应用质量控制方法完善金属框强度分析工作

应用质量控制(QC)方法,开展以完善金属框强度分析工作、提高金属框强度分析效率为目标的研究.针对统计结果中框分析所用工时过多的情况,运用创新型QC方法,广泛提出创新方案,有理有据得出最优方案,并提出了有效对策加以实施.结果表明,应用QC方法,融合信息化技术,金属框强度分析工作效率得到了有效提高,进而缩短了民机结构研发周期.最后,指出QC方法是完善金属框强度分析工作的有效方法.

用吊环和∏型金属框拉膜测量液体表面张力系数的讨论

为了讨论拉脱法测量液体表面张力时用吊环和用∏型金属框拉膜的测量结果,在不同温度下分别对纯净水、乙醇和甘油三种常见液体的表面张力系数进行了测量,得出了吊环和∏型金属框各有优点,但用吊环测量的数据稳定性要优于∏型金属框。

对称母线旋转体菱形金属框支撑维护结构的建模分析

以某个对称母线旋转体围护结构的支撑结构建模为例,分析其几何特性和实物模型的可行性。从几何角度分析,对称母线旋转体形成的菱形网格具有左右对称性和四点不共面的特性;母线沿旋转体径向倾斜时,旋转体的的外形存在收腰现象。从扭转定型和构造匹配的角度分析了连续扭转的支撑构件的可行性,从相邻菱形单元表面与支撑构件夹角相等的角度分析了菱形单元框的成型合理性。对上述分析给出相似工程相应的结论和参考性意见。

金属框结构对碲镉汞红外焦平面调制传递函数的影响

调制传递函数(MTF)值是表征碲镉汞(HgCdTe)红外探测器成像性能的重要参数。串音是减小探测器MTF值的主要因素之一。合理的器件结构设计可有效地抑制串音,从而提高器件MTF值。介绍了一种含金属框结构的HgCdTe红外焦平面探测器,该器件可有效吸收横向扩散光生载流子并减小器件的串音干扰。对含金属框结构的器件和无金属框结构的器件进行MTF测试及对比分析。测试结果表明,与无金属框结构的器件相比,含金属框结构的器件的MTF值得到显著提高。

金属轨道的形状影响感应电流的大小吗——以2020年全国高考物理3卷的压轴题为例

剖析2020全国高考物理3卷一道压轴题目的创新之处;分析这道压轴题目难度设置不大的原因;更改部分条件,将这道压轴题目变式为两个材料背景类似,但解题难度稍大的题目,并给出这两个变式的解析.

Improvement of ionic conductivity of solid polymer electrolyte based on Cu-Al bimetallic metal-organic framework fabricated through molecular grafting

A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.

An efficient strategy for the preparation of MIL-53(Al)-NH_(2)membranes with high ion selectivity and desalination performance

The efficient extraction of sodium(Na^(+))and lithium(Li^(+))from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries.However,coexisting cations such as divalent calcium(Ca^(2+))and magnesium(Mg^(2+))ions are at the subnanometer scale in diameter,similar to target monovalent ions,making ion separation a great challenge.Here,we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH_(2)membranes on the surface of anodic aluminum oxide.Such membranes contain angstrom-scale(~7Å)channels for the entrance of small monovalent ions and water molecules,endowing the selectivities for monovalent cations over divalent cations and water over salt molecules.The resulting high-connectivity MIL-53(Al)-NH_(2)membranes exhibit excellent ion separation performance(a selectivity of 121.42 for Na^(+)/Ca^(2+)and 93.81 for Li^(+)/Mg^(2+))and desalination performance(a water/salt selectivity of up to 5196).This work highlights metal–organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.

Enhancing photo-generated carriers transfer of K-C_(3)N_(4)/UiO-66-NH_(2) with Er doping for efficient photocatalytic oxidation of furfural to furoic acid

Biomass-derived platform molecules,such as furfural,are abundant and renewable feedstock for valuable chemical production.It is critical to synthesize highly efficient photocatalysts for selective oxidation under visible light.The Er@K-C_(3)N_(4)/UiO-66-NH_(2) catalyst was synthesized using a straight-forward hydrothermal technique,and exhibited exceptional efficiency in the photocatalytic oxidation of furfural to furoic acid.The catalyst was thoroughly characterized,confirming the effective adjustment of the band gap energy of Er@K-C_(3)N_(4)/UiO-66-NH_(2).Upon the optimized reaction conditions,the conversion rate of furfural reached 89.3%,with a corresponding yield of furoic acid at 79.8%.The primary reactive oxygen species was identified as·O_(2)^(-) from ESR spectra and scavenger tests.The incorporation of Er and K into the catalyst enhanced the photogenerated carriers transfer rate,hence increasing the separating efficiency of photogenerated electron-hole pairs.This study expands the potential applications of rare earth element doped g-C_(3)N_(4) in the photocatalytic selective oxidation of furfurans.

Temperature-feedback two-photon-responsive metal-organic frameworks for efficient photothermal therapy

The realization of real-time thermal feedback for monitoring photothermal therapy(PTT)under near-infrared(NIR)light irradiation is of great interest and challenge for antitumor therapy.Herein,by assembling highly efficient photothermal conversion gold nanorods and a temperature-responsive probe((E)-4-(4-(diethylamino)styryl)-1-methylpyridin-1-ium,PyS)within MOF-199,an intelligent nanoplatform(AMPP)was fabricated for simultaneous chemodynamic therapy and NIR light-induced temperature-feedback PTT.The fluorescence intensity and temperature of the PyS probe are linearly related due to the restriction of the rotation of the characteristic monomethine bridge.Moreover,the copper ions resulting from the degradation of MOF-199 in an acidic microenvironment can convert H_(2)O_(2)into•OH,resulting in tumor ablation through a Fenton-like reaction,and this process can be accelerated by increasing the temperature.This study establishes a feasible platform for fabricating highly sensitive temperature sensors for efficient temperature-feedback PTT.

Metal-organic framework-derived porous carbon for the advanced aqueous zinc-ion hybrid capacitor

Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the low energy density and the lack of sustainable design strategies for the cathodes hinder the practical application of ZIHCs.Herein,we design the N and O co-doped porous carbon cathode by annealing metal-organic framework(ZIF-8).ZIF-8 retains the original dodecahedral structure with a high specific surface(2814.67 m^(2)/g)and I_(G)/I_(D) ratio of 1.0 during carbonization and achieves self-doping of N and O heteroatoms.Abundant defect sites are introduced into the porous carbon to provide additional active sites for ion adsorption after the activation of carbonized ZIF-8 by KOH treatment.The ZIHCs assembled with modified ZIF-8 as the cathode and commercial zinc foil as the anode show an energy density of 125 W∙h/kg and a power density of 79 W/kg.In addition,this ZIHCs device achieves capacity retention of 77.8%after 9000 electrochemical cycles,which is attributed to the diverse pore structure and plentiful defect sites of ZIF-8-800(KOH).The proposed strategy may be useful in developing high-performance metal-ion hybrid capacitors for large-scale energy storage.

刚性线圈所受磁场安培力规律的研究——以2022年全国高考物理乙卷24题为例

以2022年全国高考物理乙卷第24题为例,对刚性线圈所受磁场安培力的合力进行定量分析。为解决问题方便,提出一个引理和推论并分别进行证明。变换相关已知条件,给出与原来高考题目背景材料类似的几个不同变式,并分别进行解析。

拉脱法测液体表面张力系数实验的改进

文章用一种简单且操作性强的方法对拉脱法测量液体表面张力系数实验中常认为可以忽略的水膜的重力和金属框受到的浮力进行了修正。以测量30℃下蒸馏水的表面张力系数为例,将修正前后的液体表面张力系数数据进行了对比研究。

FD-NST-I型液体表面张力系数测定仪的改进

通过具体实验过程发现FD-NST-I型液体表面张力系数测定仪在测定液体的表面张力系数中所存在的缺陷,将吊环替换为倒立的"门"式金属框,有效克服了由于吊环不水平而引起的实验误差。

Nitrogen ligands in two-dimensional covalent organic frameworks for metal catalysis

We introduced bipyridine ligands into a series of two‐dimensional （2D） covalent organic frame‐works （COFs） using 2,2’‐bipyridine‐5,5’‐dicarbaldehyde （2,2’‐BPyDCA） as a component in the mixed building blocks. The framework of the COFs was formed by the linkage of imine groups. The ligand content in the COFs was synthetically tuned by the content of 2,2’‐BPyDCA, and thus the amount of metal, palladium（II） acetate, bonded to the nitrogen ligands could be manipulated. Both the bipyri‐dine ligands and imine groups can coordinate with Pd（II） ions, but the loading position can be var‐ied, with one ligand favoring binding in the space between adjacent COFs’ layers and the other lig‐and favoring binding within the pores of the COFs. The Pd（II）‐loaded COFs exhibited good catalytic activity for the Heck reaction.

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Metal-organic frameworks MOF-808-X as highly efficient catalysts for direct synthesis of dimethyl carbonate from CO_2 and methanol

A series of metal-organic frameworks MOF-808-X(6-connected)were synthesized by regulating the ZrOCl2·8H2O/1,3,5-benzenetricarboxylic acid(BTC)molar ratio(X)and tested for the direct synthesis of dimethyl carbonate(DMC)from CO2 and CH3OH with 1,1,1-trimethoxymethane(TMM)as a dehydrating agent.The effect of the ZrOCl2·8H2O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated.Results showed that a proper ZrOCl2·8H2O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X.MOF-808-4,with almost no redundant BTC or zirconium clusters trapped in the micropores,exhibited the largest surface area,micropore size,and the number of acidic-basic sites,and consequently showed the best activity among all MOF-808-X,with the highest DMC yield of 21.5% under the optimal reaction conditions.Moreover,benefiting from the larger micropore size,MOF-808-4 outperformed our previously reported UiO-66-24(12-connected),which had even more acidic-basic sites and larger surface area than MOF-808-4,mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores.Furthermore,a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results.The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.

Solvothermal synthesis of Co-substituted phosphomolybdate acid encapsulated in the UiO-66 framework for catalytic application in olefin epoxidation

Hybrid composites of phosphomolybdic acid@UiO-66(PMo12@UiO-66)and Co-substituted phosphomolybdic acid@UiO-66(PMo11Co@UiO-66)were synthesized using the direct solvothermal method.A variety of characterization results demonstrated that phosphomolybdic acid(PMo12)or Co-substituted phosphomolybdate acid(PMo11Co)clusters are uniformly dispersed in the cages of Zr-based metal-organic UiO-66 frameworks.The catalytic properties of these hybrid composites were investigated by applying the epoxidation of olefins with tert-butyl hydroperoxide as the oxidant.Compared to PMo12@UiO-66,PMo11Co@UiO-66 showed a much higher catalytic activity and was simply recovered by filtration and reused for at least ten runs without significant loss of catalytic activity.Particularly,PMo11Co@UiO-66 can efficiently convert cyclic olefins like limonenes to epoxides,and its selectivity to 1,2-limonene oxide reached 91%in the presence of a radical inhibitor such as hydroquinone.The excellent catalytic activity and stability of the hybrid composite PMo11Co@UiO-66 are mainly attributed to the uniform distribution of highly active PMo11Co units within the smaller cages of UiO-66,to the suitable surface polarity of the hybrid composite for facilitating the access of reagents and solvent,and to the strong interface-interactions between the polyoxometalate and the UiO-66 framework.

Hierarchically porous S-scheme CdS/UiO-66 photocatalyst for efficient 4-nitroaniline reduction

Unveiling the pore-size performance of metal organic frameworks(MOFs)is imperative for controllable design of sophisticated catalysts.Herein,UiO-66 with distinct macropores and mesopores were intentionally created and served as substrates to create advanced CdS/UiO-66 catalysts.The pore size impacted the spatial distribution of CdS nanoparticles(NPs):CdS tended to deposit on the external surface of mesoporous UiO-66,but spontaneously penetrated into the large cavity of macroporous UiO-66 nanocage.Normalized to unit amount of CdS,the photocatalytic reaction constant of macroporous CdS/UiO-66 over 4-nitroaniline reduction was~3 folds of that of mesoporous counterpart,and outperformed many other reported state-of-art CdS-based catalysts.A confinement effect of CdS NPs within UiO-66 cage could respond for its high activity,which could shorten the electron-transport distance of NPs-MOFs-reactant,and protect the active CdS NPs from photocorrosion.The finding here provides a straightforward paradigm and mechanism to rationally fabricate advance NPs/MOFs for diverse applications.

Two-dimensional MOF/MOF derivative arrays on nickel foam as efficient bifunctional coupled oxygen electrodes

Oxygen electrocatalysis,exemplified by the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is central to energy storage and conversion technologies such as fuel cells,metal-air batteries,and water electrolysis.However,highly effective and inexpensive earth-abundant materials are sought after to replace the noble metal-based electrocatalysts currently in use.Recently,metal-organic frameworks(MOFs)and carbon-based MOF derivatives have attracted considerable attention as efficient catalysts due to their exceedingly tunable morphologies,structures,compositions,and functionalization.Here,we report two-dimensional(2D)MOF/MOF derivative coupled arrays on nickel foam as binder-free bifunctional ORR/OER catalysts with enhanced electrocatalytic activity and stability.Their remarkable electrochemical properties are primarily attributed to fully exposed active sites and facilitated charge-transfer kinetics.The coupled and hierarchical nanosheet arrays produced via our growth-pyrolysis-regrowth strategy offer promise in the development of highly active electrodes for energy-related electrochemical devices.

Highly selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over MIL-101(Cr)-NH_2 supported Pd catalyst at low temperature

An efficient heterogeneous catalyst,Pd@MIL‐101(Cr)‐NH2,is prepared through a direct pathway of anionic exchange followed by hydrogen reduction with amino‐containing MIL‐101as the host matrix.The composite is thermally stable up to350°C and the Pd nanoparticles uniformly disperse on the matal organic framework(MOF)support,which are attributed to the presence of the amino groups in the frameworks of MIL‐101(Cr)‐NH2.The selective hydrogenation of biomass‐based furfural to tetrahydrofurfuryl alcohol is investigated by using this multifunctional catalyst Pd@MIL‐101(Cr)‐NH2in water media.A complete hydrogenation of furfural is achieved at a low temperature of40°C with the selectivity of tetrahydrofurfuryl alcohol close to100%.The amine‐functionalized MOF improves the hydrogen bonding interactions between the intermediate furfuryl alcohol and the support,which is conducive for the further hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol in good coordination with the metal sites.