Advantageous properties of halide perovskite quantum dots towards energy-efficient sustainable applications

As lead halide perovskite(LHP)semiconductors have shown tremendous promise in many application fields,and particularly made strong impact in the solar photovoltaic area,low dimensional quantum dot forms of these perovskites are showing the potential to make distinct marks in the fields of electronics,optoelectronics and photonics.The so-called perovskite quantum dots(PQDs)not only possess the most important features of LHP materials,i.e.,the unusual high defect tolerance,but also demonstrate clear quantum size effects,along with exhibiting desirable optoelectronic properties such as near perfect photoluminescent quantum yield,multiple exciton generation and slow hot-carrier cooling.Here,we review the advantageous properties of these nanoscale perovskites and survey the prospects for diverse applications which include lightemitting devices,solar cells,photocatalysts,lasers,detectors and memristors,emphasizing the distinct superiorities as well as the challenges.

AXISYMMETRIC CONTACT PROBLEM OF CUBIC QUASICRYSTALLINE MATERIALS

The axisymmetric elasticity theory of cubic quasicrystal was developed in Ref. [1]. The axisymmetric elasticity problem of cubic quasicrystal is reduced to a single higher-order partial differential equation by introducing a displacement function, based on which, the exact analytic solutions for the elastic field of an axisymmetric contact problem of cubic quasicrystalline materials are obtained for universal contact stress or contact displacement. The result shows that if the contact stress has order - 1/2 singularity on the edge of the contact domain, die contact displacement is a constant in the contact domain. Conversely, if the contact displacement is a constant, the contact stress must have order - 1/2 singularity on the edge of die contact domain.

The Effect of Condensation on the Morphology and Magnetic Properties of Modified Barium Hexaferrite(BaFe_(12)O_(19))

We present a comparison for the effect of condensation on the morphology and magnetic prop erties of oleic acid modified BaFe_(12)O_(19) nanoparticles.Two different samples of BaFe_(12)O_(19) nanoparticles were synthesized by dehydration(Z1) and rotary evaporation(Z2) method,respectively.Oleic acid was used as the surface modification agent to observe the morphological and magnetic changes.The nanoparticles were analyzed by XRD,FTIR,TGA,SEM,and VSM techniques for structural and physicochemical characteris tics.Crystallographic analysis reveals the phase as hexaferrite and the average crystallite size of Z1 and Z2 is 21±3 nm and 17±2 nm,respectively.Rotary evaporator accelerates the condensation process in viscous gel(Z2).Due to the use of rotary evaporator,the coating with oleic acid for Z2 product has been accomplished very well,as compared with Z1.As a result,saturation magnetization of Z2 sample is much lower than that of Z1 sample.

Effect of Hydrolyzing Agents on the Properties of Poly(Ethylene Glycol)-Fe_3O_4 Nanocomposite

Poly(ethylene glycol)(PEG) assisted hydrothermal route has been used to study the influence of the hydrolyzing agent on the properties of PEG-iron oxide(Fe_3O_4) nanocomposites.Iron oxide nanoparticles(NPs),as confirmed by X-ray diffraction analysis,have been synthesized by a hydrothermal method in which Na OH and NH_3 were used as hydrolyzing agents.Formation of PEG-Fe_3O_4 nanocomposite was confirmed by Fourier transform infrared spectroscopy(FTIR).Samples exhibit different crystallite sizes,which estimated based on line profile fitting as 10 nm for NH_3 and 8 nm for Na OH hydrolyzed samples.The average particle sizes obtained from transmission electron microscopy was respectively 174±3 nm for Na OH and 165±4 nm for NH3 gas hydrolyzed samples.Magnetic characterization results reveal superparamagnetic characteristics despite a large particle size,which indicate the absence of coupling between the nanocrystals due to the presence of polymer in the nanocomposites.The conductivity curve demonstrates that σDC is strongly temperature dependent.

A ggregation-induced emission nanoparticles for in vivo three-photon fuorescence microscopic rat brain angiography

Rodents are popular biological models for physiological and behavioral research in neuroscience and rats are better models than mice due to their higher genome similarity to human and more accessible surgical procedures.However,rat brain is larger than mice brain and it needs powerful imaging tools to implement better penetration against the scattering of the thicker brain tissue.Three-photon fluorescence microscopy(3PFM)combined with near-infrared(NIR)excitation has great potentials for brain circuits imaging beause of its abilities of anti scattering,deep-tissue imaging,and high signal-to-noise ratio(SNR).In this work,a type of AIE lumninogen with red fuorescence was synthesized and encapsulated with Pluronic F-127 to make up form nano-particles(NPs).Bright DCDPP-2TPA NPs were employed for in trino three-photon fuorescent laser scanning microscopy of blood vessels in rats brain under 1550 nm femtosecond laser exci-tation.A fine three-dimensional(3D)reconstruction up to the deepness of 600 pm was achieved and the blood flow velocity of a selected vessel was measured in vrito as well.Our 3PFM deep brain imaging method simultaneously recorded the morphology and function of the brain blood vessels in vivo in the rat model.Using this angiography combined with the arsenal of rodent's brain disease,models can accelerate the neuroscience research and clinical diagnosis of brain disease in the future.

Study on Characteristics of Crystal Growth of NdFeB Cast Alloys

The characteristic of crystal growth of NdFeB cast alloys was studied. It is found that the crystal growth orientation of conventional ingots is along <410> or <411>. As the cooling rate increases, the crystallization orientation changes from a axis to c axis, along which the grain is easy to be magnetized. Meanwhile, by analyzing the change of crystallization orientation, the influence on the property of magnets was discussed.

Development of Strip Casting Technology in Rare Earth Permanent Magnet Alloys and Hydrogen Storage Alloys in China

The SC technique is now being applied widely in material preparation, especially in rare earth functional materials in virtue of its advanced process and high performance product. The applications of SC technique in rare earth permanent magnet alloys and hydrogen storage alloys were analyzed integrative, on the basis of summary of SC technique development in this paper. The paper mainly includes development history of SC technology, effect of SC technology on alloy microstructure, application of SC technology in RE storage hydrogen alloy and sintered Nd-Fe-B alloy, development of SC equipment and SC product industry. At the same time, the paper points out the existing problem of SC products.

CRACK PROBLEM UNDER SHEAR LOADING IN CUBIC QUASICRYSTAL

The axisymmetric elasticity problem of cubic quasicrystal is reduced to a single higher_order partial differential equation by introducing a displacement function. Based on the work, the analytic solutions of elastic field of cubic quasicrystal with a penny_shaped crack under the shear loading are found, and the stress intensity factor and strain energy release rate are determined.

Gold-catalyzed addition reaction between creatinine and isatin:A sustainable and green chemistry approach for the diastereoselective synthesis of 3-substituted-3-hydroxyisatins

The aldolization of various isatins with creatinine under gold catalysis in water has been developed.The reaction is operationally simple as the products can be isolated by simple filtration without requiring tedious solvent extraction and column chromatographic techniques.The generality of this methodology is showcased through the reactions of a wide range of isatin derivatives with creatinine to afford the respective aldol products in excellent yields with complete syn‐selectivity.The scope of this chemistry is further extended to a tandem reaction involving isatins,creatinine and malononitrile to afford multicomponent products in excellent yields with complete anti‐selectivity.The antioxidant potency of the synthesized compound was assessed by a spectrophotometric method,which revealed that three compounds containing halogen atoms(2c,2d and2e)were the most active compared with the standard.

Synthesis and Biological Evaluation of Novel 6-(3-(4,5-Dihydro-1,5-diphenyl-1<i>H</i>-pyrazol-3-yl)phenylamino) Pyridazin-3(2H)-one Derivatives

Pyrazoles are important nitrogen containing 5-membered heterocyclic compounds. Numerous pyrazoline derivatives have been found to possess considerable biological activities, which stimulated the research activity in this field. Several 1,3,5-Triphenyl-1H-pyrazole containing 6-aminopyridazin-3(2H)-one derivatives has been synthesized. These new compounds were characterized using IR, 1H-NMR and Mass spectra and Elemental analysis. They possess some potent biological activities. Therefore biological screening of novel compounds has been also done.

A facile design for multifunctional AIEgen based on tetraaniline derivatives

Aniline oligomers have been widely used in many fields due to their excellent physicochemical properties. Owing to strong intermolecular interactions, their emission is always weakened or quenched when they are in high concentration or aggregated state, which greatly limits their fluorescent applications. Inspired by the concept of aggregation-induced emission(AIE), herein we introduced large steric groups onto the aniline oligomer to prevent the formation of packing structure. In particular, diphenyl vinyl group was bonded with oligomeric tetraaniline by a facile synthetic procedure with high yield. The obtained aniline oligomer derivative exhibited typical AIE features, which was also confirmed by density functional theoretical calculation. More importantly, this AIE oligomer was able to detect Fe^(3+) ions selectively and quantitatively. The fluorescence intensity decreased linearly along with the increment of Fe^(3+) concentration. Moreover, we demonstrated that this AIE oligomer could stain live bacteria, such as E. coli and S. aureus efficiently. All these results suggest that such a readily accessible and multifunctional tetraaniline derivative provides a new platform for the construction of fluorescent materials.

Palladium nanoparticles supported on amine-functionalized glass fiber mat for fixed-bed reactors on the effective removal of hexavalent chromium by catalytic reduction

Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.

Tailoring magnetic hysteresis of additive manufactured Fe-Ni permalloy via multiphysics-multiscale simulations of process-property relationships

Designing the microstructure of Fe-Ni permalloy produced by additive manufacturing(AM)opens new avenues to tailor its magnetic properties.Yet,AM-produced parts suffer from spatially inhomogeneous thermal-mechanical and magnetic responses,which are less investigated in terms of process modeling and simulations.We present a powder-resolved multiphysics-multiscale simulation scheme for describing magnetic hysteresis in AM-produced material,explicitly considering the coupled thermal-structural evolution with associated thermo-elasto-plastic behaviors and chemical order-disorder transitions.The residual stress is identified as the key thread in connecting the physical processes and phenomena across scales.By employing this scheme,we investigate the dependence of the fusion zone size,the residual stress and plastic strain,and the magnetic hysteresis of AM-produced Fe_(21.5)Ni_(78.5) on beam power and scan speed.Simulation results also suggest a phenomenological relation between magnetic coercivity and average residual stress,which can guide the magnetic hysteresis design of soft magnetic materials by choosing appropriate processing parameters.

Effect of Gd addition on the superconducting properties of Ti-based V, Nb, Ta alloys

The critical current density(Jc)of the body centered cubic(bcc)V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix[S.Paul,et.al,IEEE Trans.Appl.Supercond.31,5(2021)].Very low solubility of Gd in other bcc elements like Ta and Nb is also well known[Jr.KA Gschneidner in Prog Sci Technol Rare Earths,vol.1,pp.222–258,1964&M Neuberger,et.al in Handbook of Electronic Materials,Vol 4,1972].We use these facts to find the effect of adding 1 at.%Gd into the Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys on the superconducting properties e.g.,the transition temperature(Tc),Jc,flux pinning force density(Fp)and the microstructure.In spite of Gd being ferromagnetic,the Tc in these alloys change only marginally(increase by 0.3 K in Ta0.4Ti0.6 and decrease by 0.15 K in Nb0.6Ti0.4 after Gd addition.The Jc(H?1 T,T=4 K)increases by 5 and 1.5 times respectively in the Gd containing Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys,which is quite small as compared to the increase observed in the V0.6Ti0.4(20 times)system.With Gd addition,the grain size reduces approximately by 65%and 10%respectively in Nb0.6Ti0.4 and Ta0.4Ti0.6.Our analysis indicates that grain boundaries are the major flux line pinning centres in these alloys and the role of Gd in increasing the Jc depends on the effectiveness of Gd in reducing the grain size.The grain boundary density depends strongly on the distribution of Gd precipitates,which is quite different from each other for two alloy systems under study.Moreover,our results suggest that the addition of Gd to commercial Nb‐Ti(Nb0.37Ti0.63)alloy is a new promising route for achieving higher Jc values.

Influence of Al/Cu content on grain boundary diffusion in Nd-Fe-B magnet via in-situ observation

The influence of aluminum and copper content in the starting Nd-Fe-B magnet on grain boundary diffusion process(GBDP) was studied by observing the phase transformation behaviors of the magnets in-situ at high temperature. A higher coercivity increment is discovered in the sample with higher AI/Cu despite the fact that its Dy diffusion amount is the same as the other. DSC analysis shows an evident melting behavior in the higher Al/Cu sample. Laser scanning confocal microscopy(LSCM) in-situ characterization shows a large amount of melted intergranular phase spills out to the surface simultaneously at around 600 ℃ in the high Al/Cu sample, while the phase spills out gradually one after another in the range between 623 and680 ℃ in the other sample, which indicates that the intergranular phase can be more easily melted in the sample containing more AI/Cu. The area fraction of matrix phase remarkably shrinks while that of intergranular phase enlarges after LSCM heating, which demonstrates the outer region of the Nd_2 Fe_(14)B grains melt at the temperature of 900 ℃. Electron probe microanalyzer result(EPMA) shows that the Nd and Dy concentrate in edge regions and subsequently mix into the intergranular phase with the melting of the grain edge, while a large amount of AI and Cu in the intergranular phase spill out. Nevertheless, the sample with higher starting AI/Cu still remains higher residual contents after LSCM experiments, and that could probably be the main reason why the high AI/Cu magnet shows smaller coercivity decrement after LSCM experiment. Overall, the increase of AI/Cu in the starting magnet optimizes the Dy distribution and the wettability of intergranular phase, enhancing coercivity increment effect further.

Gadolinium doped tin dioxide nanoparticles: an efficient visible light active photocatalyst

Photocatalytic degradation of phenol with sol-gel prepared rare earth doped tin dioxide （SnO2） nanoparticles was reported. Gadolinium doped tin dioxide （SnO2：Gd） nanoparticles were found to absorb higher visible light compared to lanthanum, neodymium and cerium doped materials that were studied in detail. Photocatalytic degradation of phenol under artificial white light and sunlight in the presence of SnO2：Gd nanoparticles was studied with high performance liquid chromatography （HPLC）, capillary electrophoresis （CE）, total organic carbon （TOC） measurements and the determination of chemical oxygen demand （COD）. Clear correlations be- tween the results obtained from these multiple measurements were found, and a kinetic pathway for the degradation process was pro- posed. Within 150 min of solar irradiation, the TOC of a 10 ppm phenol solution in water was reduced by 95%-99%, thus demon- strating that SnO2：Gd nanoparticles are efficient visible light photocatalysts.

Fabrication of ultrafine ZnFe2O4 nanoparticles for efficient photocatalytic reduction CO2 under visible light illumination

A one-pot, solvent-thermal process was used to create the ultrafine ZnFe2O4nanoparticles photocatalyst.During the solvent-thermal process, the in situ self-forming NaCl not only served as a "cage" to confine the ion diffusion, but also acted as a microreactor for nanocrystallite growth. An average particle size of ～10 nm and a high-specific surface area of～112.9 m2/g were observed for the ultrafine ZnFe2O4nanoparticles Owing to the synergistic effect of ultrafine particle size, the full utilization of the visible light region and high conduction band(CB) position, ultrafine ZnFe2O4photocatalyst displayed an efficient photocatalytic CO2reduction under visible light illumination. Besides, the ultrafine ZnFe2O4photocatalyst showed high production selectivity for CH3CHO and C2H5OH generation in aqueous CO2/NaHCO3solution. This work may provide a new idea for the synthesis of new high-efficiency photocatalysts.

3D non-isothermal phase-field simulation of microstructure evolution during selective laser sintering

During selective laser sintering(SLS),the microstructure evolution and local temperature variation interact mutually.Application of conventional isothermal sintering model is thereby insufficient to describe SLS.In this work,we construct our model from entropy level,and derive the non-isothermal kinetics for order parameters along with the heat transfer equation coupled with microstructure evolution.Influences from partial melting and laser-powder interaction are also addressed.We then perform 3D finite element non-isothermal phase-field simulations of the SLS single scan.To confront the high computation cost,we propose a novel algorithm analogy to minimum coloring problem and manage to simulate a system of 200 grains with grain tracking algorithm using as low as 8 non-conserved order parameters.Specifically,applying the model to SLS of the stainless steel 316L powder,we identify the influences of laser power and scan speed on microstructural features,including the porosity,surface morphology,temperature profile,grain geometry,and densification.We further validate the first-order kinetics of the transient porosity during densification,and demonstrate the applicability of the developed model in predicting the linkage of densification factor to the specific energy input during SLS.

Creation of passivated Nb/N p-n co-doped ZnO nanoparticles and their enhanced photocatalytic performance under visible light illumination

Passivated niobium/nitrogen(Nb-N) p-n co-doped zinc oxide nanoparticles were created by a simple precipitation process with in-situ self-formed NaCl "cage" to confine the nanoparticle growth followed by the heat treatment in a flow of ammonia gas. Enhanced optical absorbance into the visible light region was observed in the Nb/N co-doped ZnO nanoparticle photocatalyst due to the Nb/N co-doping effect.It demonstrated a largely enhanced photocatalytic performance in the disinfection of Escherichia coli bacteria under visible light illumination, which could be attributed to the passivated co-doping of NbN to suppress the photogenerated charge carrier recombination on dopants. This robust approach for passivated p-n co-doping may also be applied to other material systems for a wide range of technical applications.

Dy gradient and coercivity in grain boundary diffusion processed Nd-Fe-B magnet

By controlling Dy vapor deposition process, the amount of Dy that diffused into the magnet was increased gradually from 0.1 wt.% to 0.3 wt.%. Compared with the original status, the coercivity increment was not proportional to the Dy diffusion amount. Subsequent H（cj） and Dy content gradient data showed that slope of the 0.3 wt.% sample gradient was bigger than that of 0.1 wt.% one, and the gaps between outer flakes and inner flakes enlarged with the increasement of Dy diffusion amount. Although Dy mostly enriched in triple-junction regions in electron-probe microscope analysis（EPMA） images, the following Auger depth graph showed that Dy content was as high as 3.0 at.% in 1.5 mm deep center. It proved that Dy tended to get into the main phase rather than stayed in the grain boundary during the diffusion process, and over-diffusion of Dy in the main phase was unhelpful for the coercivity enhancement.