Metal Microtubes Research Articles

Production and measurement of MeV proton microbeams in atmospheric environment based on glass capillary

<sec>Traditionally, ion microbeam is produced by focusing or/and collimating to reduce the beam size to submicron level. The traditional setup for producing the microbeam consists of an expensive focusing and collimating system with a large space, based on electromagnetic fields. Meanwhile, the microbeam obtained through pure collimation of metal micro-tubes is limited by the fabrication processing, i.e. the size of beam spot is largely limited to a few microns and its manufacture is not as simple as that of a glass capillary. Inspired by early studies of the guiding effect, the use of inexpensive and easy-to-make glass capillaries as the tool for ion external microbeam production has become a new direction.</sec><sec>In this work, we use a glass capillary with an open outlet (108 μm in diameter), which serves as a vacuum differential and collimating component, to produce a 2.5 MeV-proton microbeam directly from the linear accelerator into the atmosphere for measurements. We measure the beam spot diameter and energy distribution of the microbeam as a function of the tilt angle of the capillary. We also conduct calculations and ion trajectory analysis on the scattering process of 2.5 MeV protons on the inner walls.</sec><sec>The measurement results show that when the tilt angle is around 0°, there are a direct transmission part that maintains the initial incident energy, and a scattering part with the energy loss in the microbeam. It is found that the proportion of directly transmitted protons and the beam spot size are highest near zero tilt angle. As the tilt angle increases, the beam spot diameter decreases; when the tilt angle is greater than the geometric angle, all the microbeams come from the scattering with the energy loss. The simulation combined with the ion trajectory analysis based on the scattering process can explain the experimental results. It is found that the large angle scattering determines the entire external microbeam spot, and the central region of the beam spot is composed of directly penetrating ions, whose size is determined by the geometric shape of the glass capillary, i.e. the outlet diameter and aspect ratio.</sec><sec>The natural advantage of producing external micobeames easily and inexpensively through glass capillaries is their relative safety and stable operation, and the last but not least point is to simply locate the microbeams on the sample without complex diagnostic tools. The microbeams are expected to be widely used in fields such as radiation biology, medicine, and materials.</sec>

Asymmetric layered structural design with metal microtube conductive network for absorption-dominated electromagnetic interference shielding

Conductive polymer composites (CPCs) with high conductivity components designed based on impedance mismatch strategy have high electromagnetic interference shielding effectiveness (EMI SE) yet cause serious secondary pollution due to their strong reflection. A well-designed double-layer fiber-based waterborne polyurethane (WPU) composite with electro-magnetic asymmetric distribution for EMI shielding with absorption-dominant is realized. When the electromagnetic waves (EMWs) enter the AF@Ni/Cu/Fe3O4/WPU composite through gaps of the nonwoven fabric, incoming microwaves will undergo a special ‘absorption-reflection-reabsorption’ process between the metal microtubules, and the electromagnetic shielding effectiveness (EMI SE) of the composite reaches 55.8 dB in X-band, which indicates approximately 99.9997% of EWMs are attenuated in the propagation process. Herein, absorption (SEA, 50.1 dB) contributes 89.8% to the total SE and the lowest power coefficient of reflection (R) reaches 0.62. This work expands the application field of high-performance aramid fibers, and provides a reliable strategy to reduce secondary electromagnetic radiation pollution.

Introduction of a new method for bending of AISI 304L stainless steel micro-tubes with micro-wire mandrel

Abstract The purpose of this study is presenting a new method for bending metal micro-tubes in a critical bending ratio. At first, using the fluid pressure and bending die in the bending ratio of 1.6, the micro-tube has been bent, which is caused wrinkling on the intrados of the micro-tube. Then, using a micro-wire mandrel, a new method for micro-tube bending has been proposed. Two parameters of micro-wire clearance and micro-wire arrangements have been investigated to generalize this method. The results have shown that the clearance of micro-wire with micro-tube should not be less than 50 μm because it will not be possible to insert micro-wire into the micro-tube. Also, the arrangement that has less clearance will have less cross-section distortion because they cause more filling within the micro-tube. In general, the results have shown that micro-tube bending with micro-wire mandrel did not have defects such as wrinkling and rupture. It also allows the micro-tube to bend at room temperature in a critical bending ratio.

Review on Advances in Metal Micro-Tube Forming

Metallic tubular micro-components play an important role in a broad range of products, from industrial microsystem technology, such as medical engineering, electronics and optoelectronics, to sensor technology or microfluidics. The demand for such components is increasing, and forming processes can present a number of advantages for industrial manufacturing. These include, for example, a high productivity, enhanced shaping possibilities, applicability of a wide spectrum of materials and the possibility to produce parts with a high stiffness and strength. However, certain difficulties arise as a result of scaling down conventional tube forming processes to the microscale. These include not only the influence of the known size effects on material and friction behavior, but also constraints in the feasible miniaturization of forming tools. Extensive research work has been conducted over the past few years on micro-tube forming techniques, which deal with the development of novel and optimized processes, to counteract these restrictions. This paper reviews the relevant advances in micro-tube fabrication and shaping. A particular focus is enhancement in forming possibilities, accuracy and obtained component characteristics, presented in the reviewed research work. Furthermore, achievements in severe plastic deformation for micro-tube generation and in micro-tube testing methods are discussed.

Buckling of metallic glass supercooled liquid layer during embossing

Embossing of metallic glass supercooled liquids into templates is emerging as a precision net-shaping and surface patterning technique for metals. Here, we report the effect of thickness of metallic glass on template-based embossing. The results show that the existing embossing theory developed for thick samples fails to describe the process when the thickness of metallic glass becomes comparable to the template cavity diameter. The increased flow resistance at the cavity entrance results in viscous buckling of supercooled liquid instead of filling. A phenomenological equation is proposed to describe the thickness dependent filling of template cavities. The buckling phenomenon is analyzed based on the folding model of multilayer viscous media. We show that controlled buckling can be harnessed in the fabrication of metal microtubes, which are desirable for many emerging applications.

Nanoporous Microtubes via Oxidation and Reduction of Cu–Ni Commercial Wires

Metallic porous microtubes were obtained from commercial wires (200–250 µm diameter) of Cu-65Ni-2Fe, Cu-44Ni-1Mn and Cu-23Ni, alloys (wt. %) by surface oxidation at 1173 K in air, removal of the unoxidized core by chemical etching, and reduction in annealing in the hydrogen atmosphere. Transversal sections of the partially oxidized wires show a porous layered structure, with an external shell of CuO (about 10 μm thick) and an inner layer of NiO (70–80 μm thick). In partially oxidized Cu-44Ni-1Mn and Cu-23Ni, Cu2O is dispersed in NiO because the maximum solubility of Cu in NiO is exceeded, whereas in Cu-65Ni-2Fe, a Cu2O shell is present between CuO and NiO layers. Chemical etching removed the unoxidized metallic core and Cu2O with formation of porous oxide microtubes. Porosity increases with Cu content because of the larger amount of Cu2O in the partially oxidized wire. After reduction, the transversal sections of the metallic porous microtubes show a series of f.c.c.-(Cu,Ni) solid solutions with different compositions, due to the segregation of CuO and NiO during oxidation caused by the different diffusion coefficients of Ni and Cu in the respective oxides. Pore formation occurs at each step of the process because of the Kirkendall effect, selective phase removal and volume contraction.

Fabrication of Al microtubes by electromigration and controlled etching

Al microtubes were fabricated by electromigration and controlled etching. Samples consisted of thin Al films with slits and discharge holes near the anode. Al atoms accumulated and discharged forming a microwire, which was then etched into a hollow microtube. Al microtubes could be fabricated at predetermined positions, with their lengths dependent on the current supply duration. The outer and inner diameters of the Al microtube could be determined by controlling the size of the etched hole. This technique has potential in the fabrication of other metallic microtubes.

Heat Assisted Dieless Drawing Process of Superplastic Metal Microtubes - From Zn22Al to β Titanium Alloys

A heat assisted superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn-22Al and β titanium superplastic alloy for not only circular but also noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross sections. As a result, the tendency has been to increase the limiting reduction in area with increasing strain rate sensitivity index m value. We successfully fabricate Zn-22Al alloy, AZ31 magnesium, β titanium circular microtubes with outer diameter of 191μm, 890μm and 180μm, respectively. Furthermore, a noncircular micro tube, which has inner square tubes with a 335μm side, and an outer rectangular tube of 533×923μm were fabricated successfully. During the dieless drawing process, the geometrical similarity law in cross section which the tube is drawn while maintaining its initial shape can be satisfied. The smooth surface can be obtained in case of superplastic dieless drawing process without contact situation with dies and tools. Consequently, it is found that the superplastic dieless drawing is effective for the fabrication of circular and noncircular multicore microtubes.

Deformation Profile in Rotary Laser Dieless Drawing Process for Metal Microtubes

A novel rotary laser dieless drawing process for metal microtube with local heating using a laser irradiated from one direction is proposed. A metal microtube is rotated about a tensile axis by rotary stage with chucks for circumferential uniform temperature distribution. A tube of stainless steel SUS304 with an outer diameter of 0.5mm and thickness of 0.13mm is used in the experiments. The rotating effects on outer diameter variation and outer radius error are evaluated in laser dieless drawing. As a result, the outer diameter variation under a condition of non-rotation is higher than that under condition of rotation. Thus, the limit of stable drawing condition can be enhanced by rotating effect in laser dieless drawing. In addition, in case of laser heating irradiated from one direction under non-rotating, the deformation amount of irradiated side is larger than that of non-irradiated side in laser dieless drawing. Meanwhile, the microtube is drawn subequally under condition of rotation due to circumferential uniform temperature distribution. Thus, the distorted radial deformation can be restrained by rotating effect. From these results, the effectiveness of the proposed rotary laser dieless drawing for fabricating metal microtubes can be demonstrated experimentally.

Study of the curing mechanism of metal alkoxide liquid threads for the synthesis of metal oxide fibers or microtubes

Curing processes enabling transformation of liquid threads into solid material have gained technological importance. Our study is focusing on the comparison of curing mechanisms for metal alkoxide-derived liquid threads. We studied the mechanisms of the formation of fine metal oxide fibers or hollow microtubes by comparing the solidification of propoxide and butoxide precursors.

922 金属マイクロチューブのダイレス引抜き過程における変形挙動に及ぼす表面性状の影響

Microtube is commonly used and required. Dieless drawing is fabrication process of microtube. However, in the dieless drawing process, oxidation occurs on tube surface because of local heating and it reduces reduction in area. In this study, methods of fabrication process of non-oxide tubes and the effect of surface quality on deformation behavior in dieless drawing process for metal microtubes was investigated. Materials used are stainless SUS304 tubes and copper alloy C1220 tubes. SUS304 tubes with outer diameter of 500μm and thickness of 130μm and 100μm. C1220 tubes with outer diameter of 500μm and thickness of 130μm. As a result, argon gas atmosphere reduced oxide film on the tube surface in dieless drawing process. In case of low temperature, oxide film decreases the limiting reduction in area. On the contrary, in case of high temperature, oxide film enhances the limiting reduction in area, because surface roughness with oxide film is lower than that of non-oxide film under condition of argon gas atmosphere.

Light confinement by a cylindrical metallic waveguide in a dense buffer-gas environment

We report on the implementation of metallic microtubes in a system of rubidium vapour at 230\,bar of argon buffer gas. The high buffer gas pressure leads to a widely pressure broadened linewidth of several nanometers, interpolating between the sharp atomic physics spectra and the band structure of solid state systems. Tube-like metallic waveguide structures have been inserted in the high pressure buffer gas system, allowing for an enhancement of the atom-light interaction over an optical guiding length in the tube of up to 1\,mm. The system holds promise for nonlinear optics experiments and the study of atom-light polariton condensation.

The Nickel Micro-tubes Fabrication by Galvanic Displacement Method Using Macroporous Silicon as Template

The Nickel microtubes were fabricated using the macroporous silicon as template substrate. The metal microtubes were obtained after immersion of macroporus silicon layer into the ammonium fluoride media containing nickel ions. The results show that the efficiency of tubes formation is sensible to pH level of electrolyte solution. The best pH level was 6.5 since for other pH levels non-tubes formation was observed. These results were discussed in the sense of the galvanic displacement effect.

FE Analysis of Size Effect on Deformation Behavior of Metal Microtube Considering Surface Roughness in Flaring Test

Reliable test results that show the material characteristics of a micromaterial are necessary for the accurate analysis and design of microforming processes. The size effects in the microforming are predicted to have a significant impact on the material behavior. Two size effects are explored in metallic materials. One is the grain size effect, and the other is the feature/specimen size effect. In this study, the feature size effect on the smoothing process with the consideration of tool surface roughness is investigated numerically for metal microtubes by the flaring test. Stainless-steel (SUS 316L) microtubes with the same outer diameter of 500 μm and different wall thicknesses of 50, 25 and 10 μm were used in the FE analysis to study the feature size effect on the microscale by the flaring test. The surface roughnesses of the inner and outer surfaces of the microtube, as well as the surface asperity of the conical tool, were modeled in the cyclic concave-convex configuration. It is found, in the flaring test with using rough and fine tools, that the smoothing process on the inner surface of the microtube (ISM), as well as the plastic strain in the wall thickness of microtube, is affected owing to the rigidity of the microtube, which decreases as the wall thickness of the microtube decreases. These results suggest that the feature size affects the flaring test results for the metal microtube.

Fabrication of Metallic Microtubes Using Self-Rolled Polymer Tubes as Templates

We present a novel approach for fabricating single and bimetallic (gold, titanium) (Au, Ti, Au/Ti) microtubes with very high aspect ratio from self-rolled polymer templates. The polymer microtubes used as the template were generated by self-rolling of thin polymer bilayer films (polystyrene/poly(4-vinylpyridine) (PS/P4VP) gradually released from a solid substrate. The self-rolling was introduced in the polymer bilayer by swelling the bottom P4VP layer in dodecylbenzenesulfonic acid (DBSA) solution, which was opposed by a stiff top PS layer. The inner wall of the tube was metallized by depositing a thin layer of desired metal on top of the bilayer by physical vapor deposition. The polymer template was then removed by pyrolysis, resulting in pure metal microtubes, which were characterized by optical microscopy, scanning electron microscopy (SEM), infrared spectroscopy (IR), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The tube diameter was tailored by changing the metal layer thickness on the polymer bilayer. The approach described here is general and could be used to fabricate any type of single or multimetallic tube. The metal microtubes reported in this method have potential application in drug delivery systems, microelectronics, microfluidic devices, enzyme bireaction, and chemical and biochemical sensing devices.

Effect of tool surface topography on interfacial deformation behaviour of metal microtubes in flaring test

In this study, the effect of the surface roughness of a conical tool on the surface characteristics of the micro-tube in the flaring test was investigated experimentally and numerically. The tube used is stainless steel (SUS 316L) of 500 µm diameter and 50 µm thickness. All surface asperities of the micro-tube and the conical tool were modelled as cyclic concave-convex configurations. From numerical and experimental results, it was found that the surface topographies of both the micro-tube and the conical tool are significantly important factors affecting the final surface quality of the micro-tube.

Tribological Behavior and Surface Characteristics of Metal Microtube in Flaring Test

In this study, the effect of tool asperity and the lubrication condition on tribological behavior, inner surface characteristics and deformation limit of metallic microtube in flaring test were investigated experimentally. The microtube used in this experiment is stainless steel (SUS 316L) and has a 500 μm outer diameter and 50 μm thickness. The flaring tests of the microtube using a conical tool were conducted under dry and two kinds of lubricated-contact conditions as well as different tool surface roughnesses. As a result, it is found that the flaring load and deformation limit of the microtube increase when using a rougher tool. In addition, a spray-type fluorocarbon resin, as a solid lubricant, decreases the above characteristics, but lubrication oil, as a liquid lubricant, exhibits different behavior. Meanwhile, the surface roughnesses of the inner surface of the microtube along axial and circumferential directions reduce when using a rougher tool. From these results, the surface smoothing mechanism of the microtube in the flaring test and the influencing parameters on tribological behavior are discussed.

Laser-induced Growth of Square Hollow Microtubes on Vanadium Metal

Recently, the preparation of metallic oxide microtubes using laser radiation on vanadium metal was reported by Nanai and George [1]. They found that the surface area of the microtubes is more than 1000 times larger than that of vanadium oxide powders used in industry. Given the importance of vanadium oxides as catalysts and functional ceramics, these vanadium oxide microtubes with a larger surface area prepared by laser radiation might lead to new kinds of catalysts. However, the growth mechanism of the microtubes has not been discussed and this is the subject of the present work. Our experiments indicate that the crystals may be vanadium oxides with less than 30 wt % oxygen, probably covered with a thin layer of V2O5. The growth resembles a typical VLS (vapor±liquid±solid) growth mechanism as described by Wagner and Ellis [2]. A vanadium metal sheet (purity: 99.9%, 3 mm thick) was irradiated by a Coherent=725 continuouswave CO2 laser in air. The power of the laser beam was measured to be less than 100 W with a beam size of about 2 mm diameter focused by mirror optics. Exposure times of the laser beam on the vanadium sheet were less than 60 s. The microstructure of the irradiated specimen was investigated by scanning electron microscopy (Philips XL20 SEM). A vigorous burning of the vanadium was found when the power was higher than 50 W. For a power lower than 10 W, the modi®cation process of surface structures by the laser beam was slow. Therefore, all experimental results presented here were performed using a power between 20 and 50 W with exposure times from 10 to 25 s. Hollow microtubes on the surface, as reported by Nanai and George [1], can be observed in Fig. 1 using a power of 30 W and an exposure time of 15 s. The tubes have a square cross-section with a width of about 7 im, the wall thickness being about 0.5 im. The length of the tubes is about 50 im.

Fabrication of metal microtubes using particle track membranes processing

It is proposed to prepare metal microtubes as replicated pores of particle track membranes (PTM) using photoetching for removing the polymer matrix without any chemical etching. Metal sputtered PTM was irradiated by a high intensity deuterium lamp with a window made of MgF 2. Aluminium microtubes 1.8 μm in external diameter and 8 μm long were fabricated for the illustration of the proposed method. Microtubes of such type are considered from the viewpoint of design and performance of the structurally inhomogeneous diffraction filters for laboratory applications.

Atomic emission spectrometry of sodium with electrothermal metal microtube

Atomic emission spectrometry with an electrothermal molybdenum microtube has been investigated for sodium. The highest atomic emission signal was observed in pure argon atmosphere. Detection limit of sodium was 1.1 pg. The method was applied to the determination of sodium in biological samples.