Author: JOSE MANUEL OROZCO HERNANDEZ
In order to improve the enzymatic production of biodiesel, the reuse of an immobilized preparation of Candida antarctica lipase B (CALB) was assayed under di ff erent conditions. The improvement included: (1) reuse of CALB in the presence of ethanol (EtOH), (2) reuse of CALB in the presence of methanol (MeOH), (3) blended alcohols at di ff erent molar ratios (0:100, 20:80, 40:60, 50:50, 60:40, 80:20 and 100:0, %EtOH:%MeOH), and employing second generation raw materials: waste cooking oil (WCO) and castor oil (CO). When the first strategy was carried out the FAEE (fatty acid ethyl ester) content achieved was 96% in a first cycle but after four cycles the percentage decreased to 32%. For the second strategy the FAME (fatty acid methyl ester) content attained was 63% in a first cycle but after four cycles the percentage was only 13.5%. When the blended alcohols were tested, the negative e ff ect of MeOH was evident for higher concentrations regardless the type of oil used.
In the present study, the microstructure evolution of WC-10Co-4Cr powder deposited on AISI-SAE 1020 steel substrate by laser cladding was evaluated, considering the effect of average energy per unit area. Single tracks were obtained by employing a Yb: YAG laser system with selected processing parameters. All samples were sectioned in the transverse direction for further characterization of the cladding. Results showed that dilution lay within 15% and 25%, whereas porosity was measured below 12%. According to microstructural analyses, considerable grain growth is developed within the central area of the cladding (namely, the inner region); additionally, the development of a triangular and/or polygonal morphology for WC particles along with a clear reduction in hardness was observed when employing a high average energy. It is worth noting that, in spite of the rapid thermal cycles developed during laser cladding of WC-10Co-4Cr, grain growth is attributed to a coalescence mechanism due to complete merging of WC into larger particles. Finally, the presence of small round or ellipsoidal particles within the inner region of the cladding suggested that non-merged particles occurred due to both an inhomogeneous dispersion and the lack of faced-shaped WC particles.
Author contributions: Conceptualization-data curation, E.A.L.-B.; E.A.L.-B. and V.H.B.-H.; Formal analysis, V.H.B.-H. and J.J.R.-M.; Investigation, E.A.L.-B. and H.R.-L.; Methodology, E.A.L.-B., H.R.-L., V.H.B.-H., J.J.R. M., J.I.-M. and J.M.A.-O.; Validation, E.A.L.-B.; Writing—original draft, E.A.L.-B. and V.H.B.-H.; Writing—review and editing, J.I.-M. and J.M.A.-O.
Funding: Enrique A. López Baltazar wants to thank the Mexican National Council on Science and Technology (Conacyt) for the financial support during this research project. This research was funded by Universidad Autónoma de Zacatecas, CIDESI and COMIMSA, México. This project was partially funded by CONACYT AEM Project 275781.
Acknowledgments: Haideé Ruiz-Luna wants to thank the program Cátedras-Conacyt and the projects no. 254731-INFRA-2015 and 270613-INFRA-2016. Juansethi Ibarra-Medina is commissioned as a CONACYT Research Fellow at the Center for Engineering and Industrial Development (CIDESI) (Project: Catedras 2017 - num. 57). Juansethi Ibarra-Medina also acknowledges the Conacyt Consortium in Additive Manufacturing (CONMAD) for the use of experimental facilities for this work.
Conflicts of Interest: The authors declare no conflict of interest.