Scanning Synchrotron Research Articles

Heterogeneous Nucleation Effects of Talc Particles on Polymorphic Crystallization of Cocoa Butter

Polymorphic crystallization of cocoa butter (CB) in a bulk system was examined for the influence of adding talc particles at different concentrations (0.1–5%). While the system was cooled from the melt and subsequently heated, changes in the heat flow and crystal structure of CB were analyzed using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD). Synchrotron radiation microbeam X-ray diffraction (SR-μ-XRD) was employed to determine lamellar-plane directions of CB crystals occurring with talc addition. At any cooling rates (0.1–15 °C/min) applied, talc promoted CB crystallization to elevate the onset crystallization temperature logarithmically with the increasing concentration of talc; this effect became more prominent at higher cooling rates. Talc also acted as a polymorphic stabilizer so that CB crystallized in more stable forms even when cooled at highest rate of 15 °C/min. Moreover, a highly ordered lamellar-plane direction was extensively observed for CB crystals occurring with 0.1% talc addition, which was disturbed by 0.5% talc addition probably due to the spatial dispersion of densely populated talc particles in their randomized orientation. These heterogeneous nucleation effects indicate the potential of talc particles to be used for the quality and productivity control of CB-based products.

Postcrania of Borealestes (Mammaliformes, Docodonta) and the emergence of ecomorphological diversity in early mammals

AbstractThe Middle Jurassic witnessed the early diversification of mammal groups, including the stem‐mammalian clade, Docodonta. Recent discoveries in China indicate docodontans exhibited ecomorphological diversity akin to small‐bodied mammals living >100 million years later, in the Cenozoic. Our understanding of the emergence of this ecological diversity is hindered by a lack of Middle Jurassic fossil material from other parts of the world. The two partial postcranial skeletons of Borealestes described here come from the Kilmaluag Formation, Scotland. These are the most complete Mesozoic mammaliaform skeletons currently known from the UK, and among the best preserved in Europe. As an early member of Docodonta, Borealestes provides key anatomical information for understanding the clade’s evolution, and the emergence of mammaliaform ecomorphological diversity. Using digital reconstructions from micro‐CT and synchrotron scans, we describe the postcranial anatomy of Borealestes and provide an updated phylogenetic analysis incorporating cranial and postcranial characters. We find Borealestes species form a sister group to a clade comprising Agilodocodon and Microdocodon. To complement observational analyses of the skeleton, we carry out principal components analyses using 3D landmarks on a comparative dataset of 42 extant mammal taxa. Our results indicate Borealestes lacked specializations for derived locomotor behaviour. We detect some similarity in the humerus between Borealestes and Ornithorhynchus. Borealestes is morphologically intermediate between the robust morphology of fossorial and semi‐fossorial/semi‐aquatic Haldanodon and Docofossor, and the gracile morphology for scansorial Agilodocodon and Microdocodon. We suggest ecological diversity in Docodonta may arise from an unspecialized basal bauplan, of which Borealestes may be representative.

The role of water in the reversibility of thermal denaturation of lysozyme in solid and liquid states

Although unfolding of protein in the liquid state is relatively well studied, its mechanisms in the solid state, are much less understood. We evaluated the reversibility of thermal unfolding of lysozyme with respect to the water content using a combination of thermodynamic and structural techniques such as differential scanning calorimetry, synchrotron small and wide-angle X-ray scattering (SWAXS) and Raman spectroscopy. Analysis of the endothermic thermal transition obtained by DSC scans showed three distinct unfolding behaviors at different water contents. Using SWAXS and Raman spectroscopy, we investigated reversibility of the unfolding for each hydration regime for various structural levels including overall molecular shape, secondary structure, hydrophobic and hydrogen bonding interactions. In the substantially dehydrated state below 37 wt% of water the unfolding is an irreversible process and can be described by a kinetic approach; above 60 wt% the process is reversible, and the thermodynamic equilibrium approach is applied. In the intermediate range of water contents between 37 wt% and 60 wt%, the system is phase separated and the thermal denaturation involves two processes: melting of protein crystals and unfolding of protein molecules. A phase diagram of thermal unfolding/denaturation in lysozyme - water system was constructed based on the experimental data.

Investigation of breakaway corrosion observed during oxide growth in pure and low alloying element content Zr exposed in water at 360°C

The addition of small concentrations of alloying elements to pure zirconium can prevent nuclear fuel cladding material from undergoing unstable oxide growth in aqueous environments at light water reactor operating temperatures. The role of alloying elements in stabilizing the oxide growth is examined in this paper, to better understand the oxide growth stabilization mechanism. To this end, a set of initial, short-duration corrosion experiments were performed, followed by oxide layer characterization. Specifically, ten model Zr alloys were selected to test the effect of small alloying additions on the alloy corrosion rate and corrosion breakaway. These alloys were corrosion tested in pure water in an autoclave at 360 °C for up to 70 days. The alloys included crystal bar Zr, sponge Zr, and model alloys with small concentrations of Sn, Fe, and Cr. After testing, the alloys were characterized using scanning electron microscopy (SEM) and synchrotron µ-X-ray fluorescence (µXRF) to study how the structure of the oxide and alloying element distribution related to unstable oxide growth. Initial results in the 360 °C water environment showed breakaway oxidation may be caused by unstable oxide growth due to heterogeneous distribution of the alloying elements. Heterogeneous distribution of alloying elements was correlated to the occurrence of unstable oxide growth (either nodule-like, grain boundary penetration, or differential grain-to-grain growth). It is possible that this heterogeneity, made possible by low alloying element content, can cause breakaway corrosion, but further study is warranted.

X-Ray Spectromicroscopy Investigation of Heterogeneous Sodiation in Hard Carbon Nanosheets with Vertically Oriented (002) Planes.

Hard carbon (HC) is a promising anode material for sodium-ion batteries, but the performance remains unsatisfactory and the sodiation mechanism in HC is one of the most debated topics. Here, from self-assembled cellulose nanocrystal sheets with crystallographic texture, unique HC nanosheets with vertically oriented (002) planes are fabricated and used as a model HC to investigate the sodiation mechanisms using synchrotron scanning transmission X-ray microscopy (STXM) coupled with analytical transmission electron microscopy (TEM). The model HC simplifies the 3D sodiation in a typical HC particle into a 2D sodiation, which facilitates the visualization of phase transformation at different states of charge. The results for the first time unveil that the sodiation in HC initiates heterogeneously, with multiple propagation fronts proceeding simultaneously, eventually merging into larger aggregates. The spatial correlation between the preferential adsorption and nucleation sites suggests that the heterogeneous nucleation is driven by the local Na-ion concentration, which is determined by defects or heteroatoms that have strong binding to Na ions. By identifying intercalation as the dominant sodium storage mechanism in the model HC, the findings highlight the importance of engineering the graphene layer orientation and the structural heterogeneity of edge sites to enhance the performances.

Diamond formation from methane hydrate under the internal conditions of giant icy planets

Hydrocarbon chemistry in the C–O–H system at high pressure and high temperature is important for modelling the internal structure and evolution of giant icy planets, such as Uranus and Neptune, as their interiors are thought to be mainly composed of water and methane. In particular, the formation of diamond from the simplest hydrocarbon, i.e., methane, under the internal conditions of these planets has been discussed for nearly 40 years. Here, we demonstrate the formation of diamond from methane hydrate up to 3800 K and 45 GPa using a CO2 laser-heated diamond anvil cell combined with synchrotron X-ray diffraction, Raman spectroscopy, and scanning electron microscopy observations. The results show that the process of dissociation and polymerisation of methane molecules to produce heavier hydrocarbons while releasing hydrogen to ultimately form diamond proceeds at milder temperatures (~ 1600 K) and pressures (13–45 GPa) in the C–O–H system than in the C–H system due to the influence of water. Our findings suggest that diamond formation can also occur in the upper parts of the icy mantles of giant icy planets.

Enabling curvable silicon photovoltaics technology using polycarbonate-sandwiched laminate design

Cracks in brittle silicon solar cells (wafers) are a major concern in the solar photovoltaics (PV) industry. Because of the slicing of the wafers from large ingots and further stressing during subsequent operations such as soldering and laser cutting, silicon (Si) solar cells often contain microcracks that may grow into larger cracks during cell integration into a PV module. Through our previous works on residual stress probing using synchrotron scanning X-ray microdiffraction (μSXRD) experiments, finite-element modelling of the manufacturing sequences (from cells to laminate) have been validated to predict the stresses highly accurately in the conventional PV module design (glass-cell-backsheet). In the present work, we use those validated finite element methodologies to predict the residual stresses in a novel PV module design in which silicon cells are sandwiched between polycarbonate (PC) sheets – the lightweight PC-cell-PC module. It is shown that the post-lamination residual stresses in the cells are highly compressive, which is good for inhibiting crack growth. This feature also enables the novel PV modules to be curved without the cells cracking, which favors its application to building-integrated or automotive-integrated PV modules. We demonstrate the basic feasibility of the concept – with mini curved PC-sandwiched laminates, showing the upper bounds of the achievable curvature (and their associated stress levels) without any observable cracks in the cells as determined by electroluminescence imaging. The curving here is utilized to demonstrate the larger extent of mechanical stresses the same silicon solar cells could withstand with the PC-PC design.

Effect of post-heat treatment on microstructure and mechanical properties of laser welded Al-Cu-Mg alloy

A new approach was developed to improve strength of Al-Cu-Mg alloy laser welded joints that typically within 61–90 % of that of the base metal due to a change in the microstructure and phase composition of the weld one. This result was achieved by optimization of post weld heat treatment (PWHT) included quenching and subsequent artificial aging. For the first time, the spatial distribution and evolution of the phase composition were studied at all PWHT stages using high-resolution scanning electron microscopy and synchrotron X-ray analysis. It was found that the Al-Cu-Mg solid solution was homogenized, as well as the S(Al2CuMg) strengthening and (partly) θ(Al2Cu) phases were formed. After PWHT, ultimate tensile strength was 428 MPa, yield strength was 302 MPa, and elongation was 19.6 %, which were 99 %, 98 % and 95 %, respectively, of those of the base metal.

Photophysical and structural modulation of poly(3-hexylthiophene) nanoparticles via surfactant-polymer interaction

The optical properties of poly(3-hexylthiophene-2,5-diyl) (P3HT) can be controlled by processing the polymer in the form of nanoparticles dispersed in aqueous mediums. Colloids of P3HT were prepared by two different methods: flash –or reprecipitation- and miniemulsion precipitation technique, which result in the latter case in a polymer-water system whose stability is mediated by an ionic surfactant. Both systems yield different color dispersions, thus different absorption spectra, that is explained to be caused by the influence of the surfactant on the structure of P3HT. Differential scanning calorimetry and synchrotron radiation X-ray diffraction experiments reveal the origin of these optical differences, showing evidences of the formation of a blended structure formed due to the interaction between P3HT and the ionic surfactant. This work evidences the potential use of techniques for preparing nanoparticles in water dispersions as a tool to manipulate the structure and thus, the optical properties of these materials.

An Improved Cleaning Protocol for Foraminiferal Calcite from Unconsolidated Core Sediments: HyPerCal—A New Practice for Micropaleontological and Paleoclimatic Proxies

Paleoclimatic and paleoceanographic studies routinely rely on the usage of foraminiferal calcite through faunal, morphometric and physico-chemical proxies. The application of such proxies presupposes the extraction and cleaning of these biomineralized components from ocean sediments in the most efficient way, a process which is often labor intensive and time consuming. In this respect, in this study we performed a systematic experiment for planktonic foraminiferal specimen cleaning using different chemical treatments and evaluated the resulting data of a Late Quaternary gravity core sample from the Aegean Sea. All cleaning procedures adopted here were made on the basis of their minimum potential bias upon foraminiferal proxies, such as the faunal assemblages, degree of fragmentation, stable isotope composition (δ18O and δ13C) and/or Mg/Ca ratios that are frequently used as proxies for surface-ocean climate parameters (e.g., sea surface temperature, sea surface salinity). Six different protocols were tested, involving washing, sieving, and chemical treatment of the samples with hydrogen peroxide and/or sodium hexametaphosphate (Calgon®). Single species foraminifera shell weighing was combined with high-resolution scanning electron microscopy (SEM) and synchrotron X-ray microtomography (SμCT) of the material processed by each of the cleaning protocols, in order to assess the decontamination degree of specimen’s ultrastructure and interior. It appeared that a good compromise between time and cleaning efficiency is the simultaneous treatment of samples with a mixed hydrogen peroxide and Calgon solution, while the most effective way to almost completely decontaminate the calcareous components from undesirable sedimentary material is a two-step treatment—initially with hydrogen peroxide and subsequently with Calgon solutions.

Binary Phase Behavior of 1,3-Distearoyl-2-oleoyl-sn-glycerol (SOS) and Trilaurin (LLL).

This paper reports the precise analysis of the eutectic mixing behavior of 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS) and trilaurin (LLL), as a typical model case of the mixture of cocoa butter (CB) and cocoa butter substitute (CBS). SOS was mixed with LLL at several mass fractions of LLL (wLLL); the mixtures obtained were analyzed for polymorphic phase behavior using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffractometry (SR-XRD). In melt crystallization with constant-rate cooling, SOS and LLL formed eutectics in their metastable polymorphs, allowing the occurrence of a compatible solid solution at wLLL ≥ 0.925. With subsequent heating, the resultant crystals transformed toward more stable polymorphs, then melted in a eutectic manner. For mixtures aged at 25 °C after melt crystallization, eutectics were found in the extended wLLL region, even at wLLL = 0.975. These results indicate that phase separation between SOS and LLL progressed in their solid solution under stabilization. The crystal growth of the separated SOS fraction may cause fat-bloom formation in compound chocolate containing CB and CBS. To solve this problem, the development of retardation techniques against phase separation is expected.

Mixing Ratio and Cooling Rate Dependence of Molecular Compound Formation in OPO/POP Binary Mixture.

Owing to the increasing reports of the harmful effects of trans and saturated fatty acids, the demand for trans- and saturated-fatty-acid-free oil and fat products is increasing among consumers. However, it is difficult to maintain the product stability and shape retention of such oil and fat products. As a result, there is a high demand in the processed oil and fat industry to develop solutions to such problems. Herein, we used molecular compound (MC) crystals in an attempt to find alternatives to trans and saturated fatty acids. The MCs used were 1,3-dioleoyl-2-palmitoyl-sn-glycerol (OPO) and 1,3-dipalmitoyl-2-oleoyl-sn-glycerol (POP)—the main components of lard and palm oil, respectively. We believe that OPO and POP can be used to obtain no-trans, low-saturation, and high-oleic-acid oil and fat products. Optimal conditions for efficient MC crystallization were examined by changing the oil and fat composition under rapid cooling conditions assuming industrial cooling process by using differential scanning calorimetry and synchrotron radiation time-resolved X-ray diffraction methods. It was concluded that the increase in OPO concentration destabilized MC formation, while the increase in POP concentration stabilized it under rapid cooling conditions. As a result, it was shown that MC crystals can be efficiently obtained by reducing the degree of POP supercooling.

Melloniflora, a New Extinct Multiparted Flower from the Early Cretaceous of Virginia, USA

Premise of research. The Puddledock mesofossil flora from Virginia is the richest source for studying structurally preserved plant fossils in the Early Cretaceous Potomac Group sequence. Together with other mesofossil floras from the Potomac Group and also from Portugal, it is key for direct assessment of the structure, relationships, and reproductive biology of early angiosperms. In this study, a new multiparted floral structure from the Puddledock locality is analyzed, and its phylogenetic relationships are discussed.Methodology. The fossil was extracted from unconsolidated clays and sands through sieving in water. Adhering sediment was removed using HF and HCl followed by rinsing in water. External and internal features were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Phylogenetic analyses were carried out by adding the features of the fossil flower to an existing morphological data set for extant angiosperms.Pivotal results. A new taxon, Melloniflora virginiensis gen. et sp. nov., is established on the basis of a small multiparted floral structure that has several series of free stamens (ca. 50) and carpels (21) borne on a flattened receptacle. Stamens have a broad, short base, and dehiscence is introrse. Ovules are borne in two rows on either side of the ventral suture of the carpels. Abundant secretory cells occur in all tissues. Melloniflora is related to extant early-diverging members of the Magnoliales but also has features found among extant taxa of other early-diverging angiosperm lineages such as Austrobaileyales.Conclusions. Melloniflora adds to the knowledge of plants related to extinct magnoliids from the Early Cretaceous. It shows a combination of features not seen in any extant taxon. Melloniflora contributes to the evidence of considerable extinct diversity at an early stage in angiosperm evolution, especially among clades that today are represented by only a few relatively species-poor lineages.

Catanthus, an Extinct Magnoliid Flower from the Early Cretaceous of Portugal

Premise of research. Early Cretaceous flowers recovered from Portugal and North America are some of the oldest and most informative angiosperm structures known. Analyses of this material provide a more direct basis for inferring floral structure and biology in early angiosperms than extrapolations based solely on extant taxa, and they have documented an unanticipated diversity of angiosperms, including the presence of many extinct forms, during the Early Cretaceous. The fossil flower described here from the Early Cretaceous of Portugal adds to the knowledge of this extinct diversity.Methodology. Coalified fossil flowers were extracted from unconsolidated sediments and cleaned with HF, HCl, and water. Details were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Phylogenetic relationships were evaluated by adding the fossil to a phylogenetic analysis of extant basal angiosperms based on morphological characters but constrained according to a topology based on molecular data.Pivotal results. A new genus and species, Catanthus dolichostemon, are described on the basis of the fossil flowers. The perianth consists of three thick sepal-like tepals in an outer whorl and six thinner petallike tepals in two inner whorls. The androecium consists of several whorls of stamens with long, broad filaments and anthers with extrorse dehiscence. Pollen is trichotomocolpate and possibly monocolpate. The gynoecium is superior and apocarpous, consisting of six or, rarely, five carpels. Analysis of the phylogenetic position of Catanthus suggests a relationship to Canellales and Magnoliales.Conclusions. Catanthus is a new Early Cretaceous magnoliid angiosperm for which the relationship to the two major clades of extant magnoliids (Laurales + Magnoliales or Canellales + Piperales) is not resolved securely. Catanthus adds to the evidence of substantial extinct diversity among early angiosperms, including the presence of extinct forms related to extant magnoliids, and it is consistent with a general pattern that angiosperm assemblages from the middle Albian and earlier are dominated by noneudicots.

Stepwise Synthesis of N–Ag–N and C–Ag–C Organometallic Structures on a Ag(111) Surface

Stepwise activation of N–H and C–Br bonds in bis-(4-bromophenyl)amine (BPA) on a Ag(111) surface has been studied with the aid of scanning tunneling microscopy (STM) and synchrotron radiation photo...

Vertically nanotwinned TiO2 photoanodes with enhanced charge transport for efficient solar water splitting

Nanotwinned crystals are highly desired for materials science and practical applications due to their various intriguing properties. In particular, a semiconducting photoanode with vertically aligned twin boundaries could simultaneously possess excellent charge separation and transport properties, but the synthesis remains a great challenge. Here, we report highly oriented rutile TiO2 nanotwin crystals grown on conducting substrates via a rapid hydrothermal method for the first time. The scanning synchrotron X-ray Laue nanodiffraction demonstrated that the twin boundaries in the film are strikingly perpendicular to the plane of the substrate. The nanotwin photoanode exhibited superior photoelectrochemical water oxidation activity mainly due to the massive improvement in the electrical transport. This work offers exciting opportunities for designing and fabricating new classes of ordered nanotwins.

Synchrotron micro-XRD study, the way toward a deeper characterizing the early prehistoric Iranian glass cylinders from Late Bronze Age (1280 BC)

In this article, the chemical and mineralogical composition of a unique glass cylinder obtained from the temple of Chogha-Zanbil and classified as the earliest glass discovered in Iran (2nd millennium BC) has been studied. This was achieved through the use of Fourier transform infrared spectroscopy, environmental scanning electron microscope and synchrotron X-ray micro-diffraction to characterize the presence of microstructures and the distribution of elements within their matrices. In order to accurately determine the characteristic crystalline phase constituents, micro-X-ray diffraction experiments were carried out at the CELLS-ALBA Synchrotron. Results reveal that the glass samples are comprised of silica glass and contain calcite, quartz and gehlenite as the major phases. The presence of argentojarosite as the Ag-bearing mineral within the amorphous part of glasses highlights the first use of Ag (Late Bronze Age) in Iran. The novelty of the results includes the identification of specific minerals (i.e., silver-containing minerals) used in the production of glass cylinders to obtain better luster and produce iridescence effects.

Increased Stability of Subsurface C Induced by Ca on the C-Incorporated Si(001)-4°-off Substrate

The effects of Ca atoms adsorbed on the C-incorporated Si(001)-4°-off substrate have been investigated by using scanning tunneling microscopy (STM) and synchrotron photoemission spectroscopy (PES). The C atoms incorporated into the subsurface by C2H2 exposure and postannealing at 630 °C induce the c(4 × 4) structure and debunch the double-layer DB steps. The Ca atoms additionally adsorbed on this C-incorporated substrate induce terraces with a width twice that of the clean surface. Until postannealing up to 680 °C, no SiC trace is detected. The SiC islands start to be detected after postannealing at 780 °C, which is about 100 °C higher than that for the identical surface without Ca atoms. After the adsorbed Ca atoms are mostly desorbed by 880 °C postannealing, the SiC islands only remain on the surface. Such a result implies that the adsorbed Ca atoms act as a stabilizer to the subsurface C atoms and increase the onset temperature of SiC formation by 100 °C.

Label‐Free Nanoimaging of Neuromelanin in the Brain by Soft X‐ray Spectromicroscopy

AbstractA hallmark of Parkinson's disease is the death of neuromelanin‐pigmented neurons, but the role of neuromelanin is unclear. The in situ characterization of neuromelanin remains dependent on detectable pigmentation, rather than direct quantification of neuromelanin. We show that direct, label‐free nanoscale visualization of neuromelanin and associated metal ions in human brain tissue can be achieved using synchrotron scanning transmission x‐ray microscopy (STXM), through a characteristic feature in the neuromelanin x‐ray absorption spectrum at 287.4 eV that is also present in iron‐free and iron‐laden synthetic neuromelanin. This is confirmed in consecutive brain sections by correlating STXM neuromelanin imaging with silver nitrate‐stained neuromelanin. Analysis suggests that the 1s–σ* (C−S) transition in benzothiazine groups accounts for this feature. This method illustrates the wider potential of STXM as a label‐free spectromicroscopy technique applicable to both organic and inorganic materials.

Label-Free Nanoimaging of Neuromelanin in the Brain by Soft X-ray Spectromicroscopy.

A hallmark of Parkinson's disease is the death of neuromelanin‐pigmented neurons, but the role of neuromelanin is unclear. The in situ characterization of neuromelanin remains dependent on detectable pigmentation, rather than direct quantification of neuromelanin. We show that direct, label‐free nanoscale visualization of neuromelanin and associated metal ions in human brain tissue can be achieved using synchrotron scanning transmission x‐ray microscopy (STXM), through a characteristic feature in the neuromelanin x‐ray absorption spectrum at 287.4 eV that is also present in iron‐free and iron‐laden synthetic neuromelanin. This is confirmed in consecutive brain sections by correlating STXM neuromelanin imaging with silver nitrate‐stained neuromelanin. Analysis suggests that the 1s–σ* (C−S) transition in benzothiazine groups accounts for this feature. This method illustrates the wider potential of STXM as a label‐free spectromicroscopy technique applicable to both organic and inorganic materials.