• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.466-467
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• 2006

The anatase particle was facetted at the free surface and a neck formation between the anatase particles prior to the phase transformation occured. This resulted in the severe lattice distortion at the region of the interface near the neck and this can act as the nucleation sites for the phase transformation. The grain growth of rutile particles after the phase transformation grew very fast by the sweeping phenomena of grain boundary. Therfore, It leaded to the microstructure without the rutile phase located in anatase particle.

• 한국결정성장학회지
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• 제31권4호
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• pp.166-173
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• 2021

TiO₂의 rutile 상은 anatase 상에 비해서 고온에서 안정한 상을 형성하지만 anatase의 안정한 온도 영역은 합성조건에 따라 변화된다. 본 연구에서는 TiOSO₄와 에탄올과 증류수의 혼합용매를 사용하여 Sol-gel법으로 나노 사이즈의 TiO₂를 합성하여 pH 및 열처리 온도를 따른 anatase와 rutile의 상변화에 대하여 조사하였다. 제조한 TiO₂의 pH(3, 5, 7, 9)와 열처리 온도(500, 600, 700, 800, 900℃) 조건을 변화시켜 anatase와 rutile의 비율 변화를 관찰하였다. XRD, FE-SEM 분석을 통해 이와 같은 변화를 관찰한 결과, 500℃에서는 anatase TiO₂, 900℃에서는 rutile TiO₂가 관찰되었다. 이 중간 온도인 600, 700, 800℃에서는 pH에 따라 anatase와 rutile의 비율이 변화한다. 700℃를 기준으로 pH = 3, 5는 anatase TiO₂의 비율이 더 크고, pH = 7, 9는 rutile TiO₂의 비율이 더 크다는 결론을 얻었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.111-111
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• 2003

The peroxo titanic acid solution was successfully prepared using titanium trichloride as a precursor. The basic properties of the TiO2 film prepared by the solution were investigated in view of phase change, bandgap energy, crystalline size etc. The film displayed amorphous TiO$_2$ at room temperature, anatase above 281$^{\circ}C$ and a mixture of anatase and rutile at 99$0^{\circ}C$, The crystalline size increases with annealing temperatures, while the bandgap energies decrease due to the quantum size effect and the formation of rutile phase which has low bandgap energy. As a result of TG-DTA, it was found that annealing treatment at 99$0^{\circ}C$ for 2h formed a mixtures of anatase and rutile through three steps: (1) the removal of physically adsorbed water (2) the decomposition of peroxo group (3) amorphous-anatase or anatase-rutile phase transformation.

• Composites Research
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• 제31권6호
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• pp.365-370
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• 2018

One of the critical parameters to improve the output power for triboelectric nanogenerators (TENGs) is the surface charge density. In this work, we modify the tribo-material of TENG by introducing the $TiO_x$ embedded Polydimethylsiloxane (PDMS) in anatase and rutile phase. The effect of dielectric constant and electronic structure of the $TiO_x$ on the capacitance of TENG and the output power as well are discussed. The surface charge density is increased as the control of the dielectric constant in difference weight percent of $TiO_x$ and PDMS. As the results of that, the 5% $TiO_x$ rutile phase and 7% $TiO_x$ anatase phase embedded PDMS exhibit the highest TENG output. The peak value of voltage/current obtained from $TiO_x$ rutile and anatase phase are ${\sim}180V/8.2{\mu}A$ and $211.6V/8.7{\mu}A$, respectively, at the external force of 5 N and working frequency of 5 Hz, which gives over 12-fold and 15-fold power enhancement compared with the TENG based on the pristine PDMS film. This study provides a better understanding for TENG performance enhancement from the materials view.

• 한국결정학회지
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• 제12권3호
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• pp.177-181
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• 2001

TiO₂박막의 초친수성 특성을 열처리에 따른 박막의 결정구조 변화와 연관지어 연구하였다. 박막은 Sol-Gel법을 이용하여 실리콘 (100)웨이퍼 위에 제조하였다. 1차 소결후, 500℃에서 후열처리한 시편은 anatase 상을, 1000℃에서 열처리한 시편은 rutile 상을 가지며 그 중판 온도인 750℃에서 열처리한 경우는 anatase와 rutile상이 혼재 되어 있다. 이 후열 처리한 시편들은 UV를조사하지 않아도 친수성을 보였고, 특히 750℃에서 열처리한 시편은 5°이하의 초친수성을나타내었다. 친수성을 가지는 시편들은 암실처리 중 서서히 퇴화되어 소수성을 띄게되지만, UV를 조사하면 1시간 이내에 급격히 초진수성을 회복하는 우수한 특성을 보였다.

• 한국재료학회지
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• 제12권10호
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• pp.809-813
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• 2002

Commercial nano crystalline $TiO_2$ powders were used to characterize photocatalyst, using thermal spray coating technique. The microstructure of coating layers were examined by SEM, FE-SEM and TEM. Also the cross sectional areas of TiO$_2$ coating layers were observed by SEM. The phases were analyzed by X-ray diffraction methed. Surface roughness and hardness were measured. It was found that phase transformation from anatase to rutile occurred, and the melted splats are all rutile, and unmeted nano particles were anatase. These unmelted anatase phase may enhance te play a role of photocatalyst.

• 한국세라믹학회지
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• 제49권5호
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• pp.469-474
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• 2012

The crystallinity and phase ratio of anatase to rutile in $TiO_2$ were estimated by x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS). Traditionally, the structural characterization of $TiO_2$ powders has been carried out by XRD techniques, which are comparatively easy in use and analysis. However, materials with amorphous phase, nano-sized or nano-structured crystallinities cannot be fully characterized by XRD because XRD analysis has a limit for abnormal contributions of the nano-crystal such as the surface contribution. From the comparison with the experimental and calculated Ti K-edge XAS spectra, we found the possibility of efficient estimation in the crystalinites and the phase ratio of anatase to rutile for nano-sized $TiO_2$ mixture.

• International Journal of Oral Biology
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• 제46권3호
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• pp.105-110
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• 2021

The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO₂ NPs) were investigated by comparing amorphous (amTiO₂), anatase (aTiO₂), metaphase of anatase-rutile (arTiO₂), and rutile (rTiO₂) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO₂ had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600-3,100 cm^-1 decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UV-Vis) spectra, the maximum absorbance of anatase TiO₂ NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO₂ NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO₂ > arTiO₂ > rTiO₂. Overall, the phases of TiO₂ NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.

• Korean Chemical Engineering Research
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• 제56권2호
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• pp.261-268
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• 2018

본 연구에서는 수열합성법과 주형합성법을 이용하여 메조포어를 지닌 $TiO_2$를 합성하였다. 수열합성법을 이용해서 anatase 구조의 메조포러스 $TiO_2$를 합성했다. Rutile 구조의 메조포러스 $TiO_2$를 제조하기 위해서 수열합성법으로 제조된 메조포러스 $TiO_2$를 $300^{\circ}C$부터 $700^{\circ}C$까지 소성시켰더니 $600^{\circ}C$부터 anatase에서 rutile 결정구조로 상전이가 일어났다. 하지만, 메조포어가 붕괴되었다. 메조포어을 지닌 $TiO_2$를 합성하기 위해서 메조포러스 실리카 KIT-6을 주형으로 사용하는 주형합성법을 사용하였다. 먼저 메조포어 내부에 $TiO_2$를 형성시키고 소성온도를 800, $900^{\circ}C$로 높여서 anatase에서 rutile로의 상전이 거동을 조사하였다. 수열합성을 통해 제조된 자유로운 상태의 메조포러스 $TiO_2$의 경우 $600^{\circ}C$에서 anatase에서 rutile로의 상전이가 일어났지만 제한된 공간인 메조포러스 기공 내부에 형성된 $TiO_2$의 경우 $800^{\circ}C$까지 가열하더라도 rutile구조로 상전이가 일어나지 않았고, $900^{\circ}C$로 소성시키자 일부의 anatase가 rutile로의 상전이가 일어나기 시작하였다. 이러한 상전이는 산소 빈자리의 형성에 의해서 일어나야 한다고 알려져 있지만 실리카 기공 내부에 형성된 $TiO_2$는 실리카 기공 표면이 산소 빈자리 형성을 방해해서 상전이가 억제되는 것으로 판단된다. $900^{\circ}C$의 높은 소성온도로 인해서 anatase와 rutile 구조가 섞여있으며 실리카 기공 내부에 형성된 $TiO_2$는 NaOH 수용액을 이용해서 주형인 KIT-6과 분리해서 메조포어를 지닌 $TiO_2$를 제조하였다.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.640-643
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• 1997

Pure titanium dioxide $(TiO_2)$ films were prepared by pulsed laser deposition on a single crystal Si(100) substrate. We have investigated the growth of crystalline titanium dioxide films with respect to substrate temperature and ambient oxygen pressure. The structural properties of the films were analyzed by X-ray diffraction. We found that the anatase as well as the rutile phases could be formed from the original rutile phase of the target $TiO_2$. At 0.75 torr of ambient oxygen pressure, the structure of $TiO_2$ film was amorphous at room temperature, anatase between 300 and 600 ℃, a mixture of anatase and rutile between 700 and 800 ℃, and only rutile at 900 ℃ and above. However, at a low ambient oxygen pressure, the rutile phase became dominant; the only rutile phase was obtained at the ambient oxygen pressure of 0.01 torr and the substrate temperature of 800 ℃. Therefore, the film structures were largely influenced by substrate temperature and ambient oxygen pressure.