导电浆料用银粉的研究

研究了一种制备光亮片状银粉的新工艺:用添加表面剂的甲醛和苯甲醛混合悬浮液作还原剂,还原碱金属氰化银,获得平均粒径9.6μm的光亮片状银粉;并探讨其还原机理。将还原制备的银粉调成银浆,其性能达到技术指标。     

氯化钠辅助快速合成银纳米线的研究

以硝酸银为银源、乙二醇为还原剂和溶剂、聚乙烯吡咯烷酮为表面活性剂,在氯化钠辅助作用下快速合成了银纳米线。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)与紫外-可见吸收光谱(UV-Vis)等方法对样品进行分析和表征。结果表明:在实验条件下,加入NaCl溶液体积为0.55 mL,反应时间为40 min时可获得较纯的银纳米线。最后,讨论了银纳米线的生长机理。     

单分散近球形和片状金粉的制备及表征

以HAuCl4·4H2O为前驱体,抗坏血酸(VC)为还原剂,线性聚乙烯亚胺(L-PEI)为表面活性剂在水相中制备了单分散的近球形和片状金粉.采用SEM、XRD和激光粒度分析仪对金粉的形貌、粒径、结晶和分散性进行了测试和表征.研究了还原剂和金前驱体的摩尔比、L-PEI浓度、温度及反应溶液的pH对近球形和片状金粉的形貌和粒径大小的影响.给出了制备微米级近球形和片状金粉的反应条件,同时也提出了近球形和片状金粉的成核和晶核生长的可能解释.     

单分散近球形和片状金粉的制备及表征（英文）

以HAuCl_4·4H_2O为前驱体,抗坏血酸(VC)为还原剂,线性聚乙烯亚胺(L-PEI)为表面活性剂在水相中制备了单分散的近球形和片状金粉。采用SEM、XRD和激光粒度分析仪对金粉的形貌、粒径、结晶和分散性进行了测试和表征。研究了还原剂和金前驱体的摩尔比、L-PEI浓度、温度及反应溶液的pH对近球形和片状金粉的形貌和粒径大小的影响。给出了制备微米级近球形和片状金粉的反应条件,同时也提出了近球形和片状金粉的成核和晶核生长的可能解释。     

表面活性剂对超细银粉分散性能的影响

在以抗坏血酸为还原剂、银氨配合物为前驱体、PVP为保护剂及表面活性剂为分散剂的液相化学还原体系中制备超细银粉,研究阳离子、阴离子和非离子表面活性剂在银粉制备过程中的防团聚作用和分散作用,并采用扫描电镜(SEM)和X射线衍射等对还原产物进行形貌观察和结构表征.结果表明:表面活性剂的种类对制各样品的纯度、分散性和颗粒大小有着重要的影响,其中阳离子表面活性剂和阴离子表而活性剂的分散效果不明显,非离子表面活性剂的分散效果最好.对吐温(TW)系列分散剂的研究表明:TW相对分子质量的大小对银粉颗粒的分散效果、形貌和大小也有显著影响;采用TW80分散剂可制备出高分散、窄粒级的超细银粉.     

铝基金属微粉涂层

在保护气氛下制取的片状铝-锌合金金属微粉,与磷酸和其它无机金属盐的水溶液、有机或无机还原剂、以及表面活性剂和添加剂,配成一种水系的金属微粉涂料,涂覆于金属件上,经300℃左右烘烤(20～30)min,自然冷却后形成金属基的涂层。试验发现涂层具有金属光泽,并有较好的附着和耐腐蚀性能。     

SnAg纳米粒子的尺寸控制及其机制（英文）

采用一种改进的化学还原法,在室温下合成Sn3.5Ag(质量分数,%)纳米颗粒。实验所用表面活性剂和还原剂分别为邻啡罗琳和硼氢化钠。X射线衍射分析表明所合成的纳米粒子没有明显的氧化现象。结果表明:在反应物浓度较小时,产生的一次粒子较少,团聚及二次粒子生长程度较小,纳米颗粒的尺寸也随之减小。当以某一合适的速率添加还原剂到前驱体溶液中时,表面活性剂浓度对纳米颗粒尺寸起到控制作用。由于表面活性剂分子可以与纳米团簇之间产生配位作用,因此可以抑制纳米颗粒的长大。表面活性剂与前驱体溶液质量的比值越大,得到的纳米颗粒尺寸越小。     

鞣酸还原法制备多形态纳米银

鞣酸还原AgNO3,得到不同形貌的银纳米结构体。反应物滴加的先后顺序及表面活性剂PVP的加入与否对生成物形貌的影响最大。无表面活性剂PVP加入时,改变鞣酸及银氨配离子的滴加顺序分别生成六边形及少量线状纳米银,平均粒径为55nm。加入表面活性剂PVP,易于生长银纳米线。利用XRD、TEM、FT-IR对其进行性能表征。并对其多形貌产生的原因进行了初步探讨。     

棒状金纳米粒子的制备及其光谱特性

以银离子为辅助粒子,十六烷基三甲基溴化铵(CTAB)为表面活性剂,抗坏血酸为弱还原剂,利用晶种法制备棒状金纳米粒子,着重研究晶种用量与氯金酸量的比例对棒状纳米粒子形状和产率的影响。利用透射电子显微镜（TEM）和X射线衍射（XRD）仪对纳米粒子的形貌及晶体结构进行分析,利用紫外可见光谱（UV-Vis）对产物进行光谱表征。结果表明,纳米棒为面心立方结构,其UV-Vis出现位于530 nm处的短波吸收和970~980 nm的长波吸收,随着晶种与氯金酸用量比例的增加,纳米棒的长径比出现先增大后减小的趋势,并最终形成球形颗粒。最后探讨晶种用量影响金纳米棒生长的机制。     

SnAg纳米粒子的尺寸控制及其机制

采用一种改进的化学还原法,在室温下合成Sn3．5Ag（质量分数,％）纳米颗粒。实验所用表面活性剂和还原剂分别为邻啡罗琳和硼氢化钠。X射线衍射分析表明所合成的纳米粒子没有明显的氧化现象。结果表明：在反应物浓度较小时,产生的一次粒子较少,团聚及二次粒子生长程度较小,纳米颗粒的尺寸也随之减小。当以某一合适的速率添加还原剂到前驱体溶液中时,表面活性剂浓度对纳米颗粒尺寸起到控制作用。由于表面活性剂分子可以与纳米团簇之间产生配位作用,因此可以抑制纳米颗粒的长大。表面活性剂与前驱体溶液质量的比值越大,得到的纳米颗粒尺寸越小。     

Synthesis of Silver Nanoplates without Agitation andSurfactant

在液相体系中成功制备了单分散的银纳米片,反应过程中没有机械搅拌及使用任何表面活性剂,只用硝酸银和维生素C作为原料.相反,使用机械搅拌,获得的产物为银的纳米粒子团聚体.产物的形貌和相结构用扫描电子显微镜(SEM)、透射电子显微镜(TEM0和X射线粉末衍射(XRD)进行了表征.讨论了可能的反应机理,有助于理解化学反应过程中的粒子团聚机理.     

简易种子调停法制备大小可调的三角形银纳米盘(英文)

通过柠檬酸钠还原银离子,以银纳米粒子为种子,在室温下制备出平均厚度约为5nm,尺寸40到500nm可调的三角形银纳米片。通过种子调停法可实现银纳米盘的面内偶极表面等离子体共振峰(SPR)从最初的520nm红移至1100nm。通过控制实验参数能够很好地理解其生长机制。柠檬酸根离子和增加到生长液里面的银纳米种子是2个重要的参数,可以控制银纳米盘的大小却不改变银纳米盘的厚度以及晶面结构。采用PVP作为包覆剂,其作用机理还不是很清楚,需要进一步的研究。     

用苦瓜提取液还原制备纳米银的研究

分别以中国种和印度种苦瓜的提取液为还原剂、硝酸银为前驱体制备纳米银颗粒,并采用紫外可见光谱(UV-Vis)、红外光谱(FTIR)、X射线衍射(XRD)、和透射电镜(TEM)进行表征。结果表明,当硝酸银浓度为10 mmol/L时,制备得到平均粒径最小为8.72和7.46 nm的球形纳米银颗粒。制备反应机理为类黄酮作为还原剂,通过失去H⁺由烯醇结构变为醌型结构来还原Ag⁺获得Ag⁰,蛋白质及其它三萜类化合物起保护剂作用。苦瓜提取液种类对纳米银的粒径、形貌、分散性及均匀性等总体影响不大。     

One-pot synthesis of highly stable silver nanoparticles-conducting polymer nanocomposite and its catalytic application

Herein, we report the preparation of highly stable Ag_nano–PEDOT nanocomposite by one-pot fashion in acidic condition using 3,4-ethylenedioxythiophene (EDOT) as a reductant and polystyrene sulfonate (PSS^?) as a dopant for PEDOT as well as particle stabilizer for silver nanoparticles (AgNPs). The above nanocomposite denoted as Ag_nano–PEDOT/PSS^? nanocomposite. The formation of AgNPs with concomitant EDOT oxidation was followed by UV–visible (UV–vis) spectroscopy at different time intervals. Ag_nano–PEDOT/PSS^? nanocomposite shows absorption bands at 380 and above 700 nm, which correspond to surface plasmon resonance (SPR) peak of AgNPs and oxidized PEDOT, respectively. Ag_nano–PEDOT/PSS^? nanocomposite was characterized by infrared (IR) spectroscopy, transmission electron microscopy (TEM), and XRD. TEM study reveals that AgNPs are distributed uniformly around PEDOT polymer with an average particle size diameter of 10–15 nm. In addition, Ag_nano–PEDOT/PSS^? nanocomposite was tested for the catalytic reduction of 4-nitrophenol. For comparing stability, we were also synthesized AgNPs in the absence of PSS^? (denoted as Ag_nano–PEDOT) using EDOT as reductant. UV–vis spectrum of Ag_nano–PEDOT nanocomposite revealed that AgNPs prepared in the absence of PSS^? was not stable.     

Self-assembled 3-D flower-shaped SnO2 nanostructures with improved electrochemical performance for lithium storage

Flower-shaped SnO₂ nanoplates were successfully synthesized via a simple hydrothermal treatment of a mixture of tin(II) dichloride dihydrate (SnCl₂·2H₂O) and sodium citrate (Na₃C₆H₅O₇·2H₂O) in alkali solution. The obtained SnO₂ nanoplates were less than 5 nm thick and self-assembled into flower-shaped nanostructures. The introduction of citrate was essential for the preparation of the SnO₂ nanoplates. The nanoscale shape and self-assembled architecture of SnO₂ nanoparticles were mainly controlled by the alkalinity of the solution. When the self-assembled SnO₂ nanostructures were used as anode materials in Li-ion batteries, they exhibit a reversible capacity of 670 mA h g^?1 after 30 cycles and an average capacity fading of 0.95% per cycle after the second cycle. The good electrochemical performance of the SnO₂ sample prepared via the hydrothermal synthesis indicates the possibility of fabricating specific self-assembled three-dimensional nanostructures for Li-ion batteries.     

Deposition of Pd on Co(OH)2 nanoplates in stabilizer-free aqueous phase for catalytic reduction of 4-nitrophenol

Palladium-supported cobalt hydroxide (Co(OH)₂-Pd) nanoplates were fabricated in an aqueous solution and employed as a catalyst for the reduction of 4-nitrophenol. For the preparation of Co(OH)₂-Pd, Pd nanoparticles were anchored on the Co(OH)₂ nanoplates after the reduction of Na₂PdCl₄ by ascorbic acid in the absence of a stabilizer at room temperature. The observations under transmission and scanning electron microscopy reveal that Pd nanoparticles with a size of 2–5 nm are uniformly dispersed on the surface of the Co(OH)₂ nanoplates. In catalytic test, the conversion of 4-nitrophenol to 4-aminophenol is completed within 6 min in the presence of Co(OH)₂-Pd(1000) nanoplates with 2.18 at.% Pd, and the corresponding kinetic constant is 0.0089 s^-1 in the first test. The catalyst retains relatively high activity after several cycles. The results demonstrate that the Co(OH)₂-Pd(1000) nanoplates exhibit high catalytic activity toward the reduction of 4-nitrophenol in the presence of NaBH₄.     

Identification and formation of green rust 2 as an atmospheric corrosion product of carbon steel in marine atmospheres

Green rust 2 (GR2(SO^2?₄ )) was detected amongst the products formed on a carbon steel rod exposed to atmospheric corrosion using X‐ray diffraction (XRD). The presence of green rust 2 has been related to sulphate reducing bacteria (SRB) in the sea spray. These were detected using test catch rods made out of inert material and posterior lab identification using Starkey culture. Likewise, after the exposure of said rods to sea environmental conditions, SRBs have been isolated from among the carbon steel corrosion products. The evolution of GR2(SO^2?₄ ) from GR1(SO^2?₄ ) was ruled out due to the tendency of this compund to produce GR2(SO^2?₄ ) in the presence of sulphate ions, as is the case here. Likewise, the evolution from GR1(Cl^?) has also been ruled out since in such case as this compound should be formed (it has not been detected in any of the 39 stations studied), the enormous affinity of the GRs with divalent anions (such as is the case with SO^2?₄ ) as opposed to the monovalent ions (such as is the case of the Cl^?) makes GR1(Cl^?) transform into GR2 (SO^2?₄ ).     

Two step novel chemical synthesis of polypyrrole nanoplates for supercapacitor application

Simple and inexpensive two step novel chemical method for the synthesis of polypyrrole (PPy) nanoplates has been reported. These PPy nanoplates are characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polypyrrole nanoplates exhibit amorphous nature as confirmed from XRD study. Based on SEM and TEM analysis, the formation of the spherical bunches of PPy nanoplates with average size of about 20 nm are inferred. The electrochemical performance of PPy electrode was evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurement. A high specific capacitance of 533 F g⁻¹ was obtained within the potential range of −0.4 to 0.6 V in 0.5 M H₂SO₄ solution. Moreover, PPy electrode exhibited high discharge/charge efficiency of 93% and the capacitance retention of 83% at a current density of 10 mA cm⁻² indicating good electrochemical reversibility and rate capability.     

Kinetics of simultaneous leaching of Ag and Pb from hydrometallurgical zinc residues by chloride

The leaching kinetics of silver and lead simultaneously from zinc residue by chloride was investigated.The effects of stirring speed,temperature,sodium chloride concentration,particle size and liquid/solid ratio on Ag and Pb dissolution in sodium chloride were studied.It was determined that the dissolution rates increased with increasing sodium chloride concentration,temperature and decreasing particle size.The dissolution kinetics followed a shrinking core model,with inter-diffusion through gangue layer as the rate determining step.This finding is in accordance with the apparent activation energy(Ea)of 26.8 kJ.mol-1(Ag)and 26.5 kJ.mo1-1(Pb),and a linear relationship between the rate constant and the reciprocal of squared particle size.The orders of reaction with respect to sodium chloride concentration,temperature and particle size were also achieved.The rate of reaction based on diffusion-controlled process can be expressed by semi-empirical equations.     

Hydrothermal synthesis of silver nanoparticles by sodium alginate and their applications in surface-enhanced Raman scattering and catalysis

Various methods have been reported for the synthesis of Ag nanoparticles (NPs) by reduction of AgNO₃ with a chemical reducing agent. However, many of them pose potential environmental and biological risks. Herein, we demonstrate for the first time that Ag NPs can be synthesized using sodium alginate (NaAlg) as both reducing and stabilizing agents by a simple and effective green hydrothermal strategy. By controlling the temperature and time of reaction, Ag nanospheres and nanoplates can be fabricated. Moreover, the application of an Ag NPs–NaAlg thin film in surface-enhanced Raman scattering of rhodamine 6G is demonstrated. The catalytic efficiency of the as-prepared Ag NPs embedded in calcium alginate beads is evaluated for reaction of 4-nitrophenol reduction to 4-aminophenol in the presence of NaBH₄.