Síntesis y caracterización de monolitos de carbón activado utilizando como precursor cáscara de coco

Diferente series de monolitos de carbón activado fueron preparados por activación química de cáscara de coco con cloruro de zinc a diferentes concentraciones, sin el uso de ningún aglomerante. El paso de conformado por prensado fue introducido entre la impregnación con el agente químico y el tratamiento térmico. Las estructuras fueron caracterizadas por adsorción de N2 a 77 K, microscopia electrónica de barrido (SEM) y algunas series fueron también caracterizadas mediante calorimetría de inmersión en benceno. Los resultados experimentales indicaron que la activación con cloruro de zinc produce una gran desarrollo de microporosidad (volumen demicroporo entre 0,387 cm3g–1-0,79 cm3g–1, área BET entre700 m2g–1-1520 m2g–1), buenas propiedades mecánicas ycaracterísticas superficiales

Caracterización superficial en fase gas y líquida de carbones activados

Se determinó el área superficial de carbones activados obtenidos a partir de cascarilla de café y cáscara de coco, mediante isotermas de adsorción de N2 a 77K. Se compararon los resultados con aquellos obtenidos con un método comúnmente utilizado, el índice de azul de metileno, y se encontró una buena correlación entre las dos áreas determinadas por éste método. Se muestra que los dos métodos permiten realizar un análisis complementario de una superficie porosa

Design and Characterization of a High Resolution Microfluidic Heat Flux Sensor with Thermal Modulation

A complementary metal-oxide semiconductor-compatible process was used in the design and fabrication of a suspended membrane microfluidic heat flux sensor with a thermopile for the purpose of measuring the heat flow rate. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, a low pass filter, and a lock-in amplifier can yield a resolution 20 nW with a sensitivity of 461 V/W. The thermal modulation method is used to eliminate low-frequency noise from the sensor output, and various amounts of fluidic heat were applied to the sensor to investigate its suitability for microfluidic applications. For sensor design and analysis of signal output, a method of modeling and simulating electro-thermal behavior in a microfluidic heat flux sensor with an integrated electronic circuit is presented and validated. The electro-thermal domain model was constructed by using system dynamics, particularly the bond graph. The electro-thermal domain system model in which the thermal and the electrical domains are coupled expresses the heat generation of samples and converts thermal input to electrical output. The proposed electro-thermal domain system model is in good agreement with the measured output voltage response in both the transient and the steady state

Determination of the Temperature Change by Means of an Outcoming Signal of Electric Resistance in an Isoperibolic Calorimetric Cell. Obtainment of Heat Solution

An isoperibolic calorimetric cell is built with glass surrounded by plastic insulation. Thecell has a lid on which a thermistor thermometer, an electric resistance to provide the cell with definitequantities of electric work and a container for a glass ampoule, are placed. For measuring the thermalchanges, an NTC thermistor, which provides an electric resistance signal that varies with temperature,is used. Calibration curves of the thermistor and of the stabilization of the system signal in thermalequilibrium are shown, which enable the observation of a good insulation. The calorific capacity of thesystem with water, with a value of 206.7 ± 0.7 J °C-1 is determined; the solution enthalpy for propanolwaterand KCl-water systems is obtained, which shows the behavior of the cell before exothermic andendothermic effects, respectively

Determination of the temperature change by means of an outcoming signal of electric resistance in an isoperibolic calorimetric cell. Obtainment of heat solution

Abstract: An isoperibolic calorimetric cell is built with glass surrounded by plastic insulation. The cell has a lid on which a thermistor thermometer, an electric resistance to provide the cell with definite quantities of electric work and a container for a glass ampoule, are placed. For measuring the thermal changes, an NTC thermistor, which provides an electric resistance signal that varies with temperature, is used. Calibration curves of the thermistor and of the stabilization of the system signal in thermal equilibrium are shown, which enable the observation of a good insulation. The calorific capacity of the system with water, with a value of 206.7 ± 0.7 J °C-1 is determined; the solution enthalpy for propanolwater and KCl-water systems is obtained, which shows the behavior of the cell before exothermic and endothermic effects, respectively

Thermodynamic and Calorimetric Study of Acetylsalicylic Acid (Aspirin) and Ibuprofen

Enthalpies of solution and dilution of aqueous solutions of sodium acetylsalicylic acid salt and ibuprofen salt were measured with an isoperibolic calorimeter at 293.15 K, 298.15 K, 303.15 K, 308.15 K and 318.15 K. The concentration of the electrolyte was restricted to the solubility of the salt at various temperatures and did not exceed 0.035–0.057 mol kg-1, depending on the temperature studied. The Virial coefficients were derived from Pitzer's model and the excess thermodynamic functions of both the solution and the components of the solution were calculated. An analysis of the thermodynamic characteristics of the solution in terms of concentration and temperature interval was carried out and discussed. Additionally, an analysis was performed by differential scanning calorimetry (DSC)