Effect of bi- and trimodal size distribution on the superficial hardness of Al/SiCp composites prepared by pressureless infiltration

The effect of particle size distribution on the superficial hardness of Al/SiCp composites prepared by pressureless infiltration, as well as on the microhardness and fracture toughness (KIC) of particulate silicon carbide (SiCp) was investigated. Preforms with 0.6 volume fraction of SiC powders (10, 68 and 140 μm) with monomodal, bimodal and trimodal distribution were infiltrated with the alloy Al–15.52 Mg–13.62 Si (wt.%) in argon followed by nitrogen at 1100 °C for 60 min. Results show that density behaves linearly with increase in particle-size-distribution whilst superficial hardness, microhardness and fracture toughness exhibit all a parabolic behavior. Superficial hardness behavior can be explained by the combined effect of work-hardening in the alloy matrix and particle-to-particle impingement. Due to the highly covalent nature of SiC, the parabolic response shown by microhardness and KIC cannot be attributed to a dislocation mechanism as in strain-hardening.The effect of particle size distribution on the superficial hardness of Al/SiCp composites prepared by pressureless infiltration, as well as on the microhardness and fracture toughness (KIC) of particulate silicon carbide (SiCp) was investigated. Preforms with 0.6 volume fraction of SiC powders (10, 68 and 140 μm) with monomodal, bimodal and trimodal distribution were infiltrated with the alloy Al–15.52 Mg–13.62 Si (wt.%) in argon followed by nitrogen at 1100 °C for 60 min. Results show that density behaves linearly with increase in particle-size-distribution whilst superficial hardness, microhardness and fracture toughness exhibit all a parabolic behavior. Superficial hardness behavior can be explained by the combined effect of work-hardening in the alloy matrix and particle-to-particle impingement. Due to the highly covalent nature of SiC, the parabolic response shown by microhardness and KIC cannot be attributed to a dislocation mechanism as in strain-hardening

Microstructure and Mechanical Properties of Al/SiC Composites with Multimodal Size Distribution of Reinforcements

The effect of particle size distribution and particle size ratio of SiC in SiC/SiO2 preforms on the microstructure, microhardness of SiC reinforcements, modulus of rupture and superficial hardness of Al/SiC composites produced by pressureless infiltration has been investigated. SiC/SiO2 preforms in the form of plates (4cm x 3cm x 0.5 cm) have been pressureless infiltrated by the alloy Al-15.52 Mg-13.62 Si (wt%) at 1100°C fro 60 min under inert atmosphere. SiC powders with average particle size of 10, 68 an 140 micras are mixed withy SiO2 powders an preforms of 40% porosity with unimodal, bimodal and trimodal size distribuitions are prepared by uniaxial compactation. The bimodal (small:large) and trimodal (small:medium:large) preforms are prepared with differents particles sizes ratiosin the following levels: 1:1, 3:1.1:3. 2:2:2, 3:2:1, 3:1:2. Results from characterization by XRD, SEM and energy dispersive X-ray spectrometry show that the typical microstructure of the composites contains the MgAl2O4 (spinel), AlN and MgO phases formed during processing as well as particlly reacted silica, SiC, SI and Al. It is found that the density, reinforcements microhardness, modulus of rupture and superficial hardness of the composites increase all with winder particle size distribution. However, whilst the modulus of rupture is mainly affected on going from unimodal and bimodal to trimodal distribution, superficial hardness and microhardness are mostly influenced on going from unimodal to bimmodal adn trimodal distribution

Effect of SiCp multimodal distribution on pitting behavior of Al/SiCp composites prepared by reactive infiltration

The effect of coated-SiCp multimodal-size-distribution on the pitting behavior of Al/SiCp composites was inves- tigated. α-SiC powders (10, 54, 86, and 146 μm) were properly mixed and coated with silica to produce porous preforms with 0.6 volume fraction of the reinforcement with monomodal, bimodal, trimodal, and cuatrimodal size distribution. The preforms were infiltrated with the alloy Al–13 Mg–1.8Si (wt.%) in argon followed by nitrogen at 1100 oC for 60 min. The composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after cyclic polarization measurements in 0.1 M NaCl de-aerated solu- tions. Results show that whereas corrosion and passivation potentials are not influenced with increase in SiCp particle size distribution, favorably, the susceptibility to pitting corrosion decreases. This beneficial effect is ascribed to the smaller area of the alloy matrix exposed to the chloride solution with augment in particle size distribution, substantially when going from monomodal to bimodal SiCp particle size distribution

Microstructure and Mechanical Properties of Al/Sicp Composites with Multimodal Size Distribution of Reinforcements

Abstract. The effect of particle size distribution and particle size ratio of SiCp in SiCp/SiO2 preforms on the microstructure, microhardness of SiCp reinforcements, modulus of rupture, and superficial hardness of Al/SiCp composites produced by pressureless infiltration has been investigated. SiCp/SiO2 preforms in the form of plates (4cm x 3cm x 0.5cm) have been pressureless infiltrated by the alloy Al-15.52 Mg-13.62 Si (wt. %) at 1100 oC for 60 min under inert atmosphere. SiC powders with average particle size of 10, 68 and 140 μm are mixed with SiO2 powders and preforms of 40 % porosity with unimodal, bimodal and trimodal size distributions are prepared by uniaxial compaction. The bimodal (small: large) and trimodal (small: medium: large) preforms are prepared with different particle size ratios in the following levels: 1:1, 3:1, 1:3, 2:2:2, 3:2:1, 3:1:2. Results from characterization by XRD, SEM and energy dispersive X-ray spectrometry show that the typical microstructure of the composites contains the MgAl2O4 (spinel), AlN and MgO phases formed during processing as well as partially reacted silica, SiC, Si and Al. It is found that the density, reinforcement microhardness, modulus of rupture and superficial hardness of the composites increase all with wider particle size distribution. However, whilst the modulus of rupture is mainly affected on going from unimodal and bimodal to trimodal distribution, superficial hardness and microhardness are mostly influenced on going from unimodal to bimodal and trimodal distribution

Effect of Mg Alloying Addition on Dissolution Behavior of Oxide Films in Al-Si-Mg Alloys

Cyclic polarization measurements were carried out for Al-10%Si- X%Mg (X: 3%, 6% and 9.5%) alloys in borate solutions with and without additions of 50 mM NaCl. The voltammetric response exhibited some features of oxide film growth consistent with the high field conduction model. However, higher currents and distortions in the voltammetric wave shape compared to those for pure Al were ascribed to a possible incorporation of alloying elements in the oxide film, rendering it more defective, and to the strong electrochemical activity of Mg2Si particles.Cyclic polarization measurements were carried out for Al-10%Si- X%Mg (X: 3%, 6% and 9.5%) alloys in borate solutions with and without additions of 50 mM NaCl. The voltammetric response exhibited some features of oxide film growth consistent with the high field conduction model. However, higher currents and distortions in the voltammetric wave shape compared to those for pure Al were ascribed to a possible incorporation of alloying elements in the oxide film, rendering it more defective, and to the strong electrochemical activity of Mg2Si particles

Quantifiable isovist and graph-based measures for automatic evaluation of different area types in virtual terrain generation

© 2013 IEEE. This article describes a set of proposed measures for characterizing areas within a virtual terrain in terms of their attributes and their relationships with other areas for incorporating game designers\u27 intent in gameplay requirement-based terrain generation. Examples of such gameplay elements include vantage point, strongholds, chokepoints and hidden areas. Our measures are constructed on characteristics of an isovist, that is, the volume of visible space at a local area and the connectivity of areas within the terrain. The calculation of these measures is detailed, in particular we introduce two new ways to accurately and efficiently calculate the 3D isovist volume. Unlike previous research that has mainly focused on aesthetic-based terrain generation, the proposed measures address a gap in gameplay requirement-based terrain generation-the need for a flexible mechanism to automatically parameterise specified areas and their associated relationships, capturing semantic knowledge relating to high level user intent associated with specific gameplay elements within the virtual terrain. We demonstrate applications of using the measures in an evolutionary process to automatically generate terrains that include specific gameplay elements as defined by a game designer. This is significant as this shows that the measures can characterize different gameplay elements and allow gameplay elements consistent with the designers\u27 intents to be generated and positioned in a virtual terrain without the need to specify low-level details at a model or logic level, hence leading to higher productivity and lower cost

Wireless Network

Tato bakalářská práce se zabývá všeobecnou problematikou bezdrátových sítí. Toto téma zahrnuje informace týkající se základních termínů používaných u Wi-Fi. Dále následuje konkrétní návrh sítě, která nabízí volně přístupnou Wi-Fi síť s možností přístupu na Internet a zároveň zabezpečené propojení nově zavedeného pokladního systému pro restaurace. Při návrhu je přihlíženo na nízký finanční rozpočet a na dostatečné zabezpečení.This bachelor's thesis deals with wireless networks and related issue. It includes an overview of basic terminology commonly connected with Wi-Fi technology. Moreover, it includes a network implementation design, which offers a freely accessible Wi-Fi network with an available Internet connection as well as a secured connection of a newly introduced restaurant till system. The design takes into consideration a limited budget and the need to ensure sufficient security.

Quantifiable isovist and graph-based measures for automatic evaluation of different area types in virtual terrain generation

© 2013 IEEE. This article describes a set of proposed measures for characterizing areas within a virtual terrain in terms of their attributes and their relationships with other areas for incorporating game designers\u27 intent in gameplay requirement-based terrain generation. Examples of such gameplay elements include vantage point, strongholds, chokepoints and hidden areas. Our measures are constructed on characteristics of an isovist, that is, the volume of visible space at a local area and the connectivity of areas within the terrain. The calculation of these measures is detailed, in particular we introduce two new ways to accurately and efficiently calculate the 3D isovist volume. Unlike previous research that has mainly focused on aesthetic-based terrain generation, the proposed measures address a gap in gameplay requirement-based terrain generation-the need for a flexible mechanism to automatically parameterise specified areas and their associated relationships, capturing semantic knowledge relating to high level user intent associated with specific gameplay elements within the virtual terrain. We demonstrate applications of using the measures in an evolutionary process to automatically generate terrains that include specific gameplay elements as defined by a game designer. This is significant as this shows that the measures can characterize different gameplay elements and allow gameplay elements consistent with the designers\u27 intents to be generated and positioned in a virtual terrain without the need to specify low-level details at a model or logic level, hence leading to higher productivity and lower cost

Young’s modulus of Al/SiCP/MgAl2O4 composites with different particle size distribution of reinforcements

The effect of particle size distribution of SiC particulate reinforcements coated with colloidal SiO2 on Young ́s modulus of Al/SiCp/MgAl2O4 composites fabricated by reactive infiltration was investigated. Composites were prepared from porous preforms of silica-coated α- SiC powders of 10, 54, 86, and 146 μm, 0.6 volume fraction of reinforcements and particle size distribution from monomodal to cuatrimodal. Infiltration tests with the alloy Al-13.3Mg-1.8Si (wt. %) were carried out in Ar→N2 atmosphere at 1100oC for 60 min. The composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition to density and residual porosity measurements, Young ́s modulus was evaluated by ultrasonic techniques. Results show that with increase in particles size distribution, residual porosity decreases and density and Young ́s modulus of the composites are improved, the latter from 185.39 ±3.6 to 201.93 ±2.3 GPa. This is attributed to the increased metal-ceramic interfaces and to an enhanced matrix-reinforcement load transmission