Wyniki wyszukiwania - BazTech

1

Frustules of Didymosphenia geminata as a modifier of resins

Zglobicka I., Jablonska J., Suchecki P., Mazurkiewicz-Pawlicka M., Jaroszewicz J., Jastrzebska A., Pakiela Z., Lewandowska M., Swieszkowski W., Witkowski A., Kurzydlowski K. J.

Inżynieria Materiałowa

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2018

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Vol. 39, nr 5

172--177

EN

The paper reports properties of the resin matrix with frustules of diatoms Didymosphenia geminata. The samples of resin containing up to 70% of the volume fraction of the frustules have been prepared in a relatively simple procedure for a commercial resin and using the frustules “harvested” in one of the rivers in Poland by a manual mixing. The compression tests of the samples proved the strengthening effect of the frustules, with the apparent compression modulus increasing by 100% for the volume fraction of 60%. The results of this investigation indicate a high potential of D. geminata frustules in composite technology.

PL

Didymosphenia geminata to słodkowodna okrzemka charakteryzująca się krzemionkowym pancerzykiem i stylikiem wytworzonym z zewnątrzkomórkowego materiału polimerowego. Wymiary pojedynczego pancerzyka D. geminata, wynoszą 80÷140 μm długości i 35÷45 μm szerokości, co sprawia, że jest jedną z większych okrzemek. Zgodnie z trendem stosowania materiałów biologicznych i biomimicznych w pracy przyjęto założenie, że pancerzyki okrzemek mogą być potencjalnie zastosowane jako faza zbrojąca w materiałach kompozytowych o osnowie polimerowej. Jednym z najczęściej stosowanych materiałów na osnowę w kompozytach polimerowych jest żywica epoksydowa. Żywica tego typu jest zbrojona proszkami. Celem niniejszej pracy było zbadanie wykorzystania w tej roli pancerzyków okrzemki Didymosphenia geminata. Podjęte badania polegały na wytworzeniu serii próbek materiałów kompozytowych na osnowie z żywicy epoksydowej z różnym udziałem objętościowym napełniacza. Otrzymane próbki scharakteryzowano pod kątem ich struktury i właściwości mechanicznych.

2

Numerical simulations of epitaxial growth in MOVPE reactor as a tool for aluminum nitride growth optimization

Skibinski J, Caban P., Wejrzanowski T., Grybczuk M., Kurzydlowski K. J.

Journal of Power Technologies

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2016

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Vol. 96, nr 2

110--114

EN

The present study concerns numerical simulations and experimental measurements on the influence of inlet gas mass flow rate on the growth rate of aluminum nitride crystals in Metalorganic Vapor Phase Epitaxy reactor model AIX-200/4RF-S. The aim of this study was to design the optimal process conditions for obtaining the most homogeneous product. Since there are many agents influencing reactions relating to crystal growth such as temperature, pressure, gas composition and reactor geometry, it is difficult to design an optimal process. Variations of process pressure and hydrogen mass flow rates have been considered. Since it is impossible to experimentally determine the exact distribution of heat and mass transfer inside the reactor during crystal growth, detailed 3D modeling has been used to gain insight into the process conditions. Numerical simulations increase the understanding of the epitaxial process by calculating heat and mass transfer distribution during the growth of aluminum nitride crystals. Including chemical reactions in the numerical model enables the growth rate of the substrate to be calculated. The present approach has been applied to optimize homogeneity of AlN film thickness and its growth rate.

3

Design of open-porous materials for high-temperature fuel cells

Wejrzanowski T., Ibrahim H., Cwieka K., Milewski J., Kurzydlowski K. J.

Journal of Power Technologies

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2016

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Vol. 96, nr 3

178--182

EN

Microstructure is one of the major factors influencing material properties. It is especially important for open-porous materials dedicated to catalytic applications, where fraction of pores, their size distribution and specific surface influence the diffusion of reactants and the kinetics of catalytic reactions. In these studies the numerical models of the microstructure of open-porous electrodes for molten carbonate fuel cell (MCFC) are presented. The models presented here simulate fabrication routes for real materials, including mixing of powders, tape casting and sintering processes. The substrate powders are represented by spheres with defined size distribution. Mixing and compaction of powders with polymeric binder is simulated by a granular model implemented in LAMMPS code. In the next step the polymeric phase represented by fine particles and larger porogen addition is removed to form pores. The sintering process is simulated by geometry smoothing, which results in sphere aggregation. The models presented here were compared with micro computed tomography (µCT) 3D images of real MCFC materials. Quantitative analysis of µCT images was performed and it was demonstrated that algorithms used in these studies make it possible to design materials with the desired porous microstructure.

4

Influence of hydrogen volumetric flow rate on temperature distribution in CVD reactor based on epi-growth of SiC

Skibinski J., Wejrzanowski T., Teklinska D., Kurzydlowski K. J.

Journal of Power Technologies

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2015

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Vol. 95, nr 2

119--125

EN

In the present paper the quantitative relationship between the heat and mass transfer in the Aixtron VP508 hot wall CVD reactor and the epitaxial growth of silicon carbide is determined. The aim of this study was to estimate optimal process conditions for obtaining monocrystalline silicon carbide epi-layers with the most homogenous thickness. Since there are many parameters influencing reactions on the crystal area, such as temperature, pressure, gas flow and reactor geometry, it is difficult to design an optimal process. Detailed 3D modeling was used to gain insight into the process conditions, as it is problematic to experimentally determine the exact distribution of heat and mass transfer inside the reactor during epitaxial growth. Numerical simulations allow one to understand the process by calculating the heat and mass transfer distribution during the epitaxial growth of silicon carbide. The present approach was applied to enhance the performance of the Aixtron VP508 reactor.

5

Precipitation strengthening of ultrafine-grained Al-Mg-Si alloy processed by hydrostatic extrusion

Chrominski W., Kulczyk M., Lewandowska M., Kurzydlowski K. J.

Zeszyty Historyczne Politechniki Warszawskiej

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2014

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z. 16

77--84

EN

Precipitation strengthening of an ultrafine-grained Al-Mg-Si alloy has been studied using samples obtained by hydrostatic extrusion. It has been demonstrated that the microstructure after hydrostatic extrusion consists of two types of grains: (1) nano-sized free of dislocations and surrounded with high angle grain boundaries and (2) micron-sized with dislocation substructure. After ageing at 160C, small needle-like precipitates appear in grain interiors of both nano- and micron-sized grains, bringing about a significant strength improvement. However, the precipitates are smaller than those in their coarse grained counterparts. As a consequence, they constitute weaker barriers for dislocations and induce a lower strengthening effect. In addition, one may observe intensive precipitation at nano-grains boundaries, which further reduces the strengthening effect. It was also shown that peak ageing and overageing take place for much shorter time than in the case of coarse grained samples and are caused by the grain growth rather than a change in the precipitation state.

6

Investigation of influence of internal architecture on mechanical properties of 3D printed scaffolds for bone tissue engineering

Ostrowska B., Święszkowski W., Kurzydlowski K.J.

Engineering of Biomaterials

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2012

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Vol. 15, no. 116-117 spec. iss.

8--9

EN

The aim of the study was to investigate the influence of internal architecture of 3D printed scaffolds on their mechanical properties. The polycaprolactone scaffolds with four different geometries produced by rapid prototyping were tested in this study. The 3D samples were manufactured with different internal architecture. The scaffolds were plotted using a 330 ym dispensing needle, layer by layer with lay-down pattern of the fibers: 00/450/900, 0P/60°/120°, 00/900/1800 and 00/600/1200 with shifted layers. Scanning electron mic¬roscopy analyses and mechanical properties examinations were performed. The mechanical test showed that the highest Young's modulus was obtained for the samples with 0P/6CP/12CP lay-down pattern, especially after layers shifting. The SEM analyzes didn't show any defects or layers delamination in the scaffolds. All the samples were characterized by appropriate 3D architecture and good layers connections. The obtained results confirmed the hypothesis that scaffolds with 00/60°/120l0 lay-down pattern of the fibers and with shifted layers have the highest mechanically properties of the investigated samples and therefore, show high potential to be used in bone tissue engineering application.

7

Influence of grain boundaries misorientation angle on intergranular corrosion in 2024-T3 aluminium

Bałkowiec A., Michalski J., Matysiak H., Kurzydlowski K. J.

Materials Science Poland

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2011

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Vol. 29, No. 4

305--311

EN

The special attention has been paid to the influence of misorientation angle of a random grain boundary (GB) on susceptibility to intergranular attack. The detailed observations of the microstructure of the intergranular corrosion (IGC) in 2024-T3 aluminium alloy (AA2024-T3) subjected to galvanic corrosion tests in two different solutions containing chloride ions (0.1 M and 0.5 M NaCl) were carried out using Scanning Electron Microscopy (SEM). The Electron Backscattered Diffraction (EBSD) technique was used to determine the grain boundary character distribution (GBCD) in the initial sample and a GBCD of corroded grain boundaries on a sample subjected to the corrosion test. The results are discussed in terms of the influence of the misorientation angle on the susceptibility of the grain boundaries to corrosion.

8

Quality assessment of expendable patterns in the investment casting process

Matysiak H., Haratym R., Kurzydlowski K. J., Biernacki R.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 1 spec.

247--250

EN

The article presents the basic attempts at expendable patterns quality assessment, such as hardness test, creeping resistance tests and the assessment of patterns mixtures contraction as a function of solidification module. These features were verified on step-shaped pat-terns. Patterns mixtures made on the basis of hard waxes were selected for tests and compared with the domestic mixture based on paraffin and stearin (PS) as well as with the PS-mixture to which the material of used patterns from the WSK Rzeszow factory was added. The selected tests enable a quick assessment of whether the pattern mixture quality meets the requirements of optimum size accuracy and good quality of casting surfaces.

9

Atomic modelling of point defects in B2-RuAl

Sot R., Kurzydlowski K. J.

Materials Science Poland

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2005

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Vol. 23, No. 2

407--411

EN

Ab initio calculations based on density functional theory (DFT) and the pseudopotential method have been used to study B2-structured RuAl. The structural parameters, volume changes of single defects and pressure caused by the presence of point defects in B2-RuAl intermetallic compound were computed by the ab initio pseudopotential method with the plane-wave basis set and a generalized gradient approximation (GGA). The calculated structural parameters are in good agreement with available experimental data.