Papers by Keyword: Multicomponent

Abstract: The disadvantage of high-strength multicomponent concretes is the high absolute and specific consumption of the binder per unit of strength. The object of research is multicomponent cement systems. The subject is the composition of multicomponent cement systems in order to significantly increase the concentration of the solid phase per unit volume, as well as strength and durability. The creation of a dense, highly filled solid phase in the form of heterogeneous mineral modifiers of a homogeneous dispersed structure ensures the production of high strength concretes with a low binder content. Theoretical and practical studies have shown that there are only three levels of dispersion of mineral modifiers, functionally related to the spatial and geometric parameters of the clinker component and its own pozzolanic activity, providing strength and other construction and technical properties of multicomponent cement systems at the maximum level. The properties and structure of concrete were studied using two fractions of fine aggregate, granite-gabro crushed stone fr. 5-10 mm, Portland cement class CEM I 42.5N, finely dispersed blast-furnace granular slag, microsilica, highly dispersed fraction of cement, superplasticizer Glenium 430 and high-valence hardening accelerator. Research methods: the shape and size of dispersed particles of the components were determined by a laser analyzer, the mobility of the concrete mixture in accordance with GOST 10181–2014, the strength of concrete in accordance with GOST 10180–2012. The structure of the cement stone was studied using scanning microscopy, thermographic and X-ray phase analysis methods. The strength of concrete with an optimized disperse composition, a superplasticizer and a high-valence hardening accelerator at the age of 28 days after hardening under normal conditions was 128; 137; 163 MPa, with the consumption of multicomponent cement, respectively 650, 700, 750 kg / m³.

Abstract: In order to obtain the concentration, temperature and size variations of a bicomponent moving droplet during evaporation process, a mathematic based on multicomponent droplet evaporation model and droplet motion equation was developed to simulate the evaporation characteristic of a binary decane-ethanol droplet at high temperature nitrogen environment. By numerical calculations, the time evolution of internal concentration distribution within droplet was obtained, and the variations of droplet temperature and dimensionless size were analyzed. The numerical results show that: the droplet temperature variation includes transient heating and equilibrium evaporation at atmospheric pressure; while at high pressure environment, the droplet temperature increases gradually till reaches to ambient temperature. The variations of dimensionless droplet size are deviated from the d² law due to the concentration variation during evaporation.

Abstract: Electrospinning of poly(L-lactic acid) (PLLA) and gelatin separately to form nonwoven PLLA or gelatin nanofibrous membranes was investigated. Factors that could affect the fiber morphology and fiber diameter were studies for PLLA and gelatin, respectively. The polymer solution concentration was found to play a dominant role in the formation of defected or nondefected ultrafine fibers. Using a specially designed experimental setup with separate syringe pumps for polymer solutions and separate power supplies for high voltages for electrospinning, PLLA-gelatin bicomponent fibrous membranes were formed with PLLA fibers interweaving with gelatin fibers. Multicomponent fibrous scaffolds can be very useful for tissue engineering and/or controlled release applications.

Abstract: Many Aluminium alloys use the precipitation of metastable phases to generate optimum properties. The effect of including additional structures such as θ’ and GP zones is described in the context of a hierarchy of metastable structures. Extending a Thermodynamic data base that has been designed solely to deal with equilibrium conditions is a vital prerequisite to handling the heattreatment of aluminium alloys. It is then possible to generate TTT and CCT diagrams, using the Johnson-Mehl-Avrami treatment previously applied in to other materials providing provision is made for the presence of supersaturated quenched-in vacancies. Calculations using JMatPro are given for the expected behavior of commercial aluminium alloys of increasing complexity, including AA319, AA6061 and AA7075.

Abstract: Within the frame of the ESA research program SETA, “Solidification along a Eutectic Path in Ternary Alloys”, experiments have been performed focussing on several distinct subtopics. One of these subtopics is to study coupled growth along the univariant eutectic reaction: L → α + β. In this paper, the influence of the growth velocity v on the morphology of the solid/liquid interface is evaluated in a ternary Al-Cu-Si alloy with a composition close to the univariant eutectic groove L → α(Al) + θ-Αl2Cu. Different structural regions can be identified in terms of the stability of the solid-liquid interface (morphological stability) and the stability of the coupling (competitive growth) during unidirectional solidification as function of the solidification parameters. It is found that two-phase planar growth with a lamellar arrangement can be obtained at a sufficiently low growth rate v. The measured interlamellar spacing follows the Jackson and Hunt relationship λ2v = constant. At a higher growth velocity first a destabilisation of the solid/liquid interface is observed and finally competitive growth is observed revealing primary θ-Al2Cu growing ahead of the eutectic interface. It is assumed that the cellular break-up is a two-step process related to the crystallography of the system. Fitting the different morphologies into one microstructure map, an extension of the coupled zone concept as has been proposed for binary alloys is necessary.