Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

The mechanism of external pressure suppressing dendrites growth in Li metal batteries

Li metal is considered an ideal anode material for application in the next-generation secondary batteries.However,the commercial application of Li metal batteries has not yet been achieved due to the safety concern caused by Li dendrites growth.Despite the fact that many recent experimental studies found that external pressure suppresses the Li dendrites growth,the mechanism of the external pressure effect on Li dendrites remains poorly understood on the atomic scale.Herein,the large-scale molecular dynamics simulations of Li dendrites growth under different external pressure were performed with a machine learning potential,which has the quantum-mechanical accuracy.The simulation results reveal that the external pressure promotes the process of Li self-healing.With the increase of external pressure,the hole defects and Li dendrites would gradually fuse and disappear.This work provides a new perspective for understanding the mechanism for the impact of external pressure on Li dendrites.

Investigation on the crystal structure and mechanical properties of the ternary compound Mg_(11-x)Zn_(x)Sr combined with experimental measurements and first-principles calculations

A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Microscopy(TEM).The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg_(11-x)Zn_(x)Sr phase belonged to tetragonal I41/amd space group and had the Cd_(11)Ba prototype.The Mg atoms were successfully doped into Zn_(11)Sr crystal lattice by occupying Zn atomic sites.Moreover,the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg_(11-x)Zn_(x)Sr compound.The elastic constants and modulus of the Mg_(11-x)Zn_(x)Sr compounds calculated by first-principles calculations(FPC)indicated they were increased with the increasing of Zn content.The variation of hardness,D-band widths and the total density of states for Mg_(11-x)Zn_(x)Sr compounds with Zn content was discussed.

The absorption of water color components and spectral modes in the Pearl River estuary

In-situ data from cruises in the Pearl River estuary and adjacent marine areas were collected during March to May 2001. The absorption coefficients of the water color components were studied in detail containing total suspended matter （TSM）, chlorophyll-a （chl-a）, colored dissolved organic matter （CDOM）, and de-pigment particles. For absorption coefficient of TSM, ap, and that of de-pigment particles, ad, correlations of ap（440）-TSM, ad（440）-TSM, ap（440）-chl-a and ad-chl-a were done （the italicized term means the concentration）. There was a good correlation between ap（440） and chl-a concentration. An empirical relationship model between aph（675） and chl-a was developed showing a strong correlation of 0.93. Based on the two models the chl-a and aph（2） were correlated. The values of calculated empirical spectral slope for CDOM absorption coefficients and that of de-pigment particles, 0.017 0 and 0.011 6 respectively, both are within a relative standard error of 10.0%.

A Single-Transistor Active Pixel CMOS Image Sensor Architecture

A single-transistor CMOS active pixel image sensor(1T CMOS APS)architecture is proposed,By switching the photosensing pinned diode,resetting and selecting can be achieved by diode pull-up and capacitive coupling pull-down of the source follower.Thus,the reset and selected transistors can be removed.In addition,the reset and selected signal lines can be shared to reduce the metal signal line,leading to a very high fill factor.The pixel design and operation principles are discussed in detail.The functionality of the proposed 1 T CMOS APS architecture has been experimentally verified using a fabricated chip in a standard 0.35μm CMOS AMIS technology.

A Comparative Study of Ballistic Transport Models for Nanowire MOSFETs

We comparatively study two representative ballistic transport models of nanowire metal-oxide-semiconductor field effect transistors,i.e.the Natori model and the Jiménez model.The limitations and applicability of both the models are discussed.Then the Jiménez model is extended to include atomic dispersion relations and is compared with the Natori model from the aspects of ballistic current and quantum capacitance.It is found that the Jiménez model can produce similar results compared with the more complex Natori model even at very small nanowire dimensions.

A unified charge-based model for SOI MOSFETs applicable from intrinsic to heavily doped channel

A unified charge-based model for fully depleted silicon-on-insulator （SOI） metal oxide semiconductor field-effect transistors （MOSFETs） is presented. The proposed model is accurate and applicable from intrinsic to heavily doped channels with various structure parameters. The framework starts from the one-dimensional Poisson Boltzmann equa- tion, and based on the full depletion approximation, an accurate inversion charge density equation is obtained. With the inversion charge density solution, the unified drain current expression is derived, and a unified terminal charge and intrinsic capacitance model is also derived in the quasi-static case. The validity and accuracy of the presented analytic model is proved by numerical simulations.

Marangoni-flow-assisted assembly of single-walled carbon nanotube films for human motion sensing

Single-walled carbon nanotubes(SWCNTs)present excellent electronic and mechanical properties desired in wearable and flexible devices.The preparation of SWCNT films is the first step for fabricating various devices.This work developed a scalable and feasible method to assemble SWCNT thin films on water surfaces based on Marangoni flow induced by surface tension gradient.The films possess a large area of 40 cm×30 cm(extensible),a tunable thickness of 15∼150 nm,a high transparency of up to 96%,and a decent conductivity.They are ready to be directly transferred to various substrates,including flexible ones.Flexible strain sensors were fabricated with the films on flexible substrates.These sensors worked with high sensitivity and repeatability.By realizing multi-functional human motion sensing,including responding to voices,monitoring artery pulses,and detecting knuckle and muscle actions,the assembled SWCNT films demonstrated the potential for application in smart devices.

Laser welding process and strength enhancement of carbon fiber reinforced thermoplastic composites and metals dissimilar joint:A review

Carbon fiber reinforced thermoplastic composites(CFRTP)and metals hybrid structures have been widely used in aircraft lightweight manufacturing.However,due to the significant difference in physical and chemical properties between CFRTP and metals,there are lots of challenges to connect them with high quality.Laser welding has a good application prospect in CFRTP and metals connection,and a significant research progress has been made in the exploration of CFRTP-metal laser joining mechanism,joining process optimization,joining strength improvement and joining defects controlling.However,there are still some problems need to be solved for this technology application.In this paper,the research progress of CFRTP-metal laser joining was summarized in three major aspects:theoretical modeling and simulation analysis,process exploration and parameter optimization,joint performance improvement and process innovation.And,problems and challenges of this technology were discussed,and the outlook of this research was provided.

Improving superficial microstructure and properties of the laser-processed ultrathin kerf in Ti-6Al-4V alloy by water-jet guiding

In the present research,the gas-assisted laser(GAL)and water-jet guided laser(WGL)processing technologies were applied to machine the ultrathin kerf in the wrought Ti-6Al-4V alloy.The microstructure,microhardness,and wear properties of the superficial layer were investigated.The results reveal that the GAL processing could machine the kerf with a high depth-to-width ratio of 12–15,but the increased processing times enhance the depth little.Due to the oxygen entrainment and relatively low heat and mass transferring efficiency,the assisted gas promotes the formation of a scaled recast layer containingβ-Ti phase and oxides,which increases the roughness to 20μm.The WGL processed kerf has a low depth-to-width ratio with a value of 1.9–2.5 and the depth could be increased by increasing the WGL processing times.With the assistance of the water jet,the remelted debris and heat could be eliminated immediately,which restrains the formation of the recast layer and heat-affected zone.The ultrathin oxide outer layer with hundreds of nanometers and ultrafineα-Ti grain inner layer are formed on the surface,which decreases the roughness to 12μm.Compared with the as-received Ti-6Al-4V alloy,the microhardness of GAL processed kerf surface is increased to 382.8 HV accompanied by residual tensile stress,while the microhardness of WGL processed kerf surface is increased to 481.6 HV accompanying with residual compressive stress.In addition,the GAL processing increases the wear rate at room temperature but decreases the wear rate at high temperatures.Comparatively,the WGL processing decreases the wear rate at room and high temperatures,simultaneously.Such wear behaviors could be ascribed to their different superficial microstructures and phase constituents.

Corrosion resistance properties of colored zirconium conversion coating and powder coating on cold-rolled steel

Jiuhe Corporation developed a new surface pretreatment for producing a phosphate-free and colored zirconium conversion coating on cold-rolled steel(CRS).Scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS)were applied to study the surface morphology and elemental composition of the golden yellow-colored conversion coating.Elec trochemic al impedance spectroscopy(EIS)was used to investigate the electrochemical performance of the conversion coatings with different colors.The corrosion resistance properties of the powder coatings were characterized using the neutral salt spray test(NSS)and the tape adhesion test.The EIS and NSS results demonstrate that the colored zirconium conversion coatings exhibit excellent corrosion resistance properties compared with the bare CRS.The golden yellow-colored conversion coating has a maximum EIS value(748Ω·cm^(2))and achieves 0 mm degree of corrosion,as stipulated by EN ISO 4628-8.This paper proposes a hypothesis concerning the ZrO_(2)-(β-FeOOH)-polymer conversion reaction to explain the color changes.

Selective growth of semiconducting single-walled carbon nanotubes solely from carbon monoxide

The selective growth of semiconducting single-walled carbon nanotubes(s-SWCNTs)is of great importance in many high-end applications represented by nanoelectronics.Here,we developed a general approach to grow horizontally aligned s-SWCNT arrays on stable temperature(ST)-cut quartz with bimetallic catalysts using carbon monoxide(CO)as both catalyst reductant and single component carbon feedstock under atmospheric pressure.The disproportionation of CO produces not only carbon species for SWCNT growth but also CO_(2),which could act as an in-situ etchant to remove both amorphous carbon and metallic tubes.The employment of bimetallic catalyst and quartz substrate facilitates the selective etching by narrowing the diameter distribution of as-grown SWCNT arrays.At the optimized conditions,we realized the selective growth of horizontally aligned s-SWCNT arrays with the content above 97%using CoCu catalysts,confirmed by Raman characterization and electrical measurements of the fabricated field effect transistor devices.This CO-based process in selective growth of s-SWCNTs has demonstrated its feasibility and universality by the broad growth window and applicability for other bimetallic catalysts,such as FeCu and CoMn.It possesses a practical potential in obtaining semiconducting channel materials for the scalable fabrication of CNT-based devices.

Carbon nanotube supported bifunctional electrocatalysts containing iron-nitrogen-carbon active sites for zinc-air batteries

Bifunctional electrocatalysts with high activity toward both oxygen reduction and evolution reaction are highly desirable for rechargeable Zn-air batteries. Herein, a kind of carbon nanotube (CNT) supported single-site Fe-N-C catalyst was fabricated via pyrolyzing in-situ grown Fe-containing zeolitic imidazolate frameworks on CNTs. CNTs not only serve as the physical supports of the Fe-N-C active sites but also provide a conductive network to facilitate the fast electron and ion transfer. The as-synthesized catalysts exhibit a half-wave potential of 0.865 V for oxygen reduction reaction and a low overpotential of 0.442 V at 10 mA·cm^(−2) for oxygen evolution, which is 310 mV smaller than that of Fe-N-C without CNTs. The rechargeable Zn-air batteries fabricated with such hybrid catalysts display a high peak power density of 182 mW·cm^(−2) and an excellent cycling stability of over 1,000 h at 10 mA·cm^(−2), which outperforms commercial Pt-C and most of the reported catalysts. This facile strategy of combining single-site Metal-N-C with CNTs network is effective for preparing highly active bifunctional electrocatalysts.

Intra-and inter-specific scaling laws of plants and animals

The allometric scaling laws of metabolism in 447 animal and 1200 plant species showed convex and concave curvatures between mass and metabolic rate,respectively.The objective of the study is to explain the difference of curvatures between animals and plants based on fractal models.Several intraspecific scaling laws were derived from an asymmetric vascular tree with the fractal dimension(i.e.,a in k^(a)_(1)+k^(a)_(2)+…-=1,where k_(i)refers to the ratio of daughter to mother diameters).Based on the intraspecific scaling laws,the allometric scaling exponent of metabolism(i.e.,an interspecific scaling law)was shown to be equal to one-third of fractal dimension.Moreover,a novel piecewise-defined function in conjunction with the intraspecific scaling laws was proposed to explain the diverse metabolic scaling in animals and plants.The intraspecific and interspecific scaling laws showed good agreement with morphometric measurements.The experimentally-validated scaling models predict the diversity of intraspecific and interspecific scaling seen in nature.To our knowledge,this is the first study to use fractal models to explain the convex and concave forms of metabolic scaling in animals and plants.The study resolves the long-term controversies to use the resource-transport network models for explanation of the allometric scaling law of metabolism.

Growth of Single-walled Carbon Nanotubes on Substrates Using Carbon Monoxide as Carbon Source

The growth of single-walled carbon nanotubes(SWCNTs)on substrates has attracted great interests because of the potential applications in various fields.Carbon monoxide(CO)was used as the carbon source for the growth of SWCNTs on silicon substrates.Random or oriented SWCNTs can be produced by varying the CO flow rate.When the flow rate of CO was as low as 20 sccm(sccm:standard cubic centimeter per minute).

Narrowband speech wideband extension algorithm research

To reduce the spectral distortion,a Hidden Markov Model-based narrowband speech bandwidth extension algorithm is presented.Firstly,the parameters which have higher mutual information with wideband envelope were extracted to constitute the feature vector,and then a posterior probability was calculated via the joint probability of the partial observation feature vector sequence and the markov states.Secondly,based on the posterior probability,the wideband envelope was estimated using Bayesian parameter estimation method and minimum mean square error criteria.For estimation of wideband excitation signal,intermediate frequency extension algorithm is proposed based on the harmonic correlation between the low frequency and high frequency.The experimental results show that,compared with the traditional bandwidth extension algorithm based on Hidden Markov Model,the average spectral distortion is reduced by 0.187 dB and the number of speech frame with spectral distortion over10dB is decreased by 34.3%.

Building blocks for one-dimensional van der Waals heterostructures

We recently demonstrated experimentally the synthesis of one-dimensional(1D)van der Waals(vdW)heterostructure,where single-crystal hexagonal boron nitride or molybdenum disulfide nanotubes seamlessly wrapped a singlewalled carbon nanotube and formed a coaxial hetero-nanotube with the diameter typically being 1–5 nm.1D vdW heterostructures have created large room for fundamental research from synthesis to application,but most directions are still at their initial stages.The materials that can be employed to construct 1D vdW heterostructures are limited to only a few types.In this review,we provide an outlook to the question:what are the building blocks available now and could be available in the future for the fabrication of 1D vdW heterostructures?