Ultrathin Wall Thickness Research Articles

Axially slow-variation microbubble resonators fabricated by an improved arc discharge method for strain sensing applications

In this paper, we proposed an axially slow-variation microbubble resonator fabricated by an improved arc discharge method and applied to axial strain sensing. The prepared resonators are characterized by ultra-thin wall thickness and axial slow-variation. The wall thickness was experimentally measured to reach 938 nm and maintain a quality factor of an optical mode as large as 7.36 ×107. The main factors affecting the strain sensitivity of the microbubble resonators are investigated theoretically and experimentally. Experimentally, the maximum sensitivity measured was 13.08pm/µε, which is three times higher than the microbubble resonators without this method. The device is simple to prepare and possesses ultra-thin wall thickness. It is promising for applications in high-precision sensing, such as single molecule and biological sensing.

Wall thickness control in multi-stage hydroforming of multiwave seal ring with small diameter

Thinning rate is a crucial factor in forming quality of the thin-walled seal ring with complex features. To control the excessive thinning by altering the stress state during the material deformation, a new multi-stage three-dimensional (3D) hydroforming technology was proposed in this work. Based on the characteristics of the seal ring and the used superalloy strip, a multi-stage internal pressure forming process was established through finite element analysis (FEA) and forming experiment verification. In addition, the distribution of wall thickness in every stage was discussed. And the influence of the width of deformation zone and the pressure loading path in the cavity on the wall thickness of the part in each step was studied. Finally, the optimal forming parameters of each step that can achieve a stable state of metal flow were obtained. The experimental results demonstrated that the developed 3D hydroforming technology can accurately control the material flow in the multi-stage forming of the multi-wave seal ring with small-diameter and ultrathin wall thickness. For the optimized parameter combination, the blank dimensions of deformation zone are 8 mm in the first step and 18 mm in the second step, while the pre-bulging pressure is 9 ~ 12 MPa and the maximum pressure is 100 MPa in the two steps.

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.

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 .

Rapid oxidation-etching synthesis of low-crystalline δ-MnO2 tubular nanostructures under ambient with high capacitance

The 1D low-crystalline and ultrathin MnO2-RT nanotubes consisted of tiny nanoflakes are rapid synthesized at ambient temperature through a facile oxidation-etching method, where Cu nanowires are served as sacrificial templates. Meanwhile, the MnO2-RT nanotubes can be undergone further nucleation and growth to generate 3D porous MnO2 nanotubes by calcination treatment and hydrothermal reaction, respectively. Importantly, the high specific capacitance of 384.6 F g−1 is obtained at the current density of 0.25 A g−1 for the low-crystalline MnO2-RT nanotubes, owing to its ultra-thin wall thickness, high surface area and highly disordered structure. Furthermore, the cycle stability of the low-crystalline MnO2 nanotubes can be improved by hydrothermal treatment, owing to the enhanced crystallinity.

High rate-performance supercapacitor based on nitrogen-doped hollow hexagonal carbon nanoprism arrays with ultrathin wall thickness in situ fabricated on carbon cloth

Free-standing carbon materials are promising supercapacitor electrode materials due to their outstanding properties, such as simple assemble process, high rate performance and good stability etc. We present here the fabrication of novel nitrogen-doped hollow hexagonal carbon nanoprism arrays on carbon fiber cloth for supercapacitor via chemical vapor deposition with ZnO as the sacrifice template. The hexagonal nanoprism structure of ZnO template can be well duplicated by ultrathin nitrogen-doped carbon layer through an in situ carbon deposition process. In this method, the template-removing step is not necessary attributed to the carbothermal reduction reaction between ZnO and carbon during the chemical vapor deposition process. The carbon fibers serve as highways for rapid electron transfer. Meanwhile, the in situ growth of nanoprism arrays on carbon fiber results in intact interface and low interface resistance. The open channel structure of the carbon arrays can shorten the ions diffusion path and facilitate the fast electrolyte transport. All these structural advantages contribute to the excellent rate performance of the fabricated carbon composite with scan rate and current density reaching up to 20 V s−1 and 300 mA cm−2, respectively. The present work paves a new way for designing high-rate and highly stable carbon electrode materials for supercapacitors.

Engineering the surface structure of porous indium oxide hexagonal nanotubes with antimony trioxide for highly-efficient nitrogen dioxide detection at low temperature

The development of cost-effective In2O3-based sensors exhibiting high sensitivity and selectivity to NO2 at low temperature is still a challenge. For the first time, Sb2O3 modified porous In2O3 hexagonal nanotubes (Sb2O3/In2O3 HNTs) have been synthesized for highly efficient NO2 sensing. Texture characterizations indicate that Sb2O3/In2O3 HNTs with ultrathin wall thickness of ca. 20 nm and big inner diameter of ca. 500 nm displays high specific surface area of 100.3 m2·g−1. Gas sensing property tests display that In2O3 HNTs with Sb2O3 loading of 1.5 mol% exhibit high response (Rg/Ra = 47), superior selectivity and short response/recovery time (80/85 s) to 1 ppm NO2 in comparison with reported other sensing-materials at 80 °C, and the detection limit of Sb2O3/In2O3 HNTs toward to NO2 is down to 50 ppb (S = 2). The mechanism investigations reveal that the hetero-junction at Sb2O3/In2O3 interfaces, catalytic function of Sb2O3, and high specific surface area result in the high response, superior sensitivity, and short response/recovery time of Sb2O3/In2O3 HNTs sensors at low temperature. Therefore, this work provides a promising candidate for the development of high-performance sensor to NO2 gas at low temperature.

Ultrathin Wall (1 nm) and Superlong Pt Nanotubes with Enhanced Oxygen Reduction Reaction Performance.

The synthesis of Pt nanotubes catalysts remains a substantial challenge, especially for those with both sub-nanometer wall thickness and micrometer-scale length characteristics. Combining techniques of insulin fibril template with Pd nanowire template, numerous Pt nanotubes with diameter of 5.5 nm, tube-length of several micrometers, and ultrathin wall thickness of 1 nm are assembled. These tubular catalysts with both open ends deliver electrochemical active surface area (ECSA) of 91.43 m2 gpt-1 which results from multiple Pt atoms exposed on the inner and outer surfaces that doubled Pt atoms can participate in catalytic reactions, further with enhanced electrocatalytic performance for oxygen reduction reaction (ORR). The ultrafine Pt nanotubes represent a class of hollow nanostructure with increased Pt-utilization and large ECSA, which is regarded as a type of cost-effective catalysts for ORR.

Solvent-free synthesis of N-doped carbon coated ZnO nanorods composite anode via a ZnO support-induced ZIF-8 in-situ growth strategy

The N-doped carbon coated ZnO nanorods (ZnO/NC-Z NRDs) are synthesized through a simple solvent-free method, in which the N-doped carbon is derived from thermal treatment of the in-situ grown zeolitic imidazolate framework-8 (ZIF-8) on the surface of ZnO NRDs. The in-situ coated N-doped carbon layer can not only enhance the electrical conductivity of ZnO NRDs and thus increasing the diffusion rate of Li ions, but also serve as a buffer layer to impede the volume expansion during the charge-discharge processes. When utilized as anodes for lithium-ion batteries (LIBs), the as-synthesized ZnO/NC-Z NRDs deliver a high capacity of 1011mAhg−1 at 200mAg−1 after 200 cycles and remain 544mAhg−1 at 1000mAg−1 after 850 cycles, holding a capacity retention of as high as 87.7%. In addition, the as-synthesized ZnO/NC-Z NRDs can also act as a precursor for the preparation of high performance N-doped carbon tube (1001.1mAhg−1 at 200mAg−1 with the retention of 99.1% after 100 cycles) with an ultrathin wall thickness. Such solvent-free synthetic method can not only simplify the synthesis process, but also pave a new strategy to synthesize Zn-based materials for the application of energy storage devices.

Aqueous synthesis of mesostructured BiVO4 quantum tubes with excellent dual response to visible light and temperature

Analysis of the atomic structure of monoclinic BiVO4 reveals its fascinating structure-related dual response to visible light and temperature. Although there have been a few reported studies of its responses to visible light and temperature, an understanding of the effects of quantum size, particle shape or specific exposed facets on its dual responsive properties remains elusive; this is primarily due to the limited availability of high-quality monodisperse nanocrystals with extremely small sizes and specific exposed facets. Herein, we describe a novel assembly-fusion strategy for the synthesis of mesostructured monoclinic BiVO4 quantum tubes with ultranarrow diameter of 5 nm, ultrathin wall thickness down to 1 nm and exposed {020} facets, via a convenient hydrothermal method at temperatures as low as 100 °C. Notably, the resulting high-quality quantum tubes possess significantly superior dual-responsive properties compared with bulk BiVO4 or even BiVO4 nanoellipsoids, and thus, show high promise for applications as visible-light photocatalysts and temperature indicators offering improved environmental quality and safety. This mild and facile methodology should be capable of extension to the preparation of other mesostructured inorganic quantum tubes with similar characteristics, giving a range of materials with enhanced dual-responsive properties.

Molecular Imprinting at Walls of Silica Nanotubes for TNT Recognition

This paper reports the molecular imprinting at the walls of highly uniform silica nanotubes for the recognition of 2,4,6-trinitrotoluene (TNT). It has been demonstrated that TNT templates were efficiently imprinted into the matrix of silica through the strong acid-base pairing interaction between TNT and 3-aminopropyltriethoxysilane (APTS). TNT-imprinted silica nanotubes were synthesized by the gelation reaction between APTS and tetraethylorthosilicate (TEOS), selectively occurring at the porous walls of APTS-modified alumina membranes. The removal of the original TNT templates leaves the imprinted cavities with covalently anchored amine groups at the cavity walls. A high density of recognition sites with molecular selectivity to the TNT analyte was created at the wall of silica nanotubes. Furthermore, most of these recognition sites are situated at the inside and outside surfaces of tubular walls and in the proximity of the two surfaces due to the ultrathin wall thickness of only 15 nm, providing a better site accessibility and lower mass-transfer resistance. Therefore, greater capacity and faster kinetics of uptaking target species were achieved. The silica nanotube reported herein is an ideal form of material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.