Results Of Scanning Electron Microscope Observation Research Articles

Strength degradation of GFRP cross-ply laminates in hydrothermal conditions

The changes in mechanical properties of glass fiber reinforced plastic cross-ply laminates as a result of hydrothermal aging were studied theoretically. The composite specimens have been immersed in distilled water at 25, 40, and 70 °C for 60 days for aging testing. Based on Fick’s law and the Arrhenius theorem, the moisture absorption data under different environments was analyzed, and the method for determining the diffusivity and the equilibrium moisture content was obtained. The relationship model between the moisture absorption behavior of the composite material and the ambient temperature was proposed and verified by finite element analysis. The mechanical behavior of the composites was studied by tensile, compression, and three-point bending tests. Under the condition of ultimate moisture absorption, the tensile, compressive, and bending strengths of the composite decreased by 31.663%, 12.948%, and 26.985%, respectively. A variety of empirical models were used for data analysis, which confirmed the strong correlation between strength degradation and moisture absorption of composite cross-ply laminates. The scanning electron microscope observation results of different moisture absorption levels showed that matrix cracking and fiber/matrix interface debonding caused by moisture absorption are the fundamental reasons for the strength degradation of the composites.

Numerical estimation of fretting fatigue life of bolted joints using continuum damage mechanics and SEAM Tool

For fretting fatigue, micro-slipping often causes initial micro-cracks in the contact surfaces, which gradually propagate and eventually result in fracture failure. However, it is difficult to directly observe and measure the crack initiation and propagation processes of single-lap bolted joints due to the obstacle of testing technique. Therefore, this article presents an elastic analysis–based method, in which the total fretting fatigue lifetime is divided into initiation life predicted by continuum damage mechanics and propagation life calculated by SEAM Tool in combination with Paris’s law. Since the initiation life model implicitly reflects the result of damage process, one can directly calculate the initiation life based on the elastic stress analysis. The predicted fretting fatigue life, initial crack location, and propagation path are in reasonable agreement with the fretting fatigue test and scanning electron microscope observation results. In addition, it is found that among the main factors affecting fretting fatigue of steel single-lap bolted joints, the initial life is affected by cyclic stress, friction coefficient, and tightening torque, and the propagation path is mainly influenced by tightening torque.

SEM Observation of Hydrous Superabsorbent Polymer Pretreated with Room-Temperature Ionic Liquids

Room-temperature ionic liquid (RTIL), which is a liquid salt at or below room temperature, shows peculiar physicochemical properties such as negligible vapor pressure and relatively-high ionic conductivity. In this investigation, we used six types of RTILs as a liquid material in the pretreatment process for scanning electron microscope (SEM) observation of hydrous superabsorbent polymer (SAP) particles. Very clear SEM images of the hydrous SAP particles were obtained if the neat RTILs were used for the pretreatment process. Of them, tri-n-butylmethylphosphonium dimethylphosphate ([P4, 4, 4, 1][DMP]) provided the best result. On the other hand, the surface morphology of the hydrous SAP particles pretreated with 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) was damaged. The results of SEM observation and thermogravimetry analysis of the hydrous SAP pretreated with the RTILs strongly suggested that most water in the SAP particles are replaced with RTIL during the pretreatment process.

Preparation and characterisation of scandia doped dispenser cathodes

Scandia doped dispenser cathodes were prepared by powder metallurgy method using mixed powder of scandia doped tungsten, barium–calcium aluminates obtained by sol–gel method. The scanning electron microscope observation results indicate that the cathode has submicron quasi–spherical tungsten grains structure with homogeneous distribution of Sc2O3 and barium–calcium aluminates which dispersed over and among W grains. The cathode exhibits good emission property, i.e. the current density of this cathode can reach more than 40A/cm² at 850°Cb. The cathode has low work function of 1.43 eV. Active substance of Sc, Ba and O diffuse from the inner part of cathode to the surface to form a Ba–Sc–O multilayer having certain ratios of Ba:Sc:O which contains much more Ba than normal dispenser cathode at the surface of Sc2O3–W matrix cathode during the activation period. This active–multi–layer is considered to be responsible for copious emission capability.

Effect of commercial alcoholic drinks on sound enamel surface of bovine teeth

Copyright © 2013 by Journal of Korean Academy of Oral Health This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives: The purpose of this study was to evaluate the change in surface microhardness of sound enamel of bovine teeth due to commercial alcoholic drinks. Methods: The experiment group comprised of wines, makgeollis, and beers with low pH, while distilled water was used as the control. The two experiment groups were administered soju having the highest (SojuH) and lowest (SojuL) pH. Drinking wines were classified into 2 groups: agitated (wine A) and nonagitated (wine NA) wines. The pH values, buffering capacity, and concentrations of fluorine, calcium, and phosphorus of both the wine groups were measured. Eighty-four bovine specimens were divided into seven groups (N=12) and were immersed for 1, 3, 5, 10, 30, 60, and 120 min, respectively. The surface microhardness was measured using a microhardness tester before and after treatment with each alcoholic drink. After 120 min, the enamel surface was examined using a scanning electron microscope (SEM). The statistical methods used in this study were one-way analysis of variance (ANOVA) and repeated-measure ANOVA. Results: The differences in the surface microhardness (∆VHN) values obtained before and after treatment for 120 min were statistically significant among groups. Makgeolli, wine A, and wine NA significantly eroded the enamel after 120 min. However, sojuH and sojuL had an effect similar to that of distilled water, which was used in the control group. Beer caused slight enamel erosion. SEM images revealed that makgeolli, wine A, and wine NA caused significant erosion of the enamel surface, while beer caused slight erosion. SEM observation results were similar to those obtained after surface microhardness evaluation. Conclusions: The study findings suggest that alcoholic drinks, such as makgeolli and wine, with organic acids and a pH value less than 4.0 can cause tooth enamel erosion. Therefore, alcoholic drinks with low pH values and organic acid composition should not be retained for long periods in the mouth.

Analysis of the Behaviour of Rolling Bearings in Contaminated Oil Using Some Condition Monitoring Techniques

Friction and wear behaviours of rolling bearing in contaminated oil containing white-fused alumina particles were studied. The friction and wear processes were monitored using wear debris analysis, such as ferrography and spectrometric oil analysis program, and vibration analysis. Test bearing was a deep groove ball bearing (6002P5); Wear debris and worn surfaces of the bearing components were observed with a scanning electron microscope (SEM). It was found that the friction coefficient in the contaminated oil became lower by about 0.001 than that in the new oil for the large contaminants. The results of wear debris analysis showed that the large contaminants caused the high wear rate in the bearing. Three types of wear debris were commonly observed: thread-like debris, cutting chip debris, and plate-like debris. On the basis of the SEM observation results of the worn surfaces, wear mechanisms of these wear debris were discussed. The results of vibration analysis showed that the probability density function of vibration waveform was normal distribution in both the new and contaminated oils. In the contaminated oil, it changed depending on the contaminant size and the runtime, i.e. the progress of wear in the bearing. The result of wear debris analysis was related to that of vibration analysis and discussed.

SEM evaluation of neodentinal bridging after direct pulp protection with mineral trioxide aggregate

The purpose of this study was to observe the basic morphology and determine the chemical composition of neodentinal bridges adjacent white mineral trioxide aggregate (WMTA) when used as a direct pulp capping material. The experimental procedures were performed on six intact dogs' teeth. The pulps were exposed and cavities were filled with WMTA. After 2 weeks, neodentinal bridge formation was evaluated by scanning electron microscope (SEM) of cross-sections of the specimens and electron probe microanalysis (EPMA) of the pulpal surfaces. Results of SEM observation showed that the most characteristic reaction of pulp cells was the intimate connection of cell processes and secreted extracellular fibres with the crystals of the pulp capping material. Results of EPMA indicated that the mineralisation of neodentinal bridge formation occurred progressively from the periphery to the central area. Based on these results, it appears that WMTA has the potential to be used as a direct pulp capping material during vital pulp therapy.

홍화씨 Youghurt 급여가 난소절제 Rat의 골다공증에 미치는 영향

홍화씨 yoghurt가 골다공증에 미치는 영향을 조사하기 위하여 sham-operation되어 6주간 정상식이한 군을 대조구로 하였고, 난소 절제하여 6주간 저칼슘식이한 군을 정상식이군(G I), yoghurt를 첨가하여 사육한 군(G II) 및 1%<TEX>${\sim}$</TEX>4%홍화씨yoghurt를 첨가하여 사육한 군(GIII<TEX>${\sim}$</TEX>GVI)으로 구분하여 실험식이를 급여하였다. 사료섭취량, 체중 증가량 및 사료효율을 알아보았고, 왼쪽 대퇴골의 무게, 밀도, 길이, 강도, 회분 및 무기질 함량을 조사하였다. 또한 오른쪽 대퇴골의 조직을 SEM으로 관찰하였다. 사료섭취량은 대구조와 실험구간 유의적인 차이는 없었다. 사료효율 및 체중 증가량은 홍화씨 yoghurt 식이구가 유의적으로(P < 0.05) 높았으며, 특히 GV와 GVI구가 높게 나타났다. 왼쪽 대퇴골의 밀도, 강도, 회분 및 미네랄 함량은 대조구와 G I간에 유사한 경향을 나타내었고, 홍화씨 첨가수준이 높을수록 유의적으로 높게 나타났다. 반면 무게와 길이는 전 실험구에 있어서 거의 일정하게 나타났다. 전자현미경으로 측정한 결과 4% 홍화씨 yoghurt 식이구(GVI)가 가장 골다공증 치유효과가 높은 것으로 나타났다. 이상의 결과 홍화씨 yoghurt 식이가 난소 절제 및 저칼슘식이를 한 rat의 골다공증에 미치는 효과에 있어서 정상식이 및 yoghurt 식이구보다 홍화씨 yoghurt 식이구가 높은 치유효과를 보였으며 가장 우수한 것으로 나타났다. This study was performed to investigate the effect of satllower(Carthamus tinctorius L.) seed yoghurt on osteoporosis. Sham-operated rats(control) were fed basal diet for 6 weeks. Ovariectomized rats were divided into 6 different experimental groups including basal diet group(G I), yoghurt diet group(G II) and 1% to 4% safflower seed yoghurt diet group(GIII to GVI). and fed with the experimental diet for 6 weeks, respectively. The feed intake, feed efficiency ratio and body weight gains of rats fed with the experimental diet for 6 weeks were analyzed, respectively, and the weight. length, strength, mineral content and density in left femur of the animals were determined, respectively. Also, the right femur tissues were observed by Scanning Electron Microscope(SEM). The level of feed intake was not different among all experimental groups. The feed efficiency ratio and body weight gain were high in safflower seed yoghurt groups, and GV and GVI appeared high specially. Density, strength, ash content and minerals content in left femur were similar between control and G I, and increased with increasing the amount of satllower seed in yoghurt. On the other hand, weight and length in left femur showed no difference among all experimental groups. From the results of SEM observation of right femur tissue, GVI showed high healing effects. From the results of this experiment the healing effects of satllower seed yoghurt diet group were higher than those of control and G I. Among the treatments, GVI showed the highest healing effects on the osteoporosis in ovariectomized rats.

Natural formation of multiatomic steps on patterned vicinal substrates by MOVPE and application to GaAs QWR structures

In this paper, we investigate multiatomic steps naturally formed on patterned vicinal GaAs substrates during metal organic vapor phase epitaxial (MOVPE) growth. The substrates are (0 0 1)GaAs misoriented by 2.0° and 5.0° toward [−1 1 0] direction. Periodic trenches are formed on the substrate with periods of 0.4–4.0 μm along the [1 1 0] direction using electron beam lithography and wet etching techniques. Periodic multiatomic step structures are clearly observed on AlGaAs/GaAs grown surfaces which are almost equal to the periods of the underlying substrate patterns. From cross-sectional scanning electron microscope (SEM) images, the growth modes are observed. As the growth proceeds, the growth modes change and can be divided into three regions; the multiatomic step formation, transition and multiatomic step dissociation regions. The multiatomic step features also depend on the pattern periods. GaAs grown layer thicknesses at the edges of the multiatomic steps are thicker than those on the terraces, and this effect is prominent for shorter periodicity patterns. GaAs/AlGaAs quantum wells are grown on patterned vicinal substrates with a 0.4 μm period. The cathodoluminescence (CL) spectrum at 7.0 K has two emission peaks. From the surface and cross-sectional CL images, the lower energy peak corresponds to the quantum well formed at the edges of the multiatomic steps and the higher energy peak corresponds to that on the terrace, consistent with the results of cross-sectional SEM observations. Using optimized patterning and growth condition, we can fabricate highly uniform quantum wire (QWR) arrays at the step edges.

Study On Mechanical Factor Of Grain BoundaryCavity Nucleation Under Creep-fatigue Condition

Creep-fatigue damage at high-temperature on an austenitic stainless steel is characterized by nucleation and growth of creep cavities on grain boundaries. We had carried out continuous observation of the cavity growth process under the creep-fatigue condition by using a high-temperature fatigue machine combined with a scanning electron microscope(SEM) and grasped the cavity growth mechanisms. In this study, in order to clarify a mechanical factor on cavity nucleation under the creep-fatigue condition, creep-fatigue tests under unsymmetrical triangle waveform were conducted on Type304 stainless steel and a cross section of the failure specimens were examined by the SEM. As a result, a volumetric density of damaged grain boundary induced by cavities, which was expressed as a function of time-dependent strain rate, was proposed based on the SEM observation results. The volumetric density of damaged grain boundary under trapezoidal waveform with tensile strain hold could be predicted by the proposal equation with good accuracy.