scholarly journals Production of Resistors by Arc Plasma Spraying

1975 ◽  
Vol 2 (2) ◽  
pp. 135-145 ◽  
Author(s):  
R. T. Smyth ◽  
J. C. Anderson
Keyword(s):  
Particle Size ◽  
Thick Film ◽  
Plasma Spraying ◽  
Gas Flow ◽  
Substrate Surface ◽  
Powder Particle Size ◽  
Arc Plasma ◽  
Particle Size Range ◽  
Plasma Gun ◽  
Wide Range

Arc plasma spraying (APS) is an accepted method of producing coatings for many engineering applications. The wide range of materials that can be used to form the thick film coatings make this technique interesting as an alternative method of producing electrical components and circuits.The manufacturing procedure is outlined and the potential advantages of this method of making thick film resistors are listed.The effect on the physical and electrical properties of the films produced by variation of the arc plasma gun current, gas flow rate and powder particle size are reported together with the effect of varying gun/substrate distance and the topography of the substrate surface.It is shown that using a mixture of NiO and Fe3O4powders with a particle size range of 1–20μm it is possible to produce films on a glass substrate with sheet resistivities from 5–500 Ω/sq; temperature coefficients of resistance vary from +20 to −8 × 10−4per ℃, depending on resistor composition and film thickness.The results given for a 10,000 hour life test carried out at 150℃ in air show a mean charge in resistance of ~−5%.It is concluded that APS offers a viable method of producing thick film resistors and conductors on low cost substrates.

NUMERICAL SOLUTIONS OF SMOLUCHOWSKI'S EQUATIONS FOR THE COAGULATION OF UNCHARGED AEROSOLS

1965 ◽  
Vol 43 (8) ◽  
pp. 2312-2318 ◽  
Author(s):  
J. M. Beeckmans
Keyword(s):  
Particle Size ◽  
Numerical Solutions ◽  
Coagulation Factor ◽  
Dispersion Parameter ◽  
Particle Size Range ◽  
Mean Particle Size ◽  
A Value ◽  
Wide Range ◽  
Differential Sedimentation ◽  
Smoluchowski’S Equation

Smoluchowski's equations for the coagulation of uncharged aerosol particles were programmed for solution by electronic computer. Terms representing differential sedimentation, turbulence, and mean aggregate density in solid aerosols were included. The effect of heterogeneity in the particle-size distribution of the aerosols on their rate of coagulation was illustrated by means of a slip-corrected coagulation factor Fc, which assumes a value of unity in all non-turbulent homogeneous aerosols. Curves of Fc vs. σg, the geometrical standard deviation, were calculated for aerosols of various mean particle-size. The effects due to turbulence, and to differential sedimentation, were illustrated in a similar manner. It was also found that the process of coagulation gives rise to a degree of dispersion which is independent of the original dispersion parameter, and depends only slightly on the mean particle-size of the aerosol over a wide range of particle-sizes. In the particle-size range in which differential sedimentation is inappreciable, the relatively constant value of the dispersion parameter implies that heterogeneous aerosols must obey the simplified integrated form of Smoluchowski's equation, which is applicable to homogeneous aerosols. The coagulation constant exceeds that predicted by the simple theory by about 10% for liquid aerosols of 0.1 μ or less.

Plasma Spray Deposition Processes

MRS Bulletin ◽  
1988 ◽  
Vol 13 (12) ◽  
pp. 60-67 ◽  
Author(s):  
Herbert Herman
Keyword(s):  
High Temperature ◽  
Plasma Spraying ◽  
Protective Coatings ◽  
Spray Deposition ◽  
Substrate Surface ◽  
Extractive Metallurgy ◽  
Thermal Plasmas ◽  
Corrosive Media ◽  
Wide Range ◽  
Deposition Processes

The concept of plasma is central to many scientific and engineering disciplines—from the design of neon advertisement lights to fusion physics. Plasmas vary from low density, slight states of ionization (outer space) to dense, thermal plasmas (for extractive metallurgy). And plasmas are prominent in a wide range of deposition processes — from nonthermal plasma-activated processes to thermal plasmas, which have features of flames and which can spray-deposit an enormous variety of materials. The latter technique, arc plasma spraying (or simply, plasma spraying) is evolving rapidly as a way to deposit thick films (>30 μm) and also freestanding forms.This article will review the technology of plasma spraying and how various scientific disciplines are contributing to both an understanding and improvement of this complex process.The plasma gun dates back to the 1950s, when it was introduced for the deposition of alloys and ceramics. Due to its high temperature flame it was quickly discovered that plasmas could be used for depositing refractory oxides as rocket nozzle liners or to fabricate missile nose cones. In the latter technique, the oxide (e.g., zirconia-based ceramics, spinel) was sprayed onto a mandrel and the deposited material was later removed as a free-standing form.The technique's versatility has attracted considerable industrial attention. Modern high performance machinery is commonly subjected to extremes of temperature and mechanical stress, to levels beyond the capabilities of present-day materials. It is becoming increasingly common to form coatings on such material surfaces to protect against high temperature corrosive media and to enhance mechanical wear and erosion resistance. Several thousand parts within an aircraft gas turbine engine have protective coatings, many of them plasma sprayed. In fact, plasma spraying has emerged as a major means to apply a wide range of materials on diverse substrates. The process can be readily carried out in air or in environmental chambers and requires very little substrate surface preparation. The rate of deposit buildup is rapid and the costs are sufficiently low to enable widening applications for an ever increasing variety of industries.

scholarly journals A Low-Cost Current Sensor Based on Semi-Cylindrical Magnetostrictive Composite

Electronics ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1833
Author(s):  
Shaoyi Xu ◽  
Qiang Peng ◽  
Fangfang Xing ◽  
Hongyu Xue ◽  
Junwen Sun ◽  
...  
Keyword(s):  
Particle Size ◽  
Epoxy Resin ◽  
Low Cost ◽  
High Sensitivity ◽  
Current Sensor ◽  
Mass Ratio ◽  
Particle Size Range ◽  
Giant Magnetostrictive Material ◽  
Wide Range ◽  
Magnetostrictive Composites

This paper presents the design, fabrication, and characterization of a compact current sensor based on magnetostrictive composites and resistance strain gauges. Firstly, we designed three kinds of current sensors with different structures, in which the shape of the giant magnetostrictive material (GMM) was cuboid, cylindrical, and semi-cylindrical. A set of finite element method (FEM) simulations were performed to qualitatively guide the design of three prototypes of the current sensor. It was determined that the most ideal shape of the GMM was semi-cylindrical. Secondly, Terfenol-D (TD) powder and epoxy resin were mixed to prepare magnetostrictive composites. In this paper, magnetostrictive composites with different particle size ranges and mass ratio were prepared and tested. The results show that the magnetostrictive composites had the best performance when the particle size range was 149–500 μm and the mass ratio of epoxy resin to TD powder was 1:5. Finally, this paper tested the performance of the sensor. The sensitivity, repeatability, and linear working range of the sensor reached 0.104 με/A, 2.51%, and 100–900 A respectively, when only 0.31 g of TD powder was employed. This means that current measurement with low cost, high sensitivity, and wide range was realized.

scholarly journals Sensitivity of Process Parameters in Atmospheric Plasma Spray Coating

2018 ◽  
Vol 1 (1) ◽  
pp. 1-6
Author(s):  
Biswajit Kumar Swain ◽  
◽  
Soumya Sanjeeb Mohapatra ◽  
Ashutosh Pattanaik ◽  
Sumant Kumar Samal ◽  
...  
Keyword(s):  
Plasma Spraying ◽  
Process Parameters ◽  
Spray Coating ◽  
Correct Choice ◽  
Atmospheric Plasma ◽  
Spray Parameters ◽  
Substrate Roughness ◽  
Working Pressure ◽  
Plasma Gun ◽  
Wide Range

Atmospheric plasma spraying (APS) is one of the most widely used thermal spraying technique which finds a lot of applications due to its versatility of spraying a wide range of materials from metallic to nonmetallic and hence more suitable for spraying of high melting point materials like refractory ceramics material, cermets etc. In recent era,any material can be used for plasma spraying on almost any type of substrate. Process parameters are the key factor that affects the formation of microstructures, bonding of coating with substrate and mechanical strength of coating. In this paper, the process parameters and their sensitivity towards the plasma modified structural elements are discussed.The microstructure of thermally sprayed coatings, which results from the solidification and sintering of the particles, frequently contain pores, oxides and cracks. The amount and distribution of these defects, as well as other coating properties as for instance thickness, hardness and bond strength, will be defined by the selected spray parameters. Therefore, the correct choice of the spray process as well as respective parameters (particle size, particle velocity, spray distance, plasma gun power, working pressure, substrate roughness, substrate temperature and so on) is very important for the deposition of good coatings and, consequently, to enlarge the useful life in service of the components.

High-Performance Ceramic Coatings Sprayed via Novel Supersonic Plasma Spraying System

2007 ◽  
Vol 280-283 ◽  
pp. 1203-1206 ◽  
Author(s):  
Sheng Zhu ◽  
Bin Shi Xu
Keyword(s):  
Plasma Spraying ◽  
High Performance ◽  
Gas Flow ◽  
Low Cost ◽  
Ceramic Coatings ◽  
Air Plasma ◽  
Plasma Gun ◽  
Supersonic Plasma ◽  
Particle Velocities ◽  
Supersonic Plasma Jet

A novel supersonic plasma spraying system was developed with a maximum power of 80 kW and a maximum working gas flow of 6 m3/h, at which gas and particle velocities of 2400 and 600 m/s can be achieved respectively. This paper deals with novel supersonic plasma spraying system design, the structure of novel supersonic plasma gun includes a special Laval nozzle as the single anode and inner powder supply, and the mechanisms of supersonic plasma jet as well as the effects on the sprayed particles. The spraying process parameters of several ceramic powders such as Al2O3, Cr2O3, ZrO2, Cr3C2 and Co-WC were optimized. The properties and microstructure of the sprayed ceramic coatings were investigated. Nano Al2O3-TiO2 ceramic coating sprayed by using novel supersonic plasma spraying was also studied. Novel supersonic plasma spraying improves greatly ceramic coatings quality compared with conventional air plasma spraying (Metco 9M), as well as it has lower energy and gas exhaustion compared with high power supersonic plasma spraying (Plazjet), which can spray high-performance ceramic coatings at low cost.

The Effect of Powder Particle Size on the Structural and Magnetic Properties of Bonded NdFeB Magnet

2015 ◽  
Vol 1123 ◽  
pp. 88-91 ◽  
Author(s):  
Didik Aryanto ◽  
Zailani Ray ◽  
Toto Sudiro ◽  
Agus Sukarto Wismogroho ◽  
Nanang Sudrajat
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Powder Particle Size ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Ndfeb Magnet ◽  
Particle Size Range ◽  
X Ray ◽  
Diffraction Peaks ◽  
Powder Type

Commercially, NdFeB powder (type MQP-B+) with difference in particle sizes were used in this study. The powders were isotropically compressed and heat cured at 150°C for 30 minute. The samples were then magnetized and characterized by impulse magnetizer K series and permagraph MAGNET-PHYSIK Dr. Steingroever GmbH, respectively. According to the results of SEM characterization, compacted powder showed a homogeneous plate distribution. The surface morphology also indicated the presence of pores in the bonded NdFeB magnet. X-ray diffraction analysis from all samples revealed that the diffraction peaks were detected as tetragonal Nd2Fe14B-phase. There was no significant different in magnetic properties of bonded magnets with different in particle size. The optimum Br, Hcb, and (BH)max were achieved at particle size range of 150-297 mm.

EFFECT OF PLASMA SPRAYING PARAMETERS ON THE SPRAYED HYDROXYAPATITE COATING

2007 ◽  
Vol 14 (02) ◽  
pp. 179-184 ◽  
Author(s):  
AI-JUAN WANG ◽  
YU-PENG LU ◽  
CHUAN-ZHONG CHEN ◽  
RUI-XUE SUN
Keyword(s):  
Particle Size ◽  
Plasma Spraying ◽  
Flow Rate ◽  
Gas Flow ◽  
Electric Arc ◽  
Gas Flow Rate ◽  
Arc Power ◽  
Ha Coating ◽  
Spraying Parameters ◽  
Good Biocompatibility

As the most favorable technology, plasma spray has been used to produce the hydroxyapatite (HA) coatings with the desired phase, high crystallinity, adequate porosity, and good biocompatibility. The characteristics of the HA coating are affected by many variables of the fabricating process, such as the starting particle size, spraying distance, gas flow rate, and electric arc power, etc. This paper reviews the effect of the plasma spraying parameters on the morphology and microstructure of the HA coating, and introduces several typical HA coatings fabricated with different plasma spraying parameters.

Electron microscopy studies of plasma-sprayed materials

1983 ◽  
Vol 41 ◽  
pp. 70-71
Author(s):  
K.R. Subramanian ◽  
A.H. King ◽  
H. Herman
Keyword(s):  
Plasma Spraying ◽  
Substrate Surface ◽  
Flame Temperature ◽  
Ceramic Coatings ◽  
Metallic Substrates ◽  
Hot Plasma ◽  
Almost All ◽  
Plasma Sprayed ◽  
Hostile Environments ◽  
Plasma Spraying Process

Plasma spraying is a technique which is used to apply coatings to metallic substrates for a variety of purposes, including hardfacing, corrosion resistance and thermal barrier applications. Almost all of the applications of this somewhat esoteric fabrication technique involve materials in hostile environments and the integrity of the coatings is of paramount importance: the effects of process variables on such properties as adhesive strength, cohesive strength and hardness of the substrate/coating system, however, are poorly understood.Briefly, the plasma spraying process involves forming a hot plasma jet with a maximum flame temperature of approximately 20,000K and a gas velocity of about 40m/s. Into this jet the coating material is injected, in powder form, so it is heated and projected at the substrate surface. Relatively thick metallic or ceramic coatings may be speedily built up using this technique.

Microstructural characterization of laser-melted/roller-quenched dicalcium silicate

1988 ◽  
Vol 46 ◽  
pp. 582-583
Author(s):  
C. J. Chan ◽  
K. R. Venkatachari ◽  
W. M. Kriven ◽  
J. F. Young
Keyword(s):  
Particle Size ◽  
Raw Materials ◽  
Shape Change ◽  
Microstructural Characterization ◽  
Particle Size Effect ◽  
Dicalcium Silicate ◽  
Laser Melting ◽  
Uniform Size ◽  
Cell Shape Change ◽  
Wide Range

Dicalcium silicate (Ca2SiO4) is a major component of Portland cement. It has also been investigated as a potential transformation toughener alternative to zirconia. It has five polymorphs: α, α'H, α'L, β and γ. Of interest is the β-to-γ transformation on cooling at about 490°C. This transformation, accompanied by a 12% volume increase and a 4.6° unit cell shape change, is analogous to the tetragonal-to-monoclinic transformation in zirconia. Due to the processing methods used, previous studies into the particle size effect were limited by a wide range of particle size distribution. In an attempt to obtain a more uniform size, a fast quench rate involving a laser-melting/roller-quenching technique was investigated.The laser-melting/roller-quenching experiment used precompacted bars of stoichiometric γ-Ca2SiO4 powder, which were synthesized from AR grade CaCO3 and SiO2xH2O. The raw materials were mixed by conventional ceramic processing techniques, and sintered at 1450°C. The dusted γ-Ca2SiO4 powder was uniaxially pressed into 0.4 cm x 0.4 cm x 4 cm bars under 34 MPa and cold isostatically pressed under 172 MPa. The γ-Ca2SiO4 bars were melted by a 10 KW-CO2 laser.

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