氮掺杂多孔晶态碳的合成及其电容特性的应用

采用水热-活化法以葡萄糖为碳源、尿素为氮源合成出高含氮量的多孔晶态碳材料.采用透射电镜、X射线衍射、N2吸附-脱附和X射线光电子能谱对材料的结构进行表征;利用循环伏安、恒流充放电和电化学阻抗对材料进行电容性能的测试.结果表明:合成材料具有强的结晶性、大的比表面积(1567 m2/g)、和高的氮含量(7.97at;).当其做为电极材料应用于超级电容器中时,其展示出良好电化学性能,在1 A/g时,其比电容为258 F/g,要远高于含氮的活性碳(222F/g)和晶态碳(106F/g)的电容;5000次循环后,其比电容保持率为99.98;;在功率密度为500W/kg下其能量密度为10.69 Wh/kg.     

花状NiCo-LDH/CB复合材料的制备及其电化学性能研究

以乙醇为溶剂,采用溶剂热法制备了三维花状层状双氢氧化物(Layered Double Hydroxides, LDH)与炭黑(Carbon Black, CB)复合的复合材料。采用X射线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)对样品的结构和形貌进行表征,并通过循环伏安、交流阻抗和恒流充放电研究了材料的电化学性能。结果表明,作为超级电容器电极材料,所制备的NiCo-LDH/CB和NiCo-LDH/CB-D电极在1 A·g^-1电流密度下的比电容分别为1 520 F·g^-1和2 127 F·g^-1,即使在7 A·g^-1高电流密度下,其比电容仍可达1 438 F·g^-1和2 011 F·g^-1,容量保持率为94.6%和94.5%。与单纯的花状NiCo-LDH相比,CB的引入明显提升了材料的电化学性能。     

镍硫化物/碳纳米管复合材料的制备及电化学性能研究

采用溶剂热法以NiC12·6H2O为镍源,乙醇为溶剂制备Ni/CNTs前驱体,在水热反应条件下,用Na2S2O3·5H2O对Ni/CNTs前驱体进行硫化,得到NS/CNTs复合材料.对其电化学性能进行测试,NS/CNTs复合材料在1A·g-1电流密度下的比电容可达533.33 F·g-1,经1000次循环充放电后,比电容保持率为42.50;.相较于NS纳米片(146.67 F·g-1和27.27;),NS/CNTs复合材料的电化学性能得到了显著提升,表明CNTs的加入能明显改善镍硫化物的电化学性能.     

二氧化钒/泡沫镍一体化电极材料的制备及其电化学特性研究

采用五氧化二钒,草酸和泡沫镍作为原料,经一步水热反应法,成功制备出二氧化钒/泡沫镍一体化电极。X-射线衍射仪(XRD)和扫描电子显微镜(SEM)用来表征二氧化钒/泡沫镍电极材料的物相和形貌。结果显示,当草酸浓度为0.1 mol·L~(-1)时,制备的二氧化钒具有纳米片状结构,其厚度为80~140 nm。电化学结果显示,二氧化钒/泡沫镍一体化电极材料,其比电容高达3.99 F·cm~(-2)(在电流密度为1 m A·cm~(-2)),这是由于生长在泡沫镍上片状二氧化钒具有高的比表面积。经过2000次的循环后,二氧化钒/泡沫镍电极的比电容仅损失9.95%,显示很好的循环稳定性。     

负极材料Li4Ti5O12的制备与性能研究

利用纳米二氧化钛(P25)粉为钛源,Li2CO3为锂源,采用固相法及高能球磨法制备亚微米级尖晶石Li4Ti5O12.将Li4Ti5O12与碳纳米管(CNTs)制备成复合电极作为工作电极与锂片组成电池进行电化学性能测试.通过SEM,XRD等表征材料形貌、结构及粒径分布,通过充放电测试表征其电化学性能.结果表明,在800℃合成温度及8h合成时间制备条件下可以得到小尺寸且颗粒均匀的亚微米晶体Li4Ti5O12,且合成的产物电化学性能最佳.在800℃及8h合成条件下,产物首次充放电容量分别为188.0 mAh/g和189.1 mAh/g,首次充放效率为99.4％,且具有良好的可逆性.     

溶剂热合成Co(OH)2/活性炭复合电极材料及其电化学性能研究

以Co(NO3)2·6H2O,CO(NH2)2和活性炭(AC)为原料,利用溶剂热法合成了Co(OH) 2/AC复合电极材料.X射线衍射仪、扫描电子显微镜、傅里叶红外光谱和热重分析显示,产物是约为2 μm无定形的Co(OH)2薄片状粒子与AC颗粒复合.电化学测试表明,在6 mol/L KOH电解液中电流密度为1A·g-1时,电极材料的比电容达301F·g-1,倍率特性良好(164 F·g-1,20 A·g-1);比电容值比AC和Co(OH)2分别提高了89;和35;.复合材料电化学性能提升源自于高导电性活性炭和高赝电容比容量Co(OH)2间的协同作用.     

水热法制备ZnO/石墨烯复合材料及其电化学性能研究

采用水热法制备ZnO/石墨烯复合材料,研究了ZnO、石墨烯不同配比与其电化学性能的关系.通过X射线衍射(XRD)、扫描电镜(SEM)、恒电流充放电、循环伏安法和交流阻抗等测试方法对复合材料结构、形貌及电化学性能进行表征,并通过电池解扣结合SEM和EDS进一步研究电极充放电前后的形貌及组分变化.结果表明,ZnO与石墨烯质量比为1∶1时电化学性能最好,在50 mA/g电流密度下首次可逆比容量高达680 mAh/g,且循环100次之后仍保持相对最高.电池解扣分析证明电极材料在充放电过程中表面会产生微裂纹影响其电化学性能.     

二氧化钒/泡沫镍—体化电极材料的制备及其电化学特性研究

采用五氧化二钒,草酸和泡沫镍作为原料,经一步水热反应法,成功制备出二氧化钒/泡沫镍一体化电极.X-射线衍射仪(XRD)和扫描电子显微镜(SEM)用来表征二氧化钒/泡沫镍电极材料的物相和形貌.结果显示,当草酸浓度为0.1 mol·L-1时,制备的二氧化钒具有纳米片状结构,其厚度为80 ～ 140 nm.电化学结果显示,二氧化钒/泡沫镍一体化电极材料,其比电容高达3.99 F·cm-2(在电流密度为1 mA·cm-2),这是由于生长在泡沫镍上片状二氧化钒具有高的比表面积.经过2000次的循环后,二氧化钒/泡沫镍电极的比电容仅损失9.95;,显示很好的循环稳定性.     

腐植酸钾一步炭化活化制备孔径可调的活性炭材料及其电化学性能

以腐植酸钾为碳源,乙酸钾(CH3COOK)、氢氧化钾(KOH)、碳酸钙(CaCO3)分别为活化剂,在800℃氮气气氛下碳化活化1h制备出了具备不同孔结构的三种活性炭材料.利用N2吸附-脱附分析、扫描电子显微镜(SEM)分析了所得活性炭材料的孔结构和微观形貌,并利用循环伏安(CV)和恒流充放电(GCD)测试方法评价了其作为超级电容器电极材料的电化学性能.结果表明:不同活化剂对活性炭材料的比表面积和孔径分布影响显著,而后者又进一步决定了炭材料的比电容特性.其中,尤其是直径小于1 nm的超微孔炭材料可以获得很高的比电容.在三种不同结构的活性炭中,以CH3COOK为活化剂制备的活性炭具有最优的电化学性能,其比表面积约为1100m2/g,孔径集中在0.4 ～0.6 nm;在2 mol/L KOH电解液中,电流密度为0.1 A/g时比电容高达270 F/g;经3000次充放电循环后,该材料的比电容保持率仍超过87;,是一种性能较为理想的超级电容器用电极材料.     

三维网络结构NiCo2S4@NiCo2O4复合电极的制备及其性能

超级电容器具有更大的功率密度、优秀的循环稳定性、极快的充放电速度、超长的循环寿命以及环境友好等突出特点,其性能与构件关系密切,其中最根本的就是组成它的电极材料。本研究主要采用传统的水热法制备出钴酸镍(NiCo₂O₄)电极材料,进而通过离子交换(二次水热)制得镍钴硫(NiCo₂S₄),最后利用化学浴沉积(CBD)法使其与钴酸镍复合,得到最终所需的三维网络结构NiCo₂S₄@NiCo₂O₄复合电极。经过表面形貌表征、循环伏安测试、恒电流充放电测试以及比电容计算分析等可以证明:三维网络结构NiCo₂S₄@NiCo₂O₄复合电极的比电容及循环稳定性等远远优于复合前单一的纯NiCo₂O₄电极材料,具有极大应用前景。     

Calculation of phase diagrams in AlxIn1−xAs/InP,AsxSb1−xAl/InP and AlxIn1−xSb/InSb nano-film systems

The models for calculation of phase diagrams of semiconductor thin films with different substrates were proposed by considering the contributions of strain energy, the self-energy of misfit dislocations and surface energy to Gibbs free energy. The phase diagrams of the Al_xIn_1−xAs and As_xSb_1−xAl thin films grown on the InP (1 0 0) substrate, and the Al_xIn_1−xSb thin films grown on the InSb (1 0 0) substrate at various thicknesses were calculated. The calculated results indicate that when the thickness of film is less than 1 μm, the strain-induced zinc-blende phase appears, the region of this phase extends with decreasing of the layer thickness, and there is small effect of surface energies of liquid and solid phases on the phase diagrams.     

Elastic properties of GexAsySe100−x−y glasses

The elastic properties of Ge_xAs_ySe_100−x−y (0x30; 10y40) glasses have been studied. The results were analyzed in terms of the dependence on the theoretical mean coordination number (mean number of covalent bonds per atom) m (m=2+(2x+y)×0.01). Three ranges of m (2.1m2.51, 2.51<m2.78, 2.78<m3) were revealed, where different dependencies of elastic moduli (Young’s modulus, shear modulus) and Poisson’s ratio of glasses on m were observed.     

Crystal growth of NdAl3(BO3)4 from K2O/MoO3/Nd2O3/B2O3/KF flux

NdAl₃(BO₃)₄ single crystals were grown by the flux method and the TSSG technique using a K₂O/3MoO₃/B₂O₃/0.5Nd₂O₃/KF flux system. Light-violet clear crystals could be obtained. The effects of fluoride on the growth of NAB crystals were investigated. As the content of KF was gradually increased, the growth form of NAB was changed from the equant to the columnar and the primary crystalline region of NAB was shrinked. At the ratio of KF/K₂O = 0.75, NAB crystals could not be grown.     

Synthesis and structure of new phases of the Am?1Bi2BmO3m+3 (m = 2) type

Three polycrystalline bismuth-containing layered perovskite-like oxides are synthesized by high-temperature solid-state reactions. One of these compounds was described previously, namely, Bi₃Ti_1.5W_0.5O₉, for which the unit cell parameters a = 5.372(5) Å, b = 5.404(4) Å, and c = 24.95(2) Å are determined in this study. The other two compounds, namely, Na_0.75Bi_2.25Nb_1.5W_0.5O₉ with the unit cell parameters a = 5.463(1) Å, b = 5.490(7) Å, and c = 24.78(0) Å and Ca_0.5Bi_2.5Ti_0.5Nb_1.5O₉ with the unit cell parameters a = b = 3.843(2) Å and c = 24.97(6) Å, are synthesized for the first time. The compositions of these compounds are based on the composition of the well-known compound Bi₃TiNbO₉ with a high Curie temperature (T _C = 1223 K), in which bismuth, niobium, and titanium atoms are partially or completely replaced by other atoms. The experimental and calculated interplanar distances determined from the X-ray diffraction patterns of the studied compounds are presented. __________ Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 59–64. Original Russian Text Copyright ? 2005 by Geguzina, Shuvaev, Shuvaeva, Shilkina, Vlasenko.     

Digitally alloyed modulated precursor flow epitaxial growth of AlxGa1−xN layers with AlN and AlyGa1−yN monolayers

We propose a new growth scheme of digitally alloyed modulated precursor flow epitaxial growth (DA-MPEG) using metalorganic and hydride precursors for the growth of Al_xGa_1−xN layers with high-Al content at relatively low temperatures. The growth of high-quality, high-Al content Al_xGa_1−xN layers (x_Al>50%) that are composed of AlN and Al_yGa_1−yN monolayers on AlN/sapphire template/substrates by DA-MPEG was demonstrated. The overall composition of the ternary Al_xGa_1−xN material by DA-MPEG can be controlled continuously by adjusting the Column III mole fraction of the atomic Al_yGa_1−yN sub-layer. X-ray diffraction and optical transmittance results show that the AlGaN materials have good crystalline quality. The surface morphology of DA-MPEG AlGaN samples measured by atomic force microscopy are comparable to high-temperature-grown AlGaN and are free from surface features such as nano-pits.     

Vapour epitaxial growth and characterization of InAs1-xPx

The vapour growth of InAs_1-xP_x layers has been carried out by the hydride process. The phosphorus rich part of the system (0.7 ? x ? 1) was especially investigated. Heteroepitaxial deposits of InAs_1-xP_x and InP have been performed on substrates such as InAs, GaAs and GaP. A systematic study of the influence of the substrate orientation on the quality of the layer has been carried out by growth on hemispherical substrates. Preferential planes have been pointed out: (100) and (111) A for InAs, (111) for GaAs and GaP. The band gap variation as a function of the composition has been determined by photoluminescence at 4.2 °K and X-ray diffraction measurements. It fits the equation: E_G(x) eV = 0.425 + 0.722 x + 0.273 x² at 4.2 °K.     

Crystallization behaviours ofCo100−1(x+y)NbxBy amorphous alloys

The crystallization behaviours of Co_100?1(x+y)Nb_xB_y amorphous alloys were investigated by means of differential thermal analysis and a conventional X-ray diffractometer. The crystallization sequences are discussed in terms of the equilibrium phase diagram of the ternary alloy system.Assuming crystallization occurs as a result of nucleation and growth, the stabilizing effect of eutectic phase separation on the crystallization is shown by introducing the effective free energy of the critical nucleus.