Critical review of off-axial nozzle and coaxial nozzle for powder metal deposition

2021 ◽  
Author(s):  
S. Pratheesh Kumar ◽  
S. Elangovan ◽  
R. Mohanraj ◽  
B. Srihari
Keyword(s):  
Critical Review ◽  
Metal Deposition ◽  
Powder Metal ◽  
Coaxial Nozzle

POWDER BEAM ANALYSIS OF LASER METAL DEPOSITION COAXIAL NOZZLE VIA IMAGE PROCESSING

2019 ◽  
Author(s):  
Doglas Negri ◽  
Gustavo Reis de Ascencao ◽  
Saulo Melotti ◽  
Jhonattan Gutjahr
Keyword(s):  
Image Processing ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Coaxial Nozzle ◽  
Beam Analysis

Experimental and Numerical Analysis of the Powder Flow in a Multi-Channel Coaxial Nozzle of a Direct Metal Deposition System

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Piyush Pant ◽  
Dipankar Chatterjee ◽  
Sudip Kumar Samanta ◽  
Aditya Kumar Lohar
Keyword(s):  
Gas Flow ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Deposition Process ◽  
Metal Deposition ◽  
Direct Metal Deposition ◽  
Powder Flow ◽  
Coaxial Nozzle ◽  
Proposed Model ◽  
Blown Powder

Abstract The work explores the powder transport process, using numerical simulation to address the dynamics of the powder flow in an in-house built multi-channel coaxial nozzle of a direct metal deposition (DMD) system. The fluid turbulence is handled by the standard k–ɛ and k–ω turbulence models, and the results are compared in order to predict their suitability. An image-based technique using CMOS camera is adopted to determine the powder flow characteristics. The model is validated with the in-house experimental results and verified available results in the literature. The findings of this work confirms the application of the k–ω model for powder gas flow investigations in blown powder additive manufacturing (AM) processes due to its better predictive capability. The proposed model will assist in simulating the direct metal deposition process.

The Investigation of Gravity-Driven Metal Powder Flow in Coaxial Nozzle for Laser-Aided Direct Metal Deposition Process

2005 ◽  
Vol 128 (2) ◽  
pp. 541-553 ◽  
Author(s):  
Heng Pan ◽  
Todd Sparks ◽  
Yogesh D. Thakar ◽  
Frank Liou
Keyword(s):  
Gas Flow ◽  
Particle Concentration ◽  
Metal Deposition ◽  
Direct Metal Deposition ◽  
Powder Flow ◽  
Shielding Gas ◽  
Two Phase ◽  
Coaxial Nozzle ◽  
Gravity Driven ◽  
Nozzle Geometries

The quality and efficiency of laser-aided direct metal deposition largely depends on the powder stream structure below the nozzle. Numerical modeling of the powder concentration distribution is complex due to the complex phenomena involved in the two-phase turbulence flow. In this paper, the gravity-driven powder flow is studied along with powder properties, nozzle geometries, and shielding gas settings. A 3-D numerical model is introduced to quantitatively predict the powder stream concentration variation in order to facilitate coaxial nozzle design optimizations. Effects of outer shielding gas directions, inner/outer shielding gas flow rate, powder passage directions, and opening width on the structure of the powder stream are systematically studied. An experimental setup is designed to quantitatively measure the particle concentration directly for this process. The numerical simulation results are compared with the experimental data using prototyped coaxial nozzles. The results are found to match and then validate the simulation. This study shows that the particle concentration mode is influenced significantly by nozzle geometries and gas settings.

Temperature distribution of gas powder jet formed by coaxial nozzle in laser metal deposition

2018 ◽  
Author(s):  
Yuri N. Zavalov ◽  
Vladimir D. Dubrov ◽  
Elena S. Makarova ◽  
Nikolay G. Dubrovin ◽  
Fikret K. Mirzade ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Coaxial Nozzle

Chemical modification of the bacterial wall to determine sites of metal deposition

1978 ◽  
Vol 36 (2) ◽  
pp. 350-351
Author(s):  
T. J. Beveridge
Keyword(s):  
Electron Scattering ◽  
Metal Salt ◽  
Metal Deposition ◽  
Suitable Model ◽  
X Ray Diffraction ◽  
Subtilis Cell ◽  
Thin Sections ◽  
X Ray ◽  
Section Data ◽  
Metal Impregnation

The Bacillus subtilis cell wall provides a protective sacculus about the vital constituents of the bacterium and consists of a collection of anionic hetero- and homopolymers which are mainly polysaccharidic. We recently demonstrated that unfixed walls were able to trap and retain substantial amounts of metal when suspended in aqueous metal salt solutions. These walls were briefly mixed with low concentration metal solutions (5mM for 10 min at 22°C), were well washed with deionized distilled water, and the quantity of metal uptake (atomic absorption and X-ray fluorescence), the type of staining response (electron scattering profile of thin-sections), and the crystallinity of the deposition product (X-ray diffraction of embedded specimens) determined.Since most biological material possesses little electron scattering ability electron microscopists have been forced to depend on heavy metal impregnation of the specimen before obtaining thin-section data. Our experience with these walls suggested that they may provide a suitable model system with which to study the sites of reaction for this metal deposition.

SEM of non-coated hepatocellular cytoskeleton of perfused livers

1984 ◽  
Vol 42 ◽  
pp. 306-307
Author(s):  
S.W. French ◽  
N.C. Benson ◽  
C. Davis-Scibienski
Keyword(s):  
Ambient Temperature ◽  
Critical Point ◽  
Protease Inhibitors ◽  
Metal Deposition ◽  
Heat Damage ◽  
Detergent Extraction ◽  
Cytoskeletal Elements ◽  
Triton X ◽  
Excised Tissue

Previous SEM studies of liver cytoskeletal elements have encountered technical difficulties such as variable metal coating and heat damage which occurs during metal deposition. The majority of studies involving evaluation of the cell cytoskeleton have been limited to cells which could be isolated, maintained in culture as a monolayer and thus easily extracted. Detergent extraction of excised tissue by immersion has often been unsatisfactory beyond the depth of several cells. These disadvantages have been avoided in the present study. Whole C3H mouse livers were perfused in situ with 0.5% Triton X-100 in a modified Jahn's buffer including protease inhibitors. Perfusion was continued for 1 to 2 hours at ambient temperature. The liver was then perfused with a 2% buffered gluteraldehyde solution. Liver samples including spontaneous tumors were then maintained in buffered gluteraldehyde for 2 hours. Samples were processed for SEM and TEM using the modified thicarbohydrazide procedure of Malich and Wilson, cryofractured, and critical point dried (CPD). Some samples were mechanically fractured after CPD.

Semi-synthesis as a tool for broadening the health applications of bioactive olive secoiridoids: a critical review

2021 ◽  
Author(s):  
Manuela Oliverio ◽  
Monica Nardi ◽  
Maria Luisa Di Gioia ◽  
Paola Costanzo ◽  
Sonia Bonacci ◽  
...  
Keyword(s):  
Critical Review ◽  
Natural Compounds ◽  
Effective Strategy ◽  
Synthetic Analogues ◽  
Health Applications ◽  
Natural And Synthetic

Semi-synthesis is an effective strategy to obtain both natural and synthetic analogues of the olive secoiridoids, starting from easy accessible natural compounds.

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