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Biomineralized structures with intricate shapes and morphologies, such as sea urchin skeletal elements, grow via the deposition of hydrated amorphous calcium carbonate (ACC) particles that subsequently crystallizes into single-crystalline calcite. This process is accompanied by volume changes due to density differences between the initial and final mineral state as well as variations in hydration levels. For this reason, the presence of macroporosity in synthetic systems was shown to be pivotal in the formation of large single crystals through ACC precursors. However, the role of macroporosity down to nanoporosity in the formation of biogenic minerals remains unknown. Here, we investigate the micro- and nano-porosity as well as the evolution of internal interfaces in the spines and test plates of Paracentrotus lividus sea urchins during the heat-mediated crystallization of remnant ACC and the destruction of intracrystalline organic molecules, using SEM, FIB-SEM, and in situ heating synchrotron SAXS measurements. We show the presence of nanopores likely filled with hydrated organics and visualize the evolution of nano- to micro-pores induced by heating, which may serve to accommodate the volume changes between amorphous and crystalline phases. The obtained results analyzed using thermodynamical considerations suggest that the growth in size of the nanopores is controlled by Ostwald ripening and is well described in the framework of classical pore coarsening theories. The extracted activation energies manifest that nanopore coarsening in the test plates is governed by surface diffusion, whereas in the spines by bulk diffusion. We suggest that such striking differences in diffusion mechanisms are caused by dissimilar levels of macroporosity and distributions of nano- and micro-internal interfaces in pristine biominerals.

Cross-sections of calcitic prismatic layers in mollusk shells, cut perpendicular to growth direction, reveal well-defined polygonal shapes of individual “grains” clearly visible by light and electron microscopy. For several kinds of shells, it was shown that the average number of edges in an individual prism approaches six during the growth process. Taking into account the rhombohedral symmetry of calcite, often presented in hexagonal axes, all this led to the long-standing opinion that calcitic prisms grow along the c-axis of calcite. In this paper, using X-ray diffraction and electron backscatter diffraction (EBSD), we unambiguously show that calcitic prisms in pearl oyster Pinctada margaritifera predominantly grow perpendicular to the c-axis. The obtained results imply that the hexagon-like habitus of growing crystallites may be not necessarily connected to calcite crystallography and, therefore, other factors should be taken into consideration. We analyze this phenomenon by comparing the organic contents in Pinctada margaritifera and Pinna nobilis shells, the later revealing regular growth of calcitic prisms along the c-axis.

Molluscan shells, exhibiting a variety of complex three-dimensional architectures, are an exemplar model system to study biogenic mineral formation by living organisms. Recent studies have demonstrated that the deposition process of some shell ultrastructures can be described using classical analytical models borrowed from materials physics, which were developed to predict the structural evolution of man-made and geological polycrystalline composite assemblies. In the current study, we use this newly developed capacity to quantitatively describe the morphogenesis of the prismatic ultrastructure in three shells from the bivalve family Pinnidae towards establishing a correlation between structure, texture, growth kinetics, topology and phylogeny of the species. Using data collected by electron microscopy, synchrotron-based microtomography, electron backscatter diffraction analysis (EBSD) and X-ray diffraction we demonstrate that the prismatic ultrastructures in Pinnidae are formed following either ideal or triple-junction-controlled kinetics, which are shown to be closely linked to the morphological and topological characteristics, as well as crystallographic texture of these biocomposites. The experimental and analytical framework presented in this comparative study can serve as an additional tool for classifying molluscan shell ultrastructures on the levels of structural and textural morphogenesis. STATEMENT OF SIGNIFICANCE: The ability to quantitatively describe the structural evolution of the prismatic architecture in mollusc shells is used for the first time to derive and compare between analytical parameters that define the growth kinetics and morphological and topological evolution during the growth of three shells from the family Pinnidae from two different genera. Furthermore, these parameters are linked to the evolution of crystallographic texture in the studied architectures. The developed experimental and analytical framework not only enables us to quantitatively describe species-specific growth mechanisms but also suggests a direct correlation between the evolution of morphology and texture.

It is shown that periodic modulation of electron density in a liquid layer surrounding a nanocrystal may influence considerably the width of a conventional diffraction profile taken along the normal direction to the liquid/solid interface. The kinematic approximation is used to develop an analytical expression for the diffraction profile, assuming that the degree of order in the modulated liquid-like layers diminishes exponentially with the distance from the interface, which is characterized by the correlation length,L. Owing to the above-mentioned modulation, the sizes of nanocrystals extracted from the width of diffraction profiles will appear larger than they really are. Molecular ordering is destroyed by mild annealing or pressure application, resulting in substantial broadening of X-ray diffraction lines. This effect may be most significant in nano-biocomposites, such as bone and tooth dentin, comprising substantial amounts of water (tens of percent). It is calculated that forL≃ 1 nm and a net crystallite thickness ofT< 50 nm, the relative change in profile width can reach a few percent, which is easily measurable. The obtained simulation results are compared with existing experimental data.

This work explores the ways of manipulating the microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloys of various compositions using hydrogen treatment. Changes to phase composition, microstructure, and mechanical properties of the alloys upon hydrogenation were studied. Prior to hydrogenation, the alloys were extruded at different temperatures with or without subsequent aging. Hydrogen treatment was performed on bulk rods after thermo-mechanical processing. X-ray diffraction and scanning electron microscopy studies showed that a single rare-earth (RE) hydride phase, Gd0.5Y0.5H2, was formed in all samples. As a result, the 14H long period stacking ordered (LPSO) structure, detected before hydrogenation, is completely destroyed due to the clustering of RE atoms into large hydride crystals and annihilation of the specific spatial order within the superlattice. Prolonged hydrogen treatment at high temperature (≈ 0.74·Tm) causes recrystallization and grain growth in the magnesium matrix, defect annealing and reduction of preferred orientation, which together with the complete destruction of the LPSO phase lead to the substantial decrease of alloys’ strength and concomitant increase of their ductility to the record-high value of above 20%.

The mechanical behavior of materials depends to a large extent on their properties at the nanoscale and, therefore, novel characterization techniques with sub-micron spatial resolution were developed in the last decades. Among them are the variety of tools for probing local elastic and viscoelastic properties of materials, the methods such as nanoindentation and AFM- and nanoindenter-based measurements using force modulation. In this review, we describe the nanoindenter-based nanoscale modulus mapping technique, which emerged as an extremely powerful tool for providing quantitative information on the storage and loss moduli distributions in complex nanocomposites. Since the tip penetrates only a few nanometers into the materials, this technique provides a superior lateral resolution in the order of 20 nm. All aspects of the method are covered, including a historical perspective, theoretical analysis, instrumentation, and examples of its application for studying multiphase structures and interfaces. The main focus of this review is the challenging field of natural bio-composites, which consist of stiff and compliant components, often with nanometric dimensions. Gradients of mechanical properties across the nm-sized features in biological materials are of upmost importance for their mechanical performance. Quantitative information on the nano-scale moduli distributions in these structures can hardly be achieved by other means.

Electrical conductivity/resistivity of elemental fcc metals, such as Al and Cu, has been investigated intensively for decades, both theoretically and experimentally. Since these metals are of great practical importance for electrical wiring, reducing their resistivity even by a few percent may have very strong impact on their application effectiveness. In this paper, we report on electrical resistivity measurements in Al single crystals grown by the Bridgman method. We found that their resistivity at room temperature decreases by 11.5% upon heat treatment in a boron environment at 600 °C, i.e., well below the melting temperature of Al (Tm = 660 °C). The residual resistivity indeed reaches its lower limit dictated by electron–phonon interaction at room temperature. We explain this effect by the boron-induced formation of distorted regions at the surface of the Al crystals. These regions are 30–50 μm in size and comprise finer grains with an average size of 5 μm, separated by low-angle grain boundaries. Resistivity reduction is mainly due to the getter effect, i.e., the removal of the impurity atoms from the crystal bulk by the outward diffusion to the distorted surface regions.

In the absence of minerals as stiffening agents, insects and spiders often use metal-ion cross-linking of protein matrices in their fully organic load-bearing "tools". In this comparative study, the hierarchical fiber architecture, elemental distribution, and the micromechanical properties of the manganese- and calcium-rich cuticle of the claws of the spider Cupiennius salei, and the Zn-rich cuticle of the cheliceral fangs of the same animal are analyzed. By correlating experimental results to finite element analysis, functional microstructural and compositional adaptations are inferred leading to remarkable damage resilience and abrasion tolerance, respectively. The results further reveal that the incorporation of both zinc and manganese/calcium correlates well with increased biomaterial's stiffness and hardness. However, the abrasion-resistance of the claw material cross-linked by incorporation of Mn/Ca-ions surpasses that of many other non-mineralized biological counterparts and is comparable to that of the fang with more than triple Zn content. These biomaterial-adaptation paradigms for enhanced wear-resistance may serve as novel design principles for advanced, high-performance, functional surfaces, and graded materials.

Hydrous CaCO 3 gets a new structure Calcium carbonate (CaCO 3 ) forms important minerals on Earth and is a model system for understanding crystal nucleation. Three different structures of CaCO 3 are known, along with two structures that are hydrated. Zou et al. found a third hydrated CaCO 3 structure formed from amorphous CaCO 3 in the presence of magnesium ions. The discovery illustrates the importance of amorphous precursors for producing new materials. Science , this issue p. 396

International audience; Biomineralization processes in living organisms result in the formation of skeletal elements with complex ultrastructures. Although the formation pathways in sea urchin larvae are known, the interrelation between calcite, amorphous calcium carbonate (ACC), and intra-crystalline organics in adult sea urchin biominerals is less clear. Here, we study this interplay in the spines and test 2 plates of the Paracentrotus lividus sea urchins whose skeletal elements have optimized function-properties relationships. Thermogravimetric analysis coupled with differential scanning calorimetry or mass spectrometry measurements, nuclear magnetic resonance technique and high-resolution powder X-ray diffraction show that pristine spines and test plates are composed of Mg-rich calcite and comprise about 10 wt. % of anhydrous ACC, 1.2 to 1.6 wt. % of organics, and less than 0.2 wt. % of water. Anhydrous ACC originates from incomplete crystallization of a precursor ACC phase during biomineralization and is associated with intra-crystalline organics at the molecular level. Molecular interactions at organic/inorganic interfaces cause significant calcite lattice distortions of the tensile type. The latter are amplified during ACC crystallization and finally disappear after heat-assisted destruction of organic molecules. Converting the measured lattice distortions (strains) into internal stress components, we follow stress evolution upon annealing and find that complete crystallization of ACC leads to the isotropy of residual stresses in all investigated skeletal parts. These results allow us to speculate that organic macromolecules are preferentially attached to different crystallographic planes in the pristine test and spine samples.

The tough bulk of dentin in teeth supports enamel, creating cutting and grinding biostructures with superior failure resistance that is not fully understood. Synchrotron-based diffraction methods, utilizing micro- and nanofocused X-ray beams, reveal that the nm-sized mineral particles aligned with collagen are precompressed and that the residual strains vanish upon mild annealing. We show the link between the mineral nanoparticles and known damage propagation trajectories in dentin, suggesting a previously overlooked compression-mediated toughening mechanism.

We apply advanced X-ray diffraction techniques at synchrotron microfocus beamlines in order to study the local ultrastructure of biogenic calcite with high spatial and angular resolution. Specifically, we investigate individual calcitic prisms extracted from Pinna nobilis mollusk shells with an aim to shed additional light on the structural aspects of organic/inorganic interfaces. We use annealing at elevated temperatures to destroy intracrystalline organics and measure the same prisms before and after annealing to achieve deeper understanding of the internal organization of these nanobiocomposites. Complementary nanoindentation measurements (also performed before and after annealing) allow us to elucidate the role of intracrystalline organics in increased hardness in pristine prisms and hardness reduction after annealing. We found that removal of intracrystalline organics during annealing facilitates generation of well-oriented lattice defects, which reduce the (006) diffraction intensity and are respons...

Protein crystal branching guides the morphogenesis of glass spicules in marine sponges from the class Demospongiae., Demospongiae is a class of marine sponges that mineralize skeletal elements, the glass spicules, made of amorphous silica. The spicules exhibit a diversity of highly regular three-dimensional branched morphologies that are a paradigm example of symmetry in biological systems. Current glass shaping technology requires treatment at high temperatures. In this context, the mechanism by which glass architectures are formed by living organisms remains a mystery. We uncover the principles of spicule morphogenesis. During spicule formation, the process of silica deposition is templated by an organic filament. It is composed of enzymatically active proteins arranged in a mesoscopic hexagonal crystal-like structure. In analogy to synthetic inorganic nanocrystals that show high spatial regularity, we demonstrate that the branching of the filament follows specific crystallographic directions of the protein lattice. In correlation with the symmetry of the lattice, filament branching determines the highly regular morphology of the spicules on the macroscale.

One of the most fascinating topics currently being discussed in the field of biomineralization is the occlusion of organic macromolecules within mineral crystals. It is already known that intracrystalline organic inclusions in biogenic calcite improve the fracture behavior and anisotropically distort the calcite lattice. However, the detailed structure of the crystals and the underlying processes leading to the incorporation of the organic molecules are poorly understood. In this work, we investigate calcite prisms extracted from the shell of Pinna nobilis by means of three-dimensional synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS). Organic–inorganic interfaces within the single crystals give rise to a strong, anisotropic SAXS signal. The results are shown as a stereographic projection of the integrated SAXS intensity (gray scale) together with the wide-angle spots (colored) of different calcite lattice planes. A comparison of native (left) and annealed (right) prisms, where the contrast f...

In this study, a newly developed nanoscale modulus mapping is applied in order to visualize the 2D-distribution of mechanical characteristics in the aragonitic nacre layer of Perna canaliculus (green mussel) shells. Modulus maps provide lateral resolution of about 10 nm. They allow the aragonitic mineral (CaCO 3 ) tablets and the interfaces between them to be clearly resolved, which are filled by an organic substance (mainly beta-chitin). The experimental data are compared with finite element simulations that also take into account the tip radius of curvature and the thickness of organic layers, as measured by means of scanning electron microscopy with backscattered electrons. Based on this comparison, the Young modulus of beta-chitin is extracted. The obtained number, E β = 40 GPa, is higher than previously evaluated. The collected maps reveal that the elastic modules in the nacre layer change gradually across the ceramic/organic interfaces within a spatial range four times wider than the thickness of the organic layers. This is possibly due to inhomogeneous distribution of organic macromolecules within ceramic tablets. According to the data, the concentration of macromolecules gradually increases when approaching the organic/ceramic interfaces. A behavior of this type is unique to biogenic materials and distinguishes them from synthetic composite materials. Finally, three possible mechanisms that attempt to explain why gradual changes of elastic modules significantly enhance the overall resistance to fracture of the nacre layer are briefly discussed. The experimental findings support the idea that individual ceramic tablets, comprising the nacre, are built of the compositionally and functionally graded ceramic material. This sheds additional light on the origin ofthe superior mechanical properties of biogenic composites.

We report on metal-organic chemical vapor deposition (MOCVD) of the Ba x Sr 1 − x TiO 3 (BST) films (with x ≈ 0.5) on SrTiO 3 substrates. This research comprises the development of new chemical precursors, modification of the MOCVD apparatus towards stoichiometric oxide growth and undesirable phase suppression, as well as establishing optimum growth conditions. The grown BST films were characterized by the set of experimental techniques, including high-resolution X-ray diffraction (HRXRD) and high-resolution scanning electron microscopy. The newly synthesized organo-metallic precursors exhibit better properties than the available precursors and, in particular, show low melting points of about 80 °C. By using these precursors, we succeeded to grow sub-micron thick BST films of high crystalline quality. Optimum growth temperature was found to be 740 °C. The symmetric and asymmetric HRXRD profiles, as well as wide-angle X-ray diffraction scans, taken from the films grown under optimal conditions, reveal epitaxial orientation relations between the film and the substrate.

Internal strain/stresses in the nacre layer of mollusk shells are measured as a function of depth under controlled etching in selected areas. We found strain release to be enhanced when approaching the inner surface of the shell adjacent to the mollusk mantle. Strain distribution across the thickness of the shell consists of two components: a slowly changing component, which reflects elastic bending of the shell; and a short-range periodic modulation due to forces acting at interfaces between ceramic lamella. Simulations based on the multilayer structure model reproduce well the main features of the obtained experimental data.

8 pages; International audience; We used high-resolution neutron powder diffraction to accurately measure the atomic positions and bond lengths in biogenic and geological calcite. A special procedure for data analysis was developed in order to take into account the considerable amounts of magnesium present in all the investigated samples. As a result, in biogenic calcite we found some atomic bonds to have significantly different lengths as compared to those in geological calcite, after the contribution of magnesium is accounted for. The maximum effect (elongation up to 0.7%) was found for the C−O bonds. We also analyzed changes in frequencies and spectral widths of normal vibrations of carbonate groups in biogenic calcite (as compared to geological calcite) measured by Raman and Fourier transform IR techniques. Surprisingly, the frequency shifts after subtracting the magnesium contribution are close to zero. At the same time, substantial spectral broadening (up to 1.2%) in biogenic calcite as compared to geological samples was detected. Possible explanations for the experimental findings are discussed.

We use high-resolution X-ray diffraction and high-resolution transmission electron microscopy in order to study the strain state, atomic intermixing and layer thicknesses in the MBE-grown GaSb/InSb/InAs/InSb superlattices. Simple and fast metrology procedure is developed, which allows us to obtain the most important technological parameters, such as the thicknesses of the GaSb, InAs and ultra-thin InSb sub-layers, the superlattice period and the fraction of atomic substitutions in the InSb sub-layers.

Novel barium and strontium precursors, belonging to the family of volatile complexes of the alkaline earth element (AEE) fluorinated β-diketonates with polyglymes, [M(dfhd)2(tetraglyme)] [Hdfnd = 1,1,1,2,2,6,6,7,7,7-dekafluoro-heptane-3,5-dione, M = Ba (I), Sr (II)], are synthesized and tested with an aim to use them for metal-organic (MO)CVD of BaxSr1-xTiO3 (BST) thin films. The thermal behavior and composition of vapor phases for compounds I and II are studied by thermal analysis and mass spectrometry (MS). Considerable reduction of the melting point (down to 80–90 °C) for both compounds I and II, as compared to known volatile complexes, is achieved. By means of the developed precursors, epitaxial BST films (x = 0.5) are grown on SrTiO3 substrates by using the modified MOCVD facility. The quality of the grown films is examined by high-resolution (HR) X-ray diffraction (XRD) and high-resolution (HR) scanning electron microscopy (SEM).

We used high-resolution neutron powder diffraction technique in order to accurately measure the atomic positions and bond lengths in calcium carbonates of biogenic (mollusk-made) and geological origin. As a result, in biogenic calcium carbonate we identified atomic bonds, first of all the C O bonds and some O O bonds, which obey significant modification (about 1%) with respect to those in geological calcium carbonate. Bond length changes are presumably due to the organic/inorganic interactions in natural bio-composites. Generally, the effect is more pronounced for aragonite, which is structurally more flexible (nine unfixed parameters in atomic positions) than calcite (one parameter of this kind only). The observed bond modifications can be a source of the reported changes in the frequencies of normal vibrations of the carbonate groups measured by Raman or Fourier-transform infrared spectroscopy (FTIR) techniques.

An analytic expression has been derived connecting the degree of preferred orientation in a polycrystalline material to the March parameter. The latter defines the spread of angular distribution of crystallite inclinations in the March–Dollase approach [March (1932).Z. Kristallogr.81, 285–297; Dollase (1986).J. Appl. Cryst.19, 267–272]. In turn, the March parameter can be extracted from experimental data using either the Rietveld refinement of the entire diffraction pattern or the measurement of two diffraction intensities originating in the selected crystallographic planes. Working examples taken with two different types of samples are presented.

How do living organisms attain the complicated shapes of grown bio-composites? This question is answered when studying the mechanics of the nacre layer in the bivalve mollusk shells. In this study, the internal strains/ stresses across the shell thickness are profiled as a function of depth by strain gauge measurements during controlled etching in the selected areas. Measurements of stress release under etching provide clear evidence that the investigated shells, in fact, are strained multilayered structures, which are elastically bent due to the forces evolving at the organic/inorganic interfaces. The stresses are mostly concentrated in the "fresh" nacre sub-layers near the inner surface of the shell adjacent to the mollusk mantle. This analysis unexpectedly shows that the elastic bending of the nacre layer is due to strain gradients which are originated in the gradual in-depth changes of the thickness of ceramic lamellae. The changes mentioned were directly observed by scanning electron microscopy. By this sophisticated design of the ultra-structure of the nacre layer, the bowed shape of the bivalve shells is apparently achieved.

Energy-variable X-ray diffraction technique is further established as a novel method for depth-resolved measurements of residual strains in polycrystalline multilayers. Depth sensitivity is achieved by the controlled varying of the X-ray energy and, hence, X-ray penetration into the sample. In this paper, we develop analytical expression for the energy-dependent shape of the diffraction profile taken from a polycrystalline multilayer. We show that the maximum diffraction intensity recorded in the detector originates at a characteristic depth, Zc, which strongly depends on the X-ray penetration length, as in the case of homogeneous material considered in detail in our earlier publications [E. Zolotoyabko et al. J. Synchrotron Radiation 11 (2004) 309; Nucl. Instr. & Meth. Phys. Res. B 246, (2006) 244]. The multilayer periodicity only weakly influences the previously derived expressions for Zc. The accomplished analysis provides theoretical basis of using the energy-variable diffraction in polycrystalline multilayers. We apply this technique for characterizing the alumina/Ni samples produced by high-temperature diffusion bonding.

Dentin in teeth is a bone-like nanocomposite built of carbonated hydroxyapatite (cHAP) mineral particles, protein and water that does not remodel nor heal. It is assumed to be excellently adapted for decades of mechanical function, due to the interplay between its constituents. Using samples of human origin, we combine heat treatments with synchrotron X-ray diffraction, second-harmonic generation microscopy, Raman spectroscopy, and phase contrast-enhanced nano-tomography to study the water-assisted functional coupling of the biocomposite components. Across roots we find a gradual reduction in the c-lattice parameter of the cHAP nano-crystals, from 6.894 Å externally down to 6.885 Å in deeper tooth regions. Here, approaching the pulp, tissue is formed at later stages of tooth development. In all regions, a compressive strain of ~0.3 % is observed upon drying by mild heating (125 ºC). Dehydration results in a substantial increase in the averaged microstrain fluctuations in the mineral nanoparticles. The mineral crystallite platelet lengths fall off from ~36 nm externally to ~26 nm closer to the pulp. Our results suggest that both morphology and mineral-collagen coupling allow mineral nano-particles in dentin to sustain rather large stresses of 300 MPa, far exceeding mastication stresses, and that such loads are sustained through durable collagen fibril contractions.

By using high-resolution X-ray powder diffraction at a dedicated synchrotron beam line, ID-31, of the European Synchrotron Radiation Facility (ESRF, Grenoble, France), we studied structural and microstructural modifications in biogenic aragonite crystals, obtained from mollusk shells, and subjected to heat treatments at elevated temperatures. All investigated shells revealed anisotropic lattice distortions of the orthorhombic unit cell as compared to geological aragonite. Annealing at temperatures above 150−200 °C led to pronounced lattice relaxation which is accompanied by a substantial reduction of crystallite sizes and related growth of microstrain fluctuations. These findings indicate that biogenic aragonite crystals are strained, apparently, as a result of the amorphous/crystalline phase transformation, which proceeds within the supporting network of oriented biomacromolecules at early stages of biomineralization.

Atomic positions in geological aragonite and biogenic aragonite, obtained from several mollusk shells, were precisely measured by high-resolution neutron diffraction, which is more sensitive than X-ray diffraction to the positions of light atoms, C and O, in the CaCO3 structure. Comparable analysis of atomic positions revealed, for the first time, the changes in some bond lengths and atomic configurations in biogenic specimens with respect to geological ones. Most pronounced are modifications in the aplanarity of the carbonate groups. These modifications correlate with the observed shifts of the ν2 frequency in the IR absorption spectra. The changes in atomic positions as well as the changes in lattice parameters detected by high-resolution X-ray diffraction are attributed to the interaction between organic macromolecules and growing crystallites during biomineralization. The obtained results allow us deeper understanding of the specific routes used by nature for growing bio-composites with superior chara...

Rapid thermal MOCVD technique was adopted and applied for growing epitaxial films of BaTiO 3 on MgO substrates. A detailed description of modified experimental set-up design is given. Major modifications are towards optimizing the sources and gas lines. A new barium metal-organic precursor was developed on the basis of mixed ligand complexes of barium β-diketonates. Testing procedures showed that the developed precursor offers the advantages of low melting temperature, good volatility and ease of synthesis and handling. Grown layers were characterized by low and high resolution X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectrometry in SEM in order to obtain information on structural quality, surface morphology and composition.

The formation mechanism of a perfectly ordered protein/silica structure in the axial filament of the anchor spicule of the silica sponge Monorhaphis chuni is suggested. Experimental evidence shows that the growth of this architecture is realized by a thermodynamically driven dislocation-mediated spiral growth mechanism, resulting in a specific rotation of the mesoscopic crystal lattice (Eshelby twist).

Tooth dentine and other bone-like materials contain carbonated hydroxyapatite nanoparticles within a network of collagen fibrils. It is widely assumed that the elastic properties of biogenic hydroxyapatites are identical to those of geological apatite. By applying hydrostatic pressure and by in situ measurements of the a- and c- lattice parameters using high energy X-ray diffraction, we characterize the anisotropic deformability of the mineral in the crowns and roots of teeth. The collected data allowed us to calculate the bulk modulus and to derive precise estimates of Young׳s moduli and Poisson׳s ratios of the biogenic mineral particles. The results show that the dentine apatite particles are about 20% less stiff than geological and synthetic apatites and that the mineral has an average bulk modulus K=82.7 GPa. A 5% anisotropy is observed in the derived values of Young׳s moduli, with E11≈91 GPa and E33≈96 GPa, indicating that the nanoparticles are only slightly stiffer along their long axis. Poisson׳s ratio spans ν≈0.30–0.35, as expected. Our findings suggest that the carbonated nanoparticles of biogenic apatite are significantly softer than previously thought and that their elastic properties can be considered to be nearly isotropic.

A novel algorithm for the simulation of the X-ray diffraction profiles in multilayers is developed, which can be applied to any multilayered structure, with no limitations. The simulation program in the MATLAB format is based on the direct summation of waves scattered by individual atomic planes. It takes into account the strain and concentration-induced fluctuations of interplanar spacings, interface roughness and buried amorphous layers, and enables adding the diffuse scattering contributions of the Gaussian or Lorentzian types. The summation over individual layers can be done coherently or incoherently, depending on the interface structure. In order to visualize the steps of the fitting procedure, the contribution of each layer can be plotted separately. In this paper the simulation routine is described with a focus on handling asymmetric reflections. We stress that in this case, the effective thickness of the layers, participating in the formation of diffraction signals, can be very different for low or high X-ray incidence angles. We also show that in contrast to symmetric reflections, when treating the asymmetric ones, an additional phase shift depending on the distance between the sample and detector, should be taken into account. The simulation program is applied to fit experimental diffraction profiles, symmetric and asymmetric, taken from the MOVPE-grown heterostructures and superlattices of practical importance, based on the InGaAsP/InP materials system.

An energy-variable synchrotron diffraction technique is established as a novel method for the depth-resolved measurement of d-spacings and residual strains in polycrystalline films. Depth sensitivity is achieved by the controlled varying of the X-ray energy and, hence, X-ray penetration into the sample. In this paper, an analytical expression for the energy-dependent shape of the diffraction peak taken from a polycrystalline thin film is given. We show that the maximum diffraction intensity recorded in the detector originates at a certain depth, which is composed of the film thickness and the X-ray penetration length. This finding opens a way for strain measurements with high depth resolution by varying the X-ray energy and, as a result, the X-ray penetration, in small enough steps. The technique developed is applied to the characterization of thin-film Co/Cu multilayers produced by electro-deposition. Strain variations with spatial periodicity of the order of 100 nm are clearly seen. An ability to collect experimental data in steps of 10 nm when working not far away from absorption edges is demonstrated.

In this paper, we present experimental results demonstrating systematic structural distinctions between biogenic and non-biogenic calcium carbonate. Specifically we show, by high-resolution X-ray powder diffraction on dedicated synchrotron beam lines, that the orthorhombic unit cell of the mollusk-made aragonite is anisotropically distorted as compared with that one of geological aragonite. In all investigated shells, belonging to different classes (bivalve, gastropod, and cephalopod) and taken from different habitat origins (sea, fresh water, and land), the maximum elongation of about 0.1-0.2% was found along the c-axis. The lattice distortions along the a-axis were also of the positive sign (elongation) but lower than those along the c-axis, whereas lattice distortions along the b-axis were always negative (contraction). Supporting experiments, including structural analysis after a bleach procedure, measurements of temperature-dependent lattice relaxation, measurements of the CO(2) release at elevated temperatures, signify that the observed structural distinctions are most probably caused by the organic molecules intercalating into the aragonite lattice during biomineralization. Our findings show that in some sense organisms control the atomic structure of the crystals. Deeper understanding of this phenomenon will aid in the development of new approaches to grow biomimetic composites and tailor their properties on a molecular level.

A 40 kD protein has been extracted from the biomineral matrix of the calcium carbonate gastropod shell of Strombus decorus persicus. The protein was isolated by decalcification and ion exchange HPLC. We have named this protein ACLS40, i.e., aragonite crossed-lamellar structure protein. A partial sequence of the isolated ACLS40 and amino acid analysis both indicate that it does not belong to the family of very acidic proteins, i.e., rich in aspartic and glutamic residues. The shell-extracted protein shows the ability to stabilize calcium carbonate in vitro, in the form of thermodynamically unstable vaterite polymorph, and to inhibit the growth of calcite.

High-resolution x-ray diffraction and high-resolution scanning electron microscopy have been applied to characterize BaTiO 3 films of different thicknesses, metal-organic chemical vapour deposition grown on MgO substrates. We found a strong correlation between the strain state of the films and the amount of specific material discontinuities, the latter serving as an effective channel of strain relaxation. The results obtained are explained by considering the structural misfit arising at the interface between in-plane oriented 90° domains.

A novel simulation program in the MATLAB format for x-ray diffraction profiles in multilayers was developed, which can be applied to any multilayered structure with no limitations. The simulation algorithm (nickname DIWAS) is based on direct summation of waves, scattered by individual atomic planes. It takes into account strain and concentration-induced fluctuations of interplanar spacings, interface roughness and buried amorphous layers, and enables the addition of diffuse scattering profiles.The program allows handling of asymmetric reflections as well as symmetric ones, taking special care of the effective layer thickness. The summation over individual layers can be done coherently or incoherently, depending on the interface structure. To make the fitting procedure comprehensible, the contribution of every layer can be plotted separately.In this paper, the direct wave summation (DIWAS) routine is described in detail and is applied to fit experimental diffraction profiles taken from MOVPE grown heterostructures and superlattices of practical importance, such as InGaN/GaN/AlGaN/sapphire, GaAsN/GaAs, InGaAsP/InP and InGaAs/InP.

Interrelations between the degree of uniaxial preferred orientation and the intensities and widths of selected X-ray diffraction peaks are analyzed within the March–Dollase approach. Simple analytical expressions are developed which relate the degree of preferred orientation to the rocking curve width of the strongest diffraction peak or the intensity ratio of two diffraction peaks, one of them being originated in the preferably orientated atomic planes.

An energy-variable synchrotron diffraction technique is being established as a novel method for the depth-resolved measurement of residual strains in polycrystalline structures. An analytic expression for the diffraction profile is obtained by taking into account the instrument misalignment, change of the height of an incident X-ray beam with energy, and penetration of X-rays into the sample depth. It is shown that the maximum diffraction intensity recorded in the detector is coming from a certain depth beneath the surface of the sample, the depth being energy-dependent. This finding opens a way for precise strain measurements with high depth resolution by changing the X-ray energy in small enough steps. An experimental example, residual strain measurements across an alumina/zirconia multilayer, demonstrates the capability of the method.

Nanocrystalline carbon films possessing a prevailing diamond or graphite character, depending on substrate temperature, can be deposited from a methane hydrogen mixture by the direct current glow discharge plasma chemical vapor deposition method. While at a temperature of ∼880 °C, following the formation of a thin precursor graphitic film, diamond nucleation occurs and a nanodiamond film grows, at higher and lower deposition temperatures the films maintain their graphitic character. In this study the hydrogen content, density and nanocrystalline phase composition of films deposited at various temperatures are investigated. We aim to elucidate the role of hydrogen in nanocrystalline films with a predominant diamond character. Secondary ion mass spectroscopy revealed a considerable increase of the hydrogen concentration in the films that accompanies the growth of nanodiamond. It correlates with near edge x-ray adsorption spectroscopy measurements, that showed an appearance of spectroscopic features associat...

The three-dimensional microstructure of a Strombus decorus persicus seashell was studied by means of high-resolution electron microscopy and energy-variable X-ray diffraction on synchrotron beam lines. Energy variation in small steps allows the X-ray penetration depth to be changed precisely and, on this basis, for a non-destructive microstructural analysis with depth resolution to be developed. This technique enabled determination of depth-resolved microstructural parameters, such as the degree of the preferred orientation, the lamella size, and average microstrain fluctuations in both the prismatic and the crossed-lamellar layers of these seashells. The X-ray results were in good agreement with direct observations made by electron microscopy. A detailed study of the shell microstructure shed additional light on the relationship between the structural characteristics and superior mechanical properties of seashells.

The pulsed synchrotron radiation from the Advanced Photon Source at Argonne National Laboratory was used to stroboscopically measure the dynamic response of BaTiO 3 ferroelectric films, in situ, under the application of a high-frequency electric field. The time-dependent lattice d -spacings measured in the frequency range, 25-1300 MHz, demonstrated both periodicity and attenuation features which were attributed to domain dynamics. Drastic (two order of magnitude) reduction of the relaxation time (i.e., attenuation increase) was found with increasing electric field frequency. Experimental findings are analyzed in terms of hindering of domain wall motion by generated deformation waves.

A depth-sensitive X-ray diffraction technique has been developed with the aim of studying microstructural modifications in inhomogeneous polycrystalline materials. In that method, diffraction profiles are measured at different X-ray energies varied by small steps. X-rays at higher energies probe deeper layers of material. Depth-resolved structural information is retrieved by comparing energy-dependent diffraction profiles. The method provides non-destructive depth profiling of the preferred orientation, grain size, microstrain fluctuations and residual strains. This technique is applied to the characterization of seashells. Similarly, energy-variable X-ray diffraction can be used for the non-destructive characterization of different laminated structures and composite materials.