An amorphous-nanocrystal reinforced composite coating was fabricated on Ti–6Al–4V titanium alloy by laser cladding (LC) of the Al3Ti–TiB2–(Ni-coated WC)–Al2O3–Y2O3 mixed powders. Test results ...indicate that the lots of the nanoscale particles (NP), nanorods and amorphous phases were produced in such coating. Amorphous/nanocrystalline interface owns a high bonding energy, which may retard the growth of nanocrystals in a certain extent. With Ce–Al–Ni amorphous addition, amorphous surrounded nanopolycrystals (ASNPs) were produced after the LC process. Although coarser microstructure was obtained with productions of ASNPs, the Ce–Al–Ni addition played an important amorphization effect on such LC coating, which was beneficial in increasing wear resistance of the LC coating.
•Nanoscale particles, nanorods and amorphous phases were produced in such LC coating.•The amorphous/nanocrystalline interface owns a high bonding energy.•Amorphous/nanocrystalline interface may retard the growth of nanocrystals in a certain extent.•With the addition of Ce–Al–Ni amorphous alloy, the lots of micro/nanosize ASNPs were produced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Magnesium alloys are one of the most promising lightweight structural materials. However, the poor corrosion and wear resistance restrain their further application. As a kind of surface modification ...technique, laser cladding treatment is superior to others owing to its unique characteristics such as high efficiency and the metallurgical bonding between the coatings and substrates. In this paper, the laser cladding process and the effects of processing parameters, including laser power, scanning velocity, beam focal position, feeding ways of the material etc., are discussed in detail. The material systems preplaced on magnesium alloys are summarized. Except for the traditional metallic materials, novel ternary alloys, amorphous alloys and high entropy alloys (HEAs) are widely used and apparent advantages are exhibited. In terms of the problems existing in the laser cladding process of magnesium alloys, some potential solutions and the development tendency are reviewed.
•Laser cladding material systems on magnesium alloys are reviewed entirely.•Novel devices used for laser cladding are summarized.•The existing problems and the corresponding solutions are discussed.•Potential development tendency is forecasted based on the latest research progress.
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•Nd2O3CaOFe2O3P2O5 glass was investigated by hardness, infrared and Raman spectra.•Homogeneous glasses were obtained within 10mol% Nd2O3 additions.•Hardness showed that Nd2O3 strengthened the ...crosslinking of the glass network.•PONd bonds enter the pyrophosphate structure by replacing Q1 terminal oxygen.
Homogeneous glasses of the xNd2O3(100 − x)(12CaO20Fe2O368P2O5) system were obtained within the 0⩽x⩽10mol% composition range. The density and molar volume measurements helped to understand the structural changes occurring in these glasses. Vickers-hardness results showed that addition of Nd2O3 strengthened the crosslinking of the glass network. Spectra analysis indicated that Nd2O3 enters in the structure of the phosphate glasses as a network modifier. The depolymerization of the glass network by the addition of Nd2O3 is characterized by the increase in the concentration of pyrophosphate. The decrease of the Q1 terminal oxygen with increasing Nd2O3 content indicated that PONd bonds participated in the pyrophosphate glass structure, determined from the Raman spectra.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Packaging stress has significant influence on the thermal stability of microelectromechanical system (MEMS) devices, which utilize the die-on-substrate packaging method to connect the chips and the ...package shell. A certain adhesive, during the packaging process, is deposited on the package shell by hands or machines to shape an intermediate layer for gluing die and substrate. Due to the uncontrollability of deposition amount, the adhesive always flow out to form overflow structure on the side of die chip. The adhesive overflow will change the distribution of thermal stress induced by the changed temperature and further impact the thermal stability of devices, which is characterized by the quantity of thermal drift. This paper investigates the contribution of adhesive overflow to the thermal drift of comb MEMS capacitive accelerometers. The accelerometers with different levels of overflow are modeled by chip-adhesive-substrate models to study the deformation of sensitive component induced by temperature change. The thermal drift is acquired by an analytical method using the structure deformation and the calculation of the differential capacitance. The thermal drift theory for accelerometers with adhesive overflow is verified by a series of experiments. The results indicate that the adhesive overflow can lead to 10% increase of thermal drift compared with accelerometers without adhesive overflow. In addition, this increase can be extended by the asymmetry of supporting beams of accelerometer. Therefore, the overflow phenomenon should be carefully considered in the packaging process for highly accurate MEMS accelerometers.
Human copper transporter 1 (hCTR1) is a homotrimer of a 190-amino acid monomer having three transmembrane domains believed to form a pore for copper permeation through the plasma membrane. The ...hCTR1-mediated copper transport mechanism is not well understood, nor has any measurement been made of the rate at which copper ions are transported by hCTR1. In this study, we estimated the rate of copper transport by the hCTR1 trimer in cultured cells using 64Cu uptake assays and quantification of plasma membrane hCTR1. For endogenous hCTR1, we estimated a turnover number of about 10 ions/trimer/s. When overexpressed in HEK293 cells, a second transmembrane domain mutant of hCTR1 (H139R) had a 3-fold higher Km value and a 4-fold higher turnover number than WT. Truncations of the intracellular C-terminal tail and an AAA substitution of the putative metal-binding HCH C-terminal tripeptide (thought to be required for transport) also exhibited elevated transport rates and Km values when compared with WT hCTR1. Unlike WT hCTR1, H139R and the C-terminal mutants did not undergo regulatory endocytosis in elevated copper. hCTR1 mutants combining methionine substitutions that block transport (M150L,M154L) on the extracellular side of the pore and the high transport H139R or AAA intracellular side mutations exhibited the blocked transport of M150L,M154L, confirming that Cu+ first interacts with the methionines during permeation. Our results show that hCTR1 elements on the intracellular side of the hCTR1 pore, including the carboxyl tail, are not essential for permeation, but serve to regulate the rate of copper entry.
Copper enters human cells through pores formed by trimeric hCTR1 transporters that require intramembrane methionines near the extracellular side.
The copper transport rate is increased by mutations on the intracellular side of hCTR1.
hCTR1 elements on the intracellular side affect the copper transport rate and response to high copper.
The mutations provide unexpected insight into the hCTR1 transport mechanism.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To study the value of plasma miRNA23-a and miRNA-451 as potential biomarkers for early diagnosis of non-small cell lung cancer (NSCLC).
Fifty patients with NSCLC and 50 healthy control subjects were ...recruited for testing the plasma levels of miRNA23-a and miRNA-451 and their expression levels in the tumor tissues using qRT-PCR. The correlations of the plasma levels of miRNA23-a and miRNA-451 with their expressions in the tumor tissues were analyzed. The diagnostic power of CEA, miRNA23-a and miRNA-451 for NSCLC was evaluated using the receiver-operating characteristics (ROC) curves and the area under the ROC curves (AUC). In the NSCLC cell line A549, we tested the effect of inhibition of miRNA-23a and miRNA-451 on the expression levels of SPRY2 and MIF mRNA using qRT-PCR.
The expression levels of miRNA-23a and miRNA-451 in NSCLC tissues was significantly associated with smoking, tumor size, lymph node metastasis and TNM stage (
< 0.05). Compared with those in the control group, miRNA-23a level was significant
Laser cladding coatings with excellent wear resistance behaviors are prepared on a titanium alloy substrate with a new precursor material system comprising nanoscale B4C and Ni60A self-fluxing alloy ...powder. Structural analysis reveals the existence of micron-size spherical or nearly spherical graphitic phases in the prepared coatings, which are composed of graphene-like microstructures closely associated with other reinforcement phases of high hardness such as TiC and CrB. The formation mechanism of these graphitic phases involves in situ superassembly of uncombined C atoms via repeated growth and reorientation of the graphene-like microstructures and is closely related to the laser processing parameters as well as the precursor compositions. The coexistence of these heterogeneous phases enable the obtained coatings with high wear resistance and low friction coefficient. It was found that the wear resistance of the coating has a remarkable 43.67 times enhancement than that of the titanium alloy while simultaneously showing a low friction coefficient (∼0.35). The understanding of the formation mechanism on the graphene-related novel microstructures with significantly improved mechanical properties is expected to lay the foundation for future developments and applications of graphene and its related carbon materials, such as large-scale production and further incorporation into composite materials with desired local structures.
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The abnormal phenomenon occurring in sensor calibration is an obstacle to product development but a useful guideline to product improvement. The sensitivity jump of micro accelerometers in the ...calibrating process is recognized as an important abnormal behavior and investigated in this paper. The characteristics of jumping output in the centrifuge test are theoretically and experimentally analyzed and their underlying mechanism is found to be related to the varied stiffness of supporting beam induced by the convex defect on it. The convex defect is normally formed by the lithography deviation and/or etching error and can result in a jumping stiffness of folded microbeams and further influence the sensitivity when a part of the bending beams is stopped from moving by two surfaces contacting. The jumping level depends on the location of convex and has nothing to do with the contacting properties of beam and defects. Then the location of defect is predicted by theoretical model and simulation and verified by the observation of micro structures under microscopy. The results indicate that the tested micro accelerometer has its defect on the beam with a distance of about 290μm from the border of proof mass block.
In this study, a CLCC-3 shell and a cover were connected via soldering with AuSn20 as the solder. An Au–Sn eutectic reaction occurred during the sealing process. At high soldering temperatures, only ...the eutectic ζ′-Au5Sn and δ-AuSn phases remained. At the interface between the solder and the Au/Ni coating, Ni entered Au5Sn and AuSn to form (Au,Ni)5Sn and (Au,Ni)Sn and Au entered the lattice of the Ni3Sn2 phase to form the ternary compound (Ni,Au)3Sn2. The experimental results demonstrated that at a soldering heating plate temperature of 320 °C, the structure of the soldering area was compact and there were no holes in the soldering area. Under these conditions, the macroscopic appearance of the product improved, the solder was sufficiently melted, and the cover plate was well infiltrated, which resulted in the formation of a good, dense connection with the base plate.
•The developments of various material systems on laser surface alloying on aluminum alloys are reviewed.•The influences of different processing parameters are discussed.•The microstructure and ...surface properties of alloyed layer are analyzed.•The existing problems and the corresponding solutions are elucidated and the future developments are predicted.
Aluminum and its alloys have been widely used in aerospace, automotive and transportation industries owing to their excellent properties such as high specific strength, good ductility and light weight. Surface modification is of crucial importance to the surface properties of aluminum and its alloys since high coefficient of friction, wear characteristics and low hardness have limited their long term performance. Laser surface alloying is one of the most effective methods of producing proper microstructure by means of non-equilibrium solidification which results from rapid heating and cooling. In this paper, the influence of different processing parameters, such as laser power and scanning velocity is discussed. The developments of various material systems including ceramics, metals or alloys, and metal matrix composites (MMCs) are reviewed. The microstructure, hardness, wear properties and other behaviors of laser treated layer are analyzed. Besides, the existing problems during laser surface treatment and the corresponding solutions are elucidated and the future developments are predicted.
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