• Title/Summary/Keyword: Glass Ball

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Mechanical Properties of Zirconia Reinforced Glass-Ceramic (지르코니아 강화형 Glass-Ceramic의 기계적 성질)

  • Park, Eun-Eui;Dong, Jin-Keun;Lee, Hae-Hyoung;Song, Ki-Chang;Oh, Sang-Chun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.17 no.3
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    • pp.199-204
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    • 2001
  • This study was to investigate the reused possibility of zirconia reinforced glass-ceramic(IPS Empress Cosmo ceramic) with sprue button in the flexure strength and fracture toughness. 40 disk-shaped ceramic specimens (20 specimens: as-pressed material; 20 specimens: reused material) with approximately 1.7 mm thickness and 15 mm diameter were prepared by "lost wax" technique. The remnants(sprue buttons) were used for repressing. The surface treatments for the discs were gradually abraded with 320, 800, 1200, and 2000 grit SiC sandpaper. The specimens were evaluated their flexure strength with the biaxial flexure jig(ball-on-three balls) and their fracture toughness with Vickers Indentation-microfracture test. The Weibull moduli were calculated for biaxial flexural strength. The mean flexure strength and fracture toughness of each group were $122.2{\pm}18.3MPa$, $1.00{\pm}0.09MPa{\cdot}m^{0.5}$ (as-pressed ceramics), and $122.2{\pm}20.3MPa$, $1.01{\pm}0.10MPa{\cdot}m^{0.5}$ (reused ceramics). There were no significant differences in the strength and the fracture toughness between the as-pressed and the reused IPS Empress Cosmo ceramic (P>0.05). This implied zirconia reinforced glass-ceramic(IPS Empress Cosmo ceramic) could be used one more time by reusing of sprue button in the flexure strength and fracture toughness.

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Kinetic Study Of $La_2$O_3-A1_2O_3-SiO_2$ glass infiltration into Spinel Preforms (스피넬 전성형체의 $La_2$O_3-A1_2O_3-SiO_2$계 유리 침투 kinetic)

  • 이득용;장주웅;김병수;김대준;송요승
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.12 no.1
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    • pp.31-35
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    • 2002
  • Abstract Spinel powder having a particle size of 0.9$\mu$m was calcined for 30 min at $1300^{\circ}C$, followed by ball milling for 4h, to obtain the spinel particle size of 3.29$\mu$m. The die-pressed spinel was presintered at $1100^{\circ}C$ for 2h and then lanthanum aluminosilicate glass was infiltrated at $1080^{\circ}C$ for 0~2 h to investigate the penetration kinetics in glass-spinel composite. The infiltration distance is parabolic in time due to capillarity. The strength and the fracture toughness of glassspinel composites were 317 MPa and 3.56 MPa $m^{1/2}$ respectively and dual microstructure of column (needle) and polygonal shapes as a result of recrystallization was observed due to the high calcination temperature.

Viator vitreocola gen. et sp. nov. (Stylonematophyceae), a new red alga on drift glass debris in Oregon and Washington, USA

  • Hansen, Gayle I.;West, John A.;Yoon, Hwan Su;Goodman, Christopher D.;Goer, Susan Loiseaux-de;Zuccarello, Giuseppe C.
    • ALGAE
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    • v.34 no.2
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    • pp.71-90
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    • 2019
  • A new encrusting red alga was found growing abundantly on glass debris items that drifted ashore along the coasts of Oregon and Washington. These included discarded fluorescent tubes, incandescent light bulbs, capped liquor bottles, and ball-shaped fishing-net floats. Field collections and unialgal cultures of the alga revealed that it consisted of two morphological phases: a young loosely aggregated turf and a mature consolidated mucilaginous crust. The turf phase consisted of a basal layer of globose cells that produced erect, rarely branched, uniseriate to multiseriate filaments up to $500{\mu}m$ long with closely spaced cells lacking pit-plugs. These filaments expanded in size from their bases to their tips and released single cells as spores. At maturity, a second phase of growth occurred that produced a consolidated crust, up to $370{\mu}m$ thick. It consisted of a basal layer of small, tightly appressed ellipsoidal-to-elongate cells that generated a mucilaginous perithallial matrix containing a second type of filament with irregularly spaced cells often undergoing binary division. At the matrix surface, the original filaments continued to grow and release spores but often also eroded. Individual cells, examined using confocal microscopy and SYBR Green staining, were found to contain a central nucleus, a single highly lobed peripheral chloroplast without a pyrenoid, and numerous chloroplast nucleoids. Morphological data from field and culture isolates and molecular data (rbcL, psbA, and SSU) show that this alga is a new genus and species which we name Viator vitreocola, "a traveller on glass."

Characteristics of Indium Dissolution of Waste LCD Panel Powders Fabricated by High Energy Ball Milling (HEBM) Process with Milling Time (고에너지 밀링으로 제조된 폐디스플레이 패널 분말의 밀링시간에 따른 인듐 용출특성)

  • Kim, Hyo-Seob;Sung, Jun-Je;Lee, Cheol-Hee;Hong, Hyun-Seon;Hong, Soon-Jik
    • Journal of Powder Materials
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    • v.18 no.4
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    • pp.378-384
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    • 2011
  • In this research, the indium dissolution properties of the waste LCD panel powders were investigated as a function of milling time fabricated by high-energy ball milling (HEBM) process. The particle morphology of waste LCD panel powders changed from sharp and irregular shape of initial cullet to spherical shape with an increase in milling time. The particle size quickly decreased to 15 ${\mu}m$ until the first minute, then decreased gradually about 6 ${\mu}m$ with presence of agglomerated particles after 5 minutes, which increased gradually reaching a uniform size of 13 ${\mu}m$ consist of agglomerated particles after 30 minutes. The glass recovery, after dissolution, was over 99% at initial cullet, which decreased to 90.1 and 78.6% with increasing milling time of 1 and 30 minute respectively, due to a loss in remaining powder of the surface ball and jar, as well as the filter paper. The dissolution amount of indium out of the initial cullet was 208 ppm before milling, turning into 223 ppm for the mechanically milled powder after 1 minute, and nearly 146~125 ppm with further increase in milling time because of the reaction surface decrease of powders due to agglomeration. With this process, maximum dissolving indium amount (223 ppm) could be achieved at a particle size of 15 ${\mu}m$ with 1 minute of milling.

Floor Impact Sound Pressure Level Characteristics by the Change of Reverberation Time in a Reverberation Chamber (수음실 잔향 시간변화에 따른 바닥충격음레벨 특성 - 잔향실을 중심으로 -)

  • Jeong, Jeong Ho;Kim, Jeong Uk;Jeong, Jae Gun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.3
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    • pp.274-281
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    • 2013
  • Field measurement method of heavy/soft impact sound pressure level which is regulated in JIS and ISO has been using in Korea, Japan and Canada. It is reported that heavy/soft impact sound pressure level was varied by the sound field condition of receiving room such as sound absorption power and room volume. In this study, it is checked that heavy/soft impact sound pressure level was affected by the receiving sound field condition. Rubber ball and bang machine sound pressure level was measured in the vertically connected reverberation chamber. In oder to check the effect of receiving sound field on heavy/soft impact sound pressure, sound absorption power was changed with polyester sound absorption blankets with air space and glass wool. The reverberation time at 1 kHz band was changed from 10 s to 0.2 s by sound absorption material. Rubber ball sound pressure level measured without sound absorption material was 58 dB in $L_{i,Fmax,AW}$, but the level was 46 dB with sound absorption treatment. From this result, it is confirmed that sound field correction method is needed in the heavy/soft impact sound pressure level measurement method using bang machine and rubber ball.

Research for Controlled Thermal Conductivity of p-Type Skutterudite Materials (P-type Skutterudite 열전소재의 열전도도 제어 연구)

  • Son, Geon Sik;Choi, Soon Mok
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.11
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    • pp.671-675
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    • 2016
  • Skutterudite materials show PGEC (phonon glass electron crystal) characteristics which is an optimal strategy for designing high performance thermoelectric materials. Now two methods are in parallel to control thermal conductivity of skutterudites, a rattler-atoms doping method and a process for nanostructured bulk materials. Amount of rattler atoms in p-type skutterudite are depends on a Fe/Co ratio of matrix, and the optimal Fe/Co ratio has been reported about from 3:1 to 3.5:0.5 in $R(Fe,Co)_4Sb_{12}$ structure. In this paper, our discussion for rattler doping research was concentrated on double-rattler systems and DD-doped systems in p-type skutterudites. A melt spinning precess combined with high energy ball milling were suggested as a strategy for nanostructured bulk materials with PGEC (phonon glass electron crystal) characteristics in p-type skutterudites.

Impact Damage on Brittle Materials with Small Spheres (I) (취성재료의 소구충돌에 의한 충격손상 (I))

  • U, Su-Chang;Kim, Mun-Saeng;Sin, Hyeong-Seop;Lee, Hyeon-Cheol
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.11
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    • pp.93-100
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    • 2001
  • Brittle materials are very weak for impact because of typical characteristics which happen to be easily fractured with low fracture toughness and crack sensitivity. When brittle materials are subjected to impact due to small spheres, high contact pressure is occurred to impact surface and then local damage on specimen is developed, since there are little plastic deformations due to contact pressure compared to metals. This local damage is a dangerous factor which gives rise to final fracture of structures. In this research, the crack propagation process of soda lime glass by impact of small sphere is explained and the effects of the constraint conditions of impact spheres and materials for the material damage were studied by using soda-lime glass. that is the effects for the materials and sizes of impact ball, thickness of specimen and residual strength. Especially, this research has focused on the damage behavior of ring crack, cone crack and several kinds of cracks.

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Effect of Chemically Etched Surface Microstructure on Tribological Behaviors

  • Hye-Min Kwon;Sung-Jun Lee;Chang-Lae Kim
    • Tribology and Lubricants
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    • v.40 no.3
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    • pp.84-90
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    • 2024
  • This study investigates the effect of the surface microstructure on the tribological characteristics of glass substrates. Chemical etching using hydrofluoric acid and ammonium hydrogen fluoride was employed to create controlled asperity structures on glass surfaces. By varying the etching time from 10 to 50 min, different surface morphologies were obtained and characterized using optical microscopy, surface roughness measurements, and water contact angle analysis. Friction tests were performed using a stainless steel ball as the counter surface to evaluate the tribological behavior of the etched specimens. The results showed that the specimen etched for 20 min exhibited the lowest and most stable friction coefficient, which was attributed to the formation of a uniform and dense asperity structure that effectively reduced the stress concentration and wear at the contact interface. In contrast, specimens etched for shorter (10 min) or longer (30-50 min) durations displayed higher friction coefficients and accelerated wear owing to nonuniform asperity structures that led to local stress concentration. Optical microscopy of the wear tracks further confirmed the superior wear resistance of the 20-minute etched specimen. These findings highlight the importance of optimizing the etching process parameters to achieve the desired surface morphology for enhanced tribological performance, suggesting the potential of chemical etching as a surface modification technique for various materials in tribological applications.

Comparison of metal wire reinforcement and glass fiber reinforcement in repaired maxillary complete denture (상악 총의치 정중 파절 수리 시 금속선 및 유리섬유의 보강효과 비교)

  • Lee, Jung-Ie;Jo, Jae-Young;Yun, Mi-Jung;Jeon, Young-Chan;Jeong, Chang-Mo;Huh, Jung-Bo
    • The Journal of Korean Academy of Prosthodontics
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    • v.51 no.4
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    • pp.284-291
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    • 2013
  • Purpose: This study compared fracture strength and fracture modes between metal wire reinforcement and glass fiber reinforcement in repaired maxillary complete denture. Materials and methods: In this study, fracture was reproduced on center of maxillary complete dentures and the denture was repaired with auto-polymerizing resin. The experimental groups (n = 10) were subjected to the following condition: without reinforcing material (control group), reinforcing with metal wire (W group), reinforcing with glass fiber pre-impregnated with light-curing resin (SES MESH, INNO Dental Co., Yeoncheon, Korea, G group). The fracture strength and fracture modes of a maxillary complete denture were tested using Instron test machine (Instron Co., Canton, MA, USA) at a 5.0 mm/min crosshead speed. The flexure load was applied to center of denture with a 20 mm diameter ball attachment. When fracture occurred, the fracture mode was classified based on fracture lines. The Kruskal-wallis test and the Mann-whitney U test were performed to identify statistical differences at ${\alpha}=.05$. Results: W group showed the highest value of fracture strength, there was no significant difference (P>.05) between control group and G group. Control group and W group showed anteroposterior fracture mainly, group W showed adhesive fracture of denture base and reinforcing material. Conclusion: In limitation of this study, the glass fiber did not improve the fracture strength of repaired maxillary complete denture, and adhesive failure was occurred along the lines of glass fiber.

Effect of Fiber Orientation on the Friction and Wear Properties of Epoxy-based Composites (섬유 방향에 따른 에폭시 기반 복합재의 마찰 및 마모 특성에 관한 연구)

  • An, Hyo-Seong;Khadem, Mahdi;Chun, Heoung-Jae;Kim, Dae-Eun
    • Tribology and Lubricants
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    • v.36 no.3
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    • pp.133-138
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    • 2020
  • In this paper, we present an experimental investigation of the friction coefficient and wear area change of carbon/epoxy and E-glass/epoxy composites depending on the fiber direction (0°/90°). We compared the results of the case where the sliding direction is parallel to the fiber direction (0°) with that of the case where it is perpendicular to the fiber direction (90°). The ball-on-plate wear test equipment was used to cause wear in both directions. Two types of specimens were prepared with thicknesses of 3 mm-one made of carbon fiber reinforced plastic composite (CFRP) and the other of glass fiber reinforced plastic composite (GFRP). A normal force of 20 N was applied to the specimen and the sliding speed was 10 mm/s and the sliding distance was set to 20 m to perform the wear test. The CFRP demonstrates superior tribological characteristics compared to the GFRP. This outcome is attributed to graphitization of carbon, which serves as solid lubricating particles. In addition, both CFRP and GFRP are worn more in the 90° direction than in the 0° direction. This is due to the greater occurrence of fiber breakage and separation in the 90° direction than in the 0° direction. This study is expected to be utilized as basic data for understanding the friction and wear characteristics of CFRP and GFRP composites along the fiber direction and to apply the appropriate material.