• Title/Summary/Keyword: glass particles

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Mechanical Properties and Microstructure of Dental Heat-Pressable Glass-Ceramics (치과용 열가압 글라스 세라믹스의 기계적 성질과 미세구조)

  • 이해형;이병택
    • Journal of the Korean Ceramic Society
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    • v.41 no.2
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    • pp.143-150
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    • 2004
  • Biaxial flexure strength (ball-on-3-ball) and fracture toughness (indentation microfracture) of heat-pressable glass-ceramics for dental use were investigated in this study. Crystal phase and microstructure of glass-ceramics were analyzed by XRD. SEM, and TEM. Crack propagation in specimens was not effectively arrested by dispersed crystalline particles. However, higher degree of crystallization probably contributes to strengthening of glass-ceramics. Better clinical reliability can be expected from lithium disilicate glass-ceramic because of its significantly higher biaxial flexure strength and fracture toughness.

Preparation of Fine Single-Crystalline Particles of Ferroxplana, Ba2Zn2Fe12O22 from Crystallization of Glass (유리결정화에 의한 Ferroxplana Ba2Zn2Fe12O22 미세 단결정의 제조)

  • 김성재;김동호;김태옥
    • Journal of the Korean Ceramic Society
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    • v.29 no.10
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    • pp.765-772
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    • 1992
  • As the fundamental research of preparation of fine single crystalline ferroxplana by means of glass-crystallization methods using steel twin-roller the properties of ferroxplana extracted from cyrstallized glass were studied. Most of all the specimens quenched by twin-roller at about 1350$^{\circ}C$ were glass phase, the crystallization of these glass had multi-steps and ferroxplana phase was only stable untill 900$^{\circ}C$, began to be decomposed from about 950$^{\circ}C$ in glass. The morphology of particle could be controlled by the composition and crystallization condition, and Zn2+ was replaced by reduced Fe2+ which is 2∼3% contents of total Fe. Ferroxplana extracted had such magnetic properties as Ms=34 emu/g, mHc=10 Oe and Curie Temperature, Tc=425K.

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EFFECT OF GLASS-COATED Al PASTE ON BACK-SURFACE FIELD FORMATION IN Si SOLAR CELLS

  • HYEONDEOK JEONG;SUNG-SOO RYU
    • Archives of Metallurgy and Materials
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    • v.65 no.3
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    • pp.989-992
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    • 2020
  • In this study, glass frit was coated uniformly on the surface of Al particles instead of adding glass frit to Al powder by simple mixing to form a nano-layer. The influence of the glass-frit coating on the formation of the back-surface field and electrical characteristics of the resulting Al electrode were investigated. Microstructural observations indicated that the glass components were uniformly distributed and the back-surface field layer thickness was more uniform compared to the simply mixed sample. In addition, the sheet resistance was <10 mΩ/□, much lower than the 23 mΩ/□ of the simply mixed Al electrode.

Thermal degradation properties of blue emitting phosphor particles prepared by the spray pyrolysis for PDP (분무열분해공정에서 제조된 PDP용 청색형광체의 열화특성)

  • Kang, Yun-Chan;Lee, Dong-Youl;Park, Hee-Dong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07b
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    • pp.1060-1062
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    • 2002
  • Spherical and dense BAM phosphor particles were prepared by spray pyrolysis. The key idea of dense BAM particles is to lead gelation in droplets, which was successfully achieved by using the aluminum polycation as the precursor solution for the spray pyrolysis. The BAM phosphor particles prepared by spraying the aluminum polycation solution have completely spherical shape and dense structure. When directly applied to make phosphor film on the glass by the screen-printing method, the prepared spherical BAM phosphor particles showed better packing density and surface morphology than that of commercial one, which has irregular shape and large particle size. It was also found that the thermal degradation in the photoluminescence intensity for dense and spherical BAM particles was less than that of commercial one.

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Preparation of Silica Particles by Emulsion-Gel Process Using Membrane Emulsification (막유화 에멀젼-겔 공정에 의한 실리카 입자의 제조)

  • Yeon, Song-Hee;Youm, Kyung-Ho
    • Membrane Journal
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    • v.20 no.2
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    • pp.87-96
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    • 2010
  • We prepared spherical silica particles by controlling various conditions of emulsion-gel procedure using a lab-scale membrane emulsification system equipped with SPG (Shirasu porous glass) membrane having pore size of 2.6 ${\mu}m$. We determined the effects of process parameters of membrane emulsification (dispersed phase pressure, stabilizer and emulsifier concentration in continuous phase, $H_2O$/TEOS ratio, ratio of dispersed phase to continuous phase) on the mean size and size distribution of silica particles. The increase of the dispersed phase pressure and ratio of dispersed phase to continuous phase led to the increase in the mean size of silica particles. On the contrary, the increase in stabilizer and emulsifier concentration and $H_2O$/TEOS ratio caused the reduction of the mean size of particles. Through controlling these parameters, monodisperse spherical silica particles with about 3 ${\mu}m$ of the mean size were finally prepared.

Detection of different foreign bodies in the maxillofacial region with spiral computed tomography and cone-beam computed tomography: An in vitro study

  • Abolvardi, Masoud;Akhlaghian, Marzieh;Shishvan, Hadi Hamidi;Dastan, Farivar
    • Imaging Science in Dentistry
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    • v.50 no.4
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    • pp.291-298
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    • 2020
  • Purpose: The detection and exact localization of penetrating foreign bodies are crucial for the appropriate management of patients with dentoalveolar trauma. This study compared the efficacy of cone-beam computed tomography (CBCT) and spiral computed tomography (CT) scans for the detection of different foreign bodies composed of 5 frequently encountered materials in 2 sizes. The effect of the location of the foreign bodies on their visibility was also analyzed. Materials and Methods: In this in vitro study, metal, tooth, stone, glass, and plastic particles measuring 1×1×1 mm and 2×2×2 mm were prepared. They were implanted in a sheep's head in the tongue muscle, nasal cavity, and at the interface of the mandibular cortex and soft tissue. CBCT and spiral CT scans were taken and the visibility of foreign bodies was scored by 4 skilled maxillofacial radiologists who were blinded to the location and number of foreign bodies. Results: CT and CBCT were equally accurate in visualizing metal, stone, and tooth particles of both sizes. However, CBCT was better for detecting glass particles in the periosteum. Although both imaging modalities visualized plastic particles poorly, CT was slightly better for detecting plastic particles, especially the smaller ones. Conclusion: Considering the lower patient radiation dose and cost, CBCT can be used with almost equal accuracy as CT for detecting foreign bodies of different compositions and sizes in multiple maxillofacial regions. However, CT performed better for detecting plastic particles.

Physical and Antibacterial Evaluation of Copper/Bioglass Nanoparticles (Cu/Bioglass Nano Particles; Cu-BGn) in Mineral Trioxide Aggregate(MTA) (구리/생체활성유리나노입자(Cu/Bioglass nano particles;Cu-BGn)를 첨가한 Mineral Trioxide Aggregate (MTA)의 물성 및 항균 평가)

  • Kim, Dong-Ae;Jun, Soo-Kyung
    • The Journal of the Korea Contents Association
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    • v.20 no.6
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    • pp.425-432
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    • 2020
  • For this study copper ions-containing bioactive glass nanoparticles commonly used in mineral trioxide aggregate (MTA) was developed to improve the mechanical properties and promote antibacterial effect of MTA with the original material. The mechanical properties and antibacterial activity of Cu-BGn incorporating varying amounts cooper incorporated bioactive glass nano particles(BGn) 0.5,1.0,2.0 and 4.0 wt% in MTA were characterized composition of the resulting were investigated. The compressive strength was calculated by weighing specimens with a diameter of 4 mm and a thickness of 6 mm according to ISO 6876 (2012). The antimicrobial effect was evaluated using two strains of S. mutans and E. faecalis. The mechanical properties of the test results was Cu-BGn increased no statistically significant difference was observed (p>0.05). Adhesion experiment results S. mutans in contrast to the control group Ortho MTA, 4.0 wt% of Cu-BGn added experimental group showed a significant difference was observed (p<0.05). Also, E. faecalis statistical analysis indicated a significant difference for antibacterial agents between control and Cu-BGn containing(p<0.05). It seems that this Cu-BGn proved that even a antibacterial effect was demonstrated. Therefore, it was suggest that it is necessary for in-depth research into various environments that can reproduce the oral environment.

Effect of Void Formation on Strength of Cemented Material (고결 지반 내에 형성된 공극이 강도에 미치는 영향)

  • Park, Sung-Sik;Choi, Hyun-Seok;Kim, Chang-Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2C
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    • pp.109-117
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    • 2010
  • Gas hydrate dissociation can generate large amounts of gas and water in gas hydrate bearing sediments, which may eventually escape from a soil skeleton and form voids within the sediments. The loss of fine particles between coarse particles or collapse of cementation due to water flow during heavy or continuous rainfall may form large voids within soil structure. In this study, the effect of void formation resulting from gas hydrate dissociation or loss of some particles within soil structure on the strength of soil is examined. Glass beads with uniform gradation were used to simulate a gas hydrate bearing or washable soil structure. Glass beads were mixed with 2% cement ratio and 7% water content and then compacted into a cylindrical sample with five equal layers. Empty capsules for medicine are used to mimic large voids, which are bigger than soil particle, and embedded into the middle of five equal layers. The number, direction, and length of capsules embedded into each layer vary. After two days curing, a series of unconfined compression tests is performed on the capsule-embedded cemented glass beads. Unconfined compressive strength of cemented glass beads with capsules depends on the volume, direction and length of capsules. The volume and cross section formed by voids are most important factors in strength. An unconfined compressive strength of a specimen with large voids decreases up to 35% of a specimen without void. The results of this study can be used to predict the strength degradation of gas hydrate bearing sediments in the long term after dissociation and loss of fine particles within soil structure.

Crystallization in Li$_2$O-A1$_2$O$_3$-SiO$_2$ Glass induced by 355 nm Nd:YAG Laser Irradiation

  • Lee, Yong-Su;Kang, Won-Ho
    • Journal of the Microelectronics and Packaging Society
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    • v.7 no.2
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    • pp.43-46
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    • 2000
  • Nd:YAG laser of 355 nm wavelength, which amounts to 3.5 eV, produced by a harmonic generator was used to create Ag metallic particles as seeds for nucleation in photosensitive glass containing $Ag^+$ and $Ce^{3+}$ . The pulse widths and frequency of the laser were 8ns and 10 Hz, respectively. For crystalline growth, heat-treatment following laser irradiation was carried out at $570^{\circ}C$ for 1h. Then, the $LiAlSi_3O^8$ crystal phase appeared in the laser irradiated lithium aluminum silicate glass. We present the effect of laser-induced nucleation compared with spontaneous nucleation by heat treatment fur crystallization in the glass.

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Pressure Loss and Heat Transfer Characteristics of the Glass Beads-Water Flow in a Vertical Tube (수직관내 유리알-물 유동의 압력손실 및 열전달 성능)

  • Kim, N.H.;Kim, J.S.;Lee, Y.P.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.4
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    • pp.550-560
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    • 1996
  • Recently, fluidized bed heat exchangers with circulating liquid are widely used in a number of places-chemical, process, food concentration, waste water treatment facilities, etc. In a circulating heat exchanger, solid particles circulate with the liquid, thereby increase the heat transfer and reduce the fouling potential of the heat exchanger. In this study, glass beads were circulated through a vertical tube. The pressure loss and the heat transfer coefficient were measured. At low flow velocities, glass beads enhanced the heat transfer considerably. The enhancement increased as the volume fraction of the glass beads increased. The pressure loss showed a similar trend. From the observed particle behavior near tube wall, a possible explanation of the trend is provided.

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