锂快离子导体Li1+2x+2yAlxMgyTi2-x-ySixP3-xO12系统的研究

以LiTi2(PO4)3为基以天然高岭石为起始原料,经高温固相反应(～900℃)制得了一系列新的锂快离子导体材料Li1+2x+ 2yAlxMgyTi2-x-ySixP3-xO1 2(以下简称Ti-Mg-Lisicon).系统的合成温度随x和y值的增大而降低.应用交流阻抗技术测定的电导率数据结果表明x=0.1,y=0.1的合成物的室温电导率最好为1.01×10-4S/cm,而400℃时x=0.1,y=0.3的合成物的电导率最大,为2.53×10-2S/cm.XRD分析结果表明在x=0.1,y≤0.8;x=0.2,y≤0.6的组成范围内均能得到空间群为R3c的合成物.     

锂快离子导体Li1+2xAlxTiyGe2-x-ySixP3-xO12系统的研究

以高岭石为起始原料,经高温固相反应(～1000℃)合成了Li1+2xAlxTiyGe2-x-ySixP3-xO12(以下简称Ti-Ge-Lisicon)系统的锂快离子导体.应用交流阻抗技术测定的电导率数据结果表明,y=1.5,x=0.2的合成物的电导率最好,400℃时电导率达2.13×10-2S/cm,200～400℃内的电导激活能为30.6kJ/mol.XRD分析结果表明在一定的组成范围内得到空间群为R3c的合成物.     

快离子导体Na2＋xZr2—xYbxSiP2O12系统的研究

以高温固相反应制备了 Na_(2 x)Zr_(2-x)Yb_xSiP_2O_(12)系统的合成物,确定了它们的相组成以及 Nasicon 单纯相的范围。计算了系统合成物的晶胞参数,测定了它们从室温至400℃的电导率。x=1.5的合成物具有最好的导电性,在300℃时其电导率为3.65×10~(-2)(Ω·cm)(-1),在200～400℃温区内其活化能为26.36 kJ/mol。     

Zn2+、Ge4+的取代对Li5AlSi2O8的影响

尝试以叶腊石为基体,通过高温固相反应,合成通式为Li5+xAl1-xZnxSi2-2xGe2xO8(x=0.0～1.0)系统锂快离子导体.X射线粉末衍射表明当x≤0.3时体系仍维持原有的Li5AlSi2O8结构(正交晶系);x＞0.5时结构发生明显变化,体系转变成Li6ZnGe2O)8.红外检测显示当x≥0.1红外谱图中出现Li2CO3吸收峰,表明在室温下体系中的Ge4+吸收空气中的CO2而发生分解反应.交流阻抗技术测试交流阻抗表明当温度大于200℃时体系有较高的电导率,最高时为1.11×10-2S/cm(400℃,x=1.0),x≤0.5时离子电导率很低,且不随温度变化.     

锂离子电池正极材料Li2+2xTi1-xCux(NbO4)2的研究

采用高温固相反应合成了Li2+2xTi1-xCux(NbO4)2,XRD分析表明当x≤0.8时均能得到与LiFePO4相同的橄榄石结构.电导率测定结果表明x=0.6的合成物室温电导率最高,为1.26×10-5S/cm,且当x≥0.6时合成物都表现出离子电导的特征.以x=0.6的合成物做成的待测电极与锂片组成电池,在1mol/L的LiPF6/EC+DMC(1∶1)电解液中在0.5～4.6V间以0.10mA/cm2的电流密度进行电池循环测试的结果表明,该电池的首次放电比容量高达805.8mAh/g,放电平台在对Li+/Li电对为2V附近,但其可逆性及循环性均有待改善.     

Li_(1+x)Ti_(2-x)Cr_xP_3O_(12)系统的相关系与电性

研究了 Li_(1+x)Ti_(2-x)Cr_xP_3O_(12)系统的相组成与电性的关系。结果表明,Cr~(3+)能取代 LiTi_2P_3O_(12)中的Ti~(4+)生成固溶体,直至 x=0.8。在固溶体范围内,电导率随 x 的增加不断升高,至 x=0.8时达到极大。此时在室温和300℃的电导率分别为2.4×10~(-4)和4.8×10~(-2)S/cm,电子迁移数在10~(-4)数量级,分解电压为1.8V。对所得结果从结晶化学角度进行了讨论。     

Na_3In_2(PO_4)_3的高温相转变

对化合物 Na_3In_2(PO_4)_3进行差热分析、高温显微镜观察和高温 X 射线衍射研究表明,在升温过程中,化合物经历了超结构相变。在1300℃左右时发生一级可逆相转变。电导测量表明,超结构相 Na_3In_2(PO_4)_3从室温至300℃的电导率均小于10~(?)(Ω·cm)~(-1)。由于超结构的出现可以视作亚晶格的有序化。而无序相的电导率(例 NASICON)大于10~(-6)(Ω·cm)~(-1),所以有序相的电导率大大低于无序相的电导率。     

矿物钠快离子导体Na1+3x+yAlxNdyTi2-x-ySi2xP3-2xO12合成与表征

Na1 3x yAlxNdyTi2-x-ySi2xP3-2xO12钠快离子导体(以下简称Al-Nd-Nasicon)可以用精选的天然叶腊石A12[Si4O10](OH)2为起始原料与其它化合物,经过高温(900～1100℃)固相反应约15h制得.在y=0.3,x≤0.3和y=0.5,x≤0.2的组成范围内可得到具有Nasicon的三方结构空间群属于R3C的固溶体.该相具有较高的电导率,其中起始组成y=0.3,x=0.1的合成物在350℃时电导率为1.80×10-2S/cm.     

M_xCa_(2-x)SiO_4:Ce~(3+),Al~(3+)(M=Mg,Sr,Ba荧光粉的结构与发光特性研究

采用高温固相法合成了一系列M_xCa_(2-x)SiO_4:0.5mol%Ce~(3+),4mol%Al~(3+)(M=Mg,Sr,Ba;x=0.05,0.1,0.15,0.2)荧光粉,通过X射线衍射仪、扫描电镜、荧光光谱仪对荧光粉的结构、形貌和光学性能进行了表征。结果表明,Mg~(2+)掺杂量在x=0.05时合成的荧光粉物相与未掺Mg~(2+)时一致,为γ-Ca_2SiO_4;在450nm激发下特征峰位于565nm,主要源于Ce~(3+)的5d→~2F_(7/2)和5d→~2F_(5/2)跃迁;Mg~(2+)掺杂量在x=0.1~0.2时,荧光粉物相变为β-Ca_2SiO_4,并随着Mg~(2+)的浓度增大,出现杂相,在365nm激发下发射峰位置由503nm迁移至423nm。Sr~(2+)掺杂量在x=0.05~0.15时,合成的荧光粉物相为γ-Ca_2SiO_4,激发和发射光谱与未掺Sr~(2+)时基本一致;当x=0.2时,物相转变为α'_H-Ca_2SiO_4荧光粉,在365nm激发下特征峰位于465nm。Ba~(2+)掺杂量在x=0.05~0.10时,荧光粉物相未有明显变化,但x=0.15~0.20时,合成的荧光粉物相转变为α-Ca_2SiO_4,在365nm激发下特征峰位于460nm。不同离子掺杂获得的荧光粉物相及发光性质变化的原因实际是,由于参与反应的碱土氧化熔点逐渐降低,Mg~(2+)、Sr~(2+)和Ba~(2+)进入Ca_2SiO_4晶格引起相变的趋势在增强。     

矿物锂快离子导体Li1+2xAlxSCyNbyTi2-x-2ySixP3-xO12系统的合成与表征

以LiTi2(PO4)3为母体,天然高岭石为起始原料,经高温固相反应制得了一系列新的锂快离子导体材料Li1+2xA1xScyNbyTi2-x-2ySixP3-xO12(以下简称Sc-Nb-Lisicon).X射线衍射分析表明x=0.1、x=0.2,y≤0.4;x=0.3,y≤0.25的组成范围内能得到类似于Nasicon的三方结构,即空间点群为R3C的合成物.应用交流阻抗技术测试其电导率,结果表明:x=0.1,y=0.3及x=0.2,y=0.15的合成物在室温下有较高的电导率,分别为1.05×10-4S/cm和2.78×10-4S/cm,二者在573K时的电导率可达8.00×10-3S/cm和7.82×10-3S/cm,同时在423～573K具有较低的活化能,分别为31.4kJ/mol和34.8kJ/mol.     

H(2)O(2)-sensitized TiO(2)/SiO(2) composites with high photocatalytic activity under visible irradiation

TiO(2)/SiO(2) composite photocatalysts were prepared by depositing of TiO(2) onto nano-SiO(2) particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO(2)/SiO(2) composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO(2). Increases in the amount of TiO(2) would decrease the dispersion in the composites. H(2)O(2)-sensitized TiO(2)/SiO(2) composite photocatalysts could absorb visible light at wavelength below 550 nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO(2) exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO(2) content over 30% decreased with increasing of TiO(2) content. Increases in the calcination temperature and TiO(2) content promote the formation of bulk TiO(2) and result in a decrease in activity.     

Electrical conductivity of (ZrO2)0.85(CeO2)0.12 (Y2O3)0.03

A number of zirconia-based materials show promise as electrode materials in magnetohydrodynamic (MHD) generators. As a part of an exploratory programme to find suitable materials for graded electrode applications in MHD generators, partially stabilized and fully stabilized sintered ceramic materials are prepared and characterized. The oxygen ion transference number t _ion(O^2–) and electrical conductivity of this material are measured up to 1670 K in the oxygen partial pressure range 1 to 10^–6 atm. The activation energies for conduction are determined. The electrical properties of this material are characterized by mixed conduction, ionic and electronic. The observed conductivity data are explained in terms of the defect equilibrium reactions between tetravelent Ce⁴⁺ and trivalent Ce³⁺ ions.     

Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals

Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.     

Hg(0) oxidative absorption by K(2)S(2)O(8) solution catalyzed by Ag(+) and Cu(2+)

The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (K(2)S(2)O(8), KPS) catalyzed by Ag(+) and Cu(2+) was investigated using a glass bubble column reactor. Concentrations of gaseous Hg(0) and aqueous Hg(2+) were measured by cold vapor generation atomic absorption spectrometry (CVAAS). The effects of several experimental parameters on the oxidation were studied; these include different types of catalysts, pHs and concentrations of potassium persulfate, temperatures, Hg(0) inlet concentrations and tertiary butanol (TBA). The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and catalysts Ag(+), Cu(2+) and Ag(+) provided better catalytic effect than Cu(2+). For example, in the presence of 5.0mmoll(-1) KPS, the mercury removal efficiency could reach 75.4 and 97.0% for an Ag(+) concentration of 0.1 and 0.3mmoll(-1), respectively, and 69.8 and 81.9% for 0.1 and 0.3mmoll(-1) Cu(2+). On the other hand, high temperature and the introduction of TBA negatively affect the oxidation. Furthermore, the removal efficiency of Hg(0) was much greater in neutral solution than in either acidic or alkaline solution. But the influence of pH was almost eliminated upon the addition of Ag(+) and Cu(2+), and high Hg(0) inlet concentration also has positive impact on the removal efficiency of Hg(0). The possible catalytic oxidation mechanism of gaseous mercury by KPS was also proposed.     

Synthesis and structural study of new potassium uranyl selenates K2(H5O2)(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)4 and K3(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)5

Single crystals of new uranyl selenates K₂(H₅O₂)(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₄ (1) and K₃(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₅ (2) were prepared by isothermal evaporation at room temperature. The crystal structure of 1 was solved by the direct method [C2/c, a = 17.879(5), b = 8.152(5), c = 17.872(5) Å, β = 96.943(5)°, V = 2585.7(19) ų, Z = 4] and refined to R ₁ = 0.0449 (wR ₂ = 0.0952) for 2600 reflections with |F _o| ≥ 4σ _F . The structure of 2 was solved by the direct method [P2₁/c, a = 17.8377(5), b = 8.1478(5), c = 23.696(1) Å, β = 131.622(2)°, V = 2574.5(2) ų, Z = 4] and refined to R ₁ = 0.0516 (wR ₂ = 0.1233) for 4075 reflections with |F _o| ≥ 4σ _F . The structures of 1 and 2 are based on [(UO₂)₂(SeO₄)₄(H₂O)₂]^4? layers. The charge of the inorganic layer is compensated by potassium and oxonium ions arranged in the interlayer space. Each K ion is surrounded by seven O atoms belonging to uranyl selenate layers and water molecules, so that it binds with each other the adjacent uranyl selenate structural elements.     

Ferroelectricity in Simple Binary ZrO(2) and HfO(2)

The transition metal oxides ZrO(2) and HfO(2) as well as their solid solution are widely researched and, like most binary oxides, are expected to exhibit centrosymmetric crystal structure and therewith linear dielectric characteristics. For this reason, those oxides, even though successfully introduced into microelectronics, were never considered to be more than simple dielectrics possessing limited functionality. Here we report the discovery of a field-driven ferroelectric phase transition in pure, sub 10 nm ZrO(2) thin films and a composition- and temperature-dependent transition to a stable ferroelectric phase in the HfO(2)-ZrO(2) mixed oxide. These unusual findings are attributed to a size-driven tetragonal to orthorhombic phase transition that in thin films, similar to the anticipated tetragonal to monoclinic transition, is lowered to room temperature. A structural investigation revealed the orthorhombic phase to be of space group Pbc2(1), whose noncentrosymmetric nature is deemed responsible for the spontaneous polarization in this novel, nanoscale ferroelectrics.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Dumbbell-like PtPd-Fe(3)O(4) Nanoparticles for Enhanced Electrochemical Detection of H(2)O(2)

Dumbbell-like Pt(x)Pd(100-x)-Fe(3)O(4) nanoparticles (NPs) were synthesized and studied for electrocatalytic reduction and sensing of H(2)O(2). In 0.1 M phosphate buffered saline (PBS) solution, the 4-10 nm Pt(x)Pd(100-x)-Fe(3)O(4) NPs showed the Pt/Pd composition-dependent catalysis with Pt(48)Pd(52)-Fe(3)O(4) NPs having the best activity. The Pt(48)Pd(52)-Fe(3)O(4) NPs were tested for H(2)O(2) detection, and their H(2)O(2) detection limit reached 5 nM, which was suitable for monitoring H(2)O(2) generated from Raw 264.7 cells. These dumbbell-like PtPd-Fe(3)O(4) NPs are the most sensitive probe ever reported and can be used to achieve real-time quantitative detection of H(2)O(2) in biological environment for biological and biomedical applications.     

Synthesis of Fe(2)O(3)/TiO(2) nanorod-nanotube arrays by filling TiO(2) nanotubes with Fe

Synthesis of hematite (α-Fe(2)O(3)) nanostructures on a titania (TiO(2)) nanotubular template is carried out using a pulsed electrodeposition technique. The TiO(2) nanotubes are prepared by the sonoelectrochemical anodization method and are filled with iron (Fe) by pulsed electrodeposition. The Fe/TiO(2) composite is then annealed in an O(2) atmosphere to convert it to Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The length of the Fe(2)O(3) inside the TiO(2) nanotubes can be tuned from 50 to 550?nm by changing the deposition time. The composite material is characterized by scanning electron microscopy, transmission electron microscopy and diffuse reflectance ultraviolet-visible studies to confirm the formation of one-dimensional Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The present approach can be used for designing variable one-dimensional metal oxide heterostructures.