In this work, a study of hydroxyapatite (HAp) powders obtained using both, porcine bones and chemical precursors was carried put. In the case of HAp obtained by means of porcine bones, physical processes as cooking, washing and milling were developed, for removing the organic material from the bones; after that, the powders were submitted to a thermal treatment at 800 °C, during 12 h. This procedure was carried out without adding chemical alkalines that are harmful for the environment and the human health. On the other hand, HAp powders were also synthetized using the chemical precipitation method widely reported, showing successful results. Moreover, both kind of powders were characterized using x ray diffraction, Fourier transformer infrared spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. Furthermore, the bioactivity of the materials was determined using the simulated biological fluid (SBF) method. Results showed that the natural HAp exhibited better crystallographic properties. Moreover, according to these results, HAp obtained from porcine bones contains traces of elements as Na and Mg that are favorable for the bioactivity, according to the materials behavior when they are immersed in SBF.

No abstract

This paper presents results of the analysis of organic coffee beans cultivated in Departamento del Cauca -Colombia. Beans studied are of the Coffea Arabica species cultivated in mountain soils of altitude close to 1500 m. Samples from green and roasted beans were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). We intend to relate the features of the heating spectra with the transformation experimented by the coffee. Glass transition and phase transitions were examined. DSC and TGA spectra show that the green coffee experiments a high and fast decomposition after 200°C until 289°C with a remarkable transformation in a close range around 210°C. XRD shows significant changes for green and roasted beans associated to the amount of caffeine hydrates and caffeine anhydrous. Fit of XRD curves by Lorentzian shows a considerable increase of the active crystalline phase at 2θ equal to 20.4 0 for the roasted coffee. The results obtained from this study contribute to the insight associated with the final quality of coffee dependent on roasting methods. Better quality of coffee requires a refined and very controlled roasting process around of 218°C with a slow thermal treatment since the room temperature until the 200°C.

No abstract

No abstract

No abstract

In this work, the production of a novel methodology for the application of natural corrosion inhibitors on steel, using an autoclave is presented. Tests were carried out using Artemisia vulgaris. The inhibitor was produced with a simple soxhlet extraction process using 15 g of Artemisia vulgaris and 260 mL of Ether. Once the inhibitor was produced, the steel was immersed in it, to form a coating that protects the material against corrosion. Thermogravimetry analyzes (TGA) were performed on the inhibitor, to determine the degradation temperature; it was observed that, at 321 °C, the loss of organic mass begins. After applying the inhibitor to the steel, the Fourier Transform Infrared Spectroscopy (FTIR) technique was used to determine the vibrational bands and the difference between the spectra for the steels before and after the coating was applied. For the evaluation of the method efficiency, Electrochemical Impedance Spectroscopy (EIS) and polarization resistance tests were performed, where Nyquist diagrams and Tafel curves were obtained, for steels with and without treatment. In this case, an increase of 93% in the corrosion resistance, and an 88% decrease in the corrosion rate were observed, proving that this methodology can be used to protect steel against corrosion and extend the steel’s useful life.

AuN films were produced on 304 stainless steel using an arc‐pulsed – assisted plasma physical vapor deposition system. The deposition was performed using an Au target in a nitrogen atmosphere at different pressures. The films were characterized using x‐ray photoelectron spectroscopy and x‐ray diffraction. A 398.1‐eV binding energy was observed and assigned to gold nitride species. The x‐ray diffraction patterns displayed a crystallographic structure that corresponded to the Au‐fcc phase with broad diffraction lines. The observed widening of the Bragg diffraction lines (rocking curves) can be attributed to the presence of interstitial nitrogen atoms in the Au‐fcc structure. Copyright © 2015 John Wiley & Sons, Ltd.