Microstructure Characterization Of Calcified Tissues By Xrd Using An Area Detector

2008 ◽  
Vol 1094 ◽  
Author(s):  
Alejandro Rodriguez-Navarro ◽  
Antonio G. Checa
Keyword(s):  
Crystal Size ◽  
Self Organization ◽  
Polycrystalline Materials ◽  
Area Detector ◽  
Mineral Components ◽  
Ordered Assembly ◽  
Diffraction Patterns ◽  
Calcified Tissues ◽  
Textured Materials

AbstractOrganisms can precipitate a wide array of minerals which they use to build calcified tissues (i.e., bone, mollusk shell, eggshell, coccolith) having highly sophisticated microstructures. The disposition of organic and mineral components building these materials is highly organized from the nano- to the millimeter scale. Their ordered assembly implies self-organization processes accorded in space and time, giving rise to highly sophisticated textured materials. The objective of our work is the study of fundamental processes in biomineralization such as self-organization processes and texture control in biomineral crystal aggregates. To study the order in the arrangement of shell making crystals we used area detectors available today in modern X-ray diffractometers. The 2D diffraction patterns, collected using such detectors, contain detailed information not only about the mineralogy but also about the microstructure characteristics of polycrystalline materials – crystal size, stress, crystallinity and crystallographic-texture. For instance, to understand microstructure development in mollusk shells, we use this type of detector to do microdiffraction analyses combined with high resolution SEM in order to follow the ordering mechanisms of crystals making these biomaterials.

scholarly journals Determination of crystal size distribution by two-dimensional X-ray diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1131-C1131
Author(s):  
Alejandro Rodriguez-Navarro ◽  
Krzysztof Kudłacz
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
High Sensitivity ◽  
Crystal Size Distribution ◽  
Polycrystalline Materials ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Area Detector ◽  
Diffraction Patterns

Polycrystalline materials properties and behaviour are ultimately determined by their crystallinity, phase composition and microstructure (i.e., crystal size, preferential orientation). Two-dimensional (2D) diffraction patterns collected with an area detector (i.e., CDD), available in modern X-ray diffractometers, contain detailed information about all these important material characteristics. Furthermore, recent advances in detector technologies permits the collection of high resolution diffraction patterns in which the microstructure of the material can be directly imaged. If the size of beam relative to the crystal size in the sample is adequately choosen, the diffraction pattern produced will have spotty rings in which the spots are the diffracted images of individual grains. The resolution of the image is mainly dependent on the characteristics of the X-ray beam (i.e., diameter, angular divergence), which can be modulated by X-ray optics, sample to detector distance, the pixel size of the detector and the sharpness of the point spread function. From these patterns, the crystal size distribution of different crystalline phases present in the sample can be independently determined using specialized software capable of extracting and combining the information contained in these patterns. This technique is applicable to materials with crystal sizes ranging from submicron to mm sizes and is complementary to techniques based on peak profile analyses (i.e., Scherrer method) which are applicable only to nanocrystalline materials. Finally, given the high sensitivity of current detectors, crystal size evolution can be followed in real-time to study important transformation processes such as crystallization, annealing, etc. The use of 2D X-ray diffraction as applied to microstructure characterization will be illustrated through several examples.

Registering pole figures using an X-ray single-crystal diffractometer equipped with an area detector

2007 ◽  
Vol 40 (3) ◽  
pp. 631-634 ◽  
Author(s):  
Alejandro B. Rodriguez-Navarro
Keyword(s):  
Single Crystal ◽  
Three Dimensional ◽  
Polycrystalline Sample ◽  
Polycrystalline Materials ◽  
X Ray ◽  
Area Detector ◽  
Pole Figures ◽  
Bruker Smart Apex ◽  
Dimensional Distribution ◽  
Textured Materials

The orientation of crystals in a polycrystalline sample is adequately described using pole figures, displaying the three-dimensional distribution of specific crystallographic directions or poles. Registration of pole figures is necessary to characterize the preferred orientation of crystals and its influence on the anisotropy of properties in textured materials. It is also useful to understand the development of highly organized microstructures in polycrystalline materials. Pole figures can be registered efficiently using an area detector, available at most modern single-crystal diffractometers. This paper describes in detail the procedure of data collection and processing of pole figures using a single-crystal diffractometer equipped with an area detector. Specifically, a Bruker SMART APEX diffractometer was used, but this methodology can be readily adapted to other diffractometers.

XRD2DScan: new software for polycrystalline materials characterization using two-dimensional X-ray diffraction

2006 ◽  
Vol 39 (6) ◽  
pp. 905-909 ◽  
Author(s):  
Alejandro B. Rodriguez-Navarro
Keyword(s):  
Polycrystalline Materials ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Area Detector ◽  
Multiple Data ◽  
Different Types ◽  
Ψ Angle ◽  
Data Files ◽  
Diffraction Patterns

XRD2DScanis a Windows application for displaying and analyzing two-dimensional X-ray diffraction patterns collected with an area detector. This software allows users to take full advantage of diffractometers that are equipped with an area detector but that cannot readily process the information contained in diffraction patterns from polycrystalline materials.XRD2DScanhas many capabilities for generating different types of scans (2θ scan, ψ scan,dspacingversusψ angle), which allows users to extract the maximum amount of information from two-dimensional patterns. Analyses of multiple data files can be fully automated using batch processing. The use of the software is illustrated through several examples.

Interface structures in polycrystalline ceramic materials

1986 ◽  
Vol 44 ◽  
pp. 468-471
Author(s):  
K. J. Morrissey
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Physical And Mechanical Properties ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Polycrystalline Materials ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Interface Structures

Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.

Electron diffraction studies of amorphous and polycrystalline thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 118-119
Author(s):  
D J H Cockayne ◽  
D R McKenzie
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Polycrystalline Materials ◽  
Good Resolution ◽  
Scattered Intensity ◽  
Radial Density ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Nitrogen Ion ◽  
Diffraction Patterns

The study of amorphous and polycrystalline materials by obtaining radial density functions G(r) from X-ray or neutron diffraction patterns is a well-developed technique. We have developed a method for carrying out the same technique using electron diffraction in a standard TEM. It has the advantage that studies can be made of thin films, and on regions of specimen too small for X-ray and neutron studies. As well, it can be used to obtain nearest neighbour distances and coordination numbers from the same region of specimen from which HREM, EDS and EELS data is obtained.The reduction of the scattered intensity I(s) (s = 2sinθ/λ ) to the radial density function, G(r), assumes single and elastic scattering. For good resolution in r, data must be collected to high s. Previous work in this field includes pioneering experiments by Grigson and by Graczyk and Moss. In our work, the electron diffraction pattern from an amorphous or polycrystalline thin film is scanned across the entrance aperture to a PEELS fitted to a conventional TEM, using a ramp applied to the post specimen scan coils. The elastically scattered intensity I(s) is obtained by selecting the elastically scattered electrons with the PEELS, and collecting directly into the MCA. Figure 1 shows examples of I(s) collected from two thin ZrN films, one polycrystalline and one amorphous, prepared by evaporation while under nitrogen ion bombardment.

Automated Characterization of Atheromatous Plaque in Intravascular Ultrasound Images Using Neuro Fuzzy Classifier

2012 ◽  
Vol 58 (4) ◽  
pp. 425-431 ◽  
Author(s):  
D. Selvathi ◽  
N. Emimal ◽  
Henry Selvaraj
Keyword(s):  
Intravascular Ultrasound ◽  
Human Error ◽  
Human Life ◽  
Classification Performance ◽  
Atheromatous Plaque ◽  
Ultrasound Images ◽  
Fuzzy Classifier ◽  
Neuro Fuzzy ◽  
Calcified Tissues

Abstract The medical imaging field has grown significantly in recent years and demands high accuracy since it deals with human life. The idea is to reduce human error as much as possible by assisting physicians and radiologists with some automatic techniques. The use of artificial intelligent techniques has shown great potential in this field. Hence, in this paper the neuro fuzzy classifier is applied for the automated characterization of atheromatous plaque to identify the fibrotic, lipidic and calcified tissues in Intravascular Ultrasound images (IVUS) which is designed using sixteen inputs, corresponds to sixteen pixels of instantaneous scanning matrix, one output that tells whether the pixel under consideration is Fibrotic, Lipidic, Calcified or Normal pixel. The classification performance was evaluated in terms of sensitivity, specificity and accuracy and the results confirmed that the proposed system has potential in detecting the respective plaque with the average accuracy of 98.9%.

Chemical, Physical and Engineering Characterization Of Candidate Backfill Clays and Clay Admixtures for a Nuclear Waste Respository-Part I

1981 ◽  
Vol 6 ◽  
Author(s):  
Sudesh K. Singh
Keyword(s):  
Nuclear Waste ◽  
Morphological Changes ◽  
Deionized Water ◽  
Engineering Properties ◽  
Nuclear Waste Repository ◽  
Exchange Cation ◽  
Mineral Components ◽  
Waste Repository ◽  
Mineralogical Compositions

ABSTRACTFourteen Canadian clays and clay admixtures were subjected to simulated nuclear waste repository environments. The present work is concerned with the montmorillonite-dominant materials only. The montmorillonite-dominant samples showed significant leaching on interaction with deionized water. On heating the samples at 200°C for 500 hours, montmorillomites lost intermicellar water completely and acquired cusp-like to cylindrical morphologies. The loss of water and the morphological changes in montmorillonites significantly altered the engineering characteristics. Permeability, shrinkage limits, compactability and shear strength varied in response to the dominant exchange cation in the structure of montmorillonites and the presence of other mineral components in the materials. The synthetic granite water reacted with montmorillonites and led to changes in chemical and mineralogical compositions, crystalline state and engineering properties.

Formation Of Single-Wall Carbon Nanotubes Forrest Assemblies On Metal Surfaces

2002 ◽  
Vol 734 ◽  
Author(s):  
Debjit Chattopadhyay ◽  
Izabela Galeska ◽  
Fotios Papadimitrakopoulos
Keyword(s):  
Carbon Nanotubes ◽  
Surface Coverage ◽  
Iron Hydroxide ◽  
Growth Characteristics ◽  
Self Organization ◽  
Single Wall Carbon Nanotubes ◽  
Unique Challenge ◽  
Single Wall Carbon ◽  
Topological Characteristics

ABSTRACTLearning how to purify and manipulate single wall carbon nanotubes (SWNTs) presents a unique challenge in material science. The processing-related difficulties of these long nano-fibers stem from their high aspect ratio, rigidity and the profound hydrophobic attractions along their tubular walls. Shortening them into discrete segments, with lengths from tens to hundreds of nanometers, presents a viable methodology to alleviate the shape-induced intractability. In addition, the metal-assisted self-organization of these nanosized objects into nano-forest geometries with dense perpendicular surface grafting, demonstrates that such nanosized objects hold significant promise for the development of nanoscale devices. This paper will present an extensive characterization of the topological characteristics of these assemblies, along with their surface coverage, growth characteristics and height fluctuation on iron hydroxide substrates.

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