Al2O3-SiO2系纳米粉的微观结构与红外发射特性

Al2O3-SiO2系纳米粉的微观结构与红外发射特性     

Na3AlF6-Al2O3熔盐体系中ZnFe2O4基阳极的电化学行为

研究了ＺｎＦｅ２Ｏ４基阳极在Ｎａ３ＡｌＦ６－Ａｌ２Ｏ３熔盐体系中的电化学稳定性，讨论了电极的析氧历程并得到了析氧过电位与阳极表观电流密度之间的Ｔａｆｅｌ关系式，η＝０．１２＋０．０５２ｌｏｇｉ（ｉ＝０．０１５－０．４４Ａ／ｃｍ＾２）用三角波电位扫描法测定了电极析氧过程的伏安曲线。     

精密从头算与ABEEM／MM模型对水团簇（H2O）11 9种低能结构的计算

用精密从头算方法研究了(H2O)11的9种低能异构体的性质,包括优化的几何结构、结合能、偶极矩和氢键个数等,并且得出了515-a是(H2O)11的全局最低能结构.同时,也用ABEEM/MM(atom bond electronegativity equalization method/molecular mechanics)模型研究了这些性质,与从头算的结果进行了比较,得到了相符合的结果.这显示了ABEEM/MM模型在描述中等大小的水分子团簇结构上是成功的.     

Na/Mn摩尔比对层状O2结构Liy[Li1/6Mn5/6]O2的晶体结构及化学组成的影响

层状材料;Na/Mn摩尔比对层状O2结构Liy[Li1/6Mn5/6]O2的晶体结构及化学组成的影响     

四元交互体系Li+,Na+//CO2-3,B4O72一-H2O 298 K相关系的理论预测及实验研究

采用三元体系的溶解度数据,运用多元线性回归法拟合了Li 2CO3(a),Na 2CO3(b),Li 2B4O7(c)的单盐参数、溶解平衡常数及有关的混合离子作用参数.它们的值分别为:β(o)a=-1.235 5,β(1)a=-2.654 6,Cφa=-0.004 660 7,β(0)b=-3.030 6,β(1)b=-3.023 8,Cφb=-0.290 89,β(0)c=-0.293 04,β(1)c=2.155 6,Cφc=-0.004 256 0,θLi,Na=1.041 8,θB.C=-2.630 5,ψLi,Na,C=-0.063 91,ψLi,Na,B=0.493 56,ψLi,B,C=-0.478 42,ΨNa,B,c=0.306 16,In K(Li2CO 3)=-8.962 9,In K(Na2CO3@10H2O)=3.064 6,ln K(Li2B4O 7@3H2O)=-7.356 6,ln K(Na2B4O7@10H2O)=-7.477 8.以盐的溶解平衡常数为判据,运用Pitzer方程计算了四元体系Li+,Na+//CO2-3,B4O2-7-H2O 298 K时的溶解度,并采用等温溶解平衡法,对该体系298 K时溶解度进行了实验测定,同计算值相比,二者基本吻合.     

NH3…H2O体系氢键团簇结构的从头计算方案比较

对H2O，NH3单分子以及反式线性NH3…H2O双分子团簇应用HF，DFT，MR2，CCD ，QCISD等从头计算方法在不同的基组水平上进行几何结构优化和氨—水分子间相 互作用能计算。比较实验值和计算结果表明：对氨—水体系，MP2／6-31+G^**方法 能够满足氢键N-0键长误差为0．004nm，键角∠NOH误差为1°，NH3…H2O相互作用 能△E与CCD和QCISD偏差2．1kJ／mol计算精度的要求，并有较合理的计算代价。     

精密从头算与ABEEM/MM模型对水团簇(H2O)11 9种低能结构的计算

用精密从头算方法研究了(H2O)11的9种低能异构体的性质, 包括优化的几何结构、结合能、偶极矩和氢键个数等, 并且得出了515-a是(H2O)11的全局最低能结构. 同时, 也用ABEEM/MM(atom bond electronegativity equalization method/molecular mechanics) 模型研究了这些性质, 与从头算的结果进行了比较, 得到了相符合的结果. 这显示了ABEEM/MM模型在描述中等大小的水分子团簇结构上是成功的.     

Nd(NO_3)_3-HNO_3-H_2O体系的过量吉布斯自由能和Nd(NO_3)_3-HNO_3-H_2O-HDEHP-AMSCO体系水相中各组分活度系数的计算

我们简化了混合电解质溶液过量吉布斯自由能的Pitzer公式。用此简化公式并结合我们以往的工作计算了Nd(NO_3)_3-HNO_3-H_2O体系的过量吉布斯自由能和Nd(NO_3)_3-HNO_3-H_2O-HDEHP-AMSCO体系水相中各组分的活度系数,计算值与实验值均很接近。此工作为镧系金属萃取分离进行热力学分析提供了方便。     

Al(H2O)63+水交换反应溶剂效应的量子化学团簇模型-密度泛函理论方法研究

在气相模型、极化连续模型、超分子模型和超分子-极化连续模型的基础上,采用量子化学团簇模型密度泛函理论方法,在B3LYP/6-311+G(d,p)基组水平下系统地开展了以下研究:优化得到Al(H2O)63+水交换反应的反应物、过渡态和产物构型,采用MP2方法在相同基组水平下计算得到相应的单点能,考虑零点振动能、热力学校正项和熵等参数的影响,计算得到Al(H2O)63+水交换反应的Gibbs自由能变和反应速率常数kex.计算结果表明:GP-SM//MP2-PCM和GP-SM-PCM//MP2-PCM模型得到的kex相近,并且与文献值相符,说明GP-SM//MP2-PCM模型可以充分考虑真实溶剂效应和主体溶剂效应,适用于Al(H3O)63+体系水交换反应的模拟.     

In2O3电子结构与光学性质的第一性原理计算

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法, 计算了In2O3电子结构和光学线性响应函数, 系统研究了In2O3电子结构与光学性质的内在关系. 利用计算的能带结构和态密度分析了带间跃迁占主导地位的In2O3材料的能量损失函数、介电函数、反射图谱, 根据电荷密度差分图分析了In2O3材料的化学和电学特性. 研究结果表明In2O3光学透过率在可见光范围内高达85%, 可作为优异的透明导电薄膜材料. 同时, 计算结果为我们制备基于In2O3透明导电材料的设计与大规模应用提供了理论依据, 也为监测和控制这一类透明导电材料的生长过程提供了可能性.     

醋酸离子液体[C2mim][OAc]水溶液的摩尔表面Gibbs自由能

在288.15-318.15 K温度范围内测定了不同浓度离子液体1-乙基-3-甲基咪唑醋酸盐([C₂mim][OAc])水溶液的表面张力和密度;在改进李以圭等人的溶液表面张力模型基础上,提出摩尔表面Gibbs自由能新概念,建立了摩尔表面Gibbs自由能随溶液浓度变化的线性经验方程,利用这个经验方程估算了[C₂mim][OAc]水溶液的摩尔表面Gibbs自由能,并进一步预测了该溶液的表面张力,其预测值与相应的表面张力实验值高度相关并非常相似。由此可见,摩尔表面Gibbs自由能与等张比容极其类似,可能成为预测离子液体及其溶液性质的一种新的半经验方法。在指定溶液浓度下,根据溶液的摩尔表面Gibbs自由能随温度呈线性变化的规律,得到了新的Eötvös方程,与传统的Eötvös方程相比,新Eötvös方程的每一个参数都有明确的物理意义:斜率的负值是摩尔表面熵,截距是摩尔表面焓,在指定浓度的溶液中摩尔表面焓几乎不随温度变化。     

微量热法研究载银B2 O3 -SiO2 -Na2 O玻璃对大肠杆菌的抑制作用

采用微量热法研究了载银B20,-SiO：-N％0玻璃对大肠杆菌作用的热功率输出曲线,得到了大肠杆菌在不同的抗菌剂浓度下的生长速率常数k,抑制率I等参数,定量说明了载银B2O3-SiO2-Na2O玻璃对大肠杆菌有很强的抑制作用。     

Na_3AlF_6-Al_2O_3熔盐体系中ZnFe_2O_4基阳极的电化学行为

研究了ＺｎＦｅ２Ｏ４基阳极在Ｎａ３ＡｌＦ６－Ａｌ２Ｏ３（ｓａｔｕｒａｔｅｄ）熔盐体系中的电化学稳定性,讨论了电极的析氧历程并得到了析氧过电位与阳极表观电流密度之间的Ｔａｆｅｌ关系式,η＝０．１２＋０．０５２ｌｏｇｉ（ｉ＝０．０１５－０．４４Ａ／ｃｍ２）。用三角波电位扫描法测定了电极析氧过程的伏安曲线     

Na2O或K2O对气相合成1–苯基氮杂环庚烷的CoO/SiO2-Al2O3催化剂的作用

研究了Na2O或K2O对苯胺和1,6己二醇气相合成1-苯基氮杂环庚烷的CoO/SiO2-Al2O3催化剂的作用,并采用X射线衍射、透射电子显微镜、H2-程序升温还原、NH3-程序升温脱附等技术对催化剂进行了表征.结果表明,Na2O助剂能增加催化剂的弱酸中心数,减少中强酸中心数,使催化剂的选择性得到提高.加入K2O使催化剂的弱酸中心数显著减少,并使CoO在反应过程中易于烧结,因此不利于1–苯基氮杂环庚烷的合成.     

Comparative Study of CuO Species on CuO/Al2O3, CuO/CeO-Al2O3 andCuO/La2O-Al2O3 Catalysts for CO Oxidation

CuO/Al2O3, CuO/CeO2-Al2O3, and CuO/La2O3-Al2O3 (denoted as Cu/Al, Cu/CeAl, and Cu/LaAl) catalysts were prepared by an impregnation method. CuO species and CuO/Al2O3 thermal solid-solid interaction were characterized by in situ XRD, Raman spectroscopy and H2-TPR techniques. For the Cu/Al catalyst, a CuAl2O4 phase exists between the CuO and Al2O3 layer and the CuO phase exists on the surface in both highly dispersed and bulk forms. For the Cu/CeAl catalyst, there is highly dispersed and bulk CuO on the surface, but most of the CuO has transferred into the internal layer of CeO2 as bulk CuO and CuAl2O4. For the Cu/LaAl catalyst, only bulk CuO is present on the surface of the catalyst and no CuAl2O4 is formed. The catalytic activity order for CO oxidation is Cu/CeAl>Cu/Al>Cu/LaAl. The highly dispersed CuO on the catalyst surface may be the active phase for CO oxidation. The results show that the addition of CeO2 not only promotes both the transference of CuO and the formation of CuAl2O4 but also favors the CO oxidation due to the association of highly dispersed CuO with CeO2, while La2O3 hinders the transference of CuO and the formation of CuAl2O4.     

Catalytic decomposition of CH4 over Ni-Al2O3-SiO2 catalysts: Influence of pretreatment conditions for the production of H2

This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si （4 ： 0.5 ： 1.5） catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2.     

Na3V2(PO4)2O2F的合成及其在钠离子电池中的应用

目前,合成Na3V2(PO4)2O2F(NVPF)材料的方法包括高温固相法、水热法、溶剂热法等,这些方法均不利于该材料的大规模工业化生产.本文开发了温和的低温共沉淀法合成NVPF材料,该材料首次放电容量为105.6 mAh·g-1,首次效率为90.16％.经过简单的热处理过程,可以有效去除由于液相合成带来的结晶水以及吸...     

Temperature-Dependent Electrochemical Properties and Electrode Kinetics of Na3V2(PO4)2O2F Cathode for Sodium-Ion Batteries with High Energy Density

Phosphate cathode materials are practical for use in sodium-ion batteries (SIBs) owing to their high stability and long-term cycle life. In this work, the temperature-dependent properties of the phosphate cathode Na₃V₂(PO₄)₂O₂F (NVPOF) are studied in a wide temperature range from −25 to 55 °C. Upon cycling at general temperature (above 0 °C), the NVPOF cathode retains an excellent charge/discharge performance, and the rate capability is noteworthy, indicating that NVPOF is a competitive candidate as a temperature-adaptive cathode for SIBs. Upon decreasing the temperature below 0 °C, the cell performance deteriorates, which may be caused by the electrolyte and Na electrode, based on the study of ionic conductivity and electrode kinetics. This work proposes a new breakthrough point for the development of SIBs with high performance over a wide temperature range for advanced power systems.     

Surface Engineering Strategy Using Urea To Improve the Rate Performance of Na2Ti3O7 in Na-Ion Batteries

Na₂Ti₃O₇ (NTO) is considered a promising anode material for Na-ion batteries due to its layered structure with an open framework and low and safe average operating voltage of 0.3 V vs. Na⁺/Na. However, its poor electronic conductivity needs to be addressed to make this material attractive for practical applications among other anode choices. Here, we report a safe, controllable and affordable method using urea that significantly improves the rate performance of NTO by producing surface defects such as oxygen vacancies and hydroxyl groups, and the secondary phase Na₂Ti₆O₁₃. The enhanced electrochemical performance agrees with the higher Na⁺ ion diffusion coefficient, higher charge carrier density and reduced bandgap observed in these samples, without the need of nanosizing and/or complex synthetic strategies. A comprehensive study using a combination of diffraction, microscopic, spectroscopic and electrochemical techniques supported by computational studies based on DFT calculations, was carried out to understand the effects of this treatment on the surface, chemistry and electronic and charge storage properties of NTO. This study underscores the benefits of using urea as a strategy for enhancing the charge storage properties of NTO and thus, unfolding the potential of this material in practical energy storage applications.     

碳布负载的缺氧型Na2Ti3O7纳米带阵列作为高性能柔性钠离子电池负极材料

作为锂离子电池的理想替代品,钠离子电池因具有能源储备丰富、成本低廉等优点而受到人们的广泛关注。柔性便携式电子产品的发展亟需柔性储能器件的研制。因此,发展一种廉价、高性能的柔性钠离子电池负极材料成了科研工作者的共同目标。在此项工作中,我们通过简单的水热合成和热还原法发展了一种以柔性碳布为基底,与缺氧型的Na₂Ti₃O₇纳米带(NTO)构成三维阵列结构的新型柔性钠离子电池负极材料。复合材料(R-NTO/CC)的导电性和活性位点得到提高,电化学性能也大幅提升,在200 mA·cm^-2的电流密度下,实现100 mAh·cm^-2的面积比容量,且经过200次循环后仍保留最初电容值的80%。此外,这种电极还具有优良的倍率性能,当电流密度提高到400 mA·cm^-2时,仍保持69.7 mAh·cm^-2的面积比容量,是未引入氧空位材料的三倍之多。这种三维缺氧的电极材料可有效提高载流子浓度,缩短离子传输通道,从而大幅提升电极的电化学性能。此工作为设计合成高储钠性能的新型的负极材料提供了一种实用有效的策略。