Al2O3-Al2TiO5-TiO2 composites can be obtained by the infiltration of molecular titanium precursors into presintered α-Al2O3 (corundum) cylinders. Two titanium tetraalkoxides, and two dialkoxy titanium bis(acetylacetonates) serve as precursors for TiO2 (rutile) and Al2TiO5 (tialite). The precursors were infiltrated as ethanolic solutions. After sintering at 1550, 1600, and 1650°C, the prepared ceramics’ properties were investigated by SEM, in-situ HT-XRD, and conventional XRD. Titanium tetraisopropoxide leads to the highest content of Al2TiO5 in the composite. The more reactive the precursor, considering the Al2O3/precursor interface, the lower and more anisotropic the grain growth, the more homogeneous is the TiO2 contribution and the higher is the content of Al2TiO5. Raising the sintering temperature causes an increase of the crystalline Al2TiO5 content as well as of the grain growth. Moreover, the reactivity of the precursor molecule influences the Ti/(Al + Ti) ratio in the obtained tialite phase.
Nowadays, aluminum-based composites have been produced by pure alumina (Al2O3) or pure graphene nanoplatelets (GNPs) in aluminum matrix because of the high compressive strength of alumina and the solid lubricant properties of graphene. However, there are no studies on the influence of both alumina and graphene reinforced aluminum composites. In this study, Al-Al2O3 and Al-Al2O3-GNPs composites were reinforced with pure alumina (between 0 and 30 wt.%), pure graphene (0, 0.1, 0.3, 0.5 wt.%), and their hybrid forms (Al2O3-GNPs) by the powder metallurgy method. This method involved ultrasonic dispensing, mixing, filtering, drying, pressing, and sintering processes. From the test results, the micro Vickers hardness of pure aluminum (28.2±1 HV) improved to 51.5±0.8 HV (Al-30Al2O3) and 63.1±1 HV (Al-30Al2O3-0.1GNPs). Similarly, the ultimate compressive strength (UCS) enhanced from 92.4±4 MPa (pure aluminum) to 165±4.5 MPa (Al-30Al2O3) and 188±5 MPa (Al-30Al2O3-0.1GNPs), respectively. In conclusion, the Vickers hardness and ultimate compressive strength of aluminum hybrid composites improved up to 0.1 wt.% graphene content. After 0.1 wt.% graphene content, these mechanical properties decreased because of the clumping of graphene nanoparticles.
Magnetic properties of Fe nanowire arrays (NWs) electrodeposited in anodic alumina membranes have been studied. The influence of nanowire geometry (length, pore diameter) and an external magnetic field applied during electrodeposition process on the magnetic properties of nanowire arrays was investigated. With the use of the X-ray diffraction analysis the structure of iron wires was determined. The iron wires have the regular Body Centered Cubic structure. Magnetic measurements show that shape anisotropy aligns the preferential magnetization axis along the wire axis. It was found that the application of an external magnetic field in a parallel direction to the sample surface induces magnetic anisotropy with an easy axis of magnetization following the nanowire axis. The dependence of the height of Fe wires on the electrodeposition time was determined.
In ceramic forming techniques high particles packing can provide better properties of the final ceramic products. The high quality of the material coupled with the shape complexity of the ceramic product is still challenging. The aim of this work was the optimization and preparation of the ceramic samples based on two alumina powders of different particle size (AA05: 0.5 μm and TM-DAR: 0.15 μm). Firstly, ceramic suspensions of 50vol.% solid loading and the volumetric ratio of AA05 to TM-DAR 1:1, 2:1, 3:1, 4:1, respectively have been prepared. The 2-carboxyethyl acrylate was applied as the new monomer limiting the negative effect of oxygen inhibition. Additionally, the cold isostatic pressing (CIP) was used in order to increase relative density of green bodies. The results of presented research have shown that samples with the ratio of AA05 to TM-DAR 2:1 were characterized by the highest green density (62%). Moreover, CIP process proved to be effective and increased the density of green bodies from 62% to 67%. The pore size distribution of the green bodies has been measured. Samples were sintered at different conditions (1400°C, 1450°C and 1500°C for 1h and 1300°C, 1400°C, 1450°C and 1500°C for 5h).
The subject of the study are alumina foams produced by gelcasting method. The results of micro-computed tomography of the foam samples are used to create the numerical model reconstructing the real structure of the foam skeleton as well as the simplified periodic open-cell structure models. The aim of the paper is to present a new idea of the energy-based assessment of failure strength under uniaxial compression of real alumina foams of various porosity with use of the periodic structure model of the same porosity. Considering two kinds of cellular structures: the periodic one, for instance of fcc type, and the random structure of real alumina foam it is possible to justify the hypothesis, computationally and experimentally, that the same elastic energy density cumulated in the both structures of the same porosity allows to determine the close values of fracture strength under compression. Application of finite element computations for the analysis of deformation and failure processes in real ceramic foams is time consuming. Therefore, the use of simplified periodic cell structure models for the assessment of elastic moduli and failure strength appears very attractive from the point of view of practical applications.
The technique of electrospinning was employed to fabricate uniform one-dimensional inorganic-organic composite nanofibers at room temperature from a solution containing equal volumes of aluminum 2, 4-pentanedionate in acetone and polyvinylpyrrolidone in ethanol. Upon firing and sintering under carefully pre-selected time-temperature profiles (heating rate, temperature and soak time), high-purity and crystalline alumina nanofibers retaining the original morphological features present in the as-spun composite (cermer) fibers were obtained. Tools such as laser Raman spectroscopy, scanning and transmission electron microscopy together with energy dispersive spectroscopy and selected area electron diffraction were employed to follow
the systematic evolution of the ceramic phase and its morphological features in the as-spun and the fired fibers. X-ray diffraction was used to identify the crystalline fate of the final product.
The aim of this work is the development of Cu-Al2O3 composites of copper Cu-ETP matrix composite materials reinforced by 20 and 30
vol.% Al2O3 particles and study of some chosen physical properties. Squeeze casting technique of porous compacts with liquid copper
was applied at the pressure of 110 MPa. Introduction of alumina particles into copper matrix affected on the significant increase of
hardness and in the case of Cu-30 vol. % of alumina particles to 128 HBW. Electrical resistivity was strongly affected by the ceramic
alumina particles and addition of 20 vol. % of particles caused diminishing of electrical conductivity to 20 S/m (34.5% IACS). Thermal
conductivity tests were performed applying two methods and it was ascertained that this parameter strongly depends on the ceramic
particles content, diminishing it to 100 Wm-1K-1 for the composite material containing 30 vol.% of ceramic particles comparing to 400
Wm-1K-1 for the unreinforced copper. Microstructural analysis was carried out using SEM microscopy and indicates that Al2O3 particles
are homogeneously distributed in the copper matrix. EDS analysis shows remains of silicon on the surface of ceramic particles after
binding agent used during preparation of ceramic preforms.
In the last few years, cationic layered clays, including bentonites have been investigated as potential catalysts for SCR DeNOx systems. In this work, bentonite as the representative of layered clays was modified in order to obtain an alternative, low-cost NH3–SCR catalyst. Samples of raw clay were activated with HCl or HNO3, treated with C2H2O4 and subsequently pillared with alumina by the ion- exchange. Afterwards, the modified materials were impregnated with iron and copper. The obtained catalysts were characterized by XRD and FT-IR. SCR catalytic tests carried out over analyzed samples indicated the conversion of NO of approximately 90% for the most active sample. The type of acid used for modification and the type of active phase strongly influenced the catalytic properties of the analyzed materials.
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