水热法制备均分散α-Fe2O3纳米粒子

系统地研究了以Fe(NO3)3为原料,水热合成α-Fe2O3纳米粒子时,前驱物pH值对产物形貌的控制作用.实验结果显示,以Fe(NO3)3为前驱物直接进行水热处理,所得产物形貌为片状;如果Fe(NO3)3溶液用氨水中和形成Fe(OH)3凝胶后,再调节不同的pH值作前驱物,经水热处理所得产物均为单晶粒子,且在不同的pH值下,粒子形貌明显不同:当pH为1时为菱形粒子;pH为3,5时粒子形貌为近球形多孔结构;pH为7时为菱形粒子;pH为9时粒子形貌为近球形、无孔结构.同时分析了在水热条件下前驱物pH值对产物粒径的影响,另外还讨论了反应体系中存在的电解质对α-Fe2O3生成速率的影响机理.     

异形纳米AlOOH颗粒在水热体系中的结晶生长过程

构建了水热体系中AlOOH的结晶生长过程模型,首次从生长基元的角度研究了晶体结晶过程,深入原子层面揭示异形纳米AlOOH最终形貌形成的成因,从本质上解释水热环境pH值对结晶过程及最终形貌的影响机理,重点分析了不同pH条件下AlOOH的Al3+聚集体形态. 根据[Al3(OH)4(OH2)9]5+及[Al3(OH)5(OH2)8]4+, [Al3(OH)6(OH2)7]3+ 等的配位特点,揭示了AlOOH定向生长为一维晶须和二维片状或三维颗粒的本质. 用实验样品的形貌图像直接验证了所建模型的合理性,并用X射线衍射和红外光谱检测印证了不同pH条件下的聚集体形态及生长基元模型的正确性.     

层状溶致液晶中纳米羟基磷灰石的合成

在一定的pH值条件下,将Ca(NO3)2和(NH4)2HPO4分别溶于C34H62O11(聚乙二醇辛基苯基醚)/C8H17OH/H2O体系层状溶致液晶溶剂层中,混合并经陈化即可在溶剂层中生成具有一定微观形貌的羟基磷灰石纳米粒子(HA),其直径可以达到10 nm,长度在100 nm以下.产物在不同温度下焙烧,分别用FTIR,XRD和TEM等对产物的结构及形貌进行分析表征.对不同反应物浓度条件下所得HA的微观形貌进行分析对比,并提出了改善团聚的有效措施.     

不同晶型纳米二氧化钛的水热合成

水热法合成了不同晶型、形貌和大小的纳米二氧化钛。利用X射线衍射(XRD)和透射电镜(TEM)对所得的样品进行了表征。研究了pH值、水热反应温度和水热反应时间对纳米二氧化钛晶型、形貌和晶粒尺寸的影响。结果表明,前驱体pH值是决定产品晶型、晶粒尺寸和形貌的主要因素。随着水热反应温度的升高,纳米二氧化钛的晶粒尺寸逐渐变大,但pH=3.0时所形成的锐钛矿型纳米二氧化钛的晶粒尺寸却几乎不变;随着水热反应时间的延长,金红石型纳米二氧化钛晶粒的生长速度最快,而锐钛矿型的纳米二氧化钛的晶粒生长速度则最慢。     

非晶态Ni(OH)2电极材料的制备工艺

采用微乳液快速冷冻沉淀法制备非晶态Ni(OH)2. 通过单因素及正交实验研究反应体系的pH值、反应温度和时间等因素对制备的非晶态Ni(OH)2电化学性能的影响. 结果表明,主要影响因素为pH值,其次为反应温度和时间. 采用TX-100/正丁醇/环己烷/水体系,控制TX-100与正丁醇的体积比为1:15,W值(水与表面活性剂质量比)为15.1,pH为12,反应时间2 h,反应温度55℃的条件下进行反应,放入0~5℃的超低温恒温槽中快速冷冻沉淀,合成出Ni(OH)2非晶相粉体电极活性材料,该材料的放电比容量达333.22 mA×h/g,具有较高的电化学容量. 初步探讨了微乳液快速冷冻沉淀法制备非晶态Ni(OH)2粉体的作用机理.     

pH值对水热法合成纳米LaPO_4粉体的物相和形貌的影响

以La(NO3)3和(NH4)2HPO4为原料,采用水热法,在不同pH值条件下制备了LaPO4纳米晶体,通过利用X射线衍射(XRD)和扫描电镜(SEM)测试手段,研究了pH值对LaPO4组成和形貌的影响。实验结果表明:pH值对纳米LaPO4晶体的生长影响较大,酸性条件下对LaPO4晶体的生长很有利,但当酸性过强(pH值2)时,H+浓度过高,会影响HnPO(3-n)-4水解,导致产物结晶度降低,实验表明在pH值为2合成的产物结晶最好,为单斜相结构的纳米棒。     

PVP导向ZnO纳米线、纳米棒的可控溶剂热合成及其生长机理研究

本文采用强碱性的溶剂热法,通过调控反应温度、时间、反应物投料比、特别是添加剂等影响因素,可控合成了两种不同形貌的一维ZnO纳米材料.利用透射电镜(TEM)和扫描电镜(SEM)研究了不同影响因素对ZnO产物形貌的影响.着重分析了添加剂聚乙烯吡咯烷酮(PVP)与纳米ZnO或其生长基元的络合作用,及其对纳米ZnO形貌的控制作用,并总结出强碱性溶剂热合成中反应温度、体系压强和pH值对ZnO产物形貌的作用机理.     

化学沉淀-水热法合成高矫顽力碳纳米管磁性复合材料

采用化学沉淀-水热法成功的合成了一种新颖的Ni0.75Zn0.25Fe2O4纳米晶包覆多壁碳纳米管(Ni0.75Zn0.25Fe2O4-CNTs)磁性复合材料.采用透射电镜、X射线衍射、红外光谱和振动样品磁强计等方法对制备的样品进行了表征.透射电镜结果表明Ni0.75Zn0.25Fe2O4纳米晶包覆在碳纳米管表面,纳米晶的大小为8～15 nm.X射线衍射结果表明:200℃是制备纳米Ni0.75Zn0.25Fe2O4包覆碳纳米管复合材料较好的反应条件,比合成单相Ni0.75Zn0.25Fe2O4纳米晶的温度要低.磁性复合材料中Ni0.75Zn0.25Fe2O4晶体的大小约为16.0nm.红外结果表明NiZn的特征峰在590cm-1和414cm-1处.磁滞回线结果表明室温下复合材料具有较高的矫顽力(Hc=27 244.3 kA/m).     

水热法制备铁锡纳米复合氧化物及表征

以Fe(NO3)3·9H2O,SnCl4·5H2O为原料,通过改变水热反应的条件合成了铁锡纳米复合氧化物.用X射线衍射仪和透射电镜对产物的结构和微观形貌进行了表征.结果表明:在水热制备铁锡复合氧化物的过程中,通过分步控制温度法和使用不同的沉淀剂可以控制产物的粒径大小和形貌.最终得到以棒状的α-Fe2O3晶体为核,附着有SnO2粒子的纳米复合氧化物.并对复合物形成机理进行了初步探讨.     

水热条件对金红石型纳米二氧化钛微结构的影响

对金红石型纳米二氧化钛进行水热处理,利用X射线衍射和透射电镜对水热处理前后的纳米二氧化钛进行了表征。研究了pH值、水热反应温度和水热反应时间对金红石型纳米二氧化钛形貌和晶粒尺寸的影响。结果表明:随着pH值的增加,纳米二氧化钛粒子的生长速度减慢。随着水热反应温度的升高和水热反应时间的延长,纳米的晶粒尺寸和原始粒径逐渐变大。水热条件对纳米二氧化钛形貌的影响不大。     

液相化学还原法制备纤维状纳米镍

采用液相化学还原法,利用醋酸镍为母体,1,2-丙二醇为还原剂,氢氧化钠为pH调节剂,以表面活性剂聚乙二醇-6000(PEG-6000)为修饰剂,在1,2-丙二醇体系中合成了纤维状多晶纳米镍。通过X射线衍射(XRD)、透射电子显微镜(TEM)、选区电子衍射(SAED)对所制备的样品进行了表征。通过傅立叶红外仪(FTIR)分析初步解释了纤维状纳米镍的形成机理。     

锂离子电池正极材料LiNi1/2Co1/6Mn1/3O2的制备与性能

采用Co2+浓度递增的金属离子混合溶液分次共沉淀方法制备Ni1/2Co1/6Mn1/3(OH)2,以其为前驱体,通过高温固相反应得到具有Co含量梯度的层状LiNi1/2Co1/6Mn1/3O2,探讨了焙烧温度及Co含量梯度对材料的结构和电化学性能的影响. 通过X射线衍射、扫描电镜、热重分析及恒电流充放电测试对合成的样品进行了表征. 结果表明,700℃合成产物即具有类LiNiO2的六方层状结构,800和850℃合成产物阳离子排列有序度高,层状结构显著. 材料结晶度好,粒度均匀,粒径在亚微米级. 合成温度800℃的梯度材料具有最佳的电化学性能, 2.5~4.2 V, 0.1 C倍率充放电50次后,梯度材料的容量仍保持在171.2 mA×h/g. 相同的焙烧温度,梯度材料比均匀材料的电化学性能更加优异.     

Fabrication of NiO-ZnO/RGO composite as an anode material for lithium-ion batteries

NiO-ZnO/RGO composite was obtained by the annealing of an Ni (OH)₂-Zn (OH)₂/RGO precursor, which has been fabricated by in situ ultrasonic agitation. Moreover, the NiO-ZnO nanoflakes are evenly distributed on the RGO sheets based on the scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization results. When the NiO-ZnO/RGO composite was used as an anode material in lithium-ion batteries (LIBs), the electrodes exhibited a high reversible capacity of 1017 mA h/g at a current density of 100 mA/g after 200 cycles and a specific capacity of 458 mA h/g at 500 mA/g even after 400 cycles. The electrode even reached a capacity of 185 mA h/g at a current density of 2000 mA/g. The excellent electrochemical properties of the NiO-ZnO/RGO composite might be attributable to the NiO-ZnO nanoflakes offering rich electrochemical reaction sites and shortening the diffusion length for lithium ion (Li⁺), as well as the RGO sheets improving the transfer rates of Li⁺ and electron during the charge-discharge process.     

纳米氧化镍的制备及表征

以尿素、NiCl2·6H2O为原料,采用均相沉淀法制备了前驱体Ni(OH)2,再经高温煅烧,得到纳米氧化镍。用TG DTA热分析、X射线衍射(XRD)、扫描电镜观察(SEM)等测量方法对氧化镍前驱体的热分解过程、纳米氧化镍颗粒的晶体结构、粒径和形态进行了研究。     

二硫化镍/氢氧化镍空心球的制备及其电容器性能研究

以均匀硫纳米球为硬模板，通过直接沉淀法在硫纳米球表面包覆一层氢氧化镍纳米片，得到均匀硫@氢氧化镍前驱体，前驱体经低温煅烧获得二硫化镍/氢氧化镍复合纳米空心球，用其制备的电极具有良好的电化学性能。通过X射线衍射和透射电镜等对复合材料的成分和形貌进行分析。结果表明：复合材料纯度较高，组分为二硫化镍和氢氧化镍，二者物质的量比约为1∶1；复合材料是大小均匀的多孔纳米空心球，空腔直径约为500 nm，表面覆盖超薄纳米片，长度约为250 nm，整体形如花球，大小约为1 μm。采用循环伏安、计时电位等方法对复合材料超级电容器性能进行研究。结果表明，在1 A/g电流密度下电极比电容达到1 446 F/g；在20 A/g电流密度下电极比电容仍高达976 F/g；在10 A/g电流密度下循环5 000次，电极容量保持率为86.4%，具有良好的倍率性能和循环稳定性。     

氧化铜纳米晶的合成及其丙酮气敏性能研究

本文通过水热的方法,合成CuO纳米材料.利用广角X射线衍射(Wide-angle XRD),透射电子显微镜(TEM),并结合氮气吸附(N2 adsorption measurement)等手段,证实这是一种高度结晶的单分散纳米CuO材料.气敏测试表明,CuO纳米晶是一种优异的丙酮气体敏感材料,具有较低的工作温度和较高的丙酮敏感性能.本文中,我们对该现象进行了分析,并提出其可能的机理.     

Effects of mechanochemical treatment of Ni–Al(OH)3 on the preparation of carbon nanomaterials by thermal CVD

Carbon nanomaterials have been prepared by the thermal chemical vapor deposition (CVD) method in which C₂H₂ gas was deposited on the Ni–Al(OH)₃ mixture pretreated by mechanochemical treatment with a high-energy mill. As the duration time of grinding for the Ni–Al(OH)₃ mixture by the mixer mill is increased, amorphous Al(OH)₃ and smaller Ni particles agglomerated into spheres. With unground and 120-min ground mixture of Ni–Al(OH)₃, carbon nanomaterials were prepared at 500 and 600 °C. As a result, carbon nanomaterials prepared on a ground mixture have more uniform morphologies than those of the unground mixture. The characterization of Ni–Al(OH)₃ mixture and as-prepared carbon samples was done by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy and current–voltage (I–V) measurement.     

Polypropylene as a carbon source for the synthesis of multi-walled carbon nanotubes via catalytic combustion

Multi-walled carbon nanotubes (MWCNTs) were efficiently synthesized by catalytic combustion of polypropylene (PP) using nickel compounds (such as Ni₂O₃, NiO, Ni(OH)₂ and NiCO₃ · 2Ni(OH)₂) as catalysts in the presence of organic-modified montmorillonite (OMMT) at 630-830 °C. Morphologies of the sample undergoing different combustion times were observed to investigate actual process producing MWCNTs by this method. The obtained MWCNTs were characterized by X-ray diffraction (XRD), transmission electron microscope and Raman spectroscopy. The yield of MWCNTs was affected by the composition of PP mixtures with OMMT and nickel compounds and the combustion temperature. The proton acidic sites from the degraded OMMT layers due to the Hoffman reaction of the modifiers at high temperature played an important role in the catalytic degradation of PP to supply carbon sources that are easy to be catalyzed by nickel catalyst for the growth of MWCNTs. The XRD measurements demonstrated that the nickel compounds were in situ reduced into the Ni(0) state with the aid of hydrogen gas and/or hydrocarbons in the degradation products of PP, and the Ni(0) was really the active site for the growth of MWCNTs. The combination of nickel compounds with OMMT was a key factor to efficiently synthesize MWCNTs via catalytic combustion of PP.     

Preparation and characterization of pyrochlore oxide Y2Ti2O7 nanocrystals via gel-combustion route

Pure-phase pyrochlore oxide Y₂Ti₂O₇ nanocrystals with good dispersity were successfully synthesized via a glycine-nitrate gel-combustion approach. The preparation process and products were monitored and characterized by Fourier transform-infrared spectra, thermogravimetry-differential scanning calorimetry, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The detailed results suggested that the phase and nature of as-obtained products are highly dependent of the pH value of the precursor solution and the amount of glycine. Under the appropriate conditions that the pH value of the precursor is 2.0, the fuel-to-oxidant ratio is 2.0, and the calcination temperature is 800 °C, the as-prepared products are almost sphere-like or ellipsoid, exhibits perfect crystalline phase, good dispersity and a narrow particle distribution with an average size diameter of 20–30 nm. This soft-chemistry route can be also extended to prepare Y₂Ti₂O₇-based functional nanomaterials and other pyrochlore-oxide nanocrystals.     

Particle Size Comparison of Soft-Chemically Prepared Transition Metal (Co, Ni, Cu, Zn) Aluminate Spinels

Nanocrystalline MAl₂O₄ (M=Co, Ni, Cu, Zn) spinel powders are synthesized by pyrolysis of complex compounds of aluminum and transition metal (cobalt, nickel, copper, and zinc) with triethanolamine (TEA). The precursor materials are formed on complete dehydration of the soluble complexes of aluminum–TEA and transition metal–TEA (Co, Ni, Cu, Zn), maintaining the resulting pH of each of the solutions at 4–5. The precursors are heat treated at different temperatures to provide phase formations. Single-phase MAl₂O₄ spinel powders were obtained after heat treatment of the precursor material at 600°C, but for CuAl₂O₄, the precursor passed through an intermediate-phase CuO at a lower treatment temperature. The precursor and the heat-treated powders were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometry, thermal gravimetric and differential thermal analysis, and transmission electron microscopy (TEM); the surface area was measured by a Brunauer–Emmet–Teller (BET) adsorption isotherm. The average particle sizes that were obtained from XRD, TEM, and BET adsorption isotherm were compared.