Direct hydrothermal synthesis and magnetic property of titanate nanotubes doped magnetic metal ions

Pure titanate nanotubes and titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions were synthesized by the hydrothermal method. In this process, titanate nanotubes were first prepared synchronously with doping Fe3 /Ni2 /Mn2 ions. The morphology,structure, thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions are paramagnetic behaviors.     

Microwave absorbing properties and magnetic properties of different carbon nanotubes

The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.     

微波水热法制备含氟钛酸铋系光催化剂及光催化性能研究

以Bi(NO3)3·5H2O和(NH4)2TiF6为原料,采用微波水热法在120℃~220℃反应1h得到了具有不同形貌的粉体.借助XRD、FE-SEM和EDS等分析手段对粉体的组成和形貌进行了表征,并以罗丹明B溶液为目标降解物,研究了200℃下所得粉体的光催化性能.结果表明:所得粉体是一种新型的F掺杂钛酸铋粉体,其中Bi、Ti、O、F的原子比例约为6∶11∶27∶8;随着反应温度的升高,粉体形貌从球形向六棱短柱状转变;紫外光照射下粉体具有较好的降解罗丹明B溶液的能力.     

稀土元素钇和钬掺杂对铁酸铋磁性能的影响

铁酸铋是一种典型的单相多铁性材料,宏观上磁性很弱,为了改善其磁性能,用稀土元素钇和钬对其A位元素进行替代.采用水热法制备掺钇和掺钬的铁酸铋系列粉末样品,然后将这些粉末样品采用常规的固相反应法制备出陶瓷样品.以浓度12.5mol/L的氢氧化钾为矿化剂,反应温度为240℃,反应时间为24h时,得到了掺钇和掺钬的铁酸铋样品.X射线衍射结果显示,当掺杂量小于或等于0.05时,样品结构为纯相的三方铁酸铋结构,当掺杂量大于0.05时,出现了越来越多的杂相;通过振动样品磁强计测试样品的磁性能,发现所有样品都观察到了饱和的磁滞回线,说明掺钇和钬都能明显改善铁酸铋的磁性能;通过对比掺钇和掺钬所有样品的饱和磁化强度值,发现掺杂量相同时,掺钇样品的饱和磁化强度值都要比掺钬的大,而相同大小的钇离子没有磁性,钬离子有磁性,说明稀土离子本身的磁矩可能不是铁酸铋磁性增强的主要因素.     

含氮复合缺陷改性单壁碳纳米管的电学性能

基于第一性原理的密度泛函理论,利用非平衡格林函数方法本文研究了氮原子与SW（Stone-Wales）缺陷组成的复合缺陷对碳纳米管几何结构及电子透射系数的影响。结果显示SW缺陷和掺杂都对单壁管的几何结构和电子性能有显著的影响。对于半导体性（8,0）碳纳米管,复合缺陷增强了体系的输运性能,但是输运特性明显受到杂质原子的位置的影响。     

溶胶-凝胶法制备纳米钛酸钡

以溶胶－凝胶法制备纳米钛酸钡粉体,利用价廉的重晶石为主要原料制备钡源,有效地克服了传统方法因采用有机钡盐或有机钛而导致的生产成本过高的缺点：研究结果表明,该方法可制备出高纯钛酸钡粉体,制备过程中三废排放物中基本不含有害物质,并可从母液中回收质量较高的副产品硝酸铵,具有产品质量高,原料来源广泛、价格低廉、工艺环保、节能等特点．     

金属粒子掺杂的多壁碳纳米管气敏性研究

分别利用化学还原和电化学镀覆方法,对经过浓硫酸浓硝酸混合液酸化预处理的多壁碳纳米管进行Pd和Cu的掺杂,并制备成电流型气敏传感器.以甲醛、苯、甲苯、二甲苯作为测试气体,通过电化学分析仪测试它们在不同气体种类和体积分数下的响应.实验结果表明,传感器在常温下具有较高的灵敏度和重复性,金属粒子的掺杂使传感器的灵敏性和选择性都有较大的改变.影响气敏特性的主要因素包括：碳纳米管自身的结构缺陷、气体分子与金属团簇的反应、金属粒子形成的局部催化活性中心.     

Hydrothermal synthesis and dielectric properties of lanthanum titanate ceramics

Lanthanum titanate (La2/3 TiO3) powders were synthesized by hydrothermal method based on the reaction of TiO2, La(NOa)a and KOH at 160℃ for 24 h followed by the treatment of acidification. The microstructure,morphology and dielectric properties were investigated by using X-ray diffraction, scanning electron microscope,transmission electron microscope and impedance method. The results show that the La2/a TiOa particles consist of nearly homogenous and lamellar grains. The particles can be sintered into porous ceramics above 1 150℃. The dielectric properties of La2/3 TiO3 show that both the dielectric constant and the dielectric loss tangent decrease with the increase of frequency.     

Effects of La~(3 ) doping on MnZn ferrite nanoscale particles synthesized by hydrothermal method

1　INTRODUCTIONMnZnferritesarewidelyusedinelectronicappli cationsbecauseoftheirhigh permeabilityandlowmagneticlossesathighfrequencies[1,2 ] .Theproper tiesofferritesdependlargelyontheirmicrostructure ,sothenano techniqueisintroducedtocontroltheirultramicrostructure ,insteadofthetraditionalceramicway .Additionally ,aprecisesmallamountofcationicsubstitutionisusedusually .ThemagneticlossofMnZn ferritesdopedwithCaO SiO2 athighfrequencyisdiminishedforincreasesofresistivitylayersatgrainbound…     

镁离子掺杂TiO_2纳米管的水热合成、表征及光催化性能研究

以水热法制备的TiO2钛纳米管为模板,在水溶液中通过超声辅助离子交换法合成了镁掺杂的TiO2纳米管/棒。通过扫描电镜、X-射线衍射、光催化等多种测试手段对产物进行了表征,讨论了镁掺杂前后对TiO2纳米管形貌和结构的影响。实验结果表明,镁的掺杂对TiO2纳米管的催化性能有较大提高。     

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10⁻⁷ to 0.165×10⁻³ mol/L. The corresponding detection limit is 3.34×10⁻⁸ mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.     

Effects of size and surface modification of multi-walled carbon nanotubes on mechanical properties of polyurethane-based nanocomposites

Polyurethanes/multi-walled carbon nanotube (PU/CNT) composites were prepared with a help of ultrasonically dispersing CNT in the traditional procedure of synthesizing polyurethane. In this case, the various loading levels, sizes and surface-modified groups were considered to regulate the mechanical performances of the PU/CNT nanocomposites. Moreover, the structure and mechanical properties of all the PU/CNT nanocomposites were investigated by attenuated total reflection-Fourier transform infrared spectroscopy, dynamic mechanical analysis, scanning electron microscope, transmission electron microscope, and tensile testing. The experimental results showed that a moderate loading-level of 0.1wt% and a diameter of 10-15 nm for CNT could produce the maximum tensile strength and elongation while it was worth noting that the surface carboxylation of CNT could further enhance the tensile strength and elongation of the PU/CNT nanocomposites.     

Effects of La^3＋ doping on MnZn ferrite nanoscale particles synthesized by hydrothermal method

MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La³⁺ on the products were discussed. The product was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the sample with 0.2% La³⁺ (mass fraction) or without La³⁺ has only spinel phase, but the sample with mass fraction of La³⁺ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La³⁺ is up to 1.2%. TEM image of the sample with 1.2% La³⁺ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La³⁺ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La³⁺ (2.64 A · m² · kg⁻¹) is lower than that of undoped (17.54 A · m² · kg⁻¹) and it behaves superparamagnetically. Foundation item: Project (2001BA90A09) supported by the Tenth Five-Plan of China     

Effect of Sm-doping on the morphology and magnetic properties of radio frequency magnetron sputtered Ni-Mn-Ga films

Ni55.5Mn21Ga23.5 and Ni54Mn22Ga23Sm1 films were prepared by radio frequency (RF) magnetron sputtering. The effect of Sm do-pant on the morphologic and magnetic properties of Ni55.5Mn21Ga23.5 films was investigated. Sm doping can refine the particle size of the films from 100 to 60 nm, and further grain growth is not occurs even after annealing at 1073 K for 3.6 ks. Compared to Ni55.5Mn21Ga23.5 films, Sm-doped Ni54Mn22Ga23Sm1 films are easier to be magnetized and have a lower martensitic transformation temperature. In addition, the Curie temperature can also be adjusted, decreasing from 350 to 325 K after Sm doping. Martensitic transformation is not observed in the Sm-free films, which is close to the Curie temperature in the Sm-doped films, giving rise to the overlap of the structural and magnetic transi-tion temperatures.     

溶胶凝胶法制备锆钛酸钡超细粉体

为研究用于合成纳米级高纯锆钛酸钡陶瓷粉的溶胶凝胶制备工艺.工艺采用柠檬酸锆为锆源,低价的乙酸与己二醇为溶剂,不采用己二醇独甲醚等有毒溶剂,不仅生产成本显著降低,且为环境友好材料,易于实现产业化.对采用乙酸钡-柠檬酸锆-钛酸四丁酯-己二醇体系制备的锆钛酸钡纳米粉体,通过XRD、TEM、TG-DTA分析,研究确定了溶胶、凝胶及烧结工艺.确定的最佳溶胶工艺条件为:温度40℃,pH 3.5,浓度0.05~0.1mol/L.凝胶经800℃烧结,可获得粒度为40 nm,近球形的单一钙钛矿相锆钛酸钡粉体.     

Preparation and characterization of nanometer-sized barium titanate powder by complex-precursor method

A new complex-precursor method was proposed to prepare nanometer-sized BaTiO3 powder. Firstly,Ti2O（O2）2（ta）24-complex ions were prepared by the reaction of H2O2,Ti^4＋ and ta^3-（ta=[C6H6O6N]^3-） with a desirable amount of surface active agent,and then the Ba2[Ti2O（O2）2（ta）2]·2H2O precursor was obtained by reaction between [Ti2O（O2）2（ta）2]^4-and Ba^2＋. Finally,the precursor was annealed at 800 ℃ for 2 h to obtain BaTiO3 powder. The morphology,the particle size distribution,the purity and the molar ratio of Ba to Ti of BaTiO3 powder were investigated systematically by TEM,XRD,IR,Raman and chemical analysis,respectively. The results show that the BaTiO3 powders with the grain size of about 40 nm have a tetragonal crystalline structure at room temperature and a spherical morphology.     

磁性纳米Fe_3O_4颗粒掺杂多壁碳纳米管修饰的葡萄糖生物传感器

磁性纳米Fe3O4颗粒掺杂多壁纳米碳管混合分散于壳聚糖中,得到壳聚糖胶质液.将其修饰到玻碳电极表面,通过交联剂戊二醛固定葡萄糖氧化酶,制得一种新型的传感器.该传感器在pH=6.8的磷酸盐缓冲溶液中,对葡萄糖的线性响应范围为1.0×10^-5-2.3×10^-2mol/L,响应时间5.3 s.     

Effects of carbon nanotubes on mechanical and 2D-3D microstructure properties of cement mortar

To study the influence of multi-wall carbon nanotubes （MWCNTs） on the mechanical and microstructural properties of cementitious composites, 0.00, 0.02, 0.08, 0.10, and 0.20 wt% of multi-wall carbon nanotubes were added into cement mortar, in which the cement-sand ratio was 1：1.5. The flexural and compressive strengths of cement mortar at the age of 3, 7, 28 and 90 d and the fracture performance at the age of 28 d were determined, its 2D micrograph was tested by means of SEM, and the 3D defects distribution was firstly determined with or without CNTs by means of XCT （X-ray computerized tomography）. The results showed that 0.08 wt% of CNTs improved the compressive strength and flexural strength by 18% and 19~A, respectively, and a significant improvement of its fracture property was observed. Moreover lower addition of carbon nanotubes to cement mortars can improve its microstructure and decrease the defects significantly compared to the cement mortar without CNTs. With the increase of the content of CNTs, the mechanical properties of cement mortars presented to be declined largely due to the agglomeration of CNTs.