Internal Cavity Structure Research Articles

Micro/Meso‐Porous Double‐Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc‐Ion Capacitor

AbstractEnergy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g−1 in supercapacitor and specific capacitance of 260 F g−1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Micro/Meso-Porous Double-Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc-Ion Capacitor.

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g-1 in supercapacitor and specific capacitance of 260 F g-1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Hierarchical porous spindle-shaped MIL-88B@Fe2O3 with core-shelled structure for conductometric trimethylamine detection

Hierarchical porous spindle-shaped MIL-88B (HPS-MIL-88B) with core-shelled structure was prepared by citric acid-assisted. The material exhibits open channels on its outer surface and a hierarchical internal cavity structure with meso-/macro-pores. The samples were then pretreated at 200 °C to form an oxide film, aiming to improve the conductivity of material. The as-prepared HPS-MIL-88B-6 h@Fe2O3 material with core-shelled structure exhibits superior selectivity and high sensitivity to trimethylamine (TMA) at 200 °C (detection limit as low as 1 ppm) with fast response and excellent repeatability. The outstanding sensing performance was owing to the open and hierarchical porous that enhances the reaction between the target gas and the active sites of the material. In addition, the metal unsaturated active sites of MIL-88B (Lewis’s acid) can selectively undergo acid-base reactions with TMA (Lewis’s base), enhancing the generation of oxygen species and improving the selective adsorption capacity towards the target gas. This work provides a new path route for the application of MOF materials in sensors.

Impact of Cations and Framework on Trapdoor Behavior: A Study of Dynamic and In Situ Gas Analysis.

Due to their distinct and tailorable internal cavity structures, zeolites serve as promising materials for efficient and specific gas separations such as the separation of /CO2 from N2. A subset of zeolite materials exhibits trapdoor behavior which can be exploited for particularly challenging separations, such as the separation of hydrogen, deuterium, and tritium for the nuclear industry. This study systematically delves into the influence of the chabazite (CHA) and merlinoite (MER) zeolite frameworks combined with different door-keeping cations (K+, Rb+, and Cs+) on the trapdoor separation behavior under a variety of thermal and gas conditions. Both CHA and MER frameworks were synthesized from the same parent Y-zeolite and studied using in situ X-ray diffraction as a function of increasing temperatures under 1 bar H2 exposures. This resulted in distinct thermal responses, with merlinoite zeolites exhibiting expansion and chabazite zeolites showing contraction of the crystal structure. Simultaneous thermal analysis (STA) and gas sorption techniques further demonstrated how the size of trapdoor cations restricts access to the internal porosities of the zeolite frameworks. These findings highlight that both the zeolite frameworks and the associated trapdoor cations dictate the thermal response and gas sorption behavior. Frameworks determine the crystalline geometry, the maximum porosities, and displacement of the cation in gas sorption, while associated cations directly affect the blockage of the functional sites and the thermal behavior of the frameworks. This work contributes new insights into the efficient design of zeolites for gas separation applications and highlights the significant role of the trapdoor mechanism.

Manufacturing errors detection and visualization system for parts with complex internal cavity structural through industrial CT image

To address the challenge of detection and visualization manufacturing errors in part with complex internal cavity structures, this paper present a method based on industrial computed tomography (CT) image. First, a two-dimensional (2D) CT sequence slice images are obtained using fan-beam high energy industrial CT scanning, which is then reconstructed into a three-dimensional (3D) measurement model. The measurement 3D model is registered with the original design model, and the surface information of the part is obtained by segmenting the surfaces. The error between reference surface of original design model and test surface of measurement model is calculated. By comparing the error value with the tolerance, the detection result is obtained and analyzed. The developed software system enables areas that do not meet the tolerance requirements to be visualized. This method can detect manufacturing errors for part with complex internal cavity structures, such as planeness error, cylindricity error, verticality error, and parallelism error. This method provides a basis for assessing the manufacturing and processing quality of part with complex internal cavity structures.

Investigation of the effect of the degree of hollowness and internal cavity structure on the mechanical properties of 3D-printed parts

Despite the wide growth of additive manufacturing, it is still very expensive to mass produce 3D-printed parts. The costs can be minimized if the quantity of material required to produce a part can be substantially reduced by introducing hollow cavities into the structure, without compromising its properties. This study investigates the effect of the degree of hollowness and different internal cavity structures on the mechanical properties of 3D-printed materials. Test specimens were prepared with four polymeric materials (i.e., acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), carbon fiber-reinforced (CFR) ABS, and CFR PLA) using the fused deposition modeling 3D printing technique. Internal hollow cavities were introduced to the specimens during printing and the specimens were prepared with three different cavity structures (i.e., hexagonal honeycomb, circular drills, and squares), and the degree of hollowness was varied from 0% to 30% in 10% increments. Tensile and flexural properties of the 3D-printed specimens were evaluated and analyzed. The mechanical properties of all specimens were found to decrease with increasing hollowness levels, regardless of the type of material or the internal cavity structure. The hexagonal honeycomb structure showed the best tensile properties out of the three internal cavity structures, while the flexural properties were not significantly affected by the internal cavity structure. The material type had a significant impact on the mechanical properties with PLA exhibiting better tensile and flexural properties than ABS, while their carbon fire reinforced counterparts showed enhanced mechanical properties than pure ABS and PLA.

Allowance Extraction Considering of Inner and Outer Contour and Experimental Research on Belt Grinding of Hollow Blade

Aero-engine fan blades often use a cavity structure to improve the thrust-to-weight ratio of the aircraft. However, the use of the cavity structure brings a series of difficulties to the manufacturing and processing of the blades. Due to the limitation of blade manufacturing technology, it is difficult for the internal cavity structure to achieve the designed contour shape, so the blade has uneven wall thickness and poor consistency, which affects the fatigue performance and airflow dynamic performance of the blade. In order to reduce the influence of uneven wall thickness, this paper proposes a grinding allowance extraction method considering the double dimension constraints (DDC) of the inner and outer contours of the hollow blade. Constrain the two dimensions of the inner and outer contours of the hollow blade. On the premise of satisfying the outer contour constraints, the machining model of the blade is modified according to the distribution of the inwall contour to obtain a more reasonable distribution of the grinding allowance. On the premise of satisfying the contour constraints, according to the distribution of the inwall contour, the machining model of the blade is modified to obtain a more reasonable distribution of the grinding allowance. Through the grinding experiment of the hollow blade, the surface roughness is below Ra0.4 μm, and the contour accuracy is between − 0.05~0.14 mm, which meets the processing requirements. Compared with the allowance extraction method that only considers the contour, the problem of poor wall thickness consistency can be effectively improved. It can be used to extract the allowance of aero-engine blades with hollow features, which lays a foundation for the study of hollow blade grinding methods with high service performance.

Non-mechanical optical beam-steering of a liquid crystal laser

In this paper, we demonstrate dynamic optical beam-steering of a band-edge chiral nematic liquid crystal (LC) laser that does not involve any change in the configuration of the helical structure. This beam-steering is achieved by exploiting the circular polarisation of the LC laser in combination with tuneable nematic LC phase shifters and fixed polarisation gratings. Experimental results are presented, showing the optical steering of the LC laser emission to four separate discrete spatial positions and, using simulations based on Jones calculus, we explain the appearance and relative intensities of other minor spots that appear around the primary beam. Compared with other approaches of beam-steering an LC laser, this method does not result in an alteration of the laser wavelength, does not change the internal cavity structure of the laser, and has a minimal impact on the intensity of the laser emission. In addition, the whole system (except for the solid-state pump source) is comprised of thin films that are either liquid crystalline or polymers, which provides a tangible route towards a more compact and integrated optically steerable LC laser.

Experimental investigation of dynamic mechanical properties of foamed magnesium oxysulfate cementitious material

With the rapid reutilization of solid waste materials, it is imperative to investigate the properties of composite materials formed by the addition of solid waste materials. Basic foamed magnesium oxysulfate cementitious material(FMOCM) with and without solid waste materials were studied and compared. This study focused on the internal structures and quasi-static and dynamic mechanical properties of FMOCM. The results showed that the internal cavity structure of the FMOCM underwent significant changes, and the pore sizes became smaller owing to the addition of recycled materials and wood flour, which greatly improved the quasi-static strength of the FMOCM. It was found that the FMOCM had obvious strain rate effects. By comparing the dynamic strength factors, the dynamic strength of the regular FMOCM almost doubled, and the addition of solid waste materials weakened the strain rate effect. Only when the strain rate was lower did the FMOCM with solid waste materials show better toughness compared to the more serious fracture of the regular FMOCM. Furthermore, this study demonstrated the broad application prospects of solid waste materials in magnesium oxysulfide cementitious materials.

Fabrication and properties of silica-based ceramic cores modified by mullite powders with different particle sizes

Ceramic cores provide complex internal cavity structures in the investment precision castings of hollow blades for aero-engine. The silica/mullite ceramic cores were fabricated by hot injection molding, adding fused mullite powders with different particle sizes as mineralizers. The particle size of mullite mineralizers on the crystallization and properties of ceramic cores was investigated in the paper. The result shows that the mullite mineralizers promote the crystallization of cristobalite in ceramic cores, and finer mullite powders can further improve the heterogeneous nucleation, and generate larger quantities of cristobalite. Mullite mineralizers with large particle size can lead to low sintering degree, poor mechanical properties and creep resistance of ceramic cores. While the particle size of mullite mineralizers is too small, the core contains too much quartzite crystal phase, and the microcrack occurs during the phase transformation during cooling, which also causes the deterioration of the strength at room temperature and the high temperature deformation resistance ability. The ceramic cores with mullite powders in particle size of 19 μm show excellent comprehensive performance, with linear shrinkage of 0.65%, porosity of 31.8%, room temperature strength of 17.8 MPa, high temperature creep deformation of 0.4 mm, and leaching rate of 0.06 g/min.

Formation of nanomaterial internal cavity based on process similar to bread-baking

Since 1990s, the design and control of morphology for nanomaterials has been attracting great attention. Nanomaterials with internal cavity structure are promising for their great properties related to catalysis, purification, drug delivery, electronic materials, energy storage and so on. Herein a method to fabricate WO3 nanosheets with internal cavity was reported. Being quite different from those methods reported before, e.g. using template or Kirkendall effect, this process verified a novel hollow structure forming method similar to bread-baking, including generation of dense shell on the interface and internal steam expansion. SEM observation was used by changing accelerating voltage in situ to confirm the smooth surface and porous interior of WO3 nanosheets. Besides, the BET, TEM and SAXS measurements revealed the hollow structure of as-fabricated samples.

Green preparation of thermal and solvent resistant poly (tetrafluoroethylene‐co‐perfluoropropylvinyl ether) hollow fiber membrane for organic solvent recycling

AbstractSo far, the organic solvent recycling still has great challenges. Herein, the thermal and solvent resistant poly (tetrafluoroethylene‐co‐perfluoropropylvinyl ether) (PFA) hollow fiber membranes (TS‐PFA HFMs) were continuously designed by on‐line compound technique for organic solvent recycling. The experiment results indicated that the increased sintering temperature brought about the porous surface and loose internal cavity structures. Importantly, the membrane exhibited the excellent thermal resistance at 70°C working condition. Furthermore, part of the poly (vinyl alcohol) was retained in the membrane which was competent to create synergistic effects, and endowed the membrane with not only favorable elasticity but also remarkable hot water resistance. Finally, the excellent organic solvent recycling ability of the membrane was demonstrated in simulated non‐aqueous solvent dyeing system. Specifically, no organic solvents or other hazardous substances were used during the fabrication process, which can realize the green preparation of the membrane.

Hollow Nanorods and Amorphous Co9S8 Quantum Dots Construct S-Scheme Heterojunction for Efficient Hydrogen Evolution

The hollow materials have stronger absorption capacity for visible light than other materials due to their special internal cavity structure. In this paper, NiTiO3 hollow nanorods and Co9S8 QDs were used to prepare composite materials with strong light absorption capacity and photocatalytic hydrogen production activity using an in situ growth method. The results of UV diffuse reflectance spectra prove that the existence of NiTiO3 hollow nanorod effectively improves the visible light absorption capacity of the composite material. Additionally, the existence of hollow nanorods can evenly disperse Co9S8 QDs on the surface and increase the number of active sites. X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electrochemical measurements further attest that the S-scheme heterojunction constructed between the two semiconductors not only provides a special transmission path for carrier transfer but also retains more useful electrons and holes that participate in the hydrogen evolution reaction. Therefore, the maximum hydrogen production of NiTiO3@Co9S8 QDs can reach 5.38 times that of pure Co9S8 QDs. The consequences show that the S-scheme heterojunction constructed by NiTiO3 has certain development potential in the field of photocatalysis.

Magnetic Field Analysis of Polishing Tools in Permanent Magnetic Field Polishing Device

In order to achieve the polishing of the inner wall of the workpiece with a complex internal cavity structure. In this paper, a planar polishing machine is used as an example to design a polishing device platform. The permanent magnet is used as a magnetic field to drive the polishing tool to polish the inner surface of the workpiece. In this paper, a magnetic field internal polishing analysis method is proposed, which mainly uses the matlab to qualitatively analyze the magnetic force and magnetic moment of the polishing tool, and then qualitatively analyze its motion stability.

Gas-liquid two-phase flow of liquid film breaking process under shock wave

The gas-liquid two-phase flow of liquid dispersing and breaking under the action of shock wave includes complex physical phenomena, such as turbulent mixing of gas-liquid two-phase, instability and breakage of liquid interface, and formation of internal cavity structure after atomization. In order to investigate the shock-wave-caused breaking process of the liquid film, a three-dimensional numerical simulation of the gas-liquid two-phase flow process is performed by using the computational fluid dynamics method. In the simulation, the Mach number of shock wave is 1.5 and the thickness of liquid film is 2 mm. The finite volume method is used to solve the three-dimensional Navier-Stokes equation. The volume of fluid model is applied to the gas-liquid two-phase flow. The <i>k-ε</i> double equation turbulence model is selected for the turbulence calculation. The evolution process of the wave system structure of the shock wave and the deformation, breakage and atomization characteristics of the liquid film are obtained, and compared with the experimental results. The results show that the incidence, reflection, and transmission phenomena occur during the interaction between the shock wave and the liquid film, and the intensity of the transmitted shock wave and the liquid surface tension have an important effect on the breaking process of the liquid film. The transmitted shock wave affects the shape of the broken cloud cluster on the left of the liquid film, while the incident shock wave and reflected shock wave affect the shape of the broken cloud cluster on the right side of the liquid film. The volume of the atomized cloud formed in the breaking process of the liquid film increases rapidly, first reaching 6.7 dm<sup>3</sup> within 2.5 ms, then keeping stable basically. After the shock wave exits from the tube, a long narrow jet is formed. The maximum velocity reaches 519 m/s and appears in the interior of the jet, and then decreases continuously. Under the action of the jet, an expanding three-dimensional cavity structure is formed inside the atomizing cloud, and an annular vortex with negative pressure in the core area occurs in the cavity structure. Finally, the annular vortex continuously entrains the surrounding fluid in the process of forward movement, the strength of the vortex decreases and gradually dissipates in the space. This work is conducive to further understanding the interaction process of gas-liquid two-phase flow.

Innovative Design and Additive Manufacturing of Regenerative Cooling Thermal Protection System Based on the Triply Periodic Minimal Surface Porous Structure

The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling, which are fundamental for the lightweight design and thermal protection of hypersonic vehicles. Triply periodic minimal surface (TPMS) is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics. In this study, test pieces were manufactured using Ti6Al4V lightweight material. We designed three types of porous test pieces, and the interior was filled with a TPMS lattice (Gyroid, Primitive, I-WP) with a porosity of 30%. All porous test pieces were manufactured via selective laser melting technology. A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system. Hence, the relationship between the geometry and mechanical properties of a unit cell is established, and the deformation mechanism of the porous unit cell is clarified. Among the three types of porous test pieces, the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%, the average tensile strength was reduced by 17.7% compared to the solid test piece, while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5% and 33.3%, respectively. Compared with the other two types of unit cells, Gyroid exhibited better mechanical conductivity characteristics. Its deformation process was characterised by stretching, shearing, and twisting, while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation, respectively. The finite element predictions in the study agree well with the experimental results. The results can provide a basis for the design of regenerative cooling thermal protection system.

Redox-responsive tetraphenylethylene-buried crosslinked vesicles for enhanced drug loading and efficient drug delivery monitoring.

Liposomes have been applied extensively as nanocarriers in the clinic (e.g., to deliver anticancer drugs) due to their biocompatibility and internal cavity structures. However, their low drug-loading capacity (DLC; <10%) and uncontrolled release reduce their efficacy in cancer treatment. To improve the DLC and monitor release of drugs in cells in real-time, stimuli-responsive vesicles must be developed. We present various amphiphilic tetraphenylethylene (TPE)-containing compounds designed to self-assemble into liposome-like vesicles that can load both hydrophilic and hydrophobic drugs. The highest DLC for doxorubicin (DOX) was ≤26% for vesicles (diameter = 105 nm) that could encapsulate hydrophilic DOX in the interior water pool and hydrophobic DOX viaπ-π stacking interactions between DOX and the TPE moiety. The stable vesicles could respond rapidly to overexpressed glutathione in the tumor microenvironment to release loaded DOX for cancer therapy. Vesicles modified by active targeting groups showed more efficacious tumor treatment compared with unmodified vesicles and free DOX in vitro and in vivo. Simultaneously we observed, spatiotemporally, the subcellular location of the delivery system and release process of DOX. Our work provides a novel nano-engineering technology to integrate the desired properties for anticancer theranostics: high DLC, stability, stimuli-responsiveness to the cancer environment, drug-delivery monitoring, active targeting, and suppression of tumor growth. These novel vesicles could be employed as multifunctional drug-delivery systems for cancer therapy.

Comparison of Numerical Methods for Fluid-Structure Interaction Simulation of Fused Deposition Modeled Nylon Components

Abstract A comparison is made between three different methods for fluid structure interaction (FSI) simulation of fused deposition modeled (FDM) nylon components having arbitrary internal cavity structures. The FSI methods studied include a simple fluid cavity (FC) model, a coupled Eulerian-Lagrangian (CEL) method, and a smoothed particle hydrodynamics (SPH) method. Model valuations are based on comparing the predicted macro compressive strengths for the simulated FDM builds with experimentally determined compressive yield strengths on actual FDM builds. Each simulation includes two Phases, where the first models the FDM build to compute thermal distortion and residual stresses. The second Phase applies the temperature distribution and state of stress from the first Phase as initial conditions, then includes an FSI simulation wherein the part undergoes quasi-static compression. It is found that the CEL and SPH methods demonstrate higher accuracy than FC, producing less than 2.5% and 1.06% errors, respectively, compared to the experiments. Considering computational demands, the results suggest SPH to be the most suitable method to capture the FSI effects. A case study illustrating generality of the approaches to a different FDM geometry is also included.

Numerical simulation analysis of multi-physical coupling field with abrasive flow precision polishing variable-aperture tube

In the fields of aerospace, precision machinery and energy, there are variable-diameter tubes for many key components. Abrasive flow polishing technology is an effective precision polishing technology for finishing the workpiece with an internal cavity structure. This technology can improve the quality of part finishing, reduce stress concentration, and reduce the surface roughness of the workpiece, and ultimately can improve the performance of the workpiece. In this paper, variable-aperture tube is taken as the research object, and the characteristics of abrasive flow in the multi-physics coupling field are studied by numerical simulation, and the collision removal effect between the abrasive particle and the wall surface is analyzed. We also discussed the control law of the abrasive grain flow processing quality and provided theoretical guidance for abrasive grain flow polishing of this type of part.

Complex Geometry Effects on Cavity Resonance

The flow over an aircraft bay is often represented using a rectangular cavity; however, this simplification neglects many features of actual flight geometry that could affect the unsteady pressure field and resulting loading in the bay. To address this shortcoming, a complex cavity geometry was developed to incorporate more realistic aircraft-bay features including shaped inlets, internal cavity structure, and doors. A parametric study of these features was conducted based on fluctuating pressure measurements at subsonic and supersonic Mach numbers. Resonance frequencies and amplitudes increased in the complex geometry compared to a simple rectangular cavity that could produce severe loading conditions for store carriage. High-frequency content and dominant frequencies were generated by features that constricted the flow such as leading-edge overhangs, internal cavity variations, and the presence of closed doors. Broadband frequency components measured at the aft wall of the complex cavities were also significantly higher than in the rectangular geometry. These changes highlight the need to consider complex geometric effects when predicting the flight loading of aircraft bays.