层间化合物hNB—Cu稳定性的理论研究

以分子簇为模型，用从头算方法，在６－３１Ｇ＾＊基组水平上对六方氮化硼（ｈＢＮ）进行几何全优化，再用优化构型对Ｃｕ的六方氮化硼层间化合物（ｈＮＢ－Ｃｕ）做单点计算，根据计算结果，从层间距、Ｍｕｌｌｉｋｅｎ布居、轨道相互作用、原子净电荷及前线轨道等角度分析了ｈＢＮ－Ｃｕ的电子结构及其稳定性，通过劝分析计算确认了这一层间化合物只是一个介稳结构，阐明了Ｃｕ使六方氮化硼陶瓷致密化的作用机理以及ｈＮＢ－Ｃｕ的弱抗氧化性。     

NdCl3-FeCl3-石墨层间化合物的XPS研究

通过熔盐交换法合成了ＮｄＣｌ３－ＦｅＣｌ３－ＧＩＣ,采用Ｘ射线电子能谱（ＸＰＳ）分析插入剂在石墨层间的存在形式,并测定了试样中Ｎｄ,Ｆｅ,Ｃｌ和Ｃ的相对含量。ＮｄＣｌ３－ＦｅＣｌ３－ＧＩＣ中Ｆｅ２ｐ的结合能为７１１．２０－７１０．３ｅＶ,Ｎｄ３ｄ的结合能为９８３．２０－９８３．０８ｅＶ,并发现Ｆｅ在石墨层ｅ＾３＋,Ｆｅ＾２＋形式存在。     

聚乙烯/石墨层间化合物热降解过程的TG-FTIR研究

将含磷化合物插层石墨层间化合物(GIC)用于聚乙烯(PE)的阻燃,采用氧指数(LOI)方法评价了PE/GIC的阻燃性能,并采用热分析-红外光谱联用技术(TG-FTIR)研究了PE/GIC的热降解过程,探讨了GIC的阻燃机理。研究表明,不同含磷化合物插层GIC阻燃聚乙烯的氧指数有显著差别,其中以多聚磷酸铵-GIC的阻燃效果较好,氧指数较高。TG-FTIR研究结果表明,GIC并未显著影响PE的热降解方式,但由于GIC体积膨胀所发生的氧化还原反应导致部分PE热降解提前并发生热氧化降解,促进了后期成炭的石墨化过程。     

金属石墨层间化合物的量子化学和热力学研究

采用量子化学密度泛函B3LYP方法,对碱金属、碱土金属和过渡金属石墨层间化合物(A-GIC,AE-GIC和T-GIC)进行计算.从原子净电荷、Mulliken重叠布居和轨道电子数等角度讨论了A-GIC和AE-GIC的电子结构与成键特性,初步阐明了结构与性能的关系.根据计算结果,结合热力学分析,讨论实验上尚未知的过渡金属石墨层间化合物合成的可能性.     

石墨层间化合物FeCl3-CrO3-GIC的制备及性能研究

以天然鳞片石墨、CrO₃、CH₃NO₂、FeCl₃为原料，按物质的量的比34∶1.5∶22∶1，利用化学氧化法制备出低温易膨胀、高膨胀容积的石墨层间化合物，300 ℃时膨胀容积为420 mL·g^-1，800 ℃时达到最大膨胀容积630 mL·g^-1，明显优于传统硫酸、硝酸插层的石墨层间化合物。采用SEM、EDS、FTIR、XRD、TG、VSM等技术对石墨层间化合物的组成、结构、性能进行了表征和分析。     

石墨烯吸附TiCl4分子的条件控制及光电性能的理论研究

为研究石墨烯吸附TiCl₄分子的影响因素及其光电性能,探索复合物应用于传感器及透明导电薄膜的可能性,采用第一性原理与蒙特卡罗方法研究TiCl₄气体分子在石墨烯表面的吸附条件控制与光电性能。结果表明：(1)石墨烯对TiCl₄气体分子具有较强的物理吸附作用,Cl原子吸附在其附近相距质心位置最远的碳原子顶位最稳定;(2)温度升高不利于TiCl₄气体分子吸附,气体逸度增加有利于吸附,TiCl₄气体分子插入石墨/双层石墨烯/多层石墨烯时宜将温度维持在TiCl₄沸点附近,并增加气体的压力;(3) TiCl₄的吸附对石墨烯的电子结构进行了调控,使费米能级附近的态密度显著提高,赝能隙减小,有效提高了导电性能;(4)在可见光区域,TiCl₄的吸附对体系的吸收性能影响不大,在提升透明导电薄膜导电性的同时未影响薄膜的光学性能。     

3-硝基-1,2,4-三唑-5-酮与NH3及H2O分子间相互作用的理论研究

在DFT—B3LYP／6—311 G^**水平上,求得3-硝基-1,2,4-三唑-5-酮(NTO)／NH3和NTO／H2O两种超分子体系势能面上5种全优化构型．经基组叠加误差(BSSE)和零点能(ZPE)校正,求得NTO与NH3和H2O的分子间最大相互作用能依次为-37．58和-30．14kJ／mol,表明NTO与NH3的分子问相互作用强于与H2O的作用．超分子体系中电子均由NH3或H2O向NTO转移,相互作用能主要由强氢键所贡献,由自然键轨道分析揭示了相瓦作用的本质．对优化构型进行振动分析,并基于统计热力学求得200．0～800．0K温度范围从单体形成超分子的热力学性质变化．发现由NTO和NH3形成超分子Ⅱ和Ⅲ在常温下可自发进行;而NTO和H2O只在低温下才能自发形成Ⅳ,Ⅴ和Ⅵ超分子．     

3-硝基-1,2,4-三唑-5-酮与NH3及H2O分子间相互作用的理论研究

在DFT-B3LYP/6-311＋＋G**水平上, 求得3-硝基-1,2,4-三唑-5-酮(NTO)/NH₃和NTO/H₂O两种超分子体系势能面上5种全优化构型. 经基组叠加误差(BSSE)和零点能(ZPE)校正, 求得NTO与NH₃和H₂O的分子间最大相互作用能依次为－37.58和－30.14 kJ/mol, 表明NTO与NH₃的分子间相互作用强于与H₂O的作用. 超分子体系中电子均由NH₃或H₂O向NTO转移, 相互作用能主要由强氢键所贡献, 由自然键轨道分析揭示了相互作用的本质. 对优化构型进行振动分析, 并基于统计热力学求得200.0～800.0 K温度范围从单体形成超分子的热力学性质变化. 发现由NTO和NH₃形成超分子II和III在常温下可自发进行; 而NTO和H₂O只在低温下才能自发形成IV, V和VI超分子.     

Fe/膨胀石墨插层复合物的简易制备与电磁特性研究

以膨胀石墨和硫酸亚铁为前驱物,采用一步还原法得到Fe/膨胀石墨(Fe/EG)插层复合物.并用SEM、XRD、网络矢量分析仪等测试仪器分别研究了Fe含量(wFe)对Fe/EG插层复合物的形貌、结构、微波电磁和吸波性能的影响.结果表明:改变插层剂Fe的含量能有效地调控Fe/EG插层复合物的微波电磁与吸收特性.随wFe在27.5wt%～71.5wt%范围内增大,Fe/EG插层复合物的介电常数在wFe=27.5wt%时达到最大值,磁导率呈现多重共振现象,微波吸收性能逐渐增强.这种优异的微波吸收特性归功于Fe/EG插层复合物增强的电磁匹配和磁共振损耗.     

Acceptor-type graphite intercalation compounds and new carbon materials based on them

The problems of synthesis and study of the physicochemical properties of graphite intercalation compounds (GIC) formed upon insertion of various molecules into the interplanar space of graphite are considered. Binary and ternary intercalation compounds with protonic acids (HNO₃, CH₃COOH, H₃PO₄, H₂SO₄, etc.) are described. The results of systematic research into graphite intercalation by potentiometry, calorimetry, powder X-ray diffraction, conductivity measurements, DTA, chemical analysis, and other methods are given. These results underlie elucidation of the characteristic and peculiar features of acid insertion into graphite. The physicochemical properties and practical applications of GIC and low-density carbon materials are analyzed. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1699–1716, August, 2005.     

Theoretical model and experimental study of pore growth during thermal expansion of graphite intercalation compounds

Summary A new technique, which allows one to simultaneously follow the mass and volume of graphite intercalation compounds (GICs) during thermal transformation into expanded graphite, was developed. This enabled us to elucidate the mechanism for the thermal expansion of GICs and formulate a quantitative model for the process. Effective activation parameters of the thermal decomposition of new GICs were obtained by using non-isothermal kinetics procedure. Thermal decomposition was described as a break of intermolecular bonds followed by diffusion.     

A study on the formation mechanism of graphite fluorides by Raman spectroscopy

Raman spectra were measured of highly fluorinated graphite samples prepared at room temperature, 380 and 515 °C. C_xF prepared at room temperature showed a novel downshifted band at 1555–1542 cm⁻¹ along with G band at 1593–1583 cm⁻¹. Similar behavior is also observed for samples prepared at 380 and 515 °C at early stages of fluorination, after which the Raman shifts completely disappeared. Raman spectra as well as X-ray diffraction (XRD) analysis suggest that graphite fluorides, (CF)_n and (C₂F)_n are formed via fluorine-intercalated phase with planar graphene layers.     

The lithium intercalation into graphite from electrolyte and from solid lithium

The values of diffusion coefficient (D) of lithium in thermoexpanded graphite during cathodic intercalation from aprotic electrolyte, and upon direct contact with lithium metal, are measured. In the first case galvanostatic switch-on curves were registered, in the second case the method of x-ray diffraction was used. In the both cases D was close to 10^-10 cm²/s.Presented at the 3rd International Meeting "Advanced Batteries and Accumulators," June 16th–20th 2002, Brno, Czech Republic     

Analogies and differences between calcium-based and europium-based graphite intercalation compounds

An original method using lithium-based liquid alloys has been developed, allowing studies on bulk graphite intercalation compounds with calcium and europium. We showed that binary and ternary compounds belonging to graphite-lithium-calcium and graphite-lithium-europium systems are synthesized in both cases for equivalent reaction conditions but amazingly with many different structural and physical properties. Concerning CaC₆ and EuC₆, even if their 2D unit cells are hexal, their c-axis stacking sequences lead to different symmetries. Regarding kinetical data, formation mechanisms of these graphite intercalation compounds appear comparable however different, with a first common step before differenciation in the intercalation mechanism. Obviously, their physical properties are strongly different due to the nature of the intercalated metallic element. So, the different ternary compounds from these systems also show very considerable differences concerning their electronic properties: complex magnetic ordering for Eu-based ternary GIC and superconducting behaviour for Ca-based ternary GIC. However, common points are highlighted.     

Thermal behaviour of graphite intercalation compounds with oxide of difluoride of phosphoryl

We present in this paper the thermal analysis (calorimetry, TG and DSC) of the first stage P₂O₃F₄ graphite intercalate compound in atmospheric pressure and high pressure. By heating we obtain always exfoliation phenomenon. The heating of exfoliated, graphite shows an important oxidation resistance in comparison with another exfoliated graphite. This oxidation resistance has been studied also by thermal analysis like TG, in oxygen atmosphere. Carbon foil rebuilding from exfolied graphite keeps these interesting antioxidation properties.     

X-ray photoelectron spectroscopy study of intercalated compounds of fluorinated graphite C2FxBr0.01·yCH3CN

The energy level structure of fluorinated graphite intercalation compounds C₂F_xBr_0.01·yCH₃CN (x = 0.49–0.87, y = 0.084–0.136) has been studied by X-ray photoelectron spectroscopy providing the information on the electronic structure of compounds in question. The analysis of variations of the binding energy of core levels C1s, F1s, and O1s opens the possibility to explore the nature of the chemical bond C-F in the fluorographite matrix with a varying degree of fluorination, as well as to model the structure of these compounds. The examination of decomposition results of spectra into components has revealed the occurrence of C-F fragments, carbon atoms not bonded directly to fluorine atoms, and “graphite-like” areas, whose contribution to the overall structure increases with the degree of matrix fluorination decreasing. The presence of oxygen was considered from the viewpoint of surface phenomena characteristic of low-temperature carbon materials.     

Balance between reversible and irreversible processes during lithium intercalation in graphite

The effect of the measurements’ speed on reversible and irreversible processes occurring during intercalation and deintercalation of lithium in graphite out of a 1 M LiClO₄ solution in a propylene carbonate-dimethoxyethane mixture is studied by the chronopotentiometry and cyclic voltammetry methods. Dependence of reversible and irreversible capacity on the potential scan rate during potentiodynamic measurements is shown to be quite involved. Lithium diffusion coefficients in graphite are calculated by different methods.