Effect of heat treatment of Mn-Cu precursors on morphology of dealloyed nanoporous copper

Nanoporous copper with nano-scale pore size was synthesized by dealloying Mn-Cu precursor alloy using a free corrosion method. The effects of heat treatment of Mn-Cu precursors on alloy phase, morphology and composition of the resultant nanoporous copper were investigated. It is revealed that the compositions distribute homogeneously in the bulk Mn-Cu precursors, which consequently results in a more fully dealloying for forming nanoporous copper. The alloy phase changes from Cuo.a9Mno.51 and Cuo.21Mno.79 of non-thermally treated precursor to Cuo.33Mn0.67 of heat treated alloy. The residual Mn content in nanoporous copper is decreased from 12.97% to 2.04% （molar fraction） made from the precursor without and with 95 h heat treatment. The typical pore shape of nanoporous copper prepared by dealloying the precursor without the heat treatment is divided into two different zones： the uniform bi-continuous structure zone and the blurry or no pore structure zone. Nanoporous copper is of a uniform sponge-like morphology made from the heat-treated precursor, and the average ligament diameter is 40 nm, far smaller than that from the non-thermally treated precursor, in which the average ligament diameter is estimated to be about 70 nm.

Self-Supporting Nanoporous Copper Film with High Porosity and Broadband Light Absorption for Efficient Solar Steam Generation

Solar steam generation(SSG)is a potential technology for freshwater production,which is expected to address the global water shortage problem.Some noble metals with good photothermal conversion performance have received wide concerns in SSG,while high cost limits their practical applications for water purification.Herein,a self-supporting nanoporous copper(NP-Cu)film was fabricated by one-step dealloying of a specially designed Al_(98)Cu_(2)precursor with a dilute solid solution structure.In-situ and ex-situ characterizations were performed to reveal the phase and microstructure evolutions during dealloying.The NP-Cu film shows a unique three-dimensional bicontinuous ligament-channel structure with high porosity(94.8%),multi scale-channels and nanoscale ligaments(24.2±4.4nm),leading to its strong broadband absorption over the 200–2500 nm wavelength More importantly,the NP-Cu film exhibits excellent SSG performance with high evaporation rate,superior efficiency and good stability.The strong desalination ability of NP-Cu also manifests its potential applications in seawater desalination.The related mechanism has been rationalized based upon the nanoporous network,localized surface plasmon resonance effect and hydrophilicity.

Dense copper azide synthesized by in-situ reaction of assembled nanoporous copper microspheres and its initiation performance

Copper azide with high density was successfully synthesized by in-situ reaction of nanoporous copper(NPC)precursor with HN_(3) gaseous.NPC with pore size of about 529 nm has been prepared by electroless plating using polystyrene(PS)as templates.The copper shells thickness of NPC was controlled by adjusting the PS loading amount.The effects of copper shell on the morphology,structure and density of copper azide were investigated.The conversion increased from 87.12%to 95.31%when copper shell thickness decrease from 100 to 50 nm.Meanwhile,the density of copper azide prepared by 529 nm NPC for 24 h was up to 2.38 g/cm^(3).The hollow structure of this NPC was filled by swelling of copper azide which guaranteed enough filling volume for keeping the same shape as well as improving the charge density.Moreover,HNS-IV explosive was successfully initiated by copper azide with minimum charge thickness of 0.55 mm,showing that copper azide prepared has excellent initiation performance,which has more advantages in the application of miniaturized explosive systems.

Organic-inorganic Hybrids Towards the Preparation of Nanoporous Composite Thin Films for Microelectronic Application

Silicon containing materials have traditionally been used in microelectronic fabrication. Semiconductor devices often have one or more arrays of patterned interconnect levels that serve to electrically couple the individual circuit elements forming an integrated circuit. These interconnect levels are typically separated by an insulating or dielectric film. Previously, a silicon oxide film was the most commonly used material for such dielectric films having dielectric constants( k ) near 4 0. However, as the feature size is continuously scaling down, the relatively high k of such silicon oxide films became inadequate to provide efficient electrical insulation. As such, there has been an increasing market demand for materials with even lower dielectric constant for Interlayer Dielectric(ILD) applications, yet retaining thermal and mechanical integrity. We wish to report here our investigations on the preparation of ultra low k ILD materials using a sacrificial approach whereby organic groups are burnt out to generate low k porous ORMOSIL films. We have been able to prepare a variety of organically modified silicone resins leading to highly microporous thin films, exhibiting ultra low k from 1 80 to 2 87, and good to high modulus, 1 5 to 5 5 GPa. Structure property influences on porosity, dielectric constant and modulus will be discussed.

Fixation of CO_2 by electrocatalytic reduction to synthesis of dimethyl carbonate in ionic liquid using effective silver-coated nanoporous copper composites

With high surface area,open porosity and high efficiency,a catalyst was prepared and firstly employed in electrocatalytic reduction of CO2 and electrosynthesis of dimethyl carbonate（DMC）.The electrochemical property for electrocatalytic reduction of CO2 in ionic liquid was studied by cyclic voltammogram（CV）.The effects of various reaction variables like temperature,working potential and cathode materials on the electrocatalytic performance were also investigated.80%yield of DMC was obtained under the optimal reaction conditions.

Eutectic-derived synthesis of hierarchically nanoporous copper for electrochemical actuation and solar steam generation

The utilization of nanoporous copper(np-Cu)as a metallic actuator has gained attention in recent years due to its cost-effectiveness in comparison to other precious metals.Despite this,the enhancement of np-Cu’s actuation performance remains a challenge due to limitations in its strain amplitude and actuation rate.Additionally,np-Cu has been deemed as a promising material for solar absorption due to its localized surface plasmon resonance effect.However,practical applications such as solar steam generators(SSGs)utilizing np-Cu have yet to be documented.In this study,we present the development of hierarchically nanoporous copper(HNC)through the dealloying of a eutectic Al-Cu alloy.The hierarchical structure of the HNC features a combination of ordered flat channels and randomly distributed continuous nanopores,which work in synergy to improve actuation performance.The ordered flat channels,with a sub-micron scale,facilitate rapid mass transport of electrolyte ions,while the nano-sized continuous pores,due to their large specific surface area,enhance the induced strain.Our results indicate that the HNC exhibits improved actuation performance,with a two times increase in both strain amplitude and rate in comparison to other reported np-Cu.Additionally,the HNC,for the first time,showcases excellent solar steam generation capabilities,with an evaporation rate of 1.47 kg·m^(-2)·h^(-1) and a photothermal conversion efficiency of 92%under a light intensity of 1 kW·m^(-2),which rivals that of nanoporous gold and silver film.The enhanced actuation performance and newly discovered solar steam generation properties of the HNC are attributed to its hierarchically porous structure.

A chemically stable nanoporous coordination polymer with fixed and free Cu^(2+)ions for boosted C_(2)H_(2)/CO_(2)separation

Safely and highly selective acetylene(C_(2)H_(2))capture is a great challenge,because of its highly explosive nature,as well as its nearly similar molecule size and boiling point toward the main impurity of carbon dioxide(CO_(2)).Adsorption separation has shown a promising future.Herein,a new nanoporous coordination polymer(PCP)adsorbent with fixed and free Cu ions(termed NTU-66-Cu)was prepared through post-synthetic approach via cation exchanging from the pristine NTU-66,an anionic framework with new 3,4,6-c topology and two kinds of cages.The NTU-66-Cu shows significantly improved C_(2)H_(2)/CO_(2)selectivity from 6 to 32(v/v:1/1)or 4 to 4_(2)(v/v:1/4)at low pressure under 298 K,along with enhanced C_(2)H_(2)capacity(from 89.22to 111.53 cm^(3)·g^(-1)).More importantly,this observation was further validated by density functional theory(DFT)calculations and breakthrough experiments under continuous and dynamic conditions.Further,the excellent chemical stability enables this adsorbent to achieve recycle C_(2)H_(2)/CO_(2)separation without loss of C_(2)H_(2)capacity.

Morphologies and corrosion resistances of electroless Ni-P coated nanoporous coppers

In order to improve the corrosion resistance of nanoporous coppers （NPCs）, the electroless Ni-P coated NPCs were prepared in plating solutions with different pH values （5, 8, 11） and complexing agent （actic acid, citric acid）. The morphologies and cor- rosion resistances of the as-prepared samples were investigated. The results showed that the double complexing agent com- posed of lactic acid and citric acid is relatively suitable for preparing the Ni-P coated NPC with three-dimensional continuous interpenetrating ligament-channel structures, and the uniform ligaments and nanoporous channels could be obtained at pH8. The Ni-P coated NPC showed higher corrosion potentials than NPC in H2S04, NaOH and NaC1 corrosion solutions.

Relationship between dealloying conditions and coarsening behaviors of nanoporous copper fabricated by dealloying Cu-Ce metallic glasses

Monolithic nanoporous copper （NPC） with tunable ligament size （107-438 nm） was synthesized by dealloying a new Cu-Ce binary glassy precursor in dilute H2 SO4 aqueous solution. The effects of the dealloying conditions on the morphologies of NPC were evaluated comprehensively. The results show that the ligaments of NPC can significantly coarsen with the increase of acid concentration, elevation of reaction temperature or prolongation of immersion time. These coarsening behaviors can be well described by a diffusion based growth kinetic model. Moreover, the surface diffusivity and activation energy for diffu- sion of Cu atoms were also estimated to investigate the formation mechanism of NPC, which is mainly governed by dissolution of Ce element in the glassy precursor coupled with nucleation and growth of Cu clusters via the precursor/solution interface. In the experiment of the degradation of methyl orange （MO） dye, the NPC fabricated by Cu-Ce metallic glasses exhibits superior sono-catalytic activity.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Influence of cooling rate and addition of lanthanum and cerium on formation of nanoporous copper by chemical dealloying of Cu_(15)Al_(85) alloy

The influence of cooling rate and addition of La and Ce on the formation of nanoporous copper by chemical dealloying of Cu15Al85 alloy was studied. The components and microstructures of nanoporous copper were characterized by utilizing X-ray diffrac-tion, field emission scanning electron microscopy and energy dispersive X-ray analysis. N2 adsorption/desorption experiments were used to evaluate specific surface areas of samples. The results showed that, with the increase of cooling rate, phase composition of precursor alloy almost had no change, the ligament size of nanoporous copper had a decrease trend, and specific surface area in-creased gradually. And it was found that the specific surface area of the nanoporous copper obtained by Cu15Al85 alloy containing La and Ce was 63.258 m2/g, which was more than 11.739 m2/g compared with the nanoporous copper dealloying by Cu15Al85 alloy without La and Ce under the same conditions.

Fabrication and Dealloying Behavior of Monolithic Nanoporous Copper Ribbons with Bimodal Channel Size Distributions

Monolithic nanoporous copper （NPC） ribbons with bimodal channel size distributions can be fabricated through chemical dealloying of Mg-32 Cu alloy in an acidic solution at room temperature. The microstructure of the as- dealloyed samples was characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray analysis. These NPC ribbons are composed of interconnected large-sized channels （hundreds of nm） with highly porous channel walls （tens of nm）. Both large- and small-sized channels are open, bicontinuous, and interpenetrating. Additionally, it is the first time to find that the evolution process of porous structure along the thickness direction of samples during the dealloying is from the interior to exterior, which is just contrary to the coarsening process along the thickness direction during the post-dealloying. Meanwhile, the corresponding mechanism is discussed in detail.

Scaling laws and mechanical properties of nanoporous copper

Through molecular dynamics simulations,the mechanical behavior of nanoporous copper under impact loading was investigated with relative densities ranging from 77.91% to 98.36%,focusing on deformation mechanism,the scaling laws and influence of ligament sizes.Results show that the classical Gibson-Ashby′s scaling laws should be modified for prediction of both the Young′s modulus and yield stress.A proportional relationship is established between cell wall thickness and yield stress,and new modified scaling equations are built for nanoporous copper with consideration on both relative mass density and size effects of ligaments.The size effect can be explained by larger surface area/volume ratio of samples with thinner ligament size and limited dislocation source activation due to narrow space between larger numbers of voids.

Monitoring the surface evolution of a nanoporous core-shell electrocatalyst for oxygen reduction reaction

Subject Code:E01With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Profs.Ding Yi(丁轶)and Luo Jun(罗俊)from the School of Materials Science and Engineering,Tianjin University of Technology and Prof.Liu Limin(刘利民)from Beijing

Enhanced visible-light photocatalytic degradation and disinfection performance of oxidized nanoporous g-C3N4 via decoration with graphene oxide quantum dots

Oxidized nanoporous g-C3N4(PCNO)decorated with graphene oxide quantum dots(ox-GQDs)was successfully prepared by a facile self-assembly method.As co-catalysts,the ultrasmall zero-dimensional(0 D)ox-GQDs can achieve uniform dispersion on the surface/inner channels of PCNO,as well as intimate contact with PCNO through hydrogen bonding,π-π,and chemical bonding interactions.In contrast with PCNO,the ox-GQDs/PCNO composite photocatalysts possessed improved light-harvesting ability,higher charge-transfer efficiency,enhanced photooxidation capacity,and increased amounts of reactive species due to the upconversion properties,strong electron capturing ability,and peroxidase-like activity of the ox-GQDs.Therefore,the visible-light photocatalytic degradation and disinfection performances of the ox-GQDs/PCNO composite were significantly enhanced.Remarkably,the composite with a 0.2 wt.% deposited amount of ox-GQDs(ox-GQDs-0.2%/PCNO)exhibited optimum amaranth photodegradation activity,with a corresponding rate about 3.1 times as high as that of PCNO.In addition,ox-GQDs-0.2%/PCNO could inactivate about 99.6%of Escherichia coli(E.coli)cells after 4 h of visible light irradiation,whereas only^31.9% of E.coli cells were killed by PCNO.Furthermore,h+,·O2-,and·OH were determined to be the reactive species generated in the photocatalytic process of the ox-GQDs/PCNO system;these species can thoroughly mineralize azo dyes and effectively inactivate pathogenic bacteria.

Highly efficient nanoporous CoBP electrocatalyst for hydrogen evolution reaction

Water splitting is an environment friendly and efficient way to produce hydrogen.Highly efficient and low-cost non-noble metal catalysts play an important role in hydrogen evolution reaction(HER).Dealloying is a simple method to prepare three-dimensional self-supporting nanoporous materials without conductive supports and binders.In this work,we prepared self-supporting nanoporous CoBP electrocatalyst by dealloying method.The influence of the synergistic effect of nonmetallic elements on catalytic activity was investigated.The synergistic electronic effect of Co,B and P atoms on the surface optimizes the H atoms desorption and results in superior HER activity.The bi-continuous structure of nanoporous CoBP provides more active area and favors of electron and electrolyte transfer.The nanoporous CoBP with the B/P atomic ratio of 1/3 exhibits low overpotential of 42 mV at 10 mA·cm^(-2),small Tafel slope of 39.8 mV·dec-1 and good long-term stability with no performance decrease for 20 h in alkaline solution.

Microstructure Control of Nanoporous Silica Thin Film Prepared by Sol-gel Process

Nanoporous silica films were prepared by sol-gel process with base, acid and base/acid two-step catalysis.Transmission electron microscope （TEM） and particle size analyzer were used to characterize the microstructure and the particle size distribution of the sols. Scanning electron microscopy （SEM）, atomic force microscopy （AFM） and spectroscopic ellipsometer were used to characterize the surface microstructure and the optical properties of the silica films. Stability of the sols during long-term storage was investigated. Moreover,the dispersion relation of the optical constants of the silica films, and the control of the microstructure and properties of the films by changing the catalysis conditions during sol-gel process were also discussed.

Weaving 3D highly conductive hierarchically interconnected nanoporous web by threading MOF crystals onto multi walled carbon nanotubes for high performance Li-Se battery

Lithium-selenium(Li-Se)battery has attracted growing attention.Nevertheless,its practical application is still impeded by the shuttle effect of the formed polyselenides.Herein,we report in-situ hydrothermal weaving the three-dimensional(3 D)highly conductive hierarchically interconnected nanoporous web by threading microporous metal organic framework MIL-68(Al)crystals onto multi-walled carbon nanotubes(MWCNTs).Such 3 D hierarchically nanoporous web(3 D MIL-68(Al)@MWCNTs web)with a very high surface area,a large amount of micropores,electrical conductivity and elasticity strongly traps the soluble polyselenides during the electrochemical reaction and significantly facilitates lithium ion diffusion and electron transportation.Molecular dynamic calculation confirmed the strong affinity of MIL-68(Al)for the adsorption of polyselenides,quite suitable for Li-Se battery.Their hexahedral channels(1.56 nm)are more efficient for the confinement of polyselenides and for the diffusion of electrolytes compared to their smaller triangular channels(0.63 nm).All these excellent characteristics of 3 D MIL-68(Al)@MWCNTs web with suitable confinement of a large amount of selenium and the conductive linkage between MIL-68(Al)host by MWCNTs result in a high capacity of 453 m Ah/g at 0.2 C with 99.5%coulombic efficiency after 200 cycles with significantly improved cycle stability and rate performance.The 3 D MIL-68(Al)@MWCNTs web presents a good performance in Li-Se battery in term of the specific capacity and cycling stability and also in terms of rate performance compared with all the metal-organic framework(MOF)based or MOF derived porous carbons used in Li-Se battery.

Facile synthesis of 3D nanoporous Pd/Co_2O_3 composites with enhanced catalytic performance for methanol oxidation

To simultaneously reduce noble metal Pd usage and enhance electrocatalytic performance for methanol oxidation,Pd/Co2O3 composites with ultrafine three-dimensional(3D)nanoporous structures were designed and synthesized by simple one-step dealloying of a melt-spun Al-Pd-Co alloy with an alkaline solution.Their electrocatalytic activity in alkaline media was determined by a Versa-STAT MC workstation.The results indicate that the typical sizes of the ligaments and pores of the composites were approximately 8-9 nm.The Co2O3 was uniformly distributed on the Pd ligament surface.Among the as-prepared samples,the nanoporous Pd/Co2O3 composite generated from dealloying of the Al84.5Pd15Co0.5 alloy had the best electrocatalytic activity,and its activity was enhanced by approximately 230%compared with the nanoporous Pd from dealloying of Al85Pd15.The improvement of the electrocatalytic performance was mainly attributed to the electronic modification effect between Pd and Co as well as the bifunctional mechanism between Pd and Co2O3.

Liquid metal assisted regulation of macro-/micro-structures and mechanical properties of nanoporous copper

Nanoporous metals have received significant attention as a new class of structural and functional materials.However,the macroscopic brittle fracture under the tensile test is an impediment to their practical applications.Thus,it is of central importance to develop nanoporous materials with low cost and high tensile ductility.Herein,a nanoporous Cu film supported on a pure Cu substrate(NPC@Cu)was fabricated by utilizing a liquid Ga assisted alloying-dealloying strategy,and the thickness of NPC film can be precisely regulated by changing the mass loading of liquid Ga.In-situ X-ray diffraction was performed to further explore the alloying/dealloying mechanisms.The NPC@Cu films show good tensile mechanical properties with a minimum elongation of 13.5%,which can be attributed to the good interface bonding and certain modulus matching between the nanoporous Cu layer and the Cu substrate.Our findings demonstrate that the design of film-substrate structure provides a feasible strategy for enhancing the mechanical properties of nanoporous metals.

MULTIAXIAL BEHAVIOR OF NANOPOROUS SINGLE CRYSTAL COPPER:A MOLECULAR DYNAMICS STUDY

The stress-strain behavior and copper are studied by the molecular dynamics incipient yield surface of nanoporous single crystal （MD） method. The problem is modeled by a periodic unit cell subject to multi-axial loading. The loading induced defect evolution is explored. The incipient yield surfaces are found to be tension-compression asymmetric. For a given void volume fraction, apparent size effects in the yield surface are predicted： the smaller behaves stronger. The evolution pattern of defects （i.e., dislocation and stacking faults） is insensitive to the model size and void volume fraction. However, it is loading path dependent. Squared prismatic dislocation loops dominate the incipient yielding under hydrostatic tension while stacking-faults are the primary defects for hydrostatic compression and uniaxial tension/compression.