El calor específico (Cp) es un parámetro térmico necesario para la descripción de fenómenos de transporte de calor, relacionado con la adaptación a cambios de temperatura. Por esta razón es importante en la industria de la construcción, de pegantes, de aislantes térmicos y de dispositivos electrónicos. En este trabajo, se utilizó un sistema de relajación térmica para determinar el Cp de láminas de Ti, recubiertas con S-TiO2 por Oxidación Electrolítica con Plasma (OEP). Cada muestra se ubicó dentro de una cámara de vacío que alcanza alrededor de 10-2 Torr y fue calentada por la incidencia de un haz de luz láser de 450 nm de longitud de onda; se ubicó un termómetro infrarrojo (IR) en la parte inferior de la muestra y los datos obtenidos se enviaron a un computador, usando una tarjeta de desarrollo programable. La validación del sistema se hizo comparando los resultados con los reportados por otros autores para zinc, wolframio, titanio y acero. El Cp de las muestras de Ti recubiertas por OEP, que fueron obtenidas usando un electrolito con dos concentraciones de tiourea (CH4N2S) y con tensión aplicada entre los electrodos a 2 kHz con ciclos útiles de 10 %, 20 %, y 30 %, se midió y se comparó con el fin de estudiar la influencia de los parámetros de crecimiento en las características térmicas del material. Los resultados del análisis de varianza de los datos llevaron a encontrar diferencias significativas, con un nivel de confianza del 95 %, relacionadas con la variación en la concentración de CH4N2S. Esto es un indicio del potencial uso de la técnica de relajación térmica para determinar particularidades de este tipo de recubrimientos.

The specific heat at constant pressure (Cp) is a necessary thermal parameter in the description of the heat transport in a material, related to the adaptation to changes of temperature, which is very important in the valuation and inspection of inputs for the construction, adhesives, insulators thermal and electronic devices. In this work, a thermal relaxation system with infrared thermometry was used to determine the Cp of green coffee beans, measuring the temperature of the material placed inside a vacuum chamber that reaches a pressure of 10-2 Torr. The sample was heated by radiation with laser light and the data was obtained by means of an acquisition card. The calibration of the system was made comparing the values obtained of Cp of Zinc, Tungsten, Titanium and Steel sheets with those reported and similarity was found. This method was used to measure the Cp of samples of organic and conventional coffee; these values were subjected to an analysis of variance and significant differences were found with a confidence level of 95 %. This technique could be used for the discrimination of organic coffee in the certification process.

The optical properties of phosphorus-doped hydrogenated amorphous silicon carbide (P-doped a−SixC1−x:H) thin films are studied. Films were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 110 kHz of frequency and pressure of 1.5 Torr, with silane (SiH4) and methane (CH4) as precursor gases. Hydrogen (H2) and phosphine (PH3) were used as diluent and dopant gases, respectively. The impact of the gases flow rate and thermal annealing on the optical properties is evaluated. A concordance is observed between the atomic content of Si, C, and P in films, determined by Energy Dispersive X-ray Spectroscopy, as gases flow rate increases. The composition of the films is established by identifying the vibrational bonding modes using FTIR measurements. Si-H, Si-C, and C-H bonds were identified and their density was obtained. Characterization with UV-Vis spectroscopy shows that the optical band gap (Egopt ), oscillation energy (Eo ), Urbach energy (EU ), and iso-absorption energy (E04 ) increase with the doping level but decrease with the annealing treatment. However, values of dispersion energy (Ed ), dielectric constant (ε) and the refractive index (n) generally become smaller as the phosphorus and carbon content grows, but with a tendency to fall during the annealing. The refractive index by UV-Vis is compared with measurements made with ellipsometry, resulting in a similarity between both techniques. High values of Egopt obtained in P-doped a-SixC1-x:H films can be related to better values of the temperature coefficient of resistance (TCR) for flow sensor applications.