The Crystal Structure of Al4SiC4 Revisited.

Al4SiC4 is a ternary wide-band-gap semiconductor with a high strength-to-weight ratio and excellent oxidation resistance. It consists of slabs of Al4C3 separated by SiC layers with the space group of P63mc. The space group allows Si to occupy two different 2a Wykoff sites, with previous studies reporting that Si occupies only one of the two sites, giving it an ordered structure. Another hitherto unexplored possibility is that Si can be randomly distributed on both 2a sites. In this work, we revisit the published ordered crystal structure using experimental methods and density functional theory (DFT). Al4SiC4 was synthesized by high-temperature sintering at 1800 °C from a powder mixture of Al4C3 and SiC. Neutron diffraction confirmed that Al4SiC4 crystallized with the space group of P63mc, with diffraction patterns that could be fitted to both the ordered and the disordered structures. Scanning transmission electron microscopy, however, provided clear evidence supporting the latter, with DFT calculations further confirming that it is 0.16 eV lower in energy per Al4SiC4 formula unit than the former. TEM analysis revealed Al vacancies in some of the atomic layers that can introduce p-type doping and direct band gaps of 0.7 and 1.2 eV, agreeing with our optical measurements. Finally, we propose that although the calculated formation energy of the Al vacancies is high, the vacancies are stabilized by entropy effects at the high synthesis temperature. This indicates that the cooling procedure after high-temperature synthesis can be important in determining the vacancy content and the electronic properties of Al4SiC4.

Crack reduction in laser powder bed fusion of MnAl(C) using graphene oxide coated powders.

MnAl(C) is a promising candidate as a rare earth free magnet. When processing MnAl(C) in laser powder bed fusion (L-PBF) the high cooling rates can retain the high temperature ε-phase which can then be annealed at low temperatures to yield the ferromagnetic τ-phase. However, MnAl(C) has been shown to be difficult to print using L-PBF and the material is prone to severe cracking. In this study, we have investigated how the addition of a graphene oxide (GO) coating on the powders can affect the processability of MnAl(C) and properties of the printed parts. MnAl(C) powders were coated with 0.2 wt.% GO using a wet-chemical process. The addition of GO reduced crack formation in the printed parts, and also influenced the degree of [Formula: see text] texture along the build direction. After printing, densities of 93% and 87% could be achieved for the reference and 0.2 wt.% GO, respectively. Furthermore, a 35% reduction of cracking was calculated from image analysis, comparing printed samples produced from coated and non-coated powders. Both powders formed mostly the ε-phase but some two-phase regions with a mix of γ- and ε-phase could be observed in the as-printed parts, but seemed to be more prominent in the uncoated reference samples and could also be linked to cracks. The τ-phase together with smaller amounts of secondary phases was obtained after heat treatment at 560 °C for 5 min for both samples. Vibrating sample magnetometry was used to measure the magnetic properties, the reference had a remanence of 33 Am2/kg and a coercivity of 139 kA/m, and the 0.2 wt.% GO sample showed a similar remanence of 30 Am2/kg and coercivity of 130 kA/m. These results show that GO coating is a viable method to reduce detrimental cracking in L-PBF MnAl without reducing the magnetic performance of the material.

Additive Manufacturing of Cu Using Graphene-Oxide-Treated Powder.

Additive manufacturing of Cu is interesting for many applications where high thermal and electric conductivity are required. A problem with printing of Cu with a laser-based process is the high reflectance of the powder for near-infrared wavelengths making it difficult to print components with a high density. In this study, we have investigated laser bed fusion (L-PBF) of Cu using graphene oxide (GO)-coated powder. The powder particles were coated in a simple wet-chemical process using electrostatic attractions between the GO and the powder surface. The coated powder exhibited a reduced reflectivity, which improved the printability and increased the densities from ~90% for uncoated powder to 99.8% using 0.1 wt% GO and a laser power of 500 W. The coated Cu powders showed a tendency for balling using laser powers below 400 W, and increasing the GO concentration from 0.1 to 0.3 wt.% showed an increase in spattering and reduced density. Graphene-like sheet structures could be observed in the printed parts using scanning electron microscopy (SEM). Carbon-filled inclusions with sizes ranging from 10-200 nm could also be observed in the printed parts using transmission electron microscopy (TEM). The GO treatment yielded parts with higher hardness (75.7 HV) and electrical conductivity (77.8% IACS) compared to the parts printed with reference Cu powder.

Convective Flow Redistribution of Oxygen by Laser Melting of a Zr-Based Amorphous Alloy.

Oxygen impurities play a crucial role in the glass-forming ability and crystallisation behaviour of metallic glasses. In the present work, single laser tracks were produced on Zr59.3-xCu28.8 Al10.4Nb1.5Ox substrates (x = 0.3, 1.3) to study the redistribution of oxygen in the melt pool under laser melting, which provides the basis for laser powder bed fusion additive manufacturing. Since such substrates are commercially not available, they were fabricated by arc melting and splat quenching. X-ray diffraction revealed that the substrate with 0.3 at.% oxygen was X-ray amorphous, while the substrate with 1.3 at.% oxygen was partially crystalline. Hence, it is evident that the oxygen content affects the crystallisation kinetics. Subsequently, single laser tracks were produced on the surface of these substrates, and the melt pools attained from the laser processing were characterised by atom probe tomography and transmission electron microscopy. Surface oxidation and subsequent convective flow redistribution of oxygen by laser melting were identified as causes of the presence of CuOx and crystalline ZrO nanoparticles in the melt pool. Bands of ZrO likely originate from surface oxides that were moved deeper into the melt pool by convective flow. The findings presented here highlight the influence of oxygen redistribution from the surface into the melt pool during laser processing.

Prophylactic anticoagulants to prevent venous thromboembolism in patients with nephrotic syndrome-A retrospective observational study.

BACKGROUND: Nephrotic syndrome (NS) is associated with increased risk of venous thromboembolism (VTE). Guidelines suggest prophylactic anticoagulants to patients with high risk of thrombosis and low risk of bleeding, but the evidence behind this is poor. This study aims to investigate the effectiveness and risks of prophylactic anticoagulants (PAC) and investigate risk factors for VTE and bleeding in NS. METHODS: A retrospective medical records study including adults with NS, biopsy proven glomerular disease in the county of Västernorrland, Sweden. Outcomes were VTE, bleeding and death. Patients divided into PAC- and no PAC group were compared using Fisher's exact test. Patient time was divided into serum/plasma(S/P)-albumin intervals (<20g/L and ≥20g/L) and VTE- and bleeding rates were calculated. RESULTS: In 95 included NS patients (PAC = 40, no PAC = 55), 7 VTE (7.4%) and 17 bleedings (18%) were found. Outcomes didn't differ significantly between the PAC and no PAC group. Time with S/P-albumin <20g/L conferred higher rates/100 years of VTE (IRR 21.7 (95%CI 4.5-116.5)) and bleeding (IRR 5.0 (1.4-14.7)), compared to time with S/P-albumin>20g/L. CONCLUSION: Duration of severe hypoalbuminemia (S/P-albumin <20g/L) in NS is a risk factor for both VTE and bleeding. There is a need for randomized controlled studies regarding the benefit of PAC in NS as well as risk factors of thrombosis and bleeding in NS.

Synthesis and Characterisation of Nanocomposite Mo-Fe-B Thin Films Deposited by Magnetron Sputtering.

Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0-37 at.% using non-reactive DC (direct current) magnetron sputtering. The phase composition, microstructure, and mechanical properties were investigated using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation measurements. Films deposited at 300 °C and with >7 at.% Fe are nanocomposites consisting of two amorphous phases: a metal-rich phase and a metal-deficient phase. Hardness and elastic modulus were reduced with increasing Fe-content from ~29 to ~19 GPa and ~526 to ~353 GPa, respectively. These values result in H3/E2 ratios of 0.089-0.052 GPa, thereby indicating brittle behaviour of the films. Also, no indication of crystalline ternary phases was observed at temperatures up to 600 °C, suggesting that higher temperatures are required for such films to form.

Characterisation of gene and pathway expression in stabilised blood from children with coeliac disease.

INTRODUCTION: A coeliac disease (CD) diagnosis is likely in children with levels of tissue transglutaminase autoantibodies (anti-TG2) >10 times the upper reference value, whereas children with lower anti-TG2 levels need an intestinal biopsy to confirm or rule out CD. A blood sample is easier to obtain than an intestinal biopsy sample, and stabilised blood is suitable for routine diagnostics because transcript levels are preserved at sampling. Therefore, we investigated gene expression in stabilised whole blood to explore the possibility of gene expression-based diagnostics for the diagnosis and follow-up of CD. DESIGN: We performed RNA sequencing of stabilised whole blood from active CD cases (n=10), non-CD cases (n=10), and treated CD cases on a gluten-free diet (n=10) to identify diagnostic CD biomarkers and pathways involved in CD pathogenesis. RESULTS: No single gene was differentially expressed between the sample groups. However, by using gene set enrichment analysis (GSEA), significantly differentially expressed pathways were identified in active CD, and these pathways involved the inflammatory response, negative regulation of viral replication, translation, as well as cell proliferation, differentiation, migration, and survival. The results indicate that there are differences in pathway regulation in CD, which could be used for diagnostic purposes. Comparison between GSEA results based on stabilised blood with GSEA results based on small intestinal biopsies revealed that type I interferon response, defence response to virus, and negative regulation of viral replication were identified as pathways common to both tissues. CONCLUSIONS: Stabilised whole blood is not a suitable sample for clinical diagnostics of CD based on single genes. However, diagnostics based on a pathway-focused gene expression panel may be feasible, but requires further investigation.

Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films.

The microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300°C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti-Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti-Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.

Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films.

In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 °C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 °C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.

Thermal Stability of the HfNbTiVZr High-Entropy Alloy.

The multicomponent alloy HfNbTiVZr has been described as a single-phase high-entropy alloy (HEA) in the literature, although some authors have reported that additional phases can form during annealing. The thermal stability of this alloy has therefore been investigated with a combination of experimental annealing studies and thermodynamic calculations using the CALPHAD approach. The thermodynamic calculations show that a single-phase HEA is stable above about 830 °C. At lower temperatures, the most stable state is a phase mixture of bcc, hcp, and a cubic C15 Laves phase. Annealing experiments followed by quenching confirm the results from thermodynamic calculations with the exception of the Laves phase structure, which was identified as a hexagonal C14 type instead of the cubic C15 type. Limitations of the applied CALPHAD thermodynamic description of the system could be an explanation for this discrepancy. As-synthesized HfNbTiVZr alloys prepared by arc-melting form a single-phase bcc HEA at room temperature. In situ annealing studies of this alloy show that additional phases start to form above 600 °C. This indicates that the observed HEA is metastable at room temperature and stabilized by a slow kinetics during cooling. X-ray diffraction analyses using different cooling rates and annealing times show that the phase transformations in this HEA are slow and that completely different phase compositions can be obtained depending on the annealing procedure. In addition, it has been shown that the sample preparation method (mortar grinding, heat treatment, etc.) has a significant influence on the collected diffraction patterns and therefore on the phase identification and analysis.

Celiac disease biomarkers identified by transcriptome analysis of small intestinal biopsies.

Establishing a celiac disease (CD) diagnosis can be difficult, such as when CD-specific antibody levels are just above cutoff or when small intestinal biopsies show low-grade injuries. To investigate the biological pathways involved in CD and select potential biomarkers to aid in CD diagnosis, RNA sequencing of duodenal biopsies from subjects with either confirmed Active CD (n = 20) or without any signs of CD (n = 20) was performed. Gene enrichment and pathway analysis highlighted contexts, such as immune response, microbial infection, phagocytosis, intestinal barrier function, metabolism, and transportation. Twenty-nine potential CD biomarkers were selected based on differential expression and biological context. The biomarkers were validated by real-time polymerase chain reaction of eight RNA sequencing study subjects, and further investigated using an independent study group (n = 43) consisting of subjects not affected by CD, with a clear diagnosis of CD on either a gluten-containing or a gluten-free diet, or with low-grade intestinal injury. Selected biomarkers were able to classify subjects with clear CD/non-CD status, and a subset of the biomarkers (CXCL10, GBP5, IFI27, IFNG, and UBD) showed differential expression in biopsies from subjects with no or low-grade intestinal injury that received a CD diagnosis based on biopsies taken at a later time point. A large number of pathways are involved in CD pathogenesis, and gene expression is affected in CD mucosa already in low-grade intestinal injuries. RNA sequencing of low-grade intestinal injuries might discover pathways and biomarkers involved in early stages of CD pathogenesis.

Structure and Hydrogenation Properties of a HfNbTiVZr High-Entropy Alloy.

A high-entropy alloy (HEA) of HfNbTiVZr was synthesized using an arc furnace followed by ball milling. The hydrogen absorption mechanism was studied by in situ X-ray diffraction at different temperatures and by in situ and ex situ neutron diffraction experiments. The body centered cubic (BCC) metal phase undergoes a phase transformation to a body centered tetragonal (BCT) hydride phase with hydrogen occupying both tetrahedral and octahedral interstitial sites in the structure. Hydrogen cycling of the alloy at 500 °C is stable. The large lattice strain in the HEA seems favorable for absorption in both octahedral and tetrahedral sites. HEAs therefore have potential as hydrogen storage materials because of favorable absorption in all interstitial sites within the structure.

Common founder effects of hereditary hemochromatosis, Wilson´s disease, the long QT syndrome and autosomal recessive deafness caused by two novel mutations in the WHRN and TMC1 genes.

BACKGROUND: Genealogy and molecular genetic studies of a Swedish river valley population resulted in a large pedigree, showing that the hereditary hemochromatosis (HH) HFE/p.C282Y mutation is inherited with other recessive disorders such as Wilson´s disease (WND), a rare recessive disorder of copper overload. The population also contain individuals with the Swedish long QT syndrome (LQTS1) founder mutation (KCNQ1/p.Y111C) which in homozygotes causes the Jervell & Lange Nielsen syndrome (JLNS) and hearing loss (HL).Aims of the study were to test whether the Swedish long QT founder mutation originated in an ancestral HFE family and if carriers had an increased risk for hemochromatosis (HH), a treatable disorder. We also aimed to identify the pathogenic mutation causing the hearing loss disorder segregating in the pedigree. METHODS: LQTS patients were asked about their ancestry and possible origin in a HH family. They were also offered a predictive testing for the HFE genotype. Church books were screened for families with hearing loss. One HH family had two members with hearing loss, who underwent molecular genetic analysis of the LQTS founder mutation, connexin 26 and thereafter exome sequencing. Another family with hearing loss in repeat generations was also analyzed for connexin 26 and underwent exome sequencing. RESULTS: Of nine LQTS patients studied, four carried a HFE mutation (two p.C282Y, two p.H63D), none was homozygous. Three LQTS patients confirmed origin in a female founder ( b 1694, identical to AJ b 1694, a HFE pedigree member from the Fax river. Her descent of 44 HH families, included also 29 families with hearing loss (HL) suggesting JLNS. Eleven LQTS probands confirmed origin in a second founder couple (b 1614/1605) in which the woman b 1605 was identical to a HFE pedigree member from the Fjällsjö river. In her descent there were not only 64 HH, six WND families, one JLNS, but also 48 hearing loss families. Most hearing loss was non syndromic and caused by founder effects of the late 16th century. One was of Swedish origin carrying the WHRN, c.1977delC, (p.S660Afs*30) mutation, the other was a TMC1(NM_138691),c.1814T>C,(p.L605P) mutation, possibly of Finnish origin. CONCLUSIONS: Deep human HFE genealogies show HFE to be associated with other genetic disorders like Wilson´s disease, LQTS, JLNS, and autosomal recessive hearing loss. Two new homozygous HL mutations in WHRN/p.S660Afs*30 and TMC1/p.L605P were identified,none of them previously reported from Scandinavia. The rarity of JLNS was possibly caused by miscarriage or intrauterine death. Most hearing loss (81.7%) was seen after 1844 when first cousin marriages were permitted. However, only 10 (10.3%) came from 1st cousin unions and only 2 (2.0 %) was born out of wedlock.

Superior hydrogen storage in high entropy alloys.

Metal hydrides (MHx) provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. This requires the design of alloys which allow for a very high H/M ratio. Transition metal hydrides typically have a maximum H/M ratio of 2 and higher ratios can only be obtained in alloys based on rare-earth elements. In this study we demonstrate, for the first time to the best of our knowledge, that a high entropy alloy of TiVZrNbHf can absorb much higher amounts of hydrogen than its constituents and reach an H/M ratio of 2.5. We propose that the large hydrogen-storage capacity is due to the lattice strain in the alloy that makes it favourable to absorb hydrogen in both tetrahedral and octahedral interstitial sites. This observation suggests that high entropy alloys have future potential for use as hydrogen storage materials.

Combinatorial Study of Gradient Ag-Al Thin Films: Microstructure, Phase Formation, Mechanical and Electrical Properties.

A combinatorial approach is applied to rapidly deposit and screen Ag-Al thin films to evaluate the mechanical, tribological, and electrical properties as a function of chemical composition. Ag-Al thin films with large continuous composition gradients (6-60 atom % Al) were deposited by a custom-designed combinatorial magnetron sputtering system. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), nanoindentation, and four-point electrical resistance screening were employed to characterize the chemical composition, structure, and physical properties of the films in a time-efficient way. For low Al contents (<13 atom %), a highly (111)-textured fcc phase was formed. At higher Al contents, a (002)-textured hcp solid solution phase was formed followed by a fcc phase in the most Al-rich regions. No indication of a µ phase was observed. The Ag-Al films with fcc-Ag matrix is prone to adhesive material transfer leading to a high friction coefficient (>1) and adhesive wear, similar to the behavior of pure Ag. In contrast, the hexagonal solid solution phase (from ca. 15 atom %Al) exhibited dramatically reduced friction coefficients (about 15% of that of the fcc phase) and dramatically reduced adhesive wear when tested against the pure Ag counter surface. The increase in contact resistance of the Ag-Al films is limited to only 50% higher than a pure Ag reference sample at the low friction and low wear region (19-27 atom %). This suggests that a hcp Ag-Al alloy can have a potential use in sliding electrical contact applications and in the future will replace pure Ag in specific electromechanical applications.

Influence of boron vacancies on phase stability, bonding and structure of MB2 (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB2 type structure.

Transition metal diborides in hexagonal AlB2 type structure typically form stable MB2 phases for group IV elements (M = Ti, Zr, Hf). For group V (M = V, Nb, Ta) and group VI (M = Cr, Mo, W) the stability is reduced and an alternative hexagonal rhombohedral MB2 structure becomes more stable. In this work we investigate the effect of vacancies on the B-site in hexagonal MB2 and its influence on the phase stability and the structure for TiB2, ZrB2, HfB2, VB2, NbB2, TaB2, CrB2, MoB2, and WB2 using first-principles calculations. Selected phases are also analyzed with respect to electronic and bonding properties. We identify trends showing that MB2 with M from group V and IV are stabilized when introducing B-vacancies, consistent with a decrease in the number of states at the Fermi level and by strengthening of the B-M interaction. The stabilization upon vacancy formation also increases when going from M in period 4 to period 6. For TiB2, ZrB2, and HfB2, introduction of B-vacancies have a destabilizing effect due to occupation of B-B antibonding orbitals close to the Fermi level and an increase in states at the Fermi level.

A near-wearless and extremely long lifetime amorphous carbon film under high vacuum.

Prolonging wear life of amorphous carbon films under vacuum was an enormous challenge. In this work, we firstly reported that amorphous carbon film as a lubricant layer containing hydrogen, oxygen, fluorine and silicon (a-C:H:O:F:Si) exhibited low friction (~0.1), ultra-low wear rate (9.0 × 10(-13) mm(3) N(-1) mm(-1)) and ultra-long wear life (>2 × 10(6) cycles) under high vacuum. We systematically examined microstructure and composition of transfer film for understanding of the underlying frictional mechanism, which suggested that the extraordinarily excellent tribological properties were attributed to the thermodynamically and structurally stable FeF2 nanocrystallites corroborated using first-principles calculations, which were induced by the tribochemical reaction.

Structure and bonding in amorphous iron carbide thin films.

We investigate the amorphous structure, chemical bonding, and electrical properties of magnetron sputtered Fe(1-xCx) (0.21 ⩽ x ⩽ 0.72) thin films. X-ray, electron diffraction and transmission electron microscopy show that the Fe(1-xCx) films are amorphous nanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeC(y), and a carbon-rich matrix. Pair distribution function analysis indicates a close-range order similar to those of crystalline Fe(3)C carbides in all films with additional graphene-like structures at high carbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we find that the amorphous carbidic phase has a composition of 15-25 at% carbon that slightly increases with total carbon content. X-ray absorption spectra exhibit an increasing number of unoccupied 3d states and a decreasing number of C 2p states as a function of carbon content. These changes signify a systematic redistribution in orbital occupation due to charge-transfer effects at the domain-size-dependent carbide/matrix interfaces. The four-point probe resistivity of the Fe(1-xCx) films increases exponentially with carbon content from ∼200 µΩ cm (x = 0.21) to ∼1200 µΩ cm (x = 0.72), and is found to depend on the total carbon content rather than the composition of the carbide. Our findings open new possibilities for modifying the resistivity of amorphous thin film coatings based on transition metal carbides through the control of amorphous domain structures.