Spatter during laser powder bed fusion(LPBF)can induce surface defects,impacting the fatigue performance of the fabricated components.Here,we reveal and explain the links between vapour depression shape and spatter dy...Spatter during laser powder bed fusion(LPBF)can induce surface defects,impacting the fatigue performance of the fabricated components.Here,we reveal and explain the links between vapour depression shape and spatter dynamics during LPBF of an Al-Fe-Zr aluminium alloy using high-speed synchrotron x-ray imaging.We quantify the number,trajectory angle,velocity,and kinetic energy of the spatter as a function of vapour depression zone/keyhole morphology under industry-relevant processing conditions.The depression zone/keyhole morphology was found to influence the spatter ejection angle in keyhole versus conduction melting modes:(i)the vapour-pressure driven plume in conduction mode with a quasi-semi-circular depression zone leads to backward spatter whereas;and(ii)the keyhole rear wall redirects the gas/vapour flow to cause vertical spatter ejection and rear rim droplet spatter.Increasing the opening of the keyhole or vapour depression zone can reduce entrainment of solid spatter.We discover a spatter-induced cavity mechanism in which small spatter particles are accelerated towards the powder bed after laser-spatter interaction,inducing powder denudation and cavities on the printed surface.By quantifying these laser-spatter interactions,we suggest a printing strategy for minimising defects and improving the surface quality of LPBF parts.展开更多
The 4-alkoxybenzoic acids are well-known liquid crystals showing several mesophases (nematic, smectic C phase or both) depending on the alkoxy chain length and whereby the rigid core of the mesogen is formed by interm...The 4-alkoxybenzoic acids are well-known liquid crystals showing several mesophases (nematic, smectic C phase or both) depending on the alkoxy chain length and whereby the rigid core of the mesogen is formed by intermolecular hydrogen bonds. In this paper it is shown that the thermal behaviour of lanthanide salts of 4-hexyloxybenzoic acids depends on the lanthanide ion (Ln=La, Pr, Nd, Sm, Eu). The lanthanum(Ⅲ) and praseodymium(Ⅲ) 4-hexyloxybenzoates exhibit a smectic A mesophase. No mesophase is found for the corresponding compounds of heavier lanthanides. The thermal properties of the lanthanide(Ⅲ) 4-hexyloxybenzoates were investigated by differential scanning calorimetry (DSC), polarising thermo-optical microscopy and synchrotron X-ray radiation.展开更多
The code benchmarking for hadron linac using the 3D Particle-In-Cell (PIC) code is an important task in the European framework “High Intensity Pulsed Proton Injector” (HIPPI). PARMILA and HALODYN are two of the code...The code benchmarking for hadron linac using the 3D Particle-In-Cell (PIC) code is an important task in the European framework “High Intensity Pulsed Proton Injector” (HIPPI). PARMILA and HALODYN are two of the codes involved in this work. Both of these codes have been developed and used for linac design and beam dynamics studies. In this paper, the simulation results of the beam dynamics were compared and analyzed. As predicted by two codes, the simulation results show some agreements. The physical design strategy which was adopted in two codes was also discussed.展开更多
Calcium hydroxide nanoparticles in aqueous suspensions (also called nanolime) were successfully employed in Cultural Heritage conservation thanks to the ability of favoring readhesion of the pictorial layer on origina...Calcium hydroxide nanoparticles in aqueous suspensions (also called nanolime) were successfully employed in Cultural Heritage conservation thanks to the ability of favoring readhesion of the pictorial layer on original carbonatic substrates or allowing to a better superficial cohesion and protection of treated stones. In this work, we have synthesized nanolime particles in aqueous suspension by two different methods. The produced particles were characterized in the laboratory, in terms of structural and morphological features, by means of X-Ray diffraction powder (XRD) and by transmission electron microscopy (TEM), respectively. Nanoparticles were crystalline, regularly shaped, hexagonally plated and with side dimensions generally ranging from 300 nm to 30 nm or less. Crystal structure of nanolime particles directly in the aqueous suspension, has been also analyzed by synchrotron diffraction from X-ray synchrotron radiation (SR-XRD);data have been analyzed by means of the Rietveld method and we have investigated the structure of Ca(OH)2 particles in suspension in terms of cell parameters, atomic coordinates, bond lengths and angles.展开更多
BACKGROUND The enteric nervous system(ENS)is situated along the entire gastrointestinal tract and is divided into myenteric and submucosal plexuses in the small and large intestines.The ENS consists of neurons,glial c...BACKGROUND The enteric nervous system(ENS)is situated along the entire gastrointestinal tract and is divided into myenteric and submucosal plexuses in the small and large intestines.The ENS consists of neurons,glial cells,and nerves assembled into ganglia,surrounded by telocytes,interstitial cells of Cajal,and connective tissue.Owing to the complex spatial organization of several interconnections with nerve fascicles,the ENS is difficult to examine in conventional histological sections of 3-5μm.AIM To examine human ileum full-thickness biopsies using X-ray phase-contrast nanotomography without prior staining to visualize the ENS.METHODS Six patients were diagnosed with gastrointestinal dysmotility and neuropathy based on routine clinical and histopathological examinations.As controls,fullthickness biopsies were collected from healthy resection ileal regions after hemicolectomy for right colon malignancy.From the paraffin blocks,4-μm thick sections were prepared and stained with hematoxylin and eosin for localization of the myenteric ganglia under a light microscope.A 1-mm punch biopsy(up to 1 cm in length)centered on the myenteric plexus was taken and placed into a Kapton®tube for mounting in the subsequent investigation.X-ray phase-contrast tomography was performed using two custom-designed laboratory setups with micrometer resolution for overview scanning.Subsequently,selected regions of interest were scanned at a synchrotron-based end-station,and high-resolution slices were reported.In total,more than 6000 virtual slices were analyzed from nine samples.RESULTS In the overview scans,the general architecture and quality of the samples were studied,and the myenteric plexus was localized.High-resolution scans revealed details,including the ganglia,interganglional nerve fascicles,and surrounding tissue.The ganglia were irregular in shape and contained neurons and glial cells.Spindle-shaped cells with very thin cellular projections could be observed on the surface of the ganglia,which appeared to build a network.In the patients,there were no alterations in the general architecture of the myenteric ganglia.Nevertheless,several pathological changes were observed,including vacuolar degeneration,autophagic activity,the appearance of sequestosomes,chromatolysis,and apoptosis.Furthermore,possible expulsion of pyknotic neurons and defects in the covering cellular network could be observed in serial slices.These changes partly corresponded to previous light microscopy findings.CONCLUSION The analysis of serial virtual slices could provide new information that cannot be obtained by classical light microscopy.The advantages,disadvantages,and future possibilities of this method are also discussed.展开更多
Platinum-palladium nanoparticles are synthesized and characterized with regard to their application in fuel cells due to their high (electro) catalytic activity. Different preparation times are applied leading to diff...Platinum-palladium nanoparticles are synthesized and characterized with regard to their application in fuel cells due to their high (electro) catalytic activity. Different preparation times are applied leading to different structures, from Pd cubic to core-shell PtPd concave, and different chemical compositions. The resulting particles are studied via Transmission Electron Microscopy (TEM) and in-situ X-ray absorption fine structure (XAFS) measurements. The latter allows the investigation of the oxygen reduction reaction following the variations with varying applied potentials by analysis using the Iterative Transformation Factor Analysis (ITFA) and the creation of a two-component system that consists of metallic Pt-Pd and the related oxide. With the used model, the different concentrations of the oxide are linked to the consecutive chemical steps of the oxygen reduction reaction. Finally, the catalytic activity of the particles is determined via linear scanning voltammetry and reveals a dependence on the shape and the composition of the particles.展开更多
The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used...The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.展开更多
Enabling the use of rationally designed thin films in technological devices is a recognized goal in materials science. However, constructing such thin films using highly ordered supramolecular architectures with well-...Enabling the use of rationally designed thin films in technological devices is a recognized goal in materials science. However, constructing such thin films using highly ordered supramolecular architectures with well-controlled size and growth direction has remained an elusive target. Here, we introduce a layer-by- layer protocol to grow hybrid thin films of molecule-based magnetic conductors comprising arachidic acid and donor bis（ethylenedioxy）tetrathiafulvalene （BEDO-TTF） as the organic component and Cu/Gd complexes as the inorganic component. The construction of layered hybrid thin films was achieved at ambient conditions by employing the Langmuir-Blodgett method, which provides good control over film thickness and packing of molecules in the monolayer. As demonstrated by X-ray diffraction, these films are crystalline with distinct organic and inorganic sublattices, where the BEDO-TTF molecular layer is interfaced with the inorganic layer. Due to the flexibility of the Langmuir-Blodgett deposition technique, this result indicates a route toward the preparation of well-ordered films with various functionalities, determined by the choice of the inorganic compound that is combined with the π-unit of BEDO-TFF. Moreover, the ability to deposit films on a variety of substrates establishes the potential for lower-cost device fabrication on inexpensive substrates.展开更多
Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst being simultaneously imaged in 3D in real time using high resolution,high frame rate time-lapse synchrotron co...Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst being simultaneously imaged in 3D in real time using high resolution,high frame rate time-lapse synchrotron computed tomography(CT).This enabled direct observation of void development from nucleation,through growth to coalescence and final failure validating many inferences made post-mortem or by theoretical models,as well as raising new points.The sparse,large inclusions were found to nucleate voids at essentially zero plastic strain(consistent with zero interfacial strength);these became increasingly elongated with straining.In contrast,a high density of small spherical voids were found to nucleate from the sub-micron cementite particles at larger strains(>200%)only in the centre of the necked(high triaxiality)region.An interfacial strength approaching 2100 MPa was inferred and soon after their nucleation,these small voids coalesce to form internal microcracks that lead to the final failure of the specimen.Perhaps surprisingly,under these conditions of generally low triaxial constraint the large voids are simply cut across and appear to play no significant role in determining the final failure.The implications of these results are discussed in terms of ductile fracture behaviour and the Gurson model for ductile fracture.展开更多
We demonstrate that convenient thermal treatment of a specific sapphire vicinal surface can induce the formation of a fully two-dimensional(2D)ordered surface made of a periodic assembly of(006)facets.The simiarity be...We demonstrate that convenient thermal treatment of a specific sapphire vicinal surface can induce the formation of a fully two-dimensional(2D)ordered surface made of a periodic assembly of(006)facets.The simiarity between the resuting surface topography and pattemns represented in the hexagon series"of paintings by Vasarely is really striking!We thus propose to call these surfaces as"nanoscaled Vasarely surfaces".We also show that the self-organization process,which is driven by the minimization of the free energy of a closed system,results in a quasi-linear isothermal growth of the facets'surface area over time.展开更多
基金support from the UKRI-EPSRC,Grants Numbered EP/W006774/1,EP/P006566/1,EP/W003333/1,and EP/V061798/1funded by the support from a Royal Academy of Engineering Chair in Emerging Technologies(CiET1819/10)+1 种基金CLAL is funded in part by EP/W037483/1 and IPG Photonics/Royal Academy of Engineering Senior Research Fellowship in SEARCH(ref:RCSRF2324-18-71)This research used resources of the European Synchrotron Radiation Facility(ESRF)in Beamline ID19(ME-1573).
文摘Spatter during laser powder bed fusion(LPBF)can induce surface defects,impacting the fatigue performance of the fabricated components.Here,we reveal and explain the links between vapour depression shape and spatter dynamics during LPBF of an Al-Fe-Zr aluminium alloy using high-speed synchrotron x-ray imaging.We quantify the number,trajectory angle,velocity,and kinetic energy of the spatter as a function of vapour depression zone/keyhole morphology under industry-relevant processing conditions.The depression zone/keyhole morphology was found to influence the spatter ejection angle in keyhole versus conduction melting modes:(i)the vapour-pressure driven plume in conduction mode with a quasi-semi-circular depression zone leads to backward spatter whereas;and(ii)the keyhole rear wall redirects the gas/vapour flow to cause vertical spatter ejection and rear rim droplet spatter.Increasing the opening of the keyhole or vapour depression zone can reduce entrainment of solid spatter.We discover a spatter-induced cavity mechanism in which small spatter particles are accelerated towards the powder bed after laser-spatter interaction,inducing powder denudation and cavities on the printed surface.By quantifying these laser-spatter interactions,we suggest a printing strategy for minimising defects and improving the surface quality of LPBF parts.
文摘The 4-alkoxybenzoic acids are well-known liquid crystals showing several mesophases (nematic, smectic C phase or both) depending on the alkoxy chain length and whereby the rigid core of the mesogen is formed by intermolecular hydrogen bonds. In this paper it is shown that the thermal behaviour of lanthanide salts of 4-hexyloxybenzoic acids depends on the lanthanide ion (Ln=La, Pr, Nd, Sm, Eu). The lanthanum(Ⅲ) and praseodymium(Ⅲ) 4-hexyloxybenzoates exhibit a smectic A mesophase. No mesophase is found for the corresponding compounds of heavier lanthanides. The thermal properties of the lanthanide(Ⅲ) 4-hexyloxybenzoates were investigated by differential scanning calorimetry (DSC), polarising thermo-optical microscopy and synchrotron X-ray radiation.
文摘The code benchmarking for hadron linac using the 3D Particle-In-Cell (PIC) code is an important task in the European framework “High Intensity Pulsed Proton Injector” (HIPPI). PARMILA and HALODYN are two of the codes involved in this work. Both of these codes have been developed and used for linac design and beam dynamics studies. In this paper, the simulation results of the beam dynamics were compared and analyzed. As predicted by two codes, the simulation results show some agreements. The physical design strategy which was adopted in two codes was also discussed.
文摘Calcium hydroxide nanoparticles in aqueous suspensions (also called nanolime) were successfully employed in Cultural Heritage conservation thanks to the ability of favoring readhesion of the pictorial layer on original carbonatic substrates or allowing to a better superficial cohesion and protection of treated stones. In this work, we have synthesized nanolime particles in aqueous suspension by two different methods. The produced particles were characterized in the laboratory, in terms of structural and morphological features, by means of X-Ray diffraction powder (XRD) and by transmission electron microscopy (TEM), respectively. Nanoparticles were crystalline, regularly shaped, hexagonally plated and with side dimensions generally ranging from 300 nm to 30 nm or less. Crystal structure of nanolime particles directly in the aqueous suspension, has been also analyzed by synchrotron diffraction from X-ray synchrotron radiation (SR-XRD);data have been analyzed by means of the Rietveld method and we have investigated the structure of Ca(OH)2 particles in suspension in terms of cell parameters, atomic coordinates, bond lengths and angles.
基金Supported by the Development Foundation of Region Skane,No.REGSKANE-818781 and No.2018-Projekt0024the Foundation Skane University Hospital,No.2020-0000028.
文摘BACKGROUND The enteric nervous system(ENS)is situated along the entire gastrointestinal tract and is divided into myenteric and submucosal plexuses in the small and large intestines.The ENS consists of neurons,glial cells,and nerves assembled into ganglia,surrounded by telocytes,interstitial cells of Cajal,and connective tissue.Owing to the complex spatial organization of several interconnections with nerve fascicles,the ENS is difficult to examine in conventional histological sections of 3-5μm.AIM To examine human ileum full-thickness biopsies using X-ray phase-contrast nanotomography without prior staining to visualize the ENS.METHODS Six patients were diagnosed with gastrointestinal dysmotility and neuropathy based on routine clinical and histopathological examinations.As controls,fullthickness biopsies were collected from healthy resection ileal regions after hemicolectomy for right colon malignancy.From the paraffin blocks,4-μm thick sections were prepared and stained with hematoxylin and eosin for localization of the myenteric ganglia under a light microscope.A 1-mm punch biopsy(up to 1 cm in length)centered on the myenteric plexus was taken and placed into a Kapton®tube for mounting in the subsequent investigation.X-ray phase-contrast tomography was performed using two custom-designed laboratory setups with micrometer resolution for overview scanning.Subsequently,selected regions of interest were scanned at a synchrotron-based end-station,and high-resolution slices were reported.In total,more than 6000 virtual slices were analyzed from nine samples.RESULTS In the overview scans,the general architecture and quality of the samples were studied,and the myenteric plexus was localized.High-resolution scans revealed details,including the ganglia,interganglional nerve fascicles,and surrounding tissue.The ganglia were irregular in shape and contained neurons and glial cells.Spindle-shaped cells with very thin cellular projections could be observed on the surface of the ganglia,which appeared to build a network.In the patients,there were no alterations in the general architecture of the myenteric ganglia.Nevertheless,several pathological changes were observed,including vacuolar degeneration,autophagic activity,the appearance of sequestosomes,chromatolysis,and apoptosis.Furthermore,possible expulsion of pyknotic neurons and defects in the covering cellular network could be observed in serial slices.These changes partly corresponded to previous light microscopy findings.CONCLUSION The analysis of serial virtual slices could provide new information that cannot be obtained by classical light microscopy.The advantages,disadvantages,and future possibilities of this method are also discussed.
文摘Platinum-palladium nanoparticles are synthesized and characterized with regard to their application in fuel cells due to their high (electro) catalytic activity. Different preparation times are applied leading to different structures, from Pd cubic to core-shell PtPd concave, and different chemical compositions. The resulting particles are studied via Transmission Electron Microscopy (TEM) and in-situ X-ray absorption fine structure (XAFS) measurements. The latter allows the investigation of the oxygen reduction reaction following the variations with varying applied potentials by analysis using the Iterative Transformation Factor Analysis (ITFA) and the creation of a two-component system that consists of metallic Pt-Pd and the related oxide. With the used model, the different concentrations of the oxide are linked to the consecutive chemical steps of the oxygen reduction reaction. Finally, the catalytic activity of the particles is determined via linear scanning voltammetry and reveals a dependence on the shape and the composition of the particles.
基金financial support from ADEME for a doctoral fellowship to M.C.is gratefully acknowledged
文摘The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.
文摘Enabling the use of rationally designed thin films in technological devices is a recognized goal in materials science. However, constructing such thin films using highly ordered supramolecular architectures with well-controlled size and growth direction has remained an elusive target. Here, we introduce a layer-by- layer protocol to grow hybrid thin films of molecule-based magnetic conductors comprising arachidic acid and donor bis（ethylenedioxy）tetrathiafulvalene （BEDO-TTF） as the organic component and Cu/Gd complexes as the inorganic component. The construction of layered hybrid thin films was achieved at ambient conditions by employing the Langmuir-Blodgett method, which provides good control over film thickness and packing of molecules in the monolayer. As demonstrated by X-ray diffraction, these films are crystalline with distinct organic and inorganic sublattices, where the BEDO-TTF molecular layer is interfaced with the inorganic layer. Due to the flexibility of the Langmuir-Blodgett deposition technique, this result indicates a route toward the preparation of well-ordered films with various functionalities, determined by the choice of the inorganic compound that is combined with the π-unit of BEDO-TFF. Moreover, the ability to deposit films on a variety of substrates establishes the potential for lower-cost device fabrication on inexpensive substrates.
基金funding through a European Research Council Grant(COREL-CT)(No.695638)funded through EPSRC Grants(Nos.EP/R00661X/1,EP/S019367/1,EP/P025021/1 and EP/P025498/1)+1 种基金the Institute of Metal Research,the National Science Fund for Distinguished Young Scholars(No.5172510)the National Science and Technology Major Project(No.J2019-VI-0019–0134)。
文摘Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst being simultaneously imaged in 3D in real time using high resolution,high frame rate time-lapse synchrotron computed tomography(CT).This enabled direct observation of void development from nucleation,through growth to coalescence and final failure validating many inferences made post-mortem or by theoretical models,as well as raising new points.The sparse,large inclusions were found to nucleate voids at essentially zero plastic strain(consistent with zero interfacial strength);these became increasingly elongated with straining.In contrast,a high density of small spherical voids were found to nucleate from the sub-micron cementite particles at larger strains(>200%)only in the centre of the necked(high triaxiality)region.An interfacial strength approaching 2100 MPa was inferred and soon after their nucleation,these small voids coalesce to form internal microcracks that lead to the final failure of the specimen.Perhaps surprisingly,under these conditions of generally low triaxial constraint the large voids are simply cut across and appear to play no significant role in determining the final failure.The implications of these results are discussed in terms of ductile fracture behaviour and the Gurson model for ductile fracture.
基金This work has been carried out partially within the QMAX Project No.ANR-09-NANO-031 funded by the French National Agency(ANR)in the frame of its program in Nanosciences,Nanotechnologies and Nanosystems(P3N2009)We acknowledge the synchrotron SOLEIL and the ESRF for provision of beamtime at the synchrotron radiation facilitiesThe authors express their gratitude towards the Limousin Region for financial support of the PhD salaries of A.F.and CM..
文摘We demonstrate that convenient thermal treatment of a specific sapphire vicinal surface can induce the formation of a fully two-dimensional(2D)ordered surface made of a periodic assembly of(006)facets.The simiarity between the resuting surface topography and pattemns represented in the hexagon series"of paintings by Vasarely is really striking!We thus propose to call these surfaces as"nanoscaled Vasarely surfaces".We also show that the self-organization process,which is driven by the minimization of the free energy of a closed system,results in a quasi-linear isothermal growth of the facets'surface area over time.
