• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.163-164
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• 2006

A QM-ISP-4 Planetary Mill was employed to activate mechanically the mixtures of anatase and corundum at room temperature for different times. The milled powder mixtures were then sintered at $1300^{\circ}C$ for 1 h. The XRD results showed that the milled powder mixtures were completely transformed into $Al_2TiO_5$ after sintering, except the mixtures milled for 5 and 10 hours. The SEM observations showed the typical morphology of rod-like $Al_2TiO_5$ vary in the range: widths from 0.6 to $1.2\;{\mu}m$, and lengths from 3.0 to $6.0\;{\mu}m$. The rod-like $Al_2TiO_5$ formation was attributed to the positive effects caused by the mechanical activation.

• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.560-574
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• 1997

The present study was undertaken to investigate the crystal growth onto human enamel mineral and synthetic hydroxyapatite(HA) seeds in media resembling the enamel fluid composition. Effects of fluoride at high concentrations on the precipitation were also examined in a bench-top crystal growth model adopting a miniaturized reaction column. The Ca, P and F concentrations and pH values of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated during the experimental period, and finally viewed under a scanning electron microscope. Remarkable findings were that 1) both biological and synthetic seeds with the same total surface areas yielded similar amounts of crystal growth, 2) the amount of crystal growth was accelerated in a manner depending on fluoride concentrations in the media, 3) SEM observations disclosed that without the addition of fluoride, precipitation of thin, plate-like OCP crystals became prominent, but by increasing the fluoride concentration(beyond 1ppm F), rod-like crystals having a pointed edge were most frequently observed, without any evidence for precipitation of the plate-like crystals. Furthermore, the dimension of rod-like crystals was increased in proportion to fluoride concentrations, 4) there was no difference in the morphological feature of precipitated mineral phase upon seeding between human enamel seed and synthetic HA seed. The overall results support the view that the seeded crystal growth model is of value to gain insight into the mechanism of enamel crystal growth under fluoride regimens.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.271-272
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• 2009

We fabricated a hybrid aligned film using reactive rod-like mesogen to reduce light leakage of twisted nematic(TN) cell in off-axis of the dark state. We proved that the fabricated compensation film has hybrid alignment by changing phase retardation according to polar angle. In this paper, we confirmed characteristics of compensation film through simulation results and found the matching factor of simulation results and experimental result. In result, the maximum pretilt angle of hybrid compensated film is $19^{\circ}$ which has phase retardation 0.1445.

• 대한화학회지
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• 제52권2호
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• pp.164-168
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• 2008

마이크로 에멀젼 방법으로 CaWO4 결정을 합성하였다. CTAB에 대한 H2O의 몰랄 농도비(w)를 변 화시켜서 다양한 크기와 형태의 CaWO4를 얻었다. w=5와 w=10일 때 각각 100 nm와 500 nm 길이의 타원형 CaWO4 결정을 얻었다. w=20일 때는 1 μm의 막대형 CaWO4 결정을 얻었다. w=30에서는 길이가 약 2~3 μm인 구형의 CaWO4 결정을 얻었다. CTAB에 대한 H2O의 몰랄 농도비가 증가 할수록 응집에 의해서 CaWO4 결정 의 모양은 타원형에서 막대형태를 거쳐서 구형으로 변했다.

• 한국결정성장학회지
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• 제11권5호
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• pp.203-206
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• 2001

The applicability of shaped growth of yttrium orthovanadate was approved by successful growth of rod-like single crystals with the rectangular shape. Nd-doped single crystals with content of $Nd^{3+}$ ions of 1,2,3,5 atomic % in the starting melt were grown by the EFG technique with the size up to $10^{*}10mm$ in section and up to 85 mm in length. For the testing of the multiple growth of the orthovanadates, two and three Nd-and Yb-doped $YVO_{4}$ single crystals were grown by the EFG technique simultaneously up to 110 mm in length.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.390-391
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• 2007

We have studied improvement of light leakage of twisted nematic liquid crystal display (TN-LCD) in dark state using the hybrid aligned compensation film made of rod-like LC. When the voltage is applied properly to the TN-LCD, the director tilts up but LC director on the substrate don't tilts up due to surface anchoring energy of the LC cell. Accordingly, LC director from surface to middle LC of TN -LCD become hybrid state such as hybrid aligned film. Consequently, in this paper we achieve wide viewing angle performances of TN mode using developed hybrid aligned film which especially decreases light leakage at vertical direction in dark state.

• 한국결정성장학회지
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• 제8권2호
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• pp.324-331
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• 1998

2, 5, 10 mol% YAG(yttrium aluminum garnet) 분말을 액상 소결조제로 $\alpha$상 탄화규소 분말에 첨가한 후 $1850^{\circ}C$에서 소결시간을 달리하여 소결체를 제조한 다음, 소결시 일어나는 미세구조 변화를 첨가된 액상량과 소결시간의 변화에 대하여 고찰하였다. 각 조성중 2시간 소결한 시편에서 가장 높은 밀도를 나타냈으며, 소결시간이 길수록 액상의 기화로 인하여 중량감소량이 점차 증가하였다. 또한 첨가된 YAG 액상량이 증가할 수록 상대밀도(apparent density)와 중량감소량은 증가하였으나 입성장속도는 감소하였다. 액상량이 적은 시편에서는 소결시간이 길수록 일부 6H상의 탄화규소 입자가 4H상 탄화규소 입자로 상전이 되었으며, 이로 인하여 막대상 입자들이 일부 존재하였다.

• 한국결정성장학회지
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• 제12권3호
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• pp.126-132
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• 2002

$ZrOCl_2{\cdot}8H_2O$ 수용액과 KOH 수용액의 반응으로부터 얻은 침전물을 $100^{\circ}C$에서 24 시간 동안 숙성시켜 정방정상 지르코니아를 제조한 후 수열합성 조건을 변화시킴으로써 비등방성 형상의 나노 결정형 지르코니아 분말을 합성하였다. 수열합성 시 반응온도와 반응시간이 증가할수록 정방정상인 구형 입자는 감소하고 상대적으로 단사정상 spindle-like 입자와 막대상 입자가 증가하였다. NaOH 용액의 농도가 증가함에 따라 입성장과 함께 정방정상에서 단사정상으로의 상전이가 촉진되었으며, 저온에서 반응시간이 짧은 경우 합성한 분말들은 반응초기에 응집된 입자들이 NaOH 용액에 부분적으로 용해되면서 응집입자 및 결정입자 크기가 감소되어 비표면적이 증가하였다가 반응시간이 길어지고 반응온도가 높아짐에 따라 입성장에 의하여 점차 비표면적이 감소하였다.

• 한국결정성장학회지
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• 제12권3호
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• pp.149-156
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• 2002

$Ga_2O_3$ : $Eu^{3+}$ 형광체 분말을 균일침전법에 의해 제조하여 TG/DTA, XRD, FT-IR, SEM 등으로 특성을 분석하였다. 결정질 GaOOH 와 비정질에 가까운 $\gamma$-$Ga_2O_3$ 등 두 종류의 분말이 얻어졌다. 요소 농노가 0.5 M 이하에서는 입자는 막대모양을 이루고, 열처리에 따라 $\alpha$-$Ga_2O_3$을 거쳐서 $\beta$-$Ga_2O_3$상으로 변태하였다. 한편 나노미터 크기를 갖는 $\gamma$-$Ga_2O_3$분말은 1.0 M 이상의 요소 농도에서 생성되며, 직접 $\beta$-$Ga_2O_3$으로 전이하였다. 실온에서 광 발광 특성을 비교한 결과 마이크로미터 크기의 분말에 비해 나노미터 크기의 분말이 610 nm에서의 발광 강도가 더 크게 나타났다.

• 한국재료학회지
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• 제29권7호
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• pp.432-436
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• 2019

Zinc oxide(ZnO) micro/nanocrystals are grown via thermal evaporation of ZnO powder mixed with Mn powder, which is used as a reducing agent. The ZnO/Mn powder mixture produces ZnO micro/nanocrystals with diverse morphologies such as rods, wires, belts, and spherical shapes. Rod-shaped ZnO micro/nanocrystals, which have an average diameter of 360 nm and an average length of about $12{\mu}m$, are fabricated at a temperature as low as $800^{\circ}C$ due to the reducibility of Mn. Wire-and belt-like ZnO micro/nanocrystals with length of $3{\mu}m$ are formed at $900^{\circ}C$ and $1,000^{\circ}C$. When the growth temperature is $1,100^{\circ}C$, spherical shaped ZnO crystals having a diameter of 150 nm are synthesized. X-ray diffraction patterns reveal that ZnO had hexagonal wurtzite crystal structure. A strong ultraviolet emission peak and a weak visible emission band are observed in the cathodoluminescence spectra of the rod- and wire-shaped ZnO crystals, while visible emission is detected for the spherical shaped ZnO crystals.