Jorge Bedolla Hernández

Nanostructured chromium coatings have attracted considerable attention due to their mechanical, tribological, and corrosion-resistant properties, making them suitable for demanding industrial applications. Electrodeposition assisted by chromium nanoparticles (CrNPs) represents a promising approach for producing high-performance coatings while reducing the environmental and health concerns associated with conventional hexavalent chromium processes. This chapter analyzes the scientific principles governing the electrodeposition of nanostructured chromium coatings, emphasizing the electrochemical and physicochemical phenomena controlling coating formation. Charge transfer, electrical double-layer formation, Butler–Volmer kinetics, Faraday’s laws, mass transport, hydrodynamic behavior, nucleation, and crystal growth are discussed to establish the relationship between operating conditions and coating evolution. Particular attention is given to applied potential, current density, deposition time, nanoparticle concentration, temperature, and mechanical stirring, on nucleation density, growth kinetics, coating morphology, and deposit continuity. The theoretical framework is complemented by an experimental study of chromium nanoparticle-assisted electrodeposition onto AISI 1020 steel substrates under controlled operating conditions. Deposition time, nanoparticle concentration, and stirring speed were systematically varied while maintaining constant electrical parameters. The resulting coatings were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to evaluate morphology, continuity, and elemental composition. Experimental observations indicate that mass transport and hydrodynamic conditions strongly influence nanoparticle availability at the cathode surface, affecting nucleation, coating growth, and microstructural evolution. Integrating electrochemical theory with experimental evidence provides guidelines for optimizing operating conditions to obtain uniform, reproducible, and environmentally sustainable nanostructured chromium coatings.

A prosthetic scheme is presented for the design of transtibial lower limb prostheses for replacement in users with moderate energy activities. It is based on elastic and rigid components that allow energy storage and return during the gait phases. The design is based primarily on the location of the centres of mass of the biological regions that are being replaced. A computational tool was developed to support the design, which calculates the location of the centres of mass. The results were verified against those obtained from healthy biological limbs of a population ranging in height from 150 cm to 189 cm. The calculation tool was found to have a variation of around 1%, which is considered acceptable and favours the stability of the prosthesis and its overall interaction to achieve a viable and functional design.

In this work, the tensile behaviour of an isolated maguey manso cuticle is studied from an engineering perspective. The maguey manso is a plant in the Agavaceae family that grows in the semi-dry and cold Central Valley of Mexico, among the States of Mexico, Hidalgo, Puebla and Tlaxcala. The leaves of a maguey, known as pencas, are formed basically by sap, fibers along their full length, and the cuticle. It was found that the maguey cuticle behaves as a viscoelastic material. Once the tensile stress is reached, the cuticle breaks catastrophically in a brittle way. Scanning electron microscopy reveals that the complex and homogeneous microstructural arrangement of stomata in the cuticle contributes to anisotropic and brittle crack propagation behaviour, due to preferential stomatal alignment.

This study conducts a comparative performance analysis of three different low-temperature solar collector systems: flat plate solar collectors (FPCs), heat pipe evacuated tube solar collectors (HPETCs), and heat pipe flat plate solar collectors (HPFPCs). Key performance parameters, such as heat transfer coefficients, useful heat, and thermal efficiency, are analyzed under varying mass flow rate, fluid temperature, and antifreeze concentration. The objective is to evaluate the thermal performance of these systems using different heat transfer fluids, specifically water, and mixtures of 30% and 50% ethylene glycol and propylene glycol. The performance data indicate that the heat transfer coefficient in the HPFPC diminishes by 28% and 41% when antifreeze is employed at concentrations of 30% and 50%, respectively. Furthermore, the integration of heat pipes with water in a flat plate solar collector results in efficiency enhancements, with respect to FPCs, of up to 13% at a fluid temperature of 30 °C, and up to 21% at 80 °C. At the elevated fluid temperature of 80 °C, an efficiency increase of 13% is observed with a 30% ethylene glycol concentration. The incorporation of heat pipes leads to an efficiency improvement of up to 6.5% in comparison to traditional flat plate solar collectors. This study highlights the significant impact of fluid properties, affecting the convective heat transfer coefficient, on the overall efficiency of solar collectors, emphasizing the importance of optimizing fluid composition and operating conditions for enhanced thermal performance.

A concept for the design of energy absorber system is presented, which consist basically of tube type structural elements coupled. The system considers the absorbed energy for levels of kinetic energy corresponding to similar fall arrest systems used to prevent injuries during fall incidents. The energy dissipation in the proposed passive system is developed by means of mechanical contact, friction phenomena and plastic strain. The analysis of conditions in the system is supported by the finite element software Abaqus, which permits the simplification of the body fall process. The application of structural elements in the system is based in its mechanical characteristic for energy dissipation by deformation. Plastic deformation in structural tubes is an irreversible process, which is a desirable condition for fall arrest systems. Finally, the numerical results to show the dissipation of kinetic energy in the proposed system are presented.