Laura Peña-Parás

Antiwear and Extreme Pressure Properties of Nanofluids for Industrial Applications

This study investigates the effect of CuO, TiO2, Al2O3, and multiwalled nanotube (MWNT) nanoparticles at various treat rates on the tribological properties, namely, wear, coefficient of friction (COF), and pressure of seizure (poz), of metalworking fluids during lubricating processes in diverse industrial applications. Results are reported based on two methods: wear scar diameter (WSD) and COF by ASTM D5183 and poz by the Institute for Sustainable Technologies–National Research Institute (ITEePib) Polish method for testing lubricants under scuffing conditions. Results showed significant improvements with small filler concentrations of nanoparticles. CuO nanofluids showed a diminishment of 86% for WSD at 0.01 wt%, whereas TiO2 resulted in an increase in poz of up to ∼250% at 0.05 wt% compared to pure conventional fluid.

Synthesization, Characterization, and in Vitro Evaluation of Cytotoxicity of Biomaterials Based on Halloysite Nanotubes

Halloysite is an aluminosilicate clay that has been widely used for controlled drug delivery, immobilization of enzymes, and for the capture of circulating tumor cells (CTCs). Surface modification of halloysite by organosilanes has been explored to improve their properties. In this study halloysite clay nanotubes (HNTs) were functionalized by two different organosilanes: Trimethoxy(propyl)silane (TMPS), and Triethoxy(octyl)silane (EOS). Untreated and modified samples were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), thermogravimetrical analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Results showed a strong interaction of organosilanes with the chemical groups present in HNTs. Biocompatibility and cytotoxicity of these nanomaterials were determined using C6 rat glioblastoma cells. Our results indicate that prior to functionalization, HNTs show a high biocompatibility and low cytotoxicity. However, HNTs functionalized with EOS and TMPS showed high cytotoxicity by inducing apoptosis. These results allow the identification of potential applications in biomedical areas for HNTs.

Extreme pressure properties of nanolubricants for metal-forming applications

Purpose – The purpose of this paper is to evaluate the extreme pressure properties of CuO and TiO2 nanoparticle additives with the incorporation of a surfactant within a synthetic fluid for metal-forming applications. Design/methodology/approach – The paper studies the effect of CuO and TiO2 nanoparticle additives at various concentrations (0.01, 0.05 and 0.10 wt. per cent) in a synthetic lubricant fluid under extreme pressure conditions. Oleic acid surfactant is added to the nanolubricant to improve dispersion and stability of nanoparticles. Extreme pressure tribological tests are performed on a four-ball T-02 tribotester according to the ITEePib Polish method for testing lubricants under conditions of scuffing. Findings – The results show that the addition CuO and TiO2 nanoparticles under the presence of OA resulted in an increase of the load-carrying capacity (poz) of the lubricant up to 137 and 60 per cent, respectively. The seizure load was also increased by 50 and 15 per cent, respectively. Practica...

2D-Based Nanofluids: Materials Evaluation and Performance

Advancement in technology demands the successful utilization of energy and its management in a greater extent. Thermal energy management plays a crucial role from high-payload electrical instruments to ultra-small electronic circuitries. The advent of nanofluids that happened in the 1990s successfully addressed the low thermal efficiency of conventional fluids in a significant manner. The ground-breaking report on the concept of “nanofluids for thermal management” led to the development of numer‐ ous thermal fluids using nanofillers of ceramics, metals, semiconductors, various carbon nanostructures, and composite materials. Later, demonstration of two-dimensional (2D) nanomaterials and their successful bulk synthesis led to the development of highly efficient fluids with even very low filler fractions. Introduction of 2D materials into fluids also brought out the multifunctional aspects of fluids by using them in tribolo‐ gy. In this chapter, we narrate the advances in thermal nanofluids and the develop‐ ment of novel fluids with the discovery graphene. Multifunctional aspects of these fluids are discussed here. To support the experimental observation, a theoretical platform is discussed and its predictions are correlated on the basis of existing data. The chapter has been concluded with a brief discussion on futuristic aspects of nanofluids in reallife applications. This chapter aims to focus on the description of the thermal trans‐ port, tribological behavior, and aspects that involve the use of 2D-based nanofluids, from various 2D nanostructures such as h-BN, MoS2, WS2, graphene, among others. The homogeneous nanoparticle distribution within conventional fluids and the results from the thermal transport and tribological tests and observations are included. The nanofluids under investigation belong mainly to dielectric and metal-mechanic lubricants. Also, the mechanisms that promote these effects on the improvement of nanofluids properties are considered.

Temperature dependence of the extreme-pressure behavior of CuO and TiO2 nanoparticle additives in metal-forming polymeric lubricants

Purpose The purpose of this work is to investigate the effect of temperature on the extreme-pressure (EP) properties of CuO and TiO2 nanoparticle-filled polymeric lubricants for metal-forming processes. Design/methodology/approach This paper studies the effect of nanoparticle additives of CuO and TiO2 on the load-carrying capacity of a metal-forming polymer lubricant used for deep-drawing at varying temperatures. EP measurements are performed with a four-ball tribotester according to the ITeE-PIB Polish method for testing lubricants under scuffing conditions. Tests are run at 25, 40, 60 and 75°C to further decrease the lubricant film thickness and determine the effect on the load-carrying capacity and the tribological mechanisms of nanoparticles. The tribological mechanisms of nanoparticles is studied using energy dispersive spectrometry (EDS). Findings Results indicate that nanoparticle additives increase the load-carrying capacity of the polymeric lubricant at all concentrations up to 60°C attributed to a mending effect and a reduction in the area of contact of moving surfaces; at 75°C, the improvement is lowered due to nanoparticle re-agglomeration. The best results are found with TiO2 nanoparticles due to their smaller size compared to CuO. Practical implications Nanoparticles of CuO and TiO2 are potential EP additives for metal-forming lubricants, providing protection to working components and extending tool life. Originality/value These results show the effectiveness and the tribological mechanisms of nanoparticle additives under EP conditions and increasing temperatures found in metal-forming processes.