This study examined the effects of micro- (crystallinity) and macro (orientation)-crystalline properties of graphite on the initial efficiency, discharge capacity, and rate performance of anodic materials. Needle coke and regular coke were selected as raw materials and pulverized to 2–25 μm to determine the effects of crystalline properties on particle shape after pulverization. Needle coke with outstanding crystallinity had high initial efficiency, and smaller particles with larger specific surface areas saw increased irreversible capacity due to the formation of SEI layers. Because of cavities existing between crystals, the poorer the crystalline properties were, the greater the capacity of the lithium ions increased. As such, regular coke had a 30 mAh/g higher discharge capacity than that of needle coke. Rate performance was more affected by particle size than by crystalline structure, and was the highest at a particle distribution of 10–15 μm.

The (Ga1-xZnx)(N1-xOx) solid solution is attracting extensive attention for photocatalytic water splitting and wastewater treatment owing to its narrow and controllable band gap. To optimize the photocatalytic performance of the solid solution, the key points are to decrease its band gap and recombination rate. In this study, (Ga1-xZnx)(N1-xOx) nanofibers with various Zn fractions are prepared by electrospinning followed by calcination and nitridation. The effect of the composition and crystallinity of electrospun oxide nanofibers on the morphology and optical properties of the obtained solid-solution nanofibers are systematically investigated. The results show that the final shape of the (Ga1-xZnx) (N1-xOx) material is greatly affected by the crystallinity of the oxide nanofibers before nitridation. The photocatalytic properties of (Ga1-xZnx)(N1-xOx) with different Ga:Zn atomic ratios are investigated by studying the degradation of rhodamine B under visible light irradiation.

In the present study, vanadium oxide(V2O5) films for electrochromic(EC) application are fabricated using sol-gel spin coating method. In order to optimize the EC performance of the V2O5 films, we adjust the amounts of polyvinylpyrrolidone(PVP) added to the solution at 0, 5, 10, and 15 wt%. Due to the effect of added PVP on the V2O5 films, the obtained films show increases of film thickness and crystallinity. Compared to other samples, optimum weight percent(10 wt%) of PVP led to superior EC performance with transmittance modulation(45.43 %), responding speeds(6.0 s at colored state and 6.2 s at bleached state), and coloration efficiency(29.8 cm2/C). This performance improvement can be mainly attributed to the enhanced electrical conductivity and electrochemical activity due to the increased crystallinity and thickness of the V2O5 films. Therefore, V2O5 films fabricated with optimized amount of PVP can be a promising EC material for high-performance EC devices.

Milled carbon fiber (mCF) was prepared by a ball milling process, and X-ray diffraction (XRD) diffractograms were obtained by a 2θ continuous scanning analysis to study mCF crystallinity as a function of milling time. The raw material for the mCF was polyacrylonitrile- based carbon fiber (T700). As the milling time increased, the mean particle size of the mCF consistently decreased, reaching 1.826 μm at a milling time of 18 h. The XRD analysis showed that, as the milling time increased, the fraction of the crystalline carbon decreased, while the fraction of the amorphous carbon increased. The (002) peak became asymmetric before and after milling as the left side of the peak showed an increasingly gentle slope. For analysis, the asymmetric (002) peak was deconvoluted into two peaks, less-developed crystalline carbon (LDCC) and more-developed crystalline carbon. In both peaks, Lc decreased and d002 increased, but no significant change was observed after 6 h of milling time. In addition, the fraction of LDCC increased. As the milling continued, the mCF became more amorphous, possibly due to damage to the crystal lattices by the milling.

ZnO film was prepared on a p-type Si wafer and then annealed at various temperatures in air and vacuum conditions to research the electrical properties and bonding structures during the annealing processes. ZnO film annealed in atmosphere formed a crystal structure owing to the suppression of oxygen vacancies: however, ZnO annealed in vacuum had an amorphous structure after annealing because of the increment of the content of oxygen vacancies. Schottky contact was observed for the ZnO annealed in an air. O 1s spectra with amorphous structure was found to have a value of 529 eV; that with a crystal structure was found to have a value of 531.5 eV. However, it was observed in these results that the correlation between the electronic characteristics and the bonding structures was weak.

본 실험에서는 폴리프로필렌를 이용하여 중공사의 형태로 제조되었다. 권취속도를 달리하여 중공사막을 제조하였으며, 코어로는 질소를 사용하였다. 제조된 중공사는 만능재료시험기를 이용하여 응력과 변현율을 측정하였다. 그리고 시차 주사열량계(DSC)를 이용하여 각각의 샘플의 결정화도를 측정하였고, 권취속도와 어닐링 효과에 따른 결정화도의 거동을 조사하였다. 냉연신과 열연신을 거친 중 공사 분리막은 전계방출형주사현미경(FE-SEM)을 이용하여 단면, 표면의 모폴로지를 관찰 하였다.

Silicoaluminophosphate (SAPO-34) zeolite membranes (pore diameter of 0.38nm) have shown high tendency in separation of light gas mixtures. In this work, SAPO-34 membranes were synthesized under various conditions such as different seed, the composition of coating gel and temperature. Membranes prepared by secondary growth method were analyzed using SEM and XRD for the morphology; and gas properties which were tested using a homemade single gas testing apparatus. The crystallinity was improved by the addition of dipropyl amine as an additional structure directing agent (SDA) and also the membrane show nitrogen selectivity in response. Nitrogen selective membranes show a high gas permeance (above 2000 GPU) and low selectivity (max 2.25).

High crystallinity coke-based activated carbon (hc-AC) is prepared using a potassium hydroxide solution to adsorb carbon dioxide (CO2). The CO2 adsorption characteristics of the prepared hc-AC are investigated at different temperatures. The X-ray diffraction patterns indicate that pitch-based cokes prepared under high temperature and pressure have a high crystal structure. The textural properties of hc-AC indicate that it consists mainly of slit-like pores. Compared to other textural forms of AC that have higher pore volumes, this slit-poreshaped hc-AC exhibits higher CO2 adsorption due to the similar shape between its pores and CO2 molecules. Additionally, in these high-crystallinity cokes, the main factor affecting CO2 adsorption at lower temperature is the pore structure, whereas the presence of oxygen functional groups on the surface has a greater impact on CO2 adsorption at higher temperature.

Carbon-based electric double-layer capacitors are being evaluated as potential energy-storage devices in an expanding number of applications. In this study, samples of carbon black (CB) treated at different temperatures ranging from 650℃ to 1100℃ were used as electrodes to improve the efficiency of a capacitor. The surface properties of the heat-treated CB samples were characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The effect of the heat-treatment temperature on the electrochemical behaviors was investigated by cyclic voltammetry and in galvanostatic charge-discharge experiments. The experimental results showed that the crystallinity of the CBs increased as the heat-treatment temperature increased. In addition, the specific capacitance of the CBs was found to increase with the increase in the heat-treatment temperature. The maximum specific capacitance was 165 F·g-1 for the CB sample treated at 1000℃.

We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.

Hydroxyapatite (HAp) powders with different crystallinities were synthesized at various calcination temperatures through the co-precipitation of Ca(OH)2 and H3PO4. The degradation behavior of these HAp powders with different crystallinities was assessed in a simulated body fluid solution (SBF) for 8 weeks. Below 800˚C, the powders were nonstochiometric HAp, and the single HAp phase was successfully synthesized at 800˚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.

본 논문은 용액법으로 성장시킨 저밀도 폴리에틸렌 박막의 냉각 조건에 따른 결정화도의 관계와 냉각 조건에 따른 전기전도현상, 유전특성 및 절연파괴에 관하 연구로서 박막은 140[˚C]에서 2시간 유지후 냉각 조건을 달리하여 제작하였다. 결정화도는 XRD를 이용하여 측정하였으며 냉각 속도가 빠를수록 결정화도가 감소함을 볼 수 있었다. 전기전도현상은 냉각 조건에 무관하게 저전계에서는 이온전도특성이 나타나고 고전계에서는 공간전하제한전류이론이 지배적이다. 절연파괴전계는 냉각속도가 증가할수록 증가하고 self-healing절연파괴 방법에서는 시험회수가 증가할수록 증가하였다.

비정질 PEEK필름의 self-bonding공정시 조건 변화에 따르는 결정화도(crystallinlty)변화가 self-bonding강도에 미치는 영향을 고찰하기 위하여, 비정질 PEEK필름을 그 2차천이온도(Tg=143˚C)와 용융점(Tm=335˚C) 사이의 여러 온도에서 일정 압력 하에서 접합 시간을 달리하여 self-bonding시킨 후, 각 조건에서 개발된 self-bonding강도를 측정하고, 이에 따르는 결정화도 변화를 DSC를 이용하여 비교 분석하였다. 결정화도는 접합공정변수(시간과 온도)의 함수로서 증가하였고, 동일한 값의 결정화도를 보이는 시편들의 경우에도 접합공정의 조건에 따라 결과적인 self-bonding강도는 큰 차이가 있음을 보였다. 또한 접합후 시편을 상온으로 노냉시키는 동안에는 더 이상의 결정화 현상이 일어나지 않음이 DSC분석을 통하여 판명되었다.

BST 박막을 Pt/SiO2/Si 기판위에 co-sputtering 방법으로 형성할 때 열처리 조건이 BST 박막의 결정성과 전기적 특성에 미치는 영향에 관하여 연구하였다. BST 박막의 특성은 급속 열처리나 관상로 열처리과 같은 후열처리 온도보다 증착시의 기판온도에 따라서 민감하게 변화하였고, 기판 온도를 550˚C로 하여 증착할대 Perovskite상이 가장 안정적으로 성장하여 유전율 1100, 유전손실계수 0.02로 우수한 유전특성을 나타내는 막을 형성할 수 있었다. BST 박막은 기판온도를 증가하면 정합에너지와 표면에너지를 최소로하는 (111) 방향으로 우선방위를 나타내었고 결정립의 조대화 현상으로 누설전류가 증가하였다.

비정질 SiO2위에서 증착시킨 Si1-xGex합금의 증착온도에 따른 결정성, 미세구조와 조성의 균일성을 X선 회절법과 투과 전자현미겨으로 조사하였고, Si1-xGex/Sio2계면을 고분해능 투과 전자현미경을 이용하여 원자단위로 관찰하였다. Ge의 몰분율을 0.3으로 놓고 증착온도를 300˚C,400˚C,500˚C,600˚C,700˚C로 변화시키며 Si-MBE로 증착된 박막은 , 분석 결과 300˚C에서는 비정질상만이 존재하였고 400˚C에서는 결정상과 비정질상이 공존하고 있었다. 두상은 SiO2위에 함께 증착되었으나 초기 성장에서는 비정질상이 주로 성장되었으며 박막의 두께가 비정질층이 관찰되었다. 600˚C이상에서는 결정상으로만 증착되었다. 증착된 다결정상은 주상성장을 하였다. 증착된 박막의 조성은 중착온도에 관계없이 균일하였으며, Si1-xGex/Sio2계면은 다결정상이나 비정질상에 관계없이 평탄하였다.