Papers by Keyword: Infiltration

Abstract: Dental prostheses made of ceramic composites infiltrated with glasses have been used due to their biocompatibility and possibility to mimic the natural teeth. In this study, the devitrification behavior of 20SiO₂-25B₂O₃-25Al₂O₃-15La₂O₃-15TiO₂ glass during the infiltration process in a porous alumina preform was investigated. Glass frits were prepared by melting the raw materials at 1500 °C for 60 min. The glass was infiltrated into the alumina preform at 1,150 or 1,200 °C for 60 min. The specimens were characterized by X-ray diffraction analysis and scanning electron microscopy. After the infiltration, it was possible to note that the devitrification process occurred in the remaining glass (excess glass that did not infiltrate in the preform), forming mostly aluminum borate and mullite crystalline phases. However, within the infiltrated composite no devitrification was noticed in the infiltrated glass. Possible explanations for this behavior are discussed.

Abstract: Porous biomorphic silicon carbide is a promising ceramic materials for used in wide variety of applications especially in filtration and separation. Wood derived silicon carbide retains the heterogeneous structure of initial wood. Silicon carbide ceramic was derived from Dark Red Meranti wood precursor in this study. The derivation process was prepared by reaction between liquid silicon and carbon preform. The carbon preform was obtained via pyrolysis process at 850 ^°C in Argon gas flow atmosphere. This process was followed by Si infiltration at 1500 ^°C for different holding hours. The density was determined using Archimedes method. SEM was performed to observe their microstructures while the compositions and phase analysis were analysed by EDX and XRD respectively. Thermogravimetric analysis showed that a major weight loss of about 60% of carbon perform due to the decomposition of cellulose and lignin.XRD results revealed the presence of SiC and excess of silicon. It was found that conversion efficiency of carbon into SiC has been improved when the holding time was increased.

Abstract: This study was to examine the effects of ferric oxide contents, which is one of the components of a newly developed glass, on the color and mechanical strengths of zirconia surfaces after glass infiltration. The composition of bioactive glass contained: SiO₂–Al₂O₃–Na₂O–MgO–BaO–CaO–Nb₂O₅–TiO₂–Fe₂O₃. 84 presintered zirconia discs (diameter 15 mm, height 1.2 mm) were prepared. The experimental groups were divided into 6 groups by Fe₂O₃ contents of 0, 1, 1.5, 2.0, 2.5 and 2.9 wt%. Non-glass infiltrated zirconia was used as a control. Bioactive glass was coated on the presintered zirconia disc by a spin coating and infiltrated into zirconia by complete sintering at 1450°C for 2 hr. The color of the specimens was measured using a digital spectrophotometer and biaxial flexural strength and fracture toughness was compared. The colors of glass infiltrated zirconia were from yellow to yellowish orange according to ferric oxides contents and those were within the range of natural teeth colors. The mechanical properties of glass infiltrated zirconia were not inferior to those of zirconia. Glass infiltration with ferric oxide into zirconia can improve the color and mechanical properties of zirconia and be applicable for dental purpose.

Abstract: Today, 3D-printing with polymer plaster composites is a common method in Additive Manufacturing. This technique has proven to be especially suitable for the production of presentation models, due to the low cost of materials and the possibility to produce color-models. But nowadays it requires refinishing through the manual application of a layer of resin. However, the strength of these printed components is very limited, as the applied resin only penetrates a thin edge layer on the surface. This paper develops a new infiltration technique that allows for a significant increase in the strength of the 3D-printed component. For this process, the components are first dehydrated in a controlled two-tier procedure, before they are then penetrated with high-strength resin. The infiltrate used in this process differs significantly from materials traditionally used for infiltration. The result is an almost complete penetration of the components with high-strength infiltrate. As the whole process is computer-integrated, the results are also easier to reproduce, compared to manual infiltration. On the basis of extensive material testing with different testing specimen and testing methods, it can be demonstrated that a significant increase in strength and hardness can be achieved. Finally, this paper also considers the cost and energy consumption of this new infiltration method. As a result of this new technology, the scope of applicability of 3D-printing can be extended to cases that require significantly more strength, like the production of tools for the shaping of metals or used for the molding of plastics. Furthermore, both the process itself and the parameters used are monitored and can be optimized to individual requirements and different fields of application.

Abstract: Hydroxyapatite (HA) is a ceramic material broadly studied due to its great similarity with the human bone. However, this material presents high stiffness and young modulus in comparison with the bone tissue. The polyhydroxybutyrate (PHB) is a themoplatic and biodegradable polymer that presents bone like young modulus and gradative degradation that results in a permanence of the mechanical properties after implantation. The aim of this study is to evaluate the effect of the infiltration of melted PHB on the mechanical properties of porose HA bodies. The composite samples were characterized by SEM, EDS and compressive strength. The samples produced with 10% paraffin and sintered at 1200 °C showed the best mechanical properties and reached an increase of the compressive strength from 29,00 ± 4,70 MPa before infiltration to 83,00 MPa ± 4,41 after infiltration with PHB for a final porosity of 5%.

Abstract: Attempts have been made to describe the influence of copper infiltration on properties of HSS based composites with different iron additions. Iron powder were used to reduce price of composites. The powder compositions used to produce skeletons for further infiltration were M3/2, M3/2 + 7,5%Cu, M3/2+20%Fe and M3/2+50%Fe. The powders were cold pressed at 800 MPa. These as-pressed specimens were used for direct copper infiltration.

Abstract: The paper points at complex methodical approach when assessing noise coming from exterior into residential interior with emphasis on prevention and recommendations of WHO and EC in the phase of designing of building or territory. The ventilation system of the facade of particular building and its functional properties including acoustic and infiltration capability etc. should be designed and controlled upon ensuring complex function of such system and in compliance with the health and hygiene parameters of protected room.

Abstract: Because of evapo-transpiration, compacted loess road embankments were considered to be in a partially saturated state in both arid and semi-arid regions. Based on previous studies and the theory of unsaturated soil mechanics, a numerical analysis of rainfall infiltration in a compacted loess road embankment was conducted. The transient seepage characteristics and moisture migration patterns of the moisture in the embankment were analysed. The results showed that after precipitation, the moisture profile of the compacted loess could be separated into three zones .The data also showed that: under the effect of gravity, the water continued to migrate into the embankment after the rainfall had ended. In time, the saturated zone became partially saturated as the moisture content decreased, whereas the moisture content in the conducting and humid zones increased and the wetting front moved downward. The data also showed that the depth of the conducting and humid zones increased in time, but that the moisture content in the conducting zone increased along a linear gradient with depth, while the moisture content in the humid zone decreased in a similar manner.

Abstract: Runoff and soil loss affect both farmland productivity and environmental quality. This study tested the interaction effects among polyacrylamide (PAM) application rate, PAM molecular weight, and slope gradient on runoff and soil loss under simulated sprinkler irrigation in laboratory. Experimental treatments consisted of four PAM application rates of 0 (control), 0.5, 1.0, and 2.0 g m^-2, two PAM molecular weights of 12 and 18 Mg mol^-1, and three slope gradients of 5^o, 15^o, and 25^o. Results indicated that compared with the control treatment, PAM application generally decreased total runoff volume but increased soil loss. Total runoff volume and soil loss increased with the increased PAM application rate. Under control treatment, total runoff volume increased with the increased slope gradient. However, total runoff volume was similar for different slope gradients when PAM application rates were 0.5 and 1.0 g m^-2, but it decreased with the increased slope gradient when PAM application rate was 2.0 g m^-2. Total soil loss increased with the increase of slope gradient under experimental conditions. Polyacrylamide molecular weight did not affect total runoff volume but did soil loss significantly at P < 0.001, and a high PAM molecular weight resulted in less soil loss than a low one did. Statistical analysis demonstrated that there existed a significant interaction effect at P < 0.001 between PAM application rate and soil slope gradient on runoff volume and soil loss. The interaction effects between PAM molecular weight and slope gradient or among PAM application rate, PAM molecular weight, and slope gradient on soil loss were also significant at P < 0.01. A PAM application rate less than 2 g m^-2 is suggested to control water and soil loss on sloped lands under sprinkler irrigation.

Abstract: Anti-static materials are widely used in the fields of textile, petrochemical processing, aerospace and electronics. An innovative processing method for fabricating anti-static ceramics has been developed based on Fe-infiltration on the sintered zirconia body. The sintered zirconia ceramics infiltrated by metal Fe in the inner atmosphere showed both perfect anti-resistive and mechanical properties. In this study, infiltration temperature and time was optimized to control the surface resistivity. It was shown that the lower surface resistivity could be obtained at higher infiltration temperature and longer infiltration time. However, the surface hardness was decreased. The surface resistivity reached 5.6×10⁷Ω/ at 1300°C for 12 hours. The phase transformation and microstructure changes were characterized by XRD and SEM. The existence state of Fe was analyzed by EDS.