• 한국세라믹학회지
• /
• 제21권3호
• /
• pp.271-277
• /
• 1984

To study interface between crystals grown and molten state in the crusible. Pulling and rotating rate of the shaft were varied in LiF crystal growth by Czochralski method. Lower speed of the pulling and rotating rate increased the degree of convexity in solid-liquid interface and higher speed of the pulling and rotating rate decreased it. Optimum condition of LiF crystal growth obtained as pulling rate was 6.5cm/h when it rotated as 46rpm.

• 한국결정학회지
• /
• 제11권3호
• /
• pp.157-161
• /
• 2000

In a 200nm Cz-Si crystal, a macroscopic fluctuation in pulling rate was intentionally introduced an then the variations of the pulling rate and the position of OSF-ring were compared each other. The formation behavior of OSF-ring in the effective volume, defined as the region between the growth interface position -α and the growth interface position +α, is most affected by the pulling rate fluctuation. To understand the correct effect of a macroscopic pulling rate fluctuation, its cumulative effect in the effective volume should be considered. A new concept of modeling for it was proposed here.

• 한국결정학회지
• /
• 제2권2호
• /
• pp.32-40
• /
• 1991

The effects of compositional variation, rotation speel and pulling rate on the growth of optical quality Bi120e02(1 crystals were examined. It was found to flatten the shape of crystal-melt interface for yowing a single crystals less than about 30mm in diameter at the rotation speed of 50rpm. Diameter of crystals with flat interface was increased as the pulling rate. The precipitation of Bi40e3012 phase set limits to pulling rate of BGO crystals. Precipitate-free BGO crystals were grown under pulling rate of 2mm l hr which released the stress resulted from too hi어 Pulling rate, and from 6. IBi203·GeO2 batch composition obtained by addition of 0.1 mole Bi203 into Bi-deficient melts to fill up the deficiency resulted from gradual volatilization of Bi2O). The pale-yellow colored crystals had good quality in that dislocation density was less than 103pits/cm, and it also exhibited transmittance of 70% and optical activity of 23°/mm. and SAW velosity was measured 1700m/sec on 111 cut 110 propagating BGO crystals. The SAW filter with electrode thickness of 9.8um was fabricated by using the electron beam and dry etching technique, it makes Bi12GeO20 devices intersting for color TV IF with half device size.

• 한국결정학회지
• /
• 제11권4호
• /
• pp.200-206
• /
• 2000

In a 200 mm Cz-Si crystal, a macroscopic fluctuation in pulling rate was intentionally introduced then the variations of the pulling rate and the formation behaviors of grow-in defects were compared. The diameters of the OSF-ring and the FPD area were affected by the fluctuation in the region above 1100℃. The COP density depended on the diameter of the OSF-ring. ΔOi and BMD were affected by the fluctuation in the region near 1000Δ. As the result, when a macroscopic fluctuation in pulling rate is introduced, the quality of crystal in the region of 150 mm from the growth interface should be reviewed carefully because it can be affected by the fluctuation.

• 한국결정성장학회지
• /
• 제10권5호
• /
• pp.345-349
• /
• 2000

Micro-pulling down법을 이용하여 $Al_2O_3/ZrO_2$eutectic fiber를 제조하여 그 미세구조 및 기계적 특성과 성장속도의 관계를 조사하였다. 성장속도는 0.1~15 mm/min였으며, 직경 0.2~2 mm, 길이 500 mm의 eutectic fiber를 제조하였다. $Al_2O_3/ZrO_2$eutectic fiber의 미세구조는 성장속도에 따라 rod-shape structure에서 lameller structure를 거쳐 lamellar pattern을 갖는 cellular structure로 변화하였다. lamellar thickness는 성장속도가 1 mm/min에서 15 mm/min로 증가함에 따라 380 nm에서 110 nm로 감소하였다. 이와 같은 성장속도에 따른 lamellar thickness의 감소경향은 inverse-square-root로 나타내면, = 1 -l/2와 같이 표현할 수 있다. 여기서 는 m, 는 m/s의 단위를 갖는다. 13.1 Gpa의 hardness, 900 Mpa의 상온인장강도를 나타냈으며, 성장속도의 증가 즉, interlamellar spacing이 감소함에 따라 증가하는 경향을 나타냈다.

• 한국치위생학회지
• /
• 제20권6호
• /
• pp.973-980
• /
• 2020

Objectives: This study was to analyz the effects of comparative evaluation of the effects of oil pulling on periodontal indices. Methods: A total subjects were 38; control group (19 subjects) and experimental group (19 subjects). In the experimental group, coconut oil was provided and rinsed the mouth for about 10 minutes once a day. We evaluated possession rate of pocket depth (≥4 mm), possession rate of bleeding on exploring and possession rate of gingival recession (≥1 mm). Results: The possession rate of pocket depth (≥4 mm), bleeding on exploring and gingival recession (≥1 mm) significant difference in interaction between the group and measurement time. Conclusions: The findings of this study indicate that dental hygiene process and oil pulling specialists in care of periodontal diseases were effective mediation.

• 대한기계학회논문집
• /
• 제19권5호
• /
• pp.1308-1318
• /
• 1995

The influence of varying rotation speed of both crystal and crucible was numerically investigated for the Czochralski silicon-crystal growth. Based on a simplified model assuming flatness of free surfrae, the Navier-Stokes Boussinesq equations were employed to identify the flow pattern, temperature distribution as well as the shape of the melt/crystal interface. The present results showed that the interface shape was relatively convex with respect to the melt at lower pulling rate and tended to be concave as the pulling rate increased. In particular, the experimentally observed gull-winged shape of the interface was qualitatively in agreement with the predicted shape. The rotation of crystal alone little affected the growth system. When the rotation speed of the crucible was increased, there occurred inversion of the interface shape from convex to concave pattern. At rapid rotation of the crucible, an interesting channel formation was predictied primarily due to the assumption of laminar flow.

• Korean Chemical Engineering Research
• /
• 제58권3호
• /
• pp.369-380
• /
• 2020

대부분의 단결정 실리콘 잉곳은 초크랄스키(Czochralski(Cz)) 공정으로 제조된다. 그러나 단결정 실리콘 잉곳을 제품화 및 태양 전지 기판으로 가공하였을 때 산소 불순물이 있는 경우 낮은 효율성을 나타내는 경향이 있다. 단결정 Si-잉곳의 생산을 위해서는 용융 Si를 녹인 다음 단결정 Si의 시드(Seed)로 결정화하는 초크랄스키(Cz) 공정을 도입한다. 용융된 다결정 Si-덩어리를 단결정 Si-잉곳으로 결정성장 될 때, 열 전달은 Cz-공정의 구조에서 중요한 역할을 한다. 본 연구에서 고품질 단결정 실리콘 잉곳을 얻기 위해 Cz-공정의 최적화된 설계를 구성하였다. 결정 성장 시뮬레이션로부터 결정성장을 위한 Pulling rate 및 Rotation speed에 최적의 변수값을 형성하기 위해 사용되었으며, 변형된 Cz-공정에 대한 연구 및 해당 결과가 논의되며 결정 성장 시뮬레이션을 사용하여 Cz-공정의 Pulling rate, Rotation speed 및 Melt charge level의 최적화된 설계로 인한 결정성장시 단결정 실리콘으로 유입되는 산소 농도 최소화를 설계하였다.

• 한국결정성장학회지
• /
• 제2권1호
• /
• pp.43-50
• /
• 1992

인상속도를 변수로 Czochralski법을 이용하여 $ LiNbO_3$결정들을 성장시켰다. 성장된 단결정에 균열, 기포, 셀 구조 등의 결함들이 관찰되었다. 균열들은 인상속도와 냉각속도에 매우 민감하였는데 6~7mm/h의 인상속도와 20^{circ}C/h의 냉각속도가 직경 15mm정도의 결정성장에 적당한 조건임을 알 수 있었다. 소자응용에 필요한 유전적 성질 및 광학적 성질 등을 알아보기 위하여 a축, c축방향에 따라 절삭된 시편을 온도를 변화시켜가며 측정하였다.

• 한국치위생학회지
• /
• 제19권3호
• /
• pp.375-385
• /
• 2019

Objectives: The purpose of this study was to provide basic data for gingivitis management programs by dental hygienists by evaluating the effect of oral health education, oil pulling, and professional toothbrushing on gingivitis. Methods: A total of 38 subjects were divided into three groups: control group (12 subjects), experimental group 1 (13 subjects), and experimental group 2 (13 subjects). The control and experimental groups were instructed to brush using the rotating method. Distilled water was provided to the control group after training. Coconut oil was provided every morning for about 10 minutes. In the experimental group 2, a professional brushing method was used at each visit. Results: There were no significant differences in oral health among the three groups, and there was homology between patient hygiene performance (PHP) index (p=0.144) and bleeding rate (p=0.213). The PHP index showed a significant interaction between the group and measurement time. The control and experimental groups showed changes in the PHP index with time (F=3.711; p=0.013). The bleeding rate showed a significant interaction between the group and measurement period. The control and experimental groups showed changes in the bleeding rate with time (F=6.707; p<0.001). Conclusions: Oral health education, professional toothbrushing, and oil pulling specialists in oral care of gingivitis were effective in managing gingivitis. It is necessary to educate people on self-management methods for oral health promotion using gingivitis management programs by dental hygienists.