Fabrication, Composition, Properties and Application of the AlMg1SiCu Aluminium Alloy Matrix Composite Materials Reinforced with Halloysite or Carbon Nanotubes

In this chapter, the characterisation of the halloysite nanotubes (HNTs) and multiwalled carbon nanotubes (MWCNTs) as the reinforcement in the composite materials was described. The original and author technology of production of the aluminium AlMg1SiCu matrix composite materials reinforced with halloysite or carbon nanotubes using powder metallurgy techniques, including mechanical alloying and hot extrusion and the range of own research in the case to determine microstructure, as well as mechanical properties of those materials was present. It was investigated that the addition of carbon and halloysite nanotubes causes a significant improvement in mechanical properties of the obtained nanocomposites. The investigation results show that the technology used in manufacturing nanocomposite materials can find the practical application in the production of new light metal matrix nanocomposites

Effect of Milling Conditions on Microstructure and Properties of AA6061/halloysite Composites

AbstractIn this work, AA6061 matrix composites reinforced with halloysite nanotubes (HNT) were fabricated using respectively, mechanical alloying and uniaxial pressing and hot extrusion. Halloysite, being a clayey mineral of volcanic origin which is characterized by large specific surface, high porosity, high ion exchange and easy mechanical and chemical treatment can be used as alternative reinforcement of metal matrix composite materials. Halloysite nanotubes have recently become the subject of research attention as a new type of reinforcement for improving the mechanical, thermal and fire-retardant performance of polymers. Application of halloysite as the reinforcement in metal matrix composites is the original invention of the authors and it has been patented (PL Patent 216257). The powders morphology, particle size and apparent density of newly developed nanostructural composites were studied as a function of milling time, ball-to-powder ratio and milling speed. Obtained composite powders of aluminium alloy matrix reinforced with 10wt.% of halloysite nanotubes were characterized by SEM analysis. Microstructural observation reveals that mechanical alloying generate a uniform dispersion of nanoparticles in the AA6061 matrix. AA6061 reinforced with 10wt.% HNT composite powder has been fabricated at vial rotation speed of 400rpm within only 6h of ball milling. It has been proven that milling speed and ball-to-powder ratio has a significant effect on the time required to achieve a morphological change in the powder being mechanically alloyed. Moreover, it has been confirmed that the use of mechanical alloying leads to high degree of deformation, which – coupled with a decrease in grain size below 100nm and the dispersion of the reinforcing refined particles – causing increase of composite hardness. Manufacturing conditions allow to achieve an improvement of mechanical properties compared with the base material

Composite Materials Infiltrated by Aluminium Alloys Based on Porous Skeletons from Alumina, Mullite and Titanium Produced by Powder Metallurgy Techniques

The infiltration technology with reinforcement in the form of porous skeletons fabricated with powder metallurgy methods has been presented in relation to the general characteristics of metal alloy matrix composite materials. The results of our own investigations are presented pertaining to four alternative technologies of fabrication of porous, sintered skeletons, and their structure and their key technological properties are presented. Porous skeletons made of Al2O3 aluminium are sintered reactively using blowing agents or are manufactured by ceramic injection moulding (CIM) from powder. Porous skeletons made of 3Al2O3⋅2SiO2 mullite are achieved by sintering a mixture of halloysite nanotubes together with agents forming an open structure of pores. Titanium porous skeletons are achieved by selective laser sintering (SLS). The structure and properties of composite materials with an aluminium alloy matrix—mainly EN AC-AlSi12 and also EN AC-AlSi7Mg0.3 alloys—reinforced with the so manufactured skeletons are also described. A unique structure of the achieved composite materials, together with good mechanical properties and abrasive wear resistance at low density, ensured by an aluminium alloy matrix, are indicating broad application possibilities of such composites

Mitigating Anticipated Effects of Systematic Errors Supports Sister-Group Relationship between Xenacoelomorpha and Ambulacraria

Xenoturbella and the acoelomorph worms (Xenacoe-lomorpha) are simple marine animals with controversial affinities. They have been placed as the sister group of all other bilaterian animals (Nephrozoa hypothesis), implying their simplicity is an ancient characteristic [1, 2]; alternatively, they have been linked to the complex Ambulacraria (echinoderms and hemichordates) in a Glade called the Xenambulacraria [3,5], suggesting their simplicity evolved by reduction from a complex ancestor. The difficulty resolving this problem implies the phylogenetic signal supporting the correct solution is weak and affected by inadequate modeling, creating a misleading non-phylogenetic signal. The idea that the Nephrozoa hypothesis might be an artifact is prompted by the faster molecular evolutionary rate observed within the Acoelomorpha. Unequal rates of evolution are known to result in the systematic artifact of long branch attraction, which would be predicted to result in an attraction between long-branch acoelomorphs and the outgroup, pulling them toward the root [6]. Other biases inadequately accommodated by the models used can also have strong effects, exacerbated in the context of short internal branches and long terminal branches [7]. We have assembled a large and informative dataset to address this problem. Analyses designed to reduce or to emphasize misleading signals show the Nephrozoa hypothesis is supported under conditions expected to exacerbate errors, and the Xenambulacraria hypothesis is preferred in conditions designed to reduce errors. Our reanalyses of two other recently published datasets [1, 2] produce the same result. We conclude that the Xenacoelomorpha are simplified relatives of the Ambulacraria

Cadophora margaritata sp. nov. and other fungi associated with the longhorn beetles Anoplophora glabripennis and Saperda carcharias in Finland

Symbiosis with microbes is crucial for survival and development of wood-inhabiting longhorn beetles (Coleoptera: Cerambycidae). Thus, knowledge of the endemic fungal associates of insects would facilitate risk assessment in cases where a new invasive pest occupies the same ecological niche. However, the diversity of fungi associated with insects remains poorly understood. The aim of this study was to investigate fungi associated with the native large poplar longhorn beetle (Saperda carcharias) and the recently introduced Asian longhorn beetle (Anoplophora glabripennis) infesting hardwood trees in Finland. We studied the cultivable fungal associates obtained from Populus tremula colonised by S. carcharias, and Betula pendula and Salix caprea infested by A. glabripennis, and compared these to the samples collected from intact wood material. This study detected a number of plant pathogenic and saprotrophic fungi, and species with known potential for enzymatic degradation of wood components. Phylogenetic analyses of the most commonly encountered fungi isolated from the longhorn beetles revealed an association with fungi residing in the Cadophora-Mollisia species complex. A commonly encountered fungus was Cadophora spadicis, a recently described fungus associated with wood-decay. In addition, a novel species of Cadophora, for which the name Cadophora margaritata sp. nov. is provided, was isolated from the colonised wood.Peer reviewe

Modelling of hydraulic fracturing process by coupled discrete element and fluid dynamic methods

A three-dimensional model is presented and used to reproduce the laboratory hydraulic fracturing test performed on a thick-walled hollow cylinder limestone sample. This work aims to investigate the implications of the fluid flow on the behaviour of the micro-structure of the rock sample, including the material strength, its elastic constants and the initialisation and propagation of fractures. The replication of the laboratory test conditions has been performed based on the coupled Discrete Element Method (DEM) and Computational Fluid Dynamics scheme. The numerical results are in good agreement with the experimental data, both qualitatively and quantitatively. The developed model closely validates the overall behaviour of the laboratory sample, providing a realistic overview of the cracking propagation towards total collapse as well as complying with Lame’s theory for thick-walled cylinders. This research aims to provide some insight into designing an accurate DEM model of a fracturing rock that can be used to predict its geo-mechanical behaviour during Enhanced Oil Recovery applications

Wpływ czasu mielenia na strukturę i własności proszków kompozytowych AA6061/MWCNTS

The main purpose of this work is to determine the effect of milling time on microstructure as well as technological properties of aluminium matrix nanocomposites reinforced with multi-walled carbon nanotubes (MWCNTs) using powder metallurgy techniques, including mechanical alloying. The main problem of the study is the agglomeration and uneven distribution of carbon nanotubes in the matrix material and interface reactivity also. In order to reach uniform dispersion of carbon nanotubes in aluminium alloy matrix, 5÷20 h of mechanical milling in the planetary mill was used. It was found that the mechanical milling process has a strong influence on the characteristics of powders, by changing the globular morphology of as-received powder during mechanical milling process to flattened one, due to particle plastic deformation followed by cold welding and fracturing of deformed and hardened enough particles, which allows to obtain equiaxial particles again. The obtained composites are characterised by the structure of evenly distributed, disperse reinforcing particles in fine grain matrix of AA6061, facilitate the obtainment of higher values of mechanical properties, compared to the initial alloy. On the basis of micro-hardness, analysis has found that a small addition of carbon nanotubes increases nanocomposite hardness.Głównym celem podejmowanej pracy było określenie wpływu czasu mechanicznego mielenia na strukturę oraz własności technologiczne nanokompozytów o osnowie stopu aluminium 6061 wzmocnionych wielościennymi nanorurkami węglowymi (MWCNTs, ang. multi-walled carbon nanotubes) z wykorzystaniem technik metalurgii proszków, w tym mechanicznej syntezy oraz wyciskania na gorąco. Głównymi problemami podjętymi w badaniach były: aglomeracja i nierównomierny rozkład nanorurek węglowych w osnowie, a także reaktywność na granicy faz. W celu uzyskania jednorodnego rozmieszczenia nanorurek węglowych w osnowie stopu aluminium zastosowano wysokoenergetyczne mechaniczne mielenie w młynie planetarnym przez 5÷20 godzin. Stwierdzono, że zmiana czasu trwania procesu mechanicznej syntezy wpływa znacząco na morfologię materiałów proszkowych, umożliwiając uzyskanie zmiany ich morfologii ze sferycznej – charakterystycznej dla stanu wyjściowego – w odkształconą plastycznie (płatkową), następnie w powtarzających się procesach zgrzewania i pękania materiału umocnionego ponownie przyjmuje postać cząstek równoosiowych. Otrzymane w procesie mechanicznej syntezy materiały kompozytowe charakteryzują się strukturą równomiernie rozłożonych, rozdrobnionych cząstek fazy wzmacniającej, w drobnoziarnistej osnowie stopu AA6061, sprzyjających osiąganiu wyższych wartości własności wytrzymałościowych w porównaniu do stopu wyjściowego. Na podstawie badań mikrotwardości wykazano, że już niewielki dodatek nanorurek węglowych powoduje zwiększenie twardość nanokompozytu