Carbon Material with Fibonacci Parastichy Structure

The curd of Romanesco broccoli was carbonized at 900°C under argon atmosphere in a gold furnace chamber. The carbonization afforded a carbon material with a fine logarithmic spiral on the surface, resembling the Fibonacci parastichy structure of the Romanesco broccoli flower bud. The carbonized “flower bud” structure was observed under scanning electron microscopy. Infrared absorption spectra and X-ray photoelectron spectroscopy measurements confirmed the chemical structure and component of the carbon material.

Sc元素添加对双辊铸轧Al−Cu−Li−Mg−Zr基合金热处理的影响

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金均先在300℃下退火30 min,然后在450℃下退火30 min以及530℃下退火30 min,随后进行室温水淬。前两段退火后组织中生成了细小、弥散的Al_(3)Zr/Al_(3)(Sc,Zr)颗粒。最后的退火步骤起到了均匀化/固溶处理的作用。双辊铸轧材料的细小晶粒结构使含有主要合金元素的原始颗粒在较短的退火时间内溶解。缩短保温时间可以限制表面层中Li的耗尽和Al_(3)Zr/Al_(3)(Sc,Zr)弥散相的明显粗化。铸态含Sc材料已经具有明显细小的晶粒结构,而经均匀化/固溶处理后生成的Al_(3)(Sc,Zr)弥散相抑制了晶粒在高温下发生粗化。在后续180℃下时效处理后,形成了θʹ(Al_(2)Cu)、T1(Al_(2)CuLi)和S'(Al_(2)CuMg)强化相。在峰值时效状态下,屈服强度提高了200 MPa,这一数值与类似直接冷却铸造材料的相当,从而证实了所提方案的合理性。

Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy

In this paper,the formation process,morphology,and electrochemical performance of PEO coatings on AM50 magnesium alloy prepared in low concentration phosphate,aluminate,and phosphate-aluminate electrolytes were systematically studied.The results show that the coatings prepared from the phosphate electrolytes have a higher thickness and better corrosion resistance properties compared to the other electrolytes.The coatings prepared from low concentration phosphate-aluminate mixed electrolytes have slightly thinner thickness,a similar coating structure and an order of magnitude lower value of electrochemical impedance compared with phosphate electrolyte coatings.The Coatings prepared from low concentration aluminate electrolytes have the lowest thickness and the worst corrosion resistance properties which gets close to corrosion behavior of the bare AM50 under the same test conditions.Considering application,coatings prepared from single low concentration phosphate electrolytes and low concentration phosphate-aluminate electrolytes have greater potential than single low concentration aluminate coatings.However,reducing the electrolyte concentrations of coating forming ions too much has negative influence on the coating growth rate.

A combined computational/experimental study of anode-concerned voltage drop in aqueous primary Mg-air batteries

The voltage drop appearing at Mg anode-electrolyte interface is a critical issue for the battery power and energy density of aqueous primary Mg-air batteries.The respective voltage loss is typically assigned to the deposits layer forming on the anode surface during discharge.In this work,we experimentally and computationally investigate the critical factors affecting the voltage drop at Mg anode towards a deeper understanding of the contribution of deposit and its growth.A two-dimensional(2D)mathematical model is proposed to compute the voltage drop of Mg-0.15Ca wt.%alloy(Mg-0.15Ca)by means of a semi-empirical formulas and experiments-based modification model,considering the effect of discharge current density,the negative difference effect(NDE)and surface deposits layer itself.This model is utilized to simulate the discharge potential of the anode at predefined experimental current densities.The computed voltage drop(half-cell voltage)is in good agreement with the experimental value.The applicability of the mathematical model is successfully validated on the second material(namely high-purity Mg).

Improvement of corrosion resistance of PEO coated dissimilar Ti/Mg0.6Ca couple

With the growing demand for weight reduction,the application of joint lightweight structural materials is increasing.Magnesium alloys feature low density,high specific strength and good formability,offering significant advantages for fuel efficiency and load capacity.Combined with Ti,a dissimilar Ti/Mg composite material provides great flexibility combining the properties of each material.However,because of the great differences in chemical and electrochemical properties between Mg and Ti,it is imperative to address the galvanic corrosion problem of such dissimilar Ti/Mg components.This work presents an investigation of the PEO processing of sintered Ti/Mg0.6Ca couples,aiming to improve the corrosion resistance of such dissimilar alloy combinations using a phosphate-aluminate electrolyte.The results show that uniform and continuous coatings can be formed on the dissimilar Ti/Mg0.6Ca couple.The coating mainly contains MgO and MgAl_(2)O_(4)on the Mg0.6Ca side,and Al_(2)TiO_(5)is the dominant phase on the Ti side.The work also took advantage of synchrotron X-ray computed tomography(CT)scanning to achieve 3D reconstruction of the coating morphology,which can be a fast method to assess the porosity and compactness of the coating and further predict the coating corrosion resistance.The coating effectively improved the corrosion resistance of the dissimilar Ti/Mg0.6Ca couple.

“Abnormal transient creep” in fine-grained Al-5356 alloy observed at low strain rates by high-resolution strain measurement

Transient creep at very low strain rates （less than 10-10 s-1） is still unclear. The traditional uniaxial creep testing is less useful due to unsatisfied resolution strain （~10-6）. To study transient creep behavior at such low strain rates, a high-resolution strain measurement using the helicoid spring specimen technique was employed in a fine-grained Al-5356 alloy at temperatures ranging from 0.47Tm to 0.74Tm （Tm： melting point）. To clarify transient creep mechanism at such low strain rates, transmission electron microscopy （TEM） was used in microstructure observation of crept specimens. The abnormal transient creep, high temperature strengthening at T〉Tp （Tp： the phase transformation temperature, 0.58Tm） or intermediate temperature softening at 0.4Tm〈T￡Tp and double-normal type （creep curves including double work-hardening stages） at T=Tp, were firstly observed. The substructure observation in a crept specimen at T=0.58Tm and e=1×10-4 shows pile-up dislocations including many small jogs with equal interval, and dislocations emitted from grain boundaries. The b-Al3Mg2 phase dissolves under the condition of testing temperatures higher than 523 K, which causes solid-solution quantity of Mg atoms to increase. Therefore, the “abnormal transient creep” may be related to the difference of solid solution strengthening caused by phase change during the creep tests.

Primary-transient creep and anelastic backflow of pure copper deformed at low temperatures and ultra-low strain rates

Creep and anelastic backflow behaviors of pure copper （4N Cu） with grain size dg=40 μm were investigated at low temperatures of T〈0.3Tm （Tm is melting point） and ultra-low creep rates of ε≤1×10^-10 s^-1 by a high strain-resolution measurement （the helicoid spring specimen technique）. Analysis of creep data was based on the scaling factors of creep curves instead of the conventional extrapolated steady-state creep rate. Power-law creep equation is suggested to be the best for describing the primary transient creep behavior, because the pre-parameter does not apparently change with elapsed time. The observed anelastic strains are 1/6 of the calculated elastic strains, and linear viscous behavior was identified from the logarithm plot of the anelastic strain rate versus anelastic strain （slope equals 1）. Therefore, the creep anelasticity is suggested to be due to the unbowing of there-dimensional network of dislocations.

Corrosion and wettability of PEO coatings on magnesium by addition of potassium stearate

Hydrophobic PEO coatings were fabricated in an electrolyte containing potassium stearate.The wetting behaviour of coated samples was studied using dynamic and static contact angle.Also,the corrosion behaviour of the samples was evaluated by polarization method.The dynamic contact angle and hysteresis of the contact angle for PEO coating were evaluated by Wilhelmy plate method.There was an increase in the contact angle of the nanocomposite and traditional PEO coatings when potassium stearate was added to the electrolyte up to 130°.The more hydrophobic coatings,showed more corrosion resistance in 3.5 wt.%NaCl solution.The synergistic effect of potassium stearate and nanoparticles increased the hydrophobicity because of assembling of fatty acid on ceramic powder.

Cu-Zn-Al2O3 nanocomposites: study of microstructure, corrosion, and wear properties

Alumina nanoparticles were added to a Cu-Zn alloy to investigate their effect on the microstructural,tribological,and corrosion properties of the prepared alloys. Alloying was performed using a mixture of copper and zinc powders with 0vol% and 5vol% of α-Al nanopowder in a satellite ball mill. The results showed that the Cu-Zn solid solution formed after 18 h of mechanical alloying. The mechanically alloyed powder was compacted followed by sintering of the obtained green compacts at 750°C for 30 min. Alumina nanoparticles were uniformly distributed in the matrix of the Cu-Zn alloy. The tribological properties were evaluated by pin-on-disk wear tests,which revealed that,upon the addition of alumina nanoparticles,the coefficient of friction and the wear rate were reduced to 20% and 40%,respectively. The corrosion properties of the samples exposed to a 3.5wt% Na Cl solution were studied using the immersion and potentiodynamic polarization methods,which revealed that the addition of alumina nanoparticles reduced the corrosion current of the nanocomposite by 90%.

Clarifying the influence of albumin on the initial stages of magnesium corrosion in Hank's balanced salt solution

The corrosion behavior of Mg,a promising biodegradable metallic material,in protein-containing pseudophysiological environment is still not fully understood.In this work,the influence of albumin on the corrosion behavior of commercially pure magnesium(CP Mg)is investigated during short-term tests in Hank’s Balanced Salt Solution(HBSS).This work focuses on the reactions at the Mg/medium interface from the perspective of the interactions among albumin,media components and substrate.Hydrogen evolution tests demonstrate that the physiological amount of albumin(40 g L^(-1))accelerates Mg corrosion in HBSS during the first few hours but slows down the degradation afterwards.The presence of albumin decreases the concentration of free Ca^(2+)in HBSS and delays formation of protective co-precipitation products on Mg surface.The evolution of local pH(differs from typically monitored bulk pH)near Mg/medium interface in albumincontaining HBSS is reported for the first time.Comparison of local and bulk pH values elucidates the pH buffering effect of albumin during the immersion period.Based on these results,adsorption,chelating and pH buffering effects are summarized as three important aspects of albumin influence on Mg corrosion.Additionally,constant replenishment of medium components is shown to be an influential factor during the Mg corrosion tests.

Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis

Oxygen reduction reaction(ORR)has been disclosed in recent studies as a significant secondary cathodic process during magnesium corrosion.This work elaborates on the contribution of ORR to the total corrosion process of pure Mg at different impurity levels in NaCl electrolyte with the assistance of local techniques.A finite element based numerical model taking into account the contribution of ORR during the corrosion of the Mg test materials has been designed in this study considering the local oxygen concentration.Respective computational simulations were calibrated based on the experimental data and evaluated accordingly.Finally,the simultaneous monitoring of local concentration of H_(2) and O_(2),and the combined modeling study reveal the relation between ORR and hydrogen evolution reaction.

Evaluation of the Electroslag Remelting Process in Medical Grade of 316LC Stainless Steel

This study is focused on the effects of electroslag remelting by prefused slag （CaO, Al2O3, and CaF2） on macrostructure and reduction of inclusions in the medical grade of 316LC （316LVM） stainless steel. Analysis of the obtained results indicated that for production of a uniform ingot structure during electroslag remelting, shape and depth of the molten pool should be carefully controlled. High melting rates led to deeper pool depth and interior radial solidification characteristics, while decrease in the melting rates caused more reduction of nonmetallic inclusions. Large shrinkage cavities formed during the conventional casting process in the primary ingots were found to be the cause of the fluctuation in the melting rate, pool depth and extension of equiaxed crystals zone.

Dynamic ModeⅡfracture behavior of rocks under hydrostatic pressure using the short core in compression(SCC)method

The shear failure of rocks under both a static triaxial stress and a dynamic disturbance is common in deep underground engineering and it is therefore essential for the design of underground engineering to quantitively estimate the dynamic ModeⅡfracture toughness KⅡCof rocks under a triaxial stress state.However,the method for determining the dynamic KⅡCof rocks under a triaxial stress has not been developed yet.With an optimal sample preparation,the short core in compression(SCC)method was designed and verified in this study to measure the dynamic KⅡCof Fangshan marble(FM)subjected to different hydrostatic pressures through a triaxial dynamic testing system.The formula for calculating the dynamic KⅡCof the rock SCC specimen under hydrostatic pressures was obtained by using the finite element method in combination with secondary cracks.The experimental results indicate that the failure mode of the rock SCC specimen under a hydrostatic pressure is the shear fracture and the KⅡCof FM increases as the loading rate.In addition,at a given loading rate the dynamic rock KⅡCis barely affected by hydrostatic pressures.Another important observation is that the dynamic fracture energy of FM enhances with loading rates and hydrostatic pressures.

Effects of Potassium and Manganese Promoters on Nitrogen-Doped Carbon Nanotube-Supported Iron Catalysts for CO_2 Hydrogenation

Nitrogen-doped carbon nanotubes （NCNTs） were used as a support for iron （Fe） nanoparticles applied in car- bon dioxide （CO_2） hydrogenation at 633 K and 25 bar （1 bar = 10-5 Pa）. The Fe/NCNT catalyst promoted with both potassium （K） and manganese （Mn） showed high performance in CO_2 hydrogenation, reaching 34.9% conversion with a gas hourly space velocity （GHSV） of 3.1 L-（g·h）-1. Product selectivities were high for olefin products and low for short-chain alkanes for the K-promoted catalysts. When Fe/NCNT catalyst was promot- ed with both K and Mn, the catalytic activity was stable for 60 h of reaction time. The structural effect of the Mn promoter was demonstrated by X-ray diffraction （XRD）, temperature-programmed reduction （TPR） with molecular hydrogen （H2）, and in situ X-ray absorption near-edge structure （XANES） analysis. The Mn pro- moter stabilized wtistite （FeO） as an intermediate and lowered the TPR onset temperature. Catalytic ammo- nia （NH_3） decomposition was used as an additional probe reaction for characterizing the promoter effects. The Fe/NCNT catalyst promoted with both K and Mn had the highest catalytic activity, and the Mn-promoted Fe/NCNT catalysts had the highest thermal stability under reducing conditions.

BioPerine Encapsulated Nanoformulation for Overcoming Drug-Resistant Breast Cancers

The evolving dynamics of drug resistance due to tumor heterogeneity often creates impediments to traditional therapies making it a challenging issue for cancer cure.Breast cancer often faces challenges of current therapeutic interventions owing to its multiple complexities and high drug resistivity,for example against drugs like trastuzumab and tamoxifen.Drug resistance in the majority of breast cancer is often aided by the overtly expressed P-glycoprotein(P-gp)that guides in the rapid drug efflux of chemotherapy drugs.Despite continuous endeavors and ground-breaking achievements in the pursuit of finding better cancer therapeutic avenues,drug resistance is still a menace to hold back.Among newer therapeutic approaches,the application of phytonutrients such as alkaloids to suppress P-gp activity in drug-resistant cancers has found an exciting niche in the arena of alternative cancer therapies.In this work,we would like to present a black pepper alkaloid derivative known as Bio Perine-loaded chitosan(CS)-polyethylene glycol(PEG)coated polylactic acid(PLA)hybrid polymeric nanoparticle to improve the bioavailability of Bio Perine and its therapeutic efficacy in suppressing P-gp expression in MDA-MB 453 breast cancer cell line.Our findings revealed that the CS-PEG-Bio PerinePLA nanoparticles demonstrated a smooth spherical morphology with an average size of316 nm,with improved aqueous solubility,and provided sustained Bio Perine release.The nanoparticles also enhanced in vitro cytotoxicity and downregulation of P-gp expression in MDA-MB 453 cells compared to the commercial inhibitor verapamil hydrochloride,thus promising a piece of exciting evidence for the development of Bio Perine based nano-drug delivery system in combination with traditional therapies as a crucial approach to tackling multi-drug resistance in cancers.

Continuous cooling precipitation diagram of cast aluminium alloy Al-7Si-0.3Mg

The precipitation behaviour during quenching of cast Al-7Si-0.3Mg aluminium alloy was investigated by DSC in the cooling rate range of 0.01 K/s to 3 K/s and by quenching dilatometry for higher rates. Two main precipitation reactions were observed during cooling, a high temperature reaction starting almost directly with quenching from 540℃ and a low temperature reaction starting at about 400℃. Quenching with 3 K/s already significantly suppresses precipitation during quenching. Hardness after T6 ageing increases with increasing quenching rate, due to the increasing content of supersaturated solid solution. By dilatometry and hardness results the critical cooling rate can be estimated as about 60 K/s. Quenched Al-7Si-0.3Mg microstructures have been investigated by light microscopy. The microstructures consist of an aluminium-silicon eutectic structure, aluminium solid solution dendrites and precipitates inside the aluminium dendrites, depending on quenching rate.

CuCrW(Al2O3) nanocomposite: mechanical alloying, microstructure, and tribological properties

The effect of alumina nanoparticle addition on the microstructure and tribological properties of a CuCrW alloy was investigated in this work. Mechanical alloying was carried out in a satellite ball mill. The tribological properties of the samples were evaluated using pin-on-disk wear tests with different pins(alumina, tungsten carbide, and steel pins). The results indicated that the tungsten carbide pin had a lower coefficient of friction than the alumina and steel pins because of its high hardness and low surface roughness. In addition, when the sliding rate was decreased, the weight-loss rate increased. The existence of alumina nanoparticles in the nanocomposite led to a lower weight-loss rate and to a change in the wear mechanism from adhesive to abrasive.

Microwave-assisted synthesis of CePO_4 nanorod phosphor with violet emission

Monochnic and hexagonal CePO4 nanoparticles and nanorods were successfully synthesized from Ce（NO3）36H2O and Na3PO4 121-120 solu- tions at pH 1-5 by a 180 W microwave radiation for 60 min. The products were characterized by X-ray diffraction （XRD）, Fourier transform infrared （FFIR） spectroscopy, and scanning electron microscopy （SEM）. XRD patterns revealed that the products are hexagonal CePO4 structures at pH 2-5, and monoclinic CePO4 structtLres at pH 1. SEM characterization shows that these products were nanoparticles, short nanorods, and long nanorods, controlled by the pH of the precursor solutions. Optical properties of the nanorods were also investigated by ultraviolet-visible （UV-vis） and photoluminescence （PL） spectroscopy.

In-situ LDHs growth on PEO coatings on AZ31 magnesium alloy for active protection:Roles of PEO composition and conversion solution

In this work,plasma electrolytic oxidation(PEO)coatings were produced on magnesium alloy AZ31 in aluminate,silicate and phosphate-based electrolytes,and followed by hydrothermal treatments in order to synthesis layered double hydroxides(LDHs)based nanocontainers.LDHs synthesis was done in three different growth solutions(deionized water,sodium nitrate and aluminum nitrate containing solution).In frame of this work it was shown,that it was difficult to form LDHs on Si-based PEO coating,due to more stable silicate phases in comparison with aluminate and phosphate phases in respective PEO coatings.The obtained hybrid LDH/PEO coatings were characterized using SEM,EDS and GDOES,and then the corrosion protection was further investigated by EIS.Based on the obtained results,it was confirmed that,the hydrothermal treatments in Al^(3+)containing solution played an important role on overall corrosion resistance for phosphate and silicate-based PEO coatings,but not for Al-based PEO coatings.