Stainless Steel Micro Research Articles

Verification of a Finite Element Simulation of the Progressive Collapse of Micro Lattice Structures

Stainless steel micro lattice structures, manufactured by selective laser melting, have the potential to be used as core materials in twin skinned structures. The configuration considered here is body centred cubic. One of the major structural performance requirements for such twin skinned structures is foreign object impact. The paper describes the series of steps taken to simulate (using DYNA) and validate the low velocity foreign object impact behaviour of twin skinned panels with micro lattice cores. This includes the validation of a three beam model for each micro strut, the modelling of node behaviour, and the modelling and validation of compressed micro lattice blocks, and of full foreign object impact panel behaviour.

Preparation and characterization of micro components fabricated by micro powder injection molding

Abstract Given the dimension of the micro component to be replicated, it is crucial to study sintering for dimensional and property control in micro powder injection molding. In the paper, 316 L stainless steel micro components with two different microsize structure dimensions, ϕ100 μm × height 200 μm and ϕ60 μm × height 191 μm, are fabricated from in-house feedstock. Shrinkage, microstructure, microindentation hardness and sintering trajectory are investigated for the micro components. The linear shrinkage rate of the micro component reaches the maximum at 1180 °C, after which it begins to decline. Porosity (volume fraction of pores) decrease, pore migration and breakaway, grain growth and the formation of a dense layer are observed for the microsize structures. The microindentation hardness of the dense layer in the rim of the microsize structures is lower than the microindentation hardness of the substructure. It is found that if the relative density is below 0.98, densification is promoted when the structure size reduces from the substructure in the millimeter regime to the microsize structures of ϕ60 μm. This is attributed to the oxides on the debound micro components and internal gas pressure produced by hydrogen sintering.

Microstructure evolution of 316L stainless steel micro components prepared by micro powder injection molding

Fabrication of micro components comprising of functional units of different dimensional order, ϕ100 μm, ϕ80 μm and ϕ60 μm, by micro powder injection molding is described in the paper. The microstructure is characterized for various microsize structures and substructures under different sintering conditions. The micro components are successfully molded, debound and sintered based on an in-house feedstock. Although sintered as an integral component, the microsize structure is at final stage sintering whereas the substructure is at intermediate stage sintering within the temperatures studied. The smallest microsize structures, ϕ60 μm, have the highest relative density. Higher surface area/volume ratio of the microsize structures is attributed to the advanced sintering. XPS results show that oxides on the debound micro components and consequent reduction products during hydrogen sintering attribute to the formation and progression of the observed dense layers.

The effect of H2S on the selectivity of light alkenes in the FE-Mn-catalyzed Fischer-Tropsch synthesis

Iron-manganese oxides are prepared using a co-precipitation procedure and studied for the conversion of synthesis gas to light olefins. In particular, the effect of a range of preparation variables is investigated in details. In this investigation, sulfur absorption and effect of sulfur poisoning on Fe-Mn catalysts have been studied. In the Fischer-Tropsch synthesis process, the poisoning of the catalyst is one of the important parameters causing a decrease in the catalyst activity, declaring the sulfur compounds as virulent poisons in this process. In the present investigation, poisoning of Fe-Mn catalysts were performed in a gas circulation system and H2S was injected into a circulation loop. The prepared catalysts were exposed to a mixture of H2S and N2 at about 450°C in the stainless-steel micro reactor via co-precipitation method. H2S was produced by addition of H2SO4 to Na2S × H2O and this gas was mixed with an inert carrier gas (N2). Comparing the activity and selectivity of fresh and poisoned catalysts, indicates that the selectivity and CO conversion are affected by high-level sulfur adsorbed on the catalysts. The results show that the CO conversion and selectivity with respect to methane production and coke formation were decreased, but the selectivity of light alkenes such as propylene was increased over poisoned catalysts. Characterization of both precursors and calcined catalysts by powder X-ray diffraction, BET specific surface area and thermal analysis methods such as TGA and DSC showed that the poisoning of Fe-Mn catalysts influenced the catalyst structure.

Fabrication of 316-L stainless steel micro components using encapsulating soft mould and isopressing technique

This paper presents in detail a new method to fabricate free standing 316-L stainless steel micro components using high solid loading stainless steel semi solid paste encapsulated into soft mould (PDMS) and pressed using hydrostatic pressure. The process is divided into five parts: (i) production of SU-8 master moulds and their negative replicas from soft moulds, (ii) preparation of stainless steel semi solid paste with high solid loading and filling the soft mould insert, (iii) the soft mould is sealed well and put under hydrostatic pressure, (iv) after the pressure is released the soft mould seal is removed and the paste is left to dry, (v) the green parts are obtained, de-bound, and sintered in vacuum at 1350 °C. The effect of the applied hydrostatic pressure on both the green and sintered densities as well as the linear shrinkage of the micro components was investigated in detail and compared with the pressure-less filling method. It is found that both the green and sintered densities increase while the linear shrinkage decreases with the increase of applied hydrostatic pressure. The maximum sintered density and its corresponding linear shrinkage were found to be 98.6% and 13%, respectively.

Development of WC-Co/SUS304 Functionally Graded Materials by Using Three Dimensional Micro Welding

Three dimensional micro welding (3DMW) of a novel freeform fabrication process for metal or alloy components has been developed in our investigation group. A tungsten inert gas (TIG) welding machine is controlled by utilizing CAD/CAM processes. Various types of metal or alloy wires are fed automatically under a micro-arc torch to form tiny metallic beads. These micrometer order beads are joined continuously to build three dimensional structures. Near-net-shape components of metal or alloy compounds with high melting points can be fabricated automatically with minimized energy and resources. In this study, tungsten carbide-cobalt (WC-Co) and stainless steel (SUS304) micro beads of 1.0 mm in diameter were stacked alternately to fabricate cutting tools with graded structures by using the 3DMW. The microstructure and hardness were observed by scanning electron microscope (SEM), energy dispersive spectra (EDS) and Vickers hardness tester. The maximum hardness of micro bead was approximately 1300 HV and no crack or pore existed in the formed objects.

Micro fabrication of stainless steel micro components using soft moulding and aqueous slurry

Presented is a fabrication process of stainless steel micro components. The fabrication process is divided into two main parts. In the first part, high quality SU-8 master moulds and their negative replicas from soft moulds are produced using photolithography and soft moulding techniques, respectively. The second part includes preparation of stainless steel slurry, filling the soft mould, obtaining the green parts, de-binding and sintering to the finial parts. The metallic slurry is investigated in details and the optimum dispersant and binder are obtained. Two different sintering conditions are investigated, vacuum and forming gas atmospheres. The effect of sintering atmospheres and temperatures on both density and linear shrinkage of the micro components are studied in details. The results show high quality micro components the same quality as the master moulds. The maximum sintered density and linear shrinkage are obtained when the samples are sintered in vacuum at 1350 °C and found to be 98.1% and 17.97%, respectively. The surface roughness of the sintered micro components is also investigated.

Pyrolysis of mixed plastics for the recovery of useful products

Thermal and catalytic pyrolysis of polystyrene (PS) with low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), poly-ethylene terephthalate (PET) plastics were carried out in a 25 cm 3 stainless steel micro reactor at around 430–440 °C under 5.5–6.0 MPa of N 2 gas pressure for 1 h. Three reactions of each plastic with PS were conducted in the ratio of 1:1, 1:2 and 1:3. The amount of PS was varied to explore its role and reactivity. In all coprocessing reactions, ratio 1:1 afforded the best yields in the form pyrolytic oils. SIM distillation of hexane soluble portion showed that the low boiling fractions were not found and fractions were obtained only after 96 °C + boiling point. It could be due to the vaporization of high volatile components. In most of the binary pyrolysis, light cycle oil (LCO) fractions have low recovery than heavy cycle oil (HCO). GC identified some very important chemical compounds present in the liquid products obtained from the pyrolysis of mixed plastics. The results obtained from this study have shown usefulness and feasibility of the pyrolysis process of the mixed plastics as an alternative approach to feedstock recycling.

Net shape fabrication of stainless-steel micro machine components from metallic powder

A fabrication process of the net shape 316-L stainless-steel micro machine components is reported. The fabrication process combines softlithography and powder metallurgy to produce microcomponents of complex geometries of high quality. The process starts with softlithography by producing ultra thick SU-8 master moulds and their negative replicas of polydimethylsiloxane (PDMS). Then stainless-steel slurry is prepared by mixing super fine 316-L steel powder and binder to fill the PDMS moulds. The two binders used in the experiments were Duramax D-3005 and a mixture of B1000 and B1007. The PDMS micro moulds are filled with the metallic slurries and green parts are obtained from de-moulding, before going through de-binding and sintering in forming gas atmosphere. The fabrication steps were repeatedly tested. The resultant micro parts show high quality shape retention which is attributed to the quality of the SU-8 master moulds. The hardness property of the sintered microcomponents was tested with a micro indenter and a 200 g load was applied. The Vickers hardness of the sintered components was found to be about 255, which was higher than 225 of annealed 316L stainless steel and the two binders make little difference on the hardness of the sintered samples.

Fabrication of 316-L stainless steel micro parts by softlithography and powder metallurgy

This paper presents an approach to fabricate 316-L stainless steel micro parts with complex shapes using soft lithographical and powder metallurgical techniques. The process includes production of high quality deep micro SU-8 master moulds and their negative replicas in polydimethylsiloxane (PDMS). Then the PDMS soft moulds are filled with slurry containing superfine (< 4 um) stainless steel particles and binder. When the slurry is dry, green patterns are removed from the PDMS moulds before the patterns are de-bound and sintered in the tube furnace at 1200 in forming gas atmosphere. The resultant micro parts show high shape retention. The linear shrinkage of the sintered part is measured and found to be 17%.

Fabrication of micro gear by micro powder injection molding

Micro components made from polymers can be easily processed but they may not be suitable for all applications. One example is where good mechanical properties are required. Thus, the fabrication of micro components from non-polymeric materials such as metals and ceramics is essential. In this paper, the fabrication of 316L stainless steel micro gear by micro powder injection molding is reported. The specifications of the green micro gear were: 10 teeth, module of 0.08, outer diameter of 1 mm and a length of 1 mm. Injection molding was conducted on a conventional injection molding machine with a small screw diameter of 14 mm. The green micro gear was well replicated. The debound micro gear retained its shape and the teeth were well defined. After sintering, the shape was also retained but with some surface irregularities. The process differences between μPIM and PIM, such as the use of smaller particle size and higher mold temperature are also highlighted.

Degradation pathways of decabromodiphenyl ether during hydrothermal treatment

The hydrothermal degradation pathways of decabromodiphenyl ether during hydrothermal treatment were investigated. After an initial "Heating time", the reaction runs were carried out at constant temperature (heating to 300 degrees C and keeping temperature) and pressure (8MPa) in a SUS316 stainless steel micro autoclave filled with water. Some decomposition of decabromodiphenyl ether was observed over 200 degrees C, and it was decomposed by more than 99% after 10 min at 300 degrees C. The reactivities of bromine on para and meta substituents were relatively high, while its reactivity on ortho bromine was extremely low. The formations of polybrominated dibenzo-p-dioxins and furans (PBDD/DFs) were observed in the early stages of the reactions at around 300 degrees C. The TCDD toxicity equivalency (TCDD-EQs) of the by-products was determined based on relative potencies (REPs EC(5TCDD)) with the Dioxin-Responsive-Chemical Activated Luciferase gene eXpression (DR-CALUX) bioassays technology. These results indicated that the risk of formation of PBDD/DFs in the hydrothermal degradation of deca-BDE was low, and it would be possible to reduce the TCDD-EQs value by adding some catalyst or alkali, or extending processing time.

Characterization of metallic micro rod arrays fabricated by μMIM

In this paper, two sets of arrays of 24 × 24 316L stainless steel micro rods of ϕ100 and ϕ80 μm are replicated on ϕ15 mm substructures by injection molding, debinding and sintering through micro metal injection molding. The microstructure, shrinkage, porosity and Vickers microhardness of the micro rod and the substructure of the as-sintered micro-component are characterized. Shrinkage in the micro rod is near isotropic but is higher than the substructure on which micro rods are located. Lower porosity is also observed concomitantly on the micro rod. Similar microhardness values are measured on the polished cross-sections of the substructures on which the ϕ100 and ϕ80 μm micro rod arrays are located but differing values are measured on the cross-sections of the two micro rods.

616 ステンレス及びチタンマイクロ異形線の伸線加工(OS 塑性加工(4))

616 ステンレス及びチタンマイクロ異形線の伸線加工(OS 塑性加工(4))

Somatic sensory representation in the thalamic ventrobasal complex of the Virginia opossum.

AbstractThe present study was designed to investigate the topographic organization of somatic sensory representation in the thalamic ventrobasal complex (Vb) of the Virginia opossum. Tungsten and stainless steel micro electrodes were used to record the electrical activity of single units or single unit clusters in response to mechanical stimulation of the body surface, and the obtained data were used to construct maps of somatic sensory representation in transverse planes of the ventrobasal complex. The general pattern is similar to that found in eutherian mammals. A relatively large contralateral head and face representation is located throughout the entire anterior‐posterior extent of the ventrobasal complex, while a relatively smaller representation of contralateral trunk and limbs is located laterally only in the middle regions of the ventrobasal complex. Representations of middorsal head and trunk are located dorsally while those of limb apices are located ventrally. Activity was also recorded in the posterior nuclear region of the thalamus (Po) and in the subthalamic zona incerta (ZI), and there is a suggestion of topographic organization in these nuclear regions as well.