Scanning electron microscopic structure of the prismatic layer in the Bivalvia

The shell structure of the Bivalvia has been observed with the use of optical and electron microscopes since the early 1900’s. The prismatic structure is one of the more attractive shell structures in bivalved mollusks. This structure is composed of the aggregation of polygonal prisms arranged densely. Each prism is made of small calcite crystallites arranged perpendicular to a growth shell surface. Organic materials, named organic sheaths, accumulate around prisms and stain well with heamatoxylin-eosin. The Bivalvia, which make prismatic structures, are divided into two groups. One group has the inner shell layer made up of a nacreous structure, and the other has the inner shell layer made up of a foliated structure. The aragonite prismatic layer and the prismatic layer are closely related to each other, as is the aragonite prismatic layer to the composite prismatic one.     

Scanning electron microscopic fractography of permanent moulded cast iron

The fracture susceptibility of chill-free permanent moulded cast iron is discussed in terms of graphite configuration. The details of fracture surface topography as revealed by scanning electron microscope examination on areas of slow crack growth and fast fracture are presented and the usefulness of these SEM fractographs in categorizing the fracture modes is demonstrated.     

Scanning electron microscopic study of acacia and eucalyptus wood chars

SEM studies of acacia and eucalyptus wood chars, prepared under different carbonization conditions, were undertaken to provide information on what happens in the transformation of wood to chars. The material normally lost as volatiles contributes totally to the formation of pores, cracks and pyrolytic carbon. Both woods exhibited similar devolatilization behaviour in pore structure development, crack formation and pyrolytic carbon deposition, showing a decrease in pore size with an increase in carbonization temperature and cracks/voids formation during rapid carbonization at higher temperatures (i.e. 800–1050 °C). Slow carbonization led to pyrolytic carbon deposition in resulting wood char structures and did not disturb the fibrous nature and cell structures of the wood, even at a high carbonization temperature of 1200 °C. Prolonged heating at carbonization (slow) temperatures of 800 and 1000 °C caused sintering of the adjacent fibres resulting in the formation of compacted mass.     

Scanning electron microscopic studies on some chemically modified bast fibres

The surface morphology of dewaxed jute and of dewaxed and scoured flax and ramie fibres, and the effect of chemically modified morphologies were compared using scanning electron microscopy (SEM). Limited oxidation results in the removal of surface impurities of the bast fibres, producing strands which are clearly distinguishable in the SEM. Treatment of the oxy-fibres with excess phenol (P) and formaldehyde (F) at pH 8 leads to permanentin situ deposition of P-F resin moieties, which makes the strands less clearly visible. Modification of the P-F treated oxy-fibres by vinyl grafting leads to further masking of the fibre strands due to measurable vinyl deposition; in the SEM the fibre strands appear closely cemented together by the grafted-on vinyl polymer. On exposure to a standard microbiological degradative environment, damage to the fibre strands takes place in the order jute flat ramie; oxy-jute oxy-flax oxy-ramie. Each fibre system suffers little microbiological degradation, thereby showing high rot resistance, when the respective oxy-fibres are modified by P-F treatment and also by vinyl grafting in a subsequent step. At this stage the difference between the three fibre systems in rot resistance becomes slight. The SEM observations are supported by analysis of tensile strength (TS) and retention of TS after exposure to a standard microbiological degradative environment.     

Aragonite observed in the prismatic layer of seawater-cultured pearls

The prismatic layer is obviously different from the parallel layer in seawater-cultured pearls. X-ray diffraction (XRD), optical microscopy (OM) and micro-infrared (IR) spectroscopy have been applied to characterize the crystallized layers of high- and low-quality seawater-cultured pearls produced in South China. The result shows that the prismatic layer is not only composed of calcite as reported in previous researches. Three types of prisms were found in seawater-cultured pearls: calcite prism, aragonite prism and calcite and aragonite prism. Therefore, we have a new understanding of the biomineralization of the prismatic layer in seawater-cultured pearls. The result makes us review the traditional viewpoint that the increased content of aragonite improves the quality of pearls. We discovered that some seawater prismatic pearls almost completely composed of aragonite have the worst quality. We thought that the thickness and the spatial distribution of prisms are the main factors that can affect the quality of seawater-cultured pearls.     

扫描电子声显微镜对骨组织的成像

1引言自1980年由Brandis和Rosencwaig以及Cargill分别建立扫描电子声显微镜(SEAM)以来,由于它可以高分辨率[1]地同时获得试样表面电子显微镜像(SEM)和亚表面SEAM像以及试样制备简     

Scanning electron microscopic studies on the tear fracture of polyethylene filled natural rubber vulcanizate

Tear failure of natural rubber (NR) filled with high density polyethylene (HDPE) was studied by scanning electron microscopy (SEM). The tear strength of NR was increased by the addition of HDPE. It was found that HDPE forms physical links with NR. The retention of tear strength by ageing attains an optimum value with HDPE loading.     

Scanning tunneling microscopic and field emission microscopic studies of nanostructured molybdenum film synthesized by electron cyclotron resonance plasma

Cathodic sputtering is demonstrated to be effective in synthesizing thin films of molybdenum nanoparticles. An electron cyclotron resonance plasma reactor has been used as the source. The particle size distribution is found to be controllable by proper choice of the cathodic bias potential. Sizes ranging between 20 and 30 nm deposited at the optimum bias potential are found to exhibit a self assembled structure as observed by scanning tunneling microscopy. Field emission microscopic studies on these films supported on W have exhibited very stable emission current over a period of 3 h.     

Scanning transmission electron microscopy analysis of grain structure in perpendicular magnetic recording media

The key component of a hard disk medium is a Co-based magnetic layer (ML) grown on a Ru seed layer. The ML nanostructure, composed of less than 10 nm grains, is believed to be controlled by this seed layer. We successfully used scanning transmission electron microscopy energy dispersive spectrometry simultaneous composition-based imaging and Moire? pattern analysis for determining the mutual structural and orientation relationship between the two layers revealing a grain-to-grain agreement. The method presented here can be utilized for observing structural correlations between consecutive polycrystalline thin film layers in general.     

Crystallographic alignment of calcite prisms in the oblique prismatic layer of Mytilus edulis shell

The structure and crystallographic orientation of mineral phase in the oblique prismatic layer of Mytilus edulis shell were studied by SEM, XRD and TEM with selected area electron diffraction (SAED). A crystallographic orientation regulation, i.e. the adjacent 1–5 calcite prisms with the same three-dimensional orientation in the oblique prismatic layer, was found for the first time. It is observed that the calcite prisms in the oblique prismatic layer were grown with their (104) parallel to the shell surface.     

Transmission electron microscopic study of defect structure in natural chalcopyrite (CuFeS2)

Natural chalcopyrite (CuFeS₂) specimens from Golden, New Mexico and Transvaal, South Africa were examined by transmission electron microscopy. The defect structure was composed of dislocations, dislocation loops, tangles, and substructure (including dislocation networks), stacking faults on {112} (both intrinsic and extrinsic), and mechanical twins and twin-faults. Optical microscopy indicated a large grain structure (0.3 to 0.5 cm grain size) containing numerous large twins similar in size to the average grain diameter. It is concluded that the absence of superdislocations of the type 1/4 201 is a result of the CuFeS₂ structure approximating more closely the sphalerite lattice as a result of the c/a ratio approaching 2. It is also concluded that the apparently low stacking fault free energy in CuFeS₂ will give rise to abundant mechanical twins accommodating large deformations, and this may be an important factor in the grinding and leaching of chalcopyrite concentrates. The observations suggest that the defect structure, particularly the occurrence of superdislocations and antiphase boundaries, might increase with a decrease in the c/a ratio for chalcopyrite structures, and this may have an important influence on the electrical and mechanical properties of compounds having the chalcopyrite structure.     

Variational generation of prismatic boundary‐layer meshes for biomedical computing

Boundary‐layer meshes are important for numerical simulations in computational fluid dynamics, including computational biofluid dynamics of air flow in lungs and blood flow in hearts. Generating boundary‐layer meshes is challenging for complex biological geometries. In this paper, we propose a novel technique for generating prismatic boundary‐layer meshes for such complex geometries. Our method computes a feature size of the geometry, adapts the surface mesh based on the feature size, and then generates the prismatic layers by propagating the triangulated surface using the face‐offsetting method. We derive a new variational method to optimize the prismatic layers to improve the triangle shapes and edge orthogonality of the prismatic elements and also introduce simple and effective measures to guarantee the validity of the mesh. Coupled with a high‐quality tetrahedral mesh generator for the interior of the domain, our method generates high‐quality hybrid meshes for accurate and efficient numerical simulations. We present comparative study to demonstrate the robustness and quality of our method for complex biomedical geometries. Copyright © 2009 John Wiley & Sons, Ltd.     

Scanning electron microscope studies of striations in ZnS

ZnS platelets crossed by two orthogonal sets of striations were examined. Nomarski optical interference micrographs and scanning electron microscope (SEM) secondary electron micrographs showed that both sets of striations had associated surface topographical features. One set consisted of polytype or faulted bands, the other of thickness variations (linear markings). SEM cathodoluminescence micrographs showed that in some specimens certain lines in both sets were strong light sources. In other specimens only polytype interfaces were linear cathodoluminescent sources. SEM charge collection micrographs showed that many of the polytype or faulted bands could produce contrast possibly due to the separation of electron-hole pairs by internal electric fields associated with these defects. Transmission electron microscopy showed that there could be several different types of faulted stacking structures in areas a micron square in striated ZnS.     

Infrared spectroscopic and electron microscopic characterization of gold nanogap structure fabricated by focused ion beam

Using infrared spectroscopy of plasmonic resonances and mapping of elemental composition and structure, we investigated the correlation between optical and structural properties of nanometre-scale gaps in gold nanorod dimers fabricated by electron beam lithography (EBL) and focused ion beam (FIB) milling. In spite of their very similar scanning electron microscopy (SEM) images, a fully cut nanogap and a shallower cut with slight imperfection near the gap region were clearly distinguished by their strongly different infrared plasmonic resonance behaviour. The differences in the infrared spectra are related to different structural and chemical results from elaborated cross-sectional transmission electron micrographs and energy dispersive x-ray spectrometry (EDX) mapping of the gap region.