scholarly journals The architecture of Recent brachiopod shells: diversity of biocrystal and biopolymer assemblages in rhynchonellide, terebratulide, thecideide and craniide shells

2021 ◽  
Vol 169 (1) ◽  
Author(s):  
Maria Simonet Roda ◽  
Erika Griesshaber ◽  
Lucia Angiolini ◽  
Claire Rollion-Bard ◽  
Elizabeth M. Harper ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Backscatter Diffraction ◽  
Organic Matrix ◽  
Time Interval ◽  
Marine Animal ◽  
Matrix Assembly ◽  
Animal Group ◽  
Tissue Organization ◽  
Marine Habitats ◽  
Hard Tissues

AbstractBiological hard tissues are a rich source of design concepts for the generation of advanced materials. They represent the most important library of information on the evolution of life and its environmental conditions. Organisms produce soft and hard tissues in a bottom-up process, a construction principle that is intrinsic to biologically secreted materials. This process emerged early on in the geological record, with the onset of biological mineralization. The phylum Brachiopoda is a marine animal group that has an excellent and continuous fossil record from the early Cambrian to the Recent. Throughout this time interval, the Brachiopoda secreted phosphate and carbonate shells and populated many and highly diverse marine habitats. This required great flexibility in the adaptation of soft and hard tissues to the different marine environments and living conditions. This review presents, juxtaposes and discusses the main modes of mineral and biopolymer organization in Recent, carbonate shell-producing, brachiopods. We describe shell tissue characteristics for taxa of the orders Rhynchonellida, Terebratulida, Thecideida and Craniida. We highlight modes of calcite and organic matrix assembly at the macro-, micro-, and nano-scales based on results obtained by Electron Backscatter Diffraction, Atomic Force Microscopy, Field Emission Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. We show variation in composite hard tissue organization for taxa with different lifestyles, visualize nanometer-scale calcite assemblies for rhynchonellide and terebratulide fibers, highlight thecideide shell microstructure, texture and chemistry characteristics, and discuss the feasibility to use thecideide shells as archives of proxies for paleoenvironment and paleoclimate reconstructions.

scholarly journals Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Aleksandra Kozłowska ◽  
Adam Grajcar ◽  
Aleksandra Janik ◽  
Krzysztof Radwański ◽  
Ulrich Krupp ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Retained Austenite ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Stability ◽  
Electron Backscatter Diffraction ◽  
Cost Effective ◽  
Tensile Tests ◽  
Thermal Stability Of

AbstractAdvanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

scholarly journals Oxygen Induced Phase Transformation in TC21 Alloy with a Lamellar Microstructure

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Shu Wang ◽  
Yilong Liang ◽  
Hao Sun ◽  
Xin Feng ◽  
Chaowen Huang
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Oxygen Uptake ◽  
Titanium Alloys ◽  
Electron Backscatter Diffraction ◽  
Lamellar Microstructure ◽  
Α Phase ◽  
Transmission Electron ◽  
The Matrix ◽  
Oxygen Ingress

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix.

Where are the geometrically necessary dislocations accommodating small imprints?

2009 ◽  
Vol 24 (3) ◽  
pp. 647-651 ◽  
Author(s):  
M. Rester ◽  
C. Motz ◽  
R. Pippan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Twin Boundary ◽  
Crystal Orientation ◽  
Electron Backscatter Diffraction ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Copper Single Crystals ◽  
Backscatter Diffraction ◽  
Small Misorientation

Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analyses of small indentations in copper single crystals exhibit only slight changes of the crystal orientation in the surroundings of the imprints. Far-reaching dislocations might be the reason for these small misorientation changes. Using EBSD and TEM technique, this work makes an attempt to visualize the far-propagating dislocations by introducing a twin boundary in the vicinity of small indentations. Because dislocations piled up at the twin boundary produce a misorientation gradient, the otherwise far-propagating dislocations can be detected.

scholarly journals Odontoblast processes in dentin revealed by fluorescent Di-I.

1995 ◽  
Vol 43 (2) ◽  
pp. 159-168 ◽  
Author(s):  
M R Byers ◽  
A Sugaya
Keyword(s):  
Electron Microscopy ◽  
Confocal Microscopy ◽  
Cell Structure ◽  
Carbocyanine Dyes ◽  
Carbocyanine Dye ◽  
Reparative Dentin ◽  
Hard Tissues ◽  
Odontoblast Process ◽  
Odontoblast Processes ◽  
Rat Molars

There has been controversy about the length and structure of the odontoblast process within dentin since the earliest histologic studies of teeth. Our objective was to use the fluorescent carbocyanine dye Di-I combined with a new gelatin embedment procedure and confocal microscopy to determine the structure and extent of odontoblast processes in developing and mature rat teeth, injured rat molars, reparative dentin, and adult monkey teeth. We found that odontoblast processes do not extend into outer dentin or to the dentin-enamel junction except during early stages of development. Those in innervated regions of crown are long and straight, whereas those in roots are extensively branched and shorter. Cavity injury to crown dentin caused odontoblast fragments to be aspirated into outer dentin. In reparative dentin the odontoblast processes were branched and similar to those in roots. We used photoconversion and electron microscopy to show that Di-I fills the entire odontoblast after gelatin embedment, including the cytoplasm. This is a different type of carbocyanine staining from any previously reported, and it also stains other cells in adjacent hard tissues such as bone and cementum. The Di-I-gelatin method is a new way to use carbocyanine dyes. It has enabled us to solve a long-standing controversy about the histology of teeth, and it should be useful for many other studies of cell structure.

scholarly journals Application of Electron Backscatter Diffraction (EBSD) for Crystallographic Characterization of Aluminum-Doped Zinc Oxide Sputtered Films

2013 ◽  
Vol 19 (S4) ◽  
pp. 103-104
Author(s):  
C.B. Garcia ◽  
E. Ariza ◽  
C.J. Tavares
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Zinc Oxide ◽  
Electron Backscatter Diffraction ◽  
Wide Range ◽  
Electron Backscatter ◽  
Aluminum Doped Zinc Oxide ◽  
Ebsd Technique ◽  
Backscatter Diffraction

Zinc Oxide is a wide band-gap compound semiconductor that has been used in optoelectronic and photovoltaic applications due to its good electrical and optical properties. Aluminium has been an efficient n-type dopant for ZnO to produce low resistivity films and high transparency to visible light. In addition, the improvement of these properties also depends on the morphology, crystalline structure and deposition parameters. In this work, ZnO:Al films were produced by d.c. pulsed magnetron sputtering deposition from a ZnO ceramic target (2.0 wt% Al2O3) on glass substrates, at a temperature of 250 ºC.The crystallographic orientation of aluminum doped zinc oxide (ZnO:Al) thin films has been studied by Electron Backscatter Diffraction (EBSD) technique. EBSD coupled with Scanning Electron Microscopy (SEM) is a powerful tool for the microstructural and crystallographic characterization of a wide range of materials.The investigation by EBSD technique of such films presents some challenges since this analysis requires a flat and smooth surface. This is a necessary condition to avoid any shadow effects during the experiments performed with high tilting conditions (70º). This is also essential to ensure a good control of the three dimensional projection of the crystalline axes on the geometrical references related to the sample.Crystalline texture is described by the inverse pole figure (IPF) maps (Figure 1). Through EBSD analysis it was observed that the external surface of the film presents a strong texture on the basal plane orientation (grains highlighted in red colour). Furthermore it was possible to verify that the grain size strongly depends on the deposition time (Figure 1 (a) and (b)). The electrical and optical film properties improve with increasing of the grain size, which can be mainly, attributed to the decrease in scattering grain boundaries which leads to an increasing in carrier mobility (Figure 2).The authors kindly acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) scientific program for the National Network of Electron Microscopy (RNME) EDE/1511/RME/2005.

Orientation relationships between magnetite micro-inclusions and plagioclase host 

2021 ◽  
Author(s):  
Olga Ageeva ◽  
Ge Bian ◽  
Gerlinde Habler ◽  
Rainer Abart
Keyword(s):  
Electron Microscopy ◽  
Electron Backscatter Diffraction ◽  
Orientation Relationships ◽  
Directional Growth ◽  
Crystal Lattices ◽  
Plane Normal ◽  
Transmission Electron ◽  
Easy Direction ◽  
Lattice Planes ◽  
Backscatter Diffraction

<p>Magnetite micro-inclusions in silicate minerals are important carriers of the remanent magnetization of rocks. Their shape orientation relationships (SOR) and crystallographic orientation relationships (COR) to the host crystal are of interest in the context of the bulk magnetic properties of the inclusion-host assemblage. We investigated the SOR and COR of magnetite (MT) micro-inclusions in plagioclase (PL) from oceanic gabbro using correlated optical microscopy, scanning electron microscopy, Electron backscatter diffraction analysis and Transmission electron microscopy.</p><p>In the mm-sized PL crystals of the investigated gabbros MT is present as equant, needle- and lath-shaped (sub)micrometer sized inclusions. More than 95% of the needle-shaped inclusions show SOR and specific COR to the plagioclase host. Most of the needles are elongated perpendicular to one of the MT{111} planes, which is aligned parallel to one of the (112), (1-12), (-312), (-3-12), (150), (1-50) or (100) planes of plagioclase. These inclusions are classified as “plane-normal type”. The needle elongation parallel to MT<111>, which is the easy direction of magnetization, ensures high magnetic susceptibility of these inclusions. The underlying formation mechanism is related to the parallel alignment of oxygen layers with similar lattice spacing across the MT-PL interfaces that are parallel to the elongation direction [1].</p><p>Apart from the SOR and the alignment of a MT{111} with one of the PL low index planes, the MT crystals rotate about the needle elongation direction. The rotation angles are statistically distributed with several maxima representing specific orientation relationships. In some cases one of the MT<001> axes is aligned with PL[14 10 7] or PL[-14 10 -7], which ensures that FeO<sub>6 </sub>octahedra of MT well fit into channels // [001] of PL, which are formed by six membered rings of SiO<sub>4</sub> and AlO<sub>4</sub> tetrahedra [2]. This COR is referred to as the “nucleation orientation” of magnetite with respect to PL. There are several other possibilities to fit FeO<sub>6</sub> octahedra into the [001] channels of PL, but the alignment stated above allows for the additional parallel alignment of one of the MT{111} with one of the above mentioned low index lattice planes of PL. MT crystals with one of these nucleation orientations can undergo directional growth to develop laths and needles. MT crystals with other nucleation orientations that do not allow for the parallel alignment of MT{111} with the above mentioned PL lattice planes, do not significantly grow and form the equant inclusions.</p><p>For some needles one or more of the MT{011} planes that are parallel to the needle elongation direction, are aligned with low-index planes of plagioclase such as PL (112), PL(150), PL(1-50) etc., and form MT facets. This situation corresponds to achievement of the best possible match between the two crystal lattices. This can either be generated during primary growth or during re-equilibration of the micro-inclusions and the plagioclase host.</p><p>Funding by RFBR project 18-55-14003 and Austrian Science fund (FWF): I 3998-N29 is acknowledged.</p><p>Reference</p><p>[1] Ageeva et al (2020) Contrib. Mineral. Petrol. 175(10), 1-16.</p><p>[2] Wenk et al (2011) Am. Min. 96, 1316-1324</p>

scholarly journals The Transport System of Nacre Components through the Surface Membrane of Gastropods

2016 ◽  
Vol 672 ◽  
pp. 103-112 ◽  
Author(s):  
Elena Macías-Sánchez ◽  
Antonio G. Checa ◽  
Marc G. Willinger
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Calcium Carbonate ◽  
Lamellar Structure ◽  
Surface Membrane ◽  
Organic Matrix ◽  
X Ray ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Electron Energy Loss

The surface membrane is a lamellar structure exclusive of gastropods that is formed during the shell secretion. It protects the surface of the growing nacre and it is located between the mantle epithelium and the mineralization compartment. At the mantle side of the surface membrane numerous vesicles provide material, and at the nacre side, the interlamellar membranes detach from the whole structure. Components of nacre (glycoproteins, polysaccharides and calcium carbonate) cross the structure to reach the mineralization compartment, but the mechanism by which this occurs is still unknown. In this paper we have investigated the ultrastructure of the surface membrane and the associated vesicle layer by means of Transmission Electron Microscopy. Electron Energy Loss Spectroscopy and Energy-dispersive X-ray Spectroscopy were used for elemental analysis. The analyses revealed the concentration of calcium in the studied structures: vesicles, surface membrane, and interlamellar membranes. We discuss the possible linkage of calcium to the organic matrix.

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