纳米铜粒子的热稳定性研究

利用惰性气体蒸发法制备了平均粒径为40～50nm的纳米铜粒子。采用示差扫描量热法(DSC)对纳米铜粒子的热性能进行了研究。纳米铜粒子在477℃开始熔化，但不同的升温速度有着不同的熔化过程。升温速率低于30℃／min时，纳米铜粒子有足够的时间长大因而观察不到明显的熔点降低。升温速率在30℃／min时，纳米铜粒子快速吸热熔化，在490℃出现明显的熔点，且绝大部分纳米粒子在此温度下熔化。     

[BMIm]BF4离子液体修饰的铜纳米粒子的制备

在[BMIm]BF4离子液体的修饰下,用抗坏血酸还原CuCl2 溶液制备出了铜纳米粒子。Cu2+浓度对铜纳米粒子的尺寸有着非常明显的影响。当Cu2+浓度小于2×10-2mol/L时,所制备的铜纳米粒子的直径小于10nm。还原反应的pH值和温度对铜纳米离子的尺寸没有明显影响。     

丙三醇-水二元溶剂法抗氧化纳米铜的制备

目的基于纳米铜在空气中易被氧化的缺点,制备单分散纳米铜颗粒,并研究改性对其抗氧化性能的影响。方法通过丙三醇-水二元溶剂热法用抗坏血酸还原Cu~(2+)制备纳米铜颗粒。研究丙三醇/水体积比、抗坏血酸用量、聚乙烯吡咯烷酮(PVP)浓度对纳米铜粒径及分散性的影响,并采用柠檬酸和油酸对其进行表面改性处理。结果研究发现,当丙三醇和水的体积比为3∶2,抗坏血酸浓度为0.004mol/L,PVP浓度为0.006 mol/L时,能够得到粒径均一((80±10) nm)且分散性良好的纳米铜。真空环境下保存的纳米铜只有纯铜晶相,但在空气中保存30d后部分被氧化为氧化铜或氧化亚铜。采用柠檬酸改性纳米铜在室温到243℃范围内能保持良好的热稳定性。结论采用丙三醇-水二元溶剂热法制备出了粒径均一、分散性良好的纳米铜。柠檬酸与油酸改性能够显著提高纳米铜的抗氧化与热稳定性能,其改性后在空气中保存30 d仍不被氧化。     

纳米铜粉的制备及其分散性研究

采用液相还原法制备纳米铜粉和纳米铜胶体,选用十六烷基三甲基溴化铵(CTAB)或聚乙烯吡咯烷酮(PVP)为分散剂,通过X射线衍射仪、扫描电镜对纳米铜粉进行表征,通过重力沉降法测试纳米铜胶体的稳定性。结果表明:液相还原法能够制备纯度较高的纳米铜粉;CTAB浓度为0.12 mol/L时,铜粉平均粒径最小,为20 nm,CTAB浓度为0.14 mol/L且超声粉碎20 min时,纳米铜胶体最稳定;PVP浓度为6×10^-4 mol/L时,铜粉平均粒径最小,为20 nm,PVP浓度为7×10^-4 mol/L且超声粉碎20 min时,纳米铜胶体最稳定。     

纳米壳聚糖−ACQ复合处理木材中铜的抗流失性研究

目的 季铵铜（ACQ）防腐剂中的铜离子易流失,会对环境和人类健康造成威胁,通过生物改性技术来改善ACQ的抗流失性及综合性能。方法 采用离子交联法制备纳米壳聚糖溶液,并对ACQ防腐木进行改性,考察纳米壳聚糖?ACQ复合处理后防腐木的抗流失性及物理特性。结果 当壳聚糖与三聚磷酸钠溶液的质量比为5∶1时,壳聚糖纳米粒子的平均粒径为376 nm;纳米壳聚糖与铜离子优良的螯合性使铜离子的固着率从87.89%提升至95.35%;热重结果表明,纳米壳聚糖?ACQ复合处理后木材在600 ℃时的炭残留率为22.03%,处理后木材表面的水接触角达到69.5°。结论 采用纳米壳聚糖?ACQ复合处理木材后,铜的抗流失性、热稳定性和疏水性能均得到显著提升。     

原位同生法制备纳米铜改性酚醛树脂

利用新发明的原位同生法成功地制备了摩擦材料用纳米铜改性酚醛树脂。经过X射线衍射分析证实，利用该方法制备的树脂中含有单质铜。用透射电子显微镜表征了铜粒子的形貌：呈球形，粒径为10nm～40nm。通过热重分析和冲击试验，对合成树脂的热性能和韧性进行了研究。结果显示，制备树脂的初始分解温度和半分解温度随纳米铜含量的增加先升高后降低，在含量为7％时分别达到最大值；制备树脂基摩擦材料的冲击强度随纳米铜含量的增加先增大后下降，在含量为5％时达到最大值。建立了纳米铜粒子与酚醛树脂相互作用的物理模型，并分析了纳米铜提高酚醛树脂热性能和韧性的机理。     

纳米Pb和Bi的热稳定性

利用综合热分析仪(DSC-TG)对纳米Pb(粒晶为90～150nm)和Bi(粒晶为90～130 nm)与体相Pb和Bi的熔点和熔化焓以及热稳定性等热力学性质进行了研究.实验结果表明纳米Pb和Bi比块体的Pb和Bi有更高的吸附能力和化学活性.纳米Pb比块体的Pb熔点降低2.3℃,熔化焓降低59.0%,纳米Bi比块体的Bi熔点降低5.3℃,熔化焓降低47.95%.     

聚合物/无机纳米复合材料热点述评

1 纳米及纳米科技概述 纳米是一种尺寸的计量单位，1nm为一米的十亿分之一，相当于10个氢原子一个挨一个排起来的长度。这种超微粒子具有如下三个基本特征。(一) 表面、界面特性，其粒径为10nm至1nm时，表面原子数所占比例为20％至99％，大量的孤键和悬键的存在使得纳米粒子具有很高的表面能和很大的化学活性。(二)小尺寸效应，进入纳米尺寸，物质周期性边界条件被破坏，导致了磁性、光吸收、热、化学活性及熔点等发生了变化。如铁的抗断裂能力是普通铁的13倍；气体通过纳米材料速度为一般材料的数千倍；纳米陶瓷具有超塑性；纳米材料电阻随…     

Cu/SiO2纳米复合气凝胶的制备与表征

采用含铜硅酸乙酯(CuTEOS)进行溶胶-凝胶反应来制备高Cu含量的Cu/SiO2纳米复合气凝胶,复合气凝胶中的Cu含量可在小于66%(质量分数)的范围内调节.研究了水量、催化剂浓度、溶剂量及含铜硅酸乙酯的组成对溶胶-凝胶过程的影响.本研究中Cu/SiO2纳米复合气凝胶中粒子粒径大部分小于25nm,其孔径小于50nm,比表面积在400～650m2/g范围内.     

酞菁铜纳米微粒的制备及其聚集态行为

利用气体冷凝法成功地制备了平均粒径约20～100 nm的有机半导体材料酞菁铜(CuPc)纳米微粒,并讨论了不同的热场空间分布范围,加热温度对CuPc纳米微粒的粒径及其聚集态行为的影响。     

微观尺度下单晶铜熔点多因素影响的分子动力学模拟研究

基于分子动力学方法,利用嵌入原子势(EAM)函数,在微观尺度下研究了影响单晶铜熔点的多种因素。首先利用势函数计算单晶铜的晶格常数和弹性常数,以此验证本研究所采用势函数的准确性,然后利用能量体积法、径向分布函数法和键对分析技术对模拟得到的结果进行分析,测得单晶铜熔点约为1 380K。分析了模型大小、升温速率、晶体缺陷对铜熔点的影响,研究发现模型大小、升温速率对熔点的影响不大,随着升温速率的增大,达到熔点所需的时间越短。晶体缺陷的存在使金属材料晶格点阵稳定性下降,熔化需要的热量减少,熔点相应降低,与实际熔点情况一致。     

Effects of addition of copper particles of different size to Sn-3.5Ag solder

In this study, copper particles with different sizes 20–30 nm, 3 and 10 μm were incorporated into Sn-3.5Ag solder paste to form Sn–Ag–Cu composite solder. The Cu particles were added at 0.7 and 3% by paste mixing for 30 min. The composite solder samples were prepared on copper substrate at 240°C for 60 s. Differential scanning calorimetry was conducted to measure the melting point of the composite solder. The wetting angle and microstructure of the composite solder were studied using optical microscope and scanning electron microscope. Micro hardness was measured using a 10 gf load. It was reported that the lowest melting point was obtained at 216.3°C when Cu nanoparticles was added at 3% to Sn-3.5Ag. The microstructure of Sn-3.5Ag solder structure was dendritic in nature. With the addition of Cu nanoparticles, the microstructures were modified with more refined Sn structures. The existence of sunflower morphology of un-melted copper was observed when Cu microparticles were added.     

Application of the embedded-atom method to liquid copper

A procedure for calculating the embedded-atom method (EAM) potential with the use of diffraction data for the metal near its melting point has been applied to copper at temperatures from 1423 to 7400 K. In optimizing the parameters of the EAM potential, we used the pair correlation functions of copper at 1423 and 1873 K, the thermodynamic properties of liquid copper under ordinary conditions, and flash heating and shock compression results. Molecular dynamics simulation with the EAM potential adequately represents the thermodynamic properties and structural characteristics of liquid copper up to 1873 K. The simulated 1423-K bulk modulus is close to the experimentally determined one. At low pressures, the self-diffusion coefficient rises as a power law function of temperature with an exponent close to 2.10. The simulated melting point of copper, 1384 ± 3 K, is close to the actual one. Simulations were performed at temperatures of up to 7400 K and densities a factor of 1.6 higher than the normal one. The melting point was evaluated at pressures of up to 50 GPa. The EAM potential obtained is suitable for the liquid phase but fails to accurately describe properties of crystalline copper.     

纳米Al_2O_3强化铜基ODS 20的组织与性能

研究了铜基ODS的组织与性能。结果表明,采用内氧化方法生产的铜基ODS 20,在纯铜基体上原位生成弥散、10nm左右的-γAl2O3微粒。该材料导电率约90%IACS,比纯铜导电率约降低10%。加工状态的室温强度可达到610MPa,在1173K保温1.5h,硬度达到室温硬度的86%,表明软化温度高于1173 K。经1273K+1.5h退火,晶粒平均直径小于1μm,Al2O3微粒不发生熔解、聚集、长大等现象。     

Melting behaviour of cadmium particles embedded in an aluminium matrix

An Al-4.5% Cd alloy has been manufactured by melt spinning to produce a microstructure of 14–150 nm diameter faceted cadmium particles embedded in an aluminium matrix. The melting behaviour of the cadmium particles has been investigated by differential scanning calorimetry. The melting point of 20 and 14 nm diameter cadmium particles embedded are depressed by 7 and 9 K respectively, below the bulk equilibrium cadmium melting point, because of Gibbs-Thomson capillarity effects. The average solid cadmium particle/aluminium matrix interfacial energy is 27 mJ m^–2 higher than the average liquid cadmium particle/aluminium matrix interfacial energy. No significant superheating is needed to nucleate cadmium particle melting.     

微乳法制备参数对纳米锡银铜焊粉熔点的影响

用微乳法制备低熔点纳米锡银铜焊粉并揭示其机理,研究了表面活性剂、锡前驱体和微乳液比例对合成的纳米SAC粒子熔点的影响。在最优工艺参数条件下合成的纳米Sn3.0Ag0.5Cu其熔化起始温度为183.6℃,比市售焊锡膏(217.8℃)降低了32.2℃,与传统Sn-Pb焊料的最低熔点183℃接近。     

Realization of the Temperature Scale in the Range from 234.3 K (Hg Triple Point) to 1084.62°C (Cu Freezing Point) in Croatia

This article describes the realization of the International Temperature Scale in the range from 234.3 K (mercury triple point) to 1084.62°C (copper freezing point) at the Laboratory for Process Measurement (LPM), Faculty of Mechanical Engineering and Naval Architecture (FSB), University of Zagreb. The system for the realization of the ITS-90 consists of the sealed fixed-point cells (mercury triple point, water triple point and gallium melting point) and the apparatus designed for the optimal realization of open fixed-point cells which include the gallium melting point, tin freezing point, zinc freezing point, aluminum freezing point, and copper freezing point. The maintenance of the open fixed-point cells is described, including the system for filling the cells with pure argon and for maintaining the pressure during the realization.     

Diamond synthesis by weak shock loading

A hexagonal polymorph of diamond has been synthesized by relatively weak shock loading (in a range of projectile velocity 0.655 to 1.88 km sec^–1) with a recovery technique. Four mixtures of copper with spectroscopic graphite, amorphous carbon, glassy carbon and graphite fluoride, with densities of 4.8 to 7.8 g cm^–3, were used to control the shock temperature rise and to quench efficiently. Spectroscopic graphite gave the maximum yield of diamond (8%). Chaoite was also observed in the shocked amorphous carbon and glassy carbon. A local temperature rise during shock was inferred from the temperature of some spherical particles, indicative of superheating of the particles to near or above the melting point.     

烧结温度对铜复合电子浆料烧结膜组织和性能的影响

烧结温度和玻璃粉熔点对铜复合电子浆料烧结膜的性能有重要影响。本文选用熔点为430℃的玻璃粉作为复合电子浆料的粘结相,采用四探针测试仪、扫描电镜(SEM)等方法研究了不同烧结温度下导电铜膜的电阻率及其微观结构。结果表明460℃烧结时,玻璃液粘度适中,能完全润湿、包覆铜粉,且铜粉能均匀悬浮在玻璃液中,制得的导电膜平整、致密,导电通道多,因而导电性能较好,同时玻璃液凝固、收缩使膜层与基体之间获得良好的附着力和抗老化性能。     

Observation of particle behavior in copper powder compact during pulsed electric discharge

The behavior of spherical copper powder particles of uniform size (average diameter: 550 μm) in a powder compact was observed under an optical microscope during a single-pulse electric discharge of 500 ms duration. The morphologies of necks formed between powder particles were observed under a scanning electron microscope, and their diameters were measured. The results obtained are summarized as follows: pressure and pulsed current density determine whether or not a spark occurs. Spark is more likely to occur at interparticle contacts under low pressure and high current density. Where a spark occurs, particles are joined together by melting. Regardless of whether or not a spark is observed, necks are formed at points of contact between particles and neck diameter increases with pulsed current density. These results suggest that microscopic sparking, melting, and vaporization occur by means of extremely high temperature attained by local heat generation at the interparticle contacts in the initial stage of compaction.