Stability Efficiencies of POSS and Microalgae Extracts on the Durability of Ethylene-Propylene-Diene Monomer Based Hybrids

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.

Redox Cycling for SOFC Accelerated Degradation

This work aims at development of Accelerated Stress Tests for SOFC via artificial aging of the fuel electrode applying chemical and electrochemical (hydrogen starvation) redox cycling. In principle the degradation processes follows that of calendar aging (Ni coarsening and migration), but in addition it can bring to irreversible damages caused by the development of cracks at the interface anode/electrolyte due to the expansion/shrinkage of the Ni network. The challenge is to introduce conditions which will prevent the formation of cracks which can be done by partial oxidation. The advantage of the proposed methodology is that a mild level of oxidation can be regulated by direct impedance monitoring of the Ni network resistance changes during oxidation/reduction. Once the redox cycling conditions are fixed on bare anode and checked on anode/electrolyte sample for eventual cracks, the procedure can be introduced for AST in full cell configuration. The developed methodology is evaluated by comparative impedance analysis of artificially aged and calendar aged button cells. The results for 20 redox cycles which can be performed for 24 hours are comparable with those obtained for about 1600 hours operation in standard conditions which ensures more than 50 times acceleration.

Studying the causes of destruction of steam superheater tubes in boiler equipment

Results of comprehensive studies of samples of prematurely destroyed 57×4 mm steam superheaer tubes of STBA 22 steel used in a boiler unit of Singburi Sugar Co, Ltd factory (Thailand) are presented. The tubes were manufactured at Interpipe Niko Tube Ltd. (Ukraine) according to JIS G 3462 Standard (Japan). They were destroyed in a short (~240 hrs) term of operation. The cause of premature destruction of tubes of the above steel grade and size assortment in the boiler unit has been established. Based on present-day investigation methods (metallography, X-ray diffraction, etc.), it was found that the tubes were operated with violation of fuel combustion conditions and heat-carrying agent circulation. Characteristic features of operation of damaged tubes include high thermal stresses from the side of the fire-chamber and limitation (or absence) of circulation of the heat-carrying agent (blockage in bends, drum heads, etc.). During operation, the tubes were also exposed to significant thermal vibration stresses (unstable combustion conditions). Prolonged overheating occurred at temperatures above 1000 °C because of violation of circulation of heat-carrying agent and unstable combustion mode. High thermal stresses at almost complete absence of a heat-carrying agent, uneven distribution of growing heat flows caused by violation of the combustion mode in the fire-chamber contributed to accelerated degradation of structure and thermal destruction of the tube metal. In a short term of operation (~240 hours), there was a significant change in the tube size (accelerated high-temperature creep) and complete recrystallization of metal structure throughout the entire wall thickness of the damaged tubes. It has been established that the accelerated degradation of metal microstructure in the destroyed tubes was associated with both overheating of the tube wall and the as-delivered metal structure non-recommended for operation at high temperatures and pressures. It was shown that it is necessary to adjust the heat treatment conditions for these tubes at Interpipe Niko Tube Ltd. The study results have made it possible to develop recommendations for eliminating violations of operating conditions and establishing control of actual heat flows in the most thermally loaded sections of the Singburi Sugar Co. Ltd factory’s steam boiler superheater. Taking into account peculiarities of the boiler equipment and its operating conditions, it was also recommended to use a more heat-resistant and refractory steel instead of the currently used material for manufacture of the steam superheater tubes. Keywords: boiler tube, steam superheater, damage, thermal destruction, structure degradation, combustion conditions, heat carrier circulation, overheating.

Combination of Hyaluronan and Lyophilized Progenitor Cell Derivatives: Stabilization of Functional Hydrogel Products for Therapeutic Management of Tendinous Tissue Disorders

Cultured progenitor cells and derivatives have been used in various homologous applications of cutaneous and musculoskeletal regenerative medicine. Active pharmaceutical ingredients (API) in the form of progenitor cell derivatives such as lysates and lyophilizates were shown to retain function in controlled cellular models of wound repair. On the other hand, hyaluronan-based hydrogels are widely used as functional vehicles in therapeutic products for tendon tissue disorders. The aim of this study was the experimental characterization of formulations containing progenitor tenocyte-derived APIs and hyaluronan, for the assessment of ingredient compatibility and stability in view of eventual therapeutic applications in tendinopathies. Lyophilized APIs were determined to contain relatively low quantities of proteins and growth factors, while being physicochemically stable and possessing significant intrinsic antioxidant properties. Physical and rheological quantifications of the combination formulas were performed after hydrogen peroxide challenge, outlining significantly improved evolutive viscoelasticity values in accelerated degradation settings. Thus, potent effects of physicochemical protection or stability enhancement of hyaluronan by the incorporated APIs were observed. Finally, combination formulas were found to be easily injectable into ex vivo tendon tissues, confirming their compatibility with further translational clinical approaches. Overall, this study provides the technical bases for the development of progenitor tenocyte derivative-based injectable therapeutic products or devices, to potentially be applied in tendinous tissue disorders.

A comprehensive study of current-crowding effect in high power vertical AlInGaN LEDs under high pulsed current

The goal of the study is examination of current-crowding effect in high power AlInGaN LEDs. This effect was presented by mapping of EL (electroluminescence) near filed under high pulse current. LED chip of vertical design was study in high range of current (10−9 ÷ 70A). This operating mode of LEDs are interesting for different applications, such as pumping lasers, VLC and LiFi, as well as for investigation accelerated degradation process of LEDs.