Rene Francisco Boschi Gonçalves

The N₅⁻ anion, known as pentazolate, represents a groundbreaking advancement in the field of energetic materials, offering promising applications in rocket propulsion, explosive devices, and pyrotechnics. Comprising five nitrogen atoms arranged in a cyclic structure with a negative charge, has captured significant interest due to its unique configuration and high energy potential. In this article, we provide a comprehensive overview of the N₅⁻ anion’s potential as an energetic material, alongside the role of RMD simulations in elucidating its behavior. The ReaxFF forcefield was used to simulate the materials pyrolysis. The total energy behavior of different species containing pentazolate, across a range of temperatures (1500 K to 3000 K) revealed distinct trends and characteristics associated with the thermal dynamics and stability of the molecule under varying thermal conditions. Their mechanisms were elucidated, and the kinetic parameters were calculated, indicating that CNN₅, with its low activation energy (39.14 kJ/mol), stands out as the most reactive, while PolyN₅, with the highest activation energy (52.88 kJ/mol), is the most stable. Overall, the N₅ ^- anion represents a promising avenue for the development of high-energy materials.

Currently, it is crucial for the lubricant formulation industry to explore cost-effective and environmentally friendly methodologies for analyzing the tribological properties of engine aviation lubricants under high-temperature and high-pressure operating conditions. This study demonstrates the feasibility of employing molecular dynamic simulations to gain essential insights into the evolution of the tribological properties of lubricants during operation. A three-layer molecular model was devised, comprising nickel aluminide molecules in the top and bottom layers, and polyol ester in the core. The impact of sliding velocities ranging from 20 km/h to 100 km/h was investigated under varying temperature and pressure conditions. Concentration, temperature and velocity profiles, radial distribution function, mean square displacement, and friction coefficient were calculated and analyzed in detail. Notably, the highest friction coefficients – ranging from 2.5 to 0.75 - were observed at the lowest temperature and pressure conditions tested. Conversely, other sections of the gas turbine exhibited substantially lower friction coefficients – ranging from 0 to 0.01.Simulations demonstrate that increasing pressure and temperature reduce polymer chain mobility, leading to stronger internal interactions within the lubricant. Consequently, lubricant adsorption onto metal surfaces decreases. Furthermore, the lubricant performs exceptionally well when its molecules encounter higher velocities and temperatures. Based on the results obtained, the research demonstrates that the presented technique provides both quantitative and qualitative tribological information essential for understanding a system molecular behavior, serving as a guiding framework for researchers in the field.

Portland cement concrete remains the most important of the materials used due to its mechanical properties combined with its low cost and ease of obtaining. However, conventional concrete structure suffers aging with gradual increase in porosity. This implies limitations and leads to the development of modifications to improve its general characteristics, like the so-called concrete modified by polymers that resulted in improvements in mechanical and microstructural properties, in relation to the original concrete. Concrete (cement)-polymer composites are the materials, which are made by replacing a part or all the cement hydrate binders of conventional mortar or concrete with polymers and by strengthening the cement hydrate binder with polymers. The composites are generally classified into three types by the principles of their process technology: 1. Polymer-modified mortar and concrete; 2. Polymer mortar and concrete; and 3. Polymer impregnated mortar and concrete. In this study, we evaluated the effect of the addition of the acrylic additive in the hydration reaction, comparing the result between the cement paste samples with and without added polymer. Beyond mechanical tests, such as compression resistance and traction, various thermal analysis techniques were used. The results showed great modifications on hydration process and mechanical behavior of PMC.

Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings. This paper presents a comparison of recorded pressure that was reflected on the surface of reinforced concrete slabs with and without EPS (Expanded Polystyrene) foam retrofit measured from a detonation of 2.7 kg of non-confined plastic explosive. Two 50 MPa reinforced concrete slabs measuring 1.0x1.0x0.08 m, simply supported on two sides were tested. The explosive was suspended at a distance of 2.0 m from the upper surface of the slabs; one of the slabs had 5.0 cm thick foam on the top side. Eight piezoelectric pressure sensors were positioned at a distance of 2.0 m from the explosive. Results showed that the foam retrofit reduced the reflected pressure by approximately 57% when compared to the slab without EPS foam retrofit.