The improvement of mechanical properties of conventional concretes using carbon nanoparticles using molecular dynamics simulation

Molecular nano-I-beam class of materials: options based on configuration, first principles-based optimization and properties

Nanotubes showed merits including high structural strength-to-weight ratio. However, tubes are less favored regarding stiffness and strength. Nano-I-beams are proposed for improved nano-mechanics. Computationally, the study proposes novel molecular designs of I-beam-like shaped structures. A conformation analysis, molecular dynamics and first principles-based optimization are presented. The study proposes options based on the configuration of the molecular nano-I-beam structure providing less number of planes of symmetry and hence more stability than nanotube-like structures. These designs feature a unique geometrical differentiator of having the walls of the out-of-plane hexagonal motif-based molecular nano-I-beam (C60H46) inclined with different inclination angles enabling promising properties. The stability of the proposed nano-I-beam is proved on par with the corresponding nanotube-like structure. First principles-based evidence is provided on the comparable polarizability and the comparable ability to store energy of the supercell of the crystalline slab nano-I-beam in comparison with the corresponding nanotube. A proposed hybrid octa-hexagonal-cubic molecular nano-I-beam (C24H12) remedies the nano-buckling observed in the alike square-octagonal nanostructure. The molecular nano-I-beam exhibits intrinsic switchability that enables the nano-I-beam to be a topological semiconductor/insulator. The results show promising electronic and elastic properties of the proposed nano-I-beams that suit several applications such as their use in capacitors, transistors, insulators, batteries, quantization-based nano-devices, solid lubricant additive to grease, toughening fibers of nanocomposites, hydrophobic films, emissions adsorbents, catalytic sensors, PAH materials for space, and sustainable energy. The molecular nano-I-beam provides the base of the corresponding 2-D crystalline slab nano-I-beams.

Pushing the limits of PLA by exploring the power of MWCNTs in enhancing thermal, mechanical properties, and weathering resistance

The present study focuses on enhancing the mechanical, thermal, and degradation behavior of polylactic acid (PLA) by adding carbon nanotubes (CNTs) with different concentrations of 0.5, 1, 3, and 5%. The CNTs were prepared using catalytic chemical vapor deposition, and the prepared PLA/CNTs nanocomposite films were characterized using techniques such as FT-IR, Raman spectroscopy, TGA, SEM, and XRD. The distinct diffraction patterns of multi-walled carbon nanotubes (MWCNTs) at 2θ angles of 25.7° and 42.7° were no longer observed in the prepared nanocomposites, indicating uniform dispersion of MWCNTs within the PLA matrix. The presence of MWCNTs enhanced the crystallinity of PLA as the CNT loading increased. Mechanical tests demonstrated that incorporating CNTs positively influenced the elongation at the break while decreasing the ultimate tensile strength of PLA. The PLA-3%CNTs composition exhibited the highest elongation at break (51.8%) but the lowest tensile strength (64 MPa). Moreover, thermal gravimetric analysis confirmed that the prepared nanocomposites exhibited greater thermal stability than pure PLA. Among the nanocomposites, PLA-5% CNTs exhibited the highest thermal stability. Furthermore, the nanocomposites demonstrated reduced surface degradation in accelerated weathering tests, with a more pronounced resilience to UV radiation and moisture-induced deterioration observed in PLA-3% CNTs.

Mechanical Properties of Cement Reinforced with Pristine and Functionalized Carbon Nanotubes: Simulation Studies

Concrete is well known for its compression resistance, making it suitable for any kind of construction. Several research studies show that the addition of carbon nanostructures to concrete allows for construction materials with both a higher resistance and durability, while having less porosity. Among the mentioned nanostructures are carbon nanotubes (CNTs), which consist of long cylindrical molecules with a nanoscale diameter. In this work, molecular dynamics (MD) simulations have been carried out, to study the effect of pristine or carboxyl functionalized CNTs inserted into a tobermorite crystal on the mechanical properties (elastic modulus and interfacial shear strength) of the resulting composites. The results show that the addition of the nanostructure to the tobermorite crystal increases the elastic modulus and the interfacial shear strength, observing a positive relation between the mechanical properties and the atomic interactions established between the tobermorite crystal and the CNT surface. In addition, functionalized CNTs present enhanced mechanical properties.

Structural control of a novel hierarchical porous carbon material and its adsorption properties

Novel hierarchical porous carbon materials (HPCs) were fabricated via a reactive template-induced in situ hypercrosslinking procedure. The effects of carbonization conditions on the microstructure and morphology of HPCs were investigated, and the adsorption of methylene blue (MB) on HPCs was explored. The as-prepared HPCs has a hierarchical micro-, meso- and macropore structure, which results from the overlap of hollow nanospheres possessing microporous shells and macroporous cavities. The carbonization temperature, carbonization time and carbonization heating rate played important roles in tailoring the nanostructures of HPCs. The BET specific surface area and micropore specific surface area can reach 2388 m² g^-1 and 1892 m² g^-1, respectively. Benefitting from the well-developed pore structure, the MB removal efficiency can exceed 99% under optimized conditions. The adsorption kinetics and thermodynamics can be well described by a pseudo-second-order model and Langmuir model, respectively. Furthermore, such adsorption was characterized by a spontaneous endothermic process.