Comparative Analysis of Reaction to Fire and Flammability of Hemp Shives Insulation Boards with Incorporated Microencapsulated Phase Change Materials

Nowadays buildings contain innovative materials,materials from local resources,production surpluses and rapidly renewable natural resources.Phase Change Materials(PCM)are one such group of novel materials which reduce building energy consumption.With the wider availability of microencapsulated PCM,there is an opportunity to develop a new type of insulating materials,combinate PCM with traditional insulation materials for latent heat energy storage.These materials are typically flammable and are located on the interior wall finishing yet there has been no detailed assessment of their fire performance.In this research work prototypes of low-density insulating boards for indoor spaces from hemp shives using carbamide resin binder and cold pressing were studied.Bench-scale cone calorimeter tests were conducted to evaluate fire risk,with a focus on assessing material flammability properties and the influence of PCM on the results.In this research,the amount of smoke,heat release rate,effective heat of combustion,specific extinction coefficient,mass loss,carbon dioxide yield,specific loss factor,ignition time of hemp straws samples and samples of hemp straws with 10%and without PCM admixture were compared.There is a risk of flammability for PCM and their fire reaction has not been evaluated when incorporating PCM into interior wall finishing boards.The obtained results can be used by designers to balance the potential energy savings of using PCM with a more complete understanding and predictability of the associated fire risk when using the proposed boards.It also allows for appropriate risk mitigation strategies.

Fatty Acid/Expanded Graphite Encapsulating Form-Stable Phase Change Materials for Energy Storage

The lauric-myristic-palmitic acid( LA-MA-PA) ternary eutectic mixtures/expanded graphite( EG) composite phase change materials( PCMs) were prepared by absorbing LA-MA-PA into the porous network of EG. The optimum ratio of ternary eutectic mixtures to EG was determined to be 93∶7 without liquid LA-MA-PA leakage from the composite PCMs. In order to make the structure more stable, the composite PCMs were encapsulated by surface treatment agent to prepare LA-MA-PA/EG encapsulating form-stable PCMs which were characterized by scanning electron microscope( SEM),Fourier transformation infrared spectroscope( FT-IR),differential scanning calorimetry( DSC) and thermal treatment. The results showed there was no chemical reaction between surface treatment agent and LA-MA-PA,and the samples were compactly encapsulated which left almost no imprint on the filter paper after thermal treatment. The phase change temperature and latent heat of LA-MA-PA/EG encapsulating form-stable PCMs were tested to be29. 32 ℃ and 96. 20 J/g,respectively. Additionally,the heat transfer efficiency of heat storage was improved by the addition of EG.

Experimental Investigation of the Operating Characteristics of a Pulsating Heat Pipe with Ultra-Pure Water and Micro Encapsulated Phase Change Material Suspension

The specific heat capacity of working fluid is an important influence factor on heat transfer characteristic of the pulsating heat pipe(PHP).Due to the relatively large specific heat capacity of micro encapsulated phase change material(MEPCM) suspension,a heat transfer performance experimental facility of the PHP was established.The heat transfer characteristic with MEPCM suspension of different mass concentrations(0.5% and 1.0%) and ultra-pure water were compared experimentally.It was found that when the PHP uses MEPCM suspension as its working fluid,operating stability is impoverished under lower heating power and the operating stability is better under higher heating power.At the inclination angle of 90°,the temperature at heating side decreases compared to ultra-pure water and the temperature at heating side decreases with the raising of MEPCM suspension mass concentration.The heat transfer characteristic of the PHP is positively correlated with the inclination angle and the 90° is optimum.The unfavorable effect of the inclination angle decreases with heating power increasing.When the inclination angle is 90°,the PHP with MEPCM suspension at 1.0% of mass concentration has the lowest thermal transfer resistance and followed by ultra-pure water and MEPCM suspension at 0.5% of mass concentration has the highest thermal transfer resistance.When the inclination angles are 60° and30°,the effect of gravity on the flow direction is reduced to 86.6% and 50% of that on the inclination angle of 90°,respectively,and the promoting effect of gravity on the working fluid is further weakened as the inclination angle further decreases.Due to the high viscosity of MEPCM suspension,the PHP with ultra-pure water has the lowest heat transfer resistance.When the inclination angles is 60°,the thermal resistance with MEPCM suspension at0.5% of the mass concentration is lower than that at 1.0% at the heating power below 230 W.The thermal resistance of MEPCM suspension tends to be similar for heating power of 230-250 W.At the heating power above 270 W,the thermal resistance with MEPCM suspension at 1.0% of the mass concentration is lower than that at 0.5%.

Preparation of stimuli-responsive nano-sized capsules based on cyclodextrin polymers with redox or light switching properties

We report the preparation and encapsulation properties of stimuli-responsive nanocapsules, self-assembled by the noncovalent interactions of cyclodextrin- appended polymers （host） and complementary ferrocene or azobenzene carriers （guest）. The encapsulation process was significantly accelerated by applying （electro） chemical or light stimulus, enabling the easier and faster diffusion of guest molecules through the polymer layers. The nanocapsules were characterized by dynamic light scattering, confocal microscopy, ESEM, AFM, W-visible and fluorescence spectroscopy, and electrochemical techniques. The encapsulation and release properties of the nanocapsules were reversible and could be repeated several times, indicating that the prepared nanoassemblies are very stable.

Effects of dielectric stoichiometry on the photoluminescence properties of encapsulated WSe2 monolayers

Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence （at room temperature and 10 K） is assessed on mechanically exfoliated WSe2 monolayer flakes encapsulated with SiOx and AlxOy layers by means of chemical and physical deposition techniques. Conformal coating on untreated and non- functionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion （charged exciton） photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.