Porous thick-film silver metallisation for thermally mismatched brazing operations in tokamak magnetic sensor

2015 ◽  
Vol 2015 (CICMT) ◽  
pp. 000234-000238 ◽  
Author(s):  
Caroline Jacq ◽  
Thomas Maeder ◽  
Lucas Güniat ◽  
Adrien Corne ◽  
Duccio Testa ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Shear Stress ◽  
Electrical Resistivity ◽  
Thick Film ◽  
High Frequency ◽  
Graphite Powder ◽  
Alumina Substrate ◽  
Ceramic Technology ◽  
Maximal Stress ◽  
Sufficient Degree

A novel sensor based on thick-film + LTCC (low-temperature cofired ceramic) technology has been recently developed for sensing high-frequency 3D magnetic fields in tokamak fusion devices. For integration within the walls of the tokamak, the sensor has to be connected to the mineral-insulated cabling, which is carried out by brazing to ensure sufficient thermal stability. However, thermal mismatch stresses between the braze and the cable vs. the alumina substrate may cause local cracking of the latter during cooling, as the basic dense silver metallisation of the alumina does not provide a sufficient degree of stress decoupling. To address this issue, a series of porous metallisations have been formulated by incorporation of a mix of silver and fugitive graphite powder into a thick-film paste. To allow co-firing of thick, multi-layered prints. Such porous metallisations have allowed successful brazing operations, without cracking of the alumina substrate. Metallisations were assessed by measuring their electrical resistivity and shear stress have been realised as preliminary results to measure the influence of the porosity on the maximal stress before cracking.

Development of Glass-Free Metal Electrically Conductive Thick Films

2000 ◽  
Vol 123 (1) ◽  
pp. 64-69 ◽  
Author(s):  
Zongrong Liu ◽  
D. D. L. Chung
Keyword(s):  
Electrical Resistivity ◽  
Titanium Alloy ◽  
Thick Film ◽  
Thick Films ◽  
Pure Titanium ◽  
Glass Frit ◽  
Alumina Substrate ◽  
Electrically Conductive ◽  
Active Metal ◽  
Free Metal

Air-firable glass-free metal electrically conductive thick film pastes of different compositions were developed by using a titanium alloy component, and tin and zinc metal substitutes for glass frit used in traditional thick film pastes. The effect of different components on the electrical resistivity and bonding between the thick film and the alumina substrate was investigated. Thick films with low electrical resistivity and good bonding to the alumina substrate were obtained by using silver, zinc, tin, and TiCu alloy powders in the pastes. The addition of zinc at a small proportion (<0.5 wt.%) to a thick film paste enhanced the adhesion between the thick film and the alumina substrate with negligible increase in the electrical resistivity. The use of titanium alloy powder instead of pure titanium powder is preferred. Better composition distribution, and consequently, better wetting and bonding are expected by using active metal particles of a smaller size.

scholarly journals Solutions for thermally mismatched brazing operations for ceramic tokamak magnetic sensor

2016 ◽  
Vol 2016 (CICMT) ◽  
pp. 000058-000063 ◽  
Author(s):  
Caroline Jacq ◽  
Thomas Maeder ◽  
Benoit R. Ellenrieder ◽  
Philipp Windischhofer ◽  
Xinyue Jiang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thermal Stability ◽  
Low Temperature ◽  
High Frequency ◽  
Thermal Stresses ◽  
Magnetic Sensor ◽  
Temperature Gradients ◽  
Ceramic Technology ◽  
Vacuum Vessel ◽  
Main Substrate

Abstract To monitor high-frequency fluctuations of the equilibrium magnetic field in tokamaks, a 3D magnetic sensor has been developed. The sensor, which is positioned inside the vacuum vessel behind the protective tiles of the tokamak and is exposed to potential temperatures up to 400°C, is based on thick-film and LTCC (low-temperature co-fired ceramic) technology. To connect the sensor to the cabling that runs inside the vacuum vessel, mineral-insulated cables have to be brazed to the sensor to ensure electrical connection together with mechanical robustness and sufficient thermal stability. As the brazing temperature is about 600°C, direct brazing to the alumina sensor substrate can cause failure by cracking induced by thermal stresses. It arises both by temperature gradients stemming from the localised heating and by the high thermal mismatch of alumina with the braze and wire materials. In previous work, high stresses from temperature gradients were efficiently decoupled by brazing indirectly to alumina beams attached to the main substrate, and local thermal stresses between alumina and braze/wire by using a porous metallisation. However, as the slender alumina beams protruding out of the substrate are somewhat cumbersome and fragile, three alternatives were studied in the present work: 1) testing shorter and more robust beams, 2) replacing the alumina beam by a silver wire, and 3) depositing a porous temperature- and stress-decoupling dielectric to enable direct brazing on the main alumina substrate. These solutions are characterised with respect to their mechanical robustness and of the degree of thermal decoupling with the substrate they provide.

Structural, electrical and microwave properties of (Sr0.6Ca0.4) (CoyMn1−y) O3 (0.2 ≤ y ≤ 1.0) thick film ceramics

2016 ◽  
Vol 33 (1) ◽  
pp. 9-14 ◽  
Author(s):  
R.P. Pawar ◽  
Vijaya Puri
Keyword(s):  
Electrical Resistivity ◽  
Thick Film ◽  
Microwave Absorption ◽  
Thick Films ◽  
Alumina Substrate ◽  
Microwave Properties ◽  
Frequency Range ◽  
Content Type ◽  
Dc Electrical Resistivity ◽  
Permittivity And Permeability

Purpose – This paper aims to study the structural, electrical and microwave properties of (Sr0.6Ca0.4) (CoyMn1−y) O3 (0.2 ≤ y ≤ 1.0) thick-film ceramics. Design/methodology/approach – The thick films of (Sr0.6Ca0.4) (CoyMn1−y) O3 (0.2 ≤ y ≤ 1.0) on the alumina substrate have been delineated using screen printing technique. The structural analysis was carried out using an X-ray diffraction method and scanning electron microscopy. The direct current (DC) electrical resistivity is measured using a two-probe method. Microwave absorption was studied in the 8-18 GHz frequency range by using the Waveguide Reflectometer Method. The permittivity and permeability in the 8-18 GHz frequency range were measured by using Voltage Standing Wave Ratio slotted section method. Findings – The thick films have orthorhombic perovskite structure with dominant (020) plane. By using first-principle calculation method, theoretical and experimental lattice parameter and cell volume of (Sr0.6Ca0.4) (CoyMn1−y) O3 are matched with each other. The cobalt content changes the morphology from plates to needles. The DC electrical resistivity increases with increase in Co content and decreases with increase in temperature. (Sr0.6Ca0.4) (CoyMn1−y) O3 thick film shows 75 per cent microwave absorption both in the X band and Ku band. The microwave permittivity and permeability decreases with increase in frequency and Co content. Originality/value – Structural, electrical and microwave properties of (Sr0.6Ca0.4) (CoyMn1−y) O3 (0.2 ≤ y ≤ 1.0). Thick film ceramics on alumina substrate is reported for the first time.

Thermal stability and electrical resistivity of 14N-implanted nickel contacts on n+-Si

1983 ◽  
Vol 107 (1) ◽  
pp. 67-71 ◽  
Author(s):  
T. Banwell ◽  
M.-A. Nicolet ◽  
D.M. Scott
Keyword(s):  
Thermal Stability ◽  
Electrical Resistivity

Joint inversion of high-frequency induction and lateral logging sounding data in earth models with tilted principal axes of the electrical resistivity tensor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Oleg Nechaev ◽  
Viacheslav Glinskikh ◽  
Igor Mikhaylov ◽  
Ilya Moskaev
Keyword(s):  
Electrical Resistivity ◽  
High Frequency ◽  
Joint Inversion ◽  
Finite Element Approximation ◽  
Optimization Method ◽  
Multilevel Methods ◽  
Element Approximation ◽  
Resistivity Tensor ◽  
Principal Axes ◽  
High Frequency Induction

Abstract In this article, we are the first to formulate the direct and inverse problems of resistivity logging on determining the components of the electrical resistivity tensor of rocks from a set of high-frequency induction and lateral logging sounding measurements. Using a finite element approximation, high-order hierarchical basis functions, computationally efficient multilevel methods and a multistart algorithm with the DFO-LS local optimization method, we investigate the capability of reconstructing the horizontal and vertical resistivity components, as well as the tilt of the resistivity tensor principal axes with regard to the study of complex geological objects. A separate consideration is given to a realistic generalized geoelectric model of the unique hydrocarbon source with hard-to-recover reserves, the Bazhenov Formation.

Development of high frequency coreless transformer using thick film polymer technology

1999 ◽  
Vol 30 (2) ◽  
pp. 119-125 ◽  
Author(s):  
K.I. Arshak ◽  
B. AlMukhtar
Keyword(s):  
Thick Film ◽  
High Frequency ◽  
Film Polymer

scholarly journals A two-jet arc plasma: matrix effects and ways to their suppression

2019 ◽  
Vol 85 (1II)) ◽  
pp. 139-144
Author(s):  
N. P. Zaksas ◽  
A. F. Veryaskin
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Biological Samples ◽  
Matrix Effects ◽  
Certified Reference Materials ◽  
Organic Matrix ◽  
Graphite Powder ◽  
Powdered Sample ◽  
Experimental Conditions ◽  
Emission Analysis

A two-jet plasma is used for direct atomic emission analysis of powdered samples. It is characterized by relatively weak matrix effects, which allows using unified calibration samples on the basis of graphite powder for analysis of the samples with inorganic, organic, and organomineral matrix. In the present paper the effects limiting the usage of the unified approach due to different thermal stability and evaporation efficiency of the samples are discussed. The understated concentrations of a set of elements (Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Y) were obtained in analysis of certified reference materials of geological samples. It was shown that determination of rare earth elements should be carried out in the region behind the jet confluence providing their complete evaporation. For other elements, registration of the spectra in this region improves the results to some extent but they do not achieve the certified values. To speed up evaporation of these elements, the experimental conditions were chosen for plasma chemical reactions which provide conversion of the matrix elements into more volatile compounds. Addition of ammonium hydrofluoride to powdered sample considerably increased the line intensities of Al and Ca strongly associated with the silicon matrix. Incomplete evaporation was observed in analysis of biological samples with particle size more than 100 μm. A decrease in consumption of carrier argon is quite enough for effective decomposition of the organic matrix in plasma; the value of gas consumption depends on thermal stability and particle size of the sample. Preliminary sample carbonization is another way to improve evaporation of biological samples.

Effect of composition on thermal stability and electrical resistivity of Ta–Si–N films

2000 ◽  
Vol 365 (1) ◽  
pp. 19-21 ◽  
Author(s):  
J.O Olowolafe ◽  
I Rau ◽  
K.M Unruh ◽  
C.P Swann ◽  
Z.S Jawad ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Electrical Resistivity

Design and Fabrication of an LTCC Structure for a Microceramic Combustor

2012 ◽  
Vol 9 (3) ◽  
pp. 120-125 ◽  
Author(s):  
Darko Belavic ◽  
Marko Hrovat ◽  
Gregor Dolanc ◽  
Kostja Makarovic ◽  
Marina Santo Zarnik
Keyword(s):  
Thick Film ◽  
High Pressures ◽  
Three Dimensional ◽  
Temperature Sensors ◽  
Ceramic Technology ◽  
Electronic Components ◽  
Buried Structures ◽  
Flow Rates ◽  
Points Of View ◽  
Harsh Conditions

Advanced microsystems or macrosystems are in some cases made with multilayer ceramic technology. Low-temperature cofired ceramic (LTCC) technology is considered to be one of the more suitable technologies for the fabrication of ceramic microsystems that integrate screen-printed, thick-film electronic components as well as three-dimensional buried structures, for example, cavities and channels. One of the applications is a ceramic combustor. The chemical energy of the fuel is converted into thermal energy in a chemical microcombustor through a burning process, while the accompanying high temperatures and, frequently, high pressures, impose harsh conditions on the combustor structure. Therefore, the combustor must be carefully designed not only from the functional, thermal, and chemical points of view, but also with respect to the mechanical strength. The combustor device was prepared by lamination of Du Pont 951PX LTCC green tapes. The fabricated 3D LTCC structures with buried cavities and channels including two inlets (for fuel and air), the evaporator for the fuel, the mixing system of the channels (for mixing the evaporated fuel and air), the distribution channels and eight microburners were realized. The main parts are eight microburners realized as buried cavities. In the burners, a platinum-based catalyst was deposited to assist the oxidation, that is, the burning, of the methanol with the air. Thick-film, platinum-based heaters and temperature sensors are incorporated within the structure. The device was tested with different flow rates of liquid methanol (1 mL/h to 5 mL/h) and air (7 L/h to 15 L/h). The temperatures obtained were between 250°C and 450°C.

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