Factors of large graphite crucible life

Production methods used to prepare graphite crucibles with high operating properties are considered: use as a filler of good graphitizing acicular coke, vibration molding of the original coke mix, use of production cycles for impregnation with medium temperature coal-tar pitch — firing, firing of compacted billets in metal containers, graphitization of fired billets in graphite cylinders. The last two production methods make it possible to reduce the temperature drop throughout the volume of a billet during heat treatment, and as a consequence to reduce crack development to a minimum as a result of reducing thermal stresses. All of the production methods recommended may be entirely accomplished in existing electrode plants and may be used to increase markedly the quality crucible graphite. It is possible to achieve a quality for these materials at the best world level. Translated from Novye Ogneupory, No. 8, pp. 28–33, August 2008.     

Evaluation of the possible use of carbon nanofiller for manufacturing silicided objects

Silicided graphites, prepared by SGP technology, using a graphite nanofiller fraction of less than 100 μm, are promising materials no worse in properties than leading analogs of overseas firms. Nonetheless, in view of the available raw material base for carbon materials rapid evaluation methods are required for the quality of graphites used in the manufacture of silicided objects based on them. Volumetric reaction makes it possible to establish quite rapidly the suitability of test carbon material for manufacturing silicided objects based on them without recourse to compaction, firing, machining, and siliciding shaped objects. X-ray structural data for the degree of graphitization of carbon material γ, and also a change in its structural characteristics (La and Lc) during reaction with silicon may be additional criteria for the choice of graphite filler.     

Neuere Entwicklungen und Perspektiven auf dem Gebiet des technischen Kohlenstoffs

New developments and outlook for technical carbon. The present world production of technical carbon amounts to 20 Mio. t/a (metallurgical coke as well as petroleum and pitch coke not included). More recent developments in the field of technical carbon are discussed in detail. Topics covered include: production and utilization of technical carbon and graphite products in metallurgy; recent advances in the use of carbon black as reinforcing material for car tyres; the significance of activated carbon for waste gas purification including the recovery of valuable materials; high-performance materials from carbon such as carbon fibres, carbon composites, and full-matrix carbons; synthesis of diamond for technical applications; preparation of diamond or diamond-like films by carbon vapor deposition; structure, preparation, and properties of fullerite, a new form of carbon, and conceivable future applications.     

高导热石墨材料微观结构与其导热性能的关系研究

考察了以膨胀石墨为原料制备的高导热炭材料（高导热石墨块、高导热石墨片）与以中间相沥青为原料制备的高导热炭材料（高导热石墨膜）在微观结构及导热性能上的差异。研究表明：由中间相沥青为原料制备的高导热石墨膜的石墨化度较高、La和Lc更大。高结晶石墨块、高导热石墨片、高导热石墨膜的热导率由高到低的顺序为：高导热石墨膜〉高导热石墨块〉高导热石墨片。     

Production of Polikon carbon-filled conducting materials

The effect of disperse graphite on the kinetics and thermodynamics of formation of an ion-exchange matrix was investigated and the basic parameters for production of Polikon K carbon-filled material were selected. The effect of the filler on crosslinking and the yield of finished oligomer was established. Incorporation of colloidal graphite changes the dielectric properties of Polikon K material by increasing its conductivity. __________ Translated from Khimicheskie Volokna, No. 1, pp. 52–54, January–February, 2008.     

Structure and conductivity of carbon materials produced from coal pitch with carbon additives

Attention focuses on the structure and electrical conductivity of carbon materials obtained by the carbonization of coal pitch in the presence of additives (nanotubes, graphite foam, and graphite), at temperatures up to 900°C. In some cases, ultrasonic mixing is used on introducing the additives to the pitch. Ultrasonic mixing is found to change the properties of the pitch and affect the properties of the carbon material produced. In particular, the proportion of carbon with an ordered structure is increased; the electrical conductivity at temperatures below 40 K is increased; and the energy barrier E _g between individual crystallites is reduced almost fourfold. At higher temperatures, the electrical conductivity is practically unchanged. Adding nanotubes to the pitch reduces the content of ordered carbon structures in the carbon material produced and lowers its electrical conductivity. Adding graphite foam and graphite to the pitch increases the order and electrical conductivity of the carbon material produced and lowers the energy barrier E _g between individual crystallites in the samples. The electrical conductivity of all the carbon materials below 16 K is described by the characteristic formula for fluctuation-induced tunneling conduction. This indicates that contacts between individual crystallites are mainly responsible for the electrical conductivity.     

The Effect of Graphite Particle Size on Properties of Low Carbon MgO-C Composite Materials

The effects of graphite granularity on the properties of low carbon MgO-C based materials have been investigated in the work. Large crystal fused magnesia, natural flake graphite with different particle sizes and anti-oxidant were adopted as raw material for preparation of specimens. However, the results show that the physical properties oxidation resistance and thermal shock resistance of low carbon MgO-C materials with content of 4.0 wt% graphite are improved obviously through the use of special and suitable size graphite. The excellent performance achieved was considered as a result of microstructure modification of MgO-C materials. Therefore, it is suggested that both fine and micro grade natural flake graphite used for production of low carbon MgO-C bricks.     

Electrical conductivity and rheology of carbon‐filled liquid crystal polymer composites

One emerging market for electrically conductive resins is for bipolar plates for use in fuel cells. Adding carbon fillers to thermoplastic resins increases composite electrical conductivity and viscosity. Current technology often adds as much of a single type of carbon filler as possible to achieve the desired conductivity, while still allowing the carbon‐filled thermoplastic matrix material to be extruded and molded into a bipolar plate. In this study, varying amounts of two different types of carbon, one carbon black and one synthetic graphite, were added to Vectra A950RX liquid crystal polymer. The resulting single filler composites were then tested for electrical conductivity and rheological properties. The electrical conductivity followed that typically seen in polymer composites with a percolation threshold at 4 vol % for carbon black and at 15 vol % for synthetic graphite. Over the range of shear rates studied, the viscosity followed a shear‐thinning power law model with power‐law exponent (n ? 1) = ?0.5 for neat Vectra A950RX and (n ? 1) = ?0.7 for highly filled composite materials. Viscosity increased with increasing filler volume fraction for all shear rates. The viscosity–enhancement effect was more rapid for the composites containing carbon black when compared with those containing synthetic graphite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2680–2688, 2006     

制备工艺对炭/石墨密封材料性能及其结构的影响

以改性的填料（二次焦）为骨料炭,中温煤沥青为黏结剂来制备炭/石墨密封材料,考察了材料制备工艺条件对材料机械强度、开孔率以及微观结构的影响。研究表明,与传统的炭/石墨密封材料制备工艺相比,利用改性后的骨料炭所制备的炭/石墨材料具有较高的机械强度和相对均匀的孔径分布。此外,随着二次焦热处理温度的升高,最终材料的体积密度和机械强度增大,开孔率降低。当二次焦热处理温度升高到540℃时,最终所得材料的抗压和抗弯强度分别达到210.0MPa和67MPa,开孔率为19.3%。炭/石墨材料经浸渍金属Cu后,Cu颗粒在利用传统工艺制备的材料中的尺寸相对较大,且存在局部聚集或团聚,而在利用二次浆涂工艺制备的材料中则呈细网状结构且均匀分布。     

煤沥青材料的应用及其发展前景

煤沥青分为低温、中温、高温煤沥青。介绍了煤沥青的种类与性能,论述了中温煤沥青作为基础材料用作黏结剂、浸渍剂、碳纤维、涂料,道路沥青等的应用,讨论了煤沥青用作石墨电极、电炭、防腐材料、结构材料、燃料油以及在道路沥青方面的发展前景。     

Development of an additive equation for predicting the electrical conductivity of carbon‐filled composites

The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers. The resulting composites can be used in applications such as electrostatic dissipation and interference shielding. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials. The electrical conductivity of carbon‐filled polymers was studied here by the addition of three single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project were carbon black, synthetic‐graphite particles, and milled pitch‐based carbon fibers. Materials were extruded and injection‐molded into test specimens, and then the electrical conductivity was measured. Additional material characterization tests included optical microscopy for determining the filler aspect ratio and orientation. The filler and matrix surface energies were also determined. An updated model developed by Mamunya and others and a new additive model (including the constituent conductivities, filler volume fraction, percolation threshold, constituent surface energies, filler aspect ratio, and filler orientation) fit the electrical conductivity results well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2280–2299, 2003     

Physicomechanical Properties of Carbon-Containing Film Composite Materials

Addition of 5 to 20% carbon filler to film composite material (FCM) decreases its strength and mechanical modulus of elasticity. Addition of porous carbon fillers (Aktilen fibre, industrial carbon, activated carbon) decreases the physicomechanical properties of FCM even at a low content, under 5%. FCM made from a liquid composition and containing carbon fibres exhibit anisotropy of the mechanical properties due to orientation of the filler; the strength and modulus of elasticity are higher in the longitudinal than in the transverse direction. A hypothesis is advanced concerning the presence of defective regions on the polymer—filler interface and stress concentration on the ends of the fibres, which probably also causes the decrease in the mechanical properties of the FCM. Acoustic studies suggested the existence of contacts between the carbon fibres at a content in FCM of 10% and higher. __________ Translated from Khimicheskie Volokna, No. 4, pp. 52–55, July–August, 2005.     

Structural properties of carbon materials from the electrochemical reduction of fluorinated naphthalene pitch

Synthesis of carbon materials from fluorinated naphthalene pitch has been carried out by means of electrochemical reduction. Structural and morphological properties of synthesized carbons were investigated using X-ray photoelectron spectrum (XPS), Raman scattering spectrum, X-ray diffraction measurements and scanning and transmission electron microscopy (SEM and TEM). Furthermore, a change in the structure of synthesized carbons with an electron beam irradiation was examined. The synthesized carbon has a disordered structure composed of fragments of the sp² hexagonal network, and also has lots of micro-voids. A carbyne-like structure was found only a little with the reduction of fluorinated naphthalene pitch by Raman spectra. A lot of ribbon-like graphite nanocrystal was formed by irradiation of an electron beam at a high temperature to the defluorinated carbon. Bending of a long ribbon-like crystal of graphite was often observed. Formation mechanism of graphite nanocrystals was discussed.     

鳞片石墨对无粘结剂炭材料性能的影响

：采用煤沥青中加入一定量鳞片石墨制备的类中间相原料,再经过成型、烧结等工艺制备无粘结剂炭材料。实验表明：在类中间相原料制备过程中加入一定量鳞片石墨,所制得的无粘结剂炭材料的电阻率相对传统无粘结剂炭材料有所下降,其抗折强度是传统炭材料的3倍左右。当鳞片石墨质量分数为沥青的6％时,所制备的无粘结剂炭材料的体积密度为1．46g／cm^3,电阻率为46．0μ·Ω,抗折强度为29．8MPa。     

煤沥青对焦炭的浸润性及其在核石墨制备中的作用

作为炭素材料,核石墨是高温气冷堆和熔盐堆的关键材料.在炭素材料的制备过程中,粘结剂沥青对骨料焦炭颗粒的浸润性对炭素材料的生产工艺以及最终产品的强度、耐磨性都有重要影响.在研究中,人们先后采用润湿角法、液滴测试技术、渗透层厚度法以及结焦实验对煤沥青/焦炭的浸润性进行表征和检测.沥青的化学组分和结构、焦炭的粒度、表面官能团决定了沥青的表面张力、沥青的黏度以及沥青液滴在焦炭基体上的接触角,是影响沥青浸润性的主要因素.提高沥青浸润性的常用方法包括控制沥青组分,采用表面活性剂改变沥青的结构或将润湿沥青和非润湿沥青进行混合.文章的最后对我国国产核石墨研制中煤沥青浸润性的改善途径提出建议.     

Carbon materials for structural self-sensing,electromagnetic shielding and thermal interfacing

This paper reviews carbon materials for significant emerging applications that relate to structural self-sensing (a structural material sensing its own condition), electromagnetic interference shielding (blocking radio wave) and thermal interfacing (improving thermal contacts by using thermal interface materials). These applications pertain to electronics, lighting (light emitting diodes), communication, security, aircraft, spacecraft and civil infrastructure. High-performance and cost-effective materials in various forms of carbon have been developed for these applications. The forms of carbon materials include carbon fiber, carbon nanofiber, exfoliated graphite, carbon black and composite materials. Short carbon fiber cement-matrix composites and continuous carbon fiber polymer-matrix composites are particularly effective for structural self-sensing, with the attributes sensed including strain, stress, damage and temperature. Flexible graphite as a monolithic material and nickel-coated carbon nanofiber as a filler are particularly effective for electromagnetic shielding. Carbon black paste, graphite nanoplatelet paste and flexible graphite (filled with carbon black paste) are particularly effective for thermal interfacing; carbon nanotube arrays are less effective than these pastes. The associated science pertains to the relationship among processing, structure and properties in relation to the abovementioned applications. The criteria behind the design of materials for these applications and the mechanisms of the associated phenomena are also addressed.     

Wetting of filler by binder—a simple apparatus for determining wetting temperatures

A rapid, simple method of determining wetting temperatures of pitch binders on coke fillers on a comparative basis was deemed important in order to control the quality of the final electrothermic graphite. To that end, a simple apparatus was designed and constructed. The method is applicable to the determination of the wetting temperature as measured by the change in contact angle of a liquid pitch sphere on a surface of a carbonaceous material. The carbonaceous materials can be green or calcined coke, carbon black, baked carbon, or graphite. The effect of coke calcination temperature is used as a typical application.     

TiC改性炭石墨材料的微观结构与性能研究

研究了在炭石墨材料基料中均匀掺杂TiC陶瓷粉体，经高温烧结、原住合成反应、石墨化，制备了TiC改性炭石墨复合材料。研究了TiC改性炭石墨复合材料的微观结构，分析了TiC掺杂对炭石墨材料力学性能的影响，并从微观角度解释了TiC对炭石墨材料力学性能影响的机理。从研究结果可以看出，TiC掺杂可使炭陶瓷复合材料的抗折强度提高13．4％，抗压强度提高38．1％，气孔率降低16．9％；其机理在于TiC掺杂在炭陶瓷复合材料制备过程中能促进石墨化，使晶体更加完整、细化，有利于力学性能的提高。     

Effect of graphite and carbon fiber contents on the morphology and properties of thermally conductive composites based on polyamide 6

Composites of polyamide 6 (PA 6), powdered synthetic graphite and pitch‐based carbon fiber were melt processed to explore the effect of the filler contents on the anisotropic properties of the resulting composites. Optical microscopy and mechanical properties were used to determine the dispersion of graphite and carbon fiber in the PA 6 matrix. The relationship between the structure and properties showed the anisotropic filler orientation along the three principal directions. Thermal expansion in the flow direction and transverse direction decreased as filler content increased for all composites, but the decrease in the flow direction was much more significant. This anisotropic orientation also influenced the thermal conductivity of the composites resulting in an increased in‐plane thermal conductivity up to 25 times that of pure PA 6. Thermography shows good agreement with the thermal conductivity results. © 2013 Society of Chemical Industry     

Effective method for preparing uniform carbon filler for structural graphites with improved operating life

Amethod is proposed for preparing a new form of filler NUDOL(Lobastov uniformly dispersed carbon filler) for structural graphites, on whose basis materials are prepared with improved operating life at the level of the best domestic and world examples. All of the production operations are inexpensive and may be entirely accomplished under existing enterprise conditions on available equipment. With further development of the technology for preparing filler and graphite based upon it may be possible to prepare materials with properties and productive life exceeding the world level.