Nanoscale Pore Structure Research Articles

Micro/nano dual-scale porous surface structure of the Al alloys and improvement on the joint strength with carbon fiber reinforced PA 6 thermoplastic

Improving the interfacial bonding strength of the Al/CFRTP hybrid composites is beneficial for its application in lightweight automotive technology. This study fabricated the micro/nano dual-scale porous surface structures of the Al alloy by the low-cost and effective oxalic acid anodizing to improve the interlocking interface structure. The effects of current density and oxidation time of the anodic oxidation on the shear strength of the Al/PA 6 CFRTP hybrid composite joints were investigated. The results showed that with the increase of the oxidation current density and time, the nanopore diameter, porosity, wettability, and oxide film thickness were significantly improved. The shear strength of the Al/CFRTP PA 6 joints was as high as 23.7 MPa. The micro-scale pits (average size 6 μm) produced by the NaOH treatment and the nano-scale porous structure (16–106 nm) induced by anodizing enhanced the adhesion area and anchoring effect between the Al alloy and PA 6 resin. Thus, the synergistic improvement in the interfacial bonding strength was exhibited.

Tailoring Anti-Impact Properties of Ultra-High Performance Concrete by Incorporating Functionalized Carbon Nanotubes

Replacing micro-reinforcing fibers with carbon nanotubes (CNTs) is beneficial for improving the impact properties of ultra-high performance concrete (UHPC); however, the weak wettability and dispersibility of CNTs and the weakly bonded interface between CNTs and UHPC limit their effectiveness as composites. Therefore, this study aims to enhance the reinforcement effect of CNTs on the impact properties of UHPC via functionalization. Unlike ordinary CNTs, functionalized CNTs with carboxyl or hydroxyl groups can break the Si–O–Ca–O–Si coordination bond in the C–S–H gel and form a new network in the UHPC matrix, effectively inhibiting the dislocation slip inside UHPC matrix. Furthermore, functionalized CNTs, particularly carboxyl-functionalized CNTs, control the crystallization process and microscopic morphology of the hydration products, significantly decreasing and even eliminating the width of the aggregate–matrix interface transition zone of the UHPC. Moreover, the functionalized CNTs further decrease the attraction of the negatively charged silicate tetrahedron to Ca 2+ in the C–S–H gel, while modifying the pore structure (particularly the nanoscale pore structure) of UHPC, leading to the expansion of the intermediate C–S–H layer. The changes in the microstructures of UHPC brought about by the functionalized CNTs significantly enhance its dynamic compressive strength, peak strain, impact toughness, and impact dissipation energy at strain rates of 200–800 s −1 . Impact performance of UHPC containing a small amount of carboxyl-functionalized CNTs (especially the short ones) is generally better than that of UHPC containing hydroxyl-functionalized and ordinary CNTs; it is even superior to that of UHPC with a high steel fiber content.

Electron-induced secondary electron emission of aluminum alloy processed via the combination of alodine treatment and carbon film deposition

• A porous chromate film is formed on the Al alloy via alodine treatment. • Secondary electron emission (SEE) of Al alloy is suppressed via alodine treatment. • SEE of alodine-treated Al alloy is further suppressed via carbon film deposition. • This SEE suppression is beneficial from the porous structure and sp 2 carbons. Relatively strong electron-induced secondary electron emission (SEE) of ordinary aluminum (Al) alloy limits its applications in high-power microwave devices. In this work, a combination strategy of alodine treatment and amorphous carbon (a-C) film deposition for Al alloy was proposed to achieve a goal of SEE suppression. According to the experimental results, it can be found both alodine treatment and a-C film deposition are advantageous to reducing secondary electron yield (SEY) of Al alloy. Moreover, the combination of these two surface treatments can further suppress the SEE of Al alloy due to the superposition effect of nanoscale porous structure and larger numbers of sp 2 carbon bonds. Compared with those of the untreated one, the SEY peak value, first crossover energy and second crossover energy of the Al alloy processed via the combined surface treatment change from 1.7, 25 eV and 2900 eV to 1.08, 150 eV and 650 eV, respectively.

Ultrafast, Stable Electrochromics Enabled by Hierarchical Assembly of V2O5@C Microrod Network.

Vanadium pentoxide (V2O5) with multicolor transition is widely studied in the electrochromic (EC) field to enrich color species of transition-metal oxides; yet, it always suffers from slow switching speed caused by poor electron conductivity and slow ion diffusion, poor cycling stability induced by large volume change during the EC reaction process. Herein, hierarchical network assembly of V2O5@C microrods is introduced to develop an ultrafast, stable, multicolor EC film. Using a two-step pyrolysis that involves metal-organic framework templates, porous microrods with a well-preserved one-dimensional structure are prepared through the assembly of V2O5@C nanocrystals at nanoscale, providing more active sites for ionic insertion and accessible pathways for electron transport. After spray-coating the V2O5@C microrods on conductive substrates, interconnected networks composed of V2O5@C microrods at microscale ensures the infiltration of electrolyte and provide ion transport channels. In addition, the nanoscale porous structure and coated carbon layer can accommodate volumetric changes during ion insertion/extraction process, ensuring high electrochemical stability. As a result, EC electrode with V2O5@C microrods network performed rapid switching speed (1.1/1.0 s) and stable cycle ability (96% after 2000 cycles). At last, flexible large-scale devices and multicolor digital displays were assembled to demonstrate potential application in next-generation wearable electronics.

Porous macroradical epoxy-based supercapacitors

Intrinsic p -type conductivity was observed in an otherwise aliphatic epoxy backbone through derivatization with stable radicals. The conductive potential of this combined radical-epoxy material was further investigated by prospecting for energy storage systems. This work identifies macroradical epoxy composites with 10% (w/w) conductive carbon as viable devices in supercapacitor application. In cross-linking, the appropriate selection of the diamine spacer has a profound impact on the curing and the resulting conformation of the polymer. The short-chain diamine spacer 1,2-diaminoethane exhibits the best supercapacitor performance yielding a maximum specific capacitance of 195 F g −1 at 1.0 A g −1 . The specific capacitance remains at 99% at 1.0 A g −1 after repeatedly charging and discharging 10,000 times. The observed cycling stability is rare for materials exhibiting pseudocapacitance. This better performance than a reference conventional epoxy composite is attributed to the overall contributions of the electric double layer and pseudocapacitance effect with the effective utilization of the nanoscale porous polymeric structure. Furthermore, the pseudocapacitance is significantly enhanced by using the short-chain diamine spacer due to the closer radical-to-radical interactions and the excellent dispersibility of the added conductive particles. • Macroradical epoxies have promising energy-storage prospects. • Macroradical epoxy composite electrodes are viable supercapacitors. • Superior cycling performance is observed, rare for pseudocapacitors. • Rheology and small-angle x-ray scattering correlate with electrode chemistry. • Magnets used during cross-linking are valuable in distinguishing morphology.

Influences of Clay Mineral and Organic Matter on Nanoscale Pore Structures of the Cretaceous Lacustrine Shales in the Songliao Basin, Northeast China

The Cretaceous lacustrine shales of the Qingshankou Formation (K2qn) from the Songliao Basin are recognized as a potential shale oil reservoir in China. Pore structure of shale within the oil window could be significantly influenced by several factors, including mineral and organic matter (OM) compositions. For a better understanding of the factors controlling the pore structure of these shales, 15 core shales from the K2qn were subjected to low-pressure N2 adsorption measurement for both the initial and solvent extracted samples, and the relationships between shale compositions and pore structure parameters were discussed. The results show that the average specific surface area (SSA) and pore volume (PV) increase from 10.14 m2/g to 29.74 m2/g and from 0.0276 cm3/g to 0.0554 cm3/g respectively after extraction, which suggests that the nanopores in these shales could be significantly occupied by the soluble OM, especially for the pores smaller than 10 nm in size. For the extracted samples, the good positive correlations between the SSA and the illite/smectite (I/S) content indicate that a significant amount of small pores are associated with this mineral, while the overall positive correlations between the PVs with the I/S and OM contents suggest that I/S mineral and organic matter (kerogen) have contributed most to pores lager than 10 nm. It is assessed that OM pores contribute approximately 16% to total PV of these shales. Our results will improve the understanding of pore characterization of the clay- and OM-rich lacustrine shales and provide some implications for shale oil accumulation in the Songliao Basin.

Preparation of nanoscale LaXO3 (X=Co, Mn, Ni) by rheological phase method for oxygen reduction reaction

The rheological phase method(RPM) is a simple and environmentally friendly synthesis method. In this work, nanoscale LaXO3 (X = Co, Mn, Ni) series catalysts have been synthesized by RPM and their oxygen reduction reaction (ORR) have been investigated. The optimal calcination temperature of the RPM is lower than that of the solid-phase method, and the catalytic activity of the catalyst is also higher than that of solid-phase method, mainly because the products prepared by RPM have a nanoscale porous structure and a small amount of residual carbon. By comparing the differences among LaCoO3, LaMnO3, and LaNiO3, the results show that the ORR activity of the catalyst is the strongest when the b-site element is Mn, and the calculated electron transfer number is 3.99, which is close to 4 electrons, indicating that the by-product generation is relatively small, and the kinetic current density reach 6.63 mA cm−2. Both were higher than of LaCoO3 and LaNiO3. This work is expected to provide a new green synthesis method for non-noble metal catalyst perovskite oxygen reduction catalyst of LaCoO3, LaMnO3, and LaNiO3.

Microstructural pattern formation during liquid metal dealloying: Phase-field simulations and theoretical analyses

In recent years, liquid metal dealloying (LMD) has emerged as a promising material processing method to generate micro and nano-scale bicontinuous or porous structures. Most previous studies focused on the experimental characterization of the dealloying process and on the properties of the dealloyed materials, leaving the theoretical study incomplete to fully understand the fundamental mechanisms of LMD. In this paper, we use theoretical models and phase-field simulations to clarify the kinetics and pattern formation during LMD. Our study starts from a theoretical analysis of the 1D dissolution of a binary precursor alloy, which reveals that the 1D dissolution process involves two regimes. In the first regime, due to the low solubility of one of the elements in the melt, it accumulates at the solid-liquid interface, which reduces the dissolution kinetics. In the second regime, the interface kinetics reaches a stationary regime where both elements of the precursor alloy dissolve into the melt. Previous works revealed that in the early dealloying stage, the dealloying front is destabilized by an interfacial spinodal decomposition, which triggers the formation of interconnected ligaments. We extend this line of work by proposing a linear stability analysis able to predict the initial length-scale of the ligaments formed in the initial stage of the dealloying. Combining this analysis with the 1D dissolution model proposed here enables us to better understand the initial conditions (composition of the precursor alloy and the melt) leading to a planar dissolution without interface destabilization. Finally, we report a strong influence of solid-state diffusion on dealloying that was overlooked in previous studies. Although the solid-state diffusivity is four to five orders of magnitude smaller than in the liquid phase, it is found to affect both dissolution kinetics and ligament morphologies.

Laser heating induced spatial homogenization of phase separated Na2O-B2O3-SiO2 glass plate with bearing NiO for heat center and structural probe

Na2O-B2O3-SiO2 glass plate phase separated in spinodal was partially remelted and homogenized by laser heating. As heat generation source, 0.8 mol% NiO was added to absorb continuous-wave laser with λ=1064 nm. After acid leaching, borate phase with NiO was remaining partially in laser irradiated area. Smooth, non-porous surface was found at cross section of laser irradiated area below surface, and nano-scale porous structure was found at non-irradiated area observed by scanning electron microscopy (SEM). X-ray Absorption Fine Structure (XAFS) spectra revealed that Ni2+ in laser irradiated area showed coordination change from 6 coordinated octahedral to 5 coordinated in square pyramid along with apparent color change from green to brown. Similar change was observed in water-quenched specimen from 1000°C. Ni2+ transition gave additional structural information in phase separate / homogeneous glass, which was difficult to be distinguished by spectroscopy which focuses on covalent bonding of glass network.

The Pore Structure of Marine to Continental Transitional Shales in the Permian Shanxi Formation on the East Margin of the Ordos Basin, China

The pore structure is an important factor in determining the storage capacity for shale gas development. Twelve samples were selected from the marine to continental transitional shales in the Shanxi Formations on the eastern margin of the Ordos Basin, and their nanoscale pore structure was investigated by a variety of low-temperature N2 adsorption (LT-N2GA) and low-pressure CO2 adsorption (LP-CO2GA) and high-pressure mercury intrusion (HPMI) experiments. The shale pores are complex and are mainly mesopores, which range mainly from 10 nm to 40 nm and greatly contribute to the pore volume (PV), whereas pores with a diameter less than 0.8 nm greatly contribute to the specific surface area (SSA) of the shale. The pore structure is affected by the TOC content, organic matter maturity, and illite/smectite (I/S) mixed layer content. The total PV increases with the increase in TOC content, organic matter maturity, and I/S mixed layer content. The effects of pores on the occurrence shale gas were determined by high-pressure methane adsorption experiments. The maximum adsorption amount of methane was positively correlated with the SSA of the micropores, indicating that the micropores have a large SSA, which controlled the adsorbed gas content of the shale. The mesopores provide the majority of the PV, which mainly corresponds to the volume of free gas in the shale, and the macropores are mainly micron-sized pores, which can form the main migration channels for shale gas.

Observation of water droplets in microporous layers for polymer electrolyte fuel cells by X-ray computed nano-tomography.

An X-ray computed nano-tomography (nano-CT) system has been established at the BL33XU beamline of SPring-8. The optical system consists of pseudo-Köhler illumination with a sector condenser zone plate, an apodization Fresnel zone plate as the objective lens, and a Zernike phase plate. The imaging detector is a fiber-coupling type X-ray camera. The performance of the X-ray nano-CT system was confirmed by imaging an X-ray test chart. The system was subsequently applied to the observation of a microporous layer for polymer electrolyte fuel cells and a simulated microporous layer including liquid water. The nano-CT system, which can perform a computed tomography measurement in less than 4 min, allowed visualization of a spherical water droplet produced in the microporous layer. In the present study, the shape of water droplets in a nanoscale porous structure is investigated.

Changes in Nanoscale Pore Structures and Mesopore Connectivity as a Result of Artificial Maturation of a Source Rock from the Shanxi Formation, Ordos Basin

Changes in Nanoscale Pore Structures and Mesopore Connectivity as a Result of Artificial Maturation of a Source Rock from the Shanxi Formation, Ordos Basin

Spray-drying construction of nickel/cobalt/molybdenum based nano carbides embedded in porous carbon microspheres for lithium-ion batteries as anodes

In this work, from a practical point of view, a scalable spray-drying strategy is developed to prepare nickel/cobalt/molybdenum-based nano carbides embedded in porous microspherical carbon architectures for LIBs as competitive anodes. The resulted porous Ni1.5Co1.5Mo3C/Mo2[email protected] (NCMC/[email protected]) microspheres exhibit even better lithium storage performance in terms of first Coulombic efficiency, reversible capacities, rate behaviors, and cycling stability than their counterparts including Co3Mo3C/Mo2[email protected] and Ni3Mo3C/Mo2[email protected] MSs, thanks to the involved synergistic contributions from the nanoscale effect, solid-solution feature, porous structure, and abundant hetero-interfaces, which cooperatively guarantee the rapid Li+/electron transport and buffered volume changes over (de)lithiation process. Besides, the NCMC/[email protected] full LIBs demonstrate remarkable electrochemical characteristics with high energy density and cycling stability. More significantly, the methodology here holds great promise for achieving other versatile nano carbides towards advanced LIBs and beyond.

Effects of pure carbonation on pore structure and water permeability of white cement mortars

The effects of carbonation on cement-based materials have drawn much attention because of its profound influences on durability performance of concrete structures. Most accelerated carbonation in lab is conducted at RH 50%–70%, which also dries out cement-based materials. The introduced drying action changes pore structure significantly, making the effects of carbonation obscure. To clarify the effects of pure carbonation, water permeability and related micro-structural characteristics are measured on mature mortars, which have been carbonated at water-saturated state. It is found that after carbonation, the porosity of mortars decreases slightly, with finer overall pore structure and lower characteristic pore size. The water permeability also decreases by roughly 40% on average. Based on the pore size distribution curves obtained through the low-field proton nuclear magnetic resonance technique, water permeability is predicted by the Katz-Thompson and Kozeny-Carman theories with satisfactory accuracy. The decrease of water permeability after carbonation agrees well with the reduced characteristic pore length, which quantitatively verifies the observed refinement of nanoscale pore structure due to pure carbonation.

Molecular simulation on CO2 adsorption in partially water-saturated kaolinite nanopores in relation to carbon geological sequestration

CO2 geological sequestration in depleted gas/oil reservoirs is regarded as a promising strategy to mitigate CO2 emission thanks to the well-developed nanoscale pore structures providing substantial adsorption spaces. Therefore, the fundamental understanding of CO2 adsorption in shale nanopores can provide important insights into geological CO2 sequestration. In this work, we use molecular dynamics (MD) and Grand canonical Monte Carlo (GCMC) simulations to investigate CO2 adsorption in kaolinite nanopores with two different basal surfaces and study moisture effect. In the absence of water, CO2 presents stronger adsorption in gibbsite nanopores than siloxane nanopores. In gibbsite pores, water tends to spread over the surfaces forming thin water films. While CO2 is driven to the middle of the pore, an enrichment of CO2 is observed at the water-CO2 interface. On the other hand, water bridges form in siloxane pores. In siloxane mesopores, the shape of water clusters gradually turns to be spherical ones as pressure increases suggesting a more CO2-wet surface, while the deformation of water clusters in micropores is not obvious due to stronger confinement effects. The CO2 distributions in siloxane mesopores can be divided into six zones. The highest CO2 density appears in the three-phase contact areas, while CO2 has a high tendency to accumulate in two-phase contact areas. In general, the presence of water results in the reduction of CO2 adsorption in both gibbsite and siloxane pores. Overall, water has a more detrimental influence on CO2 adsorption in gibbsite pores than siloxane pores. Our work should provide important insights into CO2 adsorption in kaolinite nanopores and reveal CO2 adsorption mechanisms in the presence of water.

Ultraflexible Photothermal Superhydrophobic Coating with Multifunctional Applications Based on Plasmonic TiN Nanoparticles

AbstractPhotothermal superhydrophobic coatings are essential for a variety of applications including anti‐icing and light‐driven self‐propelled motion. However, achieving a flexible and durable superhydrophobic coating with high photothermal efficiency and long‐term stability is still challenging. Herein, a facile and eco‐friendly approach to realizing a superhydrophobic coating with excellent flexibility is proposed. The coating is obtained by spraying titanium nitride (TiN) nanoparticles embedded in polydimethylsiloxane (PDMS) solution onto various substrates. A tight binding between the substrate and nanoparticles occurs that offers the coating the mechanical robustness to endure bending, twisting, abrasion, and tape peeling. The water repellency is retained even after 500 cycles of bending–twisting tests. Combined with the micro–nanoscale porous structure of the surface and plasmonic property of TiN nanoparticles, the coating shows excellent superhydrophobicity and high photothermal conversion properties. The equilibrium temperature of the coating is as high as 130 °C at room temperature under 1 W cm−2 of 808 nm near‐infrared laser irradiation. Due to its flexible property, the coating can be easily applied to irregular surfaces, which, together with the excellent anticorrosion, anti‐icing, and defrosting performances, makes it a reliable resource for multifunctional applications. This work offers a novel technological approach to flexible devices, wearable electronics, and smart textiles.

Influences of microwave irradiation on pore, fracture and methane adsorption of deep shale

In order to better understand the feasibility of enhancing shale gas recovery by microwave irradiation, the influences of microwave irradiation on the pore, fracture, and methane (CH4) adsorption pertaining to shale gas production of a deep shale were fully addressed. A combination of multiple characterization methods was used, including pyrolysis, X-ray diffraction, back-scattered scanning electron microscope, probe molecule adsorption, steady-state permeability, X-ray computed tomography, and gravimetric method for measuring CH4 adsorption. Results show that microwave irradiation has no obvious impact on micropore but decreases mesoporous surface area, and volume of the shale matrix. It particularly reduces the adsorption pores for accommodating CH4 with the diameter of less than 8 nm. The nanoscale pore structure evolution is mainly associated with alterations in organic matter and inorganic minerals of the deep shale after microwave irradiation. Microwave irradiation induces the decomposition, cracking, shift, stripping and formation of minerals, as well as the formation of organic matter. Furthermore, it significantly increases fractures paralleling to bedding planes of the deep shale due to thermal stress generated within various minerals. These newly formed fractures dramatically increase the porosity and permeability of the deep shale. Finally, microwave irradiation significantly decreases the maximum CH4 adsorption capacity of the deep shale by 16.38%. In summary, this study put forward a novel method for enhancing shale gas production via simultaneously promoting CH4 migration and reforming reservoirs under controlled microwave field.

Nature inspired hierarchical structures in nano-cellular epoxy/graphene-Fe3O4 nanocomposites with ultra-efficient EMI and robust mechanical strength

• Nacre/bone like hierarchical structures in epoxy-based nanocomposites. • Simple compression molding with eco-friendly supercritical CO 2 foaming process to achieve porous layered nanocomposites. • Lightweight nano-cellular (52.6 nm) nanocomposite with 75 wt.% rGO-Fe 3 O 4 loading. • Low density (1.26 g/cm 3 ) and high specific EMI SE >5200 dB/cm 2 /g, with preserved tensile strength of 67 MPa achieved. Hierarchical layered structures, whether in a compact form like nacre or a porous manner like bone, are well known for their combined features of high stiffness, strength, and lightweight, inspiring many man-made materials and structures for high performance applications. The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers, although the fabrication and processing remain a great challenge. In this work, a bio-inspired lightweight nano-cellular epoxy/graphene-Fe 3 O 4 nanocomposite with high nanofiller loading of 75 wt.% was successfully fabricated by combining features from both nacre and bone structures, via a simple compression molding process together with an eco-friendly supercritical CO 2 foaming process to achieve robust mechanical strength and excellent electromagnetic interference (EMI) shielding effectiveness (SE) simultaneously. Highly aligned graphene-Fe 3 O 4 nanoplatelets with well controlled nanoscale porous structures (52.6 nm) enabled both low density (1.26 g/cm 3 ) and high specific EMI SE >5200 dB/cm 2 /g, as well as preserved tensile strength of 67 MPa. This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications, from portable electronics to healthcare devices.

Pore structure characteristics of concrete composites with surface-modified carbon nanotubes

The macroscopic properties of carbon nanotubes (CNTs) modified reactive powder concrete (RPC) composites are closely related to their pore structure characteristics, but the structural nature of PRC composites and the effect of CNTs on their pore structure remain unclear. To comprehensively understand the pore structure of RPC composites with surface-modified CNTs and then control their properties, both the mercury intrusion porosimetry (MIP) and low-field nuclear magnetic resonance (LF-NMR) technologies were used to characterize the pore structure characteristics of RPC composites. Experimental results showed there exist large number of nano-scale pores (mainly interlayer and gel pores) with the radius range of 0.3–20 nm in RPC composites. All types of surface-modified CNTs incorporated in this study reduce the pore content and size of RPC composites, thereby modifying the pore structure of RPC. However, different CNTs present varying effects on the pore (especially nano-scale pore) structure characteristics. Among all surface-modified CNTs, the hydroxyl functionalized and nickel-coated CNTs cause the structural shrinkage of C-S-H gel, while the carboxyl functionalized CNTs induce the transformation of some nano-scale pores inside the gel. The effects of surface-modified CNTs on the pore structure of RPC composites are mainly on the nano- and micrometer scale. CNTs can not only increase the matrix compactness of RPC composites and enhance the network structure of hydration products, but also induce the pore water conversion inside C-S-H layers.

Producing light, strong foam glass under a low sintering temperature with insights from molecular simulations

We prepare a type of foam glass achieving an excellent combination of low sintering temperatures of 800 °C, low bulk densities of 320 kg/m3, and high compressive strengths of 7.02 MPa. We determine the optimal experimental parameters first and comprehensively compare the structure-property relationship of the foam glass products with carbon and CaCO3 as foaming agents. The carbon-agent foam glasses with uniform pore structures exhibit low density and high strength while the CaCO3-agent counterpart with large, connected pores exhibits lower density, lower strength. Next, we investigate the effects of Na2HPO4 as foam stabilizer and find that 10 wt.% of Na2HPO4 can effectively stabilize the foaming effects and enable uniformly distributed pore structures. Finally, the molecular nature is elucidated with molecular dynamics simulations, where we find the nanoscale pore structure may play a key role in differing the mechanical performance. This integrated experimental and computational study demonstrates an efficient way to produce foam glasses of superior properties with theoretical insights.