Raman spectral studies of Zr4+‐rich BaZrxTi1−xO3(0.5⩽x⩽1.00) phase diagram

This paper reports a systematic study of the composition and the temperature‐dependent‐Raman spectra of Zr⁴⁺‐rich BaZr_xTi_1−xO₃ (BZT) ceramic compositions (0.50⩽x⩽1.00). On the basis of the dielectric behavior of Zr rich BZT ceramics, the observed relaxor behavior has been hypothesized as a result of increasing long‐range interactions of nanosized, Ti⁴⁺‐rich polar regions in a Zr⁴⁺‐rich nonpolar matrix. Beyond an optimum concentration of BaTiO₃ (BT) in the nonpolar matrix of BaZrO₃ (x⩽0.75), a critical size and density of the polar regions is reached when the polar clusters start showing the relaxor like behavior, which finally show classical relaxor behavior for compositions with x = 0.5 and 0.6. This hypothesis is strongly supported from the Raman data on Zr‐rich BZT presented in this paper. Well‐defined BT Raman spectra for 5% BT in BZT composition were recorded, which followed completely up to the 50% Ti addition in the BZT samples. The temperature‐dependent Raman spectra collected on the BZT ceramics far beyond the dielectric transition temperatures supported the existence of the nano‐polar BT regions, like in typical relaxor samples. The full width at half‐maximum (FWHM), integrated intensity of the peaks in the Raman spectra has been analyzed to further support the conclusions. Copyright © 2008 John Wiley & Sons, Ltd.     

高温高表面氧化铝新材料的制备化学研究——La、Ba共添加对氧化铝热稳定性的影响

本文用镧、钡共同添加并使用溶胶-凝胶法制得改性氧化铝。详细研究了在保持 La含量为 5.2wt％时, Ba添加量的改变对氧化铝热稳定性的影响。实验结果表明镧、钡元素的共添加能大大增加氧化铝的热稳定性,从而使氧化铝在高温下保持高比表面积。体相中同时添加 5.2wt％ La和 2wt％ Ba以及 5.2wt％ La和 7wt％ Ba能使氧化铝保持较好的热稳定性,样品经 1100℃煅烧 20h后,比表面分别达 100.8m2· g-1和 92.3m2· g-1。通过对添加物与氧化铝保持高温高表面能力的内在联系的探讨,得出 Ba、 La元素的添加提高氧化铝热稳定性的原因主要表现在两方面：一是抑制氧化铝的微孔烧结速度;二是阻止了氧化铝向α相的转变。     

AG50W-x8树脂分离去除钡的多原子离子对电感耦合等离子体质谱法测定稀土元素的质谱干扰

采用AG50W－x8阳离子交换树脂,以HNO3作为梯度淋洗剂,可有效地分离Ba和稀土元素,实验表明：以2mol/L HNO3淋洗时,99．5％的Ba被分离去除;以5mol/L HNO3淋洗时,稀土的回收率在96－110％之间。标准参考物质的分析结果显示测定值与标准值十分接近,表明AG50W－x8阳离子交换树脂分离可有效地去除Ba元素的多原子离子（BaO^ ,BaOH^ )对ICP－MS法测定稀土元素测定的质谱干扰,该方法准确,可靠。同时,为准确测定Eu提供了一条新的途径。     

Oxidative Dehydrogenation of Propane to Propene over Barium Promoted Ni-Mo-O Catalyst

Oxidative dehydrogenation of propane to propene was investigated over Ba- promoted Ni_0.9MoO₄ catalysts (molar ratio of Ba/Mo: 1%, 3%, 6%, 9%, 12%, 15%). The selectivity for propene increases with the increasing number of basic sites on the catalyst, and molybdenum ions play an important role in propane activation. No significant deactivation of the 6% Ba- Ni_0.9MoO₄ and Ni_0.9MoO₄ at 773 K for 80 h and for 40 h, respectively, appeared, indicating that the 6% Ba- Ni_0.9MoO₄ has great advantage over the Ni_0.9MoO₄. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ba0.5Sr0.5Co0.8Fe0.2O3-δ透氧膜反应器在丙烷氧化脱氢反应中的应用

工业上一般采用丙烷热裂解脱氢反应生产丙烯. 该反应通常在高温(＞700 ℃)下进行,催化剂容易积碳. 而且,由于反应受到热力学平衡的限制,丙烯的选择性也不很高. 近年来,以廉价空气和丙烷为原料的丙烷氧化脱氢(PODH)反应为丙烯的生产提供了另外一条途径,且已引起广泛的关注. 在PODH反应中,一般认为晶格氧(O2-)参与丙烷的选择氧化,而其它氧物种(O-,O-2等)导致丙烷的完全氧化[1]. 钙钛矿结构的混合导体透氧膜是同时具有氧离子导电性和电子导电性的一类材料. 在高温下,当膜两侧存在氧浓度梯度时,氧以氧离子的形式通过氧缺陷进行传导,同时以电子的反向传输来完成传输回路[2]. 这种透氧机理使得混合导体透氧膜在理论上对烷烃氧化反应具有一定的催化活性. 作为膜反应器材料,这类混合导体透氧膜已成功地应用于甲烷部分氧化(POM)反应[3]. 但迄今为止,还没有文献报道这种膜反应器在PODH反应中的应用. 组成为Ba0.5Sr0.5Co0.8Fe0.2O3-δ的钙钛矿膜材料是本研究组开发的一类具有高透氧量、高稳定性的新型透氧膜材料. 本文尝试将该材料制备的膜反应器用于PODH反应,同时研究了PODH反应对膜透氧量的影响.     

Evaluation of polyblends of cottonseed protein and polycaprolactone plasticized by cottonseed oil

Recently, there has been an increasing trend toward replacing conventional fossil-based plastics with bioplastics that are eco-friendly and biodegradable. In this work, blends of polycaprolactone (PCL) and cottonseed protein plasticized with cottonseed oil were made and analyzed for their mechanical, adhesive, and thermal properties. The addition of water-washed cottonseed meal (WCSM) to PCL increased the Young’s modulus but decreased the tensile strength and elongation-at-break of PCL. The addition of cottonseed oil to the PCL/WCSM blend kept the tensile strength about the same but enhanced the elongation. The PCL blends with WCSM and cottonseed protein isolate gave about the same mechanical properties, both somewhat better than the PCL/soy protein isolate blend. As plasticizers, cottonseed oil performed slightly better than coconut oil, both better than poly(ethylene glycol). The addition of WCSM and cottonseed oil (up to a PCL:WCSM:plasticizer ratio of 60:40:20) did not change the adhesive performance of PCL on fiberboard. Thus, the combination of PCL/cottonseed protein/cottonseed oil seems to be a viable bioplastic, and one possible application for this material may be in the hot melt adhesive area.     

Deconvolution of pure component FT‐Raman spectra from thermal emission of barium sulfate and graphite samples using the BTEM algorithm

Band‐target entropy minimization (BTEM) was applied for the extraction of pure component Raman spectra from samples exhibiting a significant thermal background due to sample emission. In this method, singular value decomposition was first used to calculate the right singular vectors of the spectroscopic data matrix. Then the non‐noise right singular vectors were examined for localized spectral features, which were subsequently used for spectral recovery. These local features were targeted with the BTEM algorithm to recover the pure component Raman spectra. Accordingly, the interfering thermal background was removed. This method of analysis is applied to graphite and barium sulfate Raman spectroscopic data. Copyright © 2006 John Wiley & Sons, Ltd.     

Raman scattering studies on nanocrystalline BaTiO3 Part II—consolidated polycrystalline ceramics

BaTiO₃ dense ceramics with different grain sizes from 5.6 µm down to 35 nm were thoroughly studied by Raman spectroscopy. The temperature characteristics of optical phonons were compared with those obtained for powders. The micrograined ceramic revealed the well‐known spectrum profiles and transitions, typical for bulk BaTiO₃. On the other hand, the Raman spectra obtained for a nanograined ceramic with an average grain size of 35 nm revealed a tetragonally distorted pure BaTiO₃ phase showing a diffused phase transition behaviour with respect to temperature. Abnormality of phonon damping characteristics for the nanograined ceramic was demonstrated through comparison with powders with various crystallite sizes and the micrograined ceramic. The Curie temperature of the nanograined ceramic was estimated to be 105 °C from the temperature characteristic of a sharp peak at 307 cm⁻¹, which is one of the most specific tetragonal features for bulk BaTiO₃. In the present study, local stabilization of the tetragonal phase in ultra‐fine grains was experimentally demonstrated from comparison between the Raman spectroscopic results for powders and ceramics prepared through microemulsion‐mediated synthesis. Rather long phonon mean free paths can exist even in such ultra‐fine grains, but the phonon characteristics originating from various grains are diffused mainly because of the effect of internal stress. Copyright © 2007 John Wiley & Sons, Ltd.     

Morphologies of barium chromate controlled by carriers in an emulsion liquid membrane system

Morphology‐control of barium chromate has been studied in emulsion liquid membrane system. This system consists of Span80 as surfactant, N7301 or TBP as carrier, and kerosene as solvent. When BaCl₂ solution was used as internal‐aqueous phase and N7301 as carrier, the morphology of products can be varied from crystal wafers to crystal rods. X‐ray diffraction and transmission electron microscopy were used to characterize the structure and morphology. A synthetic mechanism has been proposed and the optical properties of the products were also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)