Characterisation of carbon blacks produced by solar thermal dissociation of methane

Solar methane dissociation appears as a possible route toward a hydrogen-based economy. The competitiveness of the process strongly depends on the carbon black properties and economic value. At CNRS-PROMES, a 50 kW tubular solar reactor was developed to produce carbon black and hydrogen from methane. The reaction was carried out in a graphite receiver crossed by seven graphite tubes heated up by concentrated solar radiations at the 1 MW CNRS solar furnace. The temperatures ranged between 1608 K and 1928 K and the methane flow-rates varied from 10.5 to 21 NL/min. Total methane dissociation was reached with hydrogen yield higher than 80% and the carbon yield was drastically affected by the acetylene by-product. The carbon samples were analysed in detail and their properties were compared to a commercial conductive grade carbon black. Transmission electron microscopy showed primary particles of 10–70 nm diameter. The crystallinity of the samples was characterised by Raman spectroscopy. It was also possible to correlate the specific surface area with the reaction temperature and with the concentrations of residual methane and of the acetylene by-product. The resistivity and the structure of the agglomerates were determined by simultaneous measurements of the conductivity and the density under compression.     

Meeting application requirements with conductive carbon black

High structure or so‐called conductive carbon blacks (CCBs) constitute the major family of conductive additives. They enable one to make polymers permanently conductive at “low” to “very low” loadings, for technical applications involving, e.g., the transport of energy, protection against arcing or discharge. Designing conductive parts requires certain know‐how, as many parameters influence the final electrical conductivity, and many other requirements have to be fulfilled. This paper highlights the impact of the carbon black (CB) type and loading, the polymer type, and the compounding conditions on the conductive, mechanical, dispersion, and flow properties of various plastics compounds. The study especially positions a unique family of low surface area (LSA) CCBs, suggests means to make conductive parts with compounding and transformation ease, and points out that more conductive additive does not automatically give the best overall performance. J. VINYL. ADDIT. TECHNOL., 12:14–18, 2006. © 2006 Society of Plastics Engineers     

Structure and electrical properties of carbon black

The incorporation of conductive particles into a polymer matrix modifies fundamentally the electrical conductivity of the composite. The importance of carbon black structure on other mechanical and rheological properties is also well documented. Besides common techniques, like DBP-absorption and CDBP-absorption, void-volume, determined by the measurement of the volume of a given quantity of carbon black under a given pressure, has been considered as a more absolute technique. The present work considers the void-volume technique under a broader angle. The evolution of the volume of a given carbon black weight under increasing pressure as well as the evolution of the electrical resistivity is recorded and analysed.     

Development of carbon conductive additives for advanced lithium ion batteries

The newly developed conductive carbon blacks C-NERGY™ Super C65 and C-NERGY™ Super C45 were studied with regard to their performance as conductive additives in positive lithium ion battery electrodes and compared to other reference conductive carbon blacks. The lowest electrical volume resistivity and highest compressibility were found for C-NERGY™ Super C45 dry-mixed with LiCoO₂ powder. Mixing by high shear forces in acetone dispersion improved the electrical resistivity and compressibility of the C-NERGY™ Super C65 containing LiCoO₂ mixture to the same level obtained for the C-NERGY™ Super C45 mixture in the same process. Acetone dispersions of C-NERGY™ Super C45 and LiCoO₂ showed the lowest viscosities attributed to the carbon black's specific BET surface area of 45 m² g⁻¹ being the lowest of all carbon blacks studied. The easy dispersibility of C-NERGY™ Super C45 in LiCoO₂ could be explained by its particular surface group chemistry characterized by time-of-flight secondary ion mass spectrometry. The electrical volume resistivity of the LiCoO₂/carbon black mixtures was in line with the high current rate performance of half-cells with related LiCoO₂ electrodes. Compared to the investigated carbon blacks, the electrical volume resistivity of the graphite conductive additives C-NERGY™ KS6L and C-NERGY™ SFG6L at different concentrations in LiCoO₂ powders showed higher critical volume fractions but lower ultimate resistivity levels. Adding one of these graphites to the carbon black conductive mass improved the electrode density and, at concentrations above the critical volume fraction of the graphite component, significantly decreased the ultimate resistivity level of the LiCoO₂ electrode mass.     

Differentiation of Romanian Wines on Geographical Origin and Wine Variety by Elemental Composition and Phenolic Components

Several wines were analyzed by high-performance liquid chromatography (HPLC-PDA), inductively coupled plasma mass spectrometry (ICP-MS), and flame atomic absorption spectroscopy (FAAS) in order to associate the concentration levels of the chemical parameters with the geographical origin of wines and wine varieties. Thus, the concentrations of 22 elements (Li, Be, Co, Ni, Cs, U, Pb, V, As, Ba, Cr, Cu, Zn, Al, Mn, Rb, Sr, Fe, Ca, Mg, Na, and K) and seven phenolic compounds (gallic acid, (+)-catechin, (?)-epicatechin, p-coumaric acid, ferulic acid, trans-cinnamic acid, and resveratrol) were analyzed in 22 wines from two different wine-producing areas of Romania. Among the phenolic compounds, (+)-catechin, (?)-epicatechin, p-coumaric acid, ferulic acid, and resveratrol concentrations were the most useful markers for wine differentiation by geographical origin and wine variety, whereas Ba, Be, Cr, Cs, Li, Mg, Na, Ni, Sr, U, and Zn were the main inorganic parameters selected. To explore the distribution pattern of the samples, aimed at differentiating the wine samples by geographical region and wine variety, principal component analysis (PCA) was applied to the obtained data.     

Pd-decorated CNT as sensitive material for applications in hydrogen isotopes sensing - Application as gas sensor

Applicability of multiwall carbon nanotubes (MWCNTs) decorated with palladium nanoparticles as sensitive layer in a resistive microsensor for identification of hydrogen isotopes, Deuterium (²H) and Protium (¹H), has been demonstrated. Palladium nanoparticles were anchored on the MWCNTs surface via a chemical process involving micellization, from a precursor chloride solution, in high ultrasonic density field. Pd-MWCNTs are quasi-aligned between the interdigitated gold electrodes of a SiO₂ substrate by drop casting and di-electrophoretic alignment in Tetrahydrofuran (THF) and Nafion solution. The morphostructural characterization of the sensitive material has been carried out through SEM, TEM and Raman spectroscopy and its gas sensing properties were evaluated using electrical measurements performed on a series of isotope concentrations (ranging from 0.1% up to 1%, and from 1% to 4%, value to which hydrogen becomes explosive) diluted in argon, to observe the evolution of the sensor sensibility. The two hydrogen isotopes have different behaviors related to the adsorption on the Pd-MWCNT, which is well observed in the resistance change. Therefore, the sensor based on Pd-MWCNTs could be a viable solution to be integrated in systems for hydrogen leakage detection.     

Neural networks-based adaptive control for a class of nonlinear bioprocesses

The paper studies the design and analysis of a neural adaptive control strategy for a class of square nonlinear bioprocesses with incompletely known and time-varying dynamics. In fact, an adaptive controller based on a dynamical neural network used as a model of the unknown plant is developed. The neural controller design is achieved by using an input–output feedback linearization technique. The adaptation laws of neural network weights are derived from a Lyapunov stability property of the closed-loop system. The convergence of the system tracking error to zero is guaranteed without the need of network weights convergence. The resulted control method is applied in a depollution control problem in the case of a wastewater treatment bioprocess, belonging to the square nonlinear class, for which kinetic dynamics are strongly nonlinear, time varying and not exactly known.     

Production of Carbon Nanotubes and Other Nanostructures Via Continuous 3-Phase AC Plasma Processing

The highly flexible plasma system allows the independent flow control of plasma gas, carbonaceous feedstock and metal catalyst. Further important control parameters include current intensity and product quenching rate yielding in an excellent control of the thermal history of the carbon products. Temperature profiles measured along the reactive flow of carbon particles are presented, mapping time-temperature relations for typical operating conditions. In addition, the principle product families are presented. From the characteristics observed and NT product analysis, it is concluded that the AC plasma technology shows a significant potential for the continuous production of bulk quantities of carbon-based nanotubes of controlled properties and novel tube-like nanostructures.     

Bupivacaine‐loaded chitosan hydrogels for topical anesthesia in dentistry

The paper describes the preparation of polymeric hydrogels, loaded with bupivacaine, which could represent a good alternative in clinical dentistry as local anesthetics. The hydrogels were prepared by condensation using an amidation reaction between a natural polymer (chitosan) and a synthetic one, poly[(maleic anhydride)‐alt‐(vinyl acetate)]. Infrared spectroscopy studies confirmed crosslinking through the presence of amide bonds, formed between the two types of polymer chains. Scanning electron microscopy results demonstrated that the hydrogels have a porous structure, the pore dimensions being non‐uniform with diameters between 200 and 600 μm. Hydrogels presented good bupivacaine inclusion and release capacity whereas theoretical analysis confirmed the validity of the generalized fractal model, reinforcing a csavi‐universal pattern of drug release. Cytotoxicity tests on human dermal fibroblasts revealed that the obtained hydrogels are not cytotoxic. In vivo, the bupivacaine‐loaded hydrogels presented anesthetic effects after 15 min and no side effects were observed. This system has the advantage of alleviating or eliminating pain associated with invasive procedures and avoiding direct contact of the drug with tissues, leading thus to the prevention of side effects. © 2020 Society of Chemical Industry     

Elemental Profile and <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr Isotope Ratio as Fingerprints for Geographical Traceability of Wines: an Approach on Romanian Wines

Wine geographical traceability is an important topic in the context of wine authentication and for that, many researchers worldwide have addressed this subject by developing different methodologies based on multivariate analysis of natural chemical composition data (inorganic or organic parameters) and isotopic signature. The goal of this work was to assess the potential of elemental composition and strontium isotope ratio (⁸⁷Sr/⁸⁶Sr) of wines from important wine-producing regions in Romania, located in relatively small geographical areas, in order to highlight reliable markers for wine geographical origin discrimination. Elemental profile determinations were performed by ICP-MS, GFAAS, and FAAS techniques after microwave acid digestion of the wine samples. The ⁸⁷Sr/⁸⁶Sr isotope ratio of the resulted extracts was determined by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), after separating strontium and rubidium using cation-exchange chromatography with Dowex 50W-X8 resin and the complexation ability of the carboxylic acid EDTA. The variation of elemental composition (Ga, Sr, and Al), Ca/Sr ratio, and the ⁸⁷Sr/⁸⁶Sr ratio of the investigated wine clearly demonstrated that these variables are suitable tracers for wine geographic origin determination. The proposed methodology allowed a 100 % successful classification of wines according to the region of provenance.