Non-Isothermal Crystallization Kinetics of a Rapidly Solidified as-Cast TiZrHfNiCu High Entropy Bulk Metallic Glass

This paper aims to investigate the thermal behavior and crystallization kinetics of TiZrHfNiCu high entropy bulk metallic glass (HE-BMG) alloy using the standard procedure of Differential Scanning Calorimetric (DSC) annealing technique. The alloy was produced using an arc melting machine with a critical diameter of 1.5 mm. The crystallization kinetics and phase transformation mechanism of TiZrHfNiCu HE-BMG was investigated under the isochronal condition at a single heating run based on the Johnson-Mehl- Avrami (JMA) theory. In isochronal heating, the apparent activation energy for glass transition and crystallization events was analyzed by Kissinger and Ozawa methods. The average activation energy value for crystallization of TiZrHfNiCu amorphous alloys in isochronal modes was 226.41 kJ/mol for the first crystallization and 297.72 kJ/mol for second crystallization stages. The crystallization mechanism of the first step was dominated by two- and three-dimensional growth with increasing nucleation rate, while the crystallization mechanism in the second stage was dominated by two-dimensional crystallization growth with a constant nucleation rate. The diffusion mechanism result proved the theory of sluggish atomic diffusion of HEA at elevated temperature.

Investigation on Rapidly Solidified T15 High Speed Steel Powder and Its Bulk Microcrystalline Material

Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prepared bulk microcrystalline T15 high speed steel materials by hot extruding or HIPing and hot rolling of the powders,observed and measured the microstructure and performance of the bulk materials.It was shown that rapid solidification may change the solidification characteristics and structure of T15 high speed steel powder and improve the qualities and properties of T15 high speed steel materials.

Isothermal bulk modulus and its first pressure derivative of NaCl at high pressure and high temperature

The isothermal bulk modulus and its first pressure derivative of NaCl are investigated using the classical molecular dynamics method and the quasi-harmonic Debye model. To ensure faithful molecular dynamics simulations, two types of potentials, the shell-model （SM） potential and the two-body rigid-ion Born-Mayer-Huggins-FumiqTosi （BMHFT） potential, are fully tested. Compared with the SM potential based simulation, the molecular dynamics simulation with the BMHFT potential is very successful in reproducing accurately the measured bulk modulus of NaCl. Particular attention is paid to the prediction of the isothermal bulk modulus and its first pressure derivative using the reliable potential and to the comparison of the SM and the BMHFT potentials based molecular dynamics simulations with the quasi-harmonic Debye model. The properties of NaCl in the pressure range of 0-30 GPa at temperatures up to the melting temperature of 1050 K are investigated.

Production of carbon anodes by high-temperature mould pressing

Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.

High strain rate induced embrittlement of Zr-based bulk metallic glass

Quasi-static and high strain rate mechanical behavior of the Zr_ 1.25Ti_ 13.75Ni_ 10Cu_ 12.5Be_ 22.5 bulk metallic glass was determined covering strain rates from 1.02×10 -4s -1 to 3.258×103s -1. By use of split hopkinson pressure bar(SHPB) equipment, it is found that the alloy fractures in the high strain rate period with a strength well below that of its quasi-static counterpart and thus a strain rate induced embrittlement happens. Considering the glassy nature of the alloy and with careful analysis of the fracture morphology, dynamic damage accumulated in the high speed deformation period is suggested to be the reason for this embrittlement.

Comparative Study on Super Fine Mesophase Powder and MCMB Used to Manufacture High-Density Isotropic Carbon Bulks

Mesocarbon microbeads （MCMB） and super fine mesophase powder （SFMP） were prepared firstly from a coal tar pitch and then hot-condensed into high-density isotropic carbon （HDIC） bulks under 160 MPa and finally sintered at 1 000 ℃. By analyzing the thermogravimetric behavior of the MCMB and SFMP powders, their volume shrinkage and weight loss during sintering and the bulk density and flexural strengths of their sintered bulks, it was found that the smaller sizes and the richer β-resin contents of SFMP ha）re facilitated formation of sintered bulks with more compact isotropic structure and higher flexural strengths than MCMB. Because of the filling and bonding effects of SFMP on MCMB bulks, addition of SFMP, albeit a little, can greatly increase the flexural strengths of sintered bulks of MCMB. However, adding MCMB, even a slight amount, into SFMP can severely impair the flexural strength of sintered bulks. This might be attributed to both the crack initiation along the boundaries between MCMB and SFMP and the formation of layered texture of MCMB sphere.

Comparative study of bulk metallic glass composites with high-volume-fractioned dendritic and spherical b. c. c. phase precipitates

A dendritic β-phase reinforced bulk metallic glass(BMG) composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical β-phase reinforced composite named as composite S2. It was found that the composite D2 contains β-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volumefractioned β-phase dendrites transferred to coarse spherical particles of about 20 μm in diameter in the composite S2, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical β phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.

RNA-Seq and Bulked Segregant Analysis of Genes Related to High Growth in <i>Ginkgo biloba</i>Half-Sibling Families

The lifetime of G. biloba is very long, and its growth is relatively slow. However, little is known about growth-related genes in this species. We combined mRNA sequencing (RNA-Seq) with bulked segregant analysis (BSA) to fine map significant agronomic trait genes by developing polymorphism molecular markers at the transcriptome level. In this study, transcriptome sequencing of high growth (GD) and low growth (BD) samples of G. biloba half-sib families was performed. After assembling the clean reads, 601 differential expression genes were detected and 513 of them were assigned functional annotations. Single nucleotide polymorphism (SNP) analysis identified SNPs associated with 119 genes in the GD and BD groups;58 of these genes were annotated. Two Homeobox-leucine zipper protein genes were up-regulated in the GD group compared with the BD group;therefore, these are very likely related to high growth of G. biloba. This study provides molecular level data that could be used for seed selection of high growth G. biloba half-sib families for future breeding programs.

纳米钨在高压下的物理力学行为与尺寸效应研究

探究尺寸效应对材料高压物性的影响规律有助于开发具有新颖或者改良特性的新材料。采用金刚石对顶砧结合同步辐射X射线衍射技术,研究了平均晶粒尺寸分别为30和65 nm的多晶钨粉在高压下的静态压缩行为。通过分析每个压力点下X射线衍射图谱的峰位和半高宽等,得到了纳米金属钨在高压下的晶胞体积、晶粒尺寸和微观应变等。通过拟合三阶Birch-Murnaghan方程,得到了30和65 nm钨的体弹模量,分别为257(7)GPa和343(8)GPa。结合前人的研究结果发现,当晶粒尺寸从微米降低至10 nm,钨的屈服强度逐渐增大,10 nm钨的屈服强度较微米晶样品的屈服强度提高了3.5倍;体弹模量呈现先增大后减小的趋势,30 nm钨的体弹模量较65 nm钨减小了25%。

基于BIM的航站楼钢网架屋盖高空散装法施工模拟与力学仿真分析

以南充高坪机场改扩建施工为背景进行技术应用,结果表明:在场地不足的情况下,高空散装法是较优的安装方案;基于BIM的施工模拟,能够合理规划场地模型、提高施工效率;对施工全过程进行数值模拟力学分析,得出关键杆件与关键施工步,确保施工过程安全进行。

储煤棚螺栓球网架安装技术

储煤棚螺栓球网架结构是一种由钢管杆件和螺栓球组成的空间结构,具有构造简单、受力明确的特点,杆件受力小、用钢量小、整体刚度大、抗震性能好等优点,受力杆件通过节点按一定规律布置的杆件连接起来。螺栓球网架具有结构简单、施工快速、成本低廉等优点,在储煤棚、体育馆、展览馆等领域得到了广泛应用,以某工程为例,从施工工艺、挠度测量、进度控制、安全防护等方面对螺栓球网架技术进行研究。

卫生用纸漂白针阔混合浆高浓磨浆工艺研究

通过生产线高浓磨浆、生产线高浓磨浆+实验室低浓打浆、生产线低浓磨浆、实验室低浓打浆4种工艺,分别获得混合高浓浆、混合高浓+低浓浆、混合低浓浆和实验室浆,研究了不同打浆工艺对漂白针叶木浆和漂白阔叶木浆混合浆(质量比30∶70)纤维性能及卫生用纸手抄片物理性能的影响。结果表明,与混合低浓浆相比,混合高浓浆的细小纤维含量少,纤维扭结较明显,制备的手抄片松厚度、柔软度及吸水性较好;混合高浓+低浓浆纤维扭结指数更大,细小纤维含量更低;其中,生产线高浓浆的浆浓为18%时,混合高浓+低浓浆手抄片的抗张指数、松厚度、柔软度及吸水性均优于混合低浓浆手抄片;混合高浓+低浓浆手抄片(长纤配比30%,打浆度23°SR)与实验室浆手抄片(长纤配比35%,打浆度23°SR)的抗张指数和吸水性相近,松厚度高5.7%、柔软度低27.6%。

高通量高效制备技术在无机玻璃材料中的应用进展

作为材料基因组三大要素之一,材料高通量技术旨在通过高通量制备和高通量表征,将传统材料研究中顺序迭代方法改为并行或高效串行实验,加快材料高效筛选和优化。功能无机玻璃材料是一类典型非晶态材料,因具有特殊优异性能在高技术领域备受关注。无机玻璃材料的成分往往由多个组元构成,传统无机玻璃材料性能优化实验一般采用“一炉一埚”的制备模式,而该模式存在着实验周期长和效率低的问题。因此,将高通量制备的方法和理念引入玻璃新材料的研发和优化具有重要的理论和实际意义。本文总结了现有技术中适用于无机玻璃材料的高通量高效制备技术,并分析了各技术在无机玻璃材料上应用的可行性和改进方向,从而为今后无机玻璃材料高通量制备提供参考。

大跨度网架施工过程中内力重分布问题分析

随着国民审美观念的不断提高,具有外观美的大跨度空间钢结构建筑受到越来越多人的青睐,但在目前施工技术体系下事故频发。原因多是设计网架时,通常按照竣工后整体结构计算内力,选择杆件截面。但实际施工过程中,支座条件与设计计算的差异很大,导致杆件内力与设计状态不同,部分杆件出现整体失稳等现象。该文以兴文县职业技术学校迁建工程8#体育馆为例,分析了大跨度网架施工过程中的内力重分布问题,提出了解决方案,希望为今后的施工提供参考。

装备发射端口匹配条件下屏蔽多芯线耦合连续波强场电磁辐射效应等效测试方法

针对当前对大型武器装备进行屏蔽多芯线缆耦合通道强场连续波电磁辐射效应测试难度巨大的问题,建立了屏蔽多芯线耦合通道大电流注入等效替代强场电磁辐射的理论模型,计算出了辐射和注入条件下的受试设备中各线对终端的差模响应。以两种条件下每一组线对终端的差模响应相等作为等效依据,发现在发射端口阻抗匹配的条件下,各线对的注入激励源与辐照场强的等效对应关系是线性的、相等的,且与受试端内各线对连接的终端阻抗无关。提出了装备发射端口匹配条件下屏蔽多芯线耦合连续波强场电磁辐射效应等效测试方法,并进行了试验验证。试验结果表明:当其中一组线对等效时,其余各线对也已经实现了等效。即使受试端的阻抗发生了非线性变化,各线对的最大误差小于3 dB,验证了测试方法的有效性。

基于优化布拉格结构的固态装配型谐振器

体声波谐振器的有效耦合系数和品质因数决定了体声波滤波器的整体性能。有效耦合系数依赖于叠层结构和压电材料。而品质因数高度依赖于损耗机制,主要为电学损耗和声学损耗。对于固态装配型谐振器(SMR),声学损耗主要为透过衬底的能量泄漏。为提高SMR的品质因数,改进了布拉格堆叠结构,使纵波和剪切波同时被约束在压电堆叠结构中,以减少声能对衬底的泄漏。同时,为抑制谐振腔的杂散模式,优化了布拉格结构顶层薄膜厚度,器件色散特性由Ⅱ型变为Ⅰ型。通过仿真和实验表明:基于优化布拉格结构的SMR性能得到了明显改善。

难选高硫低品位硫化铅锌矿分选工艺研究与探讨

某难选高硫低品位硫化铅锌矿石,主要有价元素Pb、Zn、Fe和S含量分别为2.45%、2.76%、26.76%和30.63%,主要赋存矿物分别是方铅矿、铁闪锌矿和黄铁矿,含量分别为2.97%、4.76%和54.65%;矿石中方铅矿和铁闪锌矿含量较低,而黄铁矿含量超过55%,有用矿物含量差异极大;有用矿物间关系密切,存在相互共生和相互包裹,属于难选硫化铅锌矿石。为确定合理工艺流程,进行了全优先浮选、铅硫部分混合浮选及等可浮选等方案的对比试验研究。结果表明,全优先浮选得到的铅精矿Pb品位和锌精矿Zn品位均很低,通过该流程很难得到合格的铅精矿和锌精矿,主要原因为大量黄铁矿难以有效抑制,同时添加大量石灰调整pH对矿浆环境产生不利影响;铅硫部分混合浮选得到的铅精矿Pb品位偏低,但Zn回收率偏低,造成该问题主要原因为部分铁闪锌矿与黄铁矿存在连生未解离,同时大量铅硫混合精矿经再磨后黄铁矿难抑制;而等可浮选即铅硫等可浮+铅硫分离-锌硫等可浮+锌硫分离工艺流程可得到铅精矿Pb品位60.41%、Pb回收率82.38%,锌精矿Zn品位48.75%、Zn回收率81.59%的良好指标,该流程对大量黄铁矿进行了分段分选,为铅硫分离和锌硫分离提供便利条件。因此,针对该高硫低品位硫化铅锌矿石,等可浮流程稳定可靠且对矿石适应性强,可为选厂设计确定最终流程提供研究方向,并为同类型矿石开发利用提供理论借鉴。

Amorphous phase formation rules in high-entropy alloys

There have been many interesting studies on high-entropy alloys（HEAs）, also known as multi-component（MC） alloys（MCAs）, in recent years. MC metallic-glasses（MGs） have shown the potential to express the advantages of MCAs and MGs in tandem. Amorphous phase formation rules are a crucial issue in the HEA and MCA field. For equal or near-equal atomic ratio alloys, mixed-entropy among the elements has a significant effect on the phase formation. This paper focuses on HEA amorphous phase formation rules. In the first two sections, the recent progress in amorphous phase formation in HEAs and MCAs is reviewed, including the effective factors and correlative parameters related to amorphous phase formation. In the third section, novel MCMGs including high-entropy（HE） bulk-metallic-glass（HE-BMG） and MCMG films developed in recent decades are summarized, and the giant-magnetic-impedance（GMI） effect of MC amorphous fibers is discussed.

高Q值横向激发体声波谐振器的设计与制备

随着5G移动通信时代的发展,射频前端(RF front-ends)的滤波和信号处理迫切需要高频大带宽的声学谐振器。横向激发体声波谐振器(XBAR)具有超高的工作频率和超大的机电耦合系数(k^(2)),但其品质因数(Q)值不高,阻碍了其在射频前端中的应用。该文提出了一种基于ZY切铌酸锂(LiNbO 3)的XBAR谐振器,通过有限元(FEM)仿真对谐振器进行了优化设计,并在微机电系统(MEMS)工艺下对谐振器进行加工。该文所制备的横向激发体声波谐振器A 1模式的谐振频率为4.72 GHz,k 2=26.9%,Q_(3) dB为384,温度频率漂移系数为-60.5×10^(-6)/℃。A_(3)模式的谐振频率为13.5 GHz,k^(2)=4.4%。

本体法聚氯乙烯预聚合釜防粘釜技术改进

介绍了本体法聚氯乙烯生产工艺,分析了预聚合釜粘釜的主要原因并提出了相应的改进措施,包括增加预聚合釜自动高压清洗装置和防粘釜剂自动喷涂装置。改进后延长了预聚合釜的清釜周期,提高了装置产能,降低清釜作业带来的安全风险。