膨胀石墨制备方法的研究进展

综述了膨胀石墨制备方法的研究现状,重点阐述了两种常用制备方法:（1）以天然鳞片石墨为原料,先经氧化制得可膨胀石墨,再经膨化处理得膨胀石墨;（2）将氧化和膨胀同时进行的爆炸法。分析了不同制备方法的优劣。并对膨胀石墨的制备工艺进行了展望。参考文献48篇。     

Estimate of polarization components in oxygen reduction process on expanded natural graphites and acetylene carbon black in acid and alkaline electrolytes

The polarization curves of oxygen reduction in gas diffusion electrodes of expanded natural graphites (ENG, prepared from graphite intercalation compounds synthesized by intercalation of sulfuric and nitric acids into natural graphites GAK-3 and GT-1) and acetylene carbon black in acid (pH 0.6) and alkaline (3 M KOH) electrolytes were analyzed. The transfer coefficients and oxygen reduction exchange currents on ENG and acetylene carbon black were estimated. The experimental polarization curves were described well with the derived semi-empirical equations.     

Electrical Conductivity of Hydrophobized Electrodes Fabricated from Thermally Expanded Graphite and Their Activity in Electroreduction of Oxygen

Intercalation compounds of GT-1 and GAK-3 graphites were electrically synthesized in concentrated sulfuric and nitric acids. Porous composite samples based on thermally expanded graphite produced from electrochemically synthesized GT-1 graphite hydrosulfate, chemically synthesized GSM-1 graphite nitrate, and fluoroplastic-4D (1–15 wt %), with a volume density of 650–1090 g l^?2, were fabricated and studied.     

石墨及石墨/双马来酰亚胺减摩树脂复合材料的XRD研究

利用X射线衍射对鳞片石墨、可膨胀石墨、膨胀石墨和纳米石墨薄片以及石墨 /双马来酰亚胺、纳米石墨薄片 /双马来酰亚胺减摩复合材料进行了研究,探讨它们之间在结构上的关系以及以复合材料中双马来酰亚胺预聚体对石墨层间距的影响.实验结果表明:可膨胀石墨中插层剂的插入除了增大石墨层间距外,还减小相邻插层剂未插入的石墨层间距;膨胀石墨的结构除了保留强度很弱的石墨特征峰外,还有大量强度极其微弱、层间距大小不一的峰;超声波对膨胀石墨的结构有整合、均匀化作用;双马来酰亚胺预聚体不能插入鳞片石墨层间,而能插入纳米石墨薄片的层间.     

可膨胀石墨催化合成乙酸苄酯

可膨胀石墨作为一种重要的非金属材料已广泛应用于各工业领域 ,将其作为有机质反应催化剂的研究尚不多见[1～ 3] 。工业上 ,乙酸苄酯常是以浓Ｈ2 ＳＯ4、对甲苯磺酸等质子酸作催化剂由乙酸和苄醇制得[4] ,但此法腐蚀设备 ,污染环境 ,且副反应多。近年来 ,为了寻找对设备腐蚀性小的酯化反应催化剂进行了一些研究 ,如曾报道的酯化反应催化剂有 :四氯化锡复合物[5] 、复合固体超强酸[6] 、稀土硫酸盐[7]等。本文报道可膨胀石墨催化乙酸苄酯的合成 ,与其它催化剂相比 ,具有催化活性高 ,反应温度低 ,反应时间短 ,收率高 ,易分离及再生处理简单等…     

Synthesis,Properties, and Dispersion of Few‐Layer Graphene Fluoride

We have fluorinated few‐layer graphene (FLG) by using a low‐temperature fluorination route with gaseous ClF₃. The treatment process resulted in a new graphene derivative with a finite approximate composition of C₂F. TEM studies showed that the product consisted of thin transparent sheets with no more than 10 fluorographene layers stacked together. Spectroscopic methods revealed a predominantly covalent nature of the C? F bonds in the as‐synthesized product and we found no evidence for the existence of so‐called “semi‐ionic” C? F bonds, as observed in bulk C_xF. In contrast to the case of graphite and typical (thick) expanded graphites, fluorination of FLG did not lead to the intercalation of ClF₃ molecules, owing to the lack of a 3D layered structure. The approximate “critical” number of graphene layers that were necessary to form a phase of intercalated compound was estimated to be more than 12, thus providing a “chemical proof” of the difference between the properties of few‐layered graphenes and bulk graphites. Fluorographene C₂F was successfully delaminated into thinner layers in organic solvents, which is an important property for its integration into electronic devices, nanohybrids, etc.     

Graphites from the Zavalie deposit as active materials for lithium-ion batteries

We study the utility of standard graphites (GAK-2, GL-1, EUZ-M, and others) produced by the Zavalie Integrated Graphite Plant (ZGP) as active materials in lithium-ion batteries (LIBs). The structure and main electrochemical characteristics of these graphites are studied for choosing the best type of graphite and evaluating its utility for LIB production. The electrochemical characteristics of the best ZGP graphites and graphite for batteries produced by Superior Graphite Co. (USA), a worldwide leader of the graphite industry, are compared. Some tendencies in the effect of the structure and particle-size distribution on the electrochemical characteristics of graphite electrodes are determined. EUZ-M graphite modified by tin with amorphous carbon is prepared. The reversible capacity of this graphite in the cell against LiCoO₂ exceeds 400 mA h/g. The increased reversible capacity is due to the contribution of components having higher specific parameters; the cycling stability is due to the core-shell structure.     

Influence of phosphorus‐grafted expandable graphite on the flame‐retardant property of UHMWPE composite

In this paper, an efficient flame retardant, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was covalently grafted onto the surface of expandable graphite (EG). The resultant DOPO‐grafted expandable graphite (EG‐g‐DOPO) was characterized by Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and X‐ray photoelectron spectroscopy (XPS), respectively. The thermal stability of EG‐g‐DOPO was also evaluated by thermogravimetric analysis (TGA). Moreover, a series of flame‐retardant ultra‐high‐molecular‐weight polyethylene (UHMWPE) composites with various concentrations of EG‐g‐DOPO were prepared and evaluated. The results show that the UHMWPE composite with 20 wt% EG‐g‐DOPO possesses a satisfactory UL‐94 flame‐retardant grade (V‐0) and a high limiting oxygen index (30.6%). The residual char of the UHMWPE composite with higher EG‐g‐DOPO concentration shows more compact and integrated, providing an efficient barrier for heat release.     

Conductive mechanism of polymer/graphite conducting composites with low percolation threshold

Preparation of the conducting composites of polystyrene/expanded graphite via in situ polymerization and investigation of the conductive mechanism were carried out. They are characterized by high conductivity and a low percolation threshold. The electrical conductivity reached 10^?2 S/cm with 3.0 vol % expanded graphite content, whereas the percolation threshold was 1.0 vol %. Optical micrographs revealed the heterogeneous distribution of the graphite particles and the formation of a conductive network in the polymer matrix. A model of primary particle was proposed to interpret the conductive phenomena. The primary particle is the basic conductive unit in the composites that comprises three of the following parts: the graphite particle, the compact‐adsorbed layer, and the wrapping shell. Our model was also used to explain the experimental data in our previous studies on nylon‐6/expanded graphite composites. A low percolation threshold of conducting composites can be also explained according to the model of the primary particle. Furthermore, the theoretical line of conductivity versus primary particle content calculated from the revised Flory's theory fits the experimental data well. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 954–963, 2002     

X-ray photoelectron study of the surface of expanded and expandable graphite

Based on analysis of the x-ray photoelectron spectra of expandable graphite obtained in hydrolysis of graphite bisulfate and expanded graphite obtained upon thermolysis of intercalated graphite compound with trifluoroacetic acid, we determine the composition of the surface layer of these materials and we suggest a structure for the functional groups present in it.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 350–354, July–August, 1992.     

All‐Polystyrene 3D‐Printed Electrochemical Device with Embedded Carbon Nanofiber‐Graphite‐Polystyrene Composite Conductor

Carbon nanofibres (CNFs) and graphite flake microparticles were added to thermoplastic polystyrene polymer with the aim of making new conductive blends suitable for 3D‐printing. Various polymer/carbon blends were evaluated for suitability as printable, electroactive material. An electrically conducting polystyrene composite was developed and used with commercially available polystyrene (HIPS) to manufacture electrodes suitable for electrochemical experiments. Electrodes were produced and evaluated for cyclic voltammetry of aqueous 1,1’‐ferrocenedimethanol and differential pulse voltammetry detection of aqueous Pb²⁺ via anodic stripping. A polystyrene/CNF/graphite (80/10/10 wt%) composite provides good conductivity and a stable electrochemical interface with well‐defined active geometric surface area. The printed electrodes form a stable interface to the polystyrene shell, give good signal to background voltammetric responses, and are reusable after polishing.     

Einfluß von Gitterstörungen des Graphits auf die Bildung von Graphithydrogensulfat

Influence of Lattice Defects of Graphite on the Formation of Graphite Hydrogensulfate Various natural and synthetic graphites were oxidized with chromic acid in sulfuric acid to the 1st stage of graphite hydrogensulfate with the intent of determining the inhibition of intercalation by lattice defects. More oxidant than required by stoichiometry is consumed because slow total oxidation to CO₂ is superimposed even at room temperature. The activation energy for total oxidation is reduced by lattice defects. With some graphites, separation of the intercalation reaction from total oxidation was accomplished using calorimetry. The reaction enthalpy in the oxidation of well-crystallized graphites to the graphite salt is ?3.05 kJ/mol C.     

石墨与聚苯乙烯的纳米复合过程研究

石墨具有电导率高、化学稳定性好等优点 ,被广泛应用于聚合物 石墨复合导电材料[1～ 3] .石墨作为聚合物导电填料一般以粉末形态居多 .用粉末状石墨填料往往需要较高的填充量才能得到理想的导电性能 .石墨也可以制备成膨胀石墨 ,将它与聚合物复合 ,可以大幅度降低石墨的填充量 .如一般粉末状石墨填料与聚合物复合制备的导电材料其逾渗阀值为 1 5 %～ 2 0 % ,电导率达到 1 0 -4 ～1 0 -7Ｓ ｃｍ[4 ] ;而若采用膨胀石墨方法 ,逾渗阀值则低于 3% ,电导率可达到 1 0 -2 Ｓ ｃｍ以上[5～ 7] .Ｐａｎ等[7] 报道用膨胀石墨与聚合物复合得到纳米复合…     

Stability and Reactivity of the Active Assemblies in Modified Graphites Characterized by TPD and TPH

Synthetic graphites, as prepared and modified by sulphonation or acetylation, were doped by Fe-, Co-, Ni- and Ca-nitrates. Temperature Programmed Desorption (TPD) and Temperature Programmed Hydrogenation (TPH) were applied to characterize thermal stability and reactivity of the active assemblies formed on the matrix surface. The functional groups lowered the reactivity of the graphites. Thermally less stabile carboxylic groups decomposed with formation of secondary groups giving more reactive material. Fe containing as well as sulphonated graphites showed a much lower reactivity than the others. Synergistic effects of Co/Ca and Ni/Ca were confirmed in the graphite materials. This revised version was published online in July 2006 with corrections to the Cover Date.     

Non-destructive determination of dysprosium in graphites by neutron activation analysis

Natural graphites, graphite components, spectral and reactor grade graphites have been analyzed non-destructively for dysprosium by neutron activation and γ-spectrometry using^165m Dy (1.2 min) and¹⁶⁵Dy (2.3 hr). In four samples the determined Dy content was in the range 1.48 to 0.039 ppm. The deviation was ±18%. The limit of lower detection of the applied method amounts to 0.01 μg Dy, depending on the background contributed by other impurities.     

Cross-linked starch nanoparticles stabilized Pickering emulsion polymerization of styrene in w/o/w system

Here, we present a method to synthesize expandable spherical polystyrene beads containing well-dispersed water microdroplets. The beads, 2–3 mm in diameter, were prepared through surfactant-free Pickering emulsion polymerization in water-in-oil-in-water (w/o/w) system using cross-linked starch nanoparticles (CSTN) as emulsifier. The CSTNs were in situ surface-modified by styrene maleic anhydride copolymer as confirmed by infrared spectroscopy and contact angle analysis. The entrapped water microdroplets with the average size of 3–4 μm were shown to be surrounded by a dense layer of the CSTN. The number droplet density as well as water encapsulation efficiency in the polystyrene beads increased with the CSTN concentration. Furthermore, regardless of CSTN content, all samples exhibited high encapsulation stability of over 68 % after 3 months. These characteristics along with good expansion behavior suggest the synthesized beads as expandable polystyrene containing water as a green blowing agent.     

Sorption of Oil by Swollen Graphite: Contributions of Specific Surface Area and Specific Volume

Sorption of heavy oil by swollen graphites obtained from residual graphite hydrosulfate at 300- 900°C was studied. The dependence of the sorption capacity for oil on the specific surface area and specific volume of the swollen graphite sorbent was analyzed.     

Effect of the Brush Structure on the Degradation Mechanism of Polystyrene–Clay Nanocomposites

Summary: Pyrolysis‐GC‐MS and TGA‐FT‐IR methods have been used to perform a comparative degradation study of polystyrene and a polystyrene–clay composite. An abnormally high yield of α‐methylstyrene has been detected for the composite. This and other differences in degradation products have been explained by enhanced intermolecular interaction of the grafted PS chains, forming a brush structure. A conceptual model of the process has been suggested.

GC pyrograms of virgin PS (A) and PS–clay composite (B) pyrolyzed at 500 °C (1: styrene; 2: 2,4‐diphenylbut‐1‐ene; 2′: dimer derivatives; 3: 2,4,6‐triphenylhex‐1‐ene; 3′: trimer derivatives; 4: α‐methylstyrene).     

氟化石墨的电化学性能研究

对系列氟化石墨及其作为碱性电池正极添加剂的电化学性能进行了研究,考察了氟化石墨作为电极活性材料及用作添加剂时电池的放电行为以及氟化石墨的氟化程度和电极中氟化石墨的含量对电池的放电性能的影响.研究了MnO₂中添加氟化石墨后对电极循环性能的影响,并用XRD比较了几种不同碳材料与氟化石墨的结构特点及MnO₂电极放电前后的状态变化,初步探讨了氟化石墨改善二氧化锰电化学性能的作用机制.     

Synthesis,structure and properties of fluorinated graphite

Fluorine-graphite intercalation compounds, C₂F to C₁₆F were synthesized by various methods. C-F bonds range from ionic to semi-covalent. These properties of C-F bonding give to fluorinated graphite metallic conductivity, higher hydrophilicity than graphite and high reduction potential. The c-axis and in-plane structures are governed by C-F bonding, fluorine intercalation rate and host graphites.