金属钴超细粉的化学镀合成及其微波性能研究

以CoSO_4·7H_2O、NaH_2PO_2 H_2O等为原料,在[Co~(2+)]=0．30 mol/L,[Co~(2+)]：[NaH_2PO_2·H_2O]=1：8(摩尔比),pH=9．8,T=90℃,[Co~(2+)]：[Na_3Cit]=2：1(摩尔比),DBS用量为0．5%(质量分数)的条件下,采用化学镀工艺制备了金属钴超细粉体。采用XRD、SEM对其相成分、显微结构进行了研究。采用波导法,对超细钴粉的复介电常数、复磁导率在8．2～12．4GHz下的变化规律进行了研究。结果表明,金属钴超细粉体的粒径在0．5～1．0μm左右,呈片状和圆球状。所制备金属钴粉的介电损耗值较小,在0左右波动,其磁损耗在1．3左右变化。     

氢气还原法制备LiFePO_4及其电化学性能的研究

在溶液中制备FePO_4·2H_2O前驱体,利用氢气还原法于650℃制得了锂离子电池正极材料LiFePO_4,并对其进行了包覆和掺杂.采用X射线衍射法(XRD)、扫描电镜法(SEM)、循环伏安法(C-V)、交流阻抗法(EIS)及充放电测试对材料进行了结构表征和电化学性能测试.结果表明,该方法制得的材料具有单一的橄榄石结构,样品形貌规则、颗粒均匀.包覆碳和掺镁后,材料具有较低的阻抗及较高的首次放电比容量,LiFePO_4、LiFePO_4/C、LiMg_(0.01)Fe_(0.99)PO_4/C的首次放电比容量分别为125.09mA·h/g、139.17mA·h/g、146.97mA·h/g.     

锂离子电池正极材料LiFe_(1-2x)Mn_xMg_xPO_4/C的电化学性能研究

通过高温固相合成法以MnCO3为锰源、(MgCO3)4·Mg(OH)·5H2O为镁源,葡萄糖为碳源,在氩气气氛下合成二元掺杂Mn、Mg的LiFe0.8Mn0.1Mg0.1PO4/C和LiFePO4/C正极材料,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱仪(FT-IR)进行结构表征,通过恒电流充放电实验研究了LiFe0.8Mn0.1Mg0.1PO4/C和LiFePO4/C电化学性能。结果表明,二元掺杂Mn、Mg的LiFe0.8Mn0.1Mg0.1PO4/C呈现橄榄石结构,无杂质产生。与未掺杂的LiFePO4/C相比,掺杂后LiFe0.8Mn0.1Mg0.1PO4/C提高了电导率,0.1C倍率下放电可逆容量为131mAh/g,表现出良好的电化学性能。     

可膨胀石墨的制备及谱学特性研究

采用化学氧化法,以石墨粉(≤30μm)为原料,硫酸与高锰酸钾为氧化剂,以及磷酸为辅助插层剂制备出具有高膨胀体积的可膨胀石墨(EG)。通过XRD、Raman、SEM、EDS、FT-IR以及TG-DTA等测试手段对材料的微观结构、形貌、谱学特性及热稳定性进行表征分析。实验结果表明,当硫酸与磷酸体积比为2∶1时,EG氧化-插层效果最好,在400℃时膨胀体积达102ml/g。同时EG片层中含有P、S、Mn等元素,表明可能插入了磷酸、硫酸以及Mn的磷酸二氢盐、硫酸盐等物质。TG-DTA显示,EG的起始膨胀温度在160℃左右,且石墨在氧化-插层后,有序结构没有被完全破坏,部分石墨仍具有很好的耐热氧性。另外,探讨了EG可能的形成及膨胀机理。     

磷酸盐溶液中碳纤维表面电化学改性

对比研究(NH₄)₂HPO₄和NH₄H₂PO₄两种不同电解质对碳纤维电化学改性效果的影响。通过拉丁方试验,研究了各改性参数对纤维表面改性效果的影响程度,采用XPS、AFM、BET技术对纤维表面化学组成、形貌及其比表面积的变化进行了表征分析。结果表明:以(NH₄)₂HPO₄为电解质处理时改性效果主要受相对电流密度的影响,而以NH₄H₂PO₄为电解质时电解液浓度是最主要的影响因素;在(NH₄)₂HPO₄电解液中,纤维表面氧化刻蚀温和,改性效果显著,层间剪切强度可提高到79.8MPa,而在NH₄H₂PO₄电解液中,纤维表面受到较强烈氧化刻蚀,本体强度损失较大,复合材料层间剪切强度仅能提高到70.8MPa。      

铜掺杂钴氧化物CuxCo3-xO4的制备及其电化学电容性能

采用X射线衍射(XRD)、场发射扫描电镜(FESEM)对铜掺杂钴氧化物(CuxCo3-xO4)纳米粒子样品的结构和形貌进行了表征;用循环伏安,恒流充放电,交流阻抗等电化学方法对其电化学性能进行了测试。结果表明:钴和铜的摩尔比对目标产物的电化学性能有显著的影响,当钴和铜的摩尔比为2.67∶0.33时,样品的电化学性能最佳。在电流密度为1A/g时,比电容达到492F/g,且在3A/g的电流密度下,经过2000次充放电循环后,其比电容值没有衰减,表明Cu0.33Co2.67O4是一种良好的超级电容器电极材料。     

不同电解液组成对TiO2纳米管形成的影响

电解液在阳极氧化中发挥着重要作用,对TiO2纳米管的形成与否,形成后管的成分、形貌都有着很大的影响.本实验采用了恒压阳极氧化方式,分别以HF(0.5wt%),(NH4)2SO4 HF(0.5wt%),(NH4)H2PO4 HF(0.5wt%),NaNO3 HF(0.5wt%)为电解液,在钛箔表面获得多孔TiO2膜.用FESEM观察了多孔膜的形貌并用EDX和XPS能谱对膜表面成分和构成进行测试分析.实验结果表明:在单一的HF酸电解液中加入(NH4)2SO4或(NH4)H2PO4后,阳极氧化生成的膜孔径明显减小,并且膜表面形态较差.加入NaNO3后,对膜的形貌影响不是很大.由EDX和XPS能谱分析得出,阴离子中的大部分非金属元素较难进入膜表面,而氮元素却很容易掺杂进入膜的表面形成N-Ti-O结构,从而影响膜的成分构成.这表明本实验利用简单电化学方法实现了N的掺杂.通过XRD测试得出,含不同阴离子的电解液对TiO2膜的晶型转变温度影响不大.     

溶胶机械活化及其溶剂对LiFePO4/C结构和电化学性能的影响

本文在溶胶凝胶法制备碳包覆LiFePO4/C锂离子电池正极材料的基础上,对溶胶进行机械球磨活化以进一步优化LiFePO4/C复合材料的结构和形貌,并通过原位引入Fe2P等方法,提高其高倍率性能。采用XRD、SEM、元素分析等材料结构测试分析方法和恒电流充放电及电化学阻抗谱电化学测试技术,对溶胶机械活化及不同溶胶溶剂对LiFePO4/C材料结构和电化学性能的影响进行了研究。研究结果表明,机械活化能有效减小LiFePO4/C颗粒的尺寸及改善其分散性,并能改变Fe2P相的含量。溶胶机械活化处理后的LiFePO4/C在不同倍率下的放电容量明显增加。相对于蒸馏水,乙醇作为溶胶溶剂获得的LiFePO4/C材料具有更好的倍率性能,其在1C和10C的容量分别达到136mAh/g和90mAh/g。     

无模板剂水热合成Bi12O17Cl2纳米带及其阻燃性能研究

以β-Bi2O3为原料,采用无模板剂水热法制备了Bi_(12)O_(17)Cl_2纳米带,利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和高分辨透射电镜(HRTEM)对其形貌和结构进行了表征并作为阻燃剂添加到聚氯乙烯(PVC)中评价其阻燃性能。结果表明,适宜的Bi/Cl物质的量比对水热合成Bi_(12)O_(17)Cl_2纳米带及其化学计量比影响显著,当Bi/Cl物质的量比为1∶2.5时,可得到分散性好、形貌均匀的Bi_(12)O_(17)Cl_2纳米带;改变Bi/Cl物质的量比,纳米带中Bi/Cl化学计量比从6∶1变成2.4∶1。初步探讨了Bi_(12)O_(17)Cl_2纳米带可能的生长机理,在水热反应过程中,Bi 3+与Cl-发生络合反应形成BiCln3-n络合物,从而合成Bi_(12)O_(17)Cl_2纳米带。     

Large-scale synthesis of single crystal silver nanowires by a sodium diphenylamine sulfonate reduction process

Silver nanowires with high aspect ratios of up to more than 60 were synthesized on a large scale by the redox reaction between silver nitrate and sodium diphenylamine sulfonate at room temperature and in the absence of surfactant and hard-template and seed. When the molar ratio of reductant sodium diphenylamine sulfonate and silver nitrate < or =1, most products were all the nanowires. When the molar ratio increases to 2:1, silver nanowires and nanobelts were concomitantly formed. The redox product N, N'-diphenylbenzidinedisulfonate and sodium diphenylamine sulfonate all play an important role in the formation of silver nanostructures. The structure, morphology, and composition of the silver nanowires were characterized by the X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive microanalysis (EDX), and UV-Vis spectroscopy respectively. High-resolution transmission microscopy (HRTEM) and selected area electron diffraction (SAED) reveal the single-crystal nature of the silver nanowires.     

Characterization of nanoparticles of LiMn2O4 synthesized by a one-step intermediate-temperature solid-state reaction

Nanoparticles of lithium manganese oxide (LiMn2O4) with a spinel structure have been synthesized by a one-step intermediate temperature solid-state reaction. The influence of the molar ratio of citric acid to the metal ions on the physicochemical properties of LiMn2O4 powders in air has been analyzed by means of X-ray diffraction and electron microscope techniques. The electrochemical behavior of the material has been examined by charge/discharge tests and cyclic voltammetry. Test results reveal that LiMn2O4 particles with lower molar ratios of citric acid to metal ions (1:2) are highly crystalline and highly electrochemically reversible, with better cycle capabilities when compared with a sample with a higher molar ratio (2:1). The LiMn2O4 powders obtained by this method have a uniform morphology with a narrow size distribution.     

Novel petal-like ZnO crystal synthesized by organic solution method

ZnO crystals with different morphologies have been synthesized by an organic solution method using Zn(CH₃COO)₂ · 2H₂O and polyvinylpyrrolidone as precursors. X-ray powder diffraction, field emission scanning electron microscopy and transition electron microscopy were used to characterize the obtained samples. The results showed that novel petal-like ZnO particles could be obtained when the molar ratio of Zn²⁺/C = O was 1 : 4. The particle had uniform diameter in 200–300 nm and with good dispersibility. Otherwise, octahedron shaped particles with sub-crystalline were achieved when the molar ratio of Zn²⁺ to the carbonyl group of polyvinylpyrrolidone was 1 : 2 or 1 : 8.     

二次锂电池NiS正极材料的制备及性能研究

以NiCl2.6H2O和硫代乙酰胺(TAA)为反应物,通过化学合成法成功制备了NiS正极材料。采用XRD和SEM对材料进行了表征。结果显示,合成的材料颗粒均匀,分散度高。通过充放电测试及循环伏安测试表征其电化学性能。在电流密度为0.1mA.cm-2,充放电区间1.0~3.5V时,该材料首次放电比容量为554mAh.g-1。     

Preparation of helical mesoporous ethylene-silica nanofibers using CTAB and (S)-2-methyl-1-butanol

The morphology and pore architecture of mesoporous ethylene-silicas were controlled using cetyltrimethylammonium bromide (CTAB) as the template and (S)-2-methyl-1-butanol (MB) as a co-structure-directing agent. X-ray diffraction, nitrogen sorption, field emission scanning electron microscopy and transmission electron microscopy techniques have been used to characterize the ethylene-silicas. When the MB/CTAB molar ratio is 20, mesoporous nanoparticles with lamellar mesopores on their surfaces were identified. Helical nanofibers were obtained at the MB/CTAB molar ratios of 0.5-10. Although MB could not drive the formation of single-handed helical nanofibers, with increasing the MB/CTAB molar ratio, the diameter and the helical pitch of the mesoporous ethylene-silica nanofibers decreased and the pore size increased.     

Utilization of strontium added NiAl(2)O(4) composites for the detection of methanol vapors

Strontium added NiAl(2)O(4) composites prepared by sol-gel technique was utilized for the detection of methanol vapors. X-ray diffraction, scanning electron microscopy (SEM), FT-IR spectroscopy and nitrogen adsorption/desorption isotherm at 77K was employed respectively to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the composites. The composites were prepared with the molar ratios of Ni:Sr as (1.0:0.0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, 0.0:1.0) keeping the aluminum molar ratio as constant for all the compositions and were labeled as NiSA1, NiSA2, NiSA3, NiSA4, NiSA5 and NiSA6, respectively. The samples sintered at 900 degrees C for 5 h were subjected to dc resistance measurements in the temperature range of 30-250 degrees C to study the methanol vapor detection characteristics. The results revealed that the sensitivity in detecting methanol vapor increased with increase in temperature up to 175 degrees C for the composites NiSA1 and NiSA6 while for the other composites up to 150 degrees C and thereafter decreased. The sensitivity increased with increase in methanol concentration from 100 to 5000 ppm at 150 degrees C. Among the different composites NiSA5 showed the best sensitivity to methanol detection at an operating temperature of 150 degrees C.     

Enhanced cycling performance of nanocrystalline Fe3O4/C as anode material for lithium-ion batteries

Fe3O4-carbon composite was prepared by the sol-gel method. The crystal structure, morphology, and phases present in the product were investigated by X-ray diffraction and by scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy and field-emission SEM. Electrochemical characterization was performed using constant current charge-discharge testing and electrochemical impedance spectroscopy. The Fe3O4/C electrode has high initial columbic efficiency (87%) and outstanding cycling performance (775.3 mAh g(-1) after 90 cycles at a current density of 100 mA g(-1)).     

掺杂对LiFePO_4电化学性能的影响

用水热法制备LiFe_(0.95)M_(0.05)PO_4(M=Mg,Ni,Co),研究了掺杂对材料电化学性能的影响.结果表明,液相Fe位掺杂合成的LiFe_(0.95)M_(0.05)PO_4具有纯相橄榄石结构、结晶良好、粒径均匀;Fe位掺杂可增强材料的可逆性和导电性,提高其1C倍率下的电化学容量和循环稳定性;LiFe_(0.95)Mg_(0.05)PO_4,LiFe_(0.95)Ni_(0.05)PO_4和LiFe_(0.95)Co_(0.05)PO_4三种材料的1C倍率首次放电比容量分别为133.1 mAh·g~(-1),128.4 mAh·g~(-1)和135.2 mAh·g~(-1);三种掺杂离子中Co~(2+)掺杂的效果最好,0.1C和1C倍率放电循环30次后的容量衰减率仅为5.7%和9.5%.     

纳米Li2MnSiO4正极材料的高压水热法制备及其电化学特性

采用高压水热法制备锂离子电池正极材料Li 2MnSiO 4,研究压强、反应温度和前驱体浓度对合成Li 2MnSiO 4的影响,并进一步研究碳包覆前后Li 2MnSiO 4的电化学性能。通过X射线衍射、扫描电镜、透射电镜、充放电测试和交流阻抗等方法对样品的结构、形貌和电化学性能进行表征分析。结果表明:采用水热法在高压高温条件下可以合成高纯度的Li 2MnSiO 4材料,提高前驱体浓度有助于形成粒径较小的Li 2MnSiO 4纳米颗粒。电化学性能测试显示碳包覆后的 Li 2MnSiO 4/C比Li 2MnSiO 4具有更高的比容量,在0.1C (电流密度为33.3mA·g -1 )下首次放电比容量可达178.6mAh·g -1 ,循环50次后放电比容量为97.1mAh·g -1 ,容量保持率为54.4%。同时,Li 2MnSiO 4/C还具有比Li 2MnSiO 4更小的电荷转移阻抗和更高的锂离子扩散系数。     

Synthesis and microwave absorption properties of magnetite nanoparticles

Nanoparticles of Fe3O4 with various sizes were synthesized from FeCl3 x 6H2O, FeCl2 x 4H2O and NaOH by coprecipitation process. The crystal structure, morphology, particle size and magnetic property of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). It was found that the molar ratio of ferrous to ferric played an important role in the formation of Fe3O4 nanoparticles. The particle mean diameter swelled from approximately 10 to approximately 20 nm with the molar ratio range from 1:2 to 6:1. The saturation magnetization and the coercivity increased correspondingly. The complex permittivity epsilon(r) and permeability mu(r) of the Fe3O4 mixture with paraffin were measured using vector network analysis. Values of epsilon(r), and mu(r) were used to determine the reflection loss at various sample thicknesses, based on a model of microwave absorbing layer backed by a metal plate. The minimal reflection loss or the dip shifts to a lower frequency region with increasing thickness. When the thickness is 5 mm, the minimal reflection loss of Fe3O4 synthesized with the molar ratio of 6:1 and paraffin wax composites reaches -35.1 dB at 5.2 GHz and -30.2 dB at 17.6 GHz, respectively. The minimal reflection loss is attributed to the thickness of the absorber approximates an odd number multiple of a quarter of the propagation wavelength.     

Capacitive characteristics of Ni–Co oxide nano-composite via coordination homogeneous co-precipitation method

A series of Ni–Co oxide nano-composites were prepared by thermal decomposition of the precursors obtained via coordination homogeneous co-precipitation method. Thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and transition electron microscopy (TEM) tests were applied to investigate the thermal behavior, crystalline. and morphology of the Ni–Co oxide composites. The electrochemical properties of Ni–Co oxide electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance measurements. Results showed that the calcination temperature had great effect on morphology and specific capacitance of product. The effect of the molar ratios of Ni²⁺/Co²⁺ in the reaction system on the electrochemical properties of Ni–Co oxide electrodes was also discussed.