Pirinç kabuğundan silisyum nitrür tozunun sentezi
Synthesis of silicon nitride powder from rice husk
- Tez No: 39243
- Danışmanlar: PROF.DR. OKAN ADDEMİR
- Tez Türü: Doktora
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 100
Özet
ÖZET Bu çalışmada Trakya(Enez) yöresine ait pirinç kabuk ları kullanılarak silisyum Nitrür (Si"N, ) toz sentezi yapılmıştır. Pirinç kabukları, 7DDQC'de argon gazı altında piro- liz işlemi sonunda öğütülerek
Özet (Çeviri)
SYNTHESIS OF SILICON NITRIDE PGlılDER FRGH RICE HUSK SUMMARY Silicon Nitride is a material used in high technology applications. This is mainly due to oxidation resistance at elevated temperatures low density, high hardness and strength of the material. These properties make silicon nitride an ideal candidate to be used as high temperature turbine components, bearings and cotting tools. World production of Si.,N, pouders are unavailable, but it is estimated that anual production world wide of Si3N, powder is about 5D0 metric tons. Many of the manufactures of Si“N, products make their own powder but there is apparently no domestic commercial supplier of Si,N,. Powder can be purchased from sources in Germany 3apan, Sweden and the United Kingdom. Preces vary from $/kg to 350 $/kg depending on specified particle size and purity. There are several routes available for the produc tion of silicon nitride powders; these include: 1)- Direct nitridation of silicon with nitrogen 2)- Vapour phase reactions between silicon halides and ammonia 3)- Reaction between silica and ammonia k)- Carbotermal reduction and nitridation of silica with nitrogen. Direct silicon nitridation is widely used because it is the simplest method of silicon nitride formation. However, it is difficult to control particle shape and size, as well as the high a -phase content, because of an intrinsic reaction mechanism in the silicon and nitrogen. vııVapor phase reaction has been widely used in the semiconductor industry as a synthesis method for pure silicon nitride. The silicon imide decomposition met hod is a recent development in which pure a -silicon nitride can be obtained. Carbothermal reduction and nitridation of silicon dioxide is of commerical interest since this method yields powder with small particle size and high purity, therefore, specific emphasis is given to the development of this method since 1970's. According to these studies, main parameters effecting Si-N., formation in SiG2-N”-C system are found to be reaction temperature, N2 gas flow rate specific surface of silica and C powder, and particle size, Si,N. addition as seeding additive, existence of Fe impurity, C/Si02 ratio in the initial mixture. Various raw materials can be used as silica and carbon source; some Df them are: sublimated silica, amporphous silica, silica precipitate from geothermal waters, graphite, and strach. The use of rice husk as C and Silica source is itageous in producing a -5i,N, pa.cle size, since it provides Homo mixture with very fine particle size. advantageous in producing a -5i,N, powder with small particle size, since it provides Homogenous C+SiD“ Production of Si”N, powder is of significant im portance for Turkey, since this would not only.create an apportunity for enterprise but would also develop an understanding for high technology ceramics. Therefore the scope of this thesis is to develop a method for carbothermal reduction and subsequent nitri dation of rice huks obtained from Enez/Trakya region. As can be seen at the flowchart in figure, pyrolized rice husks are subjected to a nitridation process in a kk kVA Tammann furnace under N“ gas. The effects of reaction temperature and duration N? flow rate, charging way of pyrolized rice husk to vmthe graphite reactor, addition of seeding Si-N, powder on Sİ..N, recovery and product morphology were examined. Also, formation mechanisms of Si,N, was determined according to CO measurements of exhaust gases and to weight losses during the reaction, and the effects of impurity Fe on Si.,N, - SiC equilibrium was investigated. As a result of the research presented in this desertation, the Enez/Trakya rice husk was characterised and found to be fiberous material composed of amorphors silica. It was shown that, through pyrolysis at 7DD C under Ar gas, the rice husk can be turned in to a raw material containing % 47.9 SiO- and 50 % C to be used in Si”N, synthesis. It was unterstood that whether Si-N, or SiC forms is related to N? gas partial pressure. Nitridation yield was found to be related to the l\L flow gase up to a certain value after which the yield was constant. The optimum conditions for Si_l\l, formation were deter mined to be 1400 C temperature and 2 h. duration at 50 L/h flow rate of N“. Above 1400 C partly turns into SiC due to the presence of excess carbon; Si,N. + 3C * 3SİC + 2N”3 4 2 Since carbon is already present in the raw material, it was found that the particle shape of the raw material, whether powder or pellete (+ 3.15-4.75, + 4.75-5.6 mm) does not have influence on the 5i,N, formation yield. ieding the charge with Si-N, at 1400DC and 50 l/h )w, on the other hand, effects the product Set gas floi morphology but not the formation yield. When the CO concentration in exhaust gas was monitered, it was observed that CO concentration increases suddenly during heating up to 1400 C and then decreases in 2 steps in the case of no seeding and decreases linearly in the case of seeding. The sudden increase was attributed to the reduction of SiO^. The first step in CO concentration of nucleoids and the secent Step being the growth of the nuclei. In the case of seeding, the CO concentration decrease was uniform till stabilization since the nuclei were already present. IXRice Husk I Pyroliysis Process 7G0DC 1 hour Argon gas Milling 53 Jim Pelletizing % 1 PUA solution Carbothermal Reduction and Nitridation 1350° - 15DD°C ^N2- Deoxidation (0.1 ppm D2) (100 ppm 0") Decarburization 700°C, 3 hours X-ray diffraction: Recovery analysis 1 Purificaiton from amorphous Silica Pure 5iJ\l, powder Air % 20 NaOH solution FIGURE: 1. Flowchart of Si-N, Powder Production From Rice Husk.The weight lass during the recduction was found to be more than the theoretical valve. This was attributed to the formation and evoparation of SiO before the tem perature reaches to thermodynamically feasible valve. It was found that the morphology of the product, whether whisker or powder; is related to reactant gas partical pressure and the seeding additive. It was interesting to note that the whiskers formed at T+QOaC one Si,N, but above 1^00 C, impurity iron forms Fe-Si intermetallic compound which disolves carbon and then helps the precipitation of SiC. XI
Benzer Tezler
- Pirinç kabuklarından karbotermal redüksiyon ve nitrürleme yöntemiyle Sic-SiN4 seramik kompozit tozu sentezi
Başlık çevirisi yok
ATİLLA SİNAN SAYGINER
- Investigation of the production of silicon nitride from Turkish rice husks
Türk pirinç kabuklarından silisyum nitrür üretiminin araştırılması
BARIŞ YİĞİT ALPAY
Yüksek Lisans
İngilizce
2014
Kimya MühendisliğiOrta Doğu Teknik ÜniversitesiMetalurji ve Malzeme Mühendisliği Ana Bilim Dalı
PROF. DR. YAVUZ ALİ TOPKAYA
PROF. DR. AHMET GEVECİ
- Karbotermal redüksiyon yöntemiyle ön şekillendirilmiş silisyum karbür üretim parametrelerinin incelenmesi
Observation of pre-shaped SiC production parametres with carbothermal reduction process
CİHAN BALABAN
- Pirinç kabuğu külünün sinter kuvars olarak bünyelerde kullanılma olanaklarının araştırılması ve özgün form uygulamalarındaki etkileri
Investigation of possibilities of use of rice husks ash as quartz and effect on original form application
NAGİHAN GÜMÜŞ AKMAN
Yüksek Lisans
Türkçe
2017
Güzel SanatlarHacettepe ÜniversitesiSeramik Ana Sanat Dalı
PROF. KAAN CANDURAN
- Silicon carbide (SiC) whisker production from rice husks of Black Sea and Thrqce regions of Turkey
Türkiye'nin Karadeniz ve Trakya bölgelerindeki pirinç kabuklarından üretilen silisyum karbür (SiC) visker üretimi
YİĞİT ALİ RIZA YÜCEL
Yüksek Lisans
İngilizce
1997
Metalurji MühendisliğiOrta Doğu Teknik ÜniversitesiMetalurji ve Malzeme Mühendisliği Ana Bilim Dalı
PROF. DR. AHMET GEVECİ