氧化镉纳米颗粒的制备

以氧化镉（CdO）和间硝基苯甲酸（HL,C7H5NO4）为原料，利用水热反应合成前驱体Cd（C7H4NO4）2·1.5H2O,然后通过焙烧得到CdO纳米颗粒。采用X射线衍射（XRD）考察了不同焙烧温度及不同焙烧时间对CdO晶粒尺寸的影响。结果表明，根据Scherrer公式计算的CdO晶体的晶粒尺寸随着焙烧温度的增高而增大，随着焙烧时间的延长而减小。

耗散粒子动力学模拟方法在软物质体系研究中的一些进展与应用

软物质是指处于固体和理想流体之间的复杂态物质,主要包括聚合物、表面活性剂、液晶、胶体悬浮液、以及生物大分子等。软物质能够对外界微小的作用产生强烈的非线性响应,并展现出丰富的有序自组装相态。作为一种新颖的模拟技术,耗散粒子动力学方法非常适合在介观尺度上对软物质体系的复杂行为进行合理的描述。本文对耗散粒子动力学模拟方法的发展及一些应用进行了系统评述。耗散粒子动力学模拟方法体现了分子动力学与格子Boltzmann模型的优点,通过与其它理论模型(如Flory-Huggins理论、Smoothed particle hydrodynamics模型等)相结合,该方法能够在介观尺度上有效地研究聚合物熔体和溶液体系、生物膜及囊泡体系以及胶体悬浮液等体系的行为。这些研究结果,对新材料的研发、特殊材料的制备、以及材料加工条件的选择具有十分重要的科学意义和实际应用价值。

K+掺杂改性的Ca3Co4O9基氧化物热电性能

用溶胶-凝胶法和放电等离子烧结(SPS)制备了层片状结构的(Ca1-xKx)3Co4O4陶瓷,烧结块体相对密度可达97%～99%.XRD(X-ray Diffraction)和SEM(Scanning Electronic Microscope)分析结果表明当K的掺杂量x＜0.08时为单一的Ca3Co4O9相,SPS烧结可以使样品带有一定的织构取向.在室温至700℃的范围内测量了不同K掺杂量时样品电导率和Seeback系数,测试结果表明,当K的掺入量小于0.06时,随着掺入量的增加,可以显著提高样品的电导率(400℃～700℃)和Seebeck系数.其中,700℃时(K0.06Ca0.94)3Co4O9样品的功率因子P=4.43×10-4W·m.-1K-2,与Ca3Co4O9(P=3.51×10-4W.m.-1K-2)相比提高了26.2%,表明K掺杂是改善Ca3Co4O9高温热电性能的有效途径之一.

对比切削与胶态成型工艺制作的氧化锆陶瓷的透光性与遮色效果

目的:利用切削素烧瓷块法与三维(three dimensional,3D)胶态成型法制作遮色效果不同的3种氧化锆陶瓷,对比其在不同厚度下的透光性及对异色离体牙的遮色效果,为临床口腔修复提供材料选择依据。方法:制备90片直径14 mm的A2色氧化锆圆盘试件,分成3组(n=30):(1)CZ组,采用计算机辅助设计(computer aided design,CAD)/计算机辅助制造(computer aided manufacturing,CAM)切削素烧瓷块法;(2)NZW组,采用3D胶态成型法,试件内表面无多孔遮色层;(3)NZY组,采用3D胶态成型法,试件内表面有多孔遮色层。3组试件根据厚度0.6 mm、1.0 mm、1.5 mm再分成3个亚组(n=10)。选用因牙周病拔除的中、重度异色前牙10颗,唇面打磨成大于6 mm2×6 mm2的平面。暗盒中用Crystaleye比色仪在黑、白背景下分别测量9组试件的色度值(CIE1976-L*a*b*),计算透光性[半透性参数(translucency parameter,TP)]。将每组试件与牙齿唇面依次粘接并测量色度值。选标准比色片A2中1/3色度值作为对照,计算试件粘接后同对照色的色差ΔE。以One-way ANOVA和Bonferroni法对数据进行统计分析。结果:(1)3组氧化锆试件在0.6 mm、1.0 mm、1.5 mm厚度下的TP值分别为:CZ组14.09、12.31和10.45,NZW组19.84、16.54和12.44,NZY组14.81、13.16和11.92。每组试件的3个亚组间透光性均显示为0.6 mm组>1.0 mm组>1.5 mm组,厚度相同的亚组间透光性均显示为NZW组>NZY组>CZ组。(2)3组氧化锆试件粘接后在0.6 mm、1.0 mm、1.5 mm厚度下与对照色的色差ΔE分别为:CZ组10.77、9.94和8.50,NZW组6.84、5.89和5.29,NZY组4.16、3.92和3.67。每组试件的3个亚组间色差值均显示为0.6 mm组>1.0 mm组>1.5 mm组,厚度相同的亚组间色差值均显示为CZ组>NZW组>NZY组。结论:3种氧化锆试件在厚度相同的情况下,透光性均为3D胶态成型技术制作的内表面无遮色处理组试件最好,而遮色效果均为3D胶态成型技术制作的内表面有遮色处理组试件最好,且其厚度在0.6 mm时即可获得较好的遮色效果。

Investigation of La_(9.33)Si_6O_(26) Oxygen Ionic Conductor

La9.335i6O26 oxygen ionic conductor was synthesized by solid state reaction method. Its structure was deter- mined by single-crystal X-ray diffraction analysis at room temperature. The results showed that La9.33Si6O26 oxide has the apatite structure with space group P63/m. AC impedance measurements indicated that the oxides sintered in nitrogen have much higher conductivity than those sintered in air. The effects of grain boundaries on the conductivity were discussed.

Astrocytes protect dopaminergic neurons against aminochrome neurotoxicity

Astrocytes protect neurons by modulating neuronal function and survival.Astrocytes support neurons in several ways.They provide energy through the astrocyte-neuron lactate shuttle,protect neurons from excitotoxicity,and internalize neuronal lipid droplets to degrade fatty acids for neuronal metabolic and synaptic support,as well as by their high capacity for glutamate uptake and the conversion of glutamate to glutamine.A recent reported astrocyte system for protection of dopamine neurons against the neurotoxic products of dopamine,such as aminochrome and other o-quinones,were generated under neuromelanin synthesis by oxidizing dopamine catechol structure.Astrocytes secrete glutathione transferase M2-2 through exosomes that transport this enzyme into dopaminergic neurons to protect these neurons against aminochrome neurotoxicity.The role of this new astrocyte protective mechanism in Parkinson´s disease is discussed.

Ionic liquids for CO_(2) electrochemical reduction

Electrochemical reduction of CO_(2) is a novel research field towards a CO_(2)-neutral global economy and combating fast accelerating and disastrous climate changes while finding new solutions to store renewable energy in value-added chemicals and fuels.Ionic liquids(ILs),as medium and catalysts(or supporting part of catalysts)have been given wide attention in the electrochemical CO_(2) reduction reaction(CO_(2) RR)due to their unique advantages in lowering overpotential and improving the product selectivity,as well as their designable and tunable properties.In this review,we have summarized the recent progress of CO_(2) electro-reduction in IL-based electrolytes to produce higher-value chemicals.We then have highlighted the unique enhancing effect of ILs on CO_(2) RR as templates,precursors,and surface functional moieties of electrocatalytic materials.Finally,computational chemistry tools utilized to understand how the ILs facilitate the CO_(2) RR or to propose the reaction mechanisms,generated intermediates and products have been discussed.

Physicochemical properties and structure of fluid at nano-/micro-interface:Progress in simulation and experimental study

In modern chemical engineering processes, the involvement of solid/fluid interface is the most important component of process intensification techniques, such as confined membrane separation and catalysis. In the review, we summarized the research progress of the latest theoretical and experimental works to elucidate the contribution of interface to the fluid properties and structures at nano-and micro-scale. We mainly focused on water, alcohol aqueous solution, and ionic liquids, because they are classical systems in interfacial science and/or widely involved in the industrialization process. Surface-induced fluids were observed in all reviewed systems and played a critical role in physicochemical properties and structures of outside fluid. It can even be regarded as a new interface, when the adsorption layer has a strong interaction with the solid surface. Finally, we proposed a perspective on scientific challenges in the modern chemical engineering processes and outlined future prospects.

Effect of structural variation in biomass-derived nonfluorinated ionic liquids electrolytes on the performance of supercapacitors

There is a growing interest in sustainable and high performance supercapacitors(SCs) operating at elevated temperatures as they are highly demanded in heat-durable electronics. Here, we present a biomass-derived nonfluorinated ionic liquid(IL) [P_(4444)][HFuA] and its structural analogue [P_(4444)][TpA]as electrolytes for supercapacitors comprising multiwall carbon nanotubes and activated charcoal(MWCNTs/AC) mixed carbon composite electrodes. A detailed investigation of the effect of scan rate, temperature, potential window and orientation of ions on the electrodes surfaces is performed. The supercapacitors exhibited relatively lower specific capacitance for both [P_(4444)][HFuA] and [P_(4444)][TpA] ILs at room temperature. However, the specific capacitance has significantly increased with an increase in temperature and potential window. The equivalent serie resistances of the SCs is deceased with increasing temperatures, which is a result of improved ionic conductivities of the IL electrolytes. In CV cycling at60 °C, the capacitor with [P_(4444)][HFuA] IL-based electrolyte retained about 90% of its initial capacitance,while the capacitor with [P_(4444)][TpA] IL-based electrolyte retained about 83% of its initial capacitance.Atomistic computations revealed that the aromatic [FuA]^(-) and [TpA]^(-) anions displayed perpendicular distribution that can effectively neutralize charges on the carbon surfaces. However, the [HFuA]-anion exhibited somewhat tilted configurations on the carbon electrode surfaces, contributing to their outstanding capacitive performance in electrochemical devices.

Activity and Stability of Rare Earth-Based Hydride Alloys as Catalysts of Hydrogen Absorption-Oxidation Reactions

Rare earth-based AB(5)-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the metahydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged, at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.

Non-Uniform FFT and Its Applications in Particle Simulations

Ewald summation method, based on Non-Uniform FFTs (ENUF) to compute the electrostatic interactions and forces, is implemented in two different particle simulation schemes to model molecular and soft matter, in classical all-atom Molecular Dynamics and in Dissipative Particle Dynamics for coarse-grained particles. The method combines the traditional Ewald method with a non-uniform fast Fourier transform library (NFFT), making it highly efficient. It scales linearly with the number of particles as , while being both robust and accurate. It conserves both energy and the momentum to float point accuracy. As demonstrated here, it is straight- forward to implement the method in existing computer simulation codes to treat the electrostatic interactions either between point-charges or charge distributions. It should be an attractive alternative to mesh-based Ewald methods.

Effect of dimethyl carbonate on the behavior of water confined in carbon nanotube

The dehydration of water by dimethyl carbonate(DMC)is of great significance for its application in electrochemistry and oil industry.With the rapid development of nanomaterial,one-dimensional(e.g.carbon nanotube(CNT))and two-dimensional(e.g.lamellar graphene)materials have been widely used for molecular sieving.In this work,the molecular behavior of dimethyl carbonate/water mixture confined in CNT with varying diameters was studied based on molecular dynamics simulation.Due to different van der Waals interactions for the components in the mixtures with the solid surface,DMC molecules are preferentially adsorbed on the inner surface of the pore wall and formed an adsorption layer.Comparing with the pure water molecules confined in CNT,the adsorption DMC layer shows notable effect on the local compositions and microstructures of water molecules under nanoconfinement,which may result in different water mobility.Our analysis shows that the surface-induced DMC molecules can destroy the hydrogen bonding network of water molecules and result in an uniform and dispersed distribution of water molecules in the tube.These clear molecular understandings can be useful in material design for membrane separation.

Electrochemical CO_(2) reduction with ionic liquids: review and evaluation

The increasing CO_(2) emission,as the chief culprit causing numerous environmental problems,could be addressed by the electrochemical CO_(2) reduction(CO_(2)R)to the added-value carbon-based chemicals.Ionic liquids(ILs)as electrolytes and co-catalysts have been widely studied to promote CO_(2)R owing to their unique advantages.Among the potential products of CO_(2)R,those only containing one carbon atom,named C1 products,including CO,CH_(3)OH,CH_(4),and syngas,are easier to achieve than others.In this study,we first summarized the research status on CO_(2)R to these C1 products,and then,the state-of-theart experimental results were used to evaluate the economic potential and environmental impact.Considering the rapid development in CO_(2)R,future scenarios with better CO_(2)R performances were reasonably assumed to predict the future business for each product.Among the studied C1 products,the research focuses on CO,where satisfactory results have been achieved.The evaluation shows that producing CO via CO_(2)R is the only profitable route at present.CH3OH and syngas of H2/CO(1:1)as the targeted products can become profitable in the foreseen future.In addition,the life cycle assessment(LCA)was used to evaluate the environmental impact,showing that CO_(2)R to CH4 is the most environmentally friendly pathway,followed by the syngas of H_(2)/CO(2:1)and CO,and the further improvement of the CO_(2)R performance can make all the studied C1 products more environmentally friendly.Overall,CO is the most promising product from both economic and environmental impact aspects.

Emerging strategies and developments in oxygen reduction reaction using high-performance platinum-based electrocatalysts

The global practical implementation of proton exchange membrane fuel cells(PEMFCs)heavily relies on the advancement of highly effective platinum(Pt)-based electrocatalysts for the oxygen reduction reaction(ORR).To achieve high ORR performance,electrocatalysts with highly accessible reactive surfaces are needed to promote the uncovering of active positions for easy mass transportation.In this critical review,we introduce different approaches for the emerging development of effective ORR electrocatalysts,which offer high activity and durability.The strategies,including morphological engineering,geometric configuration modification via supporting materials,alloys regulation,core-shell,and confinement engineering of single atom electrocatalysts(SAEs),are discussed in line with the goals and requirements of ORR performance enhancement.We review the ongoing development of Pt electrocatalysts based on the syntheses,nanoarchitecture,electrochemical performances,and stability.We eventually explore the obstacles and research directions on further developing more effective electrocatalysts.

Stereochemical editing:Catalytic racemization of secondary alcohols and amines

Chiral alcohols and amines are important structural units widely existing in pharmaceuticals,agrochemicals,and food additives.Dynamic kinetic resolution(DKR)is an efficient strategy to deliver optically active alcohols and amines from their racemates.For the development of DKR method,racemization catalyst plays as a crucial element with the requirement of compatibility with the kinetic resolution(KR)system.In this paper,recent advance in the catalytic racemization of secondary alcohols and amines is summarized based on different types of racemizing intermediates,which are redox racemization via ketone/imine intermediates,racemization via radical intermediates,and racemization via carbocation intermediates.Enzymatic racemization of secondary alcohols and amines is also enclosed.

Cracking Behavior in Additively Manufactured Pure Tungsten

In this study, near fully dense(96.5%) pure tungsten bulks were additively manufactured and the cracking behavior was investigated. A crack network with a spacing of ～100 lm was observed in the fabricated bulks. It was observed that the laser scanning strategy, which could tailor the microstructure, affected the crack distribution pattern in fabricated tungsten.The calculated surface temperature difference(7300 K) was much higher than the cracking criterion(800 K) of tungsten,indicating that cracking is almost inevitable in laser additive manufacturing of tungsten. It could be concluded that crack network formed because the cracks emerged in every laser molten track and then interconnected in the layer-by-layer building process.

Dual Targeting to Mitochondria and Chloroplasts： Characterization of Thr-tRNA Synthetase Targeting Peptide

There is a group of proteins that are encoded by a single gene, expressed as a single precursor protein and dually targeted to both mitochondria and chloroplasts using an ambiguous targeting peptide. Sequence analysis of 43 dual targeted proteins in comparison with 385 mitochondrial proteins and 567 chloroplast proteins ofArabidopsis thaliana revealed an overall significant increase in phenylalanines, leucines, and serines and a decrease in acidic amino acids and glycine in dual targeting peptides （dTPs）. The N-terminal portion of dTPs has significantly more serines than mTPs. The number of arginines is similar to those in mTPs, but almost twice as high as those in cTPs. We have investigated targeting determinants of the dual targeting peptide of Thr-tRNA synthetase （ThrRS-dTP） studying organellar import of N- and C-terminal deletion constructs of ThrRS-dTP coupled to GFR These results show that the 23 amino acid long N-terminal portion of ThrRS-dTP is crucial but not sufficient for the organellar import. The C-terminal deletions revealed that the shortest peptide that was capable of conferring dual targeting was 60 amino acids long. We have purified the ThrRS- dTP（2-60） to homogeneity after its expression as a fusion construct with GST followed by CNBr cleavage and ion exchange chromatography. The purified ThrRS-dTP（2-60） inhibited import of pF1β into mitochondria and of pSSU into chloroplasts at μM concentrations showing that dual and organelle-specific proteins use the same organellar import pathways. Furthermore, the CD spectra of ThrRS-dTP（2-60） indicated that the peptide has the propensity for forming α-helical structure in membrane mimetic environments; however, the membrane charge was not important for the amount of induced helical structure. This is the first study in which a dual targeting peptide has been purified and investigated by biochemical and biophysical means.

Oxide dispersion strengthened stainless steel 316L with superior strength and ductility by selective laser melting

Dense oxide dispersion strengthened(ODS) 316 L steels with different amount of Y2O3 additions were succe s s fully fabricated by selective laser melting(SLM) even though part of the added Y2O3 got lost during the process.The microstructure was characterized in details and the mechanical properties were tested at room temperature,250℃ and 400℃,respectively.The effect of the scanning speed on agglomeration of nanoparticles during SLM process was discussed.Superior properties,e.g.,yield strength of 574 MPa and elongation of 91%,were achieved at room temperature in SLM ODS 316 L with additional 1% of Y2 O3.At elevated temperature s,the strength kept high but the elongations dropped dra matically.It was observed that nano-voids nucleated throughout the whole gauge section at the sites where nanoinclusions located.The growth and coalescence of these voids were suppre s sed by the formation of an element segregation network before necking,which relieved local stress concentration and thus delayed necking.This unusual necking behavior was studied and compared to the previous theory.It appeared that the strong convection presented in the melt pool can evenly redistribute the short-time milled coarse Y2O3 precursor powder during SLM process.These findings can not only solve the problems encountered during the fabrication of ODS components but also replenish the strengthening mechanism of SLM 316 L thus pave a way for further improving of mechanical properties.

Effect of Build Direction on Fatigue Performance of L-PBF 316L Stainless Steel

The microstructure and fatigue and tensile properties of 316 L stainless steel fabricated via laser powder bed fusion(L-PBF)were investigated.Two 316 L stainless steel specimens with different loading directions which are either perpendicular to or parallel to building direction were prepared by L-PBF process.The results of X-ray diffraction tomography showed that there was no significant difference in morphology and size/distribution of the defects in the HB and VB samples.Since long axis of columnar grains is generally parallel to the build direction,the fatigue crack encounters more grain boundaries in VB samples under cyclic loading,which led to enhanced fatigue resistance of VB samples compared with HB sample.In contrast to HB sample,the VB sample has a higher fatigue strength due to a higher resistance to localized plastic deformation under cyclic loading.The differences in fatigue properties of L-PBF 316 L SS with different build directions were predominantly controlled by solidification microstructures.

A review of tungsten fabricated via laser powder bed fusion

Tungsten and its alloys with high strength,thermal conductivity,and plasma radiation resistance are highly desirable for applications in medical,electronic and also nuclear facilities.However,the high melting point and high ductile–brittle transition temperature limit the fabrication of complex parts by using traditional methods,such as powder metallurgy.As a kind of additive manufacturing technology,laser powder bed fusion(LPBF)was used to fabricate tungsten and its alloys in recent years because of its high energy density and low action time.This paper reviewed the recent progress of LPBF fabricated tungsten.Two main challenges,which are the lack of density and cracking problem,are focused.The methods to solve these problems are reviewed.In terms of improving the density,decreasing oxygen content,optimizing the process parameter,and adopting spherical powder were proved effective.In terms of cracking problem,the method of alloying,such as adding secondary phase nanoparticles and alloy elements,could significantly reduce the cracking density.However,the crack problem has not been completely solved up to now.Finally,future developments and potential new research directions for LPBF tungsten are proposed.