• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.150-154
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• 2016

Method for synthesizing a $K_2Ti_6O_{13}$ whisker is a solid-state method, hydrothermal synthesis method, calcination method, flux method, slow-cooling method, melting method, kneading-drying-calcination method, sol-gel method etc. $K_2Ti_6O_{13}$ whisker have been synthesized by a flux method. The average size and distribution of the synthesized $K_2Ti_6O_{13}$ whisker can be controlled by a kind of potassium precursors and reaction temperature and time. The average size of the synthesized $K_2Ti_6O_{13}$ whisker was about in the size range of 500 nm to $2{\mu}m$. The effect of synthesis parameters, such as the molar ratio of KOH to $TiO_2$, pH, reaction temperature and time, are discussed. The synthesized $K_2Ti_6O_{13}$ whisker were characterized by x-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.9-17
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• 2017

$K_2Ti_6O_{13}$ whisker have been synthesized by hydrothermal process at low temperature and pressure condition. The average length of the synthesized $K_2Ti_6O_{13}$ whisker was about in the range of 300 nm to $1.5{\mu}m$. The average diameter of the synthesized $K_2Ti_6O_{13}$ whisker was 15 nm to 60 nm. The aspect ratio of the synthesized $K_2Ti_6O_{13}$ whisker was below 12. The average length and diameter of the synthesized $K_2Ti_6O_{13}$ whisker can be controlled by reaction temperature and time, KOH molar ratio. $K_2Ti_6O_{13}$ whisker was synthesized from more than $210^{\circ}C$ and 4 h at reaction temperature and time. The length of the whisker is increased with increasing reaction temperature. Characterization of the synthesized $K_2Ti_6O_{13}$ whisker was carried out using the XRD and FE-SEM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.261-268
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• 1995

In transforming $K_2Ti_4O_9$ whisker, synthesized by calcination and slow cooling method, into $K_2Ti_6O_{13}$ whisker with boiling water and hydrochrolic acid, the effect of their treatment time and concentration on phase transformation, surface state and scattering of whisker was examined. The result was that the surface state of whisker was improved and whisker with a small diameter and a considerable aspect ratio was obtained by inducing scattering of a bundle of whisker. The treatment by boiling water and hydrochrolic acid induced the phase transformation of $K_2Ti_4O_9$ into $K_2Ti_6O_{13}$ and the phase transformation proceeded by extration of $K^+$ ion.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.585-590
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• 1998

Fibrous $Na_xTi_nO_{2n+1}$ whisker was prepared by $H^+/Na^+$ ion-exchange on layered hydrous titanium dioxide ($H_2Ti_4O_9{\cdot}nH_2O$). The ion-exchange reaction was proceeded at 0.5~2.0 M NaOH solution. In the ion-exchange at 2.0 M NaOH solution, 73% of sodium was exchanged and the prepared $Na_xTi_nO_{2n+1}$ whisker was a fibrous crystal of about $10{\sim}20{\mu}m$ of length and about $0.7{\mu}m$ of diameter. The phase transition of the ion-exchange phases identified by the thermal analysis. The result showed that the $Na_xTi_nO_{2n+1}$ whisker was decomposed into $Na_2Ti_6O_{13}$ and $TiO_2$ in the temperature of $200{\sim}600^{\circ}C$.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1174-1180
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• 1996

Potassium hexatitanate whisker was effectively prepared with calcination and flux method by using industrial $TiO_2$, $K_2CO_3$ and $K_2MoO_4$ as the starting materials. When it was synthesized by the calcination method, the filtrate after boiling water treatment was required a neutralization, as the pH of filtrate was higher than 9. Because K component was very small, recovery of K component was not economically suitable. In case of flux method, flux was recovered 96.1% of Mo component and 91.8% of K component at $K_2MoO_4$, for 10th treatment in boiling water of 100ml to 10g.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1197-1202
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• 2002

In order to develope the porous $K_2Ti_6O_13$ whisker preform with good strength, the pore characteristics and compressive strength were investigated as a function of spark plasma sintering temperature. As a result, high porous whisker preform were successfully fabricated by sintering at 900∼950${\circ}C$ for 10 min under a pressure of 40 MPa, heating rate of 50${\circ}C$/min and on-off pulse type of 12:2. The whisker preform prepared under above optimum condition showed relatively high compressive strength of 174∼266 MPa, despite of high porosity ranging from 15% to 37%. This improvement in strength was considered to be mainly due to the spark-plasma discharges and the self-heating action between whiskers. The compressive strength of whisker preform, fabricated at sintering temperature less than 900${\circ}C$, showed 80∼100 MPa. This is low strength level less than one half times compared with whisker preform fabricated at 900∼950${\circ}C$. The whisker preform fabricated at 1000${\circ}C$ showed the highest compressive strength of 523 MPa, but resulted in low porosity of ∼5%. Based on above results, it was considered that spark plasma sintering was an effective method for developing high strength and porosity of whisker preform.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.160-175
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• 1994

Fibrous potassium hexatitanate whisker with the size of $ID=0.5{\sim}1{\mu}m$ and length=$100{\sim}1000{\mu}m$ (aspect ratio=100~1000) was produced through the reaction between titanium dioxide and potassium carbonate using the slow-cooling calcination followed by water leaching treatment. The optimum condition for the production of fibrous potassium titanate was calcination temperature of $1100^{\circ}C$ for 5hrs, $TiO_2$ mole ratlo to $K_2CO_3$ of 4.5 and slow-cooling rate of $0.5^{\circ}C/min$ to $860^{\circ}C$. Fibrous crystal are grown by the association between the solid potassium titanate and liquid phase during the slow-cooling process. The Proper water leaching condition for removing of K component was leaching time of 10hrs in boiling water. Pressurizing of the mixture of $K_2CO_3$ and $TiO_2$ to be calcinated became effective on the growth of fibrous crystal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.338-343
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• 2015

Dye sensitized solar cells (DSSCs), which is one of the contending renewable energy sources, have the problem of low efficiency. To improve the efficiency, the fast electron transport and long electron lifetime are required. In this study, one-dimensional sodium hexatitanate, which is expected to have an advantageous structure for electron transports, was synthesized and the feasibility of the material on DSSC was tested. Its physical properties were characterized by the SEM, XRD, and BET method. The dye adsorption and solar cell properties were also characterized. In addition to the expectation of fast electron transport, sodium hexatitanate showed longer electron lifetime: This means sodium hexatitanate can improve the DSSC efficiency. However, it showed low current and voltage because of the low surface area leading to the low amount of dye adsorbed. Therefore, it should be mixed with titanium oxide with high surface area for the optimal performance.