Novel Process For Fabrication Research Articles

Removal of trivalent and pentavalent arsenic from water using chemically modified chitosan beads

A novel process for chemical modification of chitosan with iron oxide and potassium permanganate was developed and the beads of the modified material have been prepared for the removal of the two forms of the metalloid Arsenic - As(III) and As(V)from water in the concentration range 5-40 mg L -1 . The maximum adsorption capacity ( p H 7.0) is 43.28 and 32.26 mg g -1 for As(III) and As(V), respectively. The chemically modified chitosan beads are regenerated for successive treatment cycles through alkali treatment. The regenerated beads show negligible loss in their removal efficiency of As(III) and As(V). Overall, the study provides a novel process for fabrication of low-cost composite material of chitosan for enhanced removal of Arsenic. This report will facilitate the development and up-scaling of low-cost treatment technologies for adsorptive removal of Arsenic from water.

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

A novel, Ti-6Al-4V (Ti64)/Hydroxyapatite (HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion (EPBF) additive manufacturing (AM): specifically, the commercial electron beam melting (EBM®) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell (model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm3, and corresponding Young’s moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ∼3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography (OM) and scanning electron microscopy (SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha (hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ∼5 μm in the EPBF-fabricated Ti64 to ∼1.1 μm for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 μm. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors’ knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.

Fabrication of nano-sized copper powders in liquid media via high-energy electrical explosion method: Use of high purity copper recovered from waste jelly-filled cable as raw material

Abstract A novel process for fabrication of nano-sized copper powders in organic oleic acid medium was developed employing a high-energy electrical explosion method. Formation of copper oxides was inhibited by the oleic acid medium during the electrical explosion of copper wires recovered from waste jelly-filled cable as a raw material for synthesis of nano-colloids and final dried nano-sized copper powders. High voltage of 320 V was repeatedly applied between the two horizontal electrodes for 3000 electrical explosions across the horizontal electrodes assembly. The copper powders were finally recovered via dispersion of the colloid by ultra-sonification and subsequent drying in an oven at 60 °C for 1 h and 5 h, respectively. The copper powders thus fabricated were analyzed using FESEM, BET surface area analyzer, TEM and elemental analyzer for determination of morphology, porosity and elemental purity. All of them turned out to be superior compared to similarly produced copper nano-sized powders in deionized water or ethyl alcohol (EtOH) media.

Fabrication of silk fibroin film using centrifugal casting technique for corneal tissue engineering.

Films prepared from silk fibroin have shown potential as biomaterials in tissue engineering applications for the eye. Here, we present a novel process for fabrication of silk fibroin films for corneal application. In this work, fabrication of silk fibroin films was simply achieved by centrifugal force. In contrast to the conventional dry casting method, we carried out the new process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force was imposed on an aluminum tube containing silk fibroin solution. In the present study, we also compared the surface roughness, mechanical properties, transparency, and cell proliferation between centrifugal and dry casting method. In terms of surface morphology, films fabricated by the centrifugal casting have less surface roughness than those by the dry casting. For elasticity and transparency, silk fibroin films obtained from the centrifugal casting had favorable results compared with those prepared by dry casting. Furthermore, primary human corneal keratocytes grew better in films prepared by the centrifugal casting. Therefore, our results suggest that this new fabrication process for silk fibroin films offers important potential benefits for corneal tissue regeneration.

Nanochannel diodes based on InAs/Al80Ga20Sb heterostructures: Fabrication and zero-bias detector properties

The authors present a novel process for fabrication of deep submicron isolation patterns in InAs/Al80Ga20Sb heterostructures. The process is demonstrated by processing InAs/Al80Ga20Sb self-switching diodes (SSDs). SSDs require high-resolution isolation patterns, which presents a major fabrication challenge because of the oxidation sensitivity of Al(Ga)Sb alloys. The presented fabrication process completely avoided exposure of Al(Ga)Sb to air and resulted in an isolation pattern with a feature size down to 35 nm. The process was based on a dry etch of isolating trenches, in situ removal of the resist etch mask followed by in situ encapsulation of etched surfaces by silicon nitride. The applicability of the InAs/Al80Ga20Sb SSD process was demonstrated with on-wafer RF measurements of zero-bias detection up to 315 GHz. Below 50 GHz, the detector's noise-equivalent power was estimated to less than 100 pW/Hz½.

A Novel Process for the Fabrication of a Silver‐Nanoparticle‐Modified Electrode and Its Application in Nonenzymatic Glucose Sensing

AbstractIn this work, we present a novel process for fabrication of a silver‐nanoparticle‐modified electrode using silver ion implantation. This method is facile, low‐cost and environmental friendly without the use of any other chemicals. The obtained AgNPs on the electrode surface, which were free from any reagents surrounding or binding to them, showed prominent electrocatalytic activity towards the oxidation of glucose, leading to a nonenzymatic glucose sensor with a wide linear range and a detection limit of 0.5 µM. In addition, the modified electrode also exhibited acceptable reproducibility and long‐term stability.

Synthesis of Biomimetic Superhydrophobic Surface through Electrochemical Deposition on Porous Alumina

The superhydrophobicity of plant leaves is a benefit of the hierarchical structures of their surfaces. These structures have been imitated in the creation of synthetic surfaces. In this paper, a novel process for fabrication of biomimetic hierarchical structures by electrochemical deposition of a metal on porous alumina is described. An aluminum specimen was anodically oxidized to obtain a porous alumina template, which was used as an electrode to fabricate a surface with micro structures through electrochemical deposition of a metal such as nickel and copper after the enlargement of pores. Astonishingly, a hierarchical structure with nanometer pillars and micrometer clusters was synthesized in the pores of the template. The nanometer pillars were determined by the nanometer pores. The formation of micrometer clusters was related to the thin walls of the pores and the crystallization of the metal on a flat surface. From the as-prepared biomimetic surfaces, lotus-leaf-like superhydrophobic surfaces with nickel and copper deposition were achieved.

Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers

We demonstrate a novel process for fabrication of GaAs based self-aligned lasers based upon a single overgrowth. A lattice matched n-doped InGaP layer is utilized for both electrical and optical confinement. We present operating characteristics such as external differential quantum efficiency, T-zero and far field as a function of stripe width.

Quantum Well and Dot Self-Aligned Stripe Lasers Utilizing an InGaP Optoelectronic Confinement Layer

We demonstrate and study a novel process for fabrication of GaAs-based self-aligned lasers based upon a single overgrowth. A lattice-matched n-doped InGaP layer is utilized for both electrical and optical confinements. Single-lateral-mode emission is demonstrated initially from an In0.17Ga0.83As double quantum well laser emitting ~980 nm. We then apply the fabrication technique to a quantum dot laser emitting ~1300 nm. Furthermore, we analyze the breakdown mechanism in our devices and discuss the limitations of index guiding in our structures.

A Novel Process for Fabrication of Globular Structure by Equal Channel Angular Pressing and Isothermal Treatment of Semisolid Metal

A new process for fabrication of semisolid billets is introduced, which involves equal channel angular pressing and isothermal heating in the semisolid state. The process leads to a relatively fine globular microstructure. The microstructure evolution during isothermal treatment is studied and it is shown that dendrites breaking up has happened during equal channel angular pressing in semisolid state. The microstructural evolution during isothermal heating and the mechanism for the formation of the globular structure is tried to be understood and also modeled.

Fabrication of ultra high aspect ratio Bragg gratings for optical filter

In this paper a novel process for fabrication of high finesse and large spectral range integrated optics filtering structure for optical communication applications is presented. The technology approach used in the fabrication make use of glass-on-silicon substrates and comprise deep submicron ultra-high aspect ratio Bragg gratings which are deeply buried into the waveguide glass materials.

A novel process for fabrication of SnO 2-based thick film gas sensors

A centrifugal coating technique has been developed for SnO 2 thick film gas sensors. The thickness of the films was controlled by changing the concentration of the SnO 2 suspension. For thicknesses above 10 μm, the sensitivity was stabilized. A cold isostatic pressing of the films before sintering resulted in a slight reduction of the sensitivity and a considerable reduction in resistivity, showing the applicability of the process. Centrifugally coated samples showed a much higher sensitivity than screen-printed samples. This result was attributed to the stacking of fine powder at the surface which showed a lower resistivity and a higher sensitivity compared to coarse powder.

Design and prototyping of Stark atom chip for electric trapping of laser-cooled atoms

An electric trapping of laser-cooled neutral strontium (Sr) atoms on a chip with micro-electrodes has been successful. The device is called “Stark atom chip” since it makes use of Stark effects on neutral atoms in electric fields. In this paper, our design and prototyping of the Stark atom chip with high aspect ratio electrodes precisely built on a surface are described. The functional requirements of the chip are specified during the discussion of designing the device. The authors design a novel process for fabrication of high aspect ratio electrodes. A focused ion beam (FIB) is used for precision fabrication of the prototype.

A Novel Process for Fabrication of Gated Silicon Field Emitter Array Taking Advantage of Ion Bombardment Retarded Etching

A novel process for the fabrication of a gated silicon field emitter array is proposed. The process involves complete self-alignment of gate electrodes taking advantage of ion bombardment retarded etching. The ion-irradiated regions serve as masks for subsequent silicon etching resulting in the formation of tabletop structures. The structures are suitable for both the formation of pyramidal emitters and the arrangement of gate electrodes adjacent to each emitter. We integrate this silicon etching into a self-align process for the fabrication of gated emitter array. The emission characteristics of 100 emitters are tested, and the emission at a gate voltage of 30 V is detected. The results indicate that the proposed process is applicable to the fabrication of gated silicon emitters.

Fabrication and Characteristics of Ordered Ni Nanostructures on Glass by Anodization and Direct Current Electrodeposition

A novel process for fabrication of metal nanostructure arrays directly on glass substrates is described. An aluminum film was sputter-deposited on a glass substrate coated with a tin-doped indium oxide (ITO) film. The films were then anodically oxidized to obtain a porous alumina template, with pore diameters ranging from 5 to 150 nm, which was used as a template-electrode in a direct current electrodeposition to fabricate various nickel nanowires (⌀ 18−180 nm, 0.5−2.6 μm long) in the nanopores. The porous alumina films not only define the dimensions of the nanowires but also influence the crystalline orientation. The magnetic hysteresis measurement showed that the Ni nanowire arrays have significant magnetic anisotropy proportional to their aspect ratios. The coercivity (Hc) and the squareness (Mr/Ms) perpendicular to the substrates were 1025 Oe and 0.74 for the Ni nanowires of ⌀ 50 nm (1.8 μm), and 830 Oe and 0.94 for the Ni nanowires of ⌀ 18 nm (1.2 μm), respectively.

Channel‐Constrained Electroless Metal Deposition on Ligating Self‐Assembled Film Surfaces

Channel‐constrained metallization is described as a novel process for fabrication of metal features useful as etchmasks and electrical interconnects in microelectronics applications. The method creates a requisite surface reactivity template through patterned exposure and development of photoresist films to open channels to an underlying ligand self‐assembled film. Subsequent electroless metal deposition occurs selectively at exposed ligand sites in the channels, which constrain lateral metal growth detrimental to feature critical dimension (CD) control during plating. A characterization of the individual process steps is presented using a positive tone photoresist system as an example. Determination of the exposure and development conditions that promote clearance of photoresist residues from the channels while maintaining adequate feature CD control is identified as an important issue in successfully performing the process. The process has been successfully demonstrated using optical exposure sources and is compatible with a range of substrates relevant for electronics applications, including Si. The high plasma etching selectivity of a thin Ni metal masking layer was used in the fabrication of high aspect ratio structures (≤5:1) in Si. © 1999 The Electrochemical Society. All rights reserved.

Single crystal silicon supported thin film micromirrors for optical applications

A novel process for fabrication of single crystal silicon sup- ported torsional micromirrors with large dimensions (300 3 240 mm) is presented. The mirrors consist of a sputtered aluminum film on a layer of supporting oxide mounted on fully suspended single crystal silicon grids. The grids have an aspect ratio of 7:1 to provide a stiff backbone and to ensure flatness of the mirror surface. Thus the mirrors do not bend due to the internal stresses. A new idea of actuation of torsional structures is also presented. Vertical near-comb type actuators were fabricated to drive the torsional structures. © 1997 Society of Photo-Optical Instrumentation En- gineers. (S0091-3286(97)01405-0)