Alloying and dealloying of CuPt bimetallic nanocrystals

Bimetallic CuPt nanocrystals with size ranging from 3 to 30 nm were synthesized in the presence of either hexadecylamine or poly(vinylpyrrolidone) as a capping agent.Different growth stages of CuPt nanoparticles prepared with hexadecylamine have been investigated and a non-classic mechanism governing the formation of the metal alloy was revealed.It was found that the precursor molecules aggregate into amorphous spheres at a very early stage,followed by surface multiple nucleation,formation and combination of crystalline islands to produce a core-shell structure with surface-to-core extension of the crystallization to achieve single crystals.CuPt nanocrystals synthesized with poly(vinylpyrrolidone) grew via the classic route.Dealloying treatment was applied on these CuPt nanoalloys to selectively remove Cu.Large particles(30 nm) with Cu-rich cores exhibited hollow structures after dealloying while 3 nm particles remained solid,demonstrating that particle size and composition have a great influence on the final morphology of dealloyed particles.     

纳米多孔铜带的制备及表征

以Cu15Al85合金薄带为前驱体,采用去合金化法,制备孔结构单一、均匀且三维贯通的纳米多孔铜（NPC）,研究不同去合金腐蚀液和退火处理条件对样品微观形貌的影响。经场发射扫描电镜（FE-SEM）、X-射线衍射（XRD）和能谱仪（EDS）对 NPC 检测,结果表明：与在 w（HCl）=5%的酸性腐蚀液中自由腐蚀去合金化得到的 NPC 相比,经 w（NaOH）=5% 的碱性腐蚀形成的 NPC 的多孔结构更加完整,孔径由150 nm 减小到100 nm,孔壁由40 nm 减小到10 nm;对前躯体合金薄带进行退火处理后,去合金化形成的 NPC 多孔形貌更加完整均一,孔径尺寸由 150 nm 减小到 100 nm。     

退火温度对溅射Al膜微结构及光学常数的影响

用直流溅射镀膜工艺在室温Si基片上制备了250nm厚的Al膜,并用X射线衍射及反射式椭偏光谱技术,对薄膜的微结构和光学常数在不同退火温度下的变化进行了测试分析。结构分析表明:退火后的Al膜均呈多晶状态,晶体结构仍为面心立方;随着退火温度由室温20℃左右升高到400℃,薄膜的平均晶粒尺寸由22.8nm增加到25.1nm;平均晶格常数(4.047)略比标准值4.04960小。椭偏光谱测量结果表明:2600～8300光频范围内,退火温度对折射率n影响较小,对吸收系数k的影响较为明显。     

CdS纳米颗粒的合成、表面修饰及光学特性研究

用一步室温固相化学反应法合成CdS纳米颗粒,并以氨催化水解法对其表面进行了修饰,得到了具有CdS／SiO2核／壳结构的纳米微球,以透射电子显微镜和X-射线衍射仪对其结构和物相进行了表征,并研究了其光致发射光谱的性质,研究结果表明：固相反应完全,产物为纯相CdS,室温固相化学反应法避免了传统湿法存在的团聚现象的缺点,具有产率高、无污染、节能等优点;而且CdS纳米颗粒表面经SiO2修饰后,其带边发射显增强,缺陷发射减弱,且在一定范围内随着SiO2包覆层厚度的增加,荧光强度增加。     

原位纳米增强高强韧钢氢脆性能研究

We investigated the critical influence of in-situ nanoparticles on the mechanical properties and hydrogen embrittlement (HE) of high-strength steel. The results reveal that the mechanical strength and elongation of quenched and tempered steel (919 MPa yield strength, 17.11% elongation) are greater than those of hot-rolled steel (690 MPa yield strength, 16.81% elongation) due to the strengthening effect of in-situ Ti₃O₅–Nb(C,N) nanoparticles. In addition, the HE susceptibility is substantially mitigated to 55.52%, approximately 30% lower than that of steels without in-situ nanoparticles (84.04%), which we attribute to the heterogeneous nucleation of the Ti₃O₅ nanoparticles increasing the density of the carbides. Compared with hard TiN inclusions, the spherical and soft Al₂O₃–MnS core–shell inclusions that nucleate on in-situ Al₂O₃ particles could also suppress HE. In-situ nanoparticles generated by the regional trace-element supply have strong potential for the development of high-strength and hydrogen-resistant steels.     

Fe_3O_4@Au核壳结构的制备及在苯乙烯环氧化中的研究

以FeCl3·6H2O为铁源,乙二醇为还原剂,聚乙二醇为表面活性剂,在200℃水热条件下制备平均粒径约为300 nm的介孔Fe3O4.以3-氨丙基三乙氧基硅烷(APTES)为偶联剂对Fe3O4进行改性,室温超声下用柠檬酸钠将Au3+还原为Au0,制备了Fe3O4@Au核壳材料.利用扫描电镜(SEM),N2-吸附-脱附等温线,X射线衍射(XRD),傅里叶变换红外对核壳材料进行表征,结果表明,比表面为95.56 m2/g、孔径为5.67 nm,Fe3O4表面被金均匀涂层,其具有较好的光催化环氧化选择性.     

二氧化钛包裹竹红菌素纳米粒的制备和表征

采用溶胶-凝胶法合成二氧化钛包裹竹红菌素纳米粒,并利用透射电镜和粒度分析仪对其形貌和粒子大小进行测定,证明粒子呈球形,平均直径在100 nm左右;采用紫外和荧光光谱研究二氧化钛包裹竹红菌素纳米粒的光谱性质,并与未包裹的竹红菌素在水溶液中的光谱性质进行了比较,结果表明,竹红菌素被成功地包裹于二氧化钛纳米粒中;包裹后竹红菌素的光谱吸收峰红移,强度增加.由此,将有利于竹红菌素在光动力疗法中的应用.     

Glass-forming ability,microhardness, corrosion resistance,and dealloying treatment of Mg60?xCu40Ndx alloy ribbons

The influence of Nd addition on the glass-forming ability (GFA), microhardness, and corrosion resistance of Mg60?xCu40Ndx (x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical me-thods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corro-sion potential and corrosion current density obtained from the Tafel curves indicate that the Mg35Cu40Nd25 ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper (NPC) was synthesized through a single-step dealloying of Mg60?xCu40Ndx (x = 5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L?1 H2SO4 solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the sur-face diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed.     

PEO修饰中空SiO2纳米颗粒的制备及生长机理研究

采用基于PluronicF127胶束的软模板法,在中性、室温和无催化剂的温和环境下,制备得到中空SiO2纳米颗粒.利用透射电子显微镜(TEM)、动态光散射粒度分布测定仪(DLS)和傅里叶转换红外光谱仪(FT-IR)对所制备的中空SiO2纳米颗粒的形貌、粒径和官能团进行分析.结果表明:SiO2壳层成功在F127胶束疏水-亲水界面处形成,PEO在中空SiO2纳米颗粒表面可自由伸展,纳米颗粒的尺寸随F127浓度增加而减小,但分散性随F127浓度增加而增强.F127质量为15mg、四甲氧基硅烷为46μL时制备的中空SiO2纳米颗粒的平均粒径和内径分别为20nm和9.6nm,且具有更好的水溶性和单分散性.通过对样品的TEM照片统计分析发现,中空SiO2纳米颗粒的外径、内径和SiO2壳层厚度与F127浓度密切相关.     

尖晶石纳米粉体的微晶结构与吸光特性

为开发新的性能更优异的光催化剂,采用无机盐溶胶—凝胶法制备了CoAl2O4、MgFe2O4、CoFe2O4和CoCr2O4等12种尖晶石纳米粉体。利用X射线衍射光谱仪（XRD）和紫外—可见漫反射光谱仪（UV-Vis）对其微晶结构和吸光性能进行了对比研究。结果表明,所制备纳米粉体均具有尖晶石型晶体结构,属立方晶系,Fd/3m空间群,粒子尺寸为4～17nm;其可见光吸收性能普遍优于非磁性尖晶石纳米粉体,且磁性尖晶石纳米粉体的光吸收极限波长大于800nm,禁带宽度小于1.55eV。CoAl2O4、MgFe2O4、CoFe2O4和CoCr2O4四种尖晶石型纳米粉体具有优良的可见光响应性能。     

新型银-二氧化硅核-壳型复合纳米粒子的合成与表征

利用正四甲氧基硅在微乳液介质中的水解反应合成新型银 -二氧化硅核 -壳型复合纳米粒子 .通过化学反应调控 ,直径为 5～ 1 0 nm的金属银纳米粒子可以以单核或多核形式嵌入并分布于球型二氧化硅粒子中 .透射电子显微镜照片表明 ,该复合粒子具有高度均匀的粒径分布 .     

超声波对固体颗粒表面性质的影响

研究了在不同频率、功率、时间、温度条件下超声波对固体颗粒大小的影响;探讨了超声波对十六烷基三甲基溴化铵(HDTMA)阳离子表面活性剂在固体颗粒表面解吸性能的影响.结果表明:功率越大、时间越长,超声波作用后固体颗粒粒径均值越小.温度升高,固体颗粒的运动性能增强,超声波作用后粒径均值在55℃时最小,且在频率为40 kHz、功率为50 W、作用时间为50 min及55℃时,颗粒长轴均值从12.575μm减小到7.799μm,短轴均值从6.998μm减小到5.453μm.同时超声波发生器的功率越大、时间越长、温度越高,黏土颗粒表面吸附HDTMA的解吸率增大,且当频率为80 kHz、功率为50 W、时间为50 min、温度为65℃时,其解吸率可达64.69%.     

微乳液法制备CdSe/CdS核壳纳米粒子及表征

研究了SDS/异戊醇/环己烷/水所组成的四元微乳体系,并将该体系用于CdSe及CdSe/CdS(核壳结构)纳米粒子的制备.在反应过程中以紫外可见吸收光谱考察了不同反应条件下粒子的成核与生长情况.实验得到的CdSe微乳液非常稳定,室温下放置数月仍未见有沉淀生成.使用荧光分光光度计和高分辨透射电镜对粒子进行表征,所得CdSe/CdS纳米粒子粒径为5 nm左右,粒径均一且具有较高的荧光强度.     

尖晶石型CoAl2O4包覆云母钛珠光颜料的制备及其表征

以云母为基质,TiCl4为原料,采用强迫水解法制备了云母钛前驱体;再以Co(NO3)2.6H2O和Al(NO3)3.9H2O为原料,利用化学共沉淀法制备了尖晶石型CoAl2O4,并将其包覆在云母钛前驱体上,制备出蓝色云母钛珠光颜料.采用红外光谱和X射线衍射对产品进行了表征,并对产品进行了性能测定.蓝色云母钛珠光颜料表面包覆了金红石型TiO2和尖晶石型CoAl2O4,具有较好的珠光光泽并且性质稳定.     

Aqueous phase synthesis and fluorescence properties of inverted core/shell ZnSe/CdSe nanocrystals

We report a facile aqueous phase synthesis for prepar-ing water-soluble inverted core/shell ZnSe/CdSe semiconductor nanocrystals. The samples were characterized by X-ray diffraction (XRD),transmission electron microscopy (TEM),and their optical properties were investigated by using UV-vis-NIR spectropho-tometer and fluorescence spectrophotometer. The results indicate that the synthesized ZnSe/CdSe nanocrystals are inverted core/shell structure with diameter of about 5 nm. Furthermore,their absorption band-edge is red-shifted with the growth of CdSe shell; correspondingly,their emission wavelength can be tuned from 460 nm to 604 nm.     

Synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> magnetic composite nanoparticles by a one-pot process

Fe₃O₄@SiO₂ core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe₃O₄@SiO₂ core–shell structures from prepared Fe₃O₄ nanoparticles. The properties of the Fe₃O₄ and Fe₃O₄@SiO₂ composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe₃O₄ particles were approximately 12 nm in size, and the thickness of the SiO₂ coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe₃O₄@SiO₂ powder (34.85 A·m2·kg–1) was markedly lower than that of the Fe₃O₄ powder (79.55 A·m2·kg–1), which demonstrates that Fe₃O₄ was successfully wrapped by SiO₂. The Fe₃O₄@SiO₂ composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.     

激光热致相变核-壳微胶囊的合成与性能

以甲基丙烯酸甲酯作为主要的核单体，甲基丙烯酸缩水甘油酯作为壳单体，叔胺盐作为壳的改性剂，合成了平均粒径为55nm具有激光热致相变性能的核壳微胶囊。用红外光谱对其结构进行了表征；用透射电镜观察了微胶囊形貌；用示差量热分析法、热重分析法测定了热性能、接触角仪测定了相变前后的亲水性，探讨了对相变效果的影响因素。核聚合物的玻璃化转变温度为56.2℃，壳聚合物的玻璃化转变温度为85.3℃；该微胶囊感激光后发生相变，接触角由初始的20°变为93°。     

Glass-forming ability,microhardness, corrosion resistance,and dealloying treatment of Mg60-xCu40Ndx alloy ribbons

The influence of Nd addition on the glass-forming ability (GFA), microhardness, and corrosion resistance of Mg_60-xCu₄₀Nd_x (x=5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical methods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corrosion potential and corrosion current density obtained from the Tafel curves indicate that the Mg₃₅Cu₄₀Nd₂₅ ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper (NPC) was synthesized through a single-step dealloying of Mg_60-xCu₄₀Nd_x (x=5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L-1 H₂SO₄ solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the surface diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed.     

超声场下不同形貌银胶体的制备与表征

为了研究制备工艺条件对不同形貌银胶体稳定性的影响,在超声场作用下,以AgNO3为前驱物,聚乙烯吡咯烷酮为保护剂,KBH4和N2H4·H2O分别为还原剂,制备了稳定的银胶体,并利用透射电镜和分光光度技术对制备的银胶体进行了表征．结果表明,超声场分布、超声作用时间、超声功率和还原剂种类等对银纳米粒子形貌影响较大．未经超声处理的银胶粒为较大的类球形和六边形,随着超声作用时间和超声功率的增加,颗粒变小．驻波场下制备的银颗粒具有一定的生长取向,有利于类球形和六边形银纳米颗粒的形成,而在扩散场中得到单分散的球形银纳米颗粒．经超声场处理的银胶体稳定性增强,主要以单分散的球形纳米颗粒存在,平均粒径约为20 nm,放置数周后未出现聚沉物．改变还原剂的种类,可制备出球形、类球形和六角形银纳米颗粒．     

Cu纳米粒子的光化学制备及其可逆生长-溶解现象简

采用光化学方法在五水硫酸铜（CuSO4·5 H2 O）的乙二醇溶液中制备了Cu纳米粒子,通过反应过程中的紫外可见光谱（UV-Vis）探讨了反应历程。采用扫描电镜、X射线衍射仪和能谱仪分析了产物的形貌、物相、晶体结构和化学组成,并研究了光化学法制备Cu纳米粒子的反应参数。研究结果证明了反应仅在隔绝空气,紫外光引发的条件下才能发生,发现了生成的Cu纳米粒子敞口静置时会被溶解在胶体中的氧气逐渐氧化,再次在隔绝空气的条件下用紫外光照射后,又会重新生成Cu纳米粒子的现象,并讨论了出现这一现象的原因。而加入三乙醇胺后,同样在隔绝空气,紫外复色光照射的情况下,Cu纳米粒子会优先生长在表面上,采用这种方法,在氧化铟锡（ITO）导电玻璃上制备得到了Cu纳米粒子。