A comparative study of the characteristics of baked carbon mixes employing different filler materials

A study of the physical characteristics of baked carbon mixes employing calcined petroleum coke, coal-tar pitch coke, metallurgical coke and anthracite coal has been made to explore their relative suitability and area of application. It is revealed that petroleum coke and pitch coke lead to a carbon product of almost the same density and electrical resistivity. However, the crushing strength of the product employing pitch coke is 1 1/2 times that of the one employing petroleum coke. The carbon product produced from the metallurgical coke is found to be slightly inferior in respect of density and electrical resistivity and slightly superior in respect of crushing strength when compared with that made from petroleum coke. The use of anthracite coal results in a carbon product of significantly lower density and much higher electrical resistivity than that of the product using the petroleum coke. However, the strength of the anthracite coal-based carbons is found to be nearly double that of the petroleum coke-based carbons. Thus, the significance of the present study lies in the fact that the above findings help one to estimate a possible filler composition for a carbon product possessing the desirable critical characteristics.     

Physical characteristics of baked carbon mixes employing coal tar and petroleum pitches

A study of the physical characteristics of baked carbon mixes employing coal tar and petroleum pitches as the binder has been made to explore their relative suitability in the fabrication of carbon products. The study reveals that coal tar pitch is the most suitable binder and a petroleum pitch of the same softening point leads to a carbon product of much inferior characteristics. Raising the softening point of the petroleum pitch from 78 to 150° C or adding 10 parts of carbon black in the lower softening point pitch, increases the density, strength and also the electrical resistivity of the baked carbons. The addition of 10 parts of carbon black to the higher softening point petroleum pitch leads to a carbon product with further improved values of density and strength, which are comparable to those obtained with the coal tar pitch. However, the electrical resistivity also is marginally increased. It appears that a petroleum pitch of high aromaticity may fulfill the requirements expected of a good binder.     

Investigating the effect of filler types on thermodynamic parameters and their relationship with moisture sensitivity of asphalt mixes

Filler plays a significant role in mastic cohesion and adhesion between aggregate–asphalt binder in asphalt mixes. In the majority of research on investigating moisture damage based on thermodynamic concepts, little attention has been given to the role of filler. In the present study, 20 different combinations of asphalt mixes made with 4 filler types (stone powder, hydrated lime, calcium carbonate and portland cement), with two types of asphalt binder (60–70 and 85–100), and two types of aggregate (limestone and granite) were used. Then thermodynamic parameters (with and without considering the effect of filler) were calculated and the relationship between these parameters and test results of moisture sensitivity of asphalt mixes was investigated using statistical analyses. Results obtained by thermodynamic parameters show that only stone powder filler caused an increase in free energy of adhesion between base asphalt binder and aggregates, and other fillers reduced free energy of adhesion. The maximum amount of debonding energy in samples made by asphalt binder 60–70, was related to mastics containing calcium carbonate and hydrated lime fillers, and in asphalt binder 85–100, mastics containing portland cement and calcium carbonate had the maximum amount of debonding energy. However, the minimum amount of debonding energy was related to the mastic containing stone powder. In addition, the results of moisture sensitivity mechanical tests show that samples containing calcium carbonate and hydrated lime fillers had the maximum amount of tensile strength ratio. Finally, the amount of adjusted coefficient of correlation between debonding energy and modified Lottman test results increased from 0.553 in 4 base compounds (without filler) to 0.701 in 16 compounds with filler. The difference in correlation coefficients show the necessity to use the effect of filler on calculating thermodynamic parameters in investigating moisture sensitivity of various asphalt mixes.     

Pitch-matrix composites for electrical,electromagnetic and strain-sensing applications

Pitch-matrix composites for deicing, electromagnetic shielding and strain sensing have been developed by using carbon fiber (discontinuous) and carbon black as electrically conductive fillers. A composite with carbon fiber (5 vol%) as the sole filler is effective for strain sensing, which functions by the electrical resistivity increasing reversibly with tensile strain. A composite with carbon fiber (3.4 vol%) and carbon black (1.5 vol%) is less effective for strain sensing and is lower in tensile strength, modulus and ductility, but it is lower in the electrical resistivity. A composite with carbon black (7 vol%) as the sole filler is very high in resistivity, but exhibits high storage modulus. Either carbon fiber or carbon black as filler increases the storage modulus, decreases the resistivity, renders the ability to provide EMI shielding and increases the softening temperature.     

Effect of heat treatment on properties of steam cured fly ash-lime compacts

Four different varieties of class F fly ashes, collected from different sources from the state of West Bengal (India) were mixed with lime in 9 : 1 wt ratio, followed by compaction of the mixes. The compacts were subjected to steam curing to develop an optimum strength by the reaction between fly ash and lime. The steam cured compacts were heated at different elevated temperatures and free lime content, compressive strength, bulk density and water absorption tendency of these compacts were measured and FTIR spectral changes were studied as a function of the heating temperatures. Kinetics of thermal dehydration of the compacts was also studied from thermogravimetric measurements under non-isothermal condition to ascertain the order of dehydration process and the associated activation energy.     

低温快速固化环氧导电胶的制备与性能

采用E-51型环氧树脂为导电胶基体树脂, 低分子量聚酰胺树脂(PA)为固化剂, 填加经硅烷偶联剂(KH550)改性后的纳米级和微米级铜粉及助剂制备导电胶。首次采用了液态固化剂(低分子量的聚酰胺酯), 以解决导电胶制备过程中填料用量受限的难题。通过正交试验方法探讨了导电胶中导电填料的含量、导电填料配比、硅烷偶联剂用量和还原剂添加量对导电胶粘接性能和导电性能的影响, 对导电胶的制备工艺进行了优化, 获得了制备导电胶的最佳方案。测试结果表明该导电胶能够在60 ℃下4 h内快速固化。在填料质量分数为65%时, 导电胶具有最低的体积电阻率3.6×10-4 Ω·cm; 导电胶的抗剪切强度达到17.6 MPa。在温度为85 ℃、湿度(RH)为85%的环境下经过1000 h老化测试后导电胶电阻率的变化和剪切强度的变化均不超过10%。      

填充碳纳米管各向同性导电胶的性能

制备了以碳纳米管(CNTs) 和镀银碳纳米管(SCCNTs) 为导电填料的各向同性导电胶, 研究了它们的电学性能、力学性能及抗老化性能, 并与传统的以微米量级的银粒子作为导电填料的导电胶的性能进行比较。研究发现: CNTs 作为导电填料时, 在填料体积分数为31 %时出现体积电阻率的最低值2. 4 ×10-3Ω·cm; 在填料体积分数为23 %时导电胶表现出最好的抗剪切性能。在填料体积分数同为28 %时, 填充SCCNTs 导电胶具有最低的体积电阻率2. 2 ×10-4Ω·cm; 填充CNTs 和SCCNTs 显示出比填充微米量级银粒子导电胶高的抗剪切强度(19. 6 MPa) 。在85 ℃、RH 85 %环境下经过1000h 老化测试结果表明: 填充SCCNTs 或CNTs 导电胶体积电阻率的变化和剪切强度的变化均不超过10 %; 而填充微米量级银粒子导电胶在老化后体积电阻率的变化和抗剪切强度的变化分别达到350 %和120 %。      

原料配比对石墨材料热传导性能的影响

以煅烧石油焦和煤沥青为基本原料，采用热压工艺制备了一系列石墨材料，考察了煅烧石油焦填料的粒度分布以及粘结剂用量对石墨材料的传导性能的影响，并阐明了粘结剂与填料粒子在热混捏与热压过程中相互作用原理。结果表明：石墨材料的传导性能不仅依赖于原料种类，粒度，而且与其质量配比有关，有最佳原料配比所制备的块状石墨具有高密度，低孔率，低电阻以及高导热等特点；填料煅烧石油焦颗粒以及粘结剂用量的过多或过少，都不利于石墨材料的传导性能，本文填料中最佳煅烧石油焦颗粒用量为25%，原料中最佳粘结剂含量为25%。     

Properties of cementitious systems containing silica fume or nonreactive microfillers

The object of this work was to explore the effects of silica fume on the microstructure of hardened paste and of the transition zone between paste and aggregates in concrete. The significance of aggregates as reinforcing fillers and their impact on some properties of the transition zone and bulk paste were resolved. The experimental procedure was based on simultaneous studies of model concretes and paste matrices extracted from fresh model concrete mixes. In addition, continuously graded aggregate concretes were prepared. Three sizes of a nonreactive microfiller (carbon black) and one reactive microfiller (silica fume) were applied. On the basis of microstructural studies and compressive strength tests, it was concluded that the primary effect of silica fume was generated by its physical (microfiller) properties, since the strengthening provided by reactive silica fume was similar to that obtained with nonreactive carbon black of similar size and shape. This effect was more significant from the point of view of the concrete strength enhancement than the chemical (pozzolanic) activity of the silica fume. In concretes containing either silica fume or carbon black, aggregates of high quality could serve as reinforcing filler. This could take place when sufficient densification of the transition zone occurred in the presence of silica fume or carbon black. Significant refinement of pore structure was observed in both types of paste matrices (containing silica fume or carbon black). However, this led to a relatively small influence on the paste strength. Concretes containing reactive silica fume or an inert carbon black microfiller behaved as a composite material, unlike conventional concrete.     

Hybrid filler composition optimization for tensile strength of jute fibre-reinforced polymer composite

In present research work, pultrusion process is used to develop jute fibre-reinforced polyester (GFRP) composite and experiments have been performed on an indigenously developed pultrusion experimental setup. The developed composite consists of natural jute fibre as reinforcement and unsaturated polyester resin as matrix with hybrid filler containing bagasse fibre, carbon black and calcium carbonate (CaCO₃). The effect of weight content of bagasse fibre, carbon black and calcium carbonate on tensile strength of pultruded GFRP composite is evaluated and the optimum hybrid filler composition for maximizing the tensile strength is determined. Different compositions of hybrid filler are prepared by mixing three fillers using Taguchi L₉ orthogonal array. Fifteen percent of hybrid filler of different composition by weight was mixed in the unsaturated polyester resin matrix. Taguchi L ₉ orthogonal array (OA) has been used to plan the experiments and ANOVA is used for analysing tensile strength. A regression model has also been proposed to evaluate the tensile strength of the composite within 7% error by varying the above fillers weight. A confirmation experiment was performed which gives 73.14 MPa tensile strength of pultruded jute fibre polymer composite at the optimum composition of hybrid filler.     

Microstructure and strength of brazed joints of Ti3Al-base alloy with different filler metals

The interfacial microstructure and properties of brazed joints of a Ti₃Al-based alloy were investigated in this paper to meet the requirements of the use of Ti₃Al-based alloy in the aeronautic and space industries. The effects of different brazing fillers on the interfacial microstructure and shear strength were studied. The relationship between brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. The brazed joints were qualitatively and quantitatively analyzed by means of EPMA, SEM and XRD. The results showed that using a AgCuZn brazing filler, TiCu, Ti(Cu,Al)₂ and Ag[s,s] were formed, the shear strength of the joint was decreased because of the formation of TiCu and Ti(Cu,Al)₂; using a CuP brazing filler, Cu₃P, TiCu and Cu[s,s] were formed at the interface of the joint, the former two intermetallic compounds decreased the shear strength. The analysis also indicated that using the TiZrNiCu brazing filler, the optimum parameters were temperature T=1323 K, joining time t=5 min, and the maximum shear strength was 259.6 MPa. For the AgCuZn brazing filler, the optimum parameters were joining temperature T=1073 K, joining time t=5 min, and the maximum shear strength was 165.4 MPa. To the CuP brazing filler, the optimum parameters were joining temperature T=1223 K, joining time t=5 min, and the maximum shear strength is 98.6 MPa. Consulting the results of P. He, J.C. Feng and H. Zhou [Microstructure and strength of brazed joints of Ti₃Al-base alloy with NiCrSiB, Mater. Charact., 52(8) (2004) 309–318], relative to the other brazing fillers, TiZrNiCu is the optimum brazing filler for brazing Ti₃Al-based alloy.     

Control of the temperature coefficient of the DC resistivity in polymer-based composites

In this study, the roles of polymer matrices and filler additives in controlling the positive temperature coefficient (PTC)/negative temperature coefficient (NTC) behavior of DC resistivity at high temperature for semicrystalline ethylene vinyl acetate copolymer, amorphous acrylonitrile butadiene copolymer, and their blend composites filled with different carbon fillers like Conductex carbon black, Printex carbon black, and short carbon fiber have been investigated. It is seen that the PTC/NTC behavior of resistivity depends on the characteristics of both polymer matrices and filler additives. The anomaly in the results are due to polymer crystallinity, shape and size of fillers, and their thermal expansion coefficient, that play major role in controlling the PTC/NTC of resistivity at high temperature for the composites. Finally, reproducibility of composite resistivity has been evaluated with their some proposed practical applications. These composites can be used as both PTC and NTC thermistors.     

Increasing the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation

The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer-matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (?1.5 vol.%) at the interlaminar interface. The 7-μm-diameter 7-W/m K-thermal-conductivity continuous fiber volume fraction is increased by the curing pressure increase, but is essentially unaffected by filler incorporation. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber-fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber-fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. The curing pressure increase does not affect the effectiveness of 1-mm-long 10-μm-diameter 900-1000-W/m K-thermal-conductivity K-1100 carbon fiber or single-walled carbon nanotube (SWCNT) as fillers for enhancing the conductivity, but hinders the effectiveness of carbon black (CB, low-cost), which is less effective than K-1100 or SWCNT at the higher curing pressure, but is almost as effective as K-1100 and SWCNT at the lower curing pressure. The effectiveness for enhancing the flexural modulus/strength/ductility decreases in the order: SWCNT, CB, K-1100.     

Binderless Carbon/Graphite Materials

High performance binderless carbon bodies can be mamufactured from the mesophase raw material derived from petroleum pitch, which is ground into fine powders less than 10μm, and directly moulded, then sintered at 1000℃ without any kind of binder. The sintered bodies have a bulk density of 1.69 g/cm3, bending strength of 91.2 MPa. Shore hardness of 100. Porosity of only 7.2%. and electrical resistivity of 60x10-6 m. The bodies graphitized at 2800℃ have a bulk density of 1.88 g/cm3, bending Strength of 82 MPa. Shore hardness of 85, porosityof 5.4%, and electrical resistivity Of 12x10-6 nm. The scanning electron micrographs of thesection show that the bodies possess an extremely dense and homogeneous structure. lnfra-redspectrum analysis shows that carbonyls introduced when ground or activated are one of the keyfactors determining the selfbinding and self sintering properties of the mesophase fine powders,and the Structure and strength of the sintered bodies.     

Electrical properties of hybrid carbon black/carbon fiber polypropylene composites

The electrical conductivity and morphology of injection molded polypropylene based composites containing two conductive fillers, carbon black (CB) and carbon fibers (CF) were studied. Injection moldings containing both, CB and CF, where the content of each filler was above its own percolation threshold, resulted in similar or lower values of overall composite volume resistivity compared with the resistivity of systems filled only with CB at the corresponding content. However, the resistivity of two-filler systems is always higher than the resistivity of systems filled only with CF at the corresponding content. The morphology and fiber length analysis of the injection molded composites are quite intriguing. Fiber orientation in the injection molded two-filler systems was found to be almost perpendicular to the melt flow direction, with no significant skin-core fiber orientation patterns, contrary to the typically observed fiber orientation in injection molded fiber filled composites. Moreover, the CF breakage in the presence of the CB was found more intense than when just CF is used, resulting in shorter fibers with narrower length distributions. This unexpected fiber behavior is responsible for the unexpected electrical behavior. However, the coexistence of CB and CF electrically conductive networks, supporting each other, was confirmed, in spite of the mechanical disturbances caused by the presence of fibrilar and particulate fillers.     

Influence of the aggregate quality on the physical properties of natural feebly-hydraulic lime mortars

This paper examines the influence of the shape, average size and calcite content of the aggregate on strength, porosity, water absorption, density and capillary suction of natural feebly-hydraulic lime (NHL 2) mortars. Four types of aggregate were analysed in order to determine calcite content, particle shape and average particle size. Four different mortar mixes were then designed and produced using each of the aggregate types and NHL 2 as a binder. The mixing and curing as well as the aggregate:binder proportions were kept constant in order to attribute variation of mortar properties to the quality of the aggregate. The results suggest that an increase in the aggregate’s calcite content lowers the flexural and compressive strength of the mortar. This study also determined that sharp aggregate as well as aggregate with a small average particle size tends to increase the mechanical strength and bulk density of a mortar simultaneously reducing porosity, water absorption and capillary suction. Furthermore, this paper concludes that aggregates containing particles of a wide size range will also increase the mechanical strength and bulk density of the hardened mortar diminishing porosity, water absorption and capillary suction.      

Study on the optimization design of mixing moisture content in foamed asphalt mix

This research discussed the rational mixing moisture content (MMC) in foamed asphalt (FA) mix design. Sieve analysis was firstly used to study the bitumen dispersion and bitumen-aggregate coating and bonding action in FA mixes with three levels of MMC. Then, through variance analysis, the impacts of MMC, bitumen content and their interaction effect on the mechanical properties of FA mixes were studied. Indirect tensile strength test and dry density determination were carried out on FA mixes consisting of different gradings and material types to explore the rational MMC. On base of that, monotonic triaxial test was performed on two types FA mixes with various filler contents to further investigate the rational MMC for FA mix. The research results indicated that improper MMC led to bitumen clots and affected cohesion of FA mix. MMC and bitumen content had important impacts on mechanical properties of FA mix, while their interaction effect could be ignored in mix design. Optimal MMC increased to a certain extent with the increase of fine aggregates content, especially filler content in the grading. 70?C80% of the optimum moisture content (OMC) was recommended as rational range of MMC for FA mix with 5?C15% filler content and 75?C85% of OMC for mix with 15?C20% filler content, which offered a reference for easy and simplified MMC design for FA mix.     

Effects of chemical treatments of hybrid fillers on the physical and thermal properties of wood plastic composites

Hybrid filler reinforced composites are considered as a high performance materials, but limited numbers of researches on hybridizations of wood fibers and mineral fillers were reported. Generally, high amount of filler content in composites can lead to the reduction of interfacial adhesion between matrix polymer and fillers, and it limits their applications. In this study, we measured the changes of tensile strength, water absorption, and thermal properties of composites after chemical treatments to wood fibers and mineral fillers. Coupling agent had its own optimum amount for wood fibers and talc to obtain the highest tensile strength. Talc addition showed little effect of the tensile strength with alkali treated wood fibers. Talc addition and silane treatment showed opposite effects on water absorption. Melting enthalpy was decreased by addition of the fillers because of the reduced amount of the crystallizable resin and because of the interference of the fillers for crystallization process.     

Assessing the effect of biomass ashes with different finenesses on the compressive strength of blended cement paste

This study assesses the effect of biomass ashes with different finenesses on the compressive strength of blended cement paste. rice husk ash (RHA), palm oil fuel ash (POFA) and river sand (RS) were ground to obtain two finenesses: one was the same size as the cement, and the other was smaller than the cement. Type I Portland cement was replaced by RHA, POFA and RS at 0%, 10%, 20%, 30% and 40% by weight of binder. A water to binder ratio (W/B) of 0.35 was used for all blended cement paste mixes. The percentages of amorphous materials and the compressive strength of the pastes due to the hydration reaction, filler effect and pozzolanic reaction were investigated. The results showed that ground rice husk ash and ground palm oil fuel ash were composed of amorphous silica material. The compressive strength of the pastes due to the hydration reaction decreased with decreasing cement content. The compressive strength of the pastes due to the filler effect increased with increasing cement replacement. The compressive strengths of the pastes due to the pozzolanic reaction were nonlinear and were fit with nonlinear isotherms that increased with increasing fineness of RHA and POFA, cement replacement rate and age of the paste. In addition, the model that was proposed to predict the percentage compressive strength of the blended cement pastes on the basis of the age of the paste and the percentage replacement with biomass ash was in good agreement with the experimental results. The optimum replacement level of rice husk ash and palm oil fuel ash in pastes was 30% by weight of binder; this replacement percentage resulted in good compressive strengths.     

Study of the influence of Chitosan on selected properties of elastomeric blends

The current trend of greening production is increasingly bringing to the fore alternative types of fillers, such as biofillers, which are obtained from renewable sources or waste [1, 2]. Unfortunately, biofillers cannot be used as majority fillers due to their incompatibility with elastomer matrices and high biodegradability susceptibility [3, 4]. Therefore, the way to their efficient industrial use leads through supplementary fillers to the commonly used inorganic fillers and the partial replacement of these fillers in the blend. The influence of Chitosan as the majority filler has been investigated and its combination with carbon black filler on the elastomeric matrix of natural rubber was investigated in the presented work. The results were compared with natural rubber blends filled exclusively with carbon black. Natural rubber blends with different content of Chitosan and carbon black and their various combinations were subjected to the determination of vulcanization parameters, mechanical properties before and after thermo-oxidative aging, and scanning electron microscopy. Although the scanning electron microscopy analysis confirmed the expected negative impact of Chitosan as the majority filler on the tensile properties of the vulcanizate, its significant impact on the main vulcanization parameters such as scorch time and optimal vulcanization time was also demonstrated. In the case of blends with a combination of carbon black and Chitosan, it has been shown that Chitosan, in addition to the filler function, also acts as an antioxidant agent through its functional groups, limiting the process of degradation of mechanical properties of natural rubber blends due to their thermo-oxidative aging. It can be concluded that precisely because of its antioxidant and anti-degradation effects, Chitosan can be, in addition to carbon black filler, an excellent additional filler for elastomeric blends.