两步还原法制备MLCC电极用超细铜粉

为了制备MLCC电极用超细铜粉,克服CuSO4直接水合肼还原法制备的铜粉存在粒度分布不均匀、振实密度小的问题,提出了两步液相还原新工艺,即以CuSO4溶液为原料,首先采用NaOH沉淀-葡萄糖预还原制备Cu2O,然后用水合肼还原Cu2O制备超细铜粉.针对实现铜晶体的成核与长大过程的分离,研究了水合肼加入方式对铜粉性能的影响,发现较慢的水合肼滴加速度和将水合肼还原Cu2O阶段分为升温均匀成核与水合肼连续滴加长大两个过程有利于得到粒度均匀的铜粉.在最佳试验条件下制得的铜粉呈类球形,粒度分布均匀,分散性好,平均粒径为1.8μm,振实密度达4.2g/ml.     

化学还原法制备超细铜粉工艺及机理研究

为了提高超细铜粉分散性、均匀性及抗氧化性,采用几种化学还原法工艺分别制备了铜粉,通过反应现象探讨了温度、还原剂、添加剂及葡萄糖预还原对铜粉性能的影响,利用SEM、粒度仪对铜粉形貌、粒径进行观察,并进行相关机理分析,确定了化学还原法制备超细铜粉的最佳工艺,结果表明,在温度为70℃时,添加分散剂PVP和抗氧化剂BTA,以甲醛-水合肼为复合还原剂,结合葡萄糖预还原法制备的铜粉具有抗氧化性强、粒径分布区间窄、几乎无团聚等优点。此工艺不仅体现了葡萄糖预还原的有利影响,还明显克服了单一还原剂的缺陷,所制铜粉质量好,具有良好的应用前景。     

超细球形铜粉的制备

研究了一种新颖的球形铜粉制备方法,即先用葡萄糖还原法制备球形超细Cu2O粉末,然后用氢气还原Cu2O粉末制备球形铜粉.用葡萄糖还原Cu(Ⅱ)可以制备球形的Cu2O粒子.在240℃下用氢气还原球形Cu2O粉末,得到了分散性良好的球形铜粉,铜粉具有良好的导电性和稳定性.铜粉粒径大小和粒径分布取决于前驱体Cu2O粒子的大小和粒径分布.还原后的粉末粒径略有收缩,平均粒径为1.18μm,振实密度为2.1g/ml.     

微混效应对化学法制备超细铜粉的影响分析

采用化学还原法制备了粒度在200nm左右、形貌均匀的球形超细铜粉.研究结果表明,将硫酸铜滴加到水合肼和PVP的混合溶液中,形成的溶液体系局部过饱和度高,化学反应速率和形核速率都非常快,在极短时间内可形成大量的铜晶核.高速搅拌时,溶液体系的微混状况良好,在剪切搅拌抑制机制与断裂破碎机制的作用下会生成粒度较小、形貌均一的铜粉颗粒;低的搅拌速度下,微混作用较弱,PVP分子在铜晶核表面产生不完全吸附,导致铜晶核的二次成核和定向生长,生成长方体的条形颗粒.     

超细球形铜粉的制备工艺研究

以水合肼为还原剂,采用液相化学法对超细铜粉的制备工艺进行了研究。结果表明,直接还原Cu2O获得的铜粉粒度分布很不均匀,抗氧化性能差。在添加微量亚铁氰化钾和2,2’-联吡啶后,铜粉的形貌、粒度分布以及抗氧化性能得到很大改善。经两步还原硫酸铜可制备平均粒度0.5μm以下且分布范围窄的近球形铜粉,热分析表明,该粉末在空气中120℃以下无氧化。     

超细银粉的制备及其粒径表征的研究

本文采用以PVP(聚乙烯吡咯烷酮)为分散剂和保护剂,TW80(吐温80)为表面活性剂,用抗坏血酸还原银氨溶液制备超细银粉。通过调节银氨溶液的浓度、PVP、TW80、抗坏血酸的加入量和滴加速度,设计正交实验,制备不同粒径的超细银粉,找出控制粒径的关键因素和粒径最小的优化条件。实验结果表明银离子浓度为0.125mol/L,TW80与硝酸银的重量比为1:1,抗坏血酸与硝酸银的重量比为1:2,滴加速度为1.25ml/min,PVP与硝酸银的重量比为1:1.5时得到的银粉的粒径最小。通过所制得的银粉,利用马尔文粒度仪测试银粉的平均粒径。通过改变超声波的强度、表面活性剂的加入量、泵速和超声时间得到一套较为准确的表征方案即超声波强度为20W/cm2,外置超声时间3min,内置超声时间3min,每次加入表面活性剂量为3滴,泵速为2650r/min。并用该方案对银粉的粒径进行表征,同时样品进行了透射电镜表征。结果表明所制得的银粉的形貌为球形或类球形,一次粒径约为100nm。     

超声辅助化学还原法制备抗氧化超细铜粉

以三乙醇胺铜配合物为铜源,铝粉为还原剂,采用超声辅助化学还原法制备抗氧化超细铜粉,研究表面活性剂、超声场及温度对铜粉形貌及粒径的影响,通过X射线衍射、扫描电镜、红外光谱以及热分析对铜粉的物相、形貌、表面包覆情况及铜粉的氧化过程进行表征,并结合对铜粉电阻的测量来表征铜粉的抗氧化性。结果表明,在40℃超声场作用下,使用十六烷基三甲基溴化铵为表面活性剂制得的超细铜粉分散性较好,抗氧化能力较强。     

水合肼还原法制备球形钴粉

以水合肼为还原剂,在碱性条件下室温还原六水合硝酸钴(Co(NO3)2·6H2O)制备钴粉.探究了NaOH加入量对钴粉晶体结构的影响,以及NaOH加入量和3种不同的钴离子溶剂对形貌的影响.结果表明:在实验浓度范围内,所制备钴粉样品中fcc相的百分含量随着NaOH量的增加而呈不断增大的趋势;NaOH量较低时,钴粉为表面光滑的球形颗粒,随着NaOH量的增加,颗粒偏离球形,表面变粗糙,而当NaOH量较大时,颗粒形状变得不规则,且尺寸变小;以乙二醇为钴离子溶剂可制得表面光滑的完整球形钴粉颗粒.     

化学镀法制备核壳型银-铜双金属粉

为改善超细铜粉的高温抗氧化性能,通过热力学数据理论上分析了液相还原反应取代置换反应的可行性,并以水合肼作还原剂,银以稳定性适中的银氨络合物存在,采用化学镀法制备银包覆超细铜粉的新技术,利用SEM、XRD等手段对双金属粉的形貌和晶相组成进行了分析.研究表明,一次包覆铜粉基体表面银的包覆率为40.22%,二次包覆银的包覆率可达94.98%,在铜粉表面形成了连续的银膜,可以认为是表面包覆结构,拓展了超细铜粉的应用领域.     

改性的沉淀法制备三氧化二钇粉体

以Y（NO3）3和NH4HCO3为原料,添加适量的表面活性剂（聚乙烯醇）和（NH4）2SO4,利用改性的沉淀法制备了Y2O3前驱体。对前驱体在不同温度下进行焙烧,成功制备了超细Y2O3纳米粉体。分别采用XRD、TEM和TG—DTA分析了不同温度下煅烧所得粉体的物相、形貌以及前驱体热分解特性。结果表明,前驱体在900℃下保温1．5h,得到的Y2O3粉体颗粒近球形,细小均匀,平均尺寸约为7nm,粒径分布极窄,并具有很好的分散性和流动性。     

非晶合金颗粒／树脂基复合材料的耐蚀性

采用内旋转溶液法制备非晶态Fe_(76)Cr_4P_(13)C_7合金粉末,在其中加入适量的合成树脂,压制成形,制备非晶合金颗粒/树脂基复合材料。研究了复合材料在1N H_2SO_4,1N HCl,1N H_2SO_4+0.5N NaCl,1N NaOH和3.5％NaCl溶液中的耐蚀性。实验结果表明:复合材料在试验介质中具有优异的耐蚀性。在非晶态合金粉末中加入合成树脂,压制成形,可以获得耐蚀的块体材料,具有工业应用价值。     

PVP对溶胶凝胶法制备负热膨胀ZrW_2O_8粉体形貌及性能的影响

以PVP为添加剂,采用溶胶凝胶法制备ZrW_2O_8粉体,研究添加剂对粉体形貌的影响及其负热膨胀特性。对其前驱体进行热重-差热分析(TG-DSC),以X射线粉末衍射(XRD),扫描电子显微镜(SEM)对产物结构及形貌进行表征。结果表明所得粉体为单一立方α-ZrW_2O_8相。加入PVP后,可以有效地改变粉体的形貌,随着加入量的增大,粉体的形貌从无规则的团聚体转变为长棒状、扇形及短棒颗粒。原位X射线粉末衍射分析表明,所得ZrW_2O_8粉体具有良好的负热膨胀特性。     

Leaching copper from shredded particles of waste printed circuit boards

Leaching copper from shredded particles of waste printed circuit boards (PCBs) was carried out in sulfuric acid solution using hydrogen peroxide as an oxidant at room temperature. The influence of system variables on copper recovery by leaching was investigated, such as sulfuric concentration, amount of hydrogen peroxide addition, waste PBCs particle size, presence of cupric ion, temperature and time. The results shown that the optimum addition amount was 100mL 15 (wt%) sulfuric acid solution and 10 mL of 30% hydrogen peroxide for leaching 10 g waste PCBs powder with a solid/liquid ratio of 1/10 for 3h at room temperature (～23 °C). Moreover leaching temperature and initial copper ion concentration had insignificant effect on the leaching recovery of copper. The effect of different particle size of shredded waste PCBs on leaching of copper was investigated under the optimum leaching condition. The results revealed that shredding pieces of waste PCBs smaller than 1mm was efficient and suitable for copper leaching. Then the leaching solution was concentrated to crystallize CuSO(4)·5H(2)O, and crystal liquor was reused for the next cycles.     

聚甲基丙烯酸甲酯掺杂剂对7,7,8,8-四氰基苯醌二甲烷薄膜特性的影响

采用旋涂法制备了7,7,8,8-四氰基苯醌二甲烷(TCNQ)及聚甲基丙烯酸甲酯(PMMA)掺杂后的TCNQ敏感薄膜,探讨了PMMA掺杂剂及不同转速对薄膜性能的影响.结果表明,TCNQ/PMMA复合薄膜中TCNQ颗粒变得更细小和均匀,但对NH3的响应不稳定;纯TCNQ薄膜对NH3具有相当高的灵敏度,但响应和恢复时间较长.     

Synthesis and characterization of micrometer Cu/PVP architectures

Micrometer-sized flower-like Cu/polyvinylpyrrolidone (PVP) architectures are synthesized by the reduction of copper (II) salt with hydrazine hydrate in aqueous solution in the presence of PVP capping agent. The resulting Cu/PVP architectures are investigated by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The Cu/PVP flowers have uniform morphologies with an average diameter of 10 μm, made of several intercrossing plates. The formation of Cu/PVP flowers is a new kinetic control process, and the factors such as the amount of N₂H₄H₂O, reaction temperature, molar ratio of CuCl₂ to PVP and molecular weight of PVP have significant effect on the morphology of Cu/PVP architectures. A possible mechanism of the formation of micrometer Cu/PVP architectures was discussed.     

纳米铜微波法的制备及其粒度影响因素的探究

在MCR-3型微波反应器中以CuCl_2·2H_2O为原料,乙二醇为溶剂、还原剂以及分散剂,在碱性条件下,制备了不同粒径的纳米铜粉。考察了CuCl_2的浓度C(CuCl_2)、预置温度T、摩尔比m=n(NaOH)/n(CuCl_2)以及反应时间t对纳米铜粉粒度的影响,并对其影响机理进行了分析。结果表明,采用微波法,通过改变实验条件可以制备出粒度可控的纳米铜,且分散度好,分布均匀,结晶度高,球形性良好;预置温度是影响粒径的主要因素,低于185℃时,粒度依赖性不明显;而当高于185℃时,温度越高,粒径越大。     

微波辅助PVP溶液聚合法制备LSGM电解质粉末

采用了一种全新的化学方法(PVP溶液聚合法)成功制备出了La0.8Sr0.2Ga0.83Mg0.17O2.815粉末;研究了不同含量聚合载体(PVP)对结果的影响规律,找到了能保证金属离子在聚合网状结构中均匀分布并防止偏析的最佳的PVP含量;探索了所制备产物在不同温度下的烧结行为.与传统的Pechini法相比,本实验所需有机物聚合载体(PVP)的量更少,这也证明PVP可以作为一种制备LSGM粉末更为有效的载体.而微波具有更高的加热速率,加热时反应体系中不会存在温度梯度,使得反应更加均匀,制备的粉末杂质更少,压片烧结后其晶粒尺寸也更小(2～3μm).     

Role of Base Plate Rotational Speed in Controlling Spheroid Size Distribution and Minimizing Oversize Particle Formation During Spheroid Production by Rotary Processing

The occurrence of material adhesion and formation of oversize particles in the product yield during one-pot spheroid production by rotary processing leads to a less predictable process and a decrease in the usable portion of the total product yield obtained from each production run. The use of variable speeds of the rotating frictional base plate during the spheronization run was investigated for achieving optimal spheroid production. When the base plate speed was increased during liquid addition, the greater centrifugal forces generated improved liquid distribution and the mixing of the moist powder mass, resulting in a decrease in the amount of oversize particles formed. When the base plate was maintained at a high speed throughout the run, the amount of oversize particles and mean spheroid size increased, and a greater “between batch” mean spheroid size variability was also observed. The findings showed that, when higher speeds were used, the residence time must be adjusted accordingly to avoid excessive coalescence and growth while maintaining even liquid distribution. A “low-high-low” speed variation during rotary processing may be used to produce spheroids with a narrow size distribution and with a minimal amount of oversize particles in the total product yield.     

Role of base plate rotational speed in controlling spheroid size distribution and minimizing oversize particle formation during spheroid production by rotary processing

The occurrence of material adhesion and formation of oversize particles in the product yield during one-pot spheroid production by rotary processing leads to a less predictable process and a decrease in the usable portion of the total product yield obtained from each production run. The use of variable speeds of the rotating frictional base plate during the spheronization run was investigated for achieving optimal spheroid production. When the base plate speed was increased during liquid addition, the greater centrifugal forces generated improved liquid distribution and the mixing of the moist powder mass, resulting in a decrease in the amount of oversize particles formed. When the base plate was maintained at a high speed throughout the run, the amount of oversize particles and mean spheroid size increased, and a greater “between batch” mean spheroid size variability was also observed. The findings showed that, when higher speeds were used, the residence time must be adjusted accordingly to avoid excessive coalescence and growth while maintaining even liquid distribution. A “low-high-low” speed variation during rotary processing may be used to produce spheroids with a narrow size distribution and with a minimal amount of oversize particles in the total product yield.