Hierarchically structured diamond composite with exceptional toughness.

The well known trade-off between hardness and toughness (resistance to fracture) makes simultaneous improvement of both properties challenging, especially in diamond. The hardness of diamond can be increased through nanostructuring strategies1,2, among which the formation of high-density nanoscale twins - crystalline regions related by symmetry - also toughens diamond2. In materials other than diamond, there are several other promising approaches to enhancing toughness in addition to nanotwinning3, such as bio-inspired laminated composite toughening4-7, transformation toughening8 and dual-phase toughening9, but there has been little research into such approaches in diamond. Here we report the structural characterization of a diamond composite hierarchically assembled with coherently interfaced diamond polytypes (different stacking sequences), interwoven nanotwins and interlocked nanograins. The architecture of the composite enhances toughness more than nanotwinning alone, without sacrificing hardness. Single-edge notched beam tests yield a toughness up to five times that of synthetic diamond10, even greater than that of magnesium alloys. When fracture occurs, a crack propagates through diamond nanotwins of the 3C (cubic) polytype along {111} planes, via a zigzag path. As the crack encounters regions of non-3C polytypes, its propagation is diffused into sinuous fractures, with local transformation into 3C diamond near the fracture surfaces. Both processes dissipate strain energy, thereby enhancing toughness. This work could prove useful in making superhard materials and engineering ceramics. By using structural architecture with synergetic effects of hardening and toughening, the trade-off between hardness and toughness may eventually be surmounted.

All-Scale Hierarchical Structuring, Optimized Carrier Concentration, and Band Manipulation Lead to Ultra-High Thermoelectric Performance in Eco-Friendly MnTe.

MnTe emerges as an enormous potential for medium-temperature thermoelectric applications due to its lead-free nature, high content of Mn in the earth's crust, and superior mechanical properties. Here, it is demonstrate that multiple valence band convergence can be realized through Pb and Ag incorporations, producing large Seebeck coefficient. Furthermore, the carrier concentration can be obviously enhance by Pb and Ag codoping, contributing to significant enhancement of power factor. Moreover, microstructural characterizations reveal that PbTe nanorods can be introduced into MnTe matrix by alloying Pb. This can modify the microstructure into all-scale hierarchical architectures (including PbTe nanorods, enhances point-defect scattering, dense dislocations and stacking faults), strongly lowering lattice thermal conductivity to a record low value of 0.376 W m-1 K-1 in MnTe system. As a result, an ultra-high ZT of 1.5 can be achieved in MnTe thermoelectric through all-scale hierarchical structuring, optimized carrier concentration, and valence band convergence, outperforming most of MnTe-based thermoelectric materials.

CdSe Quantum Dots Enable High Thermoelectric Performance in Solution-Processed Polycrystalline SnSe.

Here, a high peak ZT of ≈2.0 is reported in solution-processed polycrystalline Ge and Cd codoped SnSe. Microstructural characterization reveals that CdSe quantum dots are successfully introduced by solution process method. Ultraviolet photoelectron spectroscopy evinces that CdSe quantum dots enhance the density of states in the electronic structure of SnSe, which leads to a large Seebeck coefficient. It is found that Ge and Cd codoping simultaneously optimizes carrier concentration and improves electrical conductivity. The enhanced Seebeck coefficient and optimization of carrier concentration lead to marked increase in power factor. CdSe quantum dots combined with strong lattice strain give rise to strong phonon scattering, leading to an ultralow lattice thermal conductivity. Consequently, high thermoelectric performance is realized in solution-processed polycrystalline SnSe by designing quantum dot structures and introducing lattice strain. This work provides a new route for designing prospective thermoelectric materials by microstructural manipulation in solution chemistry.

Ultrastrong conductive in situ composite composed of nanodiamond incoherently embedded in disordered multilayer graphene.

Traditional ceramics or metals cannot simultaneously achieve ultrahigh strength and high electrical conductivity. The elemental carbon can form a variety of allotropes with entirely different physical properties, providing versatility for tuning mechanical and electrical properties in a wide range. Here, by precisely controlling the extent of transformation of amorphous carbon into diamond within a narrow temperature-pressure range, we synthesize an in situ composite consisting of ultrafine nanodiamond homogeneously dispersed in disordered multilayer graphene with incoherent interfaces, which demonstrates a Knoop hardness of up to ~53 GPa, a compressive strength of up to ~54 GPa and an electrical conductivity of 670-1,240 S m-1 at room temperature. With atomically resolving interface structures and molecular dynamics simulations, we reveal that amorphous carbon transforms into diamond through a nucleation process via a local rearrangement of carbon atoms and diffusion-driven growth, different from the transformation of graphite into diamond. The complex bonding between the diamond-like and graphite-like components greatly improves the mechanical properties of the composite. This superhard, ultrastrong, conductive elemental carbon composite has comprehensive properties that are superior to those of the known conductive ceramics and C/C composites. The intermediate hybridization state at the interfaces also provides insights into the amorphous-to-crystalline phase transition of carbon.

Interleukin-34 is more suitable than macrophage colony-stimulating factor for predicting liver significant fibrosis in patients with chronic hepatitis B.

AIMS: Interleukin-34 (IL-34) and macrophage colony-stimulating factor (CSF-1) have similar functions, such as promoting the formation of liver fibrosis. This study aimed to evaluate and compare the diagnostic value of serum IL-34 and CSF-1 for significant liver fibrosis in patients with chronic hepatitis B (CHB). METHODS: A total of 369 CHB patients, consisting of 208 HBeAg-negative patients and 161 HBeAg-positive patients, were enrolled in this study. Additionally, 72 healthy individuals served as healthy controls (HCs). Serum levels of IL-34 and CSF-1 were measured using the enzyme-linked immunosorbent assay method. Liver fibrosis grades were assessed using the modified Scheuer scoring system. RESULTS: Serum IL-34 and CSF-1 levels exhibited significant elevation in both HBeAg-negative and HBeAg-positive patients in comparison to HCs (p < 0.001). IL-34 emerged as an independent factor linked to significant liver fibrosis, whereas CSF-1 did not exhibit such an association. Receiver operating characteristic (ROC) analysis indicated higher areas under the curves (AUCs) for IL-34 (0.814, p < 0.001 and 0.673, p < 0.001) when diagnosing significant liver fibrosis in HBeAg-negative and HBeAg-positive patients, respectively, as opposed to CSF-1 (0.602, p < 0.001; 0.619, p = 0.385). Within the HBeAg-negative patient subgroup, the AUC for IL-34 surpassed that of FIB-4 (p = 0.009) and APRI (p = 0.045). CONCLUSION: Serum IL-34 has the potential to be a straightforward and practical biomarker that demonstrates superior performance to serum CSF-1 in the diagnosis of significant liver fibrosis in CHB patients, especially within the HBeAg-negative patients.

Theoretical insights into the structural, mechanical, and electronic properties of bcc-C40 carbon.

Novel materials displaying multiple exceptional properties are the backbone of the advancement of various industries. In the field of carbon materials, the combination of different properties has been extensively developed to satisfy diverse application scenarios, for instance, conductivity paired with exceptional hardness, outstanding toughness coupled with super-hardness, or heat resistance combined with super-hardness. In this work, a new carbon allotrope, bcc-C40 carbon, was predicted and investigated using first-principles calculations based on density functional theory. The allotrope exhibits unique structural features, including a combination of sp3 hybridized diatomic carbon and four-fold carbon chains. The mechanical and dynamic stability of bcc-C40 carbon has been demonstrated by its elastic constants and phonon spectra. Additionally, bcc-C40 carbon exhibits remarkable mechanical properties, such as zero homogeneous Poisson's ratio, superhardness with a value of 58 GPa, and stress-adaptive toughening. The analysis of the electronic properties demonstrates that bcc-C40 carbon is a semiconductor with an indirect band gap of 3.255 eV within the HSE06 functional, which increases with the increase in pressure. At a pressure of 150 GPa, bcc-C40 carbon transforms into a direct band gap material. These findings suggest the prospective use of bcc-C40 carbon as a superhard material and a novel semiconductor.

Bottom-up design of carbon allotropes with tunable properties.

Carbon materials have received great attention owing to their numerous allotropes and rich properties. Structure design and property tuning of carbon materials is one of the tremendous challenges in the field of materials science research. Here we carried out a bottom-up approach and identified a series of carbon allotropes with similar structures but distinct properties. The structures designed in this work had comparable energy stability to those previously predicted using the top-down global structure search method. Theoretical property calculations demonstrated that the three carbon structures with pure sp3 hybridization possessed semiconductive and superhard properties, while the carbon structure with sp2 + sp3 hybridization exhibited metallic features. Also, they differed significantly in the anisotropy of the mechanical properties. These carbon structures had some match to the unidentified phases in the detonation soot and could hopefully be synthesized by thermal "degassing" of high-pressure Na-C products. Our results propose a strategy to regulate properties through structural tuning, thus paving a way for the design and synthesis of materials with desirable properties.

Extreme mechanical anisotropy in diamond with preferentially oriented nanotwin bundles.

Mechanical properties of covalent materials can be greatly enhanced with strategy of nanostructuring. For example, the nanotwinned diamond with an isotropic microstructure of interweaved nanotwins and interlocked nanograins shows unprecedented isotropic mechanical properties. How the anisotropic microstructure would impact on the mechanical properties of diamond has not been fully investigated. Here, we report the synthesis of diamond from superaligned multiwalled carbon nanotube films under high pressure and high temperature. Structural characterization reveals preferentially oriented diamond nanotwin bundles with an average twin thickness of ca. 2.9 nm, inherited from the directional nanotubes. This diamond exhibits extreme mechanical anisotropy correlated with its microstructure (e.g., the average Knoop hardness values measured with the major axis of the indenter perpendicular and parallel to nanotwin bundles are 233 ± 8 and 129 ± 9 GPa, respectively). Molecular dynamics simulation reveals that, in the direction perpendicular to the nanotwin bundles, the dense twin boundaries significantly hinder the motion of dislocations under indentation, while such a resistance is much weaker in the direction along the nanotwin bundles. Current work verifies the hardening effect in diamond via nanostructuring. In addition, the mechanical properties can be further tuned (anisotropy) with microstructure design and modification.

Novel carbon allotropes in all-sp2 bonding networks: self-assembling design and first-principles calculations.

Compared with traditional structure prediction methods, the purposeful bottom-up approach is better able to obtain structures with specified performance. In this study, we established two novel carbon phases in purely sp2-bonded networks, termed H61-carbon and H62-carbon, using a self-assembling approach. These carbyne-connected carbon allotropes had helix chains joined by cumulative double-bond chains. We certified the new carbon allotropes to be dynamically and mechanically stable. Both of these carbon allotropes exhibited excellent mechanical properties, and they had metallic and superconductive characteristics featuring superconducting transition temperatures of 10 K (H61-carbon) and 7.4 K (H62-carbon), respectively. These results provide an important strategy for the design of novel carbon allotropes with specified properties.

Hardness and electronic properties of Si-C-N structures.

Three novel hexagonal Si-C-N structures, namely SiC3N3, SiC7N6, and SiC13N14, were constructed on the basis of the α-Si3N4 crystal structure. The stability of the three structures is demonstrated by analyzing their elastic constants and phonon dispersion spectra and by calculating their formation energies. The calculated band structures and partial densities of states suggest that the SiC3N3 and SiC7N6 structures possess hole conductivity. The electron orbital analyses indicate that the SiC3N3 and SiC7N6 crystals possess three-dimensional and one-dimensional conductivity, respectively. SiC13N14 is a semiconductor with a wide bandgap of 4.39 eV. Based on two different hardness models and indentation shear stress calculations, the Vickers hardness values of SiC3N3, SiC7N6, and SiC13N14 are estimated to be 28.04/28.45/16.18 GPa, 31.17/34.19/20.24 GPa, and 40.60/41.59/36.40 GPa. This result indicates that SiC3N3 and SiC7N6 are conductive hard materials while SiC13N14 is a quasi superhard material.

Heterogeneous Diamond-cBN Composites with Superb Toughness and Hardness.

The traditional hardness-toughness tradeoff poses a substantial challenge for the development of superhard materials. Due to strong covalent bonds and intrinsic brittleness, the full advantage of microstructure engineering for enhanced mechanical properties requires further exploration in superhard materials. Here heterogeneous diamond-cBN composites were synthesized from a carefully prepared precursor (hBN microflakes uniformly wrapped by onion carbon nanoparticles) through phase transitions under high pressure and high temperature. The synthesized composites inherit the architecture of the precursors: cBN regions with an anisotropic profile that spans several micrometers laterally and several hundred nanometers in thickness are embedded in a nanograined diamond matrix with high-density nanotwins. A significantly high fracture toughness of 16.9 ± 0.8 MPa m1/2 is achieved, far beyond those of single-crystal diamond and cBN, without sacrificing hardness. A detailed TEM analysis revealed multiple toughening mechanisms closely related to the microstructure. This work sheds light on microstructure engineering in superhard materials for excellent mechanical properties.

Nanocrystalline Cubic Silicon Carbide: A Route to Superhardness.

Superhard materials other than diamond and cubic boron nitride have been actively pursued in the past two decades. Cubic silicon carbide, i.e., ß-SiC, is a well-known hard material with typical hardness <30 GPa. Although nanostructuring has been proven to be effective in enhancing materials' hardness by virtue of the Hall-Petch effect, it remains a significant challenge to improve hardness of ß-SiC beyond the superhard threshold of 40 GPa. Here, the fabrication of nanocrystalline ß-SiC bulks is reported by sintering nanoparticles under high pressure and high temperature. These ß-SiC bulks are densely sintered with average grain sizes down to 10 nm depending on the sintering conditions, and the Vickers hardness increases with decreasing grain size following the Hall-Petch relation. Particularly, the bulk sintered under 25 GPa and 1400 °C shows an average grain size of 10 nm and an asymptotic Vickers hardness of 41.5 GPa. Boosting the hardness of ß-SiC over the superhard threshold signifies an important progress in superhard materials research. A broader family of superhard materials is in sight through successful implementation of nanostructuring in other hard materials such as BP.

Low-loss edge-coupling thin-film lithium niobate modulator with an efficient phase shifter: publisher's note.

This publisher's note contains corrections to Opt. Lett.46, 1478 (2021)OPLEDP0146-959210.1364/OL.418996.

Low-loss edge-coupling thin-film lithium niobate modulator with an efficient phase shifter.

Thin-film lithium-niobate-on-insulator (LNOI) is a very attractive platform for optical interconnect and nonlinear optics. It is essential to enable lithium niobate photonic integrated circuits with low power consumption. Here we present an edge-coupling Mach-Zehnder modulator on the platform with low fiber-chip coupling loss of 0.5 dB/facet, half-wave voltage Vπ of 2.36 V, electro-optic (EO) bandwidth of 60 GHz and an efficient thermal-optic phase shifter with half-wave power of 6.24 mW. In addition, we experimentally demonstrate single-lane 200 Gbit/s data transmission utilizing a discrete multi-tone signal. The LNOI modulator demonstrated here shows great potential in energy-efficient large-capacity optical interconnects.

Highly efficient thermo-optic tunable micro-ring resonator based on an LNOI platform: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 6318 (2020)OPLEDP0146-959210.1364/OL.410192.

Highly efficient thermo-optic tunable micro-ring resonator based on an LNOI platform.

We demonstrate a high-efficiency thermo-optic (TO) tunable micro-ring resonator in thin-film lithium niobate. Thermal insulation trenches around the heated micro-ring resonator and the underlying silicon substrate significantly reduce the heating power consumption and improve the tuning efficiency. Compared to conventional TO devices without thermal insulation trenches, the proposed device achieves a full free spectral range wavelength shift with a 14.9 mW heating power, corresponding to a thermal tuning efficiency of 53.7 pm/mW, a more than 20-fold improvement of tuning efficiency. The approach enables energy-efficient high-performance TO devices such as optical switches, wavelength routers, and other reconfigurable photonic devices.

Evaporation-induced self-assembly of C60 on SrTiO3(110) reconstructed surfaces.

SrTiO3(110) polar surface was treated with repeated cycles of argon ion sputtering and annealing. Three reconstructions, namely (4 × 1), (2 × 8), and (6 × 8), were identified with subsequent scanning tunneling microscopy measurements. Using the evaporation-induced self-assembly method, C60 molecules deposited onto these reconstruction surfaces demonstrated a quasi-close packing growth mode with substantial differences. Influence factors are revealed from the investigation of these differences, such as the substrate structure and topography as well as the intermolecular and molecular-substrate interactions. Our study emphasizes the feasibility of controllable molecular self-assembly through choosing surface reconstructions.

Effect of hydrocortisone on the 28-day mortality of patients with septic acute kidney injury.

Objectives: To evaluate the efficacy of hydrocortisone in patients with septic acute kidney injury (SAKI).Methods: This retrospective cohort study consisted of all consecutive patients with SAKI who were admitted to the Taizhou First People's Hospital from March 2016 to February 2018. The patients who were treated with usual care including antibiotics, fluid resuscitation, and blood glucose control were regarded as the control group, and those received add-on hydrocortisone by the clinicians' discretion was considered in the intervention group. Hydrocortisone was administered as a 50 mg intravenous bolus every six hours for seven days. To adjust the potential baseline differences between the hydrocortisone and control groups, a 1:1 propensity score matching (PSM) was performed to identify a matched control subject for each patient in the hydrocortisone group.Results: In the propensity-matched cohort, the 28-day mortality was significantly lower for patients in the hydrocortisone group (p = .04). Both Acute Physiology and Chronic Health Evaluation (APACHE) II and the Sequential Organ Failure Assessment (SOFA) scores were significantly lower at day 7 in the hydrocortisone group (both p < .01). Serum IL-1ß, IL-6, and TNF-α concentrations significantly decreased for hydrocortisone group at day 7 (all p < .01). The levels of serum creatinine (SCr), Cystatin C (CysC), and procalcitonin (PCT) were significantly lower, while the levels of glomerular filtration rate (GFR) and urine volume were significantly higher for hydrocortisone group at day 7 (all p < .01).Conclusions: Glucocorticoid supplementation may improve renal function and reduce the 28-day mortality of patients with SAKI.

Novel carbon polymorphs with cumulative double bonds in three-dimensional sp-sp2 hybrid framework.

A conspicuous amount of theoretical study has been published on the properties of carbon allotropes with alternate single and triple bonds, (-C[triple bond, length as m-dash]C-)n. However, theoretical characterizations of carbon allotropes with cumulative double bonds ([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash])n is almost non-existent in literature. Based upon first-principles calculations, two new three-dimensional (3D) microporous carbon allotropes consisting of whorl chains connected by cumulative double bonds in a sp-sp2 hybrid framework have been proposed in this study. One of these structures, namely, Trig-C9 was obtained by an evolutionary particle swarm structural search, while the other structure, denoted as Trig-C15, was obtained by inserting double bonds into Trig-C9. Both the 3D sp-sp2 hybridized carbons have a trigonal structure with 9 and 15 atoms in the hexagonal primitive cells. The calculated results demonstrate that these polymorphs are thermodynamically, mechanically, and dynamically feasible. Trig-C9 and Trig-C15 are indirect semiconductors with band gaps of 2.70 eV and 1.25 eV, respectively. Their unique frameworks render them mechanical ductility and significant elastic anisotropy. These results open up new horizons for the exploration of new carbon phases with unique structural, mechanical, and electronic properties.

Differential Expression of CD52, CD14 and HLA-DR on CD4+ Monocytes in Three Types of Acquired Bone Marrow Failure Syndromes.

BACKGROUND: Aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and myelodysplastic syndrome (MDS) are the common spectrums of acquired bone marrow failure syndromes (BMFs). Accurate and timely diagnosis is a significant clinical challenge because of the overlapping features. The pathogenesis is not fully understood, but several studies have suggested that defective monocyte functions play an important role. We aimed to find whether the different expressions of CD52, CD14 and HLA-DR on CD4+ monocytes would be helpful in the preliminary diagnosis of acquired BMFs. METHODS: This study included 45 patients (21 AA patients, 13 MDS patients, 11 PNH patients). The control group was composed of 33 healthy adults. Flow cytometry was performed to determine the fluorochrome conjugated antibodies, including CD52, CD14 and HLA-DR. RESULTS: In this study, we found the expression of CD52 on CD4+ monocytes in AA patients was significant lower than MDS [15.90% (2.39 - 25.70) vs. 60.63% (26.0 - 94.98), p < 0.001] and healthy controls [15.90% (2.39 - 25.70) vs. 67.19% (25.5 - 88.4)%, p < 0.001], and a little higher than PNH patients [15.90% (2.39 - 25.70) vs. 4.55% (3.1 - 6.0), p < 0.05]. While comparing the levels of HLA-DR on CD4+ monocytes, AA patients were lower than PNH [40.05% (17.2 - 73.3) vs. 83.14% (80.7 - 94.3), p < 0.001] and MDS patients [40.05% (17.2 - 73.3) vs. 82.37% (69.1 - 91.2), p < 0.001]. CONCLUSIONS: According to our knowledge, this is a new clinical diagnostic method that uses surface markers for CD4+ monocytes such as CD52, CD14, and HLA-DR to make differential diagnoses within AA, PNH, and MDS patients in clinical practice. In addition, CD52 in patients shows that CD52 represents the most valuable molecular marker for differential diagnosis of three types of acquired BMFs.