火焰原子吸收法研究纳米钛酸锶钡粉体对铅的吸附性能

以氯化钡、氯化锶和四氯化钛为原料,以草酸作共沉淀剂,采用化学共沉淀法制备了纳米复盐吸附剂——钛酸锶钡粉体,并利用TEM,XRD和FTIR进行了表征。以火焰原子吸收为检测手段,详细考察了该纳米吸附剂对水中铅的吸附性能。结果表明：该法合成的钛酸锶钡粉体外形以棒状为主,平均粒径为36 nm,为纯净的钙钛矿纳米粉体。该纳米粉体对水中的铅具有较强的吸附能力,吸附量受介质的pH值影响较大,当pH值为6.0时,该吸附剂对水中铅的吸附容量可达13 mg·g-1。吸附于纳米钛酸锶钡上的铅可用0.5 mol·L-1的硝酸完全解脱。建立了纳米钛酸锶钡粉体吸附富集,火焰原子吸收法测定水中痕量铅的新方法,该法检出限为11 μg·L-1,相对标准偏差为2.6%。用于地表水中铅的测定,结果满意。     

双硫腙包覆钛酸锶钡粉体对水中镉的吸附性能

用草酸盐化学共沉淀法合成钛酸锶钡粉体,用双硫腙对该粉体表面进行包覆修饰,制成新型有机包覆吸附剂。用傅里叶变换红外光谱对包覆粉体进行了表征;以火焰原子吸收为检测手段,研究了该吸附剂对水中Cd2+ 的吸附性能,考察了洗脱条件;通过红外光谱,初步探讨了包覆和吸附作用机理。结果表明,双硫腙以氢键作用牢固地包覆于钛酸锶钡粉体上;该包覆粉体对水中的Cd2+具有较高的选择性吸附能力,其吸附量受介质的pH值影响,当pH值小于3时,该吸附剂对水中的Cd2+几乎不吸附,当pH值大于6时,吸附量达到最大;常温下,20 min内吸附达到平衡;吸附在双硫腙包覆钛酸锶钡粉体上的Cd2+,可用5% EDTA溶液完全洗脱。建立了吸附富集,火焰原子吸收法测定水中Cd2+的新方法,方法检出限为0.2 μg·L-1,相对标准偏差为2.9%。应用于自来水和地表水中Cd2+的测定,结果满意。     

钛酸锶钡纳米管的制备及其红外吸收性能研究

首次采用溶胶凝胶法结合通孔阳极氧化铝模板, 成功制备出了钛酸锶钡纳米管. 该制备工艺简单、易实现而且成本低. 首先制备通孔阳极氧化铝模板和钛酸锶钡溶胶, 然后通过浸渍加上匀胶的方法将钛酸锶钡溶胶引入到通孔阳极氧化铝模板的纳米孔洞中, 最后在650℃下煅烧1 h形成钛酸锶钡纳米管. X射线衍射(XRD)证明, 制得的钛酸锶钡纳米管为立方钙钛矿相, 主要沿(110)晶向生长. 扫描电子显微镜(SEM)显示, 钛酸锶钡纳米管外径、内径和管长分别为75 nm, 50 nm, 16 μm. 傅里叶变换显微红外光谱仪(FTIR)测试结果表明在波数为1350-1650 cm^-1红外波段, 阳极氧化铝/钛酸锶钡纳米管复合结构较钛酸锶钡薄膜有两处明显的吸收峰, 吸收峰位于1470和1550 cm^-1处, 与通孔阳极氧化铝模板相比其吸收峰强度高出一倍, 最后分析了出现这一现象的可能原因.     

负载纳米二氧化钛分离富集-火焰原子吸收光谱法测定痕量金的研究与应用

报道了负载对二甲胺基苯亚甲基若丹宁(DMABR)的纳米二氧化钛分离富集-火焰原子吸收光谱法(FAAS)测定痕量金的新方法。该方法具有操作简便、线性关系良好,灵敏度高和精密度高等优点。在动态条件下系统地研究了溶液pH值、流速、洗脱条件和干扰离子对痕量金分离富集的影响。结果表明,在pH为3.5时样品溶液以0.6mL.min-1流速过柱,金可被负载纳米二氧化钛定量富集。吸附的金可用0.1mol.L-1HCl-0.5mol.L-1硫脲以0.5mL.min-1流速完全洗脱。在优化的实验条件下,负载纳米二氧化钛对金的动态吸附容量为23.19mg.g-1。线性范围为0～0.40μg.mL-1,r=0.9993,检出限(3σ,n=11)为2.34ng.mL-1,相对标准偏差(RSD%)为2.9%(n=6,c=0.10μg.mL-1),加标回收率在96.7%～101.7%之间。方法用于实际水样中痕量金的测定,结果满意。     

花生壳吸附水中苯酚的热力学与动力学研究

利用废弃的花生壳对水中苯酚进行吸附试验,考察了吸附的最佳条件、吸附热力学和动力学特征.采用Langmuir和Freundlich等温线对平衡数据进行了线性拟合,结果表明,花生壳对苯酚的吸附平衡符合Freundlich等温方程.在298K下,吸附焓变△H=-5.12kJ ·moL^-1,自由能变△G=-4.41 kJ·moL^-1,熵变△S=-2.38J·mo1-1·K-1.表明：该吸附过程为自发进行的放热过程,其动力学行为更好的符合Lagergren准二级动力学模型.     

纳米TiO2预分离/富集FAAS法同时测定Cr(Ⅲ)和Cr(Ⅵ)的研究

纳米材料是近年来受到广泛重视的一种新兴功能材料,具有一系列新异的物理化学特性和一些优于传统材料的特殊性能.其中一点是随着粒径的减小,表面原子数迅速增大,表面原子周围缺少相邻的原子,具有不饱和性,易与其他原子相结合而稳定下来,因而具有很大的化学活性.纳米材料对许多金属离子具有很强的吸附能力,是痕量元素分析较为理想的分离富集材料.文章利用火焰原子吸收法(FAAS)研究了纳米TiO2(金红石型)对Cr(Ⅵ)/Cr(Ⅲ)的吸附性能,并应用于水样中铬的形态分析.吸附体系中pH对Cr(Ⅵ)和Cr(Ⅲ)的吸附有很大影响,当pH＞6时,纳米TiO2对Cr(Ⅲ)的吸附率大于90%,而对Cr(Ⅵ)基本不吸附,从而达到二者的分离.pH 6.5微酸性条件下,纳米TiO2吸附Cr(Ⅲ),然后以2mol.L-1HCl洗脱,得到Cr(Ⅲ)的含量,剩余水溶液中测定Cr(Ⅵ)含量.该法测定Cr(Ⅵ)和Cr(Ⅲ)的检出限分别为57和41 ng·mL-1,RSD分别为2.6%和3.4%(2.0μg·mL-1Cr,n=6),Cr(Ⅵ)和Cr(Ⅲ)的线性范围分别为0～9.0和0.1～10μg·mL-1.该法选择性好,大多数共存离子不干扰测定.该法简便快速,用于工业废水、地表水中铬的形态分析,结果较满意.     

火焰原子光谱法分析有机功能试剂改性纳米SiO2对水中Cr2072-的吸附行为

以纳米二氧化硅(Nano-SiO2)为原料,硅烷偶联剂(KH-550)作为交联剂首先合成了氨丙基纳米二氧化硅(Nano-APSG),然后加入有机功能试剂季磷盐(COOH-Ph-CH2-P(C6H5)3Br)通过有机合成反应合成有机功能试剂改性纳米二氧化硅材料(Si|(CH2)3-NH-CO-Ph-CH2-P(C6H5)3Br),利用红外、粒径、热重分析等对结构进行了表征.通过火焰原子吸收光谱法研究此有机功能试剂改性纳米二氧化硅材料对水中Cr2O12-离子的吸附行为,考察了吸附的最佳pH、震荡时间、吸附剂用量等因素的影响,实验结果表明,在pH1,吸附剂用量为0.1 g,震荡时问为30 min时吸附剂对Cr2O72-离子的吸附效率可达95%以上,实验结果表明这种新型的功能材料可实现对废水中Cr2O72离子的分离与处理.     

纳米碳纤维分离富集电感耦合等离子体质谱法测定地质样品中痕量Au

提出了纳米碳纤维微柱分离富集电感耦合等离子体质谱法(ICP-MS)测定地质样品中痕量Au的方法。考察了在动态条件下纳米碳纤维对Au3+的吸附行为,并确定了最佳吸附及洗脱条件。实验结果表明：在pH 2时,待测物可被纳米碳纤维定量富集, 用pH 1的3%硫脲溶液可将吸附在纳米碳纤维上的Au3+定量洗脱。方法对Au的检出限为0.16 ng·mL-1,精密度(RSD)为 8.5%(n=6), 用于测定实际样品中痕量Au的含量,所得结果与标准值吻合较好。     

纳米氧化铝微柱富集-ICP-AES测定绒柄牛肝菌中的痕量稀土元素

以负载了1-苯基-3-甲基-4-苯甲酰基-吡唑酮[5](PMBP)的纳米氧化铝为微柱吸附材料,采用电感耦合等离子体-原子发射光谱法(ICP-AES)研究了动态条件下对稀土离子Sc3+、Y3+和La3+的吸附性能,确定了最佳吸附及解脱条件。在pH为4.5时,分析物均可被上述吸附材料定量吸附;用0.5mol.L-1盐酸溶液可将吸附在微柱上的稀土离子完全解脱。本法对Sc3+、Y3+和La3+的检出限分别为0.15、0.18和0.34μg.L-1;相对标准偏差(RSD)分别为2.5%、3.0%和1.7%(n=12,C=0.5mg·mL-1)。方法应用于绒柄牛肝菌(Boletus tomentipes)中痕量Sc、Y和La的测定,结果满意。     

咪唑功能化聚苯乙烯包覆硅胶微球分离富集——火焰原子吸收光谱法测定痕量银

制备了咪唑功能化聚苯乙烯包覆硅胶微球并用其填充微柱,建立了微柱分离富集--火焰原子吸收光谱法测定痕量银的方法.研究了填充微柱对Ag(I)的吸附性能及影响吸附的因素,用酸性硫脲作洗脱剂,以峰面积检测,测定Ag(I)的线性范围为0.010-0.50μg/mL,相对标准偏差为2.5%(n=3),检出限为0.002μg/mL,灵敏度提高20倍,填充微柱可重复利用.     

Synthesis and characterization of highly-ordered barium-strontium titanate nanotube arrays fabricated by sol—gel method

Highly uniformed barium-strontium titanate nanotube arrays were fabricated using a porous anodic aluminum oxide template from a barium-strontium titanate sol--gel solution. Electron microscope results showed that nanotubes with uniform length and diameter were obtained. The diameters and lengths of these nanotubes were dependent on the pore diameter and the thickness of the applied anodic aluminum oxide template. High resolution transmission electron microscopy and the selected-area electron diffraction pattern investigations demonstrated the perovskite structure and the polycrystalline of the fabricated barium-strontium titanate nanotubes. The characterization of the electrical and dielectric properties had also been made. Compared to thin film material, the intrinsic leakage current density is almost the same. Besides, at 30~℃, the dielectric constant and dielectric loss of the fabricated nanotube is 80 and 0.027 at 1~MHz respectively.     

Temperature Properties of Dielectric Permittivity and Optical Properties of a Multilayer Structure of Variozone Barium–Strontium Titanate

Physics of the Solid State - Optical properties and the temperature dependence of the permittivity of a multilayer structure of a variozone ferroelectric barium-strontium titanate deposited on a...     

Effect of pulsed laser radiation on the structure and electrical properties of ferroelectric ceramics

Ceramic samples of barium titanate and solid solution of barium-strontium titanate subjected to pulsed laser irradiation have been studied by impedance spectroscopy. The measurements have been carried out in the frequency range 10²?C10⁶ Hz and at temperatures in the range from 20 to 450°C. The experimental data are represented by the dispersion of the electric modulus. The activation energy of relaxation processes in the paraelectric phase has been calculated. Scanning electron microscopy has been used to obtain micrographs of the sample surfaces and the data on the elemental composition.     

Thermodynamic estimation of cooling efficiency using an electrocaloric solid-state line

A thermodynamic cycle in a solid-state cooling line including two ferroelectric capacitors which exhibit the electrocaloric (EC) effect is considered. Expressions are derived for determining the cooling factor and the efficiency of the EC cooling line in terms of the Carnot cycle. Numerical estimates obtained for barium-strontium titanate ferroelectric capacitors make it possible to determine the cooling efficiency upon a change in temperature by ΔT = 2 K. At the initial temperature of 272 K, the efficiency is 0.6 Carnot, which considerably exceeds the efficiency of vapor-compression refrigerators.     

Ferrite-ferroelectric phase shifters controlled by electric and magnetic fields

Planar phase shifters fabricated based on ferrite-ferroelectric layered structures are studied experimentally. The structures served as waveguides for spin-electromagnetic waves, whose phase shift was controlled by both electric and magnetic fields. The measurements were performed in the magnetic field range from 900 to 2100 Oe, which corresponds to operating frequencies from 4.0 to 8.5 GHz, with 5- to 20-μm-thick yttrium-iron garnet ferrite films and 200- to 500-μm-thick barium-strontium titanate ferroelectric plates. It is shown that the phase shift may exceed 180° and is a function of the magnetic and electric fields and also of the thickness of the ferrite and ferroelectric layers.     

Effect of a positive temperature coefficient of resistance in thin films of doped strontium-barium titanate

Thin films of doped semiconducting barium-strontium titanate (Ba,Sr)TiO₃ are prepared by pulsed laser ablation. It is shown that the crystal structure, morphology, and electrical properties of (Ba,Sr)TiO₃ thin films are determined primarily by the actual ablation conditions. The ablation regimes of deposition permitting preparation of uniform polycrystalline thin films with a composition close to that of the target and with grain sizes larger than 0.1 μm are established. These samples have a positive temperature coefficient of resistance in the phase transition region. The change in the resistivity can be as much as 100%.     

Design and simulation of self-biased circulators in the ultra high frequency band

Theoretical models were developed to design self-biased Y-junction circulators operating at ultra high frequency (UHF). The proposed circulator designs consist of insulating nanowires of yttrium iron garnet (YIG) embedded in high permittivity barium-strontium titanate (BSTO) substrates. A design with as many as 10⁵ or greater wires may be considered in its entirety to determine the electromagnetic scattering S-parameters of a circulator design, thus helping to mitigate the computational limitations of the available finite element method (FEM) tools. The approach seeks to represent the nanowires and the BSTO substrate by an equivalent medium with effective properties inclusive of the average saturation magnetization, dynamic demagnetizing fields, and permittivity. The effective medium approach was validated in comparison with the FEM models. Using the proposed approach, a self-biased junction circulator consisting of YIG nanowires embedded in a BSTO substrate was designed and simulated in which the center frequency insertion loss was calculated to be as low as 0.16 dB with isolation of −42.3 dB at 1 GHz. The 20 dB bandwidth was calculated to be 50 MHz. These results suggest that practical self-biased circulators at the UHF band are feasible.     

Dielectric properties of nanometer-thick barium-strontium titanate films

Using submillimeter and infrared spectroscopies, the reflectance R(ν) and transmittance T(ν) spectra of heteroepitaxial barium-strontium titanate films of different thicknesses on MgO substrates are taken for the first time in the frequency range 10 < ν < 3000 cm⁻¹. By modeling the experimental spectra by the Fresnel formulas for layered media, the spectra of complex permittivity ɛ*(ν) = ɛ′(ν) + iɛ″(ν) of the films are determined. It is shown that when the film thicknesses decrease down to 10 nm, there appear tensile stresses in the direction parallel to the substrate surface. As a result, the dielectric contribution of a low-frequency soft mode becomes several times larger than before.     

Dielectric and Ferroelectric Properties of Thin Heteroepitaxial Films of SBN-50

Physics of the Solid State - The phase transformations and ferroelectric characteristics of thin films of barium-strontium niobate SBN-50 grown by RF-cathode sputtering in an oxygen atmosphere are...