Erosion behavior of EB-PVD 7YSZ coatings under corrosion/erosion regime: Effect of TBC microstructure and the CMAS chemistry

Aero-engines operating in dust-laden environments often encounter a lot of dust/sand that causes a severe problem to the TBCs by means of erosion. As the turbine entry temperatures are rising, molten sand is also a big concern to the life-time of TBCs.This paper deals with the TBC behavior under the combined influence of erosion and corrosion attack. Variations in TBC morphology, CMAS infiltration time and CMAS composition and their influence on the erosion resistance at room temperature were investigated. Two different EB-PVD 7YSZ morphologies consisting of a different porosity arrangement were tested in the erosion/corrosion regime. The more ‘Feathery’ structure has a better resistance to erosion compared to a more columnar ‘Normal’ structure, which leads to less degradation of the TBC. However, under the influence of CMAS infiltration the effect was found to be reversed. In general, CMAS-infiltrated EB-PVD TBCs exhibit a higher erosion resistance than the non-infiltrated ones.     

Adhesive bonding of 3D-printed ABS parts and wood

Additive manufacturing, also known as 3D printing technology, has experienced massive growth in the last decade. Instead of printing the entire product, 3D printing can be used to produce only the most complex parts, which are then combined with simple, non-printed parts from other materials to make the final product. In addition to mechanical connections, adhesive bonding is most commonly used to combine printed parts with other elements. In this study, the influence of 3D-printing parameters on the bond shear strength of 3D-printed Acrylonitrile-butadiene-styrene copolymer parts bonded to beech wood was investigated. Three printing settings with different layer thicknesses (0.39, 0.19, 0.09 mm) and a posttreatment method that utilized acetone vapour were used. The three different adhesives applied were commercial one-component polyurethane adhesive, hot melt adhesive for edge bonding, and a two-component polyurethane adhesive. The results show that the type of adhesive had the biggest influence on the strength of the bond. The highest bond strength was achieved using a two-component polyurethane adhesive. The type of failure (failure in wood, plastic, adhesive, or cohesive failure) depended greatly on the type of adhesive and thickness of the printed layer.     

Microstructural study of aged ferrite powders for sensing layers

Nanosized powders of La_0.80Sr_0.20Fe_0.95Cu_0.05O_3?w were investigated in terms of structural, morphological, chemical and surface properties by using several characterization techniques. The XPS and IR measurements showed the presence of surface hydroxide and carbonates species. After calcination of the powders at 900 °C the amount of carbonates decreased but was still significant. The sensing activity of thick film based on La_0.80Sr_0.20Fe_0.95Cu_0.05O_3?w was tested as a function of relative humidity and the results indicate that (i) after one year of ambient storage the sensing material lost quite completely its sensitivity to humidity, (ii) the sensing activity of the film was mostly re-activated after a thermal treatment at 900 °C for 2 h, and (iii) the huge shift of the detection limit to low RH caused by the presence of 5 mol% Cu is also restored.     

Crystalline Intermediate Phases in the Sol–Gel-Based Synthesis of La2NiO4+δ

X-ray diffraction and transmission electron microscopy were applied to investigate a sol–gel synthetic process for the mixed oxygen ion and electron conductor La₂NiO_4+δ with a K₂NiF₄ structure type. The development of the La₂NiO_4+δ is elucidated considering the influence of calcination temperatures and dwell times. Following the thermal decomposition of nitrate and organic precursors in an intermediate step, the lanthanum nickel oxide is obtained after a short dwell time above 750°C. This occurs by the transformation of an ultrafinely dispersed powder consisting of lanthanum oxycarbonate, lanthanum oxide, and nickel oxide. The pure La₂NiO_4+δ phase was obtained by similar solid-state reactions between nanocrystalline powder particles at just 950°C.     

Deposition of silver ions onto DBD and DCSBD plasma treated nonwoven polypropylene

The aim of this work is plasma activation of nonwoven polypropylene (PP) using two different ambient air plasma sources: volume dielectric barrier discharge (DBD) and diffuse coplanar surface barrier discharge (DCSBD) and its functionalization by silver ion deposition.     

An efficient numerical technique for solving population balance equation involving aggregation, breakage, growth and nucleation

A new discretization for simultaneous aggregation, breakage, growth and nucleation is presented. The new discretization is an extension of the cell average technique developed by the authors [J. Kumar, M. Peglow, G. Warnecke, S. Heinrich, and L. Mörl. Improved accuracy and convergence of discretized population balance for aggregation: The cell average technique. Chemical Engineering Science 61 (2006) 3327-3342.]. It is shown that the cell average scheme enjoys the major advantage of simplicity for solving combined problems over other existing schemes. This is done by a special coupling of the different processes that treats all processes in a similar fashion as it handles the individual process. It is demonstrated that the new coupling makes the technique more useful by being not only more accurate but also computationally less expensive. At first, the coupling is performed for combined aggregation and breakage problems. Furthermore, a new idea that considers the growth process as aggregation of existing particle with new small nuclei is presented. In that way the resulting discretization of the growth process becomes very simple and consistent with first two moments. Additionally, it becomes easy to combine the growth discretization with other processes. The new discretization of pure growth is a little diffusive but it predicts the first two moments exactly without any computational difficulties like appearance of negative values or instability etc. The numerical scheme proposed in this work is consistent only with the first two moments but it can easily be extended to the consistency with any two or more than two moments. Finally, the discretization of pure and coupled problems is tasted on several analytically solvable problems.     

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.

     

Three-dimensional numerical study of heat and mass transfer in fluidized beds with spray nozzle

The numerical computations of temperature and concentration distributions inside a fluidized bed with spray injection in three-dimensions are presented. A continuum model, based on rigorous mass and energy balance equations developed from Nagaiah et al., is used for the three-dimensional simulations. The three-dimensional model equation for nozzle spray is reformulated in comparison to Heinrich. For solving the non-linear partial differential equations with boundary conditions a finite element method is used for space discretization and an implicit Euler method is used for time discretization.The time-dependent behavior of the air humidity, air temperature, degree of wetting, liquid film temperature and particle temperature is presented using two different sets of experimental data. The presented numerical results are validated with the experimental results. Finally, the parallel numerical results are presented using the domain decomposition methods.     

Bone Marrow-Mesenchymal Stromal Cell Secretome as Conditioned Medium Relieves Experimental Skeletal Muscle Damage Induced by Ex Vivo Eccentric Contraction

Bone marrow-mesenchymal stem/stromal cells (MSCs) may offer promise for skeletal muscle repair/regeneration. Growing evidence suggests that the mechanisms underpinning the beneficial effects of such cells in muscle tissue reside in their ability to secrete bioactive molecules (secretome) with multiple actions. Hence, we examined the effects of MSC secretome as conditioned medium (MSC-CM) on ex vivo murine extensor digitorum longus muscle injured by forced eccentric contraction (EC). By combining morphological (light and confocal laser scanning microscopies) and electrophysiological analyses we demonstrated the capability of MSC-CM to attenuate EC-induced tissue structural damages and sarcolemnic functional properties’ modifications. MSC-CM was effective in protecting myofibers from apoptosis, as suggested by a reduced expression of pro-apoptotic markers, cytochrome c and activated caspase-3, along with an increase in the expression of pro-survival AKT factor. Notably, MSC-CM also reduced the EC-induced tissue redistribution and extension of telocytes/CD34⁺ stromal cells, distinctive cells proposed to play a “nursing” role for the muscle resident myogenic satellite cells (SCs), regarded as the main players of regeneration. Moreover, it affected SC functionality likely contributing to replenishment of the SC reservoir. This study provides the necessary groundwork for further investigation of the effects of MSC secretome in the setting of skeletal muscle injury and regenerative medicine.