Nanoscale thermal transport in epoxy matrix composite materials reinforced with carbon nanotubes and graphene nanoplatelets

Journal of Nanoparticle Research - We have applied ab initio electronic structure method to search minimum energetic structures of the supported and free bimetallic PdCo nanosized particles by...     

Nuclear orientation study of the quadrupole interaction for Co in PdCo alloy

The angular distribution anisotropy of -radiation was measured following the decays of⁵⁸Co and⁶⁰Co oriented at low temperatures in the ferromagnetic PdCo alloy. The ratio of the electric quadrupole to magnetic dipole interaction constants for the⁶⁰Co was deduced to be P/a_o=0.001±0.003, where P=3e²qQ/4I(2I-1) and a_o=H/I.     

100Rh pac study of the critical region of Co: The lessons learned

Observations of hyperfine fields over 295<T<1330 K and relaxation spectra above T_c demonstrate the feasibility of measuring static and dynamic critical exponents with sources of¹⁰⁰PdCo. These PAC experiments promise to clarify current discrepancies between measured exponents and theory in Co once source contamination problems are resolved.     

Determination of the local structure of a highly dispersed Pd-Nanosystem located on a titanium dioxide carrier

This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO₂ matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(μ-OOCMe)₄(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.     

Temperature distribution and its influence on microstructure of Mg–3Sn–1Mn alloy during rheo-rolling process

In this paper, an innovative semisolid rheo-rolling process of Mg–3Sn–1Mn alloy was proposed; the temperature distribution and its influence on microstructure of Mg–3Sn–1Mn alloy during the semisolid rheo-rolling process were studied. The alloy temperature decreased gradually from the entrance to the exit of the slope plate, and the alloy velocity increased gradually. The temperature of the alloy near the slope plate surface was lower than that of melt surface. The alloy temperature decreased gradually from the entrance to the exit of the roll gap. In the roll gap, the nearer the roll was, the lower the alloy temperature was. With the increment of casting temperature, the semisolid zone increased and moved forward from the filling mouth to the exit of the roll gap. When the casting temperature was 670°C and the roll speed was 0.052?m/s, Mg–3Sn–1Mn alloy strip with good surface quality was obtained. Homogeneous microstructure was obtained. Mechanical properties of the present product at room temperature or 150°C are higher than that of Mg–3Sn–1Mn–0.87Ce prepared by casting.     

Size and composition dependence of melting temperature of binary nanoparticles

Based on the ideal solution approximation, the model for size-dependent melting temperature of pure metal nanoparticles is extended to binary alloy systems. The developed model, free of any adjustable parameter, demonstrates that the melting temperature is related to the size and composition of alloy nanoparticles. The melting temperature of CuNi, PbBi and SnIn binary alloy nanocrystals is found to be consistent with the experiments and molecular dynamics simulations. The research reveals that alloy nanocry...     

CC5083与CC5182铝合金冷轧与再结晶后偏光金相观察组织和X射线检测织构对比研究

连续冷却铸造5083铝合金板较大塑性变形量冷轧后的组织、织构及性能与再结晶处理工艺关系的研究有限。对冷轧压下量约为91.5%的CC5083与CC5182铝合金板分别进行室温入箱式电炉、随炉不限速升温到不同温度退火2 h和分别进行直接入不同温度盐炉退火30 min、出炉水冷至室温后,采用偏光金相显微镜观察组织、采用X射线衍射检测织构,进一步对比研究较大压下量冷轧后退火工艺与再结晶组织和织构关系。结果显示：(1)电炉退火CC5083铝合金板的再结晶开始及晶粒长大温度为343 ℃,晶粒长大后形状为长条状(创新点);盐炉退火CC5083铝合金板的再结晶开始温度为343 ℃;二者再结晶完成温度都为371 ℃。(2)CC5182铝合金板分别在电炉与盐炉454 ℃以上退火,晶粒开始显著长大;电炉退火与盐炉退火CC5083铝合金板再结晶开始温度分别高于电炉与盐炉退火的CC5182铝合金板,盐炉退火CC5083铝合金板再结晶晶粒长大温度高于另外三种方式退火;CC5182铝合金板盐炉退火再结晶晶粒长大温度高于电炉退火的。CC5083和CC5182铝合金冷轧板表层再结晶及再结晶晶粒长大温度明显高于内层的(创新点)。(3)四种方式退火再结晶晶粒长大温度及相同温度退火时织构转变程度有差异(创新点);退火过程中织构检测结果与金相组织观察结果反映的再结晶进程不很一致。     

Temperature dependence of luminescence from ZnS0.11Se0.89 random and ordered alloys

Temperature dependence of the luminescence spectra was investigated for a ZnS_0.11Se_0.89 random alloy and a (ZnSe)₁/(ZnS_0.22Se_0.78)₁ ordered alloy with equivalent mean sulfur compositions. The luminescence peak for the random alloy as a function of temperature shows anomalous behavior, while that for the ordered alloy exhibits normal behavior. From the temperature dependence of luminescence intensity for the random alloy, the quenching process can be understood with additional thermal activation energy besides exciton dissociation energy. Through the analysis of the temperature variation of the luminescence line width, the exciton-optical phonon coupling constant is found to be reduced in the random alloy. The results of this study demonstrate that exciton is localized by the potential fluctuation in the random alloy and that the potential fluctuation is significantly constrained in the ordered alloy.     

白铜热氧化过程中光谱发射率特性研究

随着科技的发展,工业领域对白铜产品质量的要求日益提升;利用辐射测温技术对白铜在冶炼和加工时的温度进行精确测量,是决定产品质量的重要手段,因此研究白铜的光谱发射率特性就显得尤为重要。基于傅里叶红外光谱仪搭建的光谱发射率测量装置,测量了白铜在四个温度点（673,773,873和973 K）,波长范围2～22 μm内的光谱发射率,分别研究了波长、温度、加热时间和氧化对白铜光谱发射率的影响。研究发现,在氮气环境下白铜的光谱发射率随温度的升高而增加,随波长的增加而减少。当白铜暴露在空气环境中,随着温度的升高,其光谱发射率迅速增加。673 K时,白铜表面生成一层细微的氧化物颗粒,阻止白铜进一步氧化,这些氧化物颗粒的光谱发射率大于白铜基底,所以此温度下短波处的光谱发射率略微增加。773 K时,白铜表面氧化物的主要成分是Cu₂O,在实验过程中也观察到白铜表面逐渐变红的现象,这也是白铜在773 K温度下其光谱发射率迅速增加的原因。873 K时,白铜表面氧化物的种类和含量明显增多,氧化膜的厚度满足干涉效应条件,在白铜的光谱发射率曲线中可以明显地观察到干涉极值的演变,随着加热时间的增加,干涉极值逐渐向长波移动。随着温度的升高,白铜的抗氧化能力下降。973 K时,白铜表面的氧化程度最深,在XRD图中氧化物的峰值也最大,因此氧化1 h后由于干涉效应产生的干涉极值数最多。综上所述,波长、温度和氧化对白铜的光谱发射率有重要的影响,在运用辐射测温技术测量白铜温度时应充分考虑上述因素的影响。该研究丰富了白铜的光谱发射率数据,为辐射测温提供了真实可靠的数据支撑。     

铝-0.1%镁合金中表现反常振幅效应的低频位错内耗峰

用低频扭摆测量了经过轻度冷加工的Al-0.l％Mg合金在室温时效过程中的内耗变化,观察到表现反常振幅效应的时效内耗峯。用经过充分时效而内耗已达到稳定值的试样进行升温和降温内耗测量,也在30—55℃的温度范围内观察到表现反常振幅效应的温度内耗峯。这些现象在高纯铝试样和经过完全退火的Al-0.l％Mg合金试样中都不出现。在Al-0.l％Mg合金中也能观察到以前在Al-0.5％Cu合金中所观察到的反常内耗现象,这就排斥了任何用在点阵中所发生的一般脱溶沉淀过程来解释这种反常内耗现象的可能性,困为在含0.1％Mg的铝合金中,在实验测量所涉及的温度范围内,是不能够在点阵中发生一般的脱溶沉淀过程的。为了解释铝镁合金中所呈现的反常内耗现象的特点,可以假设在铝镁合金中能够形成两种位错气团:一种是“镁原子-空位”对与位错所组成的气团,这种气团能够在应变时效过程中形成;另一种气团是镁原子与位错所组成的气团,当经过范性形变的试样的温度升高到100℃左右时,镁原子与空位脱离,在退火过程中就单独与位错形成气团。前一种气团对于位错的钉札较第二种为强,因而它的振幅内耗峯出现在较高的振幅值。     

基于铅铟合金线的SFQ多芯片超导互连方法研究

用基于铅铟合金线的引线键合(WB)工艺对单磁通量子(SFQ)多芯片的超导互连方法进行了研究,将铅含量75%,铟含量25%的铅铟合金线制备成WB线材,用超声楔形焊工艺成功实现SFQ芯片I/O接口焊盘的超导互连.拉力测试表明室温下铅铟合金线键合强度与同线径金线相当,优于同线径铝线;用开尔文四端法测量了铅铟合金线互连的多级超导转变温度以及线材与超导芯片之间的接触电阻,结果表明该铅铟合金线的超导转变温度为6.63 K,当温度降低至6.63 K或更低时,铅铟合金线的线阻以及线材与SFQ芯片I/O接口焊盘的接触电阻为0,实现了超导互连;并通过热冲击实验验证该WB结构具有优异的热稳定性.     

Thermal stability of microstructures and mechanical properties in a Fe-based Fe-Cr-Mn-Cu-Mo multi-component alloy

A Fe-based multi-component alloy, 60Fe-12Cr-10Mn-15Cu-3Mo, was designed and fabricated for nuclear applications in the present study. The crystal structure of the alloy is a ～85% body – and 15% face–centered cubic. A detailed microstructure analysis indicated that Cu segregated in the alloy to form Cu-rich precipitates, and the Cu precipitates grew during high temperature annealing at up to 773?K. The high temperature tensile test of the alloys showed that both the yield stress and tensile strength of the 60Fe-12Cr-10Mn-15Cu-3Mo were greater than those of typical austenitic and ferritic stainless steels at 773?K. The Vickers microhardness of the designed alloy did not change after high temperature annealing for 1?h at up to 1073?K. The results indicated that the designed alloy has the potential to be used for high temperature applications.     

Ca、Sr对汽车用镁合金组织与力学性能的影响

以Mg-Al-Mn合金为研究对象,通过微合金化的方法研究了Ca、Sr对汽车用耐热镁合金常温力学性能与高温力学性能的影响,并分析了合金在固溶时效热处理后的时效硬化特征,观察了合金铸态、固溶态和时效态下的显微组织演变。     

Mn-Cu系高阻尼合金的凝固组织控制及阻尼特性的改善

Mn—Cu系阻尼合金兼有较高的阻尼特性和良好的力学性质，因而具有较大的实用前景。这类合金通常经过铸造，塑性加工和热处理来获得要求的性能和组织。加工后的Mn—Cu合金存在一个特定温度，在此温度以上合金的阻尼性能将会消失，因而影响了合金的在较高温度下的使用。该温度和合金的Mn含量有关，然而提高合金的Mn含量有会降低合金的加工性及力学性能。一般Mn-Cu合金的热处理都是利用400℃附近的时效来获得相分解后的局部高Mn组织。但是目前的时效处理后的Mn—Cu阻尼合金的最高使用温度只在80℃以下。为解决Mn—Cu阻尼合金使用温度的局限性，本研究选用凝固过程控制的方法在铸造组织中来获得较大幅度的Mn含量分布。从而在Mn-Cu合金得到较高的高阻尼特性温度。本工作利用铸型温度控制的方法，将M2052（Mn-20Cu-5Ni-2Fe）合金在250～0．1K／s冷却速度范围内控制凝固。随凝固冷却速度的降低在合金的铸态组织中观察到二次枝晶间距和晶粒尺寸的明显增大。同时还发现缓冷凝固的合金的成分比快冷凝固有较大的分布幅度。铸态下的合金阻尼性能评价也证实了凝固冷却速度对合金的凝固组织有很大的影响。尽管铸态组织的合金的高温阻尼性能并没有很大的改善，然而通过对铸态组织实施时效处理后发现缓冷凝固合金的高温阻尼性能有很大的改善。凝固冷却速度对时效处理后合金的阻尼性能有明显的影响。实验结果表明0．1K／s的冷却速度下缓慢凝固的合金在时效处理后高阻尼特性可持续高达120℃．     

Thermal stability and high-temperature shape memory characteristics of Ti–20Zr–10Ta alloy

The microstructure, martensite transformation behavior, thermal stability and shape memory behavior of Ti–20Zr– 10Ta high temperature shape memory alloy were investigated. The Ti–20Zr–10Ta alloy exhibited a reversible transformation with the high martensite transformation temperature of 500oC and good thermal stability. The alloy displayed the elongation of 15% and a maximum recovery stain of 5.5% with 8% pre-strain.     

液体钾、钠及其合金NaK的密度

我们用膨胀计方法,在温度0—300℃的范围内,测定了液体金属钠、钾以及它们的合金NaK三种样品的密度。所用金属的纯度约在三个九以上,结果表明,所测液体金属及其合金的密度可作为温度的线性函数来表示,但NaK合金的(d,t)直线在接近冰点地方偏离直线上翘。     

1 053 nm脉冲激光对铝合金/水结构辐照效应

使用1 053 nm脉冲激光分别辐照铝合金单板和铝合金/水结构,通过表面形貌观察、温度场分析、熔穿时间测量等手段,分析了水的存在对铝合金壳体烧蚀的影响。运用有限元软件ANSYS,建立了脉冲激光辐照下单板及结构温度变化的数值模型,计算了铝合金表面熔凝区域的尺寸,并与实验结果进行了对比。结果表明：在相同的实验条件下,辐照8个激光脉冲时,铝合金单板即被熔穿,而辐照10个脉冲后铝合金/水结构仍未发生熔穿,且结构中铝合金表面的熔凝区域要小于单板情形中的熔凝区域,这表明水的存在对延缓铝合金板的烧蚀有较大的作用。对于单板情形,计算结果与实验结果符合较好,而对于铝合金/水结构情形,数值模拟放大了铝合金壳体的温升,这主要是因为数值模拟程序未考虑水的对流及沸腾换热对计算结果的影响。     

激光辐照超音速气流下TA15钛合金和LY12铝合金的热响应

利用超音速气流环境模拟装置,开展了自然对流和马赫数为3切向气流下,1064nm连续激光辐照TA15钛合金和LY12铝合金热响应实验研究,得到了材料在两种条件下的温升曲线及熔穿时间。结果表明:在激光辐照材料未使得其表面发生熔化前,气流对材料激光辐照过程中的冷却效应较为明显,在表面发生熔化时,熔化的液态物质在气流切向力剥蚀作用下被吹离材料表面,使得激光继续作用在材料上,熔化→剥离→熔化→剥离如此反复,可加速熔穿过程;此外,切向气流将影响钛合金这类热扩散系数较低材料的温度场分布,使得气流下游处的温度高于上游,而对铝合金这类热扩散系数较高的材料而言,影响不明显。     

激光辐照超音速气流下TA15钛合金和LY12铝合金的热响应

利用超音速气流环境模拟装置,开展了自然对流和马赫数为3切向气流下, 1064 nm连续激光辐照TA15钛合金和LY12铝合金热响应实验研究,得到了材料在两种条件下的温升曲线及熔穿时间。结果表明：在激光辐照材料未使得其表面发生熔化前,气流对材料激光辐照过程中的冷却效应较为明显,在表面发生熔化时,熔化的液态物质在气流切向力剥蚀作用下被吹离材料表面,使得激光继续作用在材料上,熔化剥离熔化剥离如此反复,可加速熔穿过程;此外,切向气流将影响钛合金这类热扩散系数较低材料的温度场分布,使得气流下游处的温度高于上游,而对铝合金这类热扩散系数较高的材料而言,影响不明显。     

LF-6及LY-12铝高温凝聚态动力学性质研究──高温剪切模量的测量

 介绍LF-6及LY-12铝合金从常温到400 ℃高温下，在扭转Hopkinson杆上作的动态剪切模量的测试研究，并给出了相应温度范围LF-6铝杨氏模量及泊松比。它们和现有文献中的静态结果比较表明，动态性能普遍高于静态值，在高温下更显著。实验结果表明LF-6和LY-12铝合金，对于温度和加载率都是敏感的，高加载率下相对于静态的温度，敏感性要弱一些。文中给出了剪切模量、弹性模量等与温度的关系式。