Magnetoelectric Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 composite thin films derived by SOL–GEL method

Magnetoelectric (ME) Bi_3.25Nd_0.75Ti₃O₁₂–La_0.6Ca_0.4MnO₃ (BNT–LCMO) composite thin films were deposited on Pt/Ti/SiO₂/Si(100) substrates by a simple SOL–GEL method and spin-coating process with two different deposition sequences: BNT/LCMO/Pt/Ti/SiO₂/Si(BLP) and LCMO/BNT/Pt/Ti/SiO₂/Si(LBP). Our results show the composite thin films exhibit both good ferroelectric and magnetic properties, as well as a ME effect. BLP thin films have larger maximum ME voltage coefficient values than LBP structured thin films. The deposition sequence has a notable effect on the ferroelectric and magnetic properties and ME coupling behavior of the bi-layer thin films.     

La0.6Ce0.4Mn1-yFeyO3微波吸收特性

用溶胶-凝胶法制备了La0.6Ce0.4Mn1-yFeyO3 (y=0.00, 0.12, 0.14, 0.16, 0.18)样品. 用微波矢量网络分析仪测试了该样品在2～18 GHz微波频率范围的复介电常数、复磁导率, 根据测量数据计算了电磁损耗角正切及微波反射率与频率的关系. 结果表明, 当B位掺入铁元素时, 样品吸收峰值增大, 有效吸收频带增宽, 在y=0.14时, 样品微波吸收效果最好. 当样品厚度为2.00 mm, y=0.14时, 吸收峰值为38 dB, 10 dB以上频带宽度达4.1 GHz. 初步探讨了该材料的电磁损耗机理, 发现损耗吸收来自磁损耗和介电损耗的共同作用, 吸收峰所在频率介于介电损耗角正切最大值与磁损耗角正切最大值对应的频率之间, 即在12.7 GHz附近. 对样品的电阻率测试表明, 其室温范围内电导在半导体范围内, 有利于降低微波在样品表面的反射率.     

Impedance spectroscopy of V2O5–Bi2O3–BaTiO3 glass–ceramics

The glasses within composition as: (80 − x)V₂O₅/20Bi₂O₃/xBaTiO₃ with x = 2.5, 5, 7.5 and 10 mol% have been prepared. The glass transition (T_g) increases with increasing BaTiO₃ content. Synthesized glasses ceramic containing BaTi₄O₉, Ba₃TiV₄O₁₅ nanoparticles of the order of 25–35 nm and 30–46 nm, respectively were estimated using XRD. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of BaTiO₃ content by impedance spectroscopy measurements. The hopping frequency, ω_h, dielectric constant, ε′, activation energies for the DC conduction, E_σ, the relaxation process, E_c, and stretched exponential parameter β of the glasses samples have been estimated. The, ω_h, β, decrease from 51.63 to 0.31 × 10⁶ (s⁻¹), 0.84 to 0.79 with increasing BaTiO₃ respectively. Otherwise, the E_σ, increase from 0.279 to 0.306 eV with increasing BaTiO₃. The value of dielectric constant equal 9.5·10³ for the 2.5BaTiO₃/77.5V₂O₅/20Bi₂O₃ glasses-ceramic at 330 K for 1 KHz which is ten times larger than that of same glasses composition. Finally the relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy were determined.     

Phase diagram studies of methanol–CHF3 and methanol–H2O–CHF3 mixtures

Comprehensive phase diagrams of methanol/CHF₃ and methanol/H₂O/CHF₃ mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO₂ for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF₃ and methanol/H₂O/CHF₃ was compared to that of methanol/CO₂ and methanol/H₂O/CHF₃. Fluoroform is markedly more miscible with methanol or methanol/H₂O than is CO₂. Data for methanol/CHF₃ binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.     

XPS study of Ba_(0.6)K_(0.4)BiO_3

Single crystal Ba_(0.6)K_(0.4)BiO_3 was studied by using XPS.The results show that there isno evidence for the presence of Bi~(5+) in single crystal of Ba_(0.6)K_(0.4)BiO_3;instead,there is evidence forthe presence of mixed valent Bi~(3+) and Bi~((3+)-δ).Moreover,the O1s XPS results suggest the presenceof mixed valent O~(2-) and O~(1-),and the valence band spectrum suggests the high degree of covalencyfor Bi—O bonds.     

La0.6Sr0.4MnO3纳米薄膜的制备及其光催化活性

在室温下,采用溶胶-凝胶法和浸渍提拉技术在载玻片基底上制备出了钙钛矿型La0.6Sr0.4MnO3薄膜;采用TG/DTA技术分析了金属羧酸盐凝胶的热分解历程;通过XRD进行了物相分析,并计算了其晶粒尺寸;利用AFM观察了薄膜的形貌特征.实验结果表明,La0.6Sr0.4MnO3薄膜在570 ℃形成,为三方晶系,其平均晶粒度为10.8 am.采用制备出的La0.6Sr0.4MnO3薄膜对多种水溶性染料进行了光催化降解实验,研究发现,该纳米薄膜有较好的光催化效果,在9 h内对酸性红A、酸性橙Ⅱ、弱酸性黄C-3GN、直接绿BE、弱酸性蓝C-RL的脱色率分别达到95.56%,89.70%,97.56%,98.40%和81.16%.     

锰掺杂Ba0.6Sr0.4TiO3-MgTiO3复相陶瓷的制备和介电性能

以分析纯的Ba(NO3)2、Sr(NO3)2、草酸和钛酸丁酯为原料, 采用草酸盐共沉淀法制备了钛酸锶钡（Ba0.6Sr0.4TiO3, BST）纳米粉体. XRD和SEM分析结果表明, 该方法制备出立方相的Ba0.6Sr0.4TiO3粉体, 平均粒径小于100 nm, 具有较高的烧结活性. 用传统固相法制备了锰掺杂钛酸锶钡-钛酸镁(Ba0.6Sr0.4TiO3-MgTiO3, BST-MT)复相陶瓷, 系统研究了掺杂0.1%-2.0%(x, 摩尔分数, 下同)锰对钛酸锶钡-钛酸镁复相陶瓷微观形貌和介电性能的影响机理. 结果表明, 当锰的掺杂量小于1.5%时, Mn作为受主掺杂取代占据钙钛矿ABO3的B位, 因此导致居里点略微向高温偏移和相变扩散的发生, 锰的掺杂导致晶格畸变, 促进了晶粒生长, 使晶界相比例下降, 因此介电损耗随着锰掺杂量的增大而减小; 当锰的掺杂量为1.5%时, 介电损耗达到最小值, 继续增大掺杂量, 介电常数下降, 介电损耗上升.     

Phase Diagrams of Fullerenol-d–LaCl3–H2O and Fullerenol-d–GdCl3–H2O Systems at 25°С

Russian Journal of Physical Chemistry A - Isothermal phase diagrams of ternary systems fullerenol-d–LaCl3–H2O and fullerenol-d–GdCl3–H2O at 25°C are studied via...     

Investigation of Phase Transition inLa1–xPrxGaO3 and La1–xNdxGaO3 Crystals

The solid solution crystals, La_1–xNd_xGaO₃ and La_1–xPr_xGaO₃ have been studied by differential scanning calorimetry method; the crystals exhibit the first order phase transition, the temperature of the transition linearly increases with the concentration of Pr or Nd. The structure of the crystals has been determined by X-ray diffraction. The correlation between the phase transition temperature and crystalline structure at the temperature of the phase transition in both solid solution families is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aza-Morita–Baylis–Hillman reaction with ion-supported Ph3P

Various N-tosyl arylimines reacted with methyl vinyl ketone and ethyl vinyl ketone in the presence of ion-supported Ph₃P A and B to give adducts, N-(2′-methylene-3′-oxo-1′-arylbutyl)-4-methylbenzenesulfonamides and N-(2′-methylene-3′-oxo-1′-arylpentyl)-4-methylbenzenesulfonamides, respectively, in good yields with high purity by simple diethyl ether extraction of the reaction mixture. Moreover, ion-supported Ph₃P A and B could be repeatedly used for the same reaction to provide the corresponding adducts while maintaining good yields with high purity.     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

用柠檬酸溶胶－凝胶法制备钙钛矿型Ｌａ０．６Ｓｒ０．４ＭｎＯ３氧化物,并用Ａｇ对其进行修饰,制得Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３系列催化剂。结果表明,６％Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３催化剂上甲烷或甲醇氧化转化９５％时的反应温度Ｔ９５可低至７３５Ｋ（对ＣＨ４）或４２１Ｋ（对ＣＨ３ＯＨ）;适量Ａｇ的负载修饰并不改变催化剂基质氧化物Ｌａ０．６Ｓｒ０．４ＭｎＯ３的纳米级钙钛矿型结构;Ａｇ的掺杂诱使催     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

Ag-modified La0.6Sr0.4MnO3 catalysts were prepared and their catalytic performance for deep oxidation of CH4 and CH3OH at low concentrations were investigated. The results showed that the La0.6Sr0.4MnO3 host catalyst with the perovskite-type nano-crystallite structure displayed considerably high catalytic activity for deep oxidation of CH4 and CH3OH at low concentrations. Ag modification to the La0.6Sr0.4MnO3 host catalyst resulted in significant enhancement of the catalyst activity, making the T95 (the reaction temperature needed for conversion of 95%of CH4 or CH3OH) lowered down to 735K (for CH4) and 421K (for CH3OH) from 813 and 465 K over the Ag-free system under the reaction conditions:0.1MPa,CH4/O2/N2=2/12/86(molar ratio),GHSV=45000 h-1 and CH3OH/O2/N2= 0.2/1.0/98.8 (molar ratio),GHSV=58000 h-1,respectively.The carbon containing product was almost CO2 and the contents of HCHO and CO in the reaction exit gas were both under GC detectable limit in both cases.
The results of spectroscopic characterization indicated that modification by proper amount of Ag-dopant did not change the perovskite structure of the La0.6Sr0.4MnO3 host catalyst as a whole. Interaction of Ag-dopant with the surface of the host catalyst,La0.6Sr0.4MnO3,was in favor of high dispersion of the Ag component at the catalyst surface and led to the oxidation of part of the Mn3+species to Mn4+,resulting in an increase of amounts of the reducible Mnn+ species and a decrease of their reduction temperature. On the other hand, this interaction led also to enhancement of adsorption ability of the catalyst toward O2 at relatively low temperature. High activity of the Ag modified La0.6Sr0.4MnO3 catalyst for CH4 and CH3OH complete oxidation was closely related to high redox-activity of the catalyst and its prominent adsorption-activation ability to O2 at relatively low temperatures.     

Metal Triflate–Catalyzed Friedel–Crafts Acetylation of 3-Phenylsydnone

Friedel–Crafts acetylation at the 4-position of 3-phenylsydnone (1) was achieved via thermal heating overnight in moderate to good yields by employing various metal triflate catalysts (5–20 mol%), lithium perchlorate (0–20 mol%), and acetic anhydride (4 equivalents) using either acetonitrile or acetic anhydride, in excess, as solvent. Six commercially available, homogeneous metal triflate catalysts were investigated, and optimal conditions were determined. The best yields overall were achieved with indium triflate.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

Li ion dynamics in Li3xLa2/3–x□1/3–2xTiO3 studied by NMR

⁷Li nuclear magnetic resonance relaxation times, T₁ and T_1ρ, versus temperature are reported in the 150–900 K temperature range on the lithium lanthanum titanates, Li_3xLa_2/3–x□_1/3–2xTiO₃, which are fast ionic conductors. Two characteristic frequencies of Li⁺ motions are evidenced in these compounds: the first is in the range of the Larmor frequency when the second one is in the range of the radio-frequency field. These frequencies are respectively attributed to motion of the Li⁺ ion inside the cage formed by the oxygen ions and to jumps between the cages. The T₁ and T_1ρ studies on ⁶Li nuclei confirm the above results and show that the relaxation is not due to quadrupolar interaction at a variance, which is generally accepted.     

Phase Diagram of the AgNO3–CsNO3 System

The phase diagram of the binary AgNO₃–CsNO₃ system was constructed using differential thermal analysis (DTA) technique in the range 300–700 K. The apparatus is described briefly. The results exhibit a congruently melting compound CsNO₃·AgNO₃ (m.p.=453 K) characterized by two allotropic varieties and , an incongruently melting compound AgNO₃·CsNO₃ (m.p.=450 K) with three forms , and , two eutectics (16 mol% CsNO₃, 442 K and 32.5 mol% CsNO₃, 445 K) and a peritectic (38mol% CsNO₃, 450 K). The occurrence of the transitions of intermediates was confirmed by X-ray diffraction at variable temperatures. The phase diagram exhibits also two plateaus at 429 K and 435 K corresponding to the phase transitions of CsNO₃ and AgNO₃, respectively.This revised version was published online in November 2005 with corrections to the Cover Date.     

Gas Hydrate Frameworks of Allen's Polyhedra. 2. Frameworks on 3–6 and 3–5–6 Nets

The structure of two classes of water molecule frameworks built up of 5¹²(D), 5¹²6²(T), 5¹²6³(P), and 5¹²6⁴(H) polyhedra is discussed. Polyhedral layers can be distinguished in the frameworks. The centers of the polyhedra belonging to a layer are at the nodes of planar networks consisting of triangular, pentagonal, and hexagonal meshes. The structure of one network determines exclusively the topology of the entire framework. Frameworks on 3–6 nets can be constructed of two types of polyhedral blocks: D₃T₂P₂and D₂T₆. Frameworks on 3–5–6 nets might include both specific blocks and the blocks involved in the frameworks on 3–5 and 3–6 nets. The paper analyzes the structure of frameworks on the nets built as a series of rows, each of these rows being constructed of pentagons or hexagons exclusively. These frameworks are described by the formula (D₃T₂P₂) _x (D₄H₂) _y (D₂T₆) _z , where x 1, y 0, and z 0 (x, y, and z are integers). Since all known frameworks of Allen's polyhedra satisfy this formula, they can be constructed of fragments of gas hydrate lattices with the CS1, CS2, and HS1 structures because they are derivatives of these key structures. Similar frameworks can be constructed of other tetrahedral particles (C, Si, SiO₂, etc.).     

Investigation of phase equilibria in the Er2O3–Na2O–P2O5 system: the partial system ErPO4–NaPO3–Er(PO3)3

The partial system ErPO₄–NaPO₃–Er(PO₃)₃ of the Er₂O₃–Na₂O–P₂O₅ oxide system has been investigated by thermoanalytical methods and X-ray powder diffraction. On the basis of the obtained results the phase diagram of the partial system is proposed. The system is bounded by three subsystems: (i) ErPO₄–Er(PO₃)₃, (ii) Er(PO₃)₃–NaPO₃ and (iii) ErPO₄–NaPO₃. Their phase diagrams are proposed. In the Er(PO₃)₃–NaPO₃ subsystem an intermediate compound NaEr(PO₃)₄ occurs; it melts incongruently at 655 °C. It was found that ErPO₄ and NaEr(PO₃)₄ form a section which is a real system only in the subsolidus region (below 646 °C). Two ternary invariant points (one ternary peritectic and one ternary eutectic) occur in the investigated partial system ErPO₄–NaPO₃–Er(PO₃)₃.     

Synthesis and characterization of SiO2–CrO3, SiO2–MoO3, and SiO2–WO3 mixed oxides produced using the non-hydrolytic sol–gel process

Silica-based mixed oxide xerogels, namely SiO₂–CrO₃, SiO₂–MoO₃, and SiO₂–WO₃, were prepared using the non-hydrolytic sol–gel process. The materials were synthesized using metal chloride:tetraethoxysilane (TEOS) molar ratios of 0.1:2; 0.2:2 and 0.4:2 for each metal chloride and 1:2 SiCl₄:TEOS molar ratio. All of the xerogels containing Cr, Mo or W had considerably greater surface areas than that of SiO₂. The small angle X-ray scattering experiments suggest that the surface roughness of the aggregates in SiO₂–CrO₃ is less than that of SiO₂–MoO₃ and SiO₂–WO₃. The morphological characteristics of the silica-based mixed oxide xerogels were not affected by the nature and amount of metal chloride employed in the synthesis. An irregular morphology was observed for SiO₂–CrO₃, SiO₂–MoO₃ and SiO₂–WO₃, but a lamellar structure was observed for SiO₂. X-ray photoelectron spectroscopy analysis suggests that tungsten species were preferentially distributed on the outmost part of the grain. The resulting particle diameter was shown to be lower for the mixed oxides compared to that of bare silica. Furthermore, the presence of metals (Cr, Mo and W) on silica caused a decrease in the size of the particles as the atomic radii of these metals increased. According to the Fourier transform infrared spectroscopy and Raman, Cr, Mo and W were incorporated within the silica framework.     

Ag/La0.6Sr0.4MnO3基催化剂上CH3OH和CO的完全氧化

合成了Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３、Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３／γ－ＡＩ２Ｏ３两毓催化剂,发现钙钛矿型Ｌａ０．６Ｓｒ０．４ＭｎＯ３对低浓度ＣＨ３ＯＨ或ＣＯ的完全氧化显示出相当高的催化活性,适量Ａｇ对钙钛矿型Ｌａ０．６Ｓ５０．４ＭｎＯ３基质的修使其对ＣＨ３ＯＨ或ＣＯ完全氧化催化活性获明显提高;在６％Ａｇ／２０％Ｌａ０．６Ｓｒ０．４ＭｎＯ３／γ－ＡＩ２Ｏ３催化剂 ,ＣＨ３ＯＨ完全氧化的Ｔ     

钡取代锶对Sr_3Al_(0.6)Si_(0.4)O_(4.4)F_(0.6):Ce~(3+)荧光粉的发光性能影响

采用高温固相法合成Ba取代Sr_3Al_(0.6)Si_(0.4)O_(4.4)F_(0.6):Ce~(3+)中Sr的氟氧铝硅酸锶钡(Sr_(3-x)Ba_xAl_(0.6)Si_(0.4)O_(4.4)F_(0.6):Ce~(3+))荧光粉。指出Ba/Sr固溶极限为x=0.9。由于Sr_3Al_(0.6)Si_(0.4)O_(4.4)F_(0.6):Ce~(3+)中Sr具有十配位Sr(1)和八配位的Sr(2),所以激活剂离子Ce~(3+)也具有两个不同的占位,通过Ce~(3+)的光谱结果,指出是由于Ba的掺入诱导Ce(1)~(3+)发光中心增加,减少了Ce(2)~(3+)发光中心,从而出现随着Ba/Sr比增加,粉样在400 nm激发下发光强度减小,而在460 nm激发下发光强度增强的现象。因此Sr_(3-x)Ba_xAl_(0.6)Si_(0.4)O_(4.4)F_(0.6):Ce~(3+)荧光粉是一款潜在的适合近蓝光激发的白光LED用荧光粉。