Wyniki wyszukiwania - Biblioteka Nauki

1

Stabilization of heavy metal particles in Al2O3-W suspensions

100%

Kędzierska-Sar A. , Falkowski P. , Szafran M.

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tom Vol. 61, iss. 3

1465--1470

EN

Ceramic - metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed. Stability of high density metal particles (e.g. W, Mo, Nb) in ceramic-metal composite suspensions is one of crucial issues to be solved in order to obtain homogenous composite material with desired properties such as high fracture toughness, mechanical strength, hardness, wear resistance. In this paper, results of two different methods of stabilizing W particles in Al2O3 - W - H2O system were compared. The zeta potential by laser doppler electrophoresis, stability by static multiple light scattering and rheological behavior of prepared suspensions were analyzed. As a result application of hetero-flocculation effect was consider as a good way to obtain homogeneous dispersion of metal particles with a high density.

2

Manufacturing of ZrO2-Ni graded composites via centrifugal casting in the magnetic field

88%

Wachowski M. , Kosturek R. , Winkler H. , Miazga A. , Lada P. , Kaszuwara W. , Konopka K. , Zygmuntowicz J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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tom Vol. 68, nr 3

539--545

EN

The paper presents the possibility of fabricating ceramic-metal composites by an innovative method of centrifugal slip casting in the magnetic field. It was examined whether the use of this method would allow obtaining a gradient concentration of metal particles in the ceramic matrix. In the applied technique, the horizontal rotation axis was used. The study investigated the effect of solid phase content on the properties and microstructure of the products. Water-based suspensions with 35, 40, 45 and 50 vol.% of solid-phase content were prepared with 10 vol.% additional of nickel powder. The viscosity of prepared slurries was considered. The gradient distribution of nickel particles in the zirconia matrix was observed on SEM. Vickers hardness of ZrO2-Ni composites has been measured. The research revealed that the physical properties depend on the volume fraction of solid content and increase as the volume of solid content increases.

3

Kompozyty ceramiczne jako pełne wykorzystanie zalet ceramiki

75%

Prochoń M. , Biernacka A. , Witczak M.

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2017

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tom nr 1

15--16

4

Machinability analysis of thin-walled carbon fiber reinforced ceramic composites based on wire electrical discharge machining

75%

Poroś D. , Wiśniewska M.

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

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2024

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tom nr 77 (149)

5--13

EN

We propose employing wire electrical discharge machining (WEDM) for shaping thin-walled, multidirectional, carbon fiber reinforced silicon carbide (Cf-SiC) composite parts. Ceramic matrix composite Cf-SiC combines the outstanding mechanical properties of the carbon fiber with oxidation, abrasive wear, corrosion resistance, and high strength at the high temperature of the silicon carbide matrix. The impact of time-related electrical discharge machining parameters (pulse ON-time and break OFF-time) on the material removal rate and surface roughness are analyzed. The material removal rate of the Cf-SiC is proved to be 36% lower than that for machined steel grade 55. The high thermal stresses and interaction of the composite accompanying WEDM are also discussed. Furthermore, an alternative mechanism to the WEDM of metals has been investigated and confirmed by a scanning electron microscopy (SEM) analysis. The morphology of the machined Cf-SiC surface demonstrates the dominance of the carbon fibers’ fracture mechanism, both the transverse and longitudinal forms, with interphase detachment over craters and micro-cracks, pitting, and spalling on the SiC matrix. Satisfactory roughness indicators (Sa = 2 µm) are obtained in 3D topography measurements of the Cf-SiC surfaces. Concluding, the WEDM should be considered a good alternative to Cf-SiC abrasive machining when cutting holes, grooves, keyways, splines, and other complex shapes.

5

Influence of structure on fracture phenomena of materials and testing methods on fracture studies - ceramic materials.

75%

Konopka K.

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tom Vol. 65, nr 11

39-45

EN

In the present paper the process of crack propagation in ceramics and ceramic matrix composites is presented. The ceramic metal and ceramic-polymer composites were analysed. The correlation between the microstructure and the fracture of these materials are discussed. The effect of microstruc-tural defects, and the coefficient of thermal expansion on crack nucleation was described. The examples of crack propagation in ceramics and the influence of metal particles on the path of crack were presented. The role of a spinel phase in ceramic-metal composites on the fracture toughness was disused too. Moreover, the testing method in studies of fracture are described.

PL

Referat dotyczy zjawiska pękania w ceramice i kompozytach o osnowie ceramicznej. Zjawisko inicjacji pękania i dalszej propagacji jest omówione na konkretnych przykładach materiałów ceramicznych w tym kompozytów ceramika-metal i ceramika-polimer. W referacie zostały przedstawione sposoby zwiększania odporności na pękanie oraz metody wyznaczania odporności na pęknie. Na wybranym przykładzie przedstawiono również uwarunkowania metody pomiarowej wpływającej na uzyskany wynik.

6

Manufacturing of ZrO2-Ni graded composites via centrifugal casting in the magnetic field

75%

Wachowski M. , Kosturek R. , Winkler H. , Miazga A. , Lada P. , Kaszuwara W. , Konopka K. , Zygmuntowicz J. , Wachowski M. , Kosturek R. , Winkler H. , Miazga A. , Lada P. , Kaszuwara W. , Konopka K. , Zygmuntowicz J.

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nr 3

7

Modeling of thermal residual stresses in the SiC-TiB2 composite system considering real microstructure and thermo-mechanical properties anisotropy

63%

Grabowski G. , Pędzich Z.

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tom T. 68, nr 2

176--182

EN

The results are presented concerning simulations of the distribution of thermal residual stresses in a ceramic matrix particulate-reinforced composite in the SiC-TiB2 system. The stresses arise during cooling of the material after sintering due to differences in thermal expansion and elastic properties of the component phases, and belong to the most important factors for increasing fracture toughness of ceramic composites. A computational model was built on the basis of the real microstructure of the SiC-TiB2 composite. The material properties of component phases used in calculations included their temperature dependences. A temperature difference caused shrinkage and residual stress was adopted by means of the analysis of the sintering curves. The simulations were performed by using the finite element method. The results of simulations were compared with the calculated values of residual stresses, basing on analytical models and experimental data. The comparison shows good agreement. This allows an elaborated model to be used to solve more complex problems concerning fracture analysis of ceramic matrix composites.

PL

Zaprezentowano wyniki dotyczące symulacji rozkładu cieplnych naprężeń resztkowych w kompozycie dyspersyjnych z osnową ceramiczną z układu SiC-TiB2. Naprężenia powstały podczas studzenia materiału po spieczeniu z powodu różnic w rozszerzalności cieplnej i właściwościach sprężystych składowych, a należą one do najważniejszych czynników odpowiedzialnych za zwiększenie odporności na pękanie kompozytów ceramicznych. Model obliczeniowy został zbudowany na bazie rzeczywistej mikrostruktury kompozytu SiC-TiB2. Właściwości materiałowe składowych faz użyte w obliczeniach uwzględniały ich zależność od temperatury. Różnica temperatury powodująca skurcz i naprężenia resztkowe została uzyskana za pomocą analizy krzywych spiekania. Symulacje przeprowadzono z wykorzystaniem metody elementów skończonych. Otrzymane wyniki porównano z wynikami obliczeń naprężeń resztkowych opartych na modelach analitycznych i danych eksperymentalnych, uzyskując dobrą zgodność, co pozwoliło na opracowanie modelu użytecznego do rozwiązywania bardziej skomplikowanych problemów dotyczących analizy pękania kompozytów z osnową ceramiczną.

8

Fabrication and characterization of composite materials based on porous ceramic preform infiltrated by elastomer

63%

Chabera P. , Boczkowska A. , Witek A. , Oziębło A.

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tom Vol. 63, nr 1

193--199

EN

The paper presents the experimental results of fabrication and characterization of ceramic- elastomer composites. They were obtained using pressure infiltration of porous ceramics by elastomer As a result the composites in which two phases are interpenetrating three-dimensionally and topologically throughout the microstructure were obtained. In order to enhance mechanical properties of preforms a high isostatic pressure method was utilized. The obtained ceramic preforms with porosity gradient within the range of 20-40% as well as composites were characterized by X-ray tomography. The effect of volume fraction of pores on residual porosity of composites was examined. These results are in accordance with SEM images which show the microstructure of composites without any delaminations and voids. Such composites exhibit a high initial strength with the ability to sustain large deformations due to combining the ceramic stiffness and rubbery elasticity of elastomer. Static compression tests for the obtained composites were carried out and the energy dissipated during compression was calculated as the area under the stress-strain curve. The dynamic behavior of the composite was investigated using the split Hopkinson pressure bar technique. It was found that ceramic-elastomer composites effectively dissipate the energy. Moreover, a ballistic test was carried out using armor piercing bullets.