【作者】 楚广；

【导师】 杨天足；

【作者基本信息】 中南大学 ， 有色金属冶金， 2007， 博士

【摘要】 采用自悬浮定向流方法制备金属Cu、Ag和Al纳米粉体和真空手套箱技术进行隔绝空气防氧化装料，然后在惰性气体保护下由可控制精密液压机进行冷（高）压和真空温压技术分别制备出相对密度分别为96.7％、98.1％和98.5％左右的纳米Cu、Ag和Al块体材料，对压制过程的工艺技术、纳米晶体材料的微观结构和性能进行了深入系统的研究，得到如下主要结果：（1）采用自悬浮定向流法制备金属Cu纳米粉体。在10％He和90％Ar的混合气流中和在Ar气气流中制备的纳米Cu粒子形貌呈球形、平均粒度分别为45nm左右和60nm；纳米Cu粒子表面Cu和O元素的原子比为94.88：5.12，有少量氧化亚铜和氧化铜的混合物存在，但在其（包括热分析后的残留物）表面中未发现Ar和N元素。（2）在He气和Ar气流中制备的纳米Ag粉的平均粒径分别为15nm和80nm；在He气流中制备的粒径小些，颗粒基本为球形。熔点为959.7℃，比粗晶银的熔点（961.93℃）低2.23℃。（3）在Ar气流中制备的纳米Al粉的平均粒度为50nm的球形金属纳米Al粉，放置半年后含氧量（Wt％）为8.2％。在Ar气流中，新纳米铝粉的熔点为649.7℃。在纳米铝粉中未发现Ar元素存在；而在N₂气流中进行热分析后的纳米铝粉残余物中发现有N元素，说明纳米铝粉在热分析的加热过程中与N发生了化学反应。（4）对于冷压法制备金属纳米晶体Cu样品而言，压力对最终样品的密度影响很大，密度随着压力的升高而增大。材料的热稳定性好，晶粒度未退火时为19.9nm，微应变为0.233％。200℃退火三小时后，晶粒长大不明显，约为30.5nm，微应变为0.18％。。正电子湮没测试表明材料中的微观缺陷主要是单空位及空位团，大空隙的含量很少，随着压制压力的增大，材料中的空位团的相对含量增加，单空位减少，微空隙基本不变。（5）冷压法制备金属纳米晶体Cu样品的显微硬度为1.55～1.90GPa，约为常规粗晶Cu材料的3～4倍；电阻率在室温下约为1.56×10^-7Ω·m，是粗晶Cu在室温下电阻率(0.167×10^-7Ω·m)的9倍。纳米Cu块体材料作靶的激光转换成X射线（Ka线）的转换效率在一激光强度为3×10¹⁸W／cm²时，比常规Cu材料高5倍。有较好的应用前景。（6）冷压法制备的金属纳米晶体Al、Ag的样品在室温下显微硬度分别为2.11、1.26GPa。分别是粗晶Al的14倍，粗晶Ag的2.5倍。它们的熔点分别为645.9℃和955.9℃，表现出纳米材料低熔点的特点。室温下纳米晶体Ag的电阻率为1.475×10^-7Ω·m，是粗晶银在室温下的电阻率(1.59×10^-8Ω·m)的9倍。（7）用真空温压法成功制备了相对密度分别为96.15％、99.66％、97.9％的纳米金属Cu、Ag和Al块体材料，压力增大，延长保压时间，提高压制温度，均有利于其密度的提高。它们的显微硬度分别为3.8GPa、1.2GPa、1.65GPa，是相应普通粗晶材料的8倍、3倍和5倍，体现了纳米金属块体材料的高硬度特性。（8）纳米金属铜块体材料具有较好的热稳定性，在1.5GPa和200℃下压制的样品的平均晶粒度为25.3nm、微应变为0.047％。样品的正电子湮没平均寿命τ为257.07ps，比未抽真空冷压法的（221.70ps）增加36ps。说明真空温压对纳米块体铜的微观结构有影响；其微观缺陷尺寸有所增大。（9）目前，我们制备的纳米晶体材料已经在ICF物理实验中得到初步的应用，本项目获2006年度军队科技进步三等奖。更多还原

【Abstract】 In this thesis, nano-particles of Cu, Ag and Al were synthesized byflow-levitation method and filled into the mold at vacuum gloves chestunder the atmosphere of Ar in order to prevent oxidation. Subsequently,the nano-sized metal particles were compacted by use of exact hydraulicpress with cold-compaction and vacuum-warm-compaction technologyand nanocrystalline Cu, Ag and Al were prepared with relative density of96.7%, 98.1% and 98.5% respectively. The technology of preparation、microstructure and properties of such as-prepared nanocrystalline metalsmaterials were studied systematically and at close range. The results wereobtained as follows:（1） nano-particles of Cu were synthesized by flow-levitation method.The nano-particles prepared in Ar and mixture of 10%He and 90%Arwere globose with average grain size of 45 nm and 60 nm respectively.On the surface of the Cu particles, there were mixture of Cu₂O and CuOand the atom ratio of Cu and O was 94.88:5.12, but the element of Ar andN were not found in the particles（include the residue after thermalanalyses）.（2） The average grain size of nano-particles of Ag prepared in Heand Ar airflow were 15 nm and 80 nm respectively and the former issmaller. The particles were globose and the melting temperature was959.7℃, which was lower than the coarse grained Ag by 2.23℃.（3） The average grain size of globose nanoparticles of Al prepared inAr air flow was 50 nm. The content of O was 8.2% after preserved forhalf a year. The melting temperature of newly prepared nano-particleswas 649.7℃in Ar atmosphere. The element of N was found in theresidue after thermal analyses. But the element Ar was not found. Thisresult indicated that nano-particles of Al could have combined with N₂during the heat process of thermal analyses.（4） As far as nanocrystalline Cu synthesized by cold-compactionconcerned, pressure had a profound influence upon the density and thedensity increased with higher pressure. The as-consolidatednanocrystalline Cu showed high thermal stability during the annealing process. The average grain size and microstrain of un-annealing specimenwere 19.9 nm and 0.233%. After annealing at 200℃for three hours, thatbecame 30.5 nm and 0.18%. The PAS analysis results showed that themost of the defects in the specimen after press was vacancies andvacancy-clusters; the amount of micro-voids is small. During theconsolidation, the amounts of vacancy-clusters growed while the amountof vacancies decreased and the amounts of micro-voids remainedunchanged.（5） The microhardness of the nanocrystalline Cu prepared bycold-compaction was 1.55～1.90GPa, exceeded that of coarse-grained Cuby the factors of 3～4. The electricl resistivity of nanocrystalline Cu wasabout 1.56×10^-7Ω·m, which was about 9 times larger than that of thecoarse-grained Cu sample at room temperature. ICF simulationexperiment indicated that conversion efficiency of X-ray conversedfrom laser of as-prepared nanocrystalline Cu was 5 times higher thanthat of coarse-grained Cu. Nanocrystalline materials have brilliantfuture for application.（6） The microhardness of cold compacted nanocrystalline Al and Agwere 2.11GPa and 1.26GPa, which were higher than their coarse-grainedcounterparts by a factor of 14 and 2.5, respectively. The meltingtemperature of as-prepared nanocrystalline Al and Ag were 645.9℃and955.9℃, which showed lower melting temperature of nanocrystallinematerials. The electrical resistivities of the nanocrystalline Ag at roomtemperature are 1.475×10^-7Ω·m and 1.5×10^-7Ω·m, which are larger thanthe coarse grainedAg (1.59×10^-8Ω·m) by a factor of 9.（7） With vacuum-warm-compaction method, nanocrystalline Cu, Ag,Al were prepared with relative densities of 96.15%, 99.66%, 97.9%,respectively. The microhardness of this three were 3.8 GPa, 1.25 Pa and1.65 Pa, which are higher than their coarse-grained counterparts by afactor of 8,3,and 5,respectively. It showed the property of highmicrohardness of nanocrystalline metallic material.（8） The nanocrystalline Cu showed high thermal stability. Theaverage grain size and microtrain of specimen of nanocrystalline Cu were25.3 nm and 0.047%, when compacted by vacuum warm-compacting method under 1.5 GPa and at 200℃for 1 h, respectively. The averagepositron annihilation lifetime r was 257.07ps, which was larger thanthat of un-vacuum-cold-compacted specimen by 36ps. This indicated thatthe microstructure of nanocrystlalline metals had changed during thecourse of vacuum-warm-compaction and at last, the dimension of themicro-vice became larger.（9） The nanocrystalline metals synthesized in this way had beenapplied primarily in physical experiment at present. This project has wonthe third-class Award of progress in Science and technology of PLA in2006.更多还原