Effect of Diluents on Post-Reaction Sintering of Silicon Nitride Ceramics

2007 ◽  
Vol 352 ◽  
pp. 185-188 ◽  
Author(s):  
Toru Wakihara ◽  
Masahiro Yabuki ◽  
Junichi Tatami ◽  
Katsutoshi Komeya ◽  
Takeshi Meguro ◽  
...  
Keyword(s):  
Bending Strength ◽  
Exothermic Reaction ◽  
High Strength ◽  
Cost Effective ◽  
Raw Material ◽  
Reaction Sintering ◽  
Oxygen Donor ◽  
Nitride Ceramics ◽  
Si3n4 Ceramics

Post-reaction sintering as a technique for the fabrication of Si3N4 ceramics has received much attention as a cost-effective process due to the use of cheap Si powder as a raw material. In this method, the rapid exothermic nitridation of Si results in local melting of Si to cause its agglomeration, which is expected to be a flaw after densification. Therefore, control of the exothermic reaction is needed to improve the reliability of post-reaction sintered Si3N4 ceramics. In this study, Si3N4 ceramics were fabricated by post-reaction sintering with Si3N4 or SiO2 powders in order to control the exothermic reaction. As a result, the microstructure and bending strength of Si3N4 ceramics was changed by adding these additives. In particular, the addition of SiO2 resulted in the high strength of Si3N4 ceramics. Consequently, it was found that Si3N4 and SiO2 particles played the role of diluents, and SiO2 was effective in post-reaction sintering as an oxygen donor.

Sintering Shrinkage Behavior of Si3N4 Ceramics Prepared by a Post-Reaction Sintering Technique

2008 ◽  
Vol 403 ◽  
pp. 31-34
Author(s):  
Hiromasa Yabuki ◽  
Toru Wakihara ◽  
Junichi Tatami ◽  
Katsutoshi Komeya ◽  
Takeshi Meguro ◽  
...  
Keyword(s):  
Cost Effective ◽  
Raw Material ◽  
Reaction Sintering ◽  
Green Body ◽  
Shrinkage Temperature ◽  
Neck Growth ◽  
Si3n4 Powder ◽  
Sintering Shrinkage ◽  
Si3n4 Ceramics ◽  
Shrinkage Behavior

Post-reaction sintering is one of the fabrication processes of Si3N4 ceramics, which has received considerable attention as a cost-effective process due to the use inexpensive Si powder as a raw material. So far, many researches on the development of this method have been performed in order to improve their properties; however, the sintering shrinkage behavior, which is valuable for the optimization of the firing conditions, has not been well clarified. In this study, we focus on the post-reaction sintering of the Si-Y2O3-Al2O3 system, and investigate its sintering shrinkage behavior by dilatometery. It was found that there is no shrinkage from 1400 to 1600 °C due to grain rearrangements in the green body of the reaction-bonded Si3N4. Furthermore, the shrinkage of the reaction-bonded Si3N4 commenced at approximately 1750 °C, which is higher than the shrinkage temperature of the green body of conventional Si3N4 powder. The restriction of the shrinkage appears to result from the neck growth and strong aggregation among the reacted Si3N4 particles.

Preparation and Characterization of Reaction Sintering B4C/SiC Composite Ceramic

2014 ◽  
Vol 602-603 ◽  
pp. 536-539
Author(s):  
Hai Bin Sun ◽  
Yu Jun Zhang ◽  
Qi Song Li
Keyword(s):  
Fracture Toughness ◽  
High Performance ◽  
Bending Strength ◽  
Carbon Sources ◽  
High Hardness ◽  
High Strength ◽  
Composite Ceramic ◽  
High Fracture Toughness ◽  
Reaction Sintering ◽  
High Fracture

High hardness, high strength, high fracture toughness and low density are required for novel bulletproof materials. B4C/SiC composite ceramic is one of the most potential candidates. In this study, B4C/SiC composite ceramic was prepared by reaction sintering. The influence of B4C content, species and content of carbon, sintering temperature on the mechanical properties of B4C/SiC composite ceramic were studied. A high performance B4C/SiC composite ceramic was sintered at 1750°C for 30 min. Phenolic resin and carbon black were both chosen as carbon sources, whose favorable contents were 10wt%, 5wt%, respectively. The density of sintered bodies reduces with B4C content increases. To some extent, fracture toughness, bending strength improve initially and then deteriorate with the increase of B4C content whose optimal amount is 30wt%. The optimal fracture toughness and bending strength of the B4C/SiC composite ceramic are 5.07MPa·m1/2 and 487MPa, respectively. Meanwhile, the Viker-hardness of the sintered body is 30.2GPa, the density is as low as 2.82g/cm3.

scholarly journals Role of syntrophic microbial communities in high-rate methanogenic bioreactors

2012 ◽  
Vol 66 (2) ◽  
pp. 352-362 ◽  
Author(s):  
Alfons J. M. Stams ◽  
Diana Z. Sousa ◽  
Robbert Kleerebezem ◽  
Caroline M. Plugge
Keyword(s):  
Fatty Acid ◽  
Industrial Wastewater ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
High Strength ◽  
Cost Effective ◽  
Anaerobic Treatment ◽  
High Rate ◽  
Degrading Bacteria

Anaerobic purification is a cost-effective way to treat high strength industrial wastewater. Through anaerobic treatment of wastewaters energy is conserved as methane, and less sludge is produced. For high-rate methanogenesis compact syntrophic communities of fatty acid-degrading bacteria and methanogenic archaea are essential. Here, we describe the microbiology of syntrophic communities in methanogenic reactor sludges and provide information on which microbiological factors are essential to obtain high volumetric methane production rates. Fatty-acid degrading bacteria have been isolated from bioreactor sludges, but also from other sources such as freshwater sediments. Despite the important role that fatty acid-degrading bacteria play in high-rate methanogenic bioreactors, their relative numbers are generally low. This finding indicates that the microbial community composition can be further optimized to achieve even higher rates.

scholarly journals Evaluation of Kalalani vermiculite for production of high strength porcelain insulators

2019 ◽  
Vol 51 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Blasius Ngayakamo ◽  
Eugene Park
Keyword(s):  
Water Absorption ◽  
Bulk Density ◽  
Bending Strength ◽  
Raw Materials ◽  
High Strength ◽  
Microstructural Characterization ◽  
Dielectric Strength ◽  
Raw Material ◽  
Porcelain Insulators

The present work has evaluated Kalalani vermiculite as a potential raw material for the production of high strength porcelain insulators. Three porcelain compositions were prepared to contain 0, 20 and 30 wt% of Kalalani vermiculite. Porcelain samples were fabricated using a semi-drying method. The chemical, mineralogical phases and microstructural characterization of the raw materials were carried out using XRF, XRD, and SEM techniques, respectively. Water absorption, bulk density, dielectric and bending strengths were performed on porcelain samples fired up to 1300?C. However, at the sintering temperature of 1250?C, the porcelain sample with 20 wt% of Kalalani vermiculite gave the dielectric strength of 61.3 kV/mm, bending strength of 30.54 MPa, bulk density of 2.21 g/cm3 and low water absorption value of 0.21 % which is the prerequisite properties for high strength porcelain insulators. It was therefore concluded that Kalalani vermiculite has the potential to be used for the production of high strength porcelain insulators

scholarly journals PROCESSING POSSIBILITIES OF BIRCH OUTER BARK INTO GREEN BIO-COMPOSITES

2017 ◽  
Vol 3 ◽  
pp. 249 ◽  
Author(s):  
Aigars Paze ◽  
Janis Rizhikovs ◽  
Prans Brazdausks ◽  
Maris Puke ◽  
Juris Grinins ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Cost Effective ◽  
Acid Number ◽  
Raw Material ◽  
Birch Bark ◽  
Outer Bark ◽  
Epoxy Acids ◽  
Binder Ratio ◽  
A Minor

The main objective of the study was to obtain bio-composites from grey alder sawdust using a mixture of birch outer bark suberinic acids as a binder, and to test their mechanical properties. Ethanol-extracted birch outer bark was used as a raw material for the investigation. Characteristics (suberinic acids content, epoxy acids content and acid number) of the hydrolytically depolymerized birch outer bark binder were also determined. The initial filler/binder ratio and molding parameters (temperature and pressure) were established by the full factorial design. Preliminary data showed that the increase of the pressing temperature from 160 to 200 °C at a pressure of 3.5 MPa resulted in a minor growth of the boards’ density (up to 1.0 g/cm3) and bending strength (up to 17.1 MPa). Our investigation has shown that it is possible to use one of the plywood production residues – outer birch bark – as a raw material for obtaining particleboards, which have mechanical properties beyond the standard limits. The used method is also environmentally friendly, easy realizable in practice and has a potential to be cost-effective.

Preparation and Mechanism of Cordierite by Using Calcined Bauxite as Raw Material at Relatively Low Temperature

2013 ◽  
Vol 785-786 ◽  
pp. 1066-1071
Author(s):  
Jian Feng Wu ◽  
Bin Zheng Fang ◽  
Xiao Hong Xu ◽  
Xin Bin Lao
Keyword(s):  
Low Temperature ◽  
Bulk Density ◽  
Bending Strength ◽  
Raw Materials ◽  
Xrd Analysis ◽  
Raw Material ◽  
Synthetic Process ◽  
Synthetic Temperature ◽  
Sintering Method

The cordierite was synthesized at relatively low temperature by pressureless sintering method, using calcined bauxite, talcum , quartz and feldspar as raw materials in this paper. The water absorption (Wa), porosity (Pa), bulk density (Db) and bending strength of samples have been tested, and the synthetic process and mechanism have been investigated by XRD, SEM, and so on. The results showed that the cordierite could be synthesized at 1280°C and the range of synthetic temperature is 1160~1300°C, when the sample was sintered at 1280°C for 2h, its bulk density and bending strength were 2.20g/cm3and 72.13MPa, respectively. XRD analysis showed that the main phase of sample was cordierite, the cordierite content was about 88wt%, and the minor phases were MgAl2O4spinel and corundum. SEM results showed that the samples were dense and the pore sizes were 5 μm~100μm, the grains were growth and development well, the grains size were 0.5μm~6μm. High reaction activity corundum and mullite were provided by calcined bauxite, then coupled with the role of feldspar, thus reduced the synthetic temperature of cordierite.

Research the Performance of Alumina Insulation Material by Freeze-Drying

2012 ◽  
Vol 512-515 ◽  
pp. 527-530
Author(s):  
Dao Yuan Yang ◽  
Guang Hui Wei
Keyword(s):  
Freeze Drying ◽  
Bending Strength ◽  
High Strength ◽  
Raw Material ◽  
Insulation Material ◽  
Direct Foaming ◽  
Gel Casting ◽  
Alumina Particles ◽  
Additive Combination ◽  
Ice Sublimation

The traditional method of preparation alumina insulation material includes the addition of pore-forming agent, direct foaming, foam impregnation and gel-casting. In this experiment, α-alumina as raw material, silica fume as an additive, Combination freeze-drying method, add pore-forming agent and direct foaming successfully prepared low-density, high strength, low thermal conductivity of alumina insulation material. Change the particle size of pore-forming agent can be get different properties of the sample. The SEM photograph was clearly observed that the hole wall dense uniform, α-alumina particles sufficient contact, no significant ice sublimation hole left. There are also the reasons of the sample with higher value of bending strength and compressive strength. This can make a control of porosity, as well as pore size, pore shape and pores space topology of alumina insulation material.

scholarly journals Twist and lock: nutshell structures for high strength and energy absorption

2021 ◽  
Vol 8 (8) ◽  
pp. 210399
Author(s):  
Nannan Xiao ◽  
Martin Felhofer ◽  
Sebastian J. Antreich ◽  
Jessica C. Huss ◽  
Konrad Mayer ◽  
...  
Keyword(s):  
Energy Absorption ◽  
Imaging Techniques ◽  
High Strength ◽  
High Energy ◽  
Raw Material ◽  
Pistachio Shell ◽  
Composition And Structure ◽  
Depth Study ◽  
High Energy Absorption

Nutshells achieve remarkable properties by optimizing structure and chemistry at different hierarchical levels. Probing nutshells from the cellular down to the nano- and molecular level by microchemical and nanomechanical imaging techniques reveals insights into nature's packing concepts. In walnut and pistachio shells, carbohydrate and lignin polymers assemble to form thick-walled puzzle cells, which interlock three-dimensionally and show high tissue strength. Pistachio additionally achieves high-energy absorption by numerous lobes interconnected via ball-joint-like structures. By contrast, the three times more lignified walnut shells show brittle LEGO-brick failure, often along the numerous pit channels. In both species, cell walls (CWs) show distinct lamellar structures. These lamellae involve a helicoidal arrangement of cellulose macrofibrils as a recurring motif. Between the two nutshell species, these lamellae show differences in thickness and pitch angle, which can explain the different mechanical properties on the nanolevel. Our in-depth study of the two nutshell tissues highlights the role of cell form and their interlocking as well as plant CW composition and structure for mechanical protection. Understanding these plant shell concepts might inspire biomimetic material developments as well as using walnut and pistachio shell waste as sustainable raw material in future applications.

scholarly journals An Examination on Performance of Railway Sleepers

2019 ◽  
Vol 8 (4S2) ◽  
pp. 37-44 ◽  
Keyword(s):  
Failure Mechanisms ◽  
Cost Effective ◽  
Raw Material ◽  
Maintenance Cost ◽  
Sustainable Engineering ◽  
Production Activity ◽  
Transport Safety ◽  
To Come ◽  
Defensive Action

The main focus of railways is of all economies, transporting items, and passengers. The important role of sleepers is the performance of track and rail transport safety. In sleeper manufacturing, different kinds of materials (Timber, Concrete, and Steel) are utilized. The most widely used sleeper material is Hardwood Timber. The demand for sleepers will move on lots better side in time to come back due to the failures of the Sleepers. The production and maintenance cost of the sleeper is higher. This paper discusses the different failures of classic concrete, steel, and timber sleepers and the capacity of defensive action to minimize those failures. This paper comprehensively evaluates with the recommended solutions for the three typically used sleeper materials of its failure mechanisms. In order to make cost-effective sleeper, the waste materials from industries can be used as supplementary raw material with a purpose to result in enhancing the great for the environment as properly. For the approaching years, every production activity needs to focus on sustainable engineering and this study tries to present the alternative smart solution for the destiny infrastructure engineering region

scholarly journals Water permeability of argillite-based ceramic tiles

2018 ◽  
Vol 196 ◽  
pp. 04072
Author(s):  
Yana Lazareva ◽  
Anton Kotlyar ◽  
Marina Orlova ◽  
Kira Lapunova
Keyword(s):  
Water Absorption ◽  
Water Permeability ◽  
Bending Strength ◽  
High Strength ◽  
Raw Material ◽  
Ceramic Tiles ◽  
Burning Temperature ◽  
Southern Russia ◽  
Biological Corrosion

The article presents the results of experiments to determine the interconnection between water impermeability and water absorption of ceramic tiles obtained on the basis of argillite-like clays that are widespread in the Southern Russia. It is shown that with a decrease in water absorption, the permeability of ceramics is normally reduced. It is found out that with 5% water absorption, a tile can be considered guaranteed waterproof. In this case, the index is independent of the tile thickness. It has been proved that it is possible to reduce the water absorption and increase the bending strength of tiles based on argillite-like clays by finer grinding of raw material or increasing the burning temperature. It is justified that the production of ceramics with high strength and low water absorption makes it possible to produce tiles with a smaller thickness and weight, as well as with lesser probability of biological corrosion.

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