Scanning Electron Microscopy Studies of Saccharomyces cerevisiae Structural Changes by High Hydrostatic Pressure Treatment

Woo-Suk Bang,Barry G. Swanson 한국식품과학회 2008 Food Science and Biotechnology Vol.17 No.5

The structural change and leakage of cellular substances of Saccharomyces cerevisiae attributed by high hydrostatic pressure (HHP) treatment were observed with scanning electron microscopy (SEM). S. cerevisiae (ATCC16664) was inoculated in apple juice for 10 min at 23℃ and the apple juice treated at 138, 207, 276, 345, and 414 MPa pressure for 30 sec at 23℃. Increased of roughness, elongation, wrinkling, and pores on yeast cell surfaces, the yeast cell walls were severely damaged by HHP treatment from 276 to 414 MPa. Inactivation of S. cerevisiae by HHP is dependent on structural changes on the cell walls observed with SEM.

SEM을 이용한 출토 견섬유의 손상 형태에 관한 연구

배순화 ( Soon Wha Bae ),이미식 ( Mee Sik Lee ) 한국의류학회 2013 한국의류학회지 Vol.37 No.5

After analyzing excavated 17-18th century silk fibers through a scanning electron microscopy, we discovered seven different kinds of fracture morphology. Using Morton & Hearle fiber fracture morphology, we classified the findings into four different categories. Type I is tensile failure resulting from brittle fracture, granular fracture, and ductile fracture. Type II is fatigue failure caused by tensile fatigue, flex fatigue, and axial split (fibrillation). Type III is bacterial deterioration discovered only in excavated artifacts. Type IV is a combination of the three above. Humid underground conditions and the infiltration of bacteria caused the fibers to swell and weaken its interfibrillar cohesion. Fractures occur when drying and processing an excavated artifact that is already in a fragile condition. Therefore, one must minimize damage through a prompt cleaning process and make sure that the least possible force is exerted on the fabric during any treatment for repair and exhibition.

Spark Plasma Sintering Behavior of Pure Aluminum Depending on Various Sintering Temperatures

권한상,박대훈,박용하,Jean François Silvain,Akira Kawasaki,박용호 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.1

We have successfully fabricated high-density pure aluminum (Al) bulk by means of a spark-plasma-sintering (SPS) process. The relative density of Al was enhanced as the sintering temperature of the SPS process increased. During the SPS process for pure Al power, the Al oxide layer on the surface of the Al particle was partially broken by the microplasma and applied pressure. The microstructures of the spark-plasma-sintered compacts obtained at various temperatures were observed by optical microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. We believe that the pinning effect,rapid heating cycle, and applied pressure played an important role in restraining the particle growth despite the increase in sintering temperature. It is feasible that the employed SPS process could be very useful to achieve fully densified Al compact.

Effect of Annealing Temperature on the Microstructure and Tensile Properties of a Bimodal Nano/Micro Grained 1020 Carbon Steel Prepared by Aluminothermic Reaction Casting

Peiqing La,Xin Guo,Hongding Wang,Ting Shi,Xiaojuan Zhen,Fuan Wei,Xuefeng Lu 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2

Bulk 1020 carbon steel was prepared by aluminothermic reaction casting. After casting, isothermal aging treatments at different temperatures are performed for different periods up to 8 h. Microstructure characterization was performed using many methods, including optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that the steel consisted of a nanocrystalline- ferrite matrix and a microcrystalline pearlite phase with a laminar structure. The average grain sizes of the ferrite were 23, 24, 28, and 37 nm for the cast steel and for samples annealed at 600, 800, and 1000 °C, respectively. As the annealing temperature increased, the volume fraction of the pearlite initially increased and then decreased, while the laminar spacing of pearlite increased from 240 to 900 nm. When annealed at 1000 °C, a spherical black micron pearlite particle was formed. The tensile and yield strength dramatically decreased, and the elongation varied slightly with the annealing temperature. A ductile phase was achieved by extending the holding time.

Tribological and Corrosion Behaviour of Electroless Ni-B Coating Possessing a Blackberry Like Structure

Ferhat Bülbül,Hikmet Altun,Özkan Küçük,Vefa Ezirmik 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.4

This study aims to evaluate the tribological and corrosion properties of the electroless Ni-B coating deposited on AISI 304 stainless steels. The microstructure of the coating was characterized using x-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). XRD analysis revealed that the prepared coating possessed an amorphous character. SEM-EDS investigation also indicated that a non-stoichiometric Ni-B coating was deposited with a columnar growth mechanism on the stainless steel substrate and the morphology of the growth surface was blackberry-like. The hardness and tribological properties were characterized by microhardness and a pin-on-disc wear test. The electroless Ni-B coated sample had a higher degree of hardness, a lower friction coefficient and a lower wear rate than the uncoated substrate. The electrochemical potentiodynamic polarization method was used to evaluate the corrosion resistance of the coating. The electroless Ni-B coating offered cathodic protection on the substrate by acting as a sacrificial anode although it was electrochemically more reactive than the stainless steel substrate.

Influence of Cooling Rate on Secondary Phase Precipitation and Proeutectoid Phase Transformation of Micro-Alloyed Steel Containing Vanadium

Kun Dou,Lingtao Meng,Qing Liu,Bo Liu,Yunhua Huang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3

During continuous casting process of low carbon micro-alloyed steel containing vanadium, the evolution of strand surface microstructure and the precipitation of secondary phase particles (mainly V(C, N)) are significantly influenced by cooling rate. In this paper, influence of cooling rate on the precipitation behavior of proeutectoid α-ferrite at the γ-austenite grain boundary and in the steel matrix are in situ observed and analyzed through high temperature confocal laser scanning microscopy. The relationship between cooling rate and precipitation of V(C, N) from steel continuous casting bloom surface microstructure is further studied by scanning electron microscopy and electron dispersive spectrometer. Relative results have shown the effect of V(C, N) precipitation on α-ferrite phase transformation is mainly revealed in two aspects: (i) Precipitated V(C, N) particles act as inoculant particles to promote proeutectoid ferrite nucleation. (ii) Local carbon concentration along the γ-austenite grain boundaries is decreased with the precipitation of V(C, N), which in turn promotes α-ferrite precipitation.

Morphological and Chemical Analysis of Various Disposable Acupuncture Needles Used in South Korea

Dong Yong Park,JiYoon Ahn,Hyeon Jeong Park,Doo Suk Lee,Dae-Hyun Jo,Jonghoon Kim,Choulmin Kim,Heebum Chung,Ji Hye Hwang 대한약침학회 2022 Journal of pharmacopuncture Vol.25 No.4

Objectives: The Korean Industrial Standard (KS) for sterile acupuncture needles was established in 2009 based on research on the quality control of acupuncture needles. We aimed to determine the quality of acupuncture needles available in South Korea in 2021 by examining their surface condition and chemical composition using field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Methods: In South Korea, there are 23 brands of acupuncture needles, and we examined 10-15 needles from each brand, resulting in a total of 285 needles. The microstructures of the needles were assessed by SEM. Using SEM images, we evaluated the acupuncture needle tips for the following defects/aspects: scratches, lumps, detached coating, bent tip, and tip sharpness. EDS was used to determine the chemical composition of the selected acupuncture needles. Results: Overall, 88.4% of 285 needles were found to have at least one type of abnormality. The most frequently observed abnormalities were scratches and dents on the surface (68.1%), followed by detached coating (63.2%), and lumps (61.8%); blunt tips were observed in about 24% of them. Of 252 needles with at least one defect, 86.9% had two or more types of defects. The ratio of the number of needles with any defect to that of needles without any defect varied among brands, ranging from 50% to 100%. Regarding foreign materials, higher proportions of Si and O were observed on the needles, indicating incomplete or detached silicone coating. Conclusion: The quality of acupuncture needles varied among brands, suggesting that further improvements can be made through various inspection methods.

Functional Properties and Morphology of NiTi Articulated Actuation Elements During Thermo-Mechanical Cyclic Tests

Adelaide Nespoli,Elena Villa,Francesca Passaretti 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3

Shape memory alloys (SMAs) are active materials able to recover large strains over several thermo-mechanical cycles. In the actuation field, this strain recovery is principally exploited on the mini and micro scales at which SMAs exhibit their highest power density with respect to common lightweight technologies. During the repetitive actuation of a SMA element, certain events occur: strain drift at the beginning of cyclic testing, the accumulation of plastic deformation, and strain stabilisation. In this study, these events as well as the overall mechanical response of an articulated NiTi element were monitored through calorimetry and scanning electron microscopy. Fatigue and cyclic stability were tested under different loads and under different aging conditions. In addition, the surface morphology was continuously observed via scanning electron microscopy to monitor crack growth and propagation during the fatigue test. Finally, before and after the fatigue test, samples were tested through calorimetry to investigate the overall microstructural homogeneity. Results confirm the high potential of the proposed geometry for the development of NiTi non-conventional active elements in the miniature actuation field.

UVO 표면 전처리에 따른 Cu2O 성장 및 광 전극 특성 연구

이후중 ( Hu Joong Lee ),김태겸 ( Tae Gyoum Kim ),오희봉 ( Hee-bong Oh ),류혁현 ( Hyuk Hyun Ryu ),이원재 ( Won-jae Lee ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.6

Ultraviolet ozone (UVO) surface-treatment was carried out on fluorine-doped tin oxide (FTO) substrate prior to the growth of Cu2O thin-films by electrochemical deposition. This was done to improve their photo-electrochemical properties. We examined the effect of various durations of UVO surface-treatment on the morphological, structural, optical and photo-electrochemical properties of Cu2O thin-films. The effects were measured via field-emission scanning-electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectroscopy and 3-electrode potentiostat, respectively. The highest photocurrent density (4.22 mA/cm2) was achieved with a 2-minute UVO surface-treatment.(Received August 19, 2014)

The phylogenetic potential of orbicules in angiosperms

문혜경 한국식물분류학회 2018 식물 분류학회지 Vol.48 No.1

The distribution of orbicules was investigated for eleven taxa of six genera in Lamiaceae and four taxa of three genera in Verbenaceae using scanning electron microscopy. A literature survey to evaluate the phylogenetic potential of the orbicules and their possible correlations with tapetum types was also conducted. The orbicules are consistently absent in all investigated taxa of Lamiaceae, while small orbicules of an average size of less than 1 µm are densely distributed in Verbenaceae. In fact, orbicules appear consistently in 123 of 150 angiosperm families when investigated in at least one species. Thus, the distribution patterns of orbicules could be a useful diagnostic character in angiosperms. In addition, orbicules occur in 84% taxa of the secretory tapetum type, while they are commonly absent in the amoeboid tapetum type (ca. 80%). The presence of orbicules may be correlated with the secretory tapetum type. However, the study of orbicules is restricted in 150 families and the tapetum type within these families can be applied for 92 families out of a total of 416 angiosperm families. Thus, further investigation of orbicules is necessary in extended taxa to address the questions pertaining to orbicules.