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This article reports the preparation of Co3O4 phase films by sol-gel. Initially, the precursor solution was prepared by the reaction of cobalt acetate tetrahydrate with methanol. Clean glass substrates were dipped into the solution for 4 times with a speed of dipping of 2 cm per minute. Afterwards, the films deposited were thermally treated at 500 °C to produce the Co3O4 phase. FTIR, UV-Vis and XRD techniques were used to analyze the effects of temperature and pH on reaction carried out on the precursor solution. While the microstructural characterization of thermally treated films was performed through XRD and SEM techniques. In parallel, were studied the thermal decompositions of both Co(CH3COO)2 phase as precursor solution S2 powders using TGA-DTA techniques. The results show that Co3(CH3COO)5OH phase was identified as the precursor to the Co3O4 phase. It was observed that the synthesis temperature promotes the formation reaction of Co(CH3COO)5OH. While the decrease in pH by addition of citric acid had 2 effects. The first was to delay the formation reaction, and the second was to decrease the particle size of phase Co3O4 < 10 nm.

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Objective: Evaluate the physical-chemical properties and characterize the microstructure of four varieties of traditional Mexican chili (Capsicum annuum L.) powders: “Arbol”, “Guajillo”, “Piquin” and “Mole ranchero” (Ancho chili). Design/methodology/approach: Physical-chemical properties of chili powders were evaluated by means of moisture content, particle size, aerated and tapped bulk density, Carr index, Hausner ratio, angle of repose (flow properties), capsaicin, and carotenoids content. Microstructure of samples was characterized by Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. ANOVA analysis and Tukey test were performed to evaluate the significant statistical difference between samples at 95% of confidence level. Results: “Arbol”, “Guajillo”, “Piquin” and “Mole Ranchero” chili powders presented a cohesive behavior respect to its flow properties related to aerated and tapped bulk density, angle of repose, Carr Index, and Hausner ratio values under moisture content between 6.59-14.48 gH2O/100g d.s. “Arbol” and “Piquin” chili powders presented the higher capsaicin content, while “Guajillo” and “Mole ranchero” showed the higher carotenoids content. FTIR spectra confirmed the presence of secondary amide, phenolic groups, alkanes, and aliphatic chains that belong to capsaicin structure at specific absorption bands. Microstructure of chili powders presented particles with surface imperfections as cracks and dents, and smooth surface that influence physical-chemical and flowability properties. Limitations on study/implications: Hight moisture content affect the physical-chemical properties, flowability and microstructure of traditional Mexican chili powders. Findings/conclusions: Moisture content between 6.59 and 14.48 gH2O/100g d.s. influences the physical-chemical properties, flowability and microstructure of traditional Mexican chili powders. To improve physical-chemical properties and flowability behavior of chili powders is required that moisture content be lower than 6.59 H2O/100g d.s.