Carbon Black Surface Area Research Articles

Tires for Mars Rovers: Reinforcing BR and BR/Vinyl-Methyl Silicone Rubber Compounds with Carbon Black, Nano-CaCO3, or Silica for Good Low-Temperature Dynamic-Mechanical Performance

ABSTRACT Dynamic increment in Mars exploration missions necessitates the development of new materials that can satisfy the ever more stringent requirements. Currently, most of the materials used for manufacturing Mars rovers and landers are based on various metal alloys that provide high reliability in the Martian environment. However, the future planned missions, including the first human crew landing on Mars, require the development of new rubber materials that could be used for sealing Mars suits, for tires/tracks, and for damping systems for heavy Mars rovers. This research aims to investigate the properties of butadiene rubber (BR) and butadiene/vinyl-methyl silicone rubber blends (BR/VMQ) filled with various reinforcing fillers: carbon blacks (CBs), silicas, and nanometric calcium carbonate (nano-CaCO3), in order to evaluate their performance from the point of view of Mars' environmental applications. The study revealed that the designed composites exhibit very good low-temperature elasticity, and the addition of 30 phr of high surface area CB (N220) or silica (Ultrasil 9100) results in good mechanical properties of the compounds. The mechanical properties of the BR/VMQ blends depend on the type of reinforcing filler. The addition of the CBs resulted in better mechanical properties, while the incorporation of silicas worsens the mechanical properties of BR/VMQ blends in comparison to their BR counterparts. The high-cis BR grade exhibits a strong tendency to crystallize in the operating temperature range on Mars (crystallization ∼−60 °C, melting ∼−20 °C), and the addition of the fillers nucleates the crystallization, resulting in a higher amount of the crystalline phase. This might be a serious problem for any sealing application of the rubber compounds. For this reason, a non-crystallizable BR grade is recommended for further studies.

Effect of Pt Loading Percentage on Carbon Blacks with Large Interior Nanopore Volume on the Performance and Durability of Polymer Electrolyte Fuel Cells

Achieving high performance and durability at low Pt loads is an important challenge for polymer electrolyte fuel cells (PEFCs). We investigated the effect of catalyst Pt loading percentage (wt % Pt) on the performance and durability of an ultrahigh surface area carbon black (CB) with a large nanopore volume using morphological observations, nitrogen adsorption, and electrochemical performance measurements. The ratio of the surface areas of Pt on the interior and exterior surfaces of the CB affects the penetration of the ionomer into the nanosized pores. When the exterior Pt surface area is larger than that of the interior, the oxygen diffusion resistance in the ionomer increases and the performance deteriorates due to the thick covering of the ionomer on the exterior Pt. Based on durability testing that combines startup, shutdown, and galvanostatic load cycling, the main deterioration factors are dependent upon the Pt interparticle distance and the thickness of the catalyst layer, which vary with the wt % Pt. The advanced characterization and optimization of the various wt % Pt on an ultrahigh surface area CB, combined with the extensive performance and durability testing, have provided an unprecedented understanding of the reaction sites, mass transport characteristics, and stability, which are crucial for their practical application in PEFCs.

(Invited) Highly Durable and Active Electrocatalysts Using SnO2 Supports for Polymer Electrolyte Fuel Cells

Toward the widespread use of polymer electrolyte fuel cells (PEFCs) in electric vehicles, highly durable and active catalysts are required. Pt catalysts loaded on high surface area carbon blacks are promising candidate catalysts with high oxygen reduction reaction (ORR) activity [1]. In the future, the improvement of the catalyst durability is also desired for PEFCs for heavy use applications. Alternative candidate catalysts with high activity and high durability, during both startup/shutdown and load cycling, are Pt catalysts supported on non-carbon ceramic supports [2,3]. Our group confirmed that Pt catalysts supported on SnO2 (Pt/M-SnO2, M = Nb, Ta) without carbon additive were superior in ORR activity and durability (startup/shutdown, load cycling) to those of commercial Pt catalysts, e.g., supported on either graphitized carbon black (Pt/GCB, TEC10EA30E, TKK) or carbon black (Pt/CB, TEC10E30E, TKK), by evaluation of membrane-electrode assemblies [4-8]. The non-carbon support of SnO2 nanoparticles has a unique carbon-like microstructure consisting of a fused-aggregate network structure, which enhances the electronically conducting pathways via the aggregated microstructure and gas diffusion pathways via the open pores in the microstructure. In addition, the interface control between Pt and SnO2 support also affects the decrease of both the overpotential for the ORR and the resistance of the cathode catalyst layer (CL). We have also proposed ways to design the three-phase boundary within the CL to diminish the gas diffusion resistance (Fig. 2). The cell performance using the Pt/SnO2 cathode CL at operating temperatures from 80oC to 120oC is quite promising for the development of high power density with simultaneous high durability. Acknowledgments This work was partially supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cell” (SPer-FC) project and the “Advanced Research Program for Energy and Environmental Technologies” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and JSPS KAKENHI Grant Number (B24350093, B17H03410) from the Ministry of Education, Culture, Sports, Science and Technology. References N. Ramaswamy, W. Gu, J.M. Ziegelbauer, S. Kumaraguru, J. Electrochem. Soc., 167, 064515 (2020).A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Electrochem. Solid-State Lett., 12, B119 (2009).E. Fabbri, A. Rabis, R. Kötz, T.J. Schmidt, Phys. Chem. Chem. Phys., 16, 13672 (2014).K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Electrochim. Acta, 56, 2881 (2011).Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, M. Watanabe, RSC Adv., 6, 321800 (2014).Y. Chino, K. Taniguchi, Y. Senoo, K. Kakinuma, M. Watanabe, M. Uchida, J. Electrochem. Soc., 162, F736 (2015).K. Kakinuma, R. Kobayashi, A. Iiyama, M. Uchida, J. Electrochem. Soc., 165, J3083 (2018).K. Kakinuma, K. Suda, R. Kobayashi, T. Tano, C. Arata, I. Amemiya, S. Watanabe, M. Matsumoto, H. Imai,Iiyama, M. Uchida, ACS Appl. Mater. Interfaces 11, 34957 (2019). Figure 1

Chemical resistance of NR/SBR rubber blends for surfaces corrosion protection of metallic tanks in petrochemical industries

Abstract In this work, a series of Natural Rubber (NR)/Styrene Butadiene Rubber (SBR) blends were formulated to protect metallic petrochemical storage tanks from corrosive media. Therefore, these blends tested against a 10% HCl solution for 72 hr at room temperature. Blends series were prepared with different ratios of NR/SBR; 25/75, 30/70, 35/65, 40/60, 45/55, 50/50, and 55/45. Three types of carbon black (N-330, N-660, and N-762) were added individually to the 45/55 blend. Hardness, tensile strength, modulus, and elongation properties were tested before and after immersion in the 10% HCl attack media. All these mechanical properties decreased after immersion action accept hardness property. Up to 45 phr NR content, the hardness increased linearly independent on immersion action, but HCl immersion gives higher hardness values. Tensile strength increased up to 40 phr NR content with and without immersion and the immersion action decreased tensile values. The highest elongation value obtained with 35/65 blend with and without immersion. The 45 phr NR content gives the higher modulus, while the lowest value obtained with the 30 phhr content. For 45/55 blend, the hardness increased as the carbon black particle size decreased and immersion action gives higher hardness values. The tensile strength decreased linearly with the carbon black surface area, while with the medium surface area, the highest modulus and lowest elongation obtained.

Modeling Oxygen Transport in High Surface Area Carbon Supports for Polymer-Electrolyte Fuel Cells

An analytical model for resistance to oxygen transport in air electrodes containing carbon black supports with high surface area was developed by combining a Thiele modulus—effectiveness factor approach at the agglomerate scale (∼150 nm) with nanoscale diffusional resistance in carbon micropores/pits (∼5 nm). This paper extends an earlier model for transport resistance to platinum nanoparticles on low surface area carbon. Differences in transport resistances between catalyst layers with high and low surface area carbon blacks predicted by the model with reasonable geometric dimensions and physical properties are consistent with experimental observations.

Synergistic effect by high specific surface area carbon black as secondary filler in silica reinforced natural rubber tire tread compounds

The partial replacement of silica by high specific surface area and high structure Carbon Black (CB) N134 as secondary filler, keeping the same total filler content at 55 phr, shows a clear synergistic effect on overall performance. At low content of CB, i.e. in the range of 0–36 wt% of CB relative to total filler amount, the Payne effect and tan delta at both 0 °C and 60 °C change marginally, but thereafter gradually increase. Cure times are shortened in the presence of CB, facilitating an increase of productivity. Bound rubber content and mechanical properties show an optimum at 18 wt% of CB relative to total filler amount or at a ratio of silica/CB 45/10 phr. With regard to tire performance as indicated by the laboratory test results, the abrasion resistance, wet grip and ice traction can therefore be enhanced while maintaining the tire rolling resistance at the optimum level for this silica/CB ratio.

Effect of Different Types of Rubbers and Carbon Black Grades on Curing Characteristics and Dynamic Properties for Anti-vibration Application

Nowadays, the automotive industry is facing a major challenge to meet the changing demand on performance, material specifications and durability requirements. An anti-vibration part is a critical component in automotive, used to eliminate the vibration. In order to produce a good anti-vibration component, the rubber compound needs to be formulated with good damping properties. This research work focused on the effect of (unfilled) rubber types; natural rubber (SMR 60CV, SMR L, RSS) and synthetic rubber (SBR, NBR, CR, EPDM) and the effect of carbon black grades (N220, N330, N550, N774, N990). The curing characteristics and dynamic properties (dynamic stiffness, Kd) at 15, 45 and 100 Hz were analyzed. The curing characteristic results showed there is a relationship between both factors. The longer cure time for types of rubber indicates longer time is needed to break higher bond energy of the rubber chain. Meanwhile, for carbon black grades, the cure rate is gradually increased with lower carbon black surface area due to the diffusion limitation and lower chain mobility. The dynamic properties results were based on the Payne effect theory which influenced by the rubber bond structure that gave higher value of dynamic stiffness due to rubber-rubber interaction. For carbon black grades, the higher surface area of carbon black gave higher dynamic stiffness due to increased rubber-filler and filler-filler interactions.

Enhancing the Performance of Motive Power Lead-Acid Batteries by High Surface Area Carbon Black Additives

The effects of carbon black specific surface area and morphology were investigated by characterizing four different carbon black additives and then evaluating the effect of adding them to the negative electrode of valve-regulated lead–acid batteries for electric bikes. Low-temperature performance, larger current discharge performance, charge acceptance, cycle life and water loss of the batteries with carbon black were studied. The results show that the addition of high-performance carbon black to the negative plate of lead–acid batteries has an important effect on the cycle performance at 100% depth-of-discharge conditions and the cycle life is 86.9% longer than that of the control batteries. The excellent performance of the batteries can be attributed to the high surface area carbon black effectively inhibiting the sulfation of the negative plate surface and improving the charge acceptance of the batteries.

The Effect of Electrochemical and Gas Phase Activation of High Surface Area Carbon Black Ketjen Black EC 600 DJ on Its Surface Composition, Electrochemical Capacitance, and Stability

The effect of electrochemical and gas-phase activation of high-surface-area carbon black Ketjen Black EC 600 DJ on its stability and electrochemical capacitance is studied. The electrochemical activation is carried out according to the “start–stop” protocol (1–1.5 V, 0.5 V/s). The stability of samples is assessed based on variation of their effective resistance (based on the results of cyclic voltammetry (CVA)) and electrochemical capacitance (based on CVA and galvanostatic data) with the cycle number. The changes in the texture and surface properties of activated samples are studied by the methods of nitrogen low-temperature adsorption and X-ray photoelectron spectroscopy. The gas-phase activation of high-surface-area carbon black Ketjen Black EС 600 DJ is shown to impair its stability, while the electrochemical oxidation of carbonblack samples leads to a considerable (two-fold) increase in their electrochemical capacitance.

Analysis of the Corrosion Kinetic of Pt/C Catalysts Prepared on Different Carbon Supports Under the “Start-Stop” Cycling

A series of 50 wt% Pt/C catalysts based on carbon blacks with different specific surface areas and morphologies was synthesized and investigated using “start-stop” protocol (triangular scan in the 1.0–1.5 V vs. reversible hydrogen electrode (RHE) potential range with a scan rate of 500 mV s−1). The commercial 40 wt% Pt/Vulcan XC-72 and 50 wt% Pt/TEC were used for comparison. The oxygen reduction reaction (ORR) activities and electrochemically active surface area (ECSA) of Pt were obtained at 25 °C in 0.1 M HClO4 electrolyte after every 4000 cycles. All synthesized Pt/C catalysts were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), low-temperature nitrogen sorption, CO pulse chemisorption methods, and cycling voltammetry including a rotating disc electrode (RDE) method for analysis of the ORR kinetics. Dependences of the ORR activities, ECSA, and values of Tafel slopes on the number of oxidative cycles were obtained and analyzed in detail. It was shown that the initial values of Tafel slopes of the Pt/C catalysts decrease with increase of the surface area of carbon blacks. The increase in the values of Tafel slopes in the high-current density region with cycling was associated with the degradation of carbon support. The reciprocal ratios of the ECSA to initial values were found to grow linearly on the number of cycles. The ORR surface activity was significantly decreased in the first 8000–10,000 oxidation cycles as the result of changes of the active component and carbon support degradation. The following slight increase in the ORR surface activities with cycling was related to the increase in the Pt particle sizes in the Pt/C catalysts. Modification of Ketjen black EC 600 DJ through pyrocarbon deposition (KB600-C sample) led to appreciable increase of the stability of the Pt/KB600-C sample.

Hybrid of Fe@Fe3O4 core-shell nanoparticle and iron-nitrogen-doped carbon material as an efficient electrocatalyst for oxygen reduction reaction

To realize a large-scale application of fuel cells, it is highly desirable to develop noble metal-free electrocatalysts for oxygen reduction reaction (ORR). Herein, a highly active electrocatalyst is synthesized by impregnating in situ generated iron(III)-1,10-phenanthroline complex on commercially high specific surface area carbon blacks and subsequent pyrolysis at high temperature. High ORR limiting current density (5.79mAcm−2) and positive half-wave potential (0.859V versus RHE) over this electrocatalyst with a mass loading of 0.2mgcm−2 can be achieved in 0.1M KOH solution, which are very comparable with the benchmark Pt/C electrocatalyst. Detailed investigations have revealed the existence of nitrogen doped carbon (N-C), nitrogen coordinated to Fe (Fe-N), and Fe@Fe3O4 core-shell nanoparticles in this composite electrocatalyst. The high activity of this electrocatalyst is attributed to the synergistic effect among them.

Surface area as a dose metric for carbon black nanoparticles: A study of oxidative stress, DNA single-strand breakage and inflammation in rats

Combustion-derived nanoparticles are characterised by a high surface area (SA) per mass. SA is proposed to regulate the bioreactivity of nanoparticles; however, the dose metric for carbon black remains controversial. To determine the relationships between bioreactivity and SA, male spontaneously hypertensive rats were exposed to carbon black (CB) nanoparticles (15, 51 and 95 nm) via intratracheal instillation for 24 h. Pulmonary exposure to CB resulted in a significant increase in systemic 8-hydroxy-2′-deoxyguanosine (8-OHdG), DNA single-strand breakages in peripheral blood cells and pulmonary cell infiltration in rats. The oxidative potential and particularly the corresponding SA of CB were correlated with the level of 8-OHdG, DNA single-strand breakages and pulmonary cell infiltration in rats. We conclude that SA is an important dose metric for CB that can regulate oxidative stress and DNA damage in rats. Furthermore, this observation was more significant for smaller sized CB.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: II. Influence of Ink Formulation, Catalyst Layer Uniformity and Thickness

Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mgPt and SA 864 ± 56 μA/cm2Pt while Pt/V had MA 706 ± 42 mA/mgPt and SA 1120 ± 70 μA/cm2Pt when measured in 0.1 M HClO4, 20 mV/s, 100 kPa O2 and 23 ± 2°C. An enhancement factor of 2.8 in the measured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (∼4.5 μg/cm2Pt) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m2/gPt) and Pt/V (65 ± 5 m2/gPt) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.

Porosity Blocking in Highly Porous Carbon Black by PVdF Binder and Its Implications for the Li–S System

In this work, the influence of cathode binders on the porosity of composite electrodes for lithium–sulfur (Li–S) batteries employing high surface area carbon blacks has been closely scrutinized. This has been accomplished by comparison of PVdF with the related copolymer, PVdF-HFP. Analysis of carbon black porosity after addition of binder in NMP solution reveals that PVdF(-HFP) fills pores of almost any size in carbon black, which can effect a severe reduction in pore volume and surface area accessible to the electrolyte in a Li–S cell. Noting the different swelling behavior of both binders, the implications of pore filling by the binder on the electrochemistry of Li–S cells can be determined. Because of the low swellability of PVdF in dimethoxyethane:dioxolane (DME:DOL)-based electrolytes, access of the electrolyte to the carbon surface area and pore volume is restricted, with potentially severe detrimental effects on the available capacity of the cell. Furthermore, this effect is still clearly significant for common binder loadings and with preinfiltration of sulfur; this study is therefore a clear demonstration that PVdF is an unsuitable choice of binder for the lithium–sulfur system and that alternatives must be considered.

Influence of Reactions of Carbon Black and Fuel Diffusion Process on Power Generation Characteristics of Rechargeable Solid Carbon Fuel Cells(RSCFCs)

Rechargeable Solid Carbon Fuel Cells (RSCFCs) that use directly supplied carbon black (CB) as fuel were developed. The influence of the CO supply rate depended on the CO generation rate and the CO diffusion rate on the power generation was investigated. High power density was achieved by using a larger specific surface area CB fuel due to the increase in CO generation rate. Two types of cell setting were evaluated, horizontal and vertical setting. With horizontal cell setting, densely supplied CB enhanced the power density because the increase in the CO generation rate was greater than the decrease in CO diffusion rate due to the increase of CB surface area per unit column volume. However, CB supply density should decrease during the power generation due to the CB consumption by Boudouard corrosion reaction. In contrast, with the vertical cell setting, CB supply density must be almost constant because CB maintains contact with the anode surface by its own weight. Moreover, the performance of RSCFC was improved by using anode with high porosity. With 27 % porous anode, the maximum power density (PMax ) was 24.1 mW/cm2 at 50 mA/cm2, and with 33 % porous anode, the PMax was 34.6 mW/cm2 at 70 mA/cm2. The total TPB (Triple Phase Boundary) length in anode might be decreased with increasing porosity of anode, but the power density of RSCFC with CB fuel was increased.

Durability of Low-Temperature Fuel Cell Electrocatalysts

Durability of Low-Temperature Fuel Cell Electrocatalysts

Single-Atoms and Sub-Nanometer Clusters of Pt on Graphene Support Prepared By Atomic Layer Deposition

To maximize Pt utilization in polymer electrolyte membrane fuel cells (PEMFCs), platinum nanoparticles (Pt NPs) supported on high surface area carbon blacks are usually used as catalysts for both oxygen reduction and hydrogen oxidation.1 For the wide-spread commercialization of PEMFCs, key challenges to be addressed are the high electrochemical activity and high stability for low-Pt-loading catalysts. It is expected that downsizing catalyst nanoparticles to clusters or even single atoms could significantly increase their catalytic activity and is therefore highly desirable to maximize the efficiency. However, the particle-size dependent catalytic activity of Pt, determined by the interplay of surface geometric and electronic factors, is not quite straightforward in the range of a few nanometers.2,3 The interaction of Pt with support, as well as the interaction of Pt precursor with support during the supported catalyst formation, are considered to play key roles on the formation of Pt NPs, as well as their activity and stability.Recently, due to their unique electric and micro-structural characteristics, nanostructured carbon materials with graphene structures such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been studied extensively as alternative supports for electrocatalysts, showing much enhanced fuel cell performance.4 Graphene, a unique structure of a two-dimensional (2D) sheet composed of sp2-bonded carbon atoms with one-atomic layer thick, has inspired a flurry of interests for both fundamental science and applied research due to its extraordinary properties. One hopes to employ such 2-D sheets as conductive supports to both anchor electrocatalysts and modulate the electrochemical reactions in a controlled fashion.5 On the other hand, the large-scale synthesis of practical and stable clusters and single atoms of catalysts remains a significant challenge, because clusters and single atoms are too mobile and easy to sinter under realistic reaction conditions.6 To this end, atomic layer deposition (ALD), a promising technique for small size catalyst fabrication,5 provides the solution. Previous studies have revealed that ALD allows control of the morphology of the deposited metal, from discrete tiny nanoparticles to a continuous thin film, through the surface chemistry.7 In the presented study, we employ the ALD technique to fabricate single atoms and sub-nanometer clusters of Pt on the surfaces of graphene nanosheet support.8 The morphology, size, density and loading of Pt on graphene can be precisely controlled by simply adjusting the number of ALD cycles. High angle annular dark field scanning TEM (HAADF-STEM) and electrochemical characterizations were carried out to determine how the catalyst structure changes with adjusting the numbers of ALD cycles. Fig. 1a and b show the bright-field TEM image and HAADF-STEM image of Pt/graphene with 100 ALD cycles, respectively. On the bright-field TEM image, only Pt nanoparticles of 1–4 nm in size are observed (Fig. 1a). Interestingly, the sensitivity to atomic number Z-contrast of HAADF-STEM revealed, in addition to these Pt nanoparticles, the presence of numerous individual Pt atoms, as well as very small Pt clusters of size ≤1 nm consisting of only a few atoms (Fig. 1b). EDS, collected from different areas with Pt-clusters ranging from 1.2 to 6.7 nm size on a graphene nanosheet as well as an area containing only a few atoms, further confirmed the presence of Pt. The presence of Pt individual atoms and extremely small clusters suggests a strong interaction between graphene and Pt atoms, which may induce some modulation in the electronic structure of the Pt clusters. X-ray absorption fine structure (XAFS) spectroscopy, including both the X-ray Absorption Near Edge Structure (XANES) and the Extended X-ray Absorption Fine Structure (EXAFS), will be used to correlate the electronic structure and local environment of Pt and their electrochemical performance, and how it affects the methanol oxidation activity and CO adsorption. This work is anticipated to form the basis for the exploration of a next generation of highly efficient single-atom catalysts for various applications.

Water sorption behavior in polyimide thin films controlled by inorganic additives

We investigated the decreased water diffusivity depending on the content and size of carbon black (CB) added to polyimide (PI) in order to synthesize composite films (PI-CB). CBs with different diameters were used: N110 (CB1, 11–19 nm), N326 (CB2, 26–30 nm) and N660 (CB3, 49–60 nm). The water diffusion coefficient of PI-CB decreased with increasing CB content from 2.67·10−9 for pure PI films to 0.22·10−9 cm2/s for PI-CB films containing 40 wt% CB1. Moreover, the decrease in water diffusivity with increasing CB content exhibited a linear relationship. The water diffusivity of PI-CB increased with the increasing size of CB at the same CB content. The water uptake of PI-CB had a linear relationship depending on the CB content, similar to water diffusivity; the water uptake of composite films decreased by 73% (from 3.67% to 0.98%) for PI-CB1 (40 wt%) films as compared to PI films. In addition, the water uptake varied not only with the CB content, but also by the size of the CB surface area. Open image in new window

Epoxy Resin/Carbon Black Composites Below the Percolation Threshold

A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At room temperature, the dielectric permittivity is higher for epoxy loaded with CBH additives. In contrast, at high temperature, the electrical conductivity was found to be higher for composites with CBL embedded. The established influence of the CB surface area on the broadband dielectric characteristics can be exploited for the production of effective low-cost antistatic paints and coatings working at different temperatures.

Determination of surface area of carbon-black by simple cyclic-voltammetry measurements in aqueous H2SO4

Determination of the surface area of commercial carbon-black (CB) by cyclic-voltammetry (CV) measurements of the electrochemical double-layer charge (Q) in aqueous sulfuric acid was investigated. Various factors that affect the Q value associated with CB, including: the presence of redox-reversible function-groups, the binders used for the formation of thin-film CB electrodes, the scan rates of the CV measurement, H2SO4 electrolyte concentration and the volume of air contained in the pores of the CB samples were examined. Conditions for measuring Q without interference from these factors were investigated and the data derived, without interference, was found to correlate well with the surface area of the CB. The results show that the total Brunauer–Emmett–Teller (BET) surface area shows good correlation (R2=0.993) with the Q value corresponding to a full charge/discharge of the CB (Q0), obtained by extrapolation at a zero scan rate; additionally, the CB micropore surface area (diameter<2nm) shows good linear correlation with the Q deficiency (Q0–Q), measured at 5mVs−1 (R2=0.998).