R2Fe17CNx的结构和磁性

采用适当的热处理,使碳原子和氮原子先后进入到R_2Fe(17)的结构中去。利用X射线折射和磁测量技术研究了R_2Fe_(17)CN_x的晶体结构和内禀磁性。碳、氮的加入使晶胞体和膨胀、居里温度升高、饱和磁矩增大,并加强了稀土晶位的轴各向异性。     

稀土化合物Ho2Co14Fe3的磁性分析

在分析稀土磁性常用的哈密顿中，引入了自旋－自旋偶极作用，用参数拟合的方法对Ｈｏ２Ｃｏ１４Ｆｅ３的磁化曲线进行了分析，计算结果与实验数据符合得很好，并且提示了Ｈｏ２Ｃｏ１４Ｆｅ３磁矩的突变现象。     

两个氮氧双自由基桥连的稀土一维链的晶体结构、磁性和荧光性能

选用1,2-二苯氧基乙烷取代的氮氧双自由基(BNPhOEt)与稀土金属反应,得到了2例氮氧双自由基-稀土配合物[Ln(hfac)3(BNPhOEt)]·C6H14(Ln=Tb(1)、Ho(2);hfac=六氟乙酰丙酮),其均为2p-4f一维链状结构.磁性研究表明,在配合物1和2中分别存在铁磁和反铁磁耦合.此外,对2个配...     

稀土金属化合物的结构和磁性

本文介绍了稀土金属间化合物的结构特点，通过晶体结构和稀土－３ｄ过滤金属化合物中的三种相互作用分析，解释了磁性特点，同时介绍了矫顽力的两种模型。     

氧化铈负载CuO催化材料对甲烷燃烧的催化作用

以甲烷催化燃烧为目标反应, 考察了CuO/CeO2催化材料的催化活性, 研究了催化材料中铜含量, 制备方法及焙烧温度对催化活性的影响. 结果表明, CuO/CeO2催化材料对甲烷燃烧反应呈现出较高催化活性, 适当温度下焙烧催化剂有利于提高催化剂的催化活性. 随着催化剂中氧化铜含量的改变, 甲烷完全燃烧的温度改变较大. 对于浸渍法样品, 当CuO% (质量分数)>13.0% 时, 复合物本体有CuO晶相出现, 而不是以高分散形式分布在复合物表面, 导致催化活性下降, 完全燃烧温度升高. 最佳CuO含量CuO% 约为8.0%.     

混合稀土化合物Y1—xTbxCo5＋0.1x的磁性

研究了自旋－轨道作用、晶场作用、交换作用、自旋－自旋偶极作用和Ｚｅｅｍａｎ作用，对稀土化合物Ｙｚ－ｘＴｂｘＣｏ５＋０．１ｘ的磁性实验数据进行了理论分析，理论计算结果与实验符合得较好，并进一步讨论了各种作用对磁性的贡献。     

新型稀土富铁永磁化合物NdFe10Mo2Cx的制备和磁性研究

用气－固反应将碳原子渗入到母体合金ＮｄＦｅ１０Ｍｏ２的晶格间隙位，形成稳定的化合物ＮｄＦｅ１０Ｍｏ２Ｃｘ，其晶体结构保持ＴｈＭｎ１２型方结构不变，但晶胞积增大３％左右，居里温度提高１１０Ｋ以上，且ＮｄＦ３１０Ｍｏ２Ｃｘ具有单轴各向异性，磁晶各向异性场ＨＡ达到９２３３．６ｋＡ／ｍ．结果表明，ＮｄＦｅ１０Ｍｏ２Ｃｘ具备了研制高矫顽力永磁体的内禀磁性，另外，穆堡尔谱实验表明，ＮｄＦｅ１０Ｍｏ２Ｃｘ中不同     

化合物Y1—xPrxCo5和Y1—xSmxCo5的磁性分析

用改进的哈密顿,通过参数拟合法对稀土化合物Y_(1-x)Pr_xCo_5和Y_(1-x)Sm_xCo_5的磁化曲线、自发磁化曲线及易磁化方向随温度的变化曲线进行了分析.计算结果与实验符合较好,并得到了较为合理的Y_(1-x)Pr_xCo_5二阶晶场参量数值.     

稀土双核配合物的合成与磁性

稀土离子存在于许多磁性材料中,但至今稀土双核配合物的合成及磁性研究很少,建立磁性-结构间的关系对新型分子磁性材料的设计有重要意义。稀土双核配合物的磁性研究也为研究f轨道参与磁相互作用提供第一手材料。我们曾合成了一系列以氯冉酸二价阴离子为桥联配体的过渡金属双核配合物,本文合     

Electrical Properties of Chain Microstructure Magnetic Emulsions in Magnetic Field

The work deals with the experimental study of the emulsion whose dispersion medium is a magnetic fluid while the disperse phase is formed by a glycerin-water mixture. It is demonstrated that under effect of a magnetic field chain aggregates form from the disperse phase drops. Such emulsion microstructure change affects its macroscopic properties. The emulsion dielectric permeability and specific electrical conductivity have been measured. It is demonstrated that under the effect of relatively weak external magnetic fields (～1 kA/m) the emulsion electrical parameters may change several fold. The work theoretically analyzes the discovered regularities of the emulsion electrical properties.     

CuO／CeO2和CuO／Al2O3催化剂的催化性能

本文以ＣＯ氧化为模式反应考察了ＣｅＯ２和Ａｌ２Ｏ３负载氧化铜催化剂的氧化活性，运用ＸＲＤ和ＴＰＲ技术研究了催化剂的还原性能和物相结构，结果表明：载体性质对负载ＣｕＯ催化剂的ＣＯ氧化活性有很大影响，ＣｕＯ／ＣｅＯ２催化剂活性明显高于ＣｕＯ／Ａｌ２Ｏ３催化剂．催化剂的还原特性随载体不同而不同．同时发现，热处理对催化剂铜物种的存在形式，晶粒大小、还原特性及其催化活性有明显影响，ＣｕＯ／Ａｌ２Ｏ３催化剂活性下降的主要因素是生成了活性较低的ＣｕＡｌ２Ｏ４相，而ＣｕＯ／ＣｅＯ２催化剂活性下降是由于ＣｕＯ和ＣｅＯ２发生烧结，晶粒变大     

厚膜型la2cuo4的氧敏性能

采用甘氨酸-硝酸盐法合成了La2CuO4复合氧化物,并制成厚膜型氧敏元件。结果表明,在400~700℃之间,厚膜型La2CuO4的灵敏度随着测试温度的升高而逐渐降低。La2CuO4气敏元件的灵敏度(RN2/RO2)主要由表面载流子浓度决定,随着测试温度的升高,吸附氧在粒子表面的脱附速率增大,导致空穴载流子浓度随温度的升高而降低,从而使灵敏度下降。厚膜型La2CuO4在400℃时的灵敏度最大,可以达到29.6,远大于烧结型La2CuO4的灵敏度,且厚膜型La2CuO4在400℃对于氧分压变化具有快速的响应,响应时间约为4 s。     

Magnetic Properties of the 2D-Oxides

The conditions of the existence of two dimensional magnetic oxides are reviewed from both the theoretical and experimental point of view. From the magnetic data of oxides belonging to two different structural types; the K₂NiF₄-type which occurs in Ca₂MnO₄, CaLaFeO₄, SrLaBO₄ (B = Cr, Fe, Co) and the α-NaFeO₂-type which occurs in oxides of formula ACrO₂ (A = Li, Na, K), a discussion is given of the relation between dimensionality and the magnetic behaviour.     

CuO/CeO2催化剂的催化氧化性能及其表征

用CO流动反应法 ,程序升温还原 (TPR) ,光电子能谱 (XPS)和X射线衍射Rietveld分析等技术研究了CuO ,CeO2 及CuO/CeO2 各组分催化剂。结果表明 :单组分的CuO和CeO2 对CO的氧化活性较低 ,但CuO与CeO2 形成复合氧化物后 ,其CO氧化活性明显提高 ,这可能与铜物种在CeO2 表面的价态 (Cu2 + 和Cu+ ) ,分散状态和还原性能有关。CuO在CeO2 上的负载量对铜物种在CeO2 表面形成的价态 (Cu2 + 和Cu+ )至关重要 ,CuO的负载量为 1 0 %时 ,XPS检测不到Cu2p3/2 (eV)结合能 ;当CuO的负载量为 5 0 %时 ,CuO主要以Cu2 + 和Cu+ 形式存在 ,而负载量大于 5 0 %时 ,CuO则以Cu2 + 形式存在。由于形成了CuO/CeO2 复合氧化物 ,使离子半径小于Ce4 + 的CuO进入了CeO2 晶格 ;当CuO的负载量达到 5 0 %时 ,CuO的晶粒尺寸值为最小 ( 6 1nm) ,而晶格畸变值为最大 ( 2 86× 10 - 3) ,此时 ,催化剂具有较高的表面能和最佳的CO氧化活性     

Density Functional Theory Approach to the Vibrational Properties and Magnetic Specific Heat of the Covalent Chain Antiferromagnet KFeS2

Ternary potassium-iron sulfide, KFeS₂, belongs to the family of highly anisotropic quasi-one-dimensional antiferromagnets with unusual “anti-Curie–Weiss” susceptibility, quasi-linearly growing with a rising temperature up to 700 K, an almost vanishing magnetic contribution to the specific heat, drastically reduced magnetic moment, etc. While some of the measurements can be satisfactorily described, the deficiency of the entropy changes upon the magnetic transition and the spin state of the iron ion remains a challenge for the further understanding of magnetism. In this work, high-quality single-crystalline samples of KFeS₂ were grown by the Bridgman method, and their stoichiometry, crystal structure, and absence of alien magnetic phases were checked, utilizing wave-length dispersive X-ray electron-probe microanalysis, powder X-ray diffraction, and ⁵⁷Fe Mössbauer spectroscopy, respectively. An ab initio approach was developed to calculate the thermodynamic properties of KFeS₂. The element-specific phonon modes and their density of states (PDOS) were calculated applying the density functional theory in the DFT + U version, which explicitly takes into account the on-site Coulomb repulsion U of electrons and their exchange interaction J. The necessary calibration of the frequency scale was carried out by comparison with the experimental iron PDOS derived from the inelastic nuclear scattering experiment. The infrared absorption measurements confirmed the presence of two high-frequency peaks consistent with the calculated PDOS. The calibrated PDOS allowed the calculation of the lattice contribution to the specific heat of KFeS₂ by direct summation over the phonon modes without approximations and adjustable parameters. The temperature-dependent magnetic specific heat evaluated by subtraction of the calculated phonon contribution from the experimental specific heat provides a lower boundary for estimating the reduced spin state of the iron ion.     

纳米CuO的形貌控制合成及其性能研究

The CuO nanocrystals were prepared by quick-precipitation and hydrolysis method respectively, using Cu(Ac)₂ and NaOH as starting materials. The as-prepared CuO nanocrystals were characterized by XRD, TEM, XPS, UV-Visible absorption spectroscopy and BET. The catalysis of CuO nanocrystals of different morphologies on ammonium perchlorate decomposition was investigated by thermal analysis. Results indicated the variation in temperature for NaOH addition played an important role in the shape of the CuO nanocrystals in precipitation method. Well-dispersed spherical CuO nanocrystals with an average size of 6 nm could be obtained when NaOH was added at 100 ℃ and spindle-shaped CuO nanocrystals exceeding 100 nm in diameter were obtained when NaOH was added at room temperature. Needle-shaped CuO nanocrystals could be prepared by the hydrolysis method, and the presence of small amounts of cetyltrimethylammonium bromide (CTAB) could make needle-shaped CuO well dispersed. The catalytic activity of CuO nanocrystals of different morphologies on ammonium perchlorate decomposition was high. The 2% of spherical CuO nanocrystals could make higher decomposition temperature of ammonium perchlorate decreased to 102 ℃. The exothermic quantity of decomposition was from 590 J·g^-1 up to 1 420 J·g^-1.     

CO预处理对CuO/γ-Al2O3催化剂性能的影响

采用XRD，TPR，CO吸附in-situ IR，CO氧化反应等对CuO/γ-Al₂O₃催化剂经CO处理前后的结构、组成和催化性能进行了研究。结果表明，经CO在250 ℃下处理1 h后CuO/γ-Al₂O₃催化剂中出现了分散态Cu⁺物种，该物种的产生使催化剂的活性明显提高。     

Two [Ni(dmit)2]-Compounds Showing Layered and Chain Alignments: Crystal Structures and Magnetic Properties

Two metal-dithiolene compounds with a formula of[4-ClBz-l-APy][Ni(dmit)_2](1)and[4-NO_2Bz-l-APy][Ni(dmit)_2](2,4-ClBz-1-APy = 1-N-(4'-chlorobenzyl)pyridinium,4-NO_2Bz-1-APy = l-N-(4'-nitrobenzyl)pyridinium,dmit~(2-)= 1,3-dithiole-2-thione-4,5-dithiolate) were synthesized and characterized.Two compounds crystallize in triclinic space group P1 and P1,respectively,but with different cell parameters and packing structures.The[Ni(dmit)_2]~- anions and cations of 1 form mixed column stacks along the a axis and alternately layered alignments in the crystal of 2,which are parallel to the crystallographic(110) plane.Two compounds show a similar magnetic behavior,the magnetic exchange natures are mainly antiferromagnetic,and the magnetic susceptibility data can be fitted to the simple Curie-Weiss law.For 1 and 2,the fitted Curie constants are much less than the spin-only value expected for an S =1/2 system,and the fitted Weiss constants marking magnetic interaction are also very smaller.This fact implies that the weak CurrieWeiss-type paramagnetism is not the intrinsic characteristics of two compounds.     

一维链状锰配合物的合成、结构及磁性研究

合成了邻硝基苯磺酰化丙氨酸配体2-NBS-AlaH (1)(2-NBS-AlaH=邻硝基苯磺酰化丙氨酸)及其锰的配合物[Mn(4，4′-bipy)(H₂O)₄]₂[(4，4′-bipy)₂(H₂O)₃(2-NBS-Ala)₄] (2)。通过X-射线单晶衍射测定了其结构：配体通过氢键形成了一维链状结构；配合物2中，4，4′-bipy把锰离子连成了一维链状结构。磁性研究表明，配合物由于分子间的自旋耦合呈现出弱的铁磁性。