Green synthesis of Ag nanoparticles: Effect of algae life cycle on Ag nanoparticle production and long-term stability

Spherical Ag nanoparticles (AgNPs) were biologically synthesized using four different extracts prepared from Parachlorella kessleri algae cultivated for 1, 2, 3 and 4 weeks. The influence of algae life cycle on AgNPs formation and effect of different storage conditions on AgNPs long-term stability were investigated. The age of algae influenced the rate of AgNPs synthesis and amount of AgNPs in solution. The age of algae did not influence the AgNPs long-term stability. UV–vis and TEM observation revealed that long-term stability of AgNPs can be influenced by storage temperatures, and low temperature positively influences the AgNPs stability. AgNPs stored at dark and at temperature of ～5 °C showed the best long-term stability regardless of the culture age. Such AgNPs remained spherical, fine (5–20 nm) and stable (no agglomeration) even after 6 months.     

Microstructure and magnetic properties of Ti/Co/Ti films

The two series of as-deposited and annealed Ti/Co/Ti thin films were deposited by magnetron sputtering onto glass substrates at room temperature. The structural and magnetic properties of the films at room temperature were investigated as function of Co layer thickness. X-ray diffraction (XRD) profiles show Co nanograins are formed as the hexagonal-close-packed (hcp) structure. The perpendicular coercivity of the Ti(15 nm)/Co(30 nm)/Ti(15 nm) film annealed at 450 ℃ for 30 min is about 288 kA·m-1 .     

Synthesis and magnetic properties of CoPt nanoparticles

CoPt nanoparticles were prepared by simultaneous thermally reducing Co(CH3COO)2 and Pt(acac)2 in oleylamine with a small quantity of oleic acid. The composition of the particles was controlled by changing the amount of the reactants. Transmission electronic microscopy reveals that Co 48 Pt 52 particles with an average diameter of 8.4 nm are steadily dispersed in octane in the presence of oleylamine and oleic acid. Selected area electron diffraction indicates that the as-prepared particles have a face center cubic structure. Magnetic properties of these particles measured by a vibrate sample magnetometer yield a coercivity of 1.194×104 A·m-1 and a saturation magnetization of 5.3 emu·g-1 . After annealing at 650 ℃ for 2 h under the flowing Ar, the coercivity increases to 9.552×104 A·m-1 according to partly phase transformation from face center cubic structure to face center tetragonal structure for the nanoparticles.     

制备工艺对Ag/Co3O4电接触材料物理性能的影响

以水热法合成的Co3O4空心球粉体和化学银粉为原料,运用粉末冶金技术调控不同成型压力、烧结制度等工艺参数制备Ag/Co3O4电接触材料;采用扫描电镜(SEM)、X射线衍射(XRD)、金相显微镜等对其形貌、物相及金相组织进行了表征;对比分析压制烧结条件对电阻率、硬度和密度(致密度)等物理性能的影响。结果表明,100℃水热反应13 h合成的Co3O4为粒径2.2 mm的空心微球粉体。1000 MPa、850℃保温6 h初压初烧后,进一步经复压复烧(1000 MPa、800℃保温6 h)处理,得到的Ag/Co3O4材料物理性能得到提高,其电阻率低至2.78 mΩ.cm,硬度(HV0.5)高至71.7,密度为9.22 g/cm³(致密度95.6%),表明复压复烧工艺有助于实现Co3O4颗粒增强相在银基体上的均匀弥散分布,降低Ag/Co3O4材料的孔隙率,提高其致密度,改善其综合物理性能。     

Ag/SiO2核-壳结构球的制备与光学性质

采用St(o)ber方法,以AgNO3与柠檬盐钠还原反应所制备出的Ag纳米颗粒为种子,合成了Ag/SiO2核-壳结构的亚微米球.用透射电镜(TEM)观测所得产物的形貌和大小,并用光吸收谱仪测试了Ag纳米颗粒的表面等离子体共振(SPR)引起的光吸收峰.     

贵金属Cu、Ag、Au的电子结构和物理性质

由纯金属单原子理论(OA)确定了面心立方结构(FCC)贵金属Cu、Ag、Au的电子结构依次为[Ar](3dn)5.58(3dc)4.21(4sc)0.23(4sf)0.98、[Kr](4dn)4.87(4dc)4.56(5sc)0.66(5sf)0.91、[Xe](5dn)4.20(5dc)4.90(6sc)1.57(6sf)0.33,并确定了Cu、Ag、Au的密排六方结构(HCP)和体心立方结构(BCC)两种初态特征晶体和初态液体的电子结构。根据自然态的电子结构定性解释了熔点、拉伸强度、维氏硬度、体弹性模量、电导和热导率物理性质差异与电子结构的关系,定量计算了晶格常数、结合能、势能曲线及线热膨胀系数随温度的变化。根据非自然态的电子结构,定性解释了晶体结构BCC和HCP的关系。     

Synthesis and optical characterization of Pd–Au bimetallic nanoparticles dispersed within monolithic mesoporous silica

Au–Pd bimetallic nanoparticles dispersed within pores of monolithic silica was synthesized by soaking Au nanoparticles contained silica host into Pd precursor solution and subsequent step-annealing at temperature from 373 to 773 K. Theoretical optical spectra based on Mie-like model for Au_corePd_shell nanoparticles yield excellent agreement with the experimental results.     

Structure and magnetic properties of Cu-Ni alloy nanoparticles prepared by rapid microwave combustion method

Cu-Ni alloy nanoparticles were prepared by a microwave combustion method with the molar ratios of Cu²⁺ to Ni²⁺ as 3:7, 4:6, 5:5, 6:4 and 7:3. The as-prepared samples were characterized by XRD, HR-SEM, EDX and VSM. XRD and EDX analyses suggest the formation of pure alloy powders. The average crystallite sizes were found to be in the range of 21.56–33.25 nm. HR-SEM images show the clustered/agglomerated particle-like morphology structure. VSM results reveal that for low Ni content (Cu₅Ni₅, Cu₆Ni₄ and Cu₇Ni₃), the system shows paramagnetic behaviors, whereas for high Ni content (Cu₃Ni₇ and Cu₄Ni₆), it becomes ferromagnetic.     

Synthesis and Characterization of Ag/Graphene Nano- composite

采用氧化还原法制备不同银含量的银/石墨烯纳米复合材料 (银质量分数分别为0%, 30%, 46%, 56%, 63%)。并通过X射线衍射(XRD)、光电子能谱仪(XPS)、高倍透射电子显微镜(HRTEM)和拉曼光谱(Raman)分析银含量对银/石墨烯纳米复合材料形态和显微结构的影响。结果表明,氧化石墨和银离子被成功地还原成银/石墨烯纳米复合材料,所得石墨烯由3~4单层碳原子层堆砌缠绕而成,同时银纳米颗粒沉积在石墨烯的表面。银纳米颗粒的介入有效地阻碍了石墨烯的团聚,增大了石墨烯的比表面积。银纳米颗粒的尺寸与银含量相关,当银含量较低时,银纳米颗粒在石墨烯表面具有很好的分散性且粒度基本分布在25~50 nm之间,而当银含量超过46%时将会导致银纳米颗粒的团聚。另外, 银纳米颗粒增强了石墨烯的拉曼效应。     

单相纳米晶Ag_2Al颗粒的制备及表征(英文)

采用自悬浮定向流法制备单相Ag2Al金属间化合物纳米颗粒及Ag和Al纳米颗粒;利用透射电镜、X射线衍射、X射线光电子能谱分析、电感耦合等离子体发射光谱等对纳米Ag2Al微晶的形貌、粒度、相组成、成分及微结构进行表征。研究表明:所制备的金属间化合物纳米粒子为球形的六边形结构,其平均粒径为33μm,样品中Ag和Al的摩尔比非常接近标准配比2:1,颗粒由单相的Ag2Al组成。对放置在空气中的Ag2Al纳米颗粒表面成分进行分析,XPS测试结果表明:在Ag2Al微晶表面形成了一层很薄的氧化物膜,可能是铝的氧化物或银铝氧化物。实验证实,通过控制气相反应的工艺条件可以制备出粒径很小的单相Ag2Al纳米晶。     

Ca_3Co_4O_9/Ag陶瓷复合材料的制备及其热电性能

利用高分子网络凝胶法和放电等离子烧结技术(SPS)制备出高致密的Ca3Co4O9/Ag热电陶瓷复合材料.采用X射线衍射法表征了材料的相组成及其织构化程度,用SEM观察了粉体形貌和陶瓷断口的显微结构,并研究了Ag复合量对材料的室温热电性能的影响.研究结果表明,利用高分子网络凝胶法和SPS相结合的工艺有利于单质Ag在基体中的分布,使得基体中Ag相的粒径更小,分布更均匀.陶瓷复合材料的致密度均达到98%以上.虽然Ag颗粒的加入使Ca3Co4O9/Ag复合材料的Seebeck系数降低,但由于电导率显著提高,从而使材料的功率因子提高.     

反应合成Ag/SnO2复合材料挤压过程有限元模拟

通过热力模拟压缩试验研究Ag/SnO2复合材料在不同变形条件下的流变应力行为,并根据试验数据确定再结晶动力学方程及再结晶晶粒尺寸方程中的材料参数,经过有限元模拟得出反应合成法制备的Ag/SnO2复合材料在挤压过程中的晶粒尺寸演变情况及最终晶粒尺寸。与实际挤压后试样的电镜照片进行对比,模拟结果与实验吻合,揭示了挤压过程晶粒尺寸变化的机制和变化特征。     

Synthesis and magnetic properties of nickel nanoparticles deposited on the silicon nanowires

Nickel (Ni) nanoparticles with sizes of ∼35 nm were deposited on the surface of silicon nanowires (SiNWs) by electroless plating technique. The magnetic properties of Ni/SiNWs were investigated. The blocking temperature (T_B) of 370 K was obtained and confirmed by field-cooled (FC) and zero-field-cooled (ZFC) plots. The M-H hysteresis loops from 5 K to 400 K were measured. The saturation magnetization value was ∼4.5 emu/g and the coercivity was ∼375.3 Oe for the loop at 5 K, respectively. While for the loop at 400 K, these values were of ∼2.6 emu/g and ∼33.3 Oe, respectively. The temperature dependence of coercivity followed by the relation H_C(T) = H_C0[1 − (T/T_B)^1/2], indicating a superparamagnetic behavior. The magnetization of superparamagnetic grains in a magnetic field H was better described by Langevin function at 400 K. These novel magnetic properties of Ni/SiNWs were possibly attributed to the paramagnetic defects on the surface of SiNWs.     

Fabrication and microstructural characterization of nano-structured WC/Co coatings

In the present investigation, the microstructure of nano tungsten carbide/cobalt (WC/Co) coating layers fabricated by detonation-gun spraying has been studied. Phase identification and three-dimensional distribution of constituent elements have been accomplished by using an ultra high-resolution transmission electron microscope (TEM) and a three-dimensional atom probe tomography (3D-APT), respectively. The microstructures of WC/Co coating layer containing superfine carbides were observed in various forms, i.e., unmelted, partially melted and fully melted regions. TEM and APT results revealed that the WC phase has been decomposed into crystalline W₂C, W and complex amorphous phases during high temperature detonation spraying and rapid quenching process.     

一种中空金/银双金属纳米颗粒的制备及其SERS性能

以银纳米颗粒为牺牲模板,利用Ag和HAu Cl4之间的置换反应,结合柠檬酸钠同步还原的方法制备了一种中空金/银双金属纳米颗粒。通过对颗粒形貌及局域表面等离子体共振(LSPR)的分析,初步研究了此类金/银纳米颗粒的生长机理,并对影响反应的因素进行了探讨。结果表明,通过控制反应条件可以实现对LSPR的精密调控。该类金/银双金属纳米颗粒可用作为SERS基底,苯硫酚在其表面增强因子可达107,并具有良好的信号重现性。该基底用于atto610标记的生物素与亲和素的SERS检测,检测限可达80 pg/m L。     

正极材料Li（Ni1／3Co1／3-xMn1／3）MxO2（M=Ti，Mg）的合成及性能

采用草酸盐前驱体合成Ti4+、Mg2+掺杂正极材料Li(Ni1/3Co1/3-xMn1/3)MxO2(M=Ti, Mg).利用XRD和SEM对其结构和形貌进行表征,并采用循环伏安、交流阻抗、恒流/恒压充放电测试其电化学性能.结果表明:Ti4+、Mg2+掺杂后晶胞体积增大,大倍率充放电时LiNi1/3Co1/3Mn1/3O2的电化学反应阻抗Rct降低,其大倍率充放电性能得到改善,Ti4+掺杂效果更好;当掺杂量x＝0.025时,材料晶型完整,具有单一的a-NaFeO2层状结构;1C倍率时Li(Ni1/3Co1/3-0.025Mn1/3)Ti0.025O2的第二循环放电容量为143.2 mA-h/g,2C时为128.0 mA-h/g,经100次循环后容量分别为132.5和115.8 mA-h/g,容量保持率为92.53%和90.47%.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

Bi-2212/Ag带材的制备与性能

研究了名义化学成分为Bi2.10Sr1.96Ca1.0Cu2.00Ox的Bi-2212/Ag超导带材的制备和性能,采用X射线衍射技术和扫描电镜技术分析了Bi-2212相的合成过程和Bi-2212/Ag超导带材中超导体的微观组织形貌,在4.2～30K温度范围内测量了Bi-2212/Ag超导带材样品的临界电流密度(Jc),应用背景场的磁场(B)最高达到7T。结果表明,Bi2.10Sr1.96Ca1.0Cu2.00Ox的粉末在空气中多次烧结后,2212相生成量可以达到91.6%;Bi-2212/Ag超导带材中晶粒间有良好的连接性,但微观组织中仍存在大量的缩孔。在磁场高于5T和温度低于20K时,Jc随应用磁场和操作温度升高而缓慢下降,而当磁场小于5T和温度超过20K时,Jc快速下降。通过熔化-慢冷工艺得到的Bi-2212/Ag带材其临界电流密度Jc可达到320A/mm2(4.2K,7T)。     

退火对Co/Cu多层膜微观结构和磁性能的影响

研究了退火对磁控溅射Co/Cu多层膜微观结构和磁性能的影响。用扫描电子显微镜(SEM),透射电子显微镜(TEM)观察了沉积态及在不同温度退火后Co/Cu多层膜表面及截面的显微组织,用能谱仪(EDS)分析了退火后Co/Cu多层膜截面的元素分布,用综合物性测量系统(PPMS)对Co/Cu多层膜的磁滞回线进行了测量。表面显微组织的观察结果表明退火温度低于450℃时,多层膜表面形貌变化不大,均是由细小的晶粒组成。退火温度高于该温度后,随退火温度的升高,晶粒迅速长大。截面显微组织的观察结果和元素分布的测试结果表明,磁控溅射的Co/Cu多层膜内有大量柱状晶,随退火温度升高柱状晶长大。当退火温度达到600℃后,多层膜内的层状结构被破坏。磁滞回线的测量结果表明,退火温度低于400℃时,Co/Cu多层膜的磁性能变化不大,退火温度高于该温度后,随退火温度升高,矫顽力迅速增大。     

Bi-2212/Ag多芯线(带)材的制备

系统研究了Bi-2212导体的成材制备技术,通过优化粉末的热处理制度,获得了主相纯度高、各相分布均匀、粒度适宜和碳含量较低的装管粉末;并采用PIT和部分熔化相结合的线(带)材制备方法成功制备出临界电流密度(Jc)为205kA/cm2(4.2K,19T)的37芯带材和104kA/cm2(4.2K,19T)的37芯线材。