NM都具有有限厚度,而在理论处理中,外NM被看做是无限厚的.对FM厚度于磁性双隧道结中自旋极化电子输运性质(特别是隧穿磁电阻)的影响做了研究.用Slonczewski近自由电子模型所得到的计算结果表明,FM厚度的变化会引起隧穿电阻和隧穿磁电阻振荡;当FM厚度取适当值时,会得到比FM/I/NM/I/FM更大的隧穿磁电阻.

采用精益六西格玛方法提高无磁钢A磁导率合格率

太钢型材厂针对无磁钻铤用钢A磁导率合格率低的状况,特立项采用精益六西格玛方法,实施＂定义—测量—分析—改进—控制＂流程,提高无磁钻铤用钢A磁导率合格率。在实施过程中,按照无磁钻铤用钢磁导率合格率为80%的现状与潜在最佳值之间的差距可提高70%~90%的原则,确定提高磁导率合格率83.3%的目标,对无磁钢关键过程进行改进,并严格控制工艺参数,最终使无磁钢A系列磁导率合格率已基本稳定,2010年第四季度此值保持在97%以上,全年平均达到95.86%。

Mn系无磁球墨铸铁的研制

为寻找一种原材料来源较广、成本较低的无磁球墨铸铁材料，采取合金优化、球化处理、硅铁和铝联合孕育以及热处理技术，对Mn系无磁球墨铸铁进行了研制。结果表明，恰当的Si／in（0．5～0．6）和铜（1．5％～3％）配合、硅铁和铝联合孕育处理，可在铸态下获得性能优良的无磁球墨铸铁；热处理可以进一步改善Mn系无磁球墨铸铁的磁导率、力学性能和机械加工性能。

High conductive graphene assembled films with porous micro-structure for freestanding and ultra-low power strain sensors

Graphene emerges as an ideal material for constructing high-performance strain sensors,due to its superior mechanical property and high conductivity.However,in the process of assembling graphene into macroscopic materials,its conductivity decreases significantly.Also,tedious fabrication process hinders the application of graphene-based strain sensors.In this work,we report a freestanding graphene assembled film(GAF)with high conductivity((2.32±0.08)×105 S m-1).For the sensitive materials of strain sensors,it is higher than most of reported carbon nanotube and graphene materials.These advantages enable the GAF to be an ultra-low power consumption strain sensor for detecting airflow and vocal vibrations.The resistance of the GAF remains unchanged with increasing temperature(20-100℃),exhibiting a good thermal stability.Also,the GAF can be used as a strain sensor directly without any flexible substrates,which greatly simplifies the fabrication process in comparison with most reported strain sensors.Additionally,the GAF used as a pressure sensor with only^4.7μW power is investigated.This work provides a new direction for the preparation of advanced sensors with ultra-low power consumption,and the development of flexible and energy-saving electronic devices.

Core-shell Ni_(3)Sn_(2)@C particles anchore d on 3D N-dope d porous carbon skeleton for modulated electromagnetic wave absorption

Synthesizing multi-component composites via a straightforward,reliable,and scalable approach has been challenging.Herein,a three-dimensional nitrogen-doped porous carbon decorated with core-shell Ni_(3)Sn_(2)@carbon particles(3D N-PC/Ni_(3)Sn_(2)@C)was customized through a simple salt-template pyrolysis approach.The formed Ni_(3)Sn_(2) particles are perfectly surrounded by crystalline carbon layers and em-bedded in 3D carbon walls during pyrolysis.The dual protection of crystalline carbon layers and porous carbon walls guarantees the electrical conductivity and stability of Ni_(3)Sn_(2).The intriguing 3D and core-shell structure coupled with the introduction of multiple components empowers the composite with rich heterogeneous interface and conductive network,and contributes to the lightweight,corrosion resistance,oxidation resistance,and superior stability of electromagnetic(EM)wave absorbers.The N-PC/Ni_(3)Sn_(2)@C possesses the minimum reflection loss(RL min)of-54.01 dB and wide effective absorption bandwidth(EAB)of 7.36 GHz under a low filler content of less than 10%.The concept in the work proposes a facile,eco-friendly,and scalable pathway for the synthesis of other heterogeneous structures of EM wave ab-sorbers.