FRM用先进陶瓷纤维及其拉伸强度

陶瓷,其耐热性、耐腐蚀性、功能性等引起人们重视,作为一种新材料而得到开发,其有用性得到了公认。所谓新材料,或明显提高原料纯度,或使其形状极端微细化、微粉化或者薄膜化,或使原料组合、制成合金,从而使材料性能得到空前的发挥。碳化硅(SiC)、硼(B)、氧化铝(Al₂O₃)等陶瓷也可使其形状变成又细又长的纤维状,从而使拉伸强度提高,使陶瓷的使用变得容易起来。本稿将就最近开发的轻质高强陶瓷纤维的性能加以介绍。      

有限宽度和椭圆孔形状对缺口层合板强度预测的影响

本文采用有限元方法对正交各向异性材料含有不同椭圆孔形状的有限宽度板作了分析,给出了有限宽度和椭圆孔形状对应力集中因子K₁和孔边应力分布σ_y(x,0)的影响公式。数值结果表明:正交各向异性板的有限宽度和椭圆孔形状对K_r和σ_y(x,0)的影响均与各向同性材料不同,所以有限宽度和椭圆孔形状将对缺口层合板强度的预测产生影响。      

复合材料加筋板的动力分析

本文构造了九自由度三角形拟协调罚函数复合材料板单元与六自由度复合材料梁单元,考虑了剪切变形与转动惯量的影响。用这两种单元对复合材料加筋板的自由振动、阻尼特性和瞬态响应问题进行了研究,给出一些有益结果。      

Microstructure and mechanical properties of CoCrNi-Mo medium entropy alloys:Experiments and first-principle calculations

The effect of Mo additions on the microstructures and mechanical properties of CoCrNi alloys was investigated,meanwhile,ab initio calculations are performed to quantitatively evaluate the lattice distortion and stacking fault energy(SFE).The yield strength,ultimate tensile strength,and elongation of(CoCrNi)₉₇Mo₃alloy are 475 MPa,983 MPa and 69%,respectively.The yield strength is increased by~30%and high ductility is maintained,in comparison with CoCrNi alloy.Besides the nano-twins and dislocations,the higher density of stacking faults is induced during the tensile deformation for(CoCrNi)₉₇Mo₃alloy.Ab initio calculation results indicate the mean square atomic displacement(MSAD)and SFE value of(CoCrNi)₉₇Mo₃alloy is 42.6 pm²and-40.4 mJ/m²at 0 K,respectively.The relationship between mechanical properties and MSAD,SFE for various multiple principal element alloys is discussed.     

涂料的前世与今生

<正>2014年3月24日,应国家主席习近平夫人彭丽媛邀请,美国总统奥巴马夫人米歇尔·奥巴马以及米歇尔的母亲和两个女儿抵达西安参观访问。中午1时,米歇尔一行的车队抵达秦陵博物院,在进入一号俑坑的一刹那,米歇尔露出非常惊讶的表情。既惊讶于兵马俑规模的宏大,也好奇于兵马俑彩绘的绚烂。当她来到一件正在清理的陶俑旁边时,陶俑身上的彩绘吸引了米歇尔的目光。米歇尔好奇地询问这些颜色是不是原始的颜色。考古人员告诉她,这是刚刚发现的。米歇尔随后表示,希望能把文物保护     

冷轧薄宽带钢局部型中浪瓢曲变形行为研究

针对薄宽带钢冷轧过程中易发多发的局部型中浪瓢曲缺陷,引入非均匀载荷宽度、弹性约束系数及平均张应力建立了屈曲变形的解析计算模型。应用能量最低原理对屈曲变形区域进行搜索求解,得到了局部型中浪屈曲临界条件(包括临界应力、屈曲波长和屈曲波宽),获得了其与非均匀载荷宽度、弹性约束系数、平均张应力的关系,并发现平均张应力是产生局部型中浪的重要影响因素。应用样条有限元方法对局部型中浪进行数值仿真分析,验证了屈曲解析计算方法的正确性。在实验轧机上进行了轧制研究,通过轧制获得了局部型中浪屈曲模态,对实验结果分析得到了相对应的屈曲临界条件,与解析法和样条有限元法结果基本吻合,证明了样条有限元计算方法与解析计算方法的正确性及其工程应用价值。     

F16-4型放映机激励灯的调整和固定

激励灯的灯头上有一大一小两个卡片,在灯座上对应的有两个槽,把激励灯装上去应当稳定不动.但由于槽的缝隙较宽,或固定灯泡的弹簧片疲劳使弹力减弱,致使灯泡受震动后容易前(指的是靠镜头一面)后幌动,这样会导致激励光刃变宽或不均匀,使还音含糊不清、失真.     

真空技术在射线源注油中的应用

本设备可对注油机的储油箱、拉模箱、溢油箱提供真空环境并对射线源抽真空和注油,注油过程中对各储油室中的绝缘油进行真空脱气、脱水,以确保注油前的性能指标,使油品达到军标、国标、国际标准.使真空技术在射线源注油技术中得到了很好的应用.通过理论计算合理配置真空系统,通过不断的探索和实践在真空系统中加装了氟里昂挡油装置,氟里昂挡油装置的设置从根本上解决了液体绝缘油在进行真空脱气、脱水过程中的一系列难题.     

Tailoring polysulfide trapping and kinetics by engineering hollow carbon bubble nanoreactors for high-energy Li-S pouch cells

Despite great progress of lithium-sulfur(Li-S)battery performance at the laboratory-level,both key parameters and challenges at cell scales to achieve practical high energy density require high-sulfur-loading cathodes and lean electrolytes.Herein,a novel carbon foam integrated by hollow carbon bubble nanoreactors with ultrahigh pore volume of 6.9 cm3·g?1 is meticulously designed for ultrahigh sulfur content up to 96 wt.%.Tailoring polysulfide trapping and ion/electron transport kinetics during the charge-discharge process can be achieved by adjusting the wall thickness of hollow carbon bubbles.And a further in-depth understanding of electrochemical reaction mechanism for the cathode is impelled by the in-situ Raman spectroscopy.As a result,the as-prepared cathode delivers high specific capacitances of 1,269 and 695 mAh·g?1 at 0.1 and 5 C,respectively.Furthermore,Li-S pouch cells with high areal sulfur loading of 6.9 mg·cm?2 yield exceptional practical energy density of 382 Wh·kg?1 under lean electrolyte of 3.5μL·mg?1,which demonstrates the great potential for realistic high-energy Li-S batteries.     

Efficient hexane isomers separation in isoreticular bipyrazolate metal-organic frameworks: The role of pore functionalization

Hydrocarbons separation in petrochemical industries is a key,energy-consuming stage in the manufacture of high-quality added-value products—hence the need for more efficient materials and environmentally friendly methodologies to improve this process.In this context,we have studied the effect of metal-organic frameworks(MOFs)pore functionalization in hexane isomers separation,isolating the robust isoreticular zinc(ll)bipyrazolates Zn(BPZ),showing no pore decoration,Zn(Me₂BPZ),the pores of which are decorated with apolar methyl groups,and Zn(BPZ(NH₂)₂),the spacers of which possess polar Lewis-basic functions(H₂BPZ=1H,1'H-4,4'-bipyrazole;H₂Me₂BPZ=3,3'-dimethyl-1H,1'H-4,4'-bipyrazole;H₂BPZ(NH₂)₂=3,5-diamino-1H,1'H-4,4'-bipyrazole;DMF=dimethylformamide).After characterizing Zn(BPZ(NH₂)₂)as per its crystal structure and thermal behaviour,and all the three MOFs as per their textural properties,we investigated,from the experimental and computational points of view,the impact of the square one-dimensional channels decoration on the separation of the hexane isomers,demonstrating the relevance of pore constrictions in the resolution of the title alkanes mixture.     

Quaternary system Li2MoO4-Na2MoO4-CaMoO4-BaMoO4

The Li₂MoO₄-Na₂MoO₄-CaMoO₄-BaMoO₄ quaternary system was studied by differential thermal analysis and direct visual observation. Three invariant points, two peritectic and one eutectic, were located.     

Superconducting and normal state properties of ErRh4B4 and LuRh4B4

Detailed heat capacity measurements of the ternary compounds ErRh₄B₄ and LuRh₄B₄ have been performed between 0.5 and 36 K and in magnetic fields up to 4 kG, yielding new information on crystal field effects in these materials and on the influence of externally applied magnetic fields on the coupled superconducting-ferromagnetic reentrant transition in ErRh₄B₄. Static magnetic susceptibility data on LuRh₄B₄ are presented which allow qualitative conclusions to be drawn regarding the magnitude of exchange enhancement and orbital paramagnetic effects in the RERh₄B₄ compounds. The electrical resistivity of ErRh₄B₄ has also been determined between 4 K and room temperature.This research was supported by the Department of Energy under Contract Number Ey-76-S-03-0034-PA227-3 (LDW, HBM, RWM, MBM) and by the National Science Foundation under Grant Number NSF/DMR77-08469 (DCJ). One of us (RWM) thanks the National Science Foundation for a postdoctoral fellowship.     

10Cr4Ni4Mo4V钢和Cr4Mo4V钢的特性与断裂行为

对１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢和Ｃｒ４Ｍｏ４Ｖ钢的特性与断裂行为进行了试验研究。结果表明,１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢经微氮渗碳热处理后,其表面硬度、残余应力、断裂韧性及裂纹扩展速率均优于Ｃｒ４Ｍｏ４Ｖ钢的。     

Itinerant electron magnetism in the Mo4 tetrahedral cluster compounds GaMo4S8, GaMo4Se8, and GaMo4Se4Te4

The specific heat and magnetic properties of GaMo₄X₈ (X=S, Se, SeTe) between 1.4 and 290 K are reported. Our measurements tend to demonstrate that these compounds have a very high density of states, leading to a Stoner magnetic instability of conduction electrons at low temperatures. The linear temperature-dependent term in the specific heat is enhanced by electron-phonon coupling and spin fluctuation effects. These compounds could indicate an electron-phonon contribution to the Stoner enhancement factor.     

Dielectric properties of Bi4(GeO4)3 and Bi4(SiO4)3

Dielectric constant, dielectric loss and conductivity of Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ single crystals have been measured as a function of frequency and in the temperature range from liquid nitrogen temperature to 400° C. The values of the static dielectric constant at room temperature are 16·4 and 13·7 for Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ respectively. The plots of log (σ) against reciprocal temperature at different frequencies of these crystals merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0·95 eV and 1·2 eV for Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ respectively.     

球形NH4FePO4·H2O的制备

以柠檬酸铵作络合剂通过控制结晶法制备了的球形NH4FePO4·H2O,用扫描电镜观察了颗粒的形貌和分布.通过研究加料方式、反应温度、滴加速度、搅拌速度、反应物浓度等对颗粒形态的影响,得到了制备球形NH4FePO4·H2O的最佳工艺条件.     

Nano-phases of NaBH4 and KBH4

Phase stability and chemical bonding of beta-NaBH4 and beta-KBH4 derived nano-structures and possible low energy surfaces of them from thin film geometry have been investigated using ab initio projected augmented plane wave method. Structural optimizations based on total energy calculations predicted that, for beta-NaBH4 and beta-KBH4 phases, the (011) and (101) surfaces are more stable among the possible low energy surfaces. The predicted critical size of the nano-cluster for beta-NaBH4 and beta-KBH4 is 1.35 and 1.8 nm, respectively. The corresponding critical diameter for the nano-whisker is 2.6 and 2.8 nm respectively for beta-NaBH4 and beta-KBH4. Structural optimization based on total energy calculations show that the bond distances in the surfaces of nano-whisker are found to be higher than that in the bulk material and the calculated H site energies and bond overlap population analysis suggesting that it is considerably easier to remove hydrogen from the surface of the clusters and nano-whiskers than that from the bulk crystals.     

Low-temperature magnetic properties of HoRh4B4

The low-temperature magnetic properties of HoRh₄B₄ have been studied by means of measurements of the magnetic susceptibility, magnetization, specific heat, thermal expansion, and magnetostriction. The ferromagnetic phase transition at T _M= 6.7 K shows almost ideal S = 1/2 mean field behavior in the specific heat. Crystal field effects due to the splitting of the J = 8 Hund's rule ground state of the Ho³⁺ ions result in Schottky anomalies in the specific heat and the thermal expansion and are also revealed in the low-field magnetic susceptibility and the magnetostriction. Information on the ground state doublet of the 4f electrons has been obtained from the nuclear contribution to the specific heat below 1 K and the high-field magnetization below T_M.This research was supported by the Schweizerische Nationalfonds zur Forderung der wissenschaftlichen Forschung (HRO), by the Department of Energy under Contract No. EY-76-S-03-0034-PA227-3 (LDW, MBM), and by the National Science Foundation under Grant No. NSF/DMR77-08469 (DCJ)     

Low-temperature magnetic behavior of HoRh4B4

Detailed measurements of the magnetization of HoRh₄B₄ and GdRh₄B₄ near the magnetic transition temperature are presented. In contrast to the ferromagnetic behavior of GdRh₄B₄, no spontaneous magnetization is found to develop below T _min HoRh₄B₄. This raises doubts about the nature of the magnetic order in that material as well as in DyRh₄B₄ and TbRh₄B₄. Anisotropy and time dependence of the magnetization are found in these last three compounds. The behavior of the very small remanent magnetization and of the paramagnetic susceptibility of HoRh₄B₄ is shown. These results point to a complex magnetic order, possibly helical or sinusoidal antiferromagnetism with a long wavelength.Partially supported by a grant from the Swiss National Science Foundation.Research in La Jolla supported by National Science Foundation Grant No. DMR77-08467.