Sphere Wall Research Articles

APMP Pilot Study on High Transmittance Haze

Abstract This article presents the results of the Asia Pacific Metrology Programme (APMP) pilot comparison on high transmittance haze (TH), specifically TH >40 %. Various methods, including ASTM D1003, ISO 14782, the double beam method, and the double compensation method were employed. The results revealed that ASTM D1003 is still influenced by failure to compensate for sphere throughput, even in high TH artefacts. In contrast, the other methods exhibit good consistency, as expected. This article also analyses the total transmittance (TT) and diffuse transmittance (DT) obtained using the double compensation method, theoretically capable of determining accurate TT, DT, and TH, discussing the possibility of inconsistency in the reflectance between the sphere wall and the white plate affecting the agreement.

Sedimentation of a Charged Soft Sphere within a Charged Spherical Cavity.

The sedimentation of a soft particle composed of an uncharged hard sphere core and a charged porous surface layer inside a concentric charged spherical cavity full of a symmetric electrolyte solution is analyzed in a quasi-steady state. By using a regular perturbation method with small fixed charge densities of the soft sphere and cavity wall, a set of linearized electrokinetic equations relevant to the fluid velocity field, electrical potential profile, and ionic electrochemical potential energy distributions are solved. A closed-form formula for the sedimentation velocity of the soft sphere is obtained as a function of the ratios of core-to-particle radii, particle-to-cavity radii, particle radius-to-Debye screening length, and particle radius-to-porous layer permeation length. The existence of the surface charge on the cavity wall increases the settling velocity of the charged soft sphere, principally because of the electroosmotic enhancement of fluid recirculation within the cavity induced by the sedimentation potential gradient. When the porous layer space charge and cavity wall surface charge have the same sign, the particle velocity is generally enhanced by the presence of the cavity. When these fixed charges have opposite signs, the particle velocity will be enhanced/reduced by the presence of the cavity if the wall surface charge density is sufficiently large/small relative to the porous layer space charge density in magnitude. The effect of the wall surface charge on the sedimentation of the soft sphere increases with decreases in the ratios of core-to-particle radii, particle-to-cavity radii, and particle radius-to-porous layer permeation length but is not a monotonic function of the ratio of particle radius-to-Debye length.

Effect of arrangement patterns of spheres encapsulating phase change material in packed beds on thermal performance

The NaNO3-KNO3 salt has the disadvantage of poor heat transfer capacity and low heat transfer efficiency in single-tank heat storage systems. However, molten salt can be used as phase change materials (PCM) and encapsulated with highly conductive sphere-shaped metals as PCM spheres. Arranging these spheres can appropriately change the situation. In this study, a heat storage system of a multilayer packed bed of PCM spheres consisting of NaNO3-KNO3 salt and type 316 stainless steel sphere shell was designed. This system's heat transfer and heat storage performance were also investigated using CFD simulation. For the same sphere diameter, the heat storage efficiency of hexagonal close packing (HCP) was 1.1 times that of cubic close packing (CCP). With the same porosity, the heat charging efficiency for the case using the 47.5 mm sphere diameter was the highest, at 99.3 %. When the number of layers of spheres was increased from 3 to 7, the heat flux through the sphere wall and the heat storage density of PCM spheres decreased from 40.8 kW and 67.3 × 105 kJ/m3 to 35.7 kW and 59.2 × 105 kJ/m3, respectively. Therefore, the heat charging efficiency of HCP was better than that of CCP. Reducing sphere size could shorten the heat transfer time and improve the heat storage efficiency. These numerical simulation results are consistent with the commonly known fact that the volumetric heat transfer intensity in the porous media is proportional to the reciprocal particle size since the smaller the particle size, the larger the contact area between the packing and the fluid. The conclusion drawn from the present findings provides an idea for designing a PCM heat storage system with high temperature and high efficiency of molten salt. The idea could also be used as a reference for the optimal design of a packed bed reactor.

Influence of upstream and downstream flow on different packed bed configurations in phase change process

One approach to storing latent heat in large quantities is through PBSS (Packed bed storage system) with spheres filled with PCM (Phase Change Materials). In these storage systems, an HTF (heat transfer fluid) flows over the spheres. So, both the sphere wall temperature and the heat flux can vary depending on the geometric conditions of the bed of spheres, the PCM thermodynamic conditions, and the HTF thermal conditions. Thus, this work aims to verify the influence of the thermal conditions of the external flow on the PBSS filled with PCM in the melting process. Cases with variable heat flux as well as uniform temperature and uniform heat flux conditions were tested. Three sphere positions, 4 sphere spacing ratios (blockage ratio), and three temperature differences between HTF and PCM phase change temperature were also analyzed, for two external flow directions (upstream and downstream), totaling 74 different configurations. The study found that the uniform temperature condition resulted in a 33 % faster total melting time than the uniform heat flow condition. Additionally, the upstream flow showed a total melting time that was approximately 24 % shorter than the flows in the opposite direction. The relationship between the total melting time and the temperature differences was found to be non-linear. Moreover, the blockage ratio showed a non-linear dependence with total melting time. The configuration with a blockage ratio of 1.125 demonstrated the shortest total melting time, with values on average 22.4 % shorter than the blocking ratio of 0.550, which had the longest melting times. These results demonstrate that optimizing external flow thermal conditions is crucial for improving the performance of PBSS with PCM-filled spheres in large-scale latent heat storage systems.

DRIFTS-MS Investigation of Low-Temperature CO Oxidation on Cu-Doped Manganese Oxide Prepared Using Nitrate Aerosol Decomposition.

Cu-doped manganese oxide (Cu-Mn2O4) prepared using aerosol decomposition was used as a CO oxidation catalyst. Cu was successfully doped into Mn2O4 due to their nitrate precursors having closed thermal decomposition properties, which ensured the atomic ratio of Cu/(Cu + Mn) in Cu-Mn2O4 close to that in their nitrate precursors. The 0.5Cu-Mn2O4 catalyst of 0.48 Cu/(Cu + Mn) atomic ratio had the best CO oxidation performance, with T50 and T90 as low as 48 and 69 °C, respectively. The 0.5Cu-Mn2O4 catalyst also had (1) a hollow sphere morphology, where the sphere wall was composed of a large number of nanospheres (about 10 nm), (2) the largest specific surface area and defects on the interfacing of the nanospheres, and (3) the highest Mn3+, Cu+, and Oads ratios, which facilitated oxygen vacancy formation, CO adsorption, and CO oxidation, respectively, yielding a synergetic effect on CO oxidation. DRIFTS-MS analysis results showed that terminal-type oxygen (M=O) and bridge-type oxygen (M-O-M) on 0.5Cu-Mn2O4 were reactive at a low temperature, resulting in-good low-temperature CO oxidation performance. Water could adsorb on 0.5Cu-Mn2O4 and inhibited M=O and M-O-M reaction with CO. Water could not inhibit O2 decomposition to M=O and M-O-M. The 0.5Cu-Mn2O4 catalyst had excellent water resistance at 150 °C, at which the influence of water (up to 5%) on CO oxidation could be completely eliminated.

Mechanical performance of hexagonal close-packed hollow sphere infill structures with shared walls under compression load

Infill structures of additive manufactured components give not only stability, but can be used as a design feature regarding lightweight and mechanical properties. In this study, an infill structure was investigated which consists of hollow spheres in a hexagonal closed packing. An additional characteristic is, that the contact between the spheres is modelled as an intersection. A script-based design approach was used for generating the structure within a cylinder. Thus, the sphere diameter, the sphere wall thickness and the outer shell thickness can be varied. The deformation behavior was studied using the Finite Element Method (FEM). Compression tests on additive manufactured cylindrical specimens verify the FEM results: (1) appropriate modelling of the contact between the spheres enhances the stability to the structure. (2) Increasing the relative density increases the mechanical properties. (3) Lower values for the relative sphere wall thickness result in an improved ductility.

In situ decoration of Co3O4 on N-doped hollow carbon sphere as an effective bifunctional oxygen electrocatalyst for oxygen evolution and oxygen reduction reactions

Transition metal oxide based materials are believed as a sustainable and effective electrocatalysts for oxygen evolution and oxygen reduction reactions (OER/ORR). However, poor conductivity, specific surface area, and tunable crystallography are major bottlenecks. To alleviate such issues, we developed a highly active spinel Co3O4 decorated N-doped hollow carbon sphere (Co3O4/NHCS) by single step decoration using cobalt phthalocyanine (CoPc) precursor for the first time. The introduction of various extents of CoPc significantly affects the sphere wall thickness, defect sites, doping amount of cobalt content, and the concentration of Co3+ and Co2+ sites. The resulting optimum loading of 0.2 g of Co3O4/NHCS-0.2, exhibits a highly uniform hollow carbon sphere with a high wall thickness (61 nm), better surface area (445 m2 g−1), and moderate defect sites. Notably, an exterior concentration of octahedral Co3+ (35.50%) and tetrahedral Co2+ (26.54%) sites serve as the active centres for OER and ORR, respectively. Remarkably, the obtained material exhibits exceptional OER performance with a potential of 1.80 V vs. RHE in 0.1 M KOH medium for achieving a current density of 10 mA cm−2, outperforming the benchmark RuO2 material. In addition, Co3O4/NHCS-0.2 demonstrates an impressive ORR electrocatalytic activity with onset potential of 0.89 V vs. RHE, excellent current density of 5.0 mA cm−2, lower Tafel slope of 60 mV dec−1 and close to four electron transfer. Moreover, the moderate carrier concentration, flat band potential, higher tetrahedral Co2+ and pyridinic N sites significantly improved the ORR activity and methanol oxidation tolerance ability.

Material and particle size sensitivity analysis on coefficient of restitution in low-velocity normal impacts

In many granular processes, impacts play a crucial role. These impacts are often described by the coefficient of restitution (COR). This COR does not only depend on impact velocity but also on the material pairing, the shape of impacting bodies, number of impacts, etc. This paper analyzes and compares the sensitivity of the COR for often seen material pairings metal–metal and metal–polymer. For experimental investigations, a steel sphere impacts different planar material probes in a defined manner, e.g., a sphere–wall contact is reproduced. While the metal–metal impacts show a significant dependency on impact velocity, the metal–polymer impacts show only little influence of the impact velocity. Also, repeated impacts onto the same spot have a significant influence on metal–metal impacts, while metal–polymer impacts are not affected. To gain insights not only about the macroscopic behavior of impacts but also about the microscopic behavior, finite element simulations are performed using an efficient 2D axisymmetric model and viscoelastic and elastic–viscoplastic material models. A good agreement between experiments and FEM simulations are achieved for the utilized material pairings. Then, the influence of the sphere’s size is studied. Afterward, a deeper look into the energy dissipation process during contact is investigated. Finally, the contact duration and normal force in the contact zone are studied experimentally.

CdS QDs modified three-dimensional ordered hollow spherical ZnTiO3-ZnO-TiO2 composite with improved photocatalytic performance

Three-dimensional ordered hollow spherical ZnTiO3-ZnO-TiO2 composite (3DOH ZnTiO3-ZnO-TiO2) was prepared by vacuum impregnation combined with calcination method using polystyrene (PS) colloidal microspheres as the template, and the CdS QDs were modified into 3DOH ZnTiO3-ZnO-TiO2 by water bath method. The crystal structure, chemical composition, surface morphology, optical absorption and surface physicochemical properties of CdS QDs modified 3DOH ZnTiO3-ZnO-TiO2 (CdS QDs 3DOH ZnTiO3-ZnO-TiO2) composite were well characterized. The results show that the three-dimensional ordered hollow spherical CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite mainly composes of anatase phase TiO2, rutile phase TiO2, and hexagonal phase ZnTiO3 and hexagonal phase ZnO. Among them, a homojunction is formed between the mixed crystal phase of TiO2 (anatase–rutile), and a heterojunction is found between hexagonal phase ZnTiO3 and hexagonal phase ZnO. In addition, the composite treated by the polystyrene (PS) colloidal microspheres template has formed the three-dimensional ordered hollow sphere structure, the hollow spheres are arranged neatly and orderly, and the sphere wall is formed by stacking nanoparticles. At the same time, the three-dimensional ordered hollow spherical structure of CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite provides more transfer paths for material transport and promotes repeated light absorption, prolonging the lifetime of photogenerated charge carriers. Moreover, due to the close connection between CdS QDs, ZnTiO3, ZnO and TiO2, the separation of electrons and hole pairs is facilitated, and the recombination of electron and hole pairs is effectively suppressed, so that CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite exhibits extremely high photocatalytic activity. Its hydrogen production is more than 300 times that of pure TiO2, moreover, of which cycle stability also shows better.

O-101 Neospermatogenesis benefits from a three-dimensional culture system

Abstract Study question Does a three-dimensional (3D) culture system increase the efficiency of male germline differentiation of mouse embryonic stem cells (mESC) over a bidimensional method? Summary answer Our 3D culture system based on direct spherification proves superior to the standard bidimensional plating in promoting neogametogenesis of mESC into post-meiotic male germ cells. What is known already Two-dimensional monolayer cell cultures are common in stem cell research. However, this method does not replicate a physiological 3D spatial relationship and may provide an inaccurate replication of in vivo environments. A 3D spherical structure allows us to mimic the seminiferous tubule, the site of in vivo spermatogenesis. By using spheroids as a scaffold to replicate cell culture systems, we can study spermatogenesis in a controlled setting. Direct spherification, a technique commonly used in molecular gastronomy, provides an opportunity to create spheroids that mimic in vivo events that materialize in the lab Study design, size, duration mESCs were initially cultured on a 6-well plate coated with fibroblasts and inserted into sodium alginate spheres. To coax differentiation, spheres (3 to 6 mm in diameter) were plunged directly into differentiation medium (DM) while the control mESC in 6-well dishes were layered with it. Cells obtained from both culture systems were tested by biomarkers for different germ cell stages Participants/materials, setting, methods Bidimensional mESC at 80% confluence were differentiated either on a plate or spherified for a 3D culture. Both systems underwent the same timeline of exposure to EpiLC medium with Activin A, bFGF and KSR for 3 days and PGCLC medium with BMP4, LIF, SCF and EGF for 7 days. Differentiated cells were retrieved from each method at day 3 and day 10 to assess for germ line differentiation markers, DAZL, VASA and BOULE Main results and the role of chance Under optic visualization through the sphere wall, cellular aggregation was seen on day 2 of culturing in EpiLC medium while this phenomenon was not observed on bidimensional plating. In the conventional method, cells expressed 7% DAZL (spermatogonium cell stage) and 1% VASA (pre-spermatid cell stage) whereas in direct spherification, cells expressed 20% DAZL (P < 0.001) and 15% VASA positivity (P < 0.0001). To further compare the different methods in later stages of germ-line differentiation, the remaining spheres were cultured in PGCLC medium for 7 days. At day 10, isolated cells were assessed for VASA and DAZL again. In the conventional method, 23% of cells expressed positivity for VASA and 29% DAZL whereas direct spherification achieved a positivity rate of 43% for VASA (P < 0.005) and 45% for DAZL (P < 0.005). This increased expression in both VASA and DAZL signify the increased number of cells undergoing germline differentiation. Additionally, BOULE was assessed for the presence of meiotic cells such as the spermatocyte. The conventional method yielded < 1% BOULE positivity whereas in direct spherification, there was 10% positivity (P < 0.005). Direct spherifcation result shows that differentiation almost doubled in comparison to the conventional method, yielding more post-meiotic cells in the same amount of time Limitations, reasons for caution Despite a higher differentiation rate in direct spherification, these cells would still need to be tested for their fertilization potential. The ability to achieve fertilization, blastocysts and live pups would provide final proof and reliability of this method of neogametogenesis Wider implications of the findings Differentiating ESCs through direct spherification provides an alternative to studying intercellular relationships. This provides an opportunity to study spermatogenesis in more detail by replicating the microenvironment of the seminiferous tubule. Once embryo developmental competence of the de novo gamete is confirmed, this may open a new chapter in human reproduction Trial registration number N/A

The hollow spherical nano-TiO2 particles synthesized from Ti-bearing blast furnace slag and the reaction model analysis

The hollow spherical nano-TiO2 was successfully synthesized by carbon spheres as the template and Ti-bearing blast furnace slag as the Ti source. The SEM and TEM results showed that the as-synthesized TiO2 consist of uniform separated hollow spheres, and the sphere wall was composed of nanoparticles. The XRD result showed that the crystallized phase was rutile. Almost complete extraction of Ti from slag was achieved in NaOH-NaF molten salt. The kinetic analysis indicated that the slag decomposition was applied to control of chemical reaction of the reactionless core-shrinking model, and the apparent activation energy was39.54 kJ mol-1 .

Transport of Lipophilic Anti‐Tuberculosis Drug Benzothiazone‐043 in Ca3(PO4)2 Nanocontainers

Abstract1,3‐Benzothiazin‐4‐one‐043 (BTZ043) is a novel anti‐mycobacterial agent for tuberculosis (TB) therapy with highly hydrophobic properties. In order to enhance local drug concentrations by improved administration and delivery to the site of the mycobacterial infection, we suggest BTZ043/Toc@Ca(ds)2@Ca3(PO4)2 nanocontainers made via a microemulsion approach for drug delivery (Toc: tocopherol; ds: dodecylsulfate). Based on our concept, the surfactant of the microemulsion itself is used to stabilize the droplet phase by interaction with Ca2+, followed by the formation of an inorganic Ca3(PO4)2 sphere wall in one‐pot reaction. Tocopherol (vitamin E) was used as biocompatible droplet phase of the microemulsion to dissolve the highly lipophilic BTZ043. According to electron microscopy and electron spectroscopy, the resulting BTZ043/Toc@Ca(ds)2@Ca3(PO4)2 nanocontainers exhibit an outer diameter of 28±8 nm and a sphere wall of 4±1 nm. The inner cavity, 18±7 nm in diameter, is loaded with BTZ043 with a concentration of 30.5 μg/mL. First in vitro tests with murine bone marrow derived macrophages infected with Mycobacterium tuberculosis show promising antibiotic activity of the BTZ043/Toc@Ca(ds)2@Ca3(PO4)2 nanocontainers.

Manufacture and characterization of a 3D-printed integrating sphere

3D printers are more accessible in both academic and research groups, becoming instruments to facilitate the construction of high-quality scientific equipment for laboratories. In the present study, a 3D printed integrating sphere was validated to acquire diffuse reflectance and transmittance on turbid samples in order to compute optical absorption and reduced scattering through the inverse adding doubling algorithm. The 3D printed integrating sphere was validated in three stages: analysis of the integrating sphere coating reflectance using two possible coating materials (barium sulfate powder and a mixture of barium sulfate and paint), the sphere wall reflectance, and using two accurate optical polyurethane phantoms to measure the absorption and reduced scattering coefficients. The results indicate that the system developed with this methodology shows satisfactory reflectance compared to commercial models and is able to acquire experimental diffuse reflectance and transmittance measurements to compute the optical coefficients of turbid samples due to the use of an inverse adding doubling (IAD) algorithm. However, this system is limited to the region from 500 to 1300 nm due to a decrease in the reflectance of the coating.

Study on the Microstructure and Compression of Composite Metal Foam Core Sandwich Panels

Stainless steel composite metal foam core sandwich panels (SS-CMF-CSP) were manufactured in large-scale panels and tested under quasi-static compression. Stainless steel face sheets were attached to the SS-CMF core using two methods: diffusion and adhesive bonding. Scanning electron microscope imaging revealed grain growth in both the matrix and sphere wall for the diffusion-bonded sandwich panels. The face sheets were found to not greatly affect the deformation of the SS-CMF core under compression. However, the diffusion-bonded SS-CMF-CSP yielded a stronger product primarily due to microstructural changes that occur during the diffusion bonding heat cycle within the SS-CMF core. The diffusion-bonded SS-CMF-CSP had a plateaus stress and densification stress 17 and 10 pct higher than its baseline SS-CMF, respectively. The large-scale manufacturing was improved, and additional samples were tested with a yield and plateau strength 75 to 80 pct higher than the initial SS-CMF samples. The improved diffusion-bonded SS-CMF-CSP showed similar strengthening, with a plateau stress 16 pct higher than its base SS-CMF. Finite element analysis was completed using IMPETUS Afea that advances the current modeling of SS-CMF and was found to be in good agreement with the experimental findings.

Tensile properties of composite metal foam and composite metal foam core sandwich panels

Steel-steel composite metal foam (SS-CMF) and composite metal foam core sandwich panels (SS-CMF-CSP) were manufactured and tested under quasi-static tension. The SS-CMF-CSP were manufactured by attaching stainless steel face sheets to a SS-CMF core using solid-state diffusion bonding. SEM imaging was used to inspect the microstructure of SS-CMF and compare it to that of SS-CMF-CSP. The results indicate a cohesive bond line at the interface of the core and the face sheets. The bare SS-CMF samples had an ultimate tensile strength between 75–85 MPa and a failure strain between 7.5–8%. The normalized tensile strength of the SS-CMF was approximately 24 MPa/(g/cm3), 410% higher than other comparable metal foams, with a specific energy absorption of 0.95 J/g under tension. The uniform porosities and strong bonding between the sphere wall and matrix seem to be the strengthening factor of SS-CMF under tension when compared to other metal foams. The ultimate tensile strength of the SS-CMF-CSP was 115% stronger than the bare SS-CMF at 165 MPa with an average failure strain of 23%. The normalized strength of the SS-CMF-CSP was 52% higher than the bare SS-CMF. The modulus of elasticity was approximated using the rule of mixtures for the SS-CMF and the SS-CMF-CSP and the experimental results were found to lie within the calculated upper and lower bounds.

Ratiometric pathlength calibration of integrating sphere-based absorption cells.

Chemical sensors based on optical absorption require accurate knowledge of the optical pathlength of the sample cell. Integrating spheres offer increased pathlengths compared to single pass cells combined with tolerance to misalignment, making them attractive for use in challenging environments subject to vibration. However, the equivalent optical pathlength can be degraded by dirt and / or condensation on the inner surface of the sphere. We present a new scheme for in-situ calibration that uses a ratiometric two-beam approach. Results are presented for an integrating sphere used in the measurement of methane by tunable diode laser spectroscopy (TDLS) at 1651nm. Reduced sphere reflectivity was simulated by applying small areas of black tape on the inner surface. At methane concentrations of 1500ppm and 3125 ppm, for areas of contamination up to 2.3% of the sphere wall, the technique reduced the error from over 50% to within ±4%. At a concentration of 6250 ppm and the most severe fouling corresponding to 2.9% wall coverage, the technique reduced the error from 55-65% to within ±11%.

One‐Pot Template‐Free Cross‐Linking Synthesis of SiOx–SnO2@C Hollow Spheres as a High Volumetric Capacity Anode for Lithium‐Ion Batteries

Porous SiOx anodes for Li‐ion batteries with a high volumetric energy density are desired. Herein, carbon‐coated SiOx–SnO2 hollow spheres are prepared by facile one‐pot high‐temperature annealing without using any template. During the process, SiOx is obtained through Sn reduction with the assistance of C. In the composite, the SiOx hollow spheres have a thin wall, the small SnO2 particles are uniformly imbedded in the sphere wall, and the SiOx–SnO2 hollow spheres are coated by cross‐linked carbon. As an anode, the composite has a large volumetric capacity (1339 mAh cm−3 at 0.1 A g−1), a high gravimetric capacity (1030 mAh g−1 at 0.1 A g−1), and a good cyclic stability (after 100 cycles, 90% capacity is retained compared with that of the second cycle at 0.5 A g−1). The high capacity and good cycle stability result from the superior structure of the composite. Furthermore, the thin wall of the sphere can timely release a large expanded volume during lithiation, and the conformal carbon also provides a framework to maintain the structural integrity and facilitate the formation of a stable solid–electrolyte interface.

Dynamic responses and energy absorption of hollow sphere structure subjected to blast loading

Closed-cell and open-cell hollow spheres were designed to develop lightweight cellular structures with excellent blast resistance, and the mechanical response of the hollow sphere structure (HSS) under blast loading was investigated numerically using ANSYS®/LS-DYNA®17.0. In this paper, the blast wave pressure decay rate was served as the main index of blast resistance while areal specific energy absorption and frame deformation were used as auxiliary indexes. The results indicated that the weight of HSS was reduced by 37.7%–69.8% compared to solid structures with the same physical size, and the blast resistance of HSS was significantly affected by the hollow sphere diameter and wall thickness, frame length and width, opening size and opening density. Closed-cell HSS with smaller hollow sphere diameters and thicker wall, or smaller frame lengths and widths would achieve the optimal blast resistance. Meanwhile, the blast resistance of HSS could be improved by adopting a smaller opening size, but the effect of opening density did not follow any rule, which was affected by the number and position of openings. Comprehensively, the blast resistance of HSS was enhanced when there was opening only at the face blast surface rather than at both the face blast surface and back blast surface.

Hierarchical Porous Carbon Cathode for Lithium–Sulfur Batteries Using Carbon Derived from Hybrid Materials Synthesized by Twin Polymerization

AbstractA new route of fabrication of cathodes for lithium–sulfur (Li–S) batteries with high cycle stability is reported. The cathodes are fabricated using porous carbon materials obtained from hybrid materials synthesized by twin polymerization on sulfonated polystyrene microparticles. The sulfonic acid groups act as room temperature catalyst for twin polymerization resulting in the formation of nanostructured phenolic resin/silica hybrid materials on the surface of sulfonated polystyrene particles. The shell formed by phenolic resin is transformed into carbon by simple pyrolysis and the polystyrene core is decomposed simultaneously at the pyrolysis temperature yielding porous carbon/silica nanocomposite hollow spheres. After silica removal, a hierarchical, highly porous carbon is obtained. Melt mixing of the carbon with sulfur is used for the fabrication of cathodes for Li–S batteries. The presence of silica on one hand imposes strength to the sphere wall during the carbonization and depolymerization of polystyrene, and on the other hand generates microporous carbon material for lithium–sulfur batteries. The nanostructured hybrid cathode allows very high capacity of 800–1000 mAh gsulfur −1 and remarkable reversible cycling stability and rate capability over 200 cycles at 0.1C rate and over 440 cycles at 1C rate for Li–S batteries.

Researches on compressive mechanical property of thin‐walled hollow spheres structure

AbstractThe compressive mechanical property of thin‐walled hollow spheres structure is researched by experiment and finite element method in this paper. Due to the ideal elastic‐plastic material and extremely thin but uniform wall thickness, Ping‐Pong balls are bonded together with a linking neck to comprise the ideal model of thin‐walled hollow spheres structure. The experimental result validates the effectiveness of the finite element model. The effects of the material and geometry parameters of the spheres and linking neck are then investigated by finite element method. The results reveal that: 1) The deformation process of the two‐ball bonding structure includes four stages: elastic deformation, axisymmetric buckling, forming non‐axisymmetric polygon and transforming to axisymmetric mode (or structural self‐contact behavior); 2) the Young's modulus and initial yield stress are basically unaffected by the linking neck center thickness, but they increase linearly with the hollow sphere wall thickness and linking neck radius as well as the Young's modulus and yield stress of material, and the linear correlation of the material yield stress is the lowest; 3) the strain of structural self‐contact behavior increases with the linking neck center thickness and radius.