• Title, Summary, Keyword: Mechanochemical

Search Result 129, Processing Time 0.041 seconds

Fabrication of SiC-TiC Composites via Mechanochemical Synthesis

  • Park, Heon-Jin;Lee, Ki-Min;Kim, Hyung-Jong;Lee, June-Gunn
    • Journal of the Korean Ceramic Society
    • /
    • v.38 no.4
    • /
    • pp.314-318
    • /
    • 2001
  • SiC-TiC composites have been fabricated by using a mechanochemical processing of a mixture of Si, Ti, and C at room temperature and subsequent hot pressing. TiC powders have been obtained by the mechanochemical processing of a mixture of Ti and C whereas SiC powders has not been obtained from a mixture of Si and C. By using the exothermic reaction between Ti and C, SiC-TiC powder could be obtained from the mixture of Si, Ti, and C using the mechanochemical processing for more than 12h. The X-ray diffraction analysis has shown that the powder subjected to the mechanochemical processing consisted of the particles having crystallite size below 10nm. Fully densified SiC-TiC composites have been obtained by hot-pressing of the powder at 1850$\^{C}$ for 3h and it has shown comparable mechanical properties to those of the SiC-TiC composites prepared from the commercially available SiC and TiC powders. Flexural strength of 560 MPa and fracture toughness of 4.8 MP$.$am$\_$1/2/ have been shown for the SiC-TiC composites with composition corresponding to 0.75:0.25:1 mole ratio of Si:Ti:C.

  • PDF

Effects of Mechanochemical Pretreatment on the Extraction of Functional Materials from Houttuynia cordata

  • Park, Keum-Joo;Song, Won-Seob;Islam, Mohammad Nazrul;Lee, Jong-Ill;Kim, Yang-Soo
    • Korean Journal of Plant Resources
    • /
    • v.24 no.3
    • /
    • pp.309-313
    • /
    • 2011
  • Houttuynia cordata is used as a raw material of oriental medicine to acquire antioxidant and anti cancer effect and to cure a heart disease. Mechanochemical technology not only reduces the size of the object but also changes the chemical properties of the object. Extraction of functional materials from the Houttuynia cordata after grinding as a pretreatment using the mechanochemical technology was conducted in this study to investigate the effect of grinding on the yields and antioxidant activities of the extract. Houttuynia cordata was ground by the planetary ball mill and the morphology was analyzed by SEM. Yields of functional materials were increased from 6.2 g in the sample without grinding to 7.0, 7.8, 8.8 g after grinding of 30 minutes, 1 hour and 2 hours, respectively. Nitrite scavenging abilities were increased from 57-77% to 69-86% as a result of mechanochemical pretreatment. Also, DPPH scavenging abilities for the methanol extraction were increased from 10.01-40.29% to 11.01-49.29% as a result of mechanochemical grinding.

Mechanochemical Treatment of Quartz for Preparation of EMC Materials

  • Shin, Hee-Young;Chae, Young-Bae;Park, Jai-Koo
    • Proceedings of the IEEK Conference
    • /
    • /
    • pp.315-324
    • /
    • 2001
  • Mechanochemical effects that occurred in the fine grinding process of quartz particles using planetary ball mill was investigated. Quartz particles have been frequently utilized for optical materials, semiconductor molding materials. We determined that grinding for a long time can be create amorphous structures from the crystalline quartz by Mechanochemical effects. But, to be produced nano-composite particles that the critical grinding time reached for composite materials in a short time. Henceforth, a qualitative estimation must be conducted on the filler for EMC(Epoxy molding compound) materials. It can be produced mechanochemically treated composite materials and also an integrated grinding efficiency considering of the nano-composite amorphous structured particles. The mechanochemical characteristics were evaluated based on particle morphology, size distribution, specific surface area, density and the amount of amorphous phase materials into the particle surface. The grinding operation in the planetary ball mill can be classified into three stages. During the first stage, initial particle size was reduced for the increase of specific surface area. In the second stage, the specific surface areas increased in spite of the increase in particle size. The final stage as a critical grinding stage, the ground quartz was considered mechanochemically treated particles as a nano- composite amorphous structured particles. The development of amorphous phase on the particle surface was evaluated by X-ray diffractometry, thermal gravity analysis and IR spectrometer. The amount of amorphous phase of particles ground for 2048 minutes was 85.3% and 88.2% by X-ray analysis and thermal gravity analysis, respectively.

  • PDF

Electrochemical Properties of LiCoO2 Prepared by Mechanochemical Process (Mechanochemical Process로 제조된 LiCoO2의 전기화학적 특성)

  • Cho, Byung-Won;Lee, Joong Kee;Lee, Jae-Ryong;Kim, Su-Jin;Lee, Kwan-Young;Na, Byung-Ki
    • Korean Chemical Engineering Research
    • /
    • v.46 no.1
    • /
    • pp.69-75
    • /
    • 2008
  • Discharge capacity of $LiCoO_2$ in preparation by mechanochemical process decreased remarkably over 4.3V. However, Zr coating of $LiCoO_2$ showed very stable electrochemical properties up to 4.5V. Zr coating of $LiCoO_2$ in this experiment showed the discharge capacity of 197 mAh/g at 3.0-4.5V, and it maintained 96% of the initial discharge capacity after 50 cycle of charge/discharge.

Nano-particles of Mechanochemical Synthesis

  • Urakaev, Farit Kh.
    • Journal of the Speleological Society of Korea
    • /
    • no.71
    • /
    • pp.5-11
    • /
    • 2006
  • A theoretical investigation of the solid phase mechanochemical synthesis of nano sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3 mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano TlCl by dilution of initial (2NaCl+$Tl_2SO_4$) mixture with the exchange reaction product (diluent,$zNa_2SO_4$, z=z*=11.25) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano TlCl obtained experimentally were compared with those for the model reaction KBr+TlCl+zKCl=(z+1) KCl+TlBr (z=z1*=13.5), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

Application of Mechanochemical Processing for Preparation of Si3N4-based Powder Mixtures

  • Sopicka-Lizer, Malgorzata;Pawlik, Tomasz
    • Journal of the Korean Ceramic Society
    • /
    • v.49 no.4
    • /
    • pp.337-341
    • /
    • 2012
  • Mechanochemical processing (MCP) involves several high-energy collisions of powder particles with the milling media and results in the increased reactivity/sinterability of powder. The present paper shows results of mechanochemical processing (MCP) of silicon nitride powder mixture with the relevant sintering additives. The effects of MCP were studied by structural changes of powder particles themselves as well as by the resulting sintering/densification ability. It has been found that MCP significantly enhances reactivity and sinterability of the resultant material: silicon nitride ceramics could be pressureless sintered at $1500^{\circ}C$. Nevertheless, a degree of a silicon nitride crystal lattice and powder particle destruction (amorphization) as detected by XRD studies, is limited by the specific threshold. If that value is crossed then particle's surface damage effects are prevailing thus severe evaporation overdominates mass transport at elevated temperature. It is discussed that the cross-solid interaction between particles of various chemical composition, triggered by many different factors during mechanochemical processing, including a short-range diffusion in silicon nitride particles after collisions with other types of particles plays more important role in enhanced reactivity of tested compositions than amorphization of the crystal lattice itself. Controlled deagglomeration of $Si_3N_4$ particles during the course of high-energy milling was also considered.

Mechanochemical Synthesis of $Ba(Mg_{1/3}Nb_{2/3})O_{3}$ Ceramics (메카노케미컬 방식에 의한 BMN 세라믹 합성)

  • 조정호;조종래;김강언;정수태;조상희
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.208-211
    • /
    • 2000
  • Ba(Mg$_{1}$3/$Nb_{2/3}$)O$_3$ powders were synthesised from mechanochemically treated mixtures of Ba(OH)$_2$. 8$H_2O$, MgO and Nb$_2$O$_{5}$. Perovskite BMN powder of nanosized particles was successfully synthesized by using mechanochemical methods. Density and dielectric constant of samples with mechanochemical methods showed higher values than those of conventional processing.ng.

  • PDF

Synthesis of Eu3+ Doped (Y,Gd)BO3 Powder by Mechanochemical Process (기계 화학적 방법을 통한 Eu3+ 도핑된 (Y,Gd)BO3 형광체의 분말제조)

  • Won, Hee-Sub;Lee, Wan-Jae;Kim, Je-Seok;Hong, Gun-Young;Lee, Kun-Jae;Choa, Yong-Ho
    • Journal of Korean Powder Metallurgy Institute
    • /
    • v.15 no.2
    • /
    • pp.136-141
    • /
    • 2008
  • The mechanochemical process were employed to prepare the red phosphors (Y,Gd)$BO_3:Eu^{3+}$. The main factors affecting particle size, particle distribution, and luminescent properties of the product were investigated in details. Particles sized around 200-600 nm are formed after intensive milling. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum. Results revealed that phosphors with different morphology, small particle size and high luminescence intensity could be obtained by mechanochemical process.

Mechanochemical Synthesis of LaNiO3 Crystalline Phase from Mixture of La2O3sub> and NiO (La2O3의 메카노케미컬 합성에 의한 LaNiO3결정상 생성)

  • 김대영;김강언;이명교;정수태
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.16 no.8
    • /
    • pp.681-687
    • /
    • 2003
  • The syntheses of LaNiO$_3$Perovskite crystalline phase from mixtures of La$_2$O$_3$and NiO via it mechanochemical(used planetary mill) and a wet ball mill process were investigated. A single and stable LaNiO$_3$perovskite crystalline phase was successfully prepared by using a heat free mechanochemical process which produced a fine amorphous powder, while that phase was not formed in a wet ball mill process which needed heat treatment ranging from 500 to 150$0^{\circ}C$ and produced a coarse powder. It was shown that the LaNiO$_3$ceramics made of the mechanochemically synthesized powder possesed a good metallic characteristic.

A Study on the Nano-Deformation Behaviors of Single Crystal Silicon and Amorphous Borosilicate Considering the Mechanochemical Reaction (기계화학적 반응을 고려한 단결정 실리콘과 비정질 보로실리케이트의 나노 변형 거동에 관한 연구)

  • 윤성원;신용래;강충길
    • Transactions of Materials Processing
    • /
    • v.12 no.7
    • /
    • pp.623-630
    • /
    • 2003
  • Nanomachining process, static nanoplowing, is one of the most promising lithographic technologies in terms of the low cost of operation and variety of workable materials. In nanomachining process, chemical effects are more dominant factor compared with those by physical deformation or fracture. For example, during the nanoscratch on a silicon surface in the atmosphere, micro protuberances are formed due to the mechanochemical reaction between diamond tip and the surfaces. On the contrary, in case of chemically stable materials, such as ceramic or glass, surface protuberances are not formed. The purpose of this study is to understand effects of the mechanochemical reaction between tip and surfaces on deformation behaviors of hard-brittle materials. Nanometerscale elasoplastic deformation behavior of single crystal silicon (100) was characterized with micro protuberance phenomena, and compared with that of borosilicate (Pyrex glass 7740). In addition, effects of the silicon protuberances on nanoscratch test results were discussed.