Bulk nanocrystalline Al prepared by cryomilling

Bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature (cryomilling) and then by hot pressing in vacuum. By using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), the microstructure evolution of the material during cryomilling and consolidation was investigated. With increasing the mill- ing time, the grain size decreased sharply and reduced to 42 nm when cryomilled for 12 h. The grains had grown up, and the colum- nar grain was formed under the hot pressing and extrusion compared with the cryomilled powders. The grain size of as-extruded specimen was approximately 300-500 nm. The reason of high thermal stability of this bulk was attributed primarily to the Zener pin- ning from the grain boundary of the AlN arising from cryomilling and the solute drag of the impurity. Tensile tests show that the strength of nanocrystalline Al is enhanced with decreasing grain size. The ultimate tensile strength and tensile elongation were 173 MPa and 17.5%, respectively. It appears that the measured high strength in the cryomilled Al is related to a grain-size effect, disper- sion strengthening, and dislocation strengthening.     

半导体器件钝化层Si3N4薄膜的制备及特性研究

采用热分解法在硅衬底上制备了Si3N4薄膜，根据在制备过程中薄膜生长速度随颜色的变化，研究了衬底温度和薄膜沉积速率之间的关系，分别利用AFM对薄膜表面进行观测，C—V法对薄膜和硅片界面态进行了测试。结果表明：所制备的Si3N4薄膜在硅片上以无定形方式存在，在Si3N4薄膜和硅界面之间存在着大量的表面电荷，由于这种高密度表面电荷的存在，导致Si3N4薄膜不适于直接作为半导体器件的表面钝化层。     

电势对硅片摩擦电化学材料去除特性的影响

为了提高硅片抛光效率,改善抛光表面质量,采用电化学交流阻抗谱法实验研究了极化电势对硅片表面钝化作用的影响规律,结合摩擦电化学实验探讨了极化电势对硅片表面摩擦系数及材料去除特性的影响．结果表明,在碱性CeO₂抛光液中,对硅片施加1 V阳极极化电势能够促进其表面形成抑制腐蚀的钝化层,极化电势过高会破坏表面钝化层,过低则抑制钝化层形成．良好的硅片表面钝化层能够有效增大其摩擦系数,提高摩擦电化学实验过程中的材料去除率．     

非晶/纳米晶磁粉芯的热压制备工艺探究

在不使用粘接剂的条件下,通过Gleeble-3500热模拟试验机将Fe-Si-B-Cu-Nb非晶合金粉末在其过冷液相区直接热压成型,制备成非晶/纳米晶磁粉芯。研究热压压力和热压时间对非晶/纳米磁粉芯密度的影响,并与传统冷压或温压成型条件下获得的非晶/纳米晶磁粉芯的性能进行比较。结果表明,在180 MPa,快速升温到723 K,再缓慢升温到773 K,保温1 h,最后空冷的热压工艺条件下,制备的磁粉芯样品中形成了纳米微晶镶嵌于非晶体的非晶/纳米晶双相结构。与传统冷压或温压条件下制备的磁粉芯相比,制备的磁粉芯具有更高的密度,约为6.8g/cm3;较高的饱和磁感应强度,约为1.34T;较低的矫顽力,约为2A/m。     

Mechanistic investigation into the role of aluminum diffusion in the oxidation behavior of cryomilled NiCrAlY bond coat

High temperature oxidation behavior of the bond coat layer is a critical factor that controls the failure mechanism of thermal barrier coatings (TBCs). Previous work reveald that TBCs with cryomilled NiCrAlY bond coats exhibited an improved oxidation behavior compared to equivalent TBCs with conventional bond coats. The cryomilled NiCrAlY bond coats contributed to a slower growth rate of thermally grown oxides (TGO) with a final thinner thickness and enhanced homogeneity in TGO composition. To better understand the improved oxidation behavior, a mechanistic investigation based on diffusion theory and quantum mechanics is performed to elucidate the role of aluminum diffusion in the oxidation behavior and how the microstructural features of the cryomilled NiCrAlY bond coats, i e, the creation of a thermally stable, uniform distribution of ultrafine Al-rich oxide dispersoids, affect the diffusion kinetics of Al and the migration of free electrons. It is revealed that these Al-rich oxide dispersoids result in a uniform diffusion of Al and slow migration of free electrons within the NiCrAlY bond coat, consequently leading to the improved oxidation behavior.     

一种含硅丙烯酸酯共聚物及表面性能研究

以γ-甲基丙烯酰氧丙基甲氧基三（三甲硅氧基）硅烷和甲基丙烯酸甲酯为原料制备不同硅含量的含硅共聚物。测试了共聚物的Tg、表面接触角、表面自由能,同时对共聚物进行FTIR和表面电子能谱（XPS）分析。结果表明,随着共聚物中硅单体含量的增加,其表面能显著降低,且共聚物在成膜过程中,含硅基团有向共聚物-空气界面富集的趋势。     

碳化硅粉体表面乳液聚合处理及特性研究

利用乳液聚合方法对碳化硅粉体表面进行聚电解质包覆改性，处理后碳化硅粉体表面特性发生改变，不易团聚，可以制成固相含量较高的稳定的悬浮液。分析了聚电解质处理后的碳化硅粉体悬浮液的特性，结果表明：碳化硅粉体表面的疏水性越好，其沉降性越好，悬浮液的固相含量就越高。     

CeY分子筛对HDS汽油的吸附脱硫及表面酸性的影响规律

用固相离子交换和液相离子交换法制备了CeY分子筛,利用X射线衍射(XRD)、N2物理吸附脱附、电感耦合等离子原子发射光谱仪(ICP)等方法表征了吸附剂的物理性质,借助NH3-TPD及吡啶-原位傅里叶变换红外(Py-FTIR)技术考察了吸附剂表面的酸度分布及酸类型。采用固定床动态吸附实验和色谱-硫化学发光检测(GCSCD)偶联技术系统考查了改性Y分子筛对加氢脱硫燃料油的吸附脱硫性能。结果表明,4种Y分子筛对加氢脱硫油脱硫能力大小顺序为S-CeYL-CeYNaYHY。表面酸性的差异显著地影响分子筛的吸附脱硫性能,两种方法制备的CeY分子筛表面酸性与NaY原粉差异较大,分子筛表面B酸中心是噻吩发生催化反应的活性中心。     

片状锌粉的可控钝化及电性能研究

采用水/酒精、双氧水溶液为氧化剂,制备了表面钝化Zn(OH)2的片状锌粉.采用X射线衍射(XRD)、热重分析(TG)、扫描电镜(SEM)对钝化锌粉进行了表征,考察了钝化增重对锌粉压片电阻率和漏电流密度的影响.结果表明,锌粉钝化后在表面形成鼓包状组织,随着氧化剂浓度和时间的增加,锌粉钝化增加;随着钝化膜的增厚,钝化锌粉的电阻率增加,漏电流密度减小.     

热氧化处理对氮化硅粉料表面可溶性离子的影响

选用一种商业氮化硅粉料,研究了可溶性高价反离子对其水中分散性能的影响,并研究了粉料表面的几种可溶性金属离子在热氧化处理过程中的变化规律.研究发现,初始氮化硅粉料分散性能的限制性因素是可溶性（Ca^2＋＋Mg^2＋）的浓度过高所致.一价可溶性离子Na^＋和K＋非常稳定,热氧化处理基本上不改变其在氮化硅颗粒表面的存在状态.对于Ca^2＋,Mg^2＋和Fe^3＋而言,热氧化处理显著改变了其在氮化硅颗粒表面的存在状态,由可溶性的高价反离子变成了难溶性的氧化物.对Fe元素而言,除了变成难溶性的氧化物外,在热氧化过程中还发生了由氮化硅粉料表面向颗粒内部的扩散.     

纳米晶Li7Si3合金的制备与性能表征

为研究纳米结构锂电池阳极材料的特性,试制了纳米晶Li-Si合金.采用优化的纳米晶合金块体材料制备工艺,即熔炼制备粗晶Li7Si3合金铸锭、高能球磨得到Li7Si3非晶粉末,结合放电等离子烧结(spark plasma sintering,SPS)制备得到了纳米晶Li7Si3合金,并对其进行了Rietveld结构精修和杨氏模量测定.结果表明:纳米晶Li7Si3单胞结构参数为a=b=0.4452 nm(比粗晶增加0.38%),c=1.8239 nm(比粗晶增加0.58%),单胞体积Vo=0.313 070nm3(比粗晶增加1.35%).利用纳米压痕法测定纳米晶Li7Si3合金的杨氏模量为(30.6±2.4)GPa.     

Preparation of ZAO powder and investigation on its infrared emissivity

According to the basic infrared stealth mechanism of low infrared emissivity powders,the ZAO powder materials were prepared by liquid coprecipitation method,and the starting materials were Zn( NO3) 6H2O and Al( NO3) 39H2O. The process parameters were obtained,and the relationship between technology parameters and infrared emissivity was investigated. The temperature of thermal treatment,crystal structure and surface micrograph of ZAO powder was analyzed by the help of TG-DTA,XRD and SEM. The infrared stealth performance of ZAO powder was studied by IR-2 emissivity spectroscopy. Results showed that the infrared emissivity was the lowest when pH was 8. 0,calcination temperature was 1100 ℃,calcination time was 2 h,and the Al2O3doping content was 3% ( mass percentage) . The crystal structure of doped ZAO powder was lead-zinc, and there exists distortion of crystal lattice in nanocrystalline ZnO. The average particle size was 10 μm. The lowest infrared emissivity reached to 0. 61 at between 8 μm and 14 μm. It means that the ZAO powders will be excellent infrared stealthy materials.     

电弧喷涂制备铝基非晶纳米晶合金材料

采用高速电弧喷涂技术,制备了铝基非晶纳米晶复合涂层材料.经XRD、TEM分析发现,铝基非晶纳米晶复合涂层是由非晶相、纳米晶相和晶化相共同组成的;涂层呈明显层状结构,层与层之间结合良好;涂层结构致密,无明显裂纹和孔隙,孔隙率约为1.8%;涂层的平均显微硬度值约为311 HV100,已达到传统制备工艺获得的铝基非晶合金的显微硬度值.     

Characterization of Low Pressure RF Plasma Heating

Compacts of a-Al2O3 and Mo powder were heated in radio-frequency (RF) induced low pressure N2, H2,Ar, and their mixture plasma. An optical pyrometer, a radiation pyrometer, and a system called Accufiber Model310 were used to measure the temperature of compacts heated in the plasma. The results indicate that there are different heat transfer mechanisms from plasma to specimens of different physical properties. The Ar plasma showed thehighest heating ability among N2, H2, and Ar plasma for Al2O3 specimens, whereas the H2 plasma could heat Mospecimens to a higher temperature than the Ar plasma did, even under the same generating conditions.     

有机硅高沸副产物应用于防水砂浆的研究

以辛基三乙氧基硅氧烷生产过程中产生的高沸副产物为防水活性成分,选用便宜易得的微硅粉为载体,制备了有机硅防水粉.以液质联用（HPLC-MS）检定高沸副产物,以红外光谱分析、激光粒度仪表征自制防水粉物化性质,并将其试用于防水砂浆中,与DOW CORNING（R）GP SHP 50防水粉进行对比,参照相关标准,测试了防水砂浆的工作性能、力学性能、防水性能.结果表明,自制防水粉在降低成本的同时,其制备方法切实可行,其配制的防水砂浆各项指标均达到标准要求.     

AlGaN/GaN HEMTs表面钝化抑制电流崩塌的机理研究

通过实验测量对AlGaN/GaN HEMT表面钝化抑制电流崩塌的机理进行了深入研究.AlGaN/GaN HEMT Si3N4钝化层使用PECVD获得.文章综合考虑了钝化前后器件输出特性及泄漏电流的变化,钝化后直流电流崩塌明显减少,仍然存在小的崩塌是由于GaN缓冲层中的陷阱对电子的捕获.传输线模型测量表明,钝化后电流的增加是由于钝化消除了表面态密度进而增加了沟道载流子密度.     

LC4铝合金液中电火花表面改质的研究

对LC4铝合金材料工件表面改质时，采用了液中电火花改质工艺．利用自制粉体压制模具，把一定比例的钨、石墨颗粒、聚乙烯醇压制成压粉体电极．在试验中，通过选择电火花机床加工允许范围内的各种电参数进行组合，得到优化的参数，在加工过程中，对压制成的压粉体电极和工件分别采用不同极性的方式，通过电火花放电对压粉体电极蚀除、熔覆至工件表面，形成钨 碳改质层．再用铜电极等消耗小的电极二次加工使改质层和基体结合牢固，并提高改质层的硬度试验表明：LC4铝合金工件表面经液中电火花改质处理后可得到结构致密的改质层，其硬度、耐腐蚀性和耐磨性均显著提高。     

Synthesis of Ag@Cu_2O core-shell metal-semiconductor nanoparticles and conversion to Ag@Cu core-shell bimetallic nanoparticles

Ag@Cu2O core-shell metal-semiconductor nanoparticles(NPs) were prepared by using solution phase strategy. It was found that Ag@Cu2O core-shell NPs were easily converted to Ag@Cu bimetallic core-shell NPs with the help of surfactant PVP and excessive reducer ascorbic acid in air at room temperature, which is a unique phenomenon. Varying volumes of Ag colloidal solutions were added into the reaction mixtures containing fixed initial concentrations of Cu2+ and PVP, Ag@Cu2O and Ag@Cu core-shell NPs with fixed core size but varying outer shell thicknesses could be obtained. The composites, structures, morphologies and extinction properties of Ag@Cu2O and Ag@Cu core-shell NPs were systematically characterized by XRD, TEM and extinction spectra. Both of these NPs show wide tunable optical properties. The extinction peaks could be shifted from 421 nm to 700 nm. FTIR results reveal that Cu+ ions on the surface of Cu2 O nanocrystalline coordinate with N and O atoms in PVP and further are reduced to metallic Cu by excessive ascorbic acid and then form a nucleation site on the surface of Cu2 O nanocrystalline. PVP binds onto a different site to proceed with the reduction until all the Cu sources in Cu2 O NPs are completely assumed. And the shell of Cu2 O is converted to Cu shell. The synthesis approach in this paper is simple and also a promising reference for synthesizing other core-shell NPs. Ag@Cu2O NPs can be easily converted to Ag@Cu NPs in air at room temperature, which is promising to be used in electronic devices.     

球形超细铜粉的制备及其空气中抗氧化的研究

为了研究球形超细铜粉的液相还原制备方法,采用适中还原剂抗坏血酸和强还原剂水合肼、硼氢化钾和次亚磷酸钠分别还原硫酸铜,相比之下,抗坏血酸价格昂贵,反应体系的pH值既影响反应物相也影响产物形貌,因此反应条件不易控制;次亚磷酸钠和硼氢化钾制得的铜粉形貌不规则,分散性很差;而水合肼制得的铜粉形貌不仅为球形,而且大小均一,分散性较好。此外,还研究了缓蚀剂对增强铜粉在空气中的抗氧化性的影响,结果发现:四种缓蚀剂油酸、苯并三氮唑、明胶和阿拉伯树胶中,明胶前处理对增强铜粉在空气中的抗氧化性效果最好;而以水合肼为还原剂、明胶添加量为CuSO4·5H2O质量的5%进行前处理制备的球形超细铜粉粒径最小,可达30 nm左右,且分散性最好。     

激光能量对掺铒纳米Si晶薄膜形貌的影响

采用XeCl脉冲准分子激光器,保持激光脉冲比为1:2,分时烧蚀Er靶和高阻抗单晶Si靶。改变激光能量,在真空中沉积了掺Er非晶Si薄膜。在氮气保护下,分别在950℃,1010℃和1100℃温度下进行30min热退火处理,得到掺Er纳米晶Si薄膜。扫描电子显微镜的结果表明,高的退火温度或高的激光能量均会导致迷津结构的形成。