scholarly journals In-Situ Friction Monitoring of Self-Mated CVD Diamond Coatings Using Acoustic Emission

2006 ◽  
Vol 514-516 ◽  
pp. 749-753
Author(s):  
C.S. Abreu ◽  
Filipe J. Oliveira ◽  
J.R. Gomes ◽  
Manuel Belmonte ◽  
A.J.S. Fernandes ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Microwave Plasma ◽  
Normal Load ◽  
Chemical Vapour ◽  
Cvd Diamond ◽  
Ambient Atmosphere ◽  
Diamond Coatings ◽  
Ae Signal ◽  
State Regime

In-situ measurements of acoustic emission (AE) in self-mated tribological pairs of CVD diamond coated silicon nitride (Si3N4) were made with the purpose of investigating the relationship between AE signal and friction events. A good correlation is found between the energy dissipation/emission processes, therefore enabling the possibility of monitoring the different friction regimes occurring during the sliding contact of microcrystalline diamond (MCD) coatings. Deposition of MCD on flat and ball-shaped Si3N4 samples was accomplished using microwave plasma assisted chemical vapour deposition (MPCVD) with H2/CH4 gas mixtures. The friction behaviour of self-mated MCD coatings was assessed using a reciprocating ball-on-flat geometry. The tests were run in ambient atmosphere without lubrication, the frequency (1Hz) and stroke (6mm) were kept constant while the applied normal load varied in the range 10-80N. The microstructure, surface topography and roughness of the MCD coatings were characterised by SEM and AFM techniques. The diamond quality was assessed from micro-Raman spectroscopy. The friction evolution was characterised by a short running-in period where the main feature is a sharp peak reaching values as high as approximately 0.6 followed by a steady-state regime with very low values in the range 0.03-0.04.

The Design and Development of an Evaluation System for Redox Characteristics of Anode Supported SOFCs Using In-Situ Acoustic Emission and Electrochemical Technique

2012 ◽  
Author(s):  
S. Hashimoto ◽  
H. Watanabe ◽  
T. Sakamoto ◽  
T. Kawada ◽  
K. Yashiro ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Evaluation System ◽  
Voltage Drop ◽  
Cell Voltage ◽  
Test System ◽  
Electrochemical Technique ◽  
Gas Concentration ◽  
Ae Signal ◽  
Cell Test

In this study, a redox evaluation system for anode supported SOFCs using in-situ acoustic emission (AE) and electrochemical technique has been developed. The system consists of a gas blending unit, moisture controlling unit, AE cell evaluation probe, gas cooling exhaust, electrochemical cell test system and AE signal measurement system. The anode supported coin cells, which have the same thickness dimension as practical SOFCs have, can be evaluated under temperature and atmosphere controlled conditions. The oxygen partial pressure in the anodic atmospheres can be gradually controlled from air to reducing atmosphere using the gas blending unit which is connected to 6 gas cylinders. Humidity in the anodic atmospheres can be controlled by moisture controlling unit which consists of 2 bubblers form 0.86% (5°C saturation) up to 80% (94°C saturation). Redox process of the anode can be simulated in this system by controlled three oxidation modes, i.e. O2 gas oxidation, steam oxidation and electrochemical oxidation, which correspond to actual troubles, i.e. gas leakage, degradation of downstream and fuel depletion, respectively. An AE transducer can monitor the cell condition via an inner tube for a guide of exhaust from the cathode. Redox cell test for the anode supported coin cell has been examined at 770°C using this system. After the reduction of the anode substrate in moist H2, current 0.5Acm−2 loaded to the cell. And then H2 gas concentration had been reduced by stages. The cell voltage was down to below −6V after H2 gas concentration was reduced to pH2 = 2%. This drastic cell voltage drop and AE signal generation occurred at the same time. It is considered that Ni re-oxidation with fracture started at this time. Local delamination between anode and electrolyte, and also cracks at the electrolyte and cathode were observed after redox test. It was confirmed that AE sensing is effective for redox evaluation.

Properties of CVD Diamond/Metal Interface

1989 ◽  
Vol 162 ◽  
Author(s):  
Yusuke Mori ◽  
Hiroshi Kawarada ◽  
Akio Hiraki
Keyword(s):  
Room Temperature ◽  
Vapour Deposition ◽  
Microwave Plasma ◽  
Chemical Vapour ◽  
Point Contact ◽  
Cvd Diamond ◽  
Rectification Ratio ◽  
Metal Interface ◽  
Plasma Chemical ◽  
Plasma Chemical Vapour Deposition

ABSTRACTElectric properties of the interface between metal and semiconducting CVD diamond formed by microwave plasma chemical vapour deposition (CVD) have been investigated. Much better rectifying property due to Schottky barrier has been obtained in the films formed with CO(5%)/H2 compared with CH4(0.5%)/H2. A high breakdown voltage (200 V) and a high rectification ratio (105) have been observed at the evaporated Al/diamond interfaces formed with CO(5%)/H2. In the point contact interfaces, where the metal-carbon reaction is not expected at room temperature, the rectifying and ohmic property depends on the electronegativity of metals.

In-Situ Wear Monitoring of Slider and Disk Using Acoustic Emission

2000 ◽  
Vol 123 (1) ◽  
pp. 175-180 ◽  
Author(s):  
Kaoru Matsuoka ◽  
Koji Taniguchi ◽  
Masaru Nakakita
Keyword(s):  
Acoustic Emission ◽  
Wear Volume ◽  
Disk Interface ◽  
Wear Process ◽  
Slip Ring ◽  
Ae Signal ◽  
Wear Monitoring ◽  
Transducer Output ◽  
Ae Signals

The methodology has been developed for both the evaluation and analysis of slider/disk interface phenomena. We have been studying the direct relationships between the acoustic emission (AE) signal and wear of materials. The power in the AE signal is directly related to the power required for material removal in the wear process. This technique has been successfully applied to monitoring the wear of the tri-pad contact slider and the disk. The AE transducers were directly mounted onto both the arm with the slider and the disk in order to measure the slider/disk contact behavior. The AE transducer output from the disk was transmitted by the slip ring and the brush. The predicted wear of the slider and the disk based on the AE signals were computed from the relationship mentioned above. The measured wear of the slider and the disk were obtained by atomic force microscopy (AFM) and an optical surface analyzer (OSA) respectively. According to the experimental results, the predicted wear of both the slider and the disk using AE signals agreed with the wear which was measured. Therefore, wear can be estimated and monitored indirectly in-situ using the AE signals without direct measurements of the wear volume.

scholarly journals Interaction of Methane Concentration and Deposition Temperature in Atmospheric Laser Based CVD Diamond Deposition on Hard Metal

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 537
Author(s):  
Markus Prieske ◽  
Sven Müller ◽  
Peer Woizeschke
Keyword(s):  
Coating Thickness ◽  
Deposition Temperature ◽  
Laser Scanning ◽  
Methane Concentration ◽  
Chemical Vapour ◽  
Cvd Diamond ◽  
Hard Metal ◽  
Process Temperature ◽  
Diamond Coatings ◽  
Methane Concentrations

For laser-based plasma chemical vapour deposition (CVD) of diamond on hard metal at atmospheric pressure, without a vacuum chamber, the interaction between the deposition temperature and the methane concentration has to be understood to adjust the coating thickness, deposition duration, and medium diamond crystal size. The hypothesis of this study is that a wider range of methane concentrations could be used to deposit microcrystalline diamond coatings due to the increasing etching and deposition rates with rising deposition temperatures. The deposition of the CVD diamond coatings was carried out on K10 hard metal substrates. The process temperature and the methane concentration were varied from 650 to 1100 °C and from 0.15% to 5.0%, respectively. The coatings were analysed by scanning electron and 3D laser-scanning confocal microscopy, energy dispersive X-ray and micro-Raman spectroscopy, as well as cryofracture-based microscopy analysis. The results showed that microcrystalline diamond coatings could be deposited in a wider range of methane concentrations when increasing the process temperature. The coating thickness saturates depending on the process temperature even though the methane concentration constantly increases. The coating thickness increases with an increasing deposition temperature until the cobalt diffusion hinders the deposition at the process temperature of 1100 °C.

Characterization of CVD Diamond for Thermal Management Applications

2013 ◽  
Vol 2013 (1) ◽  
pp. 000511-000515
Author(s):  
R.S. Balmer ◽  
B. Bolliger ◽  
J.M. Dodson ◽  
D.J. Twitchen
Keyword(s):  
Thermal Management ◽  
Microwave Plasma ◽  
Chemical Vapour ◽  
Cost Effective ◽  
Cvd Diamond ◽  
Infrared Region ◽  
Infrared Transmission ◽  
Measurement Methodology ◽  
Transmission Measurements

Data is presented on state-of-the-art microwave plasma assisted chemical vapour deposited (CVD) diamond films with thicknesses between 0.1 and 0.8 mm. Infrared transmission measurements are compared with through-thickness and in-plane thermal conductivities measured using thermal flash and heated bar techniques, respectively. A simple model is presented and discussed on the correlation between thermal conductivity and the integrated absorption in the infrared region of the spectrum between 2760 and 3030 cm−1. This correlation opens the possibility to a cost effective, repeatable measurement methodology accurate enough for quality control and new recipe development.

Electron irradiation and heat treatment of polycrystalline CVD diamond

1993 ◽  
Vol 342 (1664) ◽  
pp. 253-260 ◽  
Keyword(s):  
Heat Treatment ◽  
Electron Irradiation ◽  
Vapour Deposition ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Chemical Vapour ◽  
Cvd Diamond ◽  
Other Point Defects ◽  
Resonant Raman ◽  
Original Strength

Photoluminescence and Raman spectra have been used to characterize the properties of diamond films grown by microwave plasma assisted chemical vapour deposition. Measurements at 77 K and excitation wavelengths in the range 476.5 nm to 514.5 nm show the presence of two components, A and B, in the Raman spectrum in addition to the diamond Raman line. The A and B components are rather similar in appearance and show resonant Raman behaviour. Electron irradiation results in the removal of the A and B Raman components, but they return to their original strength after after heating at 600 °C. The Raman scattering species interact with other point defects in the CVD films during heat treatment, and may be related to the presence of silicon in the diamond film.

CVD Diamond Coatings for Machining

2006 ◽  
Vol 526 ◽  
pp. 55-60 ◽  
Author(s):  
D. Moulin ◽  
O. Raymond ◽  
P. Chevrier ◽  
Paul Lipiński ◽  
Thierry Barre
Keyword(s):  
High Performance ◽  
Metal Cutting ◽  
Thermal Stresses ◽  
Chemical Vapour ◽  
Surface Preparation ◽  
Deposition Process ◽  
Cvd Diamond ◽  
Tool Geometry ◽  
Diamond Coatings ◽  
Machined Surface

Machining of modern materials requires high performance tools. More than 60% of metal cutting tools used are coated to limit abrasive wear. As the harder material known to man, diamond and consequently Chemical Vapour Deposited (CVD) diamond coatings allow to increase performances of tungsten carbide tools, i.e. tool life, machined surface quality, and to decrease costs. However, CVD diamond coated tools quality is very dependent on the surface preparation as much as the fabrication process parameters. This paper aims to discuss the influence of pretreatments before deposition, and thermal stresses induced by the cooling operation. Diamond deposition process is described emphasizing the role of every step and its function. Some numerical simulations of the residual stresses at the interface are presented, enlightening that tool geometry is an important factor while using a coating, and that tools must be designed for the diamond coating.

In-Situ Observation and Acoustic Emission Analysis for Corrosion Pitting of MgCl2 Droplet in SUS304 Stainless Steel

2012 ◽  
Vol 53 (6) ◽  
pp. 1069-1074 ◽  
Author(s):  
Mitsuharu Shiwa ◽  
Hiroyuki Masuda ◽  
Hisashi Yamawaki ◽  
Kaita Ito ◽  
Manabu Enoki
Keyword(s):  
Stainless Steel ◽  
Acoustic Emission ◽  
Emission Analysis ◽  
Sus304 Stainless Steel ◽  
Corrosion Pitting ◽  
Acoustic Emission Analysis

Hydrogen embrittlement of titanium during microwave plasma assisted CVD diamond deposition

2000 ◽  
Vol 16 (4) ◽  
pp. 355-360 ◽  
Author(s):  
Y. Fu ◽  
B. Yan ◽  
N.L. Loh ◽  
C.Q. Sun ◽  
P. Hing
Keyword(s):  
Hydrogen Embrittlement ◽  
Microwave Plasma ◽  
Cvd Diamond ◽  
Diamond Deposition

scholarly journals Analysis of Acoustic Emission (AE) Signals for Quality Monitoring of Laser Lap Microwelding

2021 ◽  
Vol 11 (15) ◽  
pp. 7045
Author(s):  
Ming-Chyuan Lu ◽  
Shean-Juinn Chiou ◽  
Bo-Si Kuo ◽  
Ming-Zong Chen
Keyword(s):  
Stainless Steel ◽  
Acoustic Emission ◽  
Frequency Domain ◽  
Monitoring System ◽  
Welding Quality ◽  
Steel Sheets ◽  
Signal Features ◽  
Ae Signal ◽  
Laser Microwelding ◽  
Ae Signals

In this study, the correlation between welding quality and features of acoustic emission (AE) signals collected during laser microwelding of stainless-steel sheets was analyzed. The performance of selected AE features for detecting low joint bonding strength was tested using a developed monitoring system. To obtain the AE signal for analysis and develop the monitoring system, lap welding experiments were conducted on a laser microwelding platform with an attached AE sensor. A gap between the two layers of stainless-steel sheets was simulated using clamp force, a pressing bar, and a thin piece of paper. After the collection of raw signals from the AE sensor, the correlations of welding quality with the time and frequency domain features of the AE signals were analyzed by segmenting the signals into ten 1 ms intervals. After selection of appropriate AE signal features based on a scatter index, a hidden Markov model (HMM) classifier was employed to evaluate the performance of the selected features. Three AE signal features, namely the root mean square (RMS) of the AE signal, gradient of the first 1 ms of AE signals, and 300 kHz frequency feature, were closely related to the quality variation caused by the gap between the two layers of stainless-steel sheets. Classification accuracy of 100% was obtained using the HMM classifier with the gradient of the signal from the first 1 ms interval and with the combination of the 300 kHz frequency domain signal and the RMS of the signal from the first 1 ms interval.

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