• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.51-53
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• 1999

The crystallization mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied from the relations between crystallization and volume changes by dilatometry. Further, the effect of addition of CdO on the crystallization mechanism and superconductivity was discussed. The shrinkage of the amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ occurred with the crystallization of $Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase decrease with increasing CdO content with a minimum at x=0.4. Better superconductivity was obtained in the specimens formation less amount of the$Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase during the crystallization process.

• 한국군사과학기술학회지
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• 제16권3호
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• pp.358-364
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• 2013

Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of $80.4SiO_2-4.2Na_2O-2.4Al_2O_3-13.0B_2O_3$. The 2-step crystallization was performed around $584^{\circ}C$ of glass transition temperature ($T_g$), and $774^{\circ}C$ of crystallization temperature($T_c$). The maximum nucleation rate was $8.8{\time}10^9/mm^3{\cdot}hr$ at $600^{\circ}C$ and the maximum crystal growth rate was 3.5nm/min at $750^{\circ}C$. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, $752kg/mm^2$, $1.082MPa{\cdot}mm^{1/2}$. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.

• 한국미생물·생명공학회지
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• 제42권3호
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• pp.297-301
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• 2014

본 연구에서는 실리카겔을 이용한 반응액 부피당 표면적(surface area per volume of reaction solution)이 증가된 반코마이신 결정화 공정에서 이온성 액체의 영향을 조사하였다. 실리카겔로 표면적을 증가시킨 경우에 이온성 액체([BMIm][$BF_4$])를 접목하면 결정화 효율을 더욱 향상시킬 수 있었다. 실리카겔을 이용한 표면적이 증가된 결정화에서 이온성 액체(20%, v/v)를 첨가한 경우 결정화 4시간에 반코마이신 결정이 생성되었으며 실리카겔과 이온성 액체를 사용하지 않은 경우보다 결정화에 소요되는 시간을 6배 정도 단축시킬 수 있었다. 또한 이온성 액체 첨가량이 증가함에 따라 반코마이신 결정 입자크기가 감소할 뿐만 아니라 결정이 균일하고 일정해짐을 알 수 있었다.

• 한국세라믹학회지
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• 제23권4호
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• pp.1-10
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• 1986

The crystallization behaviour and the machinability of mica glass-ceramics with the content of F1 were studied. The material was made from the $K_2O-MgO-Al_2O_3-B_2O_3-SiO_2-F$ glasses by the heattreatment at 80$0^{\circ}C$-110$0^{\circ}C$ where the content of F-1 was changed in the range from 1, 3wt% to 6.1wt%. X-ray diffraction phase analysis and optical observation were adopted to study the crystallization behaviour. The machinability was measured by a manual sawing test and MOR. The crystal phases of these glass-ceramics identified by XRD were chondrodite fluoborite and norbergite at low temperature but fluorophlogopite at high temperature. The crystallization of glasses containing 1.3wt% -2.5wt% F-1 were predominately controlled by surface crystallization while the crystallization of glasses containing 3.8 wt% -6.1wt% F-1 were controlled by volume crystallization. Among the test the best machinability and strength value were obtained from those specimens contained fluoride 4.2wt% -4.4wt% and when the heattreatment was performed at 95$0^{\circ}C$-110$0^{\circ}C$ for 2 hours.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2369-2376
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• 2011

Effect of heat treatment of carbon nanofibers (CNF) on electrical properties and crystallization behavior of polypropylene was reported. Two types of CNFs (untreated and heat treated at 2300 $^{\circ}C$) were incorporated into polypropylene (PP) using intensive mixing. A significant drop in volume resistivity was observed with composites containing untreated 5 wt % and heat treated 3 wt % CNF. In non-isothermal crystallization studies, both untreated and heat treated CNFs acted as nucleating agents. Composites with heat treated CNFs showed a higher crystallization temperature than composites with untreated CNFs did. TEM results of CNF revealed that an irregular structure of CNFs can be converted into the continuous graphitic structure after heat treatment. Furthermore, STM showed that the higher carbonization temperature leads to the higher graphite degree which presents the larger carbon network size, suggesting that a more graphitic structure of CNFs led to a higher crystallization temperature of PP.

• 한국미생물·생명공학회지
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• 제42권3호
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• pp.232-237
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• 2014

본 연구에서는 반응액 부피당 표면적(surface area per volume of reaction solution)이 증가된 반코마이신 결정화 공정에서 표면적 증가물질인 실리카겔의 영향을 조사하였다. 표면적 증가물질로 실리카겔을 사용한 경우, 반코마이신 결정화 시간 단축 측면에서 표면적 증가물질인 실리카겔의 기공지름은 $40-60{\AA}$, 입자크기 230-400 mesh 범위가 적절함을 알 수 있었다. 또한 실리카겔의 첨가량이 증가 할수록 반코마이신의 결정 크기가 감소함을 확인할 수 있었다. 실리카겔을 표면적 증가물질로 사용함으로써 표면적 증가물질이 없을 때 보다 결정화에 소요되는 시간을 4배 정도 단축시킬 수 있었다. 이러한 개선된 결정화 방법은 반코마이신 정제 효율 향상에 상당히 기여할 것으로 판단된다.

• 공업화학
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• 제29권6호
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• pp.799-804
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• 2018

결정화조작에 의해 접촉분해경유(LCO) 유분 중에 함유된 2,6-디메틸나프탈렌(2,6-DMN)의 분리 정제를 검토했다. LCO 유분을 원료로, 이소프로필알코올을 결정화 용매로 각각 사용하여 solute crystallization (SC)을 수행했다. 결정화 조작온도의 상승과 용매/원료의 체적비(S/F)의 증가는 2,6-DMN의 순도를 향상시켰으나, 역으로 수율의 저하를 초래시켰다. LCO 유분(13.9% 2,6-DMN)과 이소프로필알코올을 사용한 SC, SC에 의해 회수한 결정과 메틸아세테이트를 사용한 re-crystallization 1 (RC 1), RC 1에 의해 회수한 결정과 메틸아세테이트를 사용한 RC 2의 3단계로 결정화조작을 행한 결과, 19.5%의 수율로 99.9% 2,6-DMN의 결정을 회수할 수 있었다. SC, RC 1, RC 2의 각 조작을 통해 얻어진 실험적 결과를 이용하여 LCO 유분 중에 함유된 2-6-DMN의 분리 정제공정을 검토했다.

• Korea-Australia Rheology Journal
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• 제12권2호
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• pp.101-105
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• 2000

The crystallization behavior of homo polypropylene (PP) and PP in the PP-poly($\varepsilon$-caprolactone) (PCL) blends during isothermal crystallization has been investigated using differential scanning calorimeter (DSC) and advanced rheometric expansion system (ARES). From the storage modulus data of the homo PP and PP-PCL blends during isothermal crystallization, the volume fraction of crystallized material ($X_t$) of the homo PP and PP in the PP-PCL blends was calculated using the various rheological models. The results of $X_t$ of the homo PP and PP in the PP-PCL blends from ARES measurement were compared with the results from DSC. The $X_t$ of the homo PP was found to be higher in the ARES measurement than in the DSC. The crystallization rate of the homo PP was found to be faster in the rheological measurements than in the thermal analysis. The $X_t$ of PP in the PP-PCL blends with various compositions was obtained from the thermal analysis and rheological measurements. The $X_t$ of PP in the PP-PCL blends obtained from the thermal analysis and rheological measurements are not consistent. This discrepancy of $X_t$ may be due to the morphological changes resulted from the different crystallization kinetics of PP in the PP-PCL blends.

• 한국세라믹학회지
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• 제33권8호
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• pp.855-862
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• 1996

The nucleation and the crystal growth rates of Ge-Se-Te chalcogenide glass by two step heat-treatment and its effect on the mechanical optical properties and water-resistance were determined. The maximum nuclea-tion and crystal growth rate were 2.1$\times$103/mm3 .min at 28$0^{\circ}C$ and 0.4${\mu}{\textrm}{m}$/min at 33$0^{\circ}C$ respectively. When the crystal volume fraction with crystal size $1.5mutextrm{m}$ was about 4% the (hardness and fracture toughness were about 117kg/mm2 and 6.0 MPa.mm1/2)respectively. The weight loss of crystallized glass in water was lower than parent glass($25^{\circ}C$ for 32 hrs : 0.03% 8$0^{\circ}C$ for 16 hrs : 0.1%) as 0.01% at $25^{\circ}C$, 0.03% at 8$0^{\circ}C$ for 16 hrs : 0.1%) at $25^{\circ}C$ 0.03% at 8$0^{\circ}C$ respectively. The IR-transmittance decreased with increasing crystal size and crystal volume fraction. The IR-transmittance of crystallized glass with the crystal size of $1.5mutextrm{m}$ (crystal volume fraction : 4%) presented 56% which was about 4% lower than that of parent glass.

• 한국세라믹학회지
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• 제29권12호
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• pp.956-962
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• 1992

The predominant sintering mechanisms of low firing temperature ceramic substrate which consists of borosilicate glass containing alumina as a filler are the rearrangement of alumina particles and the viscous flow of glass powders. In this system, sintering condition depends on the volume ratio of alumina to glass and on the particle size. When the substrate contains about 35 vol% alumina filler and the average alumina particle size is 4 $\mu\textrm{m}$, the best firing condition is obtained at the temperature range of 900∼1000$^{\circ}C$. The extensive rearrangement behavior occurs at these conditions, and the optimum sintering condition is attained by smaller size of glass particles, too. The formation of cristobalite during sintering causes the difference of thermal expansion coefficient between the substrate and Si chip. This phenomenon degradates the capacity of Si chip. Therefore, the crystallization should be prevented. In the alumina filled borosilicate glass system, the crystallization does not occur. This effect may have some relation with aluminum ions in alumina. For aluminum ions diffuse into glass matrix during sintering, functiong as network former.