• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.35 no.5
• /
• pp.431-438
• /
• 2022

In functional materials, in situ experimental techniques as a function of external stimulus (e.g., electric field, magnetic field, light, etc.) or changes in ambient environments (e.g., temperature, humidity, pressure, etc.) are highly essential for analyzing how the physical properties of target materials are activated/evolved by the given stimulation. In particular, in situ electric-field-dependent X-ray diffraction (XRD) measurements have been extensively utilized for understanding the underlying mechanisms of the emerging electromechanical responses to external electric field in various ferroelectric, piezoelectric, and electrostrictive materials. This tutorial article briefly introduces basic principles/key concepts of in situ electric-field-dependent XRD analysis using a lab-scale XRD machine. We anticipate that the in situ XRD method provides a practical tool to systematically identify/monitor a structural modification of various electromechanical materials driven by applying an external electric field.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.05a
• /
• pp.210-210
• /
• 2012

본 연구에서는 터치패널에 적용되는 ITO 박막의 $SnO_2$ 함량별(2, 3, 5, 10wt%) 특성을 확보하기 위하여, Sputtering 장치를 사용하여 ITO 박막을 상온에서 증착한 후 In-situ HT(High temperature)-XRD를 이용하여 온도에 따른 구조적 특성변화를 조사하였다. In-situ HT-XRD 측정 시 온도는 170, 200, $250^{\circ}C$, 유지시간은 1시간으로 제어하였다.

• Polymer(Korea)
• /
• v.29 no.1
• /
• pp.87-90
• /
• 2005

In this study, we have examined the exfoliation behavior of layered clay during in-situ polymeriztion with styrene by using real-time XRD analysis. The 4C1 beam line at the Pohang Accelerator Laboratory (PAL) was used for this study. Different exfoliation behaviors have been shown to depend on the cation exchange capacity (CEC) of clay and the chemical structure of organic modifiers. For 10A-MMT and 15A-MMT having high CEC, no peak shifts were observed on real-time XRD analysis during polymerization. However, 2$\theta$ for 25A-MMT and VDAC-MMT, each having low CEC’s as well as aromatic benzene moieties and vinyl groups, respectively, decreased as polymerization time increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.12
• /
• pp.1032-1038
• /
• 2000

Ni$_{81}$$Fe_{19}$(200 nm) thin films have been deposited by RF-magnetron sputtering on Si(001) substrates, Atomic force microscopy(AFM), X-ray diffraction(XRD) and magnetoresistance(MR) measurements of the thin films for investigating electromagnetic properties and microstructures were employed. During field annelaing for 1hr, there was no big difference n XRD patterns of Ni$_{81}$$Fe_{19}$ thin films. However, there was a significant change in XRD patterns of Ni$_{81}$$Fe_{19}$ thin films deposited at 40$0^{\circ}C$ during in-situ magnetic field deposition. The degree of surface roughness increased with increasing annealing and deposition temperature. With variation of surface roughness, there was no significant difference in MR Characteristics of Ni$_{18}$ $Fe_{19}$ thin films in 1hr-annealed case. High MR ratio was observed in the case of in-situ field deposited Ni$_{81}$$Fe_{19}$ films. 19/ films.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.25 no.5
• /
• pp.225-229
• /
• 2015

This study was performed to investigate crystal structure of cubic spinel-type monophase oxide composed of the Mn-Co-Ni ternary system. Starting material was prepared by mixing Mn, Co, Ni oxides then evaporation to dryness. The XRD patterns were analyzed by in-situ XRD as increasing temperature from room temperature to $1400^{\circ}C$ in air atmosphere. The cubic spinel phase was existed in a temperature range from $900^{\circ}C$. However, separation of NiO phase was detected from $1300^{\circ}C$, which was the origin of deterioration in the crytallinity. The surface morphology of the manufactured NTC thermistors were analyzed by FE-SEM for comparison of good and bad samples.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
• /
• 2001.06a
• /
• pp.1288-1288
• /
• 2001

X-ray powder diffraction (XRD) is utilized for determination of polymorphism in crystalline organic materials. Though convenient to use in a laboratory setting, XRD is not easily adapted to in situ monitoring of synthetic chemical production applications. Near-Infrared spectroscopy (NIR) can be adapted to in situ manufacturing schemes by use of a source/detector probe. Conversely, NIR is unable to conclusively define the existence of polymorphism in crystalline materials. By combining the two techniques, a novel simultaneous NIR/XRD instrument has been developed. During material's analysis, results from XRD allow for defining the polymorphic phase present, and NIR data are collected as a fingerprint for each of the observed polymorphs. These NIR fingerprints will allow for the development of a library, which can be referenced during the use of a NIR probe in manufacturing settings.

• 한국전기화학회:학술대회논문집
• /
• 2003.04a
• /
• pp.22-22
• /
• 2003

• Korean Journal of Materials Research
• /
• v.14 no.5
• /
• pp.305-309
• /
• 2004

Mechanical alloying (MA) of Ti-25.0～37.5at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-25.0～26.1at%Si powders showed that there were no peaks during MA, indicating $Ti_{5}$ $Si_3$ was synthesised by a slow reaction of solid state diffusion. Those of Ti-27.1～37.5at%Si powders, however, showed that there were exothermic peaks during MA, indicating $_Ti{5}$ $Si_3$ and$ Ti_3$Si phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). For Ti-27.1～37.5at%Si powders, the critical milling times for SHS decreased from 38.1 to 18.5 min and the temperature rise, ΔT (= peak temperature - onset temperature) increased form $19.5^{\circ}C$ to $26.7^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 27.1at% and the critical value of the negative heat of formation of Ti-27.1at%Si to be -1.32 kJ/g.

• Korean Journal of Materials Research
• /
• v.14 no.5
• /
• pp.310-314
• /
• 2004

Mechanical alloying (MA) of Ti-50.0～66.7at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-50.0～59.6at%Si powders showed that there were exothermic peaks during MA, indicating TiSi, $TiS_2$, and $Ti_{5}$ $Si_4$ phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). Those of Ti-59.8～66.7 at%Si powders, however, showed that there were no peaks during MA, indicating any Ti silicide was not synthesised until MA 240 min. For Ti-50.0～59.6at%Si powders, the critical milling times for SHS increased from 34.5 min to 89.5 min and the temperature rise, $\Delta$T (=peak temperature-onset temperature) decreased form $26.2^{\circ}C$ to $17.1^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 59.6at% and the critical value of the negative heat of formation of Ti-59.6at%Si to be -1.48 kJ/g.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.5-5
• /
• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.