Browsing by Subject "Glass ceramics"
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Item Stress analysis in al based composites depending on joining quality(Association for Scientific Research, 2011) Köksal N.S.; Alkan M.It is essential that joints in the design of aluminium based materials be safe and at the desired strength. Specific methods are to be used in welding of these materials. Brazing, that assures joining without changing the material properties, is widely used for this purpose. In this method, quality joining can be achieved, provided the parameters are set up accurately. In this study, joining characteristics of aluminium based composite materials widely used in automotive industry are investigated in detail. Solid models of the parts manufactured by brazing are created using Solidworks software. Hydrostatic loading similar to the real working conditions is applied to these models and stress analysis is performed using ANSYS software. In the samples, joining regions are 2 mm and 2,83 mm in length; and stress distributions are investigated in three groups assuming full, 70% and 50% joining. Stresses arising from loading in the model are below the damage inducing level, but the shape and the length of the joining region are observed to be significant in stress development. © Association for Scientific Research.Item Effect of heat treatment parameters on the crystallization of feldspathic-based dental glass-ceramics(Taylor and Francis Ltd., 2020) Yalamaç E.; Sutcu M.; Ergani E.S.The effects of heat treatment time and temperature on the crystallization of the feldspathic glass-ceramics produced from frit powders were investigated. Two-step heat treatment processes (nucleation and crystal growth) were applied to produce glass-ceramics. In both stages, the samples were heated at different soaking temperatures and times. Tetragonal leucite crystal nucleation and growth processes were followed by XRD, SEM and dilatometer techniques. Depending on first step heat treatment temperature and soaking time the crystallization gradually increases with increasing time and temperature. The second step heat treatment soaking times showed significant change in the coefficient of thermal expansion (CTE) of the glass ceramic samples. Biaxial flexural strength (σ) of the samples slightly increases with increasing the 2nd step soak time and all results are above the required standard value of 100 MPa for the monolithic ceramic for single-unit anterior on dental restorations. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of The Korean Ceramic Society and The Ceramic Society of Japan.Item Recent progress in lanthanide-doped luminescent glasses for solid-state lighting applications - A review(IOP Publishing Ltd, 2021) Erol E.; Vahedigharehchopogh N.; Kibrisli O.; Ersundu M.C.; Ersundu A.E.Nowadays, solid-state white light-emitting diodes (wLEDs) have attracted remarkable attention for applications in general lighting, displays and numerous electronical devices due to their eminent efficiency, longer lifetime and higher mechanical durability compared to traditional incandescent and fluorescent lights. In current commercial wLEDs, a combination of Y3Al5O12:Ce3+ yellow phosphor with blue LED chip and epoxy resin is generally used to generate white light. However, there are some considerable frailties mostly originated from phosphor and resin such as, degradation upon heat, and moisture, inhomogeneous spectral distribution, and poor color rendering capability. Therefore, phosphor embedded glass-ceramics have been developed as a promising way to obtain durable solid-state lighting devices. However, in these methods, there is a greater risk of reactions between the phosphor material and the glass host. At this point, lanthanide-doped luminescent glasses have drawn great attention as a new generation phosphor and/or epoxy free white-light-emitting source owing to their favorable properties including high thermal and chemical stability, high transparency, and easy manufacturing process. This review article aims to comprehensively summarize the recent progress in singly (i.e., Dy3+, Eu2+), doubly (i.e., Dy3+/Eu3+, Dy3+/Tm3+, Dy3+/Ce3+, Ce3+/Sm3+, Ce3+/Tb3+) and triply (i.e., Ce3+/Tb3+/Mn2+, Eu3+/Tb3+/Tm3+, Ce3+/Tb3+/Eu3+, Tm3+/Tb3+/Sm3+, Ce3+/Dy3+/Eu3+, Ho3+/Tm3+/Yb3+, Er3+/Tm3+/Yb3+) lanthanide-doped glasses for solid-state lighting applications through down-shifting and up-conversion emissions. Theoretical background including energy transfer mechanisms, glass synthesis methods, radiative and colorimetric properties are given in details. Finally, various effective strategies are highlighted that minimize the critical challenges associated with lanthanides - such as providing energy transfer from quantum dots or nanoparticles to lanthanides, and doping lanthanides in low phonon energy glass - to improve the white light emission of luminescent glasses and broaden their application areas. © 2021 IOP Publishing Ltd.Item Synthesis and in vitro characterization of superparamagnetic γ-Fe2O3-containing 13–93 bioactive glasses for bone cancer therapy(Elsevier Ltd, 2022) Saatci M.; Deliormanlı A.M.; Atmaca H.Osteosarcoma is one of the most common types of bone cancer, which generally starts in the long bones. In this study, superparamagnetic maghemite-containing (2, 5, 10, 20 wt%) bioactive glass powders were prepared for the treatment of osteosarcoma. For this purpose, maghemite nanoparticles were synthesized using the co-precipitation technique, and maghemite-containing bioactive glass-ceramic composites were fabricated through the sol-gel process. The structural, morphological, thermal, and magnetic properties and the in vitro bioactivity of the prepared bioactive glasses were investigated. In vitro cytotoxicity was examined using SaOS-2 and MC3T3-E1 cells. The fluorouracil (5-FU) release behavior of the studied bioactive glass powders was also monitored in phosphate-buffered saline as a function of time. Results revealed that synthesized maghemite nanoparticles as well as the maghemite-containing bioactive glass-ceramic composites have superparamagnetic properties. They have high bioactivity, with up to 5 wt% maghemite content. Prepared bioactive glass composites have no cytotoxicity against osteosarcoma and pre-osteoblast cells at low concentrations. Drug-loaded bioactive glass powder showed sustained release behavior. Overall results indicated that prepared glass composites have a high potential to be used in magnetic hyperthermia and anticancer drug release applications for the treatment of bone cancer. © 2022 Elsevier Ltd and Techna Group S.r.l.Item Mechanical Properties of Al2024/Al2O3/MgO/Graphite composites via hydro-thermal hot pressing route(Elsevier Ltd, 2023) Ovalı İ.; Esen C.; Albayrak S.; Karakoç H.; Saravana Kumar M.; Yang C.-H.Currently, the research community is focused on hybrid composites with two different reinforcements. However, it's difficult to attain both mechanical strength and wear resistance simultaneously. So, the prime novelty of this research work is to enhance both the mechanical strength and wear performance of the composites by adding three reinforcement particles effectively through the hydro-thermal hot pressing technique. In this research, Al2024 alloy was reinforced with Al2O3–MgO-Gr particles in five different reinforcement combinations. With the help of a 3D mixer, the reinforcements were mixed in determined ratios for 30 min. The mixed powders were cold pressed under 50 MPa pressure, and then hot pressed at 550 °C under 200 MPa pressure. The fabricated hybrid composite materials were evaluated for their density and porosity. Further, hardness, transverse rupture strength and wear performance were investigated. The predominant wear mechanism was examined by wear mechanism maps under various sliding and normal conditions. The outcome shows that the inclusion of excess (>3%) nano MgO and (>1.5%) Gr particles decrease the density of the composite materials by forming micropores. The optimum reinforcement combination of 10% Al2O3, 3% of MgO and 1.5% of Gr particles shows improved cross-fracture strength of 132.6 MPa, minimum volume loss of 0.55 mm3 and decreased frictional coefficient of 0.18. Further, the smoothness in the worn-out surface SEM images of the composites substantiates the enhanced wear performance. © 2023 Elsevier B.V.Item Machine learning approach to predict the mechanical properties of cementitious materials containing carbon nanotubes(Elsevier Ltd, 2024) Okasha N.M.; Mirrashid M.; Naderpour H.; Ciftcioglu A.O.; Meddage D.P.P.; Ezami N.This research explores the use of machine learning to predict the mechanical properties of cementitious materials enhanced with carbon nanotubes (CNTs). Specifically, the study focuses on estimating the elastic modulus and flexural strength of these novel composite materials, with the potential to significantly impact the construction industry. Seven key variables were analyzed including water-to-cement ratio, sand-to-cement ratio, curing age, CNT aspect ratio, CNT content, surfactant-to-CNT ratio, and sonication time. Artificial neural network, support vector regression, and histogram gradient boosting, were used to predict these mechanical properties. Furthermore, a user-friendly formula was extracted from the neural network model. Each model performance was evaluated, revealing the neural network to be the most effective for predicting the elastic modulus. However, the histogram gradient boosting model outperformed all others in predicting flexural strength. These findings highlight the effectiveness of the employed techniques, in accurately predicting the properties of CNT-enhanced cementitious materials. Additionally, extracting formulas from the neural network provides valuable insights into the interplay between input parameters and mechanical properties. © 2024 The Authors