scholarly journals Influence of temperature and time factor on process of spraying of metallic powders in a plasma atomizer

2020 ◽  
Vol 221 ◽  
pp. 02003
Author(s):  
Sergey Ermakov ◽  
Evgeny Gyulikhandanov ◽  
Evgeny Petukhov
Keyword(s):  
Mathematical Modelling ◽  
Industrial Production ◽  
Additive Technologies ◽  
Time Factor ◽  
Chemical Compositions ◽  
Metal Powders ◽  
Spray Chamber ◽  
Commercial Products ◽  
Influence Of Temperature

The development of additive technologies is hampered by the almost complete absence of domestic systems for the production of metal powders. A prototype installation of a plasma atomizer was developed and manufactured, which makes it possible to obtain low-tonnage batches of metal powders of various chemical compositions. However, when the technology was transferred from the laboratory to production, a number of additional issues arose associated with a decrease in the quality of commercial products as the time of continuous spraying increases. It was found that the reason for this is the formation of powder deposits on the walls of the spray chamber and the increase in its temperature. Using the method of mathematical modelling, the maximum permissible temperature of the walls of the spraying chamber was determined, ways of stabilizing the quality of the powder during industrial production were shown.

scholarly journals Regulation of powder particles shape and size at plasma spraying

2021 ◽  
pp. 7-15
Author(s):  
S. B. Ermakov ◽  
Keyword(s):  
Spherical Shape ◽  
Plasma Generator ◽  
Current Strength ◽  
Additive Technologies ◽  
Chemical Compositions ◽  
Metal Powders ◽  
Gas Velocity ◽  
Technological Parameters ◽  
Powder Particles ◽  
Protective Gas

Additive technologies are among the most rapidly developing areas of modern production. To ensure the progressive movement of additive technologies development in the Russian Federation, it is necessary to provide maximum availability of additive raw materials – spherical metal powders for the domestic enterprises; however, the absence of domestic assemblies to produce such powders hampers the solution of this issue. Peter the Great St. Petersburg Polytechnic University has developed and successfully carried out industrial tests of a plasma atomization system for solid metal feedstocks of various chemical compositions. The paper presents the results of the study of the influence of some technological parameters on the granulometric size, shape, and defect structure of 12H18N9 steel and VG98 alloy powders. The paper includes the results of the research of the influence of such spraying parameters as the current strength and the plasma-forming gas velocity supplied to the plasma generator and the volume of protective gas supplied to the spray torch through the fluidized bed system nozzles located in the midsection of the atomizer spraying chamber. The study showed that by increasing the current strength and the plasma-forming gas velocity, it is possible to reduce the average size of the powder particles; and by changing the volume of the protective gas supply, it is possible to control the particle shape. The analysis of the chemical composition of the obtained powders shows that during the spraying process, there is no loss of alloying elements and the powder composition is the same as the original feedstock compositions. The paper gives the developed modes for the alloy feedstocks spraying, shows the possibility to produce metal powders with the level of the spherical shape factor of 92–96 % and minimal – not exceeding 0.5 % of powder aggregate weight – number of particles with nonmetallic inclusions, external and internal defects.

scholarly journals The influence of temperature and TMGa flow rate on the quality of p-GaN

AIP Advances ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 035109
Author(s):  
Zikun Cao ◽  
Xiaowei Wang ◽  
Degang Zhao ◽  
Feng Liang ◽  
Zongshun Liu
Keyword(s):  
Flow Rate ◽  
Influence Of Temperature

scholarly journals Porosity Analysis of Additive Manufactured Parts Using CAQ Technology

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1142
Author(s):  
Peter Pokorný ◽  
Štefan Václav ◽  
Jana Petru ◽  
Michaela Kritikos
Keyword(s):  
Manufacturing Process ◽  
Scanning Speed ◽  
Additive Technologies ◽  
Integration Time ◽  
Detector Resolution ◽  
Porosity Analysis ◽  
3D Scans ◽  
Printing Direction ◽  
Non Destructive

Components produced by additive technology are implemented in various spheres of industry, such as automotive or aerospace. This manufacturing process can lead to making highly optimized parts. There is not enough information about the quality of the parts produced by additive technologies, especially those made from metal powder. The research in this article deals with the porosity of components produced by additive technologies. The components used for the research were manufactured by the selective laser melting (SLM) method. The shape of these components is the same as the shape used for the tensile test. The investigated parts were printed with orientation in two directions, Z and XZ with respect to the machine platform. The printing strategy was “stripe”. The material used for printing of the parts was SS 316L-0407. The printing parameters were laser power of 200 W, scanning speed of 650 mm/s, and the thickness of the layer was 50 µm. A non-destructive method was used for the components’ porosity evaluation. The scanning was performed by CT machine METROTOM 1500. The radiation parameters used for getting 3D scans were voltage 180 kV, current 900 µA, detector resolution 1024 × 1024 px, voxel size 119.43 µm, number of projections 1050, and integration time 2000 ms. This entire measurement process responds to the computer aided quality (CAQ) technology. VG studio MAX 3.0 software was used to evaluate the obtained data. The porosity of the parts with Z and XZ orientation was also evaluated for parts’ thicknesses of 1, 2, and 3 mm, respectively. It has been proven by this experimental investigation that the printing direction of the part in the additive manufacturing process under question affects its porosity.

scholarly journals Assessment of Mini-Tablets Coating Uniformity as a Function of Fluid Bed Coater Inlet Conditions

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 746
Author(s):  
Magdalena Turk ◽  
Rok Šibanc ◽  
Rok Dreu ◽  
Maja Frankiewicz ◽  
Małgorzata Sznitowska
Keyword(s):  
Coating Layer ◽  
Spectrophotometric Analysis ◽  
Material Distribution ◽  
Spray Chamber ◽  
Colorimetric Analysis ◽  
Swirl Generator ◽  
Coating Uniformity ◽  
Fluid Bed ◽  
Inlet Conditions

This study concerned the quality of mini-tablets’ coating uniformity obtained by either the bottom spray chamber with a classical Wurster distributor (CW) or a swirl distributor (SW). Mini-tablets with a diameter of 2.0, 2.5, and 3.0 mm were coated with hypromellose using two different inlet air distributors as well as inlet airflow rates (130 and 156 m3/h). Tartrazine was used as a colorant in the coating layer and the coating uniformity was assessed by spectrophotometric analysis of solutions obtained after disintegration of the mini-tablets (n = 100). Higher uniformity of coating material distribution among the mini-tablets was observed in the case of SW distributor, even for the biggest mini-tablets (d = 3.0 mm), with an RSD no larger than 5.0%. Additionally, coating thickness was evaluated by colorimetric analysis (n = 1000), using a scanner method, and expressed as a hue value. A high correlation (R = 0.993) between inter-tablet variability of hue and UV-Vis results was obtained. Mini-tablets were successfully coated in a fluid bed system using both a classical Wurster distributor as well as a swirl generator. However, regardless of the mini-tablets’ diameter, better film uniformity was achieved in the case of a distributor with a swirl generator.

scholarly journals Thermodynamic Behavior of Fe-Mn and Fe-Mn-Ag Powder Mixtures during Selective Laser Melting

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 234
Author(s):  
Jakob Kraner ◽  
Jožef Medved ◽  
Matjaž Godec ◽  
Irena Paulin
Keyword(s):  
Selective Laser Melting ◽  
Manganese Oxides ◽  
Elevated Temperatures ◽  
Manganese Content ◽  
Chemical Compositions ◽  
Metal Powders ◽  
Laser Melting ◽  
Powder Mixtures ◽  
Ε Martensite ◽  
The Impact

Additive manufacturing is a form of powder metallurgy, which means the properties of the initial metal powders (chemical composition, powder morphology and size) impact the final properties of the resulting parts. A complete characterization, including thermodynamic effects and the behavior of the metal powders at elevated temperatures, is crucial when planning the manufacturing process. The analysis of the Fe-Mn and Fe-Mn-Ag powder mixtures, made from pure elemental powders, shows a high susceptibility to sintering in the temperature interval from 700 to 1000 °C. Here, numerous changes to the manganese oxides and the αMn to βMn transformation occurred. The problems of mechanically mixed powders, when using selective laser melting, were highlighted by the low flowability, which led to a less controllable process, an uncontrolled arrangement of the powder and a large percentage of burnt manganese. All this was determined from the altered chemical compositions of the produced parts. The impact of the increased manganese content on the decreased probability of the transformation from γ-austenite to ε-martensite was confirmed. The ε-martensite in the microstructure increased the hardness of the material, but at the same time, its magnetic properties reduce the usefulness for medical applications. However, the produced parts had comparable elongations to human bone.

scholarly journals Developing WHO guidelines: Time to formally include evidence from mathematical modelling studies

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1584 ◽  
Author(s):  
Matthias Egger ◽  
Leigh Johnson ◽  
Christian Althaus ◽  
Anna Schöni ◽  
Georgia Salanti ◽  
...  
Keyword(s):  
Mathematical Modelling ◽  
The Body ◽  
World Health ◽  
Who Guidelines ◽  
Problem Model ◽  
Assessment Development ◽  
Modelling Studies ◽  
Health Organization

In recent years, the number of mathematical modelling studies has increased steeply. Many of the questions addressed in these studies are relevant to the development of World Health Organization (WHO) guidelines, but modelling studies are rarely formally included as part of the body of evidence. An expert consultation hosted by WHO, a survey of modellers and users of modelling studies, and literature reviews informed the development of recommendations on when and how to incorporate the results of modelling studies into WHO guidelines. In this article, we argue that modelling studies should routinely be considered in the process of developing WHO guidelines, but particularly in the evaluation of public health programmes, long-term effectiveness or comparative effectiveness.  There should be a systematic and transparent approach to identifying relevant published models, and to commissioning new models.  We believe that the inclusion of evidence from modelling studies into the Grading of Recommendations Assessment, Development and Evaluation (GRADE) process is possible and desirable, with relatively few adaptations.  No single “one-size-fits-all” approach is appropriate to assess the quality of modelling studies. The concept of the ‘credibility’ of the model, which takes the conceptualization of the problem, model structure, input data, different dimensions of uncertainty, as well as transparency and validation into account, is more appropriate than ‘risk of bias’.

scholarly journals Preservatives Stability: Stability Study of Parabens under Different Conditions of Stress Degradation

2020 ◽  
Vol 11 (3) ◽  
pp. 4187-4194
Author(s):  
Ismail Bennani ◽  
Madiha Alami Chentoufi ◽  
Miloud El Karbane ◽  
Ibrahim Sbai El Otmani ◽  
Amine Cheikh ◽  
...  
Keyword(s):  
Extreme Values ◽  
Stability Study ◽  
Wide Field ◽  
Direct Influence ◽  
Light Conditions ◽  
Influence Of Temperature ◽  
Stress Degradation ◽  
Quality Of Products ◽  
The Stability

Preservatives are used in a wide field of application to maintain the quality of products. They are used to deal with the chemical, physical and microbiological problems and the constraints of the development of several formulations. In this work, we tested the stability of antimicrobial preservatives which are the parabens under different stress degradation conditions to evaluate their degree of effectiveness. The tested parabens were incubated in different solutions at different pH, Temperatures, light conditions, and presence or absence of sucrose in solution (create a medium similar of syrups). The HPLC was used for the assay, by a validated method for the parabens assay and the statistical analysis of the data is carried out by JMP software. The results show a direct influence of temperature and pH on the level of parabens, while the influence of light remains negligible. The increase in temperature gives a degree of immunity of parabens levels, especially with the extreme values of pH. This study is one of the first studies of forced decomposition of parabens carried out under the various conditions suggested. The results give an idea of the stability profile of the tested parabens and suggest a model of the conditions of conservation and use of these products in different domains and under different conditions.

Effects of Cellulase on the Chemical Compositions Characteristics and Microbial Community of Saline-alkali Land Alfalfa Silage

2019 ◽  
Author(s):  
Qiang Lu ◽  
Gentu Ge ◽  
Qiming Cheng ◽  
Meiling Hou ◽  
shan Yu Jia
Keyword(s):  
Microbial Community ◽  
Anaerobic Fermentation ◽  
Alpha Diversity ◽  
Chemical Compositions ◽  
Diversity Analysis ◽  
Microbial Network ◽  
Before And After ◽  
Alfalfa Silage ◽  
The Difference

Abstract Background We aim to assess the nutritional quality of alfalfa in saline-alkali and the main fermenting microorganisms acting on alfalfa in saline-alkali soils.Results In this study, We tested the nutrient composition and microbial community of Zhongmu No. 3 (salt-tolerant) alfalfa, including the nutritional fermentation quality and microbial diversity analysis of alfalfa before and after ensiling (30 days and 60 days). Then we got closely genus that related to saline-alkali soils.The validity of the microbiological data was confirmed by alpha diversity analysis. From the Microbial network, we obtained the difference of the saline-type mantle type.Conclusions we found that the silage quality of Saline-alkali alfalfa can be ensured by anaerobic fermentation with addition. The LABs that play a major role in the saline alkaline alfalfa silage are Lactobacillus, lactococcus and enterococcus.

Development of Toxic Degradation Products during Heat Sterilization of Glucose-Containing Fluids for Peritoneal Dialysis: Influence of Time and Temperature

1995 ◽  
Vol 15 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Per Kjellstrand ◽  
Evi Martinson ◽  
Anders Wieslander ◽  
Björn Holmquist
Keyword(s):  
Peritoneal Dialysis ◽  
Glucose Solution ◽  
Degradation Products ◽  
General Pattern ◽  
Low Ph ◽  
Uv Absorbance ◽  
Influence Of Temperature ◽  
In Vitro Systems

Objective Fluids for peritoneal dialysis (PD) cause cytotoxic reactions in many different in vitro systems. The low pH, the high osmolality of the fluids, and the glucose degradation products formed during heat sterilization have been considered responsible. In the present study, we investigate the influence of temperature and time during heat sterilization of PD fluids and glucose solutions on glucose degradation and cytotoxicity of the solutions. Design Ampoules containing PD-fluid or glucose solution were heated in an oil bath to predetermined F o values (combinations of time and temperature giving equal energy/bacteriallethality). Cytotoxicity of the solutions was measured as groWth inhibition of cultured L-929 fibroblasts. Glucose degradation was measured as UV absorbance at 228 and 284 nm. Results The same general pattern was seen in both PD fluid and glucose solution. Cytotoxicity decreased from 90% to 15% when the sterilization temperature was increased from 115° to 140°C and concomitantly the length of time shortened in order to maintain equal bacteriallethality. Under the same conditions, degradation products, measured as UV absorbance at 284 nm, decreased from 0.2 to 0.02. Conclusion To minimizethe development of cytotoxic breakdown products, high temperatures over short periods of time should be used to heat-sterilize PD fluids. Even as small an increase as 5°C at around 120°C will improve the quality of the solutions.

Sign in / Sign up

Export Citation Format

Share Document