Improved latent heat storage properties through mesopore enrichment of a zeolitic shape stabilizer

Latent heat storage systems are applied to keep temperature of a local environment within a constant range. The process takes place via release/storage of latent heat during freezing/melting of a corresponding phase change material embedded in a shape stabilizer, which is the scaffold keeping the phase change material stationary in its molten form. In this work, a highly siliceous ZSM-5 and modified versions thereof were chosen as shape stabilizers for molecular and polymeric phase change materials (namely lauric acid and polyethylene glycol), to be impregnated using solvent assisted vacuum impregnation. The dominantly microporous analogues, parent ZSM-5 and its acid-treated derivative, were limited to 40% uptake for each phase change material. Contrastingly, a mesopore rich analogue (as formed under basic conditions) reached 65% impregnation for lauric acid and 70% for polyethylene glycol, without any leakage at 70 \ub0C, resulting in latent heats of 106.9 J/g and 118.6 J/g for each composite, respectively. A simple prototypical real-world application demonstrated that the prepared lauric acid and polyethylene glycol composites of mesopore enriched ZSM-5 could maintain their temperatures up to 27% and 22% lower than the ambient environment under solar heating, as well as up to 20% and 26% higher when solar heating stops. The presented findings indicate mesopore enrichment improves phase change material uptake in these low cost, non-toxic zeolitic shape stabilizers, hence making them good candidates as isolation materials to address energy loss during heating/cooling of household environments

Flexible waterborne polyurethane nanocomposite foams incorporated with halloysites as fresh-keeping packaging inserts for fresh fruits

Food losses due to the deterioration of fresh fruits and related economic problems can be prevented by the use of active food packaging materials. Here, waterborne polyurethane (WPU)/halloysite nanotube (HNT) nanocomposite foams with ethylene and moisture absorption properties are presented, which can be inserted into existing food packages as fresh-keeping packaging materials for the improvement of the shelf life of fruits. WPU with moisture absorption properties has been utilized as a carrier for HNTs, which have a large capacity to absorb ethylene gas, the plant hormone responsible for the ripening of climacteric fruits. HNTs were incorporated into WPUs during a foaming process, resulting in open-cell foams with average pore sizes of 316 µm and a density of 0.136 g/cc. The resulting WPU-HNT foams were shown to absorb moisture by 7 % when they were incubated in a closed container of 100 % relative humidity for 14 days. The WPU-HNT foams were also demonstrated to absorb 2.5 ppm of ethylene gas per gram of foam when kept in a sealed container injected with 90 ppm ethylene gas for 3 days. Tomatoes stored together with the nanocomposite foams in plastic boxes at 4 °C for 14 days presented significantly higher firmness values than the tomatoes stored without the foams. Similarly, bananas stored in polyethylene bags containing the nanocomposite foam remained firmer and free of brown spots for at least 2 days longer than the bananas stored without the nanocomposite foam. The WPU-HNT foams have a strong potential as low-cost, environmentally friendly food packaging inserts that can prevent spoilage of fruits

A new approach in biomimetic synthesis of calcium phosphate coatings using lactic acid-Na lactate buffered body fluid solution

WOS: 000278250100046PubMed ID: 20004750The main objective of this study was to investigate calcium phosphate (CaP) coatings on Ti6Al4V substrates by using the biomimetic technique. To this purpose, a new solution was developed to coat CaP on Ti6Al4V alloy substrates. The newly formulated body fluid (Lac-SBF) contained appropriate amounts of sodium lactate (NaL) and lactic acid (HL), as well as all the other ionic constituents of the human blood plasma. The inorganic ion concentrations of the Lac-SBF solutions were identical with those of human blood plasma. The new Lac-SBF solution of this study eliminated the need for using Tris/HCl or Hepes/NaOH buffers. Prior to coating, Ti6Al4V substrates were chemically treated in NaOH and/or NaOH + H(2)O(2) solutions as an alternative route and then heated at 600 degrees C for 1 h in air. In the previous applications, the Cl(-) ion concentration was found to be higher than blood plasma 103 mM, which exists in human blood plasma as a result of Tris/HCl which are used to prevent precipitation and to keep the pH level at certain values. In this study, instead of using Tris/HCl, HL/NaL which are generated by human body and do not show any toxic behavior, are used and Cl(-) concentration was kept at 103 mM value for the first time. The prepared Lac-SBF was shown to have similar concentration to human blood plasma in terms of all inorganic ions for the first time. Solution properties were evaluated by using turbidimeter, pH meter and rheometer. The coatings were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and a scratch tester. The obtained results are presented and discussed. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.State and Planning Foundation in Ankara, TurkeyTurkiye Cumhuriyeti Kalkinma Bakanligi [06-DPT-002]; EBIL-TEM in Izmir, TurkeyEge UniversityThis work was funded by the State and Planning Foundation in Ankara, Turkey (Project No. 06-DPT-002). The authors thank EBIL-TEM in Izmir, Turkey, because this foundation partially supported our project

Targeting Bacterial Nanocellulose Properties through Tailored Downstream Techniques

Bacterial nanocellulose (BNC) is a biodegradable polysaccharide with unique properties that make it an attractive material for various industrial applications. This study focuses on the strain Komagataeibacter medellinensis ID13488, a strain with the ability to produce high yields of BNC under acidic growth conditions and a promising candidate to use for industrial production of BNC. We conducted a comprehensive investigation into the effects of downstream treatments on the structural and mechanical characteristics of BNC. When compared to alkaline-treated BNC, autoclave-treated BNC exhibited around 78% superior flexibility in average, while it displayed nearly 40% lower stiffness on average. An SEM analysis revealed distinct surface characteristics, indicating differences in cellulose chain compaction. FTIR spectra demonstrated increased hydrogen bonding with prolonged interaction time with alkaline solutions. A thermal analysis showed enhanced thermal stability in alkaline-treated BNC, withstanding temperatures of nearly 300 °C before commencing degradation, compared to autoclaved BNC which starts degradation around 200 °C. These findings provide valuable insights for tailoring BNC properties for specific applications, particularly in industries requiring high purity and specific mechanical characteristics