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The reliability of LEDs decreases in moist environments. One potential gateway of moisture ingress, reducing the product lifetime is the lens. In white LEDs, phosphor particles are embedded into the optical silicone of the lens to convert the blue light emitted by the diode down in frequency and achieve a light output that appears white. In this study, the influence of these phosphor particles on the moisture sorption, permeation and diffusion in optical silicones is investigated by comparing two silicone resins that are commonly used in LEDs, both with and without the addition of phosphor particles. The results of two methods are compared: the wet-cup method and a gravimetric approach of dynamic vapour sorption (DVS). Diffusion coefficients between 20 and 75 °C are reported as well as sorption isotherms, activation energy and sorption enthalpy. It is concluded that the addition of phosphor particles only has a very small impact on the moisture transport properties of the silicones., Electronic Components, Technology and Materials, (OLD) MSE-6

The reliability of LEDs decreases in moist environments. One potential gateway of moisture ingress, reducing the product lifetime is the lens. In white LEDs, phosphor particles are embedded into the optical silicone of the lens to convert the blue light emitted by the diode down in frequency and achieve a light output that appears white. In this study, the influence of these phosphor particles on the moisture sorption, permeation and diffusion in optical silicones is investigated by comparing two silicone resins that are commonly used in LEDs, both with and without the addition of phosphor particles. The results of two methods are compared: the wet-cup method and a gravimetric approach of dynamic vapour sorption (DVS). Diffusion coefficients between 20 and 75 °C are reported as well as sorption isotherms, activation energy and sorption enthalpy. It is concluded that the addition of phosphor particles only has a very small impact on the moisture transport properties of the silicones., Electronic Components, Technology and Materials, (OLD) MSE-6

According to the European Commission, in 2016 the residential sector represented 25.4% of the final energy consumption. Heating and cooling in EU households account for 69.1% of the total energy consumption. The fraction of 84% for heating and cooling is still generated from fossil fuels, and only 16% is generated from renewable energy. To decrease carbon dioxide emissions of fossil fuel consumption, it is crucial to find alternatives to supply the heating and cooling demand. Alternatives such as adsorption-based heat pumps and desiccant cooling systems are receiving much attention because of their moderate energy consumption. These systems are based on the energetic exchange during the adsorption/desorption of working fluids. In this work, we combined experiments and simulations to evaluate the viability of several zeolites and MOFs with water for cooling systems applications. We combined the study of adsorption mechanisms and the dynamics of water inside the pores of the structures, thereby obtaining an overall understanding of the working pair. We found that the Al content in FAU-topology zeolites is a key factor for an efficient process. We also identify ZJNU-30 metal–organic framework as a suitable candidate for cooling applications because of its outstanding water capacity, cooling capacity, and coefficient of performance., Accepted Author Manuscript, Engineering Thermodynamics

According to the European Commission, in 2016 the residential sector represented 25.4% of the final energy consumption. Heating and cooling in EU households account for 69.1% of the total energy consumption. The fraction of 84% for heating and cooling is still generated from fossil fuels, and only 16% is generated from renewable energy. To decrease carbon dioxide emissions of fossil fuel consumption, it is crucial to find alternatives to supply the heating and cooling demand. Alternatives such as adsorption-based heat pumps and desiccant cooling systems are receiving much attention because of their moderate energy consumption. These systems are based on the energetic exchange during the adsorption/desorption of working fluids. In this work, we combined experiments and simulations to evaluate the viability of several zeolites and MOFs with water for cooling systems applications. We combined the study of adsorption mechanisms and the dynamics of water inside the pores of the structures, thereby obtaining an overall understanding of the working pair. We found that the Al content in FAU-topology zeolites is a key factor for an efficient process. We also identify ZJNU-30 metal–organic framework as a suitable candidate for cooling applications because of its outstanding water capacity, cooling capacity, and coefficient of performance., Accepted Author Manuscript, Engineering Thermodynamics

Architecture

Architecture

The coupled mass transfer and chemical reactions of a gel-forming compound in a two-phase system were studied in detail. Tetra-methyl-ortho-silicate (TMOS) is often used as a precursor in sol-gel chemistry to produce silica gels in aqueous systems. TMOS can also be mixed with many hydrocarbons without chemical reaction, which allows for various applications in multiphase systems. In this study, TMOS was mixed with n-hexadecane and placed together with water in small cylinders. Upon contact of the mixture with the water, TMOS transfers completely to the aqueous phase where it forms a gel through a heterogeneous reaction. Nuclear magnetic resonance imaging and relaxation time measurements were employed to monitor the mass transfer of TMOS from the oleic to the aqueous phase. The longitudinal relaxation time (T1) was calibrated and used to determine the concentration of TMOS in n-hexadecane during the transfer. The mass transfer rate was obtained at various temperatures (25–45?°C) and for several initial concentrations of TMOS. In the aqueous phase a sharp decrease in the transversal relaxation time (T2) is observed which is attributed to the gel reaction, in particular the formation of methanol in the initial stage. The minimum in T2 indicates the gelation point, and was found to be strongly dependent on temperature and concentration., Geotechnology, Civil Engineering and Geosciences

Architecture

The coupled mass transfer and chemical reactions of a gel-forming compound in a two-phase system were studied in detail. Tetra-methyl-ortho-silicate (TMOS) is often used as a precursor in sol-gel chemistry to produce silica gels in aqueous systems. TMOS can also be mixed with many hydrocarbons without chemical reaction, which allows for various applications in multiphase systems. In this study, TMOS was mixed with n-hexadecane and placed together with water in small cylinders. Upon contact of the mixture with the water, TMOS transfers completely to the aqueous phase where it forms a gel through a heterogeneous reaction. Nuclear magnetic resonance imaging and relaxation time measurements were employed to monitor the mass transfer of TMOS from the oleic to the aqueous phase. The longitudinal relaxation time (T1) was calibrated and used to determine the concentration of TMOS in n-hexadecane during the transfer. The mass transfer rate was obtained at various temperatures (25–45?°C) and for several initial concentrations of TMOS. In the aqueous phase a sharp decrease in the transversal relaxation time (T2) is observed which is attributed to the gel reaction, in particular the formation of methanol in the initial stage. The minimum in T2 indicates the gelation point, and was found to be strongly dependent on temperature and concentration., Geotechnology, Civil Engineering and Geosciences

Architecture