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In this paper, a novel thermoelectric material with ZT as high as 2.8 at medium temperature has been discovered, and the study shows that strong acoustic-optic coupling is a crucial factor for ultra-low lattice thermal conductivity.

The seismic discontinuity around 520 km is believed to be caused by the phase transition from wadsleyite to ringwoodite, the dominant minerals in the mantle transition zone (MTZ). Both wadsleyite and ringwoodite can contain more than 1.0 wt% water at MTZ’s conditions, but it is not well known how water affects the wadsleyite-ringwoodite transition. Here we investigated water partitioning between wadsleyite and ringwoodite and the water effect on this phase boundary using first-principles calculations. Our results show that the presence of water will shift the phase boundary to higher pressures, and the width of the two-phase coexistence domain in the Mg2SiO4-H2O system is insignificant at mid-MTZ conditions. For the (Mg0.9Fe0.1)2SiO4 system, the incorporation of 1.0 wt% water can narrow the effective width of two-phase coexistence by two-thirds. Together with elastic data, we find that velocity and impedance contrasts are only mildly changed by the water partitioning. We suggest that compared to the anhydrous condition, the presence of 1.0 wt% water will increase velocity gradients across the wadsleyite-ringwoodite transition by threefold, enhancing the detectability of the 520 km discontinuity.

Lubricant oil is crucial to the rolling bearings as the main medium of lubricating, cooling, cleaning, and so on. The oil starvation in and around the contacts is harmful to the performance and fatigue life of rolling bearings. Therefore, it is of necessity to understand the behaviors of oil transfer and the patterns of air-oil two-phase flow in bearings, especially with the influence of different capillary properties. This work established a transient air-oil two-phase flow model in a ball bearing based on computational fluid dynamics (CFD). Groups of cases are implemented to investigate the behaviors of oil transfer and air-oil flow under different capillary conditions with speed, surface tension, and viscosity. Flow patterns are classified by the morphological features of the air-oil flow. Staged phenomena are analyzed with flow patterns and reach good agreements with the observations from experiments. It is found that the oil distribution and air-oil flow behaviors in a ball bearing are strongly related to the speed and the ratio of oil viscosity and air-oil surface tension (μoil/σ). The flow maps imply that the levels of capillary number (Ca) may be the boundaries and the critical points of flow pattern transition between the different flow patterns in bearing.

Graphene-oxide (GO) has been recognized as an excellent lubrication material owing to its two-dimensional structure and weak interlayer interactions. However, the functional groups of GO that can contribute to anti-friction, anti-wear, and superlubricity are yet to be elucidated. Hence, further improvement in GO-family materials in tribology and superlubricity fields is impeded. In this study, macroscale superlubricity with a coefficient of friction of less than 0.01 is achieved by exploiting the high adhesive force between amino groups within aminated GO (GO-NH2) nanosheets and SiO2. It was observed that GO-NH2 nanosheets form a robust adsorption layer on the worn surfaces owing to the high adsorption of amino groups. This robust GO-NH2 adsorption layer not only protects the contact surfaces and contributes to low wear, but also causes the shearing plane to transform constantly from solid asperities (high friction) into GO-NH2 interlayers (weak interlayer interactions), resulting in superlubricity. A SiO2-containing boundary layer formed by tribochemical reactions and a liquid film are conducive to low friction. Such macroscale liquid superlubricity provides further insights into the effect of functional groups within functionalized GO materials and a basis for designing functionalized GO materials with excellent tribological performances.

The stability and lifetime of electrical contact pose a major challenge to the performance of microelectro-mechanical systems (MEMS), such as MEMS switches. The microscopic failure mechanism of electrical contact still remains largely unclear. Here conductive atomic force microscopy with hot switching mode was adopted to simulate the asperity-level contact condition in a MEMS switch. Strong variation and fluctuation of current and adhesion force were observed during 10,000 repetitive cycles, exhibiting an “intermittent failure” characteristic. This fluctuation of electrical contact properties was attributed to insulative carbonaceous contaminants repetitively formed and removed at the contact spot, corresponding to degradation and reestablishment of electrical contact. When contaminant film was formed, the contact interface became “metal/carbonaceous adsorbates/metal” instead of direct metal/metal contact, leading to degradation of the electrical contact state. Furthermore, a system of iridium/graphene on ruthenium (Ir/GrRu) was proposed to avoid direct metal/metal contact, which stabilized the current fluctuation and decreased interfacial adhesion significantly. The existence of graphene enabled less adsorption of carbonaceous contaminants in ambient air and enhanced mechanical protection against the repetitive hot switching actions. This work opens an avenue for design and fabrication of microscale electrical contact system, especially by utilizing two-dimensional materials.

In this study, we demonstrate for the first time the construction of a ternary BiVO4/FeVO4/Cu2O nanorod array (NRA) photoelectrode via seed-assisted refluxing, hydrothermal and successive ionic-layer adsorption and reaction (SILAR) method and its photoelectrochemical (PEC) water oxidation performance. The energy band structures of the BiVO4, FeVO4 and Cu2O show that two type-II band alignments with a ladder-like structure are formed in the constructed ternary BiVO4/FeVO4/Cu2O NRA photoelectrode, enabling the photoelectrode to display substantially enhanced PEC performance. The constructed ternary photoelectrode loaded with the optimized Cu2O nanoparticles achieves a zero-bias photocurrent density of 50 μA cm−2, 5 times higher than that of the pure BiVO4 NRA photoelectrode. The measurements of optical property reveal that the constructed BiVO4/FeVO4/Cu2O nanorod arrays (NRAs) demonstrate improved light absorption capability. The electrochemical impedance and photoluminescence measurements confirm that the charge carriers of the BiVO4/FeVO4/Cu2O heterojunction NRAs are transferred and separated effectively. The substantially boosted PEC water oxidation activity of the constructed ternary BiVO4/FeVO4/Cu2O heterojunction NRA photoelectrode is ascribed to the improved light harvesting and effective charge separation.

Common scab (CS) caused by Streptomyces spp. is a significant soilborne potato disease that results in tremendous economic losses globally. Identification of CS-associated species of the genus Streptomyces can enhance understanding of the genetic variation of these bacterial species and is necessary for the control of this epidemic disease. The present study isolated Streptomyces strain 6-2-1(1) from scabby potatoes in Keshan County, Heilongjiang Province, China. PCR analysis confirmed that the strain harbored the characteristic Streptomyces pathogenicity island (PAI) genes (txtA, txtAB, nec1, and tomA). Pathogenicity assays proved that the strain caused typical scab lesions on potato tuber surfaces and necrosis on radish seedlings and potato slices. Subsequently, the strain was systemically characterized at morphological, physiological, biochemical, and phylogenetic levels. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 6-2-1(1) shared 99.86% sequence similarity with Streptomyces rhizophilus JR-41T, isolated initially from bamboo in rhizospheric soil in Korea. PCR amplification followed by Sanger sequencing of the 16S rRNA gene of 164 scabby potato samples collected in Heilongjiang Province from 2019 to 2020 demonstrated that approximately 2% of the tested samples were infected with S. rhizophilus. Taken together, these results demonstrate that S. rhizophilus is capable of causing potato CS disease and may pose a potential challenge to potato production in Heilongjiang Province of China.