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Silicon nitride (Si3N4) is one of the promising ceramics for dental restoration due to providing significant benefits during the application. This study aimed to investigate the potential use of Si3N4 for all-ceramic dental restorations by characterizing some critical properties as color shade, mechanical resistance, shear-bond strength and radiolucency. For our study, porous Si3N4 ceramic was produced by partial sintering process with limited amounts of sintering additives and low temperature. A commercial ZrO2 ceramic was prepared according to manufacturer’s instructions and results were compared with Si3N4. Si3N4 is an attractive ceramic for dental applications with good mechanical properties even in porous form, it has additional advantages over the conventional ceramics used as restorative material, such as, inherent antibacterial/anti-infective activity, radiolucency, and lower hardness. It is expected that Si3N4 will become popular in dental applications as well. WOS:000640288300023 PMID: 33028788 Q3 Q4

The biocompatibility of silicon nitride ceramics was proven by several studies however this study is apart from the literature in the manner of production routes that are tape casting and partial sintering. We report the tape casting route was chosen and a porous structure was obtained by partial sintering technique. Tape casting brought a smooth surface to the samples. Density and pore size distribution analysis showed that the scaffolds have low density because of the porous structure. XRD and SEM analyses were carried out to reveal the phase and microstructural characteristics of porous ceramic samples. Static contact angle measurement was done for the characterization of the wettability of the scaffolds. It revealed that the surface of the scaffolds was highly hydrophilic which is a desirable characteristic for the protein and cell adhesion. The mechanical characteristics of the scaffolds were analyzed by compression tests. Human osteosarcoma cells were used for in vitro studies. Cell-proliferation and cytotoxicity were analyzed by WST-1 and LDH, respectively. The osteoblastic behavior of the cells on the surface of the scaffolds was identified by alkaline phosphatase activity. BCA analysis was used for total protein content. The BCA and ALP results showed an increasing trend which is directly correlated with cell proliferation. Cells on the surface of the silicon nitride scaffolds were visualized by SEM and fluorescence microscopy where the images supported the in vitro analysis. Therefore, porous silicon nitride scaffolds fabricated via tape casting and partial sintering were biocompatible and they are possible candidates as bone substitute elements.

The corrosion behavior of zircon containing glass-ceramic glazes was studied by examining four different glaze compositions. Glazes with different SiO 2 and ZrO 2 contents were prepared. Chemical resistance of glazed surfaces was tested by immersion of glazes in strong acid solution (HCl-18 vol%). XRD studies of the surfaces before and after immersion did not detect any changes in types and amount of crystalline phases. Zircon was formed as the major phase besides, quartz and anorthite were detected as secondary phases for all samples before and after immersion. Surface examination and SEM-EDX analysis showed that the corrosion mechanism of glazes was directly affected by the composition of the glassy phase. When ZrO 2 dissolved in the glassy phase, the formation of soluble Zr-containing components accelerated the corrosion by the dissolution of the glassy phase and EDX study revealed the compositional change of the glassy phase. When glassy phase did not contain ZrO 2 , corrosion occurred via dissolution of grain boundary phase around the zircon grains instead of dissolution of the glassy phase.

WOS: 000405158100117, The phase and pore evolution of porcelain tiling against sintering temperature are investigated in this study. A standard porcelain tile composition was sintered at nine different temperatures between 1150 and 1230 degrees C. The amount of the amorphous phase and the degree of densification show good compatibility with each other; up to 1200 degrees C they increase gradually, although at this temperature retardation is observed for both properties. Pore size increases up to 1170 degrees C, after which the amorphous phase becomes the major phase of the tile and pore size begins to reduce below 0.4 mu m through the elimination of interconnected porosity. Simultaneous evaluation of scanning electron microscopy (SEM), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) analyses enables us to obtain the sintering behavior of the porcelain tile., Anadolu University Scientific Research Project [080210], Financial support from the Anadolu University Scientific Research Project, Project No. 080210, is gratefully acknowledged.

Calcium orthophosphate (COP) ceramics have been investigated as bone repair materials for many decades. The first in vivo application of these materials was accomplished in 1920 to test tricalcium phosphate performance as a bone substitute. Since this first attempt, various COPs were investigated on animals to shed light on their effect on the healing behavior of bones. Calcium phosphate cements are currently receiving a great deal of interest especially for the hard tissue repair, augmentation, and regeneration applications due to their attractive characteristics such as biocompatibility, ease of shaping, osteoconductivity, and biodegradability.

WOS:000506274000001 Highly porous SiC ceramics containing borax decahydrate were produced by a starch consolidation method in which corn starch was used as a shaping and pore-forming additive. Four different compositions were prepared with different SiC:borax decahydrate ratios and corn starch content. Mixtures with a solid ratio of 55 wt.% were cast in non-porous molds and heated at 80 degrees C for shaping. The starch consolidation technique enabled the shaping of SiC ceramics with different forms and sizes. Simultaneous thermogravimetry and differential thermal analysis of the SiC-borax decahydrate mixture showed that melting took place at below 600 degrees C, as a result of which sintering was carried out at the relatively low temperature, of 600 degrees C in the air using borax decahydrate as a sintering additive. Phase analysis showed that oxidation of SiC did not take place, since no cristobalite phase was detected. Density measurement and mercury porosimetry studies showed that highly porous (70-89% porosity) SiC ceramics with pore size values ranging from 14 to 18 mu m were produced. SEM microstructures of each composition revealed that a strong neck had been formed between the SiC particles in spite of the low sintering temperature. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114M510] This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK Project No: 114M510).

WOS:000578070500001 Si(3)N(4)porous beads were produced from direct carbothermal reduction and nitridation of spheres composed of carbon+SiO(2)mixtures. A simple one-step sol-gel templating technique was used to prepare carbon+SiO2(molar ratio of carbon/SiO(2)was set as 4) containing spheres with a diameter of 2 mm. A natural and abundant biopolymer, alginate, is used as a sacrificial template to produce porous Si(3)N(4)ceramic beads. Carbothermal reduction and nitridation process was conducted at two different temperatures (1500 and 1550 degrees C) and atmospheres (pure nitrogen and 5% hydrogen in nitrogen) to observe the effect of process parameters on the yield of Si3N4. Porous beads with a smooth shape and without any deformation were successfully obtained after the carbothermal reduction and nitridation process. X-ray powder diffraction studies showed that the use of H(2)increased the amount of Si(3)N(4)formed by accelerating the reduction and nitridation reactions. Microstructural investigations revealed oxide addition changed grain morphology from fiber-like to short, angular geometry. This microstructural development showed that the addition of oxide powder increased the amount of liquid phase formed during the heat treatment process and changed carbothermal reduction and nitridation mechanism from vapor-solid to vapor-liquid solid.

Mullit, dusuk isil genlesme, dusuk isil iletkenlik, mukemmel surunme direnci, yuksek sicaklik mukavemeti ve iyi kimyasal kararlilik gibi ozellikleri nedeniyle ileri teknoloji yapisal ve fonksiyonel seramikler icin kullanilan bir malzemedir. Havacilik sektorunde kullanilan metal malzemelerin veya gelecekte kullanim potansiyeli bulunan Si 3 N 4 , SiC gibi seramiklerin mullit esasli seramikler ile kaplanmasina yonelik calismalar yapilmaktadir. Bu calismada, turbin motor bilesenleri icin kaplama malzemesi olarak kullanilabilecek gozenekli mullit seramikler, kismi sinterleme ve gozenek olusturucu ilavesiyle uretilmistir. PMMA (polimetilmetaakrilat) kureleri ve karbamit gozenek olusturucu olarak eklenmis, gozenek tipinin ve buyuklugunun etkileri arastirilmistir. Iki farkli tane boyutunda PMMA ve karbamit olmak uzere uc farkli gozenek olusturucu hacimce % 5 oraninda kullanilmistir. Ortalama tane boyutu PMMA kureleri icin 40 ve 400 µm, karbamit icin ise 1000 µm’dir. Uretilen numunelerin gozenegi % 30-40 arasinda degisirken, gozenek buyuklugu gozenek olusturucu tipine bagli olarak 1-500 µm arasinda olculmustur. Numunelerin elastisite modulu ultrasonik yontemle olculmus, mikroyapisal gelisimi taramali elektron mikroskobu (SEM) ile incelenmis, gozenek buyuklugu ve dagilimi civa porozimetresi ile belirlenmistir.

In this study, Si3N4 foams are successfully produced by a combination of replica and carbothermal reduction and nitridation (CRN) methods. Slurries prepared from C, SiO2 (molar ratio of C:SiO2 was kept to 2.2), bentonite and three types of oxide additives (Y2O3, CeO2 and Yb2O3) are impregnated into polyether sponges. With the addition of bentonite, sufficient green strength is provided and durable foams are produced after the sponge burnout process. Bentonite also enhances the CRN process by increasing the amount of eutectic melt and, hence, a higher amount of beta-Si3N4 is obtained. In addition to bentonite, the yield of beta-Si3N4 is highly dependent on the type of oxide additive. The highest yield is achieved when Y2O3 is used as a result of the formation of a lower viscosity eutectic melt. Vapor-liquid-solid mechanism is favored by the lower viscosity. Foams have beta-Si3N4 as the major phase with minor amounts of alpha-Si3N4 and secondary phases originate from the eutectic melt. The formation and growth mechanisms of beta-Si3N4 are directly affected by the eutectic melt. SiO is deposited in the eutectic melt and super-saturation of beta-Si3N4 grains occur. During the growth of these grains, they contact each other, hindering the formation of typical elongated beta-grains. The final microstructures of the foams consist of hexagonal beta-grains with a low aspect ratio.

•We produce highly porous (up to 66%) Si 3 N 4 .•We enhance the permeability of Si 3 N 4 by using starch as pore former.•Increasing starch amount (?20vol.%) created large and bimodal pore channels and permeability values of these samples are quite higher.•Pore size is more predominant than porosity on permeability. In this study, the possibility of enhancing permeability of porous Si 3 N 4 ceramics was studied by using pore former additive (potato starch; 0-30vol.%). The open porosity of samples changed between 52 and 66% as the mean pore channel size values ranged from 0.9 to 4µm. Increasing starch addition provides bimodal distribution of pore size channels by accompanying abrupt increment in non-Darcian permeability. k 2 value rised from 8.7×10 -10 m to 30.1×10 -10 m

International Workshop on Cellular Materials (I.Wo.C.Mat) -- DEC 15, 2011 -- Turin, ITALY, WOS: 000318325700008, Porous beta-Si3N4 ceramics with two distinct structures were produced by using two different Si3N4 sources to investigate the relationship between microstructure and permeability. Results showed that regardless of pore amount, size of pore channels, shape-distribution of beta-Si3N4 grains are more effective on permeability of porous Si3N4 ceramics. Higher permeability and lower contribution of inertial forces was obtained by microstructure consists of coarse and equiaxed grains even at lower porosity amount. Calculated Forchheimer number (F-o) and measured the local breadth of a pore also supported the effect of microstructure on permeability

WOS: 000324003300014, Thermal properties of AlN-Si-Al composites produced by pressureless melt infiltration of Al/Al alloys into porous alpha-Si3N4 preforms were investigated in a temperature range of 50-300 degrees C. SEM and TEM investigations revealed that the grain size of AlN particles was less than 1 gm. In spite of sub-micron grain size, composites showed relatively high thermal conductivity (TC), 55-107 W/(m.K). The thermal expansion coefficient (CTE) of the composite produced with commercial Al source, which has the highest TC of 107 W/(m.K), was 6.5x10(-6) K-1. Despite the high CTE of Al (23.6x10(-6) K-1), composites revealed significantly low CTE through the formation of Si and AlN phases during the infiltration process., Foundation for Scientific Research Projects of Mugla Sitki Kocman University [10/30]; Scientific & Technological Research Council of Turkey (TUBITAK) [108M194], We are grateful to The Foundation for Scientific Research Projects of Mugla Sitki Kocman University (Project No. 10/30) and The Scientific & Technological Research Council of Turkey (TUBITAK, Project No: 108M194) for funding the present work. We also would like to acknowledge MSc student Serkan Ulukut (Anadolu University) for his help during the TEM sample preparation studies.

International Workshop on Cellular Materials (I.Wo.C.Mat) -- DEC 15, 2011 -- Turin, ITALY, WOS: 000318325700004, In this study, porous beta-Si3N4 ceramics containing limited amount of Sm2O3 and CaO as sintering aids were produced by addition of potato starch (10 and 20 vol.%) and partial sintering. Two different Si3N4 powders, alpha- and beta-, were used as starting materials. Scanning electron microscopy investigations revealed that development of elongated beta-Si3N4 grains were much more pronounced when alpha-Si3N4 starting powder was used. Even though porosity values of the compositions prepared by using alpha-Si3N4 (similar to 57.0-58.4%) is significantly higher than the samples produced by beta-Si3N4 (42.6%), no significant change was observed for the bending strength, fracture toughness and Weibull modulus. This indicates that microstructural features have a significant contribution to the mechanical properties of the porous materials in terms of bending strength and fracture toughness