Solubility of iron(Ⅲ) and nickel(Ⅱ) acetylacetonates in supercritical carbon dioxide

As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.

Numerical investigation of film forming characteristics and mass transfer enhancement in horizontal polycondensation kettle

The process of producing high viscosity polyester by transesterification polycondensation needs to adjust the operating conditions and equipment structure of pre-polycondensation kettle and final polycondensation kettle to realize process intensification.In view of this,the fluid volume function method of computational fluid dynamics numerical simulation was used to investigate the film formation and surface renewal characteristics of horizontal polycondensation kettle under different operating conditions,including viscosity,rotating speed and liquid height.The results show that the viscosity and rotating speed were positively correlated with the film area and surface renewal in the pre-polycondensation stage.However,increasing the viscosity by several orders of magnitude in the final polycondensation kettle,the larger the film area and film thickness,but the overall surface renewal of the disk decreased.Therefore,a hexagonal hole disk is designed.By comparison,it is found that the film is more uniform,the surface update frequency is higher,and the power consumption can be reduced by more than 20%.

Numerical Study of Trapped Solid Particles Displacement From the Elbow of an Inclined Oil Pipeline

The solid particle impurities generated by pipe wall corrosion might deposit at the elbow of hilly pipelines during the production shutdown of oil pipelines.These solid particle impurities will seriously affect the safety of the pipeline operation and the quality of the petroleum products.Thus,it is necessary to study the methods of removing these trapped particles from pipelines.At present,the most common way to remove these solid particle impurities is pigging oil pipelines periodically by utilizing the mechanical pigging method,while the frequent pigging operation will increase the cost and risk of pipeline operation.It is very convenient and economical to remove the accumulated particles out from the pipeline by oil stream,which can be named Hydraulic Pigging Method(HPM).However,the behavior mechanism of particle in flowing oil is still unclear.This motivates the present research on the particles flushed out by the flowing oil.A numerical model governing the trapped particles displacement from the elbow of an inclined oil pipeline is established in the Euler-Lagrangian framework.The simulation is achieved via CFD coupling with DEM.The CFD method is employed to solving the continuous phase flow,while the discrete particle phase is tracked by the DEM.The numerical model is first validated by comparison with results taken from the published literature.From the simulation results,it is observed that the oil stream,carrier phase,can only flush out the solid particles in a certain diameter range under the given operation conditions,and the particles whose diameter beyond that diameter range will cannot be removed out from the pipeline.The influence of the pipe inclined angle,the oil bulk velocity and the particle diameter on the particle migration characteristics is examined in detail.Furthermore,in order to enhance the efficiency of HPM,an Enhanced Hydraulic Pigging Method based on Multi-Physical Field Collaboration(EHPM-MPFC)is also proposed in the present work.The EHPM-MPFC is validated for having high pigging efficiency via the comparison of the migration characteristics of particles during the EHPM-MPFC and HPM process.The present results can provide the guidance to the HPM operation of products pipelines.

Hot Deformation Characteristics for a Nickel-base Superalloy GH742y

The hot deformation characteristics of as-cast nickel-base superalloy GH742y after hot isostatic pressing （HIP）（hereafter referred to as-cast alloy） have been investigated by hot compression tests in the temperature range of 1050 to 1140℃, strain rate range of 0.01 s^-1 to 10 s^-1 and strain range of 35% to 50% by means of Gleeble-3500 thermal mechanical simulator. The results show that the as-cast alloy exhibits the poor deformability, and shows wedge-shaped cracking beyond the strain of 35%. At strain rates less than 1.0 s^-1, the stress-strain curves exhibit nearly steady-state behavior, while at strain rate of 10 s^-1, a yield drop and serrated yielding occur. The activation energy values developed on the basis of the experimental data are divided into three domains. The first domain appears at lower strain rate （≤1.0 s^-1） and lower temperature （≤1080℃）, with the lowest mean value of activation energy about 261.4 kJ/mol. The second domain appears at the same strain rate as the first domain, but higher temperature （〉1080℃）, with the intermediate mean value of activation energy about 328.8 k J/tool. The third domain appears at higher strain rate （10 s^-1） and temperature range of 1050 to 1140℃, with the largest mean value of activation energy about 605.05 kJ/mol. Three different constitutive equations are established in corresponding to domains. Microstructural observations in the third domain reveal non-uniform dynamic recrystallization （DRX） of homogeneous γ phase, which leads to the poor deformability and the highest Q value. In contrast, microstructures in the first domain show fully DRX of homogeneous γ phase, leading to the better deformability and the lowest Q value. It is noted that the grain size increases with the increment of strain rate or temperature. These results suggest that bulk metal working of this material may be carried out in the first domain where fully DRX of γ homogeneous occurred.

Modified Layer-Removal Method for Measurement of Residual Stress in Pre-stretched Aluminium Alloy Plate

Residual stress is one of the factors affecting the machining deformation of monolithic structure parts in the aviation industry. Thus, the studies on machining deformation rules induced by residual stresses largely depend on correctly and efficiently measuring the residual stresses of workpieccs. A modified layer-removal method is proposed to measure residual stress by analysing the characteristics of a traditional, layer-removal method. The coefficients of strain release are then deduced according to the simulation results using the finite element method （FEM）. Moreover, the residual stress in a 7075T651 aluminium alloy plate is measured using the proposed method, and the results are then analyzed and compared with the data obtained by the traditional methods. The analysis indicates that the modified layer-removal method is effective and practical for measuring the residual stress distribution in pre-stretched aluminium alloy plates.

Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equationproposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease firstas the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Snlarger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by adecrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9) and(Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9))_(0.97)Sn_3 was evaluated by Kissinger equation. It is noted that the Sn addition increases theactivation energies for glass transition and crystallization, implying that the higher thermal stability can be obtainedby appropriate addition of Sn.

Effect of Cooling Conditions on Grain Size of AZ91 Alloy

The grain size of AZ91 alloy was investigated in terms of the effects of cooling rate, superheat and steel gauze. It was found that rapid cooling rate and low superheat favoured the achievement of fine grain structures. The gauze had a less profound effect on the grain size in AZ91 magnesium alloy than that in A356 aluminum alloy. The mechanisms by which these factors affect grain refinement of AZ91 have also been discussed.

Effect of chemical ordering annealing on superelasticity of Ni-Mn-Ga-Fe ferromagnetic shape memory alloy microwires

Ni50Mn25Ga20Fe5 ferromagnetic shape memory alloy microwires with diameters of^30-50μm and grain sizes of^2-5μm were prepared by melt-extraction technique.A step-wise chemical ordering annealing was carried out to improve the superelasticity strain and recovery ratio which were hampered by the internal stress,compositional inhomogeneity,and high-density defects in the as-extracted Ni50Mn25Ga20Fe5 microwires.The annealed microwires exhibited enhanced atomic ordering degree,narrow thermal hysteresis,and high saturation magnetization under a low magnetic field.As a result,the annealed microwire showed decreased superelastic critical stress,improved reversibility,and a high superelastic strain(1.9%)with a large recovery ratio(>96%).This kind of filamentous material with superior superelastic effects may be promising materials for minor-devices.

Nucleation and Growth of Atomizing Droplets during Spray Forming

In this paper, the behaviors of nucleation and growth of atomizing droplets were investigated by means of microstructure observation and theoretical analysis. The results showed that. there is a unique heterogeneous nucleation mechanism for atomizing process that pre-solid smaller particles colliding with and embedding in liquid-state larger ones act as heterogeneous nuclei. In addition, the reasons of presenting the dendritic growth was analyzed based on the nonequilibrium solute distribution theory, and the relationship between the microstructural refinement and the cooling rate of the material was given.

Turning Affected Layers of GH4169 with Worn Tools

To solve problems of surface integrity of GH4169 caused by tool wear during machining,residual stresses layers(RSL),deformation layers(DL),and surface roughness of machined surface were studied in this work.Jobs were done at the turning parameters of v_(c)=15 m/min and f_(z)=0.05 mm/r and ap=1 mm with6 different worn tools.Firstly,tool nose wear closes to minor flank face and how it influenced machined surface were discussed.Details were given by image processing and it concluded to 5 tool w ear states according to cutting time.Secondly,relationships between tool wear states and tensile residual stresses(RS)were built so the RS range is manageable by placing a cutting time limit.Thirdly,affected layers’depths were associated w ith tool wear and the consistency betw een RSL and DL was presented.At last,roughness values variation with cutting time were discussed.Results show that RS in peripheral direction is far larger than that in axial direction.The total cutting time of a tool should be controlled within 37 min and a time period 30-37 min before severely worn owns excellent cutting effects.Tensile RS of 400 M Pa can be set as a reference value for evaluating tool quality from angle of workpiece.

Analysis on the Wear Performances of Cemented Carbide Tools Containing Ti in the Coatings When Machining Ti⁃6Al⁃4V Alloys

Because of the high affinity of the same element Ti,cemented carbide tools containing Ti seem to be non⁃optimal in machining titanium alloys.However,in practice,cemented carbide tools containing Ti are still widely used in machining titanium alloys.Cutting experiments were conducted in order to systematically explain the contradictions between the practice and theory.The diffusion process between titanium alloys and the cemented carbide tools was analyzed by auger electron spectroscopy detecting the cutting regions.It was also analyzed by Ti/Co diffusion behavior simulated by molecular thermodynamics.The experimental results and the simulation results showed that the mutual diffusion of Ti/Co atoms was the major reason for the diffusion wear.The dissolution⁃diffusion wear was one of the main wear mechanisms for the cemented carbide tools containing Ti in the coatings.Moreover,four types of cemented carbide tools and two other types of cermet tools were used to machine the Ti⁃6Al⁃4V alloys at different cutting speeds to further verify the high affinity of cutting tools containing Ti in the substrate/coating.The verification experiments results showed that the cemented carbide tools containing Ti generally cannot be used for machining titanium alloys,but could show less affinity in the cutting regions with reasonable cutting conditions.

A novel neuroprotective method against ischemic stroke by accelerating the drainage of brain interstitial fluid

Ischemic stroke is a leading cause of death and disability worldwide.Inflammatory response after stroke determines the outcome of ischemic injury.A recent study has reported an efficient method,epidural arterial implantation(EAI),for accelerating interstitial fluid(ISF)drainage,which provides a promising strategy to clear pro-inflammatory cytokines in the brain extracellular space(ECS).In this study,the method of EAI was modified(m-EAI)to control its function of accelerating the ISF drainage at different time points following ischemic attack.The neuroprotective effect of m-EAI on ischemic stroke was evaluated with the transient middle cerebral artery occlusion(tMCAO)rat model.The results demonstrated the accumulation of IL-1β,IL-6,and TNF-αwas significantly decreased by activating m-EAI at 7 d before and immediately after ischemic attack in tMCAO rats,accompanied with decreased infarct volume and improved neurological function.This study consolidates the hypothesis of exacerbated ischemic damage by inflammatory response and provides a new perspective to treat encephalopathy via brain ECS.Further research is essential to investigate whether m-EAI combined with neuroprotective drugs could enhance the therapeutic effect on ischemic stroke.

Massive water production from lunar ilmenite through reaction with endogenous hydrogen

Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.

Magneto-mechanical effect of magnetic microhydrogel for improvement of magnetic neuro-stimulation

Superparamagnetic iron oxide(SPIO)nanoparticles play an important role in mediating precise and effective magnetic neurostimulation and can help overcome limitations related to penetration depth and spatial resolution.However,nanoparticles readily diffuse in vivo,decreasing the spatial resolution and activation efficiency.In this study,we employed a microfluidic means to fabricate injectable microhydrogels encapsulated with SPIO nanoparticles,which significantly improved the stability of nanoparticles,increased the magnetic properties,reinforced the stimulation effectivity.The fabricated magnetic microhydrogels were highly uniform in size and sphericity,enabling minimally invasive injection into brain tissue.The long-term residency in the cortex up to 22 weeks and the safety of brain tissue were shown using a mouse model.In addition,we quantitatively determined the magneto-mechanical force yielded by only one magnetic microhydrogel using a video-based method.The force was found to be within 7–8 pN under 10 Hz magnetic stimulation by both theoretical simulation and experimental measurement.Lastly,electrophysiological measurement of brain slices showed that the magnetic microhydrogels offer significant advantages in terms of neural activation relative to dissociative SPIO nanoparticles.A universal strategy is thus offered for performing magnetic neuro-stimulation with an improved prospect for biomedical translation.

Relating microstructure to magnetocaloric properties in RE_(36)Tb_(20)Co_(20)Al_(24)(RE=Gd,Dy or Ho)high-entropy metallic-glass microwires designed by binary eutectic clusters method

The new high-entropy metallic-glasses(HE-MGs)are designed by using Dy and Ho to replace Gd in Gd_(36)Tb_(20)Co_(20)Al_(24)alloy based on the binary eutectic clusters method.Compared with the equiatomic Gd 25 Tb 25 Co 25 Al 25 HE-MG,the non-equiatomic RE_(36)Tb_(20)Co_(20)Al_(24)(RE=Gd,Dy,or Ho)alloys show bet-ter glass-forming ability,which is attributed to the deep binary eutectic compositions used for alloy de-sign.All RE_(36)Tb_(20)Co_(20)Al_(24)alloys undergo second-order magnetic transition.An extreme peak value of magnetic entropy change is obtained as 10.3 J kg^(-1) K-1(5 T)for the Ho_(36)Tb_(20)Co_(20)Al_(24)alloy.In-situ high-energy synchrotron X-ray diffraction was conducted to observe the microstructural difference among non-equiatomic samples at cryogenic temperatures.The results indicate that Gd_(36)Tb_(20)Co_(20)Al_(24)alloy possesses a relatively large average value of the dispersion of local clusters at a low-temperature range.This,com-bined with the critical exponentβclose to 0.5 of Gd_(36)Tb_(20)Co_(20)Al_(24)alloy,leads to its widest working temperature span among non-equiatomic samples.This work successfully establishes the connection be-tween microstructure and magnetocaloric properties of HE-MGs,which is beneficial for understanding the physical mechanism of the magnetocaloric behaviors of HE-MGs.

Green manure rotation and application increase rice yield and soil carbon in the Yangtze River valley of China

The addition of organic matter via green manure rotation with rice is considered a smart agricultural practice to maintain soil productivity and support environmental sustainability.However,few studies have quantitatively assessed the impact of green manure rotation and application on the interactions between agronomic management practice,soil fertility,and crop production.In this study,800 pairs of data from 108 studies conducted in the agricultural region of the Yangtze River,China were assessed,and random forest(RF)modeling was performed to evaluate the effect of green manure rotation and application on rice yield and soil properties.Compared to a winter fallow system,rotation and application of green manure significantly increased rice yield and soil organic carbon(SOC)by 8.1%and 8.4%,respectively.According to the RF models,rice type,green manure application rate and duration,mineral and organic nitrogen application rates,and initial SOC content and soil pH were identified as the main drivers for rice yield and SOC changes.Marginal benefit analysis revealed that green manure application rates for early rice in double cropping system and the rice in single cropping system were approximately 20 and 26 t ha-1(fresh weight),respectively.Further,the optimum green manure application rate was approximately 25 t ha-1(fresh weight)for carbon sequestration.However,it should be noted that green manure application to soils with high SOC level might result in the soils becoming a net carbon source.Our study contributed scientific and quantitative indicators for achieving the greatest benefits in rice yield and increasing SOC upon application of green manure.

四季桂抗氧化防御系统对干旱、高温及协同胁迫的响应

以天香台阁四季桂(Osmanthus fragrans cv.‘Tian Xiang Tai Ge’)为材料,研究干旱(轻度、中度和重度)、高温(40°C)及干旱高温协同胁迫对四季桂叶片抗氧化防御系统的影响。结果显示,干旱胁迫下,四季桂活性氧(ROS)逐渐积累,膜脂过氧化程度加深;轻度和中度干旱胁迫下,抗氧化酶活性显著升高;重度干旱胁迫下,抗坏血酸(As A)及其还原力(As A/DHA)显著降低,谷胱甘肽(GSH)及其还原力(GSH/GSSG)以及抗坏血酸-谷胱甘肽(As A-GSH)循环相关酶活性呈先上升后下降的趋势,在中度干旱胁迫时达到峰值。高温胁迫显著增强ROS积累、抗氧化酶活性、抗氧化剂含量及As A-GSH循环效率。干旱高温协同胁迫下,四季桂所受伤害大于单一胁迫,ROS在抗氧化酶的作用下增幅减缓;随着胁迫强度的加剧,As A-GSH循环效率呈先增加后下降的趋势,重度协同胁迫时显著降低,无法维持氧化还原平衡。四季桂在干旱高温胁迫下能快速启动体内抗氧化防御系统,清除体内过量的ROS,增加机体还原力,以减缓胁迫带来的伤害。

医药磁性氧化铁纳米材料的研究和发展

以氧化铁纳米颗粒为代表的医药磁性纳米材料,近年来在医学健康领域得到越来越多的重视.作为唯一得到食品药品监督管理局(FDA)批准,可临床使用的无机功能纳米材料,氧化铁纳米颗粒在纳米生物医学的研究和应用中发挥着至关重要的作用.本文将聚焦于氧化铁纳米颗粒等医药磁性纳米材料,主要基于本实验室的相关研究工作,介绍该领域的研究和发展.主要从如下几个方面进行论述:医药磁性氧化铁纳米材料的制备、医药磁性氧化铁纳米材料的磁学性质、医药磁性氧化铁纳米材料的生物效应、医药磁性氧化铁纳米材料的组装和性质调控以及医药磁性纳米材料及技术的发展趋势.

毛竹快速生长期茎秆不同节间光合色素和光合酶活性的差异

为揭示毛竹(Phyllostachysedulis)快速生长期茎秆中的光合碳同化特征及其在不同节间的变化规律,以毛竹笋竹茎秆为材料,测定不同节间光合色素含量、核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)、磷酸烯醇式丙酮酸羧化酶(PEPC)、苹果酸脱氢酶(NADP-MDH)、NADP-苹果酸酶(NADP-ME)、磷酸烯醇式丙酮酸羧激酶(PEPCK)以及丙酮酸磷酸双激酶(PPDK)活性。结果显示,茎秆中叶绿素a、叶绿素b以及类胡萝卜素含量随节间升高均呈下降趋势,叶绿素a/b比值呈逐渐上升趋势;随着节间的升高,茎秆中Rubisco、PEPC和PPDK活性在第1–10节间显著下降,之后酶活性降幅逐渐减缓;NADP-ME活性在第1–13节间呈显著下降趋势,之后酶活性趋于平稳;NADP-MDH活性在第1–25节间显著下降。PEPC/Rubisco活性比值随节间升高而不断增加,其范围介于18.37–65.09之间,明显大于典型C3植物中的活性比值。上述结果表明,茎秆不同节间的光合碳同化能力存在明显差异,中、下部节间生长相对较快;茎秆中存在多种C4酶且活性较高,这为此时期茎秆中存在C4光合途径提供了有力证据。

石墨烯基单原子催化剂的合成、表征及分析

单原子催化剂具有配位数低、配位环境特殊、原子利用率极高和催化位点高度均一等优点,是沟通均相和异相催化剂之间的桥梁,有助于更好地认识催化反应的本质。本文综述了近年来国内外石墨烯基单原子催化剂的多种合成方法,包括原子层沉积法、浸渍-煅烧法、缺陷捕获法、配位锚定法和其他新颖方法的制备过程、合成原理和表征。在此基础上,本文对石墨烯基金属单原子催化剂在催化方面的性能进行阐述和分析,以期为单原子催化剂制备提供指导和参考。