Carbon research

C, Vol. 5, Pages 35: A Simple Two-Step Process for Producing Strong and Aligned Carbon Nanotube-Polymer Composites In this paper, we present the results of a study related to fabrication of polymer-aligned carbon nanotube (CNT) composites made with different thermoplastic polymers. These composites have been manufactured by employing a simple two-step process using the internal resistive heating approach. The resulting composites have shown improved tensile strength, load, and elastic modulus compared to pristine CNT sheets. Poly (methyl methacrylate) (PMMA)-CNT, UltemTM-CNT and thermoplastic polyurethane (TPU)-CNT composites showed an increase in tensile strength by as much as 41%, 77% and 86% respectively over pristine CNT sheets. The improvement in tensile strength is the result of a good adhesion achieved between the aligned CNTs and polymer as observed with transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

C, Vol. 5, Pages 34: Mechanical Behavior of Porous Functionally Graded Nanocomposite Materials Materials used in biomedical applications need to cope with a wide set of requisites, one of them being their structural adequacy to a specific application. Thus, it is important to understand their behavior under specified standard cases, namely concerning their structural performance. This objective constituted the focus of the present study, where nanocomposite functionally graded materials integrating different porosity distributions were analyzed. To this purpose a set of numerical simulations based on the finite element method, reproducing American Society for Testing and Materials (ASTM) tensile and bending tests were considered. The results obtained show a good performance of the models implemented through their preliminary verification. It is also possible to conclude that carbon nanotubes and porosity distributions provide different and opposite effects in the context of the nanocomposite materials analyzed.

C, Vol. 5, Pages 33: Carbon Dots for Sensing and Killing Microorganisms Carbon dots (or carbon quantum dots) are small (less than 10 nm) and luminescent carbon nanoparticles with some form of surface passivation. As an emerging class of nanomaterials, carbon dots have found wide applications in medicine, bioimaging, sensing, electronic devices, and catalysis. In this review, we focus on the recent advancements of carbon dots for sensing and killing microorganisms, including bacteria, fungi, and viruses. Synthesis, functionalization, and a toxicity profile of these carbon dots are presented. We also discuss the underlying mechanisms of carbon dot-based sensing and killing of microorganisms.

C, Vol. 5, Pages 32: Chemical Recycling of Consumer-Grade Black Plastic into Electrically Conductive Carbon Nanotubes The global plastics crisis has recently focused scientists’ attention on finding technical solutions for the ever-increasing oversupply of plastic waste. Black plastic is one of the greatest contributors to landfill waste, because it cannot be sorted using industrial practices based on optical reflection. However, it can be readily upcycled into carbon nanotubes (CNTs) using a novel liquid injection reactor (LIR) chemical vapor deposition (CVD) method. In this work, CNTs were formed using black and white polystyrene plastics to demonstrate that off-the-shelf materials can be used as feedstock for growth of CNTs. Scanning electron microscopy analysis suggests the CNTs from plastic sources improve diameter distribution homogeneity, with slightly increased diameters compared with control samples. Slight improvements in quality, as determined by Raman spectroscopy of the D and G peaks, suggest that plastics could lead to increased quality of CNTs. A small device was constructed as a demonstrator model to increase impact and public engagement.

C, Vol. 5, Pages 31: Microbiological Properties of Microwave-Activated Carbons Impregnated with Enoxil and Nanoparticles of Ag and Se Microwave-activated carbons from walnut shells (ACMW) were impregnated with Ag and Se nanoparticles and with the Enoxil biologically active preparation, and the microbiological properties of the obtained composites were studied. To increase the functionality of the adsorbent, the activated carbon was oxidized with ozone, resulting in ACMWO containing aliphatic and aromatic carboxylic groups. There was a considerable decrease in the specific surface of the activated carbon after the oxidation process. Nitrogen adsorption was used to determine the structural parameters of the activated carbons. A simultaneous thermal analysis was used to study the thermal behavior of intact and oxidized activated carbons. Infrared spectroscopy was applied to analyze the surface chemistry of the adsorbents. The microbiological activity of the activated carbons was studied using Escherichia coli bacteria and Candida albicans fungi. The kinetic study of the microbiological activity allowed the estimation of the bactericidal/fungicidal action time of the activated carbons.

C, Vol. 5, Pages 30: Mechanothermal Approach for N-, S-, P-, and B-Doping of Carbon Nanotubes: Methodology and Catalytic Performance in Wet Air Oxidation The texture and the surface chemistry of carbon nanotubes (CNTs) were modified using a solvent-free methodology involving a ball-milling mechanical treatment and thermal treatment under nitrogen in the presence of adequate precursors (melamine, sodium thiosulfate, sodium dihydrogen phosphate, and boric acid) of different heteroatoms (N, S, P, and B, respectively). The incorporation of these heteroatoms promotes significant changes in the pristine textural and chemical properties. This easy post-doping method allows the introduction of large concentrations of heteroatoms. Their effect on the catalytic activity of the materials was evaluated in the oxidation of oxalic acid by catalytic wet air oxidation (CWAO), as an alternative to the noble metal and rare earth oxide catalysts traditionally used in this process. Improved catalytic activities were obtained using the N-, P-, and B-doped CNTs in oxalic acid oxidation, while the S-doped CNT sample underperformed in comparison to the pristine material.

C, Vol. 5, Pages 29: The Advances in Biomedical Applications of Carbon Nanotubes Unique chemical, physical, and biological features of carbon nanotubes make them an ideal candidate for myriad applications in industry and biomedicine. Carbon nanotubes have excellent electrical and thermal conductivity, high biocompatibility, flexibility, resistance to corrosion, nano-size, and a high surface area, which can be tailored and functionalized on demand. This review discusses the progress and main fields of bio-medical applications of carbon nanotubes based on recently-published reports. It encompasses the synthesis of carbon nanotubes and their application for bio-sensing, cancer treatment, hyperthermia induction, antibacterial therapy, and tissue engineering. Other areas of carbon nanotube applications were out of the scope of this review. Special attention has been paid to the problem of the toxicity of carbon nanotubes.

C, Vol. 5, Pages 28: Preparation of Few-Layer Graphene/Carbon Nanotube Hybrids Using Oxide Spinel Catalysts Functional 3D materials can be developed from graphene-based hybrids by introducing other nanomaterials, with multi-walled carbon nanotubes (CNTs) being the most studied additive. For large-scale applications, few-layer graphene (FLG)-CNT hybrids are produced by catalytic chemical vapor deposition (c-CVD) starting from a mixture of catalysts (one for FLG and one for CNTs) in the required proportions. Due to the difference in growth kinetics between CNTs and FLG, the composition of such hybrids is not well controlled. In this study, we report the single-step preparation of FLG-CNT hybrid materials by a fixed-bed c-CVD process using a single catalyst with the formula AlxCo1−xFe2O4 (x = 0.025–0.10). Different catalysts (with varying x) were prepared by the citrate–nitrate gel combustion method. Then, c-CVD synthesis was carried out at 650 °C in a horizontal fixed-bed reactor using ethylene as the carbon source. Only FLG was obtained when using CoFe2O4. However, the introduction of small amounts of Al (x < 0.05) induced the simultaneous production of CNTs, leading to the formation of uniform FLG-CNT hybrids. For catalysts with higher Al content (e.g., AlCoFeO4), CNTs were selectively produced. Thus, we observed the existence of a narrow Al-doping window, where CNTs and FLG can be obtained simultaneously. Our results can pave the way to developing high-yield single catalyst-based CVD synthesis of FLG-CNT hybrid materials.

C, Vol. 5, Pages 27: Methods for the Treatment of Cattle Manure—A Review Environmental concerns, caused by greenhouse gases released to the atmosphere and overrunning of nutrients and pathogens to water bodies, have led to reducing direct spread onto the land of cattle manure. In addition, this practice can be a source of water and air pollution and toxicity to life by the release of undesirable heavy metals. Looking at the current practices, it is evident that most farms separate solids for recycling purposes, store slurries in large lagoons or use anaerobic digestion to produce biogas. The review explores the potential for cattle manure as an energy source due to its relatively large calorific value (HHV of 8.7–18.7 MJ/kg dry basis). This property is beneficial for thermochemical conversion processes, such as gasification and pyrolysis. This study also reviews the potential for upgrading biogas for transportation and heating use. This review discusses current cattle manure management technologies—biological treatment and thermochemical conversion processes—and the diverse physical and chemical properties due to the differences in farm practices.

C, Vol. 5, Pages 26: Highly Active, High Specific Surface Area Fe/C/N ORR Electrocatalyst from Liquid Precursors by Combination of CO2 Laser Pyrolysis and Single NH3 Thermal Post-Treatment This paper reports original results on the synthesis and characterization of Fe/C/N ORR electrocatalysts obtained by a combination of CO2 laser pyrolysis and thermal post-treatment. The precursor liquid media, consisting in a 14 g·L−1 iron III acetylacetonate solution in toluene, was aerosolized and then exposed to a CO2 laser beam for pyrolysis in continuous flow. Ammonia was used in the pyrolysis process, both as the laser wavelength absorbing gas (i.e., energy transfer agent) and as the sole source of nitrogen. After the laser pyrolysis step, the material was submitted to thermal post-treatment under argon on the one hand, and ammonia on another hand. The three materials—one as-prepared, one thermally treated under argon, and one thermally treated under ammonia—were characterized, in particular, through specific surface area determination, XPS analysis, and ORR measurement. It was found that both kinds of thermal treatment significantly improved the ORR performances, which were evaluated on porous electrodes. Indeed, while the as-prepared material showed an ORR onset potential at ≈790 mV vs. the standard hydrogen electrode (SHE) in HClO4 1M, the argon treatment increased the latter to ≈820 mV, and the ammonia treatment led to a very high value of ≈910 mV. Selectivities of 3.65 and 3.93 were measured for the argon and ammonia treated materials, respectively. The outstanding ORR performance resulting from the ammonia treatment is probably related to the very high BET specific surface area measured at 1130 m2·g−1, which was notably obtained without using any templating or sacrificial component in the precursor media.