• Title, Summary, Keyword: relative crystallinity

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Gamma-Irradiated Ultra-high Molecular Weight Polyethylene : Anisotropic Changes in Crystallinity and Crosslinking

  • Lee, Kwon-Yong
    • Journal of Biomedical Engineering Research
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    • v.18 no.2
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    • pp.107-112
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    • 1997
  • The effect of gamma-irradiation sterilization on molecular structural changes in orthopaedic surgical-grade polyethylene was studied. The relative crystallinity ud. percent crosslinking of the substance increased as a result of the gamma irradiation and varied anisotropically as a function of depth. Samples from the articulating surfaces showed 5% Venter relative crystallinity than those from the mid-sections, whereas samples from the mid-sections exhibited 15% greater crosslinking than those from the surfaces. These anisotropic variations are discussed in assDciation with oxidation.

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Variation of Crystalline State in a Stem of Chamaecyparis obtusa E. (편백(Chamaecyparis obtusa E.) 수간내에서의 결정상태의 변이성)

  • Kim, Nam-Hun;Lee, Ki-Yeong
    • Journal of the Korean Wood Science and Technology
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    • v.26 no.4
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    • pp.20-25
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    • 1998
  • Radial variation of crystalline state in a stem of Chamaecyparis obtusa E. was examined by x-ray diffraction analyses. Relative crystallinity and degree of crystallite orientation showed significant differences between juvenile and adult wood. That is, Relative crystallinity increased with increasing the age from pith to about 20th annual ring, after which it reached a more or less constant value. On the other hand, degree of crystallite orientation decreased outward from pith to about 10 years and presented almost a constant value thereafter. Crystal width by Scherrer's equation did not show any significant differences between juvenile and adult wood. Therefore, it was considered that crystallinity index and degree of crystallite orientation by x-ray diffraction method could be used for evaluating wood quality.

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Variation of Fine Structure of Wood Cellulose within Stems of 3 Commercial Softwood Species Grown in Korea (국내산 주요 침엽수 3종간의 수간 내 목재셀룰로오스의 미세구조 변이)

  • Eun, Dong-Jin;Kwon, Sung-Min;Kim, Nam-Hun
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.1
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    • pp.12-20
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    • 2008
  • Radial and vertical variations of relative crystallinity and crystallite width of cellulose within stems of three softwoods (Pinus densiflora S. et Z., P. koraiensis S. et Z, P. rigida Mill.) grown in Korea were examined by an X-ray diffraction method. The mean of relative crystallinity was 61.7% in P. koraiensis, 60.6% in P. densiflora and 49.4% in P. rigida. The degree of crystallinity in earlywood and latewood increased with the age from pith to about 10~15 years, and then remained almost constant value. The relative crystallinitiy of latewood was slightly higher than that of earlywood. The relative crystallinity in P. densiflora was a little lower at the base of stem, but no significant difference by height was shown in P. koraiensis and P. rigida. The crystallite widths in the stems were 2.8 to 3.0 nm, but were not significantly different in earlywood and latewood by height. In conclusion, the relative crystallinity appeared to be a useful index for separating juvenile wood from adult wood in the softwoods of P. densiflora, P. koraiensis, and P. rigida grown in Korea.

Studies on the Fundamental Properties of the Wood of Gumgangsong(Pinus densoflora for. erecta Uyeki) (Part 1) (강송의 기초적 재질에 관한 연구(제1보))

  • 김정환;이원희;홍선천
    • Journal of the Korea Furniture Society
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    • v.10 no.2
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    • pp.55-61
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    • 1999
  • This research was carried out to investigate the fundamental properties such as the structure of annual ring, density distribution, compressive strength with parallel to grain, relative crystallinity, and microfibril angle of Gumgangsong(Pinus densoflora for. erecta Uyeki). The wood specimens, Gumgangsong and Sonamu(Pinus densiflora S. et Z.), for this experiment were prepared at Ulijingoon Sokwangri and Kyungpook university's forest in Kyungpook province, respectively. Average annual ring width is $2.0mm{\pm}0.3$ in heartwood of Gumgangsong. The respectively of heart wood was over 60 percent in Gumgangsong and 20~50 percent in Sonamu. Heartwood density were ranged from 0.5 to $0.8{\;}g/cm^3$ in Gumgangsong and from 0.4 to $0.5{\;}g/cm^3$ in sonamu. Compressive strength in Gumgangsong and Sonamu was about $30{\pm}5MPa$ and $25{\pm}5MPa$, resepectively. But the relative crystallinity and microfibril angle of two species were not different clearly. From these results of Gumgangsong and Sonamu, therefore, it was considered the main difference factors for both species were annual ring width and heartwood percentage.

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Microstructural Changes in Orthopaedic-Grade Ultra High Molecular Weight Polyethylene (UHMWPE) according to Gamma-Irradiation Method (감마선 조사 방법에 따른 정형외과용 초고분자량 폴리에틸렌의 미세구조 변화)

  • Lee, Kwon-Yong
    • Polymer(Korea)
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    • v.34 no.5
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    • pp.454-458
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    • 2010
  • In this study, the microstructural changes in orthopaedic-grade ultra high molecular weight polyethylene (UHMWPE) were compartively investigated for six different gamma-irradiation methods. Compared with un-irradiation (UGI), conventional gamma-irradiation in air room temperature (AR) induced statistically significant increases of relative crystallinity and percent crosslinking in UHMWPE. Vacuum environment (VR) during gamma-irradiation significantly increased the percent crosslinking in UHMWPE. Vacuum extreme low temperature (V77) during gamma-irradiation induced no significant changes in both relative crystallinity and percent crosslinking of UHMWPE but the percent crosslinking of UHMWPE in VR and V77 was significantly larger than that in AR. Post-irradiation stabilization process significantly increased the relative crystallinity of UHMWPE in V77, and it also significantly increased the percent crosslinking of UHMWPE in AR and V77.

Thermal Properties and Crystallization Behaviors of Poly(ethylene terephthalate) at Various Annealing Conditions (열처리 조건에 따른 폴리(에틸렌 테레프탈레이트)의 열적 특성 및 결정화 거동)

  • 류민영;배유리
    • Polymer(Korea)
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    • v.27 no.2
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    • pp.113-119
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    • 2003
  • The thermal properties and crystallization behaviors of poly(ethylene terephthalate) (PET) were investigated by controlling the annealing conditions of PET sample, such as relative humidity, temperature, and time. The variations of moisture content, glass transition temperature ($T_g$) and cold crystallization temperature ($T_{\propto}$) were examined after annealing the PET sample. Subsequently crystallization process was performed with the annealed PET specimen, and then the degree of crystallinity and heat distortion temperature (HDT) of variously crystallized PET specimen were examined. Residual stress relaxation in the injection molded PET sample after annealing was also observed through polarized films. Moisture content in the PET specimen increased up to 6000 ppm with increasing the relative humidity, temperature, and time of annealing. $T_g$ and $T_{\propto}$ of the annealed PET specimen decreased with increasing moisture content. The degree of crystallinity increased as increasing moisture content in the PET specimen. However for same moisture content, the degree of crystallinity varied with annealing conditions. The relaxations of residual stress in the PET sample differed from annealing conditions, and the maximum degree of crystallinity increased with decreasing residual stress in the PET sample.

Characterization of PECVD and LPCVD a-Si films crystallized by excimer laser (엑시머 레이저를 이용하여 결정화한 PECVD 및 LPCVD 비정질 실리콘 박막의 특성 분석)

  • 최홍석;이성규;장근호;전명철;한민구
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.6
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    • pp.172-177
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    • 1996
  • We have characterized XeCl excimer-laser-induced crystallization of thin amorphous silicon films deposited by PECVD (${\alpha}$-Si:H) and LPCVD (${\alpha}$-Si). The electrical properties, surface roughness and crystallinity of crystallized thin films have been measured. The dc conductivities, crystallinity andsurface roughness of the films increased as the laser energy density and shot density were increased. The properties of laser annealed films deposited by LPCVD were better than those of thin films deposite by PECVD. We have also found that the multiple shots with relative low energy density were more benifical to the improsvement of surface roughness than the single shot with high energy density preserving the crystallinity.

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MWPCVD에 의해 합성된 다이아몬드 박막 특성에 대한 증착조건의 영향

  • 이병수;박상현;신태현;유도현;이덕출
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.97-97
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    • 2000
  • In this thesis, the metastable state diamond thin films have been deposited on Si substrates from methane-hydrogen and oxygen mixture using Microwave Plasma Enhanced Chemical Vapor deposition (MWPCVD) method. Effects of each experimental parameters of MWPCVD including methane concentrations, oxygen additions, operating pressure, deposition time, etc. on the growth rate and crystallinity were investigated. SEM, XRD, and Raman spectroscopy were employed to analyze the growth rate and morphology, crystallinity and prefered growth direction, and relative amounts of diamond and non-diamond phases respectively. As a methane concentration below 4%, the deposited films having well-defined facets could be obtained. As the methane concentration increases over 4%, the shape of films gradually changed into a amorphos form. The best crystallinity of the film at 3% in the Raman spectroscopy. Addition of oxygen to the methane-hydrogen mixture gave an improved film crystallinity at 50% oxygen concentration due to its more effectiveness in the selective removal of the non-diamond phased compared to the of H atom. on the contrary, the growth rate generally decreased by oxygen to from the more stable CO and CO2 is responsible for such an effect. Upon increasing the operating pressure and time, increased of growth rate and crystallinity were increased simultaneously.

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Effect of deposition on the properties of diamond thin films synthesized by Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD에 의해 합성된 다이아몬드 박막 특성에 대한 증착조건의 영향)

  • Lee, Byoung-Soo;Lee, Duch-Chool
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.51 no.1
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    • pp.33-38
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    • 2002
  • In this study, the metastable state diamond thin films have been deposited on Si substrates from methane-hydrogen and oxygen mixture using microwave plasma enhanced chemical vapor deposition (MPCVD) method. Effects in experimental parameters of MPCVD including methane concentrations, oxygen additions, operating pressure, deposition time on the growth rate and crystallinity were investigated. Diamond thin film was synthesized under the following conditions: methane concentration of 0.5%(0.5sccm)~5%(5sccm), oxygen concentration of 0~80%(2.4sccm), operating pressure of 30Torr~70Torr, deposition time of 1~32hr. SEM, XRD, and Raman spectroscopy were employed to analyze the growth rate and morphology, crystallinity and prefered growth direction, and relative amounts of diamond and non-diamond phases, respectively.

Electrical and Electromagnetic Shielding Properties of Polyaniline Films with Different Degrees of Crosslinking (교차결합의 변화에 따른 Polyaniline 필름의 전기적 성질과 전자기차폐 성질에 관한 연구)

  • 김재욱
    • Electrical & Electronic Materials
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    • v.10 no.1
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    • pp.54-60
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    • 1997
  • The electrical and electromagnetic shielding properties have been investigated in polyaniline free standing films with different degrees of elongation cast from N-methyl 2-pyrrolidone(NMP) solution and camphorsulfonic acid(HCSA) doped polyaniline film. The degree of crystallinity of the crosslinked films increased with increasing the draw ratio. For the case of the oriented films doped with hydrochloric acid, we have the values of conductivities up to 173 S/cm. It is considered that the physical micro-crystalline crosslinking domains act as nucleation sites for the increase of relative crystallinity during stretching. We have obtained the value of conductivity 210 S/cm in the HCSA doped polyaniline film cast from the solvent of m-cresol, which is higher than that of the crosslinking oriented films. The electromagnetic shielding efficiency of HCSA doped polyaniline film obtained 37-41 dB in the frequency range of 10MHz-1GHlz, which is higher than that of the crosslinking oriented films. The higher value of electromagnetic shielding efficiency of HCSA doped polyaniline film suggests strong possibility of electromagnetic shielding material.

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