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.

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 ◽  
pp. 31-34
Author(s):  
Hiromasa Yabuki ◽  
Toru Wakihara ◽  
Junichi Tatami ◽  
Katsutoshi Komeya ◽  
Takeshi Meguro ◽  
...  
Keyword(s):  
Reaction Sintering ◽  
Sintering Shrinkage ◽  
Shrinkage Behavior

Sintering Shrinkage Behavior and Mechanical Properties of HfO2-Added Si3N4 Ceramics

2008 ◽  
Vol 403 ◽  
pp. 35-38 ◽  
Author(s):  
Daisuke Horikawa ◽  
Junichi Tatami ◽  
Toru Wakihara ◽  
Katsutoshi Komeya ◽  
Takeshi Meguro
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Boundary Phase ◽  
High Temperature Strength ◽  
Powder Mixtures ◽  
Sintering Aid ◽  
Liquid Phases ◽  
Sintering Shrinkage ◽  
Si3n4 Ceramics ◽  
Shrinkage Behavior

HfO2-added Si3N4 ceramics are known to exhibit excellent high-temperature strength and excellent damage characteristics because HfO2 assists the crystallization of the grain boundary phase. However, the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4 have not been well clarified so far, although it has been reported that TiO2, in which Ti is from the same group as Hf in the periodic table, enhances the densification of the Si3N4-Y2O3-Al2O3-AlN system and wear resistance due to TiN formed from TiO2 and AlN in the grain boundary. In the present study, we focus on HfO2 as the sintering aid to investigate the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4. The powder mixtures are prepared by the addition of HfO2 to the Si3N4-Y2O3-Al2O3 or Si3N4-Y2O3-Al2O3-AlN system. The sintering shrinkage curves of HfO2-added Si3N4 ceramics show rapid shrinkage at 1600°C as compared with those of the Si3N4 ceramics without HfO2.The shrinkage can be explained by the formation of SiO2-Y2O3-HfO2 derived liquid phases. Furthermore, the mechanical properties of HfO2-added Si3N4 were as excellent as those of the Si3N4 ceramics without HfO2.

Teknologi Esktrasi dan Cara Pemisahannya untuk Mendapatkan Kembali Karotenoid dari Minyak Sawit : Suatu Tinjauan

2016 ◽  
Vol 9 (1) ◽  
pp. 80-95
Author(s):  
Agus Sudibyo ◽  
Sardjono Sardjono
Keyword(s):  
Vitamin A ◽  
Palm Oil ◽  
Beta Carotene ◽  
Cost Effective ◽  
Raw Material ◽  
Extraction And Separation ◽  
Molecular Product ◽  
Industrial Use ◽  
Palm Oil Mill ◽  
Selection Of

Crude palm oil (CPO)is the richest natural plant source of carotenoids in terms of retinol (pro-vitamin A) equivalent, whereas palm oil mill effluent (POME) is generated from palm oil industry that contains oil and carotenes that used to be treated before discharge. Carotenoids are importance in animals and humans for the purpose of the enhancement of immune response, conversion of vitamin A and scavenging of oxygen radicals. This component has different nutritional  functions and benefits to humaan health. The growing interest in the other natural sources of beta-carotene and growing awareness to prevent pollution has stimulated the industrial use of CPO and POME as a raw material for carotenoids extraction. Various technologies of extraction and separation have been developed in order to recover of carotenoids.This article reports on various technologies that have been developed in order to recover of carotenoids from being destroyed in commercial refining of palm oil and effects of some various treatments on the extraction end separation for carotenoid from palm oil and carotenoids concentration. Principally, there are different technologies, and there is one some future which is the use of solvent. Solvent plays important role  in the most technologiest, however the problem of solvents which are used is that they posses potentiaal fire health and environmental hazards. Hence selection of the  most safe, environmentally friendly and cost effective solvent is important to design of alternative extraction methods.Chemical molecular product design is one of the methods that are becoming more popular nowadays for finding solvent with the desired properties prior to experimental testing.ABSTRAKMinyak sawit kasar merupakan sumber karotenoid terkaya yang berasal dari tanaman sawit sebagai senyawa yang sama dengan retinol atau pro-vitamin A; sedangkan limbah pengolahan minyak sawit dihasilkan dari industri pengolahan minyak sawit yang berisi minyak dan karotene yang perlu diberi perlakuan terlebih dahulu sebelum dibuang. Karotenoid merupakan bahan penting yang diperlukan pada hewan dan manusia guna memperkuat tanggapan terhadap kekebalan, konversi ke vitamin A dan penangkapan gugus oksigen radikal. Dengan berkembangnya ketertarikan dalam mencari beta-karotene yang bersumber dari alam lain dan meningkatnya kesadaran untuk mencegah adanya pencemaran lingkungan, maka mendorong suatu industri untuk menggunakan CPO dan POME sebagai bahan baku untuk diekstrak karotenoidnya. Berbagai macam teknologi guna mengekstrak dan memisahkan karotenoid telah dikembangkan untuk mendapatkan kembali karotenoidnya. Makalah ini melaporkan dan membahas berbagai jenis teknologi yang telah dikembangkan guna mendapatkan kembali senyawa karotenoid dari kerusakan di dalam proses pemurnian minyak sawit secara komersial dan pengaruh beberapa perlakuan terhadap ekstrasi dan pemisahan karotenoid dari minyak sawit dan konsentrasi karotenoidnya. Pada prinsipnya, berbagai teknologi yang digunakan untuk mengekstrak dan memisahkan karotenoid terdapat perbedaan, dan terdapat salah satu teknologi yang digunakan untuk esktrasi dan pemisahan karotenoid adalah menggunakan bahan pelarut. Pelarut yang digunakan mempunyai peranan yang penting dalam teknologi ekstrasi; namun pelarut yang digunakan untuk mengekstrak tersebut mempunyai persoalan karena berpotensi mengganggu kesehatan dan membahayakan cemaran lingkungan. Oleh karena itu, pemilihan jenis teknologi yang aman, ramah terhadap lingkungan dan biaya yang efektif untuk penggunaan pelarut merupakan hal penting sebelum dilakukan desain metode/teknologi alternatif untuk esktrasi karotenoid. Pola produk molekuler kimia merupakan salah satu metode yang saat ini menjadi lebih populer untuk mencari pelarut dengan sifat-sifat yang dikehendaki sebelum diujicobakan. Kata kunci :    karotenoid, ekstrasi, pemisahan, teknologi, minyak sawit kasar, limbah industri pengolahan sawit.

scholarly journals End-of-Life Alternatives of Glass Reinforced Polyester Boat Hulls Compared by LCA

2018 ◽  
Vol 27 (4) ◽  
pp. 096369351802700 ◽  
Author(s):  
Mehmet Önal ◽  
Gökdeniz Neşer
Keyword(s):  
End Of Life ◽  
Environmental Impacts ◽  
Raw Materials ◽  
Weight Ratio ◽  
Cost Effective ◽  
Raw Material ◽  
Photochemical Oxidation ◽  
Human Toxicity ◽  
Vacuum Infusion ◽  
Infusion Method

Glass reinforced polyester (GRP), as a thermoset polymer composites, dominates boat building industry with its several advantages such as high strength/weight ratio, cohesiveness, good resistance to environment. However, proper recovering and recycling of GRP boats is became a current environmental requirement that should be met by the related industry. In this study, to propose in a cost effective and environmentally friendly way, Life Cycle Assessment (LCA) has been carried out for six scenarios include two moulding methods (namely Hand Lay-up Method, HLM and Vacuum Infusion Method, VIM) and three End-of-Life (EoL) alternatives(namely Extruding, Incineration and Landfill) for a recreational boat's GRP hulls. A case study from raw materials purchasing phase to disposal/recycling stages has been established taking 11 m length GRP boat hull as the functional unit. Analysis show that in the production phase, the impacts are mainly due to the use of energy (electricity), transport and raw material manufacture. Largest differences between the methods considered (HLM and VIM) can be observed in the factors of marine aquatic ecotoxicity and eutrophication while the closest ones are abiotic depletion, ozon layer depletion and photochemical oxidation. The environmental impact of VIM is much higher than HLM due to its higher energy consumption while vacuum infusion method has lower risk than hand lay-up method in terms of occupational health by using less raw material (resin) in a closed mold. In the comparison of the three EoL techniques, the mechanical way of recycling (granule extruding) shows better environmental impacts except terrestrial ecotoxicity, photochemical oxidation and acidification. Among the EoL alternatives, landfill has the highest environmental impacts except ‘global warming potential’ and ‘human toxicity’ which are the highest in extrusion. The main cause of the impacts of landfill is the transportation needs between the EoL boats and the licenced landfill site. Although it has the higher impact on human toxicity, incineration is the second cleaner alternative of EoL techniques considered in this study. In fact that the similar trend has been observed both in production and EoL phases of the boat. It is obvious that using much more renewable energy mix and greener transportation alternative can reduce the overall impact of the all phases considerably.

Advances in absorbents and techniques used in wet and dry FGD: a critical review

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lokesh Kumar ◽  
Susanta Kumar Jana
Keyword(s):  
Power Plants ◽  
Low Cost ◽  
Fine Particulate Matter ◽  
Packed Column ◽  
Toxic Substance ◽  
Cost Effective ◽  
Solid Wastes ◽  
Raw Material ◽  
Process Industries ◽  
Slurry Bubble Columns

Abstract Sulfur dioxide is considered as an extremely harmful and toxic substance among the air pollutants emitted from the lignite- and other high-sulfur-coal based power plants, old tires processing units, smelters, and many other process industries. Various types of absorbents and desulfurization technologies have been developed and adopted by the industries to reduce the emission rate of SO2 gas. The present paper focuses on the ongoing advances in the development of varieties of regenerative and non-regenerative absorbents viz., Ca-based, Mg-based, Fe-based, Na-based, N2-based, and others along with various FGD technology, viz., wet, dry or semi-dry processes. Additionally, different types of contactors viz., packed column, jet column, spray tower, and slurry bubble columns along with their significant operational and design features have also been discussed. In the existing or newly installed limestone-based FGD plants, an increasing trend of the utilization of newly developed technologies such as limestone forced oxidation (LSFO) and magnesium-enhanced lime (MEL) are being used at an increasing rate. However, the development of low-cost sorbents, particularly suitable solid wastes, for the abatement of SO2 emission needs to be explored sincerely. Many such wastes cause air pollution by way of entrainment of fine particulate matter (PM), groundwater contamination by its leaching, or brings damage to crops due to its spreading onto the cultivation land. One such pollutant is marble waste and in this work, this has been suggested as a suitable substitute to limestone and cost-effective sorbent for the desulfurization of flue gases. The product of this process being sellable in the market or may be used as a raw material in several industries, it can also prove to be an important route of recycling and reuse of one of the air and water-polluting solid wastes.

scholarly journals Chemical Composition and Thermal Behavior of Kraft Lignins

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 483 ◽  
Author(s):  
Aleš Ház ◽  
Michal Jablonský ◽  
Igor Šurina ◽  
František Kačík ◽  
Tatiana Bubeníková ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Cost Effective ◽  
Activation Energies ◽  
Industrial Applications ◽  
Raw Material ◽  
Molecular Weight Determination ◽  
Two Samples ◽  
Process Measurements

Lignin has great potential for utilization as a green raw material or as an additive in various industrial applications, such as energy, valuable chemicals, or cost-effective materials. In this study, we assessed a commercial form of lignin isolated using LignoBoost technology (LB lignin) as well as three other types of lignin (two samples of non-wood lignins and one hardwood kraft lignin) isolated from the waste liquors produced during the pulping process. Measurements were taken for elemental analysis, methoxyl and ash content, higher heating values, thermogravimetric analysis, and molecular weight determination. We found that the elemental composition of the isolated lignins affected their thermal stability, activation energies, and higher heating values. The lignin samples examined showed varying amounts of functional groups, inorganic component compositions, and molecular weight distributions. Mean activation energies ranged from 93 to 281 kJ/mol. Lignins with bimodal molecular weight distribution were thermally decomposed in two stages, whereas the LB lignin showing a unimodal molecular weight distribution was decomposed in a single thermal stage. Based on its thermal properties, the LB lignin may find direct applications in biocomposites where a higher thermal resistance is required.

scholarly journals ASSESSING THE SUITABILITY OF TIGER NUT FIBRE FOR STRUCTURAL APPLICATIONS

2020 ◽  
Vol 3 (01) ◽  
pp. 32-38
Author(s):  
Uduakobong Okorie ◽  
Ubong Robert ◽  
Ubong Iboh ◽  
Grace Umoren ◽  
Grace Umoren
Keyword(s):  
Thermal Conductivity ◽  
Cost Effective ◽  
Waste Recycling ◽  
Cassava Starch ◽  
Fibre Content ◽  
Raw Material ◽  
Structural Applications ◽  
The Mean ◽  
Thermal Absorptivity ◽  
Reduce Health Risk

In this work, the properties of the composite produced from waste carton with various tiger nut fibre contents having cassava starch slurry as binder were investigated. The results obtained showed the ranges of the mean thermal conductivity, bulk density, specific heat capacity, thermal diffusivity, thermal absorptivity, nailability, flexural strength  and compressive strength values to be (0.0447 – 0.0603) Wm-1K-1, (683.62 – 746.32) kgm-3, (1439.811 – 1840.554) J/kg/K, (5.612 - 3.553) 10-8 m2s-1, (25.456 – 31.993) m-1, (23.9 – 100)%, (1.58 – 1.86) MPa and (2.16 – 2.78) MPa respectively between  8.3% and 43.1% of the fibre content.  It was generally observed that with a choice variation in the fibre content, the performance of the developed board can be optimized for structural applications. Hence, instead of discarding the fibre as waste, recycling it can help to provide raw material for the production of cost effective and environmentally friendly materials. This will in turn reduce health risk caused by environmental pollution due to improper waste disposal practice of such material.

scholarly journals Second Generation Biobutanol: An Update

REAKTOR ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 101-110
Author(s):  
Dian Burhani ◽  
Eka Triwahyuni ◽  
Ruby Setiawan
Keyword(s):  
First Generation ◽  
Second Generation ◽  
Cost Effective ◽  
Production Method ◽  
Raw Material ◽  
Food Crops ◽  
Butanol Production ◽  
Clostridium Species ◽  
Food Scarcity ◽  
Absolute Requirement

Butanol, a rising star in biofuel, can be produced by two approaches, petrochemically and biologically. Currently, the most promising route for butanol production is by fermentation using Clostridium species through an anaerobic condition. However, similar to other biofuels, feedstock has greatly influenced the production of biobutanol and the search for inexpensive and abundant raw material is an absolute requirement for a cost-effective process. Second-generation biobutanol which is produced from lignocellulosic biomass of agricultural and forestry waste not only meets the requirement but also alleviates competition with food crops and thereby solves the problems of food scarcity from the first generation biobutanol. This paper delivered the latest and update information regarding biobutanol production specifically second-generation biobutanol in terms of production method, recovery, purification, status, and technoeconomic.  Keyword: biobutanol, lignocellulose, purification, recovery, technoeconomic

scholarly journals Exploiting xylan as sugar donor for the synthesis of an antiproliferative xyloside using an enzyme cascade

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Manuel Nieto-Domínguez ◽  
José Alberto Martínez-Fernández ◽  
Beatriz Fernández de Toro ◽  
Juan A. Méndez-Líter ◽  
Francisco Javier Cañada ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Biomass Conversion ◽  
Value Added ◽  
Cost Effective ◽  
Raw Material ◽  
Birchwood Xylan ◽  
Enzyme Cascade ◽  
Antiproliferative Agent ◽  
Xylanolytic Enzymes ◽  
Value Added Products

Abstract Background Currently, industrial societies are seeking for green alternatives to conventional chemical synthesis. This demand has merged with the efforts to convert lignocellulosic biomass into value-added products. In this context, xylan, as one of main components of lignocellulose, has emerged as a raw material with high potential for advancing towards a sustainable economy. Results In this study, the recombinant endoxylanase rXynM from the ascomycete Talaromyces amestolkiae has been heterologously expressed in Pichia pastoris and used as one of the catalysts of an enzyme cascade developed to synthesize the antiproliferative 2-(6-hydroxynaphthyl) β-d-xylopyranoside, by transglycosylation of 2,6-dihydroxynaphthalene. The approach combines the use of two fungal xylanolytic enzymes, rXynM and the β-xylosidase rBxTW1 from the same fungus, with the cost-effective substrate xylan. The reaction conditions for the cascade were optimized by a Central Composite Design. Maximal productions of 0.59 and 0.38 g/L were reached using beechwood xylan and birchwood xylan, respectively. For comparison, xylans from other sources were tested in the same reaction, suggesting that a specific optimization is required for each xylan variety. The results obtained using this enzyme cascade and xylan were similar or better to those previously reported for a single catalyst and xylobiose, an expensive sugar donor. Conclusions Beechwood and birchwood xylan, two polysaccharides easily available from biomass, were used in a novel enzyme cascade to synthetize an antiproliferative agent. The approach represents a green alternative to the conventional chemical synthesis of 2-(6-hydroxynaphthyl) β-d-xylopyranoside using a cost-effective substrate. The work highlights the role of xylan as a raw material for producing value-added products and the potential of fungal xylanolytic enzymes in the biomass conversion.

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