Improvement of energy storage performance by controlling the crystallinity of Aurivillius BaBi4Ti4O15 thin films

금윤형,Shin Hyun Wook,손종역 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.6

We investigated the crystallinity, ferroelectric properties, and energy storage effi ciency of Aurivillius BaBi 4Ti4O15 (BBTO) thin fi lms epitaxially deposited on single-crystal (001) Rh substrates by pulsed laser deposition method. From X-ray dif- fraction experiments, it was confi rmed that the BBTO thin fi lms had a mixed crystallinity of a-oriented crystallinity and c-oriented crystallinity. The BBTO thin fi lms fabricated by a low substrate temperature and a high deposition rate showed highly a-oriented crystallinity. On the other hand, the BBTO thin fi lms deposited by a high substrate temperature and a low deposition rate showed improved crystallinity with highly c-oriented crystallinity. The BBTO thin fi lm with the highly a-oriented crystallinity showed large remanent polarization, and the BBTO thin fi lm with the highly c-oriented crystallinity showed small remanent polarization but excellent leakage current characteristics. In addition, the BBTO thin fi lm with the highly c-oriented crystallinity exhibited superior energy storage characteristics with a high energy storage density of 32.5 J/cm3 and a high effi ciency of 0.8 compared to the BBTO thin fi lm with the highly a-oriented crystallinity.

Investigation of Mechanical and Hygroscopic Properties for the Semi-crystalline Polypropylene Polymer Via Experiments and Molecular Dynamics

Donghyun Kim,Yeon-Taek Hwang,김학성 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.1

In this study, mechanical properties and moisture related hygroscopic characteristics of semi-crystalline polypropylene (PP) were investigated via molecular dynamics (MD) simulations and experiments with respect to degree of crystallinity. To control the degree of crystallinity, experimental samples were treated by an annealing process while MD models were constructed through combination of crystalline and amorphous layers. In order to evaluate crystal structure and calculate degree of crystallinity for the experimental samples, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) measurements were conducted. For comparison with the experimental samples, an XRD simulation was performed for the MD models. Then, the mechanical and hygroscopic properties such as elastic modulus and moisture saturation amount were studied with respect to the degree of crystallinity through experiment and MD simulation. It was found that the effects of the degree of crystallinity on the hygro-mechanical properties of the semi-crystalline PP can be predicted from the developed MD simulation. It is expected that the simulation approach developed in our study can be widely used to predict the characteristics of the semi-crystalline PP with varying degree of crystallinity.

Crystallinity of silicon/carbon composite materials for rechargeable battery

Jinsuk Lee,Yujeong Ahn,Sihyun Lee 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6

The silicon battery’s uncontrollable volume change during the lithiation process leads to a severely decreased battery life. Despite such a critical drawback of the material, the unparalleled capacity potential of silicon (Si) batteries is what makesit the next generation’s most anticipated battery anode material. The first part of determining the capacity of a Si anodeis the Si core itself. Our research indicated that the higher the purity of Si results in a naturally higher crystallinity status. When the purity of the sample was identical, monocrystalline Si proved to have higher crystallinity than polycrystalline andamorphous. The second part that determines the capacity is the graphite used in the composite. Natural Graphite (NG) havehigher crystallinity values than Artificial Graphite (AG) and show more resistant properties to the crystallinity breakingdown by milling time, which inspected by particle size analyzer, optical transmission and microscope. We reached a millingmethod of getting small particle sizes yet high crystallinity and graphene presence, which expect to improve the robustnessof anode materials and electrochemical performances. The third part that determines coated carbon layers accommodate thevolume change and prevents the quick loss of capacity, indicating higher crystallinity. Finally, the composites prepared withthis method showed that higher X-ray Diffraction (XRD) and Raman Spectroscopy peaks than commercial references. Weconcluded how high crystallinity used in silicon carbon composite materials show high capacity potential with integrity inrechargeable battery.

Determination of Crystallinity of Thermosetting Urea-Formaldehyde Resins Using Deconvolution Method

Eko Setio Wibowo,박병대 한국고분자학회 2020 Macromolecular Research Vol.28 No.6

Current low formaldehyde/urea (F/U) molar ratio urea-formaldehyde (UF) resins are quite different from high molar ratio UF resins used 20 years ago in terms of their crystallinity. For the first time, this paper reports a method of determining the crystallinity of thermosetting urea-formaldehyde (UF) resins of different molar ratios with the deconvolution method, using Voigt, Lorentzian, and Gaussian function. The Gaussian deconvolution of X-ray diffraction (XRD) patterns was the most suitable and reliable curve-fitting method, which gave the crystallinity value from 31.8% to 56.1% as the molar ratio decreased from 1.6 to 1.0. These results also indicated that low-molar-ratio (1.2 and 1.0) UF resins were semi-crystalline, whereas high molar-ratio (1.6 and 1.4) resins were amorphous. The Gaussian function was also employed to determine the crystallinity of the low-molar-ratio (1.0) UF resins cured at different curing and hardener conditions. Hardener level had greater influence on the crystallinity than hardener type even though the curing temperature and time affected the crystallinity.

의사체액에서 수산화아파타이트의 결정성에 따른 분해거동

진형호,김동현,김태완,박홍채,윤석영,Jin, Hyeong-Ho,Kim, Dong-Hyun,Kim, Tae-Wan,Park, Hong-Chae,Yoon, Seog-Young 한국재료학회 2011 한국재료학회지 Vol.21 No.6

Hydroxyapatite (HAp) powders with different crystallinities were synthesized at various calcination temperatures through the co-precipitation of $Ca(OH)_2$ and $H_3PO_4$. The degradation behavior of these HAp powders with different crystallinities was assessed in a simulated body fluid solution (SBF) for 8 weeks. Below $800^{\circ}C$, the powders were nonstochiometric HAp, and the single HAp phase was successfully synthesized at $800^{\circ}C$. The degree of crystallinity of the HAp powders increased with an increasing calcination temperature and varied in a range from 39.6% to 92.5%. In the low crystallinity HAp powders, the Ca and P ion concentrations of the SBF solution increased with an increasing soaking time, which indicated that the low crystallinity HAp degraded in the SBF solution. The mass of the HAp powders linearly decreased with respect to the soaking time, and the mass loss was higher at lower crystallinities. The mass loss ranged from 0.8% to 13.2% after 8 weeks. The crystallinity of the HAp powders increased with an increasing soaking time up to 4 weeks and then decreased because of HAp degradation. The pH of the SBF solution did not change much throughout the course of these experiments. These results suggested that the crystallinity of HAp can be used to control the degradation.

벌크흑연 제조를 위한 결합재로 이용되는 콜타르 핏치 및 페놀수지의 열처리에 의한 결정성 변화

이상민 ( Sang-min Lee ),이현용 ( Hyun-yong Lee ),이상혜 ( Sang-hye Lee ),노재승 ( Jae-seung Roh ) 한국공업화학회 2021 공업화학 Vol.32 No.2

인조흑연 제조용 바인더로 주로 이용되는 콜타르 핏치와 페놀 레진은 soft carbon 및 hard carbon의 초기 탄소화합물구조에 차이가 있다. 따라서 탄화 온도에 따른 열분해 거동, 미세조직, 결정성의 변화 과정도 다를 것으로 예상할 수 있다. 본 연구에서는 콜타르 핏치 및 페놀 레진의 열분해 거동, 미세조직, 결정성 변화에 관하여 비교 분석하였다. 콜타르 핏치는 액상을 경유한 탄화 과정을 거치며, 탄화 온도가 증가함에 따라 미세조직이 점차 변화되는 것을 확인할 수 있었다. 탄화 온도가 증가함에 따라 콜타르 핏치 및 페놀 레진 모두 결정성은 증가하는 경향을 나타냈지만, 콜타르 핏치는 미세조직이 급변하는 500 및 600 ℃ 구간에서 결정성도 급격히 변화는 것을 확인할 수 있었다. 또한 미세조직과 결정성은 서로 밀접한 연관성이 있었다. The coal tar pitch and phenol resins are used as binders in artificial graphite manufacture, but there are differences in the initial carbon compound structure. According to the carbonization temperature, it can be expected that there are differences in thermal decomposition behavior, microstructure, and crystallinity change. These properties of the coal tar pitch and phenol resins were compared to each other. As the carbonization temperature of coal tar pitch and phenol resin increases, crystallinity tends to increase. The coal tar pitch went through the carbonization process through the liquid, and it was confirmed that the crystallinity changed rapidly in the temperature range of 500 and 600 ℃, where the microstructure changed quickly. These results confirmed the close correlation between microstructure and crystallinity.

Prediction of Cellulose Crystallinity in Liquid Phase Using CBM-GFP Probe

Xiaoyu Guo,Fan Yang,Huixue Liu,Yingmin Hou,Yafang Wang,Jie Sun,Xiaoyi Chen,Yanan Liu,Xianzhen Li 한국고분자학회 2019 Macromolecular Research Vol.27 No.4

Carbohydrate-binding modules (CBMs) have been developed to investigate the presence of crystalline and amorphous regions of cellulose. However, systematic and quantitative assessment of cellulose crystallinity using such non-hydrolytic fusion proteins in liquid phase has not been reported. In this work, cellulose directed CBM probes containing a green fluorescent protein (GFP) were constructed and named CG17, CG28, and CG2a. The probe binding condition was determined as incubating 30 μg/mL probes in 10 mM phosphate buffer at 30oC for 60 min. Under the optimized condition, the linear correlations between CBM probe binding capability and X-ray diffraction (XRD) crystallinity were well established. Using linear regression equations, the crystallinity of several cellulosic materials was well calculated. Amorphous component and cellulosic surface area probably had a less effect on binding capability of CG2a than that of CG17 and CG28. Therefore, crystalline-region specific probe CG2a should be an efficient tool for interpreting the crystallinity of cellulosic materials.

Surface Crystallinity of Meltspun Isotactic Polypropylene Filaments

Ali Kilic,Keith Jones,심은경,Behnam Pourdeyhimi 한국고분자학회 2016 Macromolecular Research Vol.24 No.1

In this study, surface crystallinity of meltspun polypropylene (PP) filaments was reported. Results obtained from attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were confirmed with tapping mode atomic force microscopy (TM-AFM) analysis. ATR-FTIR tests were performed directly on longitudinal surfaces of the filaments, where IR radiation penetrates up to a specific depth. TM-AFM measurements were done on microtomed cross-sections of the filaments, which were scanned carefully to investigate stiffness. Annealing enhanced the surface crystallinity of the filaments in a significant way. Interestingly, samples annealed at 70 and 110 oC for 12 h exhibited similar crystallinity on the uppermost 500 nm surface, whereas for the bulk a continuous increase was observed after XRD studies. 12 h annealing at 70 oC modified the endothermic thermogram, while it did not causes significant effect on overall bulk crystallinity. Differences in the behavior of surface and bulk of the fibrous materials should be considered particularly for surface treatment, i.e. plasma, corona discharge, chemical vapor deposition. Results are also pertinent for water and dye absorbency in polymers.

Surface morphology evolution of microcrystalline silicon p-layer prepared by RFPECVD

Seung-Yoon Lee,Seh-won Ahn,Heon-Min Lee 한국물리학회 2010 Current Applied Physics Vol.10 No.2

Surface morphology and crystallinity of silicon p-layer have been investigated on the effect of various deposition conditions of RFPECVD in order to clarify crystalline nuclei evolution. Crystallinity increased with increasing hydrogen dilution, but decreased with increasing both RF input power and diborane doping. Microcrystalline nuclei size increased with increasing working pressure, RF input power and substrate temperature. However, surface morphology was not correlated with crystallinity or deposition rate. A film with relatively large nuclei but having rather low crystallinity can be prepared for some condition,and vice versa. In order to get a dense microcrystalline silicon intrinsic layer subsequently deposited,surface morphology control of microcrystalline p-layer seems to be important as well as crystallinity.

알칼리 처리에 따른 아마섬유의 헤미셀룰로스 제거와 결정구조 전이

엄인철,권해용,박영환,Um, In Chul,Kweon, Hae Yong,Park, Young Hwan 한국섬유공학회 2012 한국섬유공학회지 Vol.49 No.5

In this study, delignified flax fiber was treated with a NaOH aqueous solution. XRD diffractometry and FTIR spectroscopy were utilized to examine the structural transition of the alkali-treated flax fibers. Also, the effect of the hemicellulose removal on the structural change of flax fibers was discussed. XRD measurement revealed that the crystallinity of cellulose I increased at low NaOH concentration (3%) due to the elimination of amorphous hemicellulose. The structural transition from cellulose I to cellulose II occurred in a NaOH concentration range of 12~15%. Considering most hemicellulose in flax fiber is removed at 12% NaOH, it can be assumed that the presence of hemicellulose in flax fiber has a role in preventing the structural change of flax cellulose. IR absorbance ratios ($A_{1370cm}{^{-1}}/A_{2900cm}{^{-1}}$ and $A_{1430cm}{^{-1}}/A_{2900cm}{^{-1}}$) were utilized as a barometer of cellulose I crystalline exhibiting a similar result with the cellulose I crystallinity from XRD. Another absorbance ratio ($A_{895cm}{^{-1}}/A_{2900cm}{^{-1}}$) reflected the cellulose II crystalline showing almost the same trend as cellulose II crystallinity. On the whole, the total crystallinity of flax fiber was increased at low NaOH concentration (3%) and decreased at 12% due to the reduction of cellulose I content and increased again at 15% attributed to the formation of cellulose II content.