Journal of Nanoparticle Research
Cobalt ferrite (CoFe(2)O(4)) nanoparticles were synthesized by using the hydrothermal route with the addition of trisodium citrate dihydrate (Na(3)CA center dot 2H(2)O). The formation of CoFe(2)O(4) nanoparticles with size ranging from 13 to 19 nm was confirmed by X-ray diffraction, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy; the clear-cut sharp of the nanoparticles was observed by transmission electron microscopy. By these characterization methods, the evolution of lattice constant and morphologies of the nanoparticles with the addition of Na(3)CA center dot 2H(2)O is observed. Furthermore, the magnetic hysteresis loops measured at room temperature indicate that the magnetic properties of the products also show clear relationship with the masses of Na(3)CA center dot 2H(2)O. For example, coercivity and high-field paramagnetic susceptibility increase with the increasing masses of Na(3)CA center dot 2H(2)O, whereas the saturation magnetization and the effective magnetic anisotropy constant have the maximum values as the mass of Na(3)CA center dot 2H(2)O is 1 g. This change of magnetic properties is related with the expanded lattice and the varied size and shape because of the addition of Na(3)CA center dot 2H(2)O.
关键词:
Cobalt ferrite;Nanoparticles;Hydrothermal method;Magnetism;nanocomposite;nanocrystals;temperature;particles;size
Journal of Applied Physics
The dielectric relaxation and magnetocapacitance effect of one-dimensional spin frustrated compound Ca(3)Co(2)O(6) are investigated. The steplike magnetocapacitance effect is observed and one to one corresponds to the steplike magnetization. We explain this phenomenon from the spin configuration dependent dielectric response. The simulation results using the Monte Carlo method are in good agreement with experimental data at low temperature. The close correspondence between the magnetic and dielectric properties indicates that the coupling is the intrinsic character of Ca(3)Co(2)O. The steplike magnetocapacitance effect may find potential applications in data storage and sensors. (C) 2008 American Institute of Physics.
关键词:
one-dimensional ca3co2o6;triangular lattice;compound;crystal;chains;phase
Journal of Alloys and Compounds
The formation of impurity Li(x)Ni(1-x)O when synthesizing spinel LiNi(0.5)Mn(1.5)O(4) using solid state reaction method, and its influence on the electrochemical properties of product LiNi(0.5)Mn(1.5)O(4) were studied. The secondary phase LixNi(1-x)O emerges at high temperature due to oxygen deficiency for LiNi(0.5)Mn(1.5)O(4) and partial reduction of Mn(4+) to Mn(3+) in LiNi(0.5)Mn(1.5)O(4). Annealing process can diminish oxygen deficiency and inhibit impurity Li(x)Ni(1-x)O. The impurity reduces the specific capacity of product, but it does not have obvious negative effect on cycle performance of product. The capacity of LiNi(0.5)Mn(1.5)O(4) that contains Li(x)Ni(1-x)O can deliver about 120 mAhg(-1). (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Lithium ion batteries;LiNi(0.5)Mn(1.5)O(4);Impurity Li(x)Ni(1-x)O;Electrochemical properties;lithium batteries;rate capability;spinel;performance
曾国勋
,
张海燕
,
胡礼初
,
王力
,
陈易明
人工晶体学报
doi:10.3969/j.issn.1000-985X.2006.04.033
本文研究了利用柠檬酸盐法制备的Zn(Al)O的介电性能.XRD分析显示先驱体燃烧后制成了单相的Zn(Al)O.热重分析显示先驱体易发生不完全燃烧,产生炭黑残留.燃烧产物经600℃,90min加热除去炭黑.2～18GHz的介电谱测量结果显示含炭黑的Zn(Al)O的复介电常数无论实部还是虚部均高于不含炭黑Zn(Al)O;介电谱还显示Zn(Al)O分别在X、Ku波段存在两个损耗峰.其中X波段的损耗峰位易受炭黑的影响,发生移动;Ku波段的损耗峰较稳定.文章理论计算Zn(Al)O微波吸收率.显示出Zn(Al)O对微波具有良好的透波作用.因此,当Zn(Al)O做红外反射材料时,不影响底层材料对微波的吸收.
关键词:
Zn(Al)O
,
微波
,
介电性能
彭义
,
李长生
,
董丽荣
,
丁巧党
,
王昊璐
复合材料学报
为适应20℃～-200℃温度的适用范围, 采用固相法制备了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导材料, 用摩擦磨损试验机测试了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)从液氮温度至室温的摩擦学性能. 结果表明: 在室温20℃下, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)与对偶件轴承钢盘对摩时, 摩擦系数约为0. 35, 当温度降到超导转变温度以下时(液氮温度-170℃)摩擦系数大幅度降低, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导态摩擦系数为正常态值的一半, 实验证明了电子激励对摩擦能量耗散的作用. 为改善室温下Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)摩擦学性能, 掺杂不同质量分数Ag作为润滑组元, 制备了Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导固体润滑复合材料, 取得良好耐磨减摩效果. Ag掺杂不影响Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)复合材料的超导性, 在正常载荷和滑动速度下10 wt%Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)复合材料摩擦系数为0. 2～O. 3, 磨损率为4. 57×10~(-4) mm~3·(N·m)~(-1).
关键词:
Bi(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O10-x
,
Ag
,
复合材料
,
超导转变
,
摩擦学性能
秦邦
,
赵玉宝
,
李辉
,
邱亮
,
樊造
催化学报
doi:10.1016/S1872-2067(15)60877-4
Cr(VI)具有高毒性和强诱变致癌性,且能稳定存在于自然界中,对人类和自然环境危害极大.而容易沉淀和吸附在固体上的Cr(III)毒性较小,约为Cr(VI)的千分之一.因此,将Cr(VI)还原为Cr(III)是处理含铬废水的有效途径.光催化还原是一种环境友好的新型技术,基于可见光的催化还原处理含Cr(VI)废水能够在常温常压下进行,具有经济、高效、清洁和无二次污染等特点而受到广泛关注.采用适宜的晶面生长控制剂,调变不同晶面的相对生长速率,可制得暴露不同晶面、具有多种形貌的Cu2O.将这些具有不同晶面的Cu2O用于光催化氧化降解有机污染物的研究表明, Cu2O的光催化氧化性能与其所暴露的晶面密切相关,其表面残留的用作晶面生长控制剂的表面活性剂对其催化性能有重要影响.相对而言,将Cu2O用于光催化还原Cr(VI)的研究较少,关于晶面导向剂油酸对其光催化还原Cr(VI)性能的影响尚未见报道.
本文采用液相法,首先合成了仅暴露Cu2O{100}晶面的立方体(Cub),进而通过控制晶面导向剂油酸的用量,制得仅外露Cu2O{111}晶面的八面体(OctO)和仅暴露Cu2O{110}晶面的十二面体(RhdO),继而再将OctO和RhdO在C3H6-O2等混合气中于215 oC处理30 min,通过此温和氧化除去表面油酸,获得了具有洁净表面的八面体(Oct)和十二面体(Rhd)的Cu2O.采用X射线衍射(XRD)、扫描电镜(SEM)和傅里叶变换红外光谱(FT-IR)等技术对其物性特征进行了表征.在LED可见光辐照下,对比评价了具有不同晶面的Cu2O光催化还原Cr(VI)的性能,研究了暴露晶面及晶面导向剂油酸等对Cu2O光催化还原Cr(VI)的影响.
XRD研究表明,采用液相法及温和氧化处理可制得纯相的Cu2O,其XRD图中无Cu及CuO等杂峰出现. SEM观测结果表明,所得Cu2O样品形貌均一性较好,采用丙烯选择氧化去除表面油酸后, Cu2O的形貌无明显改变,仅其外表面略有粗化. FT-IR分析进一步说明,去除表面油酸后,其物相仍为Cu2O,没有出现CuO的红外特征吸收.
动力学研究结果显示, Cu2O光催化还原Cr(VI)具有准一级反应动力学特征,晶面导向剂油酸的存在能够在一定程度上减缓光腐蚀和酸腐蚀,有助于较长时间内保持Cu2O光催化还原活性,而对Cu2O光催化速率没有影响.以单位比表面积速率常数为比活性指标,不同晶面Cu2O光催化还原Cr(VI)的活性次序为{111}>{110}>{100}. Cu2O不同晶面的原子配位情况差异明显,且{100}晶面的表面能较低,由此可较好解释具有不同晶面Cu2O光催化还原Cr(VI)活性的不同.八面体Cu2O的{111}面上同时存在配位饱和与配位不饱和Cu,而菱形十二面体Cu2O的{110}面上只有配位饱和Cu,立方体Cu2O的{100}面上只有配位不饱和O.相对于Cu2O的{100}晶面,具有更高表面自由能的{111}和{110}晶面易于产生光生电子-空穴对,从而表现出较{100}晶面更高的光催化活性.而Cu2O{111}晶面表现出更高光催化活性的原因可能是： Cu2O{111}晶面上存在的不饱和Cu可作为活性位点,在某种程度上有利于光生电子-空穴对分离,减少光生电子-空穴对复合,从而提高光催化还原速率.
关键词:
六价铬
,
晶面
,
光催化
,
可见光
,
氧化亚铜
Journal of Materials Science
Plane-wave pseudopotential total energy method was used to calculate the effects of impurity Li atom on crystal structure, electronic and dielectric properties of Si(2)N(2)O. It is proved that Li atom prefers to occupy interstitial site than to substitute the Si atomic site. In addition, the presence of interstitial Li atom leads to relaxation of internal coordinates of Si, N, and O atoms, and bring out a different X-ray diffraction (XRD) pattern compared with that of a pure Si(2)N(2)O. The result is helpful to understand the diversity of experimental XRD data for Si(2)N(2)O sintered with and without Li(2)O additive. The theoretical polycrystalline dielectric constant of Li-doped Si(2)N(2)O is larger than that of a pure one, which can be attributed to a reduction of band gap. The mechanism is that interstitial Li atom provides extra electronic states at the bottom of conductive band.
关键词:
optical-properties;si2n2o;nitride;dioxide;state;phase
