Ultrathin Walls Research Articles

Hexagonally connected submicron hollow veins for high efficiency, narrow beam organic emitters

This study presents a hexagonal array of submicron hollow veins covered with a high-refractive-index (n) ceramic layer for extracting and steering light trapped in organic light-emitting diodes (LEDs). The hollow veins sustained by an ultrathin (35 nm in thickness) alumina wall were fabricated on a glass substrate by sequentially using nanoimprinting lithography, atomic layer deposition, and calcination processes, followed by sputtering a Si3N4 (n = 2.0) or TiO2 (n = 2.4) cover. A more pronounced scattering signal was revealed by dark-field imaging and scattering spectroscopy for the TiO2-cover sample. Measurements of photonic band dispersion via evanescent-field coupling demonstrated that the TiO2-cover sample surpassed the Si3N4-cover sample in extracting light trapped by total internal reflections in the glass substrate. The extraction efficiency of hollow vein embedded ceramic films was evaluated by conducting ray-wave integrated optics simulations on millimeter-scale (0.25 × 0.25 × 0.10 mm3) organic LEDs for covers with different n values. The incorporation of a cover with n = 2.4 maximized the extraction efficiency because of the dramatically enhanced top emission (i.e., a 2.8-fold enhancement relative to an unpatterned organic LED) through the glass substrate, thereby leading to a narrow beam angle of 30º.

Ultrathin Porous Carbon Nitride Bundles with an Adjustable Energy Band Structure toward Simultaneous Solar Photocatalytic Water Splitting and Selective Phenylcarbinol Oxidation

AbstractActiniae‐like carbon nitride (ACN) bundles were synthesized by the pyrolysis of an asymmetric supramolecular precursor prepared from L‐arginine (L‐Arg) and melamine. ACN has adjustable band gaps (2.25 eV–2.75 eV) and hollow microtubes with ultrathin pore walls, which enrich reaction sites, improve visible‐light absorption and enhance charge separation. In the presence of phenylcarbinol, ACN exhibited excellent water‐splitting ability (95.3 μmol h−1) and in the meanwhile phenylcarbinol was selectively oxidized to benzaldehyde (conversion of 90.9 %, selectivity of 99.7 %) under solar irradiation. For the concurrent reactions, 2D isotope labeling, separation, and detection were conducted to confirm that the proton source of released hydrogen is water. The mechanism of water splitting and phenylcarbinol oxidation was also investigated.

Hollow platinum tetrapods: using a combination of {111} facets, surface concave topology, and ultrathin walls to boost their oxygen reduction reactivity

Hollow Pt tetrapods with {111} facets, surface concave topology, and ultrathin walls exhibit superior electro-catalytic activity and stability towards the acidic oxygen reduction reaction.

Direct detection of inorganic ions and underivatized amino acids in seconds using high-speed capillary electrophoresis coupled with back-scatter interferometry.

High speed capillary electrophoresis (HSCE) combined with refractive index (RI) detection is developed for the rapid separation and detection of inorganic ions and amino acids. A mixture of three inorganic ions (K+, Na+, Li+) and eight amino acids (Lys, Arg, Ala, Gly, Val, Thr, Trp, Asp) are detected using back scatter interferometry (BSI), without the need for chemical modifications or contrast. A thin-walled separation capillary (50 μm i.d. by 80 μm o.d.) helps mitigate Joule heating at the high field strengths required for rapid separations. This, combined with a short 8 cm length-to-detector (10 cm total length), enables separations on the seconds time scale. Using a background electrolyte (BGE) of 4 M acetic acid (pH 1.6) and a field strength of 900 V cm-1, all 11 analytes are separated in less than 40 s. Moreover, peaks in the BSI signal arising from the sample injection and EOF, enable electrophoretic mobilities to readily be obtained from apparent mobilities. This leads to excellent repeatability, with analyte electrophoretic mobilities varying from 0.39 to 1.56 % RSD over eight consecutive separations. The universal detection of inorganic ions and amino acids without prior chemical modification or additives in the BGE is an advantage of refractive index detection. A disadvantage arises from modest detection limits. Here, however, we show that submicromolar detection is possible with careful thermostatting of the thin separation capillary. A series of electropherograms are used to quantify arginine concentrations from 700 nM to 500 μM, using 50 μM Li+ as an internal standard. The resulting calibration curve leads to a calculated LOD of 376 nM and a LOQ of 1.76 μM. Diagnostically relevant amino acid panels are also separated, illustrating the potential for future applications in neurodegenerative and metabolic disease diagnostics. HSCE combined with BSI detection, therefore, is shown to be a rapid, sensitive, and universal approach for analyzing sample mixtures.

Amorphous Fe nanoclusters embedded inside balloon-like N-doped hollow carbon for efficient electrocatalytic oxygen reduction

Rational designs of electrocatalytic active sites and architectures are of great importance to develop cost-efficient non-noble metal electrocatalysts towards efficient oxygen reduction reaction (ORR) for high-performance energy conversion and storage devices. In this work, active amorphous Fe-based nanoclusters (Fe NC) are elaborately embedded at the inner surface of balloonlike N-doped hollow carbon (Fe NC/Ch sphere) as an efficient ORR electrocatalyst with an ultrathin wall of about 10 nm. When evaluated for electrochemical performance, Fe NC/Ch sphere exhibits decent ORR activity with a diffusion-limited current density of ∼5.0 mA/cm2 and a half-wave potential of ∼0.81 V in alkaline solution, which is comparable with commercial Pt/C and superior to Fe nanoparticles supported on carbon sheet (Fe NP/C sheet) counterpart. The electrochemical analyses combined with electronic structure characterizations reveal that robust Fe−N interactions in amorphous Fe nanoclusters are helpful for the adsorption of surface oxygen-relative species, and the strong support effect of N-doped hollow carbon is benefitial for accelerating the interfacial electron transfer, which jointly contributes to improve ORR kinetics for Fe NC/Ch sphere.

Critical assessment of the impact of process parameters on vertical roughness and hardness of thin walls of AlSi10Mg processed by laser powder bed fusion

This work deals with the impact of prominent process parameters in laser powder bed fusion (L-PBF) technique, also called selective laser melting (SLM), on relevant properties of AlSi10Mg such as surface roughness and hardness. More particularly, the influence of scanning strategies, track energy density (TED), and of the offset between the contours and the bulk hatching were scrutinized. Basic thin structures such as single wall tracks (SWT) and ultra thin walls (UTW) were used to isolate the effect of the TED and of the offset between parallel melt pool tracks on the vertical roughness, respectively. It is shown that the TED reduces the level of roughness mostly due to a geometrical effect. The optimum range of TED is shown to be at the beginning of the keyhole conditions, at the expense of the amount of sub-surface porosities and of hardness. Increasing the offset also allows reducing the roughness. Thicker structures with contours and bulk hatching were also used and brought the same conclusions. In this work, low levels of roughness (about 4 μm) have been obtained on vertical walls without any post-treatment but at the expense of the mechanical properties.

Symmetric sponge-like porous polybenzimidazole membrane for high temperature proton exchange membrane fuel cells

Conductive porous membranes are promising for environmental and energy applications. Here, a novel symmetric sponge-like porous poly[2,2’-(4,4′-oxybis(1,4-phenylene))-5,5′-bibenzimidazoles] (OPBI) membrane used for high temperature proton exchange membrane fuel cells was successfully fabricated by vapor-induced phase separation (VIPS). Typically, the symmetric sponge-like porous OPBI membrane exhibits thousands of micron-sized cells separated by ultra-thin walls, which are characterized by SEM micrographs. Porous membrane exhibits considerably enhanced acid doping level (ADL) of 9.6 and proton conductivity of 70.8 mS cm−2 at 180 °C compared with the corresponding dense membranes (OPBI: ADL = 4.1). Interestingly, with higher ADL, the porous OPBI membrane showed much lower swelling ratio in in-plane direction (50%) and thus higher dimensional stability than dense OPBI (74%) and mPBI (103%). Moreover, the open circuit voltage (OCV) of the fuel cell based on the porous membrane was 0.86 V indicating the low gas crossover and the fuel cell showed excellent peak power density of 485.3 mW/cm2 at 160 °C, higher than m-membrane of 353.1 mW/cm2 and OPBI membrane of 38.7 mW/cm2. Though the single cell durability is poor for porous OPBI membrane than that of m-PBI due to the leach of PA, the combination of the facile fabrication procedure, high performance and easy up-scaling enables the PBI porous membranes to be promising for high temperature proton exchange membrane fuel cells. Further work for us is to adjust the size of the pores and porous structure, thus improving the PA retention of porous membranes.

Millimeter-Scale Soft Continuum Robots for Large-Angle and High-Precision Manipulation by Hybrid Actuation.

Developing small‐scale soft continuum robots with large‐angle steering capacity and high‐precision manipulation offers broad opportunities in various biomedical settings. However, existing continuum robots reach the bottleneck in actuation on account of the contradiction among small size, compliance actuation, large tender range, high precision, and small dynamic error. Herein, a 3D‐printed millimeter‐scale soft continuum robot with an ultrathin hollow skeleton wall (300 μm) and a large inner‐to‐outer ratio (0.8) is reported. After coating a thin ferromagnetic elastomer layer (≈100–150 μm), the proposed soft continuum robot equipped with hybrid actuation (tendon‐ and magnetic‐driven mode) achieves large‐angle (up to 100°) steering and high‐precision (low to 2 μm for static positioning) micromanipulation simultaneously. Specifically, the robot implements an ultralow dynamic tracking error of ≈10 μm, which is ≈30‐fold improved than the state of art. Combined with a microneedle/knife or nasopharyngeal swab, the robot reveals the potential for versatile biomedical applications, such as drug injection on the target tissue, diseased tissue ablation, and COVID‐19 nasopharyngeal sampling. The proposed millimeter‐scale soft continuum robot presents remarkable advances in large‐range and high‐precise actuation, which provides a new method for miniature continuum robot design and finds broad applications in biomedical engineering.

Enhanced magnetic and photocatalytic properties of BiFeO3 nanotubes with ultrathin wall thickness

In this work, hollow BiFeO3 nanotubes with ultrathin wall thickness were successfully synthesized via a template approach by using anodic aluminum oxide (AAO) as the template. The structure, morphology, magnetic properties and photocatalytic activity of the hollow BiFeO3 nanotubes were characterized in detail. The results showed that the as-prepared BiFeO3 nanotubes exhibited hollow tubular structure with external diameter of ~50 nm and wall thickness of 5 nm, respectively. In addition, enhanced magnetic properties with saturation magnetization (Ms) value of 1.74 emu·g−1, low photoluminescence (PL) intensity and large surface-to-volume ratio were observed. Compared to the BiFeO3 nanofibres and BiFeO3 nanoparticles, the BiFeO3 nanotubes exhibited the best photocatalytic activity and stability to the degradation of methylene blue (MB) under visible light irradiation. According to the analysis of the photocatalytic mechanism, the enhanced photocatalytic activity can be ascribed to the unique one-dimensional hollow nanotubular structure with ultrathin wall thickness and enhanced magnetic properties.

Research on machining technology of high speed and ultra-thin wall parts

This paper mainly analyzes and experiments the processing technology of high speed (12000 r/min) and large proportion thin-wall parts (thickness/width = 1:80 and thickness/height = 1:120), so as to guide the machining of closed centrifugal impellers in aerospace. In this process, low melting point alloy is selected as the filling material to increase the rigidity of thin-walled parts and improve the indicated roughness of parts. Different low melting point alloy filling structures are carried out on large proportion of thin-wall sample parts. In addition, an auxiliary angle R is added at the stress concentration of the part itself to reduce the vibration caused by the machining path. For the results of simulation and test, the parts without filling low melting point alloy can not be processed and used at all, while the “tower” filling structure has fine cracks at the top of the thin-walled parts. The “column” filling structure increases the rigidity by about 19.97 % and the roughness by about 50 %.

Recent improvements in straw neutron detectors for large-scale neutron science instruments

Modified boron-coated straw (BCS) detector configurations are introduced, in order to improve detection efficiency, and reduce the number of layers required to match the response of high-pressure 3He tubes, in large-scale neutron science instruments. A new 7-straw design employing thin-walled aluminum tubes facilitates operation in vacuum, and substantially reduces the scattering material by a factor of 5 compared with the flow-through design of the Multi-Grid detector. Another design introduces 18 radial walls inside each straw, coated on both sides with enriched boron carbide, to increase the coated wall perimeter 4.3 times. The so-called Pie straw offers a significant benefit in detection efficiency compared with round straws used in LoKI. An example of such a straw having 18 septa is explored in modeling and experimental studies, that can potentially reduce the number of layers needed in large-scale instruments like LoKI by a factor of 2.8. In a parallel development, a totally new configuration of boron-coated detectors is introduced, aimed to address the need for high spatial resolution, and high-rate capability in single crystal diffractometers, like MaNDi and TOPAZ at the SNS, and in neutron reflectometers. The proposed structure is a close-packed array of rectangular cells, each fabricated by wrapping copper foil having a coating of 10B4C on one side and electroplated tin on the other side, around precisely machined rectangular bars. The array is pressed together and then vacuum brazed together. The resulting structure is quite strong and precise in geometry. This so-called Microcell Straw Array can be configured with channel dimensions as small as 0.5 mm × 2.5 mm. Due to its ultra thin walls (25 μm) secondary scattering of neutrons is minimized. It is sealed inside a fully welded thin aluminum containment vessel that allows convenient operation in vacuum. A mature low power readout system capable of an estimated count rate of 22 MHz in a 15 × 15 cm2 detector is also proposed. The improvements are the result of recent advances in BCS design, spurred by the development of compact, high-sensitivity monitors for homeland security and military applications.

Fusiform-Shaped g-C3 N4 Capsules with Superior Photocatalytic Activity.

Carbon nitride (g-C3 N4 ) nanostructure rebuilding is an effective means to modify its photocatalytic properties, especially the hollow micron-nanostructure. The increased scattering in the body effectively improves the light utilization efficiency and improves catalytic properties. In this work, fusiform-shaped g-C3 N4 capsules are created by controlling the nucleation kinetics of supramolecular assemblies. The fusiform-shaped capsule micron-nanostructure is synthesized with ultrathin wall thickness and adjusted carbon/nitride ratios which decrease the recombination rate of photo-generated carriers. The hollow nanostructure and relatively higher specific surface area of the fusiform-shaped capsule effectively enhance light scattering inside body and lead to an enhanced carrier utilization efficiency. Moreover, the decrease of bandgap and relatively negative conduction band position affect the response of hollow fusiform-shaped g-C3 N4 capsules (Hf-g-C3 N4 ) in visible light region and improve the photo-reducing performance. In term of H2 evolution property, Hf-g-C3 N4 has been improved to 7052 µmol g-1 h-1 , which is 10.9 times higher compared with bulk structure. More importantly, Hf-g-C3 N4 can produce CH4 at the rate of 1.63 µmol g-1 h-1 without help of co-catalyst and hole sacrificial agent in the photocatalytic reduction reaction of CO2 to CH4 . At same time, the selective photocatalytic reduction of CO2 is another advantage of Hf-g-C3 N4 .

Deformation Property and Suppression of Ultra-Thin-Walled Rectangular Tube in Rotary Draw Bending

Recently, miniaturization and weight reduction have become important issues in various industries such as automobile and aerospace. To achieve weight reduction, it is effective to reduce the material thickness. Generally, a secondary forming process such as bending is performed on the tube, and it is applied as a structural member for various products and a member for transmitting electromagnetic waves and fluids. If the wall thickness of this tube can be thinned and the bending technology can be established, it will contribute to further weight reduction. Therefore, in this study, we fabricated an aluminum alloy rectangular tube with a height H0 = 20 mm, width W0 = 10 mm, wall thickness t0 = 0.5 mm (H0/t0 = 40) and investigated the deformation properties in the rotary draw bending. As a result, the deformation in the height direction of the tube was suppressed applying the laminated mandrel. In contrast, it was found that the pear-shaped deformation peculiar to the ultra-thin wall tube occurs. In addition, axial tension and lateral constraint were applied. Furthermore, the widthwise clearance of the mandrel was adjusted to be bumpy. As a result, the pear-shaped deformation was suppressed, and a more accurate cross-section was obtained.

User experience for manual injection of 2 mL viscous solutions is enhanced by a new prefillable syringe with a staked 8 mm ultra-thin wall needle

ABSTRACT Objectives User experience was compared between a new pre-fillable 2.25 mL glass syringe equipped with an ultra-thin-wall (UTW) 8 mm staked needle and a marketed BD Neopak™ syringe equipped with a special-thin-wall (STW) 12.7 mm staked needle. Methods Participants simulated subcutaneous injections with both syringes alone (formative Human Factors study) and in combination with a needlestick-prevention device (validation Human Factors study). Results Usability results of both studies showed higher success rates for delivering the full dose of 2 mL viscous solution (30 cP) with the 8mmUTW syringe than with the 12.7mmSTW one (63% vs. 42% in the formative study). The use of the 8mmUTW syringe demonstrated also better ease of use and acceptance results and 72% of formative study participants preferred this new syringe over the current one when delivering the viscous solution. Using a shorter needle also showed a benefit in decreasing the injection-related anxiety. Besides, in the case of a non-recommended injection technique, the calculated risk of accidental intramuscular injection is reduced by 2 to 13 times with the 8mmUTW syringe. Conclusion Altogether, the results obtained demonstrated an improvement of the user experience with this new syringe compared to the current one in the manual delivery of 2 mL viscous solutions.

Dimensional Optimization of Electric Component in Ultra Thin-wall Injection Molding by Using Moldflow Simulation

Dimensional Optimization of Electric Component in Ultra Thin-wall Injection Molding by Using Moldflow Simulation

Optimization of spinning process parameters for the large-diameter thin-walled cylinder based on the drum shape

Thinning spinning has the advantage of enhancing the performance of a product, and it is an effective method for manufacturing large-diameter ultrathin cylindrical parts. However, the rigidity of a large-diameter ultrathin wall cylinder is poor, the spinning process and forming quality are sensitive to the process parameters, and the drum-shaped result of the spinning process is prone to instability, which can cause the spinning process to be unbalanced. Therefore, it is a great challenge to select the appropriate process parameters for achieving the long-range stable spinning of large-diameter ultrathin wall cylinders. Based on the analysis of the thin-walled cylinder spinning mechanism, this study analyzed the effects of key process parameters on the drum shape of a C-276 thin-walled cylinder spinning process by serial experiments. The results of serialization experiments show that the thinning rate has a great influence on the spinning process state, the feed rate is secondary, and the speed has the least influence. On the basis of experimental analysis, the optimized process parameters of thin-walled cylinder spinning are obtained by using the support vector machine method: the wall thickness reduction rate cannot exceed 45% in single-pass spinning; 30~40% is a reasonable choice interval; the feed rate can range from 0.8 to 1.0 mm/r; and the rotation speed can range from 80 to 100 r/min. Finally, a comparative experiment and stability test of thin-walled cylinder thinning spinning over a long range is carried out, which verifies that the optimized spinning parameters can be used for the long-range stable spinning of large-diameter ultrathin cylinder parts.

High-Speed Capillary Electrophoresis Using a Thin-Wall Fused-Silica Capillary Combined with Backscatter Interferometry.

High-speed capillary electrophoresis (HSCE) is implemented using a 10 cm total length fused-silica capillary (50 μm i.d., 80 μm o.d.) combined with refractive index (RI) detection using backscatter interferometry (BSI). The short capillary length reduces analysis time while the ultrathin wall (15 μm) efficiently dissipates heat from the separation channel, mitigating the deleterious effects of Joule heating. The separation capillary is mounted on a temperature-controlled heat sink that stabilizes the temperature to ±0.004 °C. This temperature stabilization improves separation efficiency and enhances RI detection. Ohm's Law plots confirm the superior heat dissipation of the HSCE capillary compared to a similarly prepared conventional CE capillary (50 μm i.d., 363 μm o.d.). The speed and efficiency of HSCE combined with universal RI detection is illustrated through the separation of K+, Ba2+, Mg2+, Na+, Li+, and Tris+ in approximately 30 s, with efficiencies greater than 500 000 plates/m. Run-to-run repeatability is explored using nine consecutive electrokinetic injections of a K+, Na+, and Li+ mixture. The average migration times and %RSD for K+, Na+, and Li+ were measured to be 22.04 s (1.59%), 26.81 s (1.38%), and 29.80 s (2.21%), respectively. Finally, we show that the BSI signal is sensitive to the separation voltage through the Kerr mechanism. This leads to peaks in the electropherogram from the injection process that are useful for precisely defining the start of each separation and quantifying the amount of sample injected onto the capillary.

Stability research on spinning of ultra-thin-wall aluminum alloy tube

In this paper, the instability in spinning process of ultra-thin-wall tube is analyzed, and the influence law of different parameters of roller and main process parameters in spinning forming process. Firstly, the forward spinning finite element model of ultra-thin wall tube is established and its reliability is verified. It is concluded that the instability of ultra-thin-wall aluminum alloy tube during spinning is caused by its poor rigidity and material flow disorder. The effects of different parameters of roller (roller diameters, roller forming angles and roller corner radii) and the main process parameters (feed rates, friction coefficients and thinning rates) on the equivalent plastic strain and diameter expansion amount in spinning forming process were investigated. The results show that the influence of each parameter on the stability of ultra-thin-wall is quite different. The influence of roller corner radius is stronger than roller diameter and much stronger than roller forming angle. The influence that feed rate does the expansion amount to exist a minimum value. The friction coefficient and thinning rate have positive correlation with expansion amount. The optimum combination of process parameters was further determined, and the accuracy of the results was verified by experiments, which provided reference and guidance for actual production.

Coal-based ultrathin-wall graphitic porous carbon for high-performance form-stable phase change materials with enhanced thermal conductivity

Creating coal-based new materials and finding their new applications are important for sustainable chemistry and engineering of coals. Here, we prepared a new kind of coal-derived three-dimensional graphitic porous carbon (denoted as GPC) for form-stable composite phase change materials. The ultrathin graphitic walls of this material enhanced thermal conductivity and shape stability. This hierarchical porous material exhibits a specific surface area of 1351 m2·g−1, which is rarely achieved in coal-derived carbons. It provides a high loading capacity of solid-liquid phase change materials (e.g., paraffin) with shape stability and high specific thermal storage density. The loaded 90 wt% paraffin@GPC composite achieved a reversible melting enthalpy of 187.4 kJ·kg−1, standing for a 7.8% increase than the theoretical value calculated from the loading amount. In addition, the highly porous GPC provides abundant sites for solidification nucleation of paraffin and therefore obtains high endo-/exo-thermal stability. The thin graphitic walls of GPC render the 90 wt% composite with an enhanced thermal conductivity of 0.58 W·m−1·K−1, which is beneficial to deliver rapid thermal transfer from outside in. The structural and thermal properties of this low-cost coal-based GPC reveal new potential applications for thermal storage.

Fabrication of rGO/g-C3N4@SnS2 and its rate-performance enhancement

Poor cycling performance of SnS2 induced by the initial structural transformation and subsequent volumetric expansion during lithiating process hinders the widespread application of SnS2 in lithium ion batteries despite its high theoretic capacity. A simple approach promoting the performance of SnS2 is proposed here via strategically introducing rGO/g-C3N4 hybrid to form a robust framework in the designed SnS2 composite. Nano-composite of rGO/g-C3N4@SnS2 where hollow SnS2 spheres with ultra-thin walls are combined with rGO/g-C3N4. The prepared rGO/g-C3N4@SnS2 possesses excellent lithium storage and high rate performance with a recovered capacity of 864.93 mAh/g at the current density of 800 mA/g.