Microwave Absorbency Change of Nitride Powders under Vacuum Heating

2014 ◽  
Vol 88 ◽  
pp. 31-36
Author(s):  
Saburo Sano ◽  
Sadatsugu Takayama ◽  
Akira Kishimoto
Keyword(s):  
Microwave Absorption ◽  
Millimeter Wave ◽  
Wave Guide ◽  
Heating Process ◽  
Vacuum Furnace ◽  
Metal Powders ◽  
Mixed Powder ◽  
Compact Sample ◽  
Vacuum Heating ◽  
Increasing Temperature

We measured the microwave and millimeter-wave behaviors of ceramics and metal powders as a basis for developing microwave and millimeter-wave heating technology. In this study, nitride powders were subjected to microwave absorption measurements at elevated temperature. These measurements were performed using a system comprising a vector network analyzer, a circular wave-guide fixture, and a vacuum furnace. The sample’s microwave absorbency was evaluated by the change in reflection power from the sample in the circular wave-guide fixture under vacuum heating. Measurements were performed at approximately 24 GHz and at temperature up to approximately 1100°C. Boron nitride (BN) exhibited almost no absorption of microwaves up to 1100°C, similar to the results of a low-loss oxide powder such as alumina. Dichromium mononitride (Cr2N) powder exhibited a rather high absorption of microwaves at room temperature. During vacuum heating, absorbency of Cr2N started to decrease at 300°C, and became almost zero at temperature greater than 600°C, similar to the behavior of iron powder. This result indicated that roughly packed Cr2N powder absorbs microwave radiation; however, during vacuum heating, the compact body was sintered and the whole sample body became a reflector of microwaves. This change was irreversible, and the sample maintained its reflection behavior upon the cooling. When a mixed powder of Cr2N (20 mass%) and Al2O3 was heated under vacuum, the compact sample exhibited microwave absorption that increased with increasing temperature. This change was reversible upon cooling. These results indicated that the mixed powder did not become reflector of microwaves; Cr2N particles were not electrically connected each other because the Al2O3 particles kept the Cr2N particles separate during the vacuum heating process.

Microwave Absorbency Change of Zirconia Powder and Fiber during Vacuum Heating

2010 ◽  
Vol 63 ◽  
pp. 85-90 ◽  
Author(s):  
Saburo Sano ◽  
Shoji Kawakami ◽  
Yasumasa Takao ◽  
Sadatsugu Takayama ◽  
Motoyasu Sato
Keyword(s):  
Microwave Absorption ◽  
Stoichiometric Composition ◽  
Wave Guide ◽  
Stabilized Zirconia ◽  
Zirconia Powder ◽  
Partially Stabilized Zirconia ◽  
Zro2 Powder ◽  
Zirconia Fiber ◽  
Vacuum Heating ◽  
Absorption Measurements

Stabilized zirconia shows rather high microwave absorbency at room temperature, and the absorbency become higher with increasing temperature. In this study, stabilized zirconia powder, partially stabilized zirconia powder and zirconia fiber were subjected for microwave absorption measurements at elevated temperature. Microwave absorption measurements were done by using a system consists of a microwave vector network analyzer, a circular wave-guide fixture and a vacuum furnace. Microwave absorbency was evaluated by the reflection power change from the sample in the circular wave-guide fixture under vacuum heating. Microwave absorbency of stabilized zirconia powder, partially stabilized zirconia powder and zirconia fiber gradually increased with the increase of temperature. We supposed that the increase of microwave absorbency is related to the ionic (oxygen) conduction behavior of stabilized zirconia. Stoichiometric composition ZrO2 powder was also subjected for a measurement to consider the relation between microwave absorbency and ion conduction of zirconia. As the result, stoichiometric composition ZrO2 powder was not absorbed microwave power even when the powder was heated up to 900oC because it isn’t an oxygen ion conductor.

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VI—NON-RESONANT MICROWAVE ABSORPTION IN ULTRA-THIN Bi-Sr-Ca-Cu-O FILMS—

1992 ◽  
Vol 06 (05) ◽  
pp. 265-272 ◽  
Author(s):  
K. SUGAWARA ◽  
T. SUGIMOTO ◽  
D.J. BAAR ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Microwave Absorption ◽  
Signal Intensity ◽  
Critical Magnetic Field ◽  
High Tc Superconductors ◽  
Temperature Relation ◽  
High Tc ◽  
Absorption Studies ◽  
Increasing Temperature ◽  
Mgo Substrate

Non-resonant microwave absorption (NRMA) studies have been done for Bi-Sr-Ca-Cu-O (BSCCO) films with thicknesses of 30 Å and 15 Å fabricated on MgO substrate by MOCVD. For the latter two kinds of samples have been fabricated: BSCCO/MgO and BiOx/BSCCO/MgO . NRMA signals have been detected up to about 70–75 K for all the samples. The lower critical magnetic field H c1 * of the 30 Å film was severely increased by the application of a magnetic field of several kGauss, whereas it is almost unaffected in the case of 15 Å films. H c1 * increases but the signal intensity decreases with increasing temperature for all the 30 Å and 15 Å samples. The temperature dependence of the intensity is quite different from that of thicker films (100 Å and 350 Å), in which the intensity vs. temperature relation has a peak (or peaks) at particular temperature(s).

Titanium and Ti-13Nb-13Zr Alloy Porous Implants Obtained by Space-Holder Technique with Addition of Albumin

2012 ◽  
Vol 529-530 ◽  
pp. 574-579
Author(s):  
Tamiye Simone Goia ◽  
Kalan Bastos Violin ◽  
José Carlos Bressiani ◽  
Ana Helena de Almeida Bressiani
Keyword(s):  
Thermal Treatment ◽  
Surface Characterization ◽  
High Vacuum ◽  
Pure Titanium ◽  
Vacuum Furnace ◽  
Metal Powders ◽  
Space Holder ◽  
Significant Difference ◽  
13Zr Alloy ◽  
Hydride Titanium

Titanium and its alloys are the main metals studied as porous metallic implants by their excellent mechanical properties and biological interactions. Production methods of porous metallic materials are based on powder metallurgy (PM), because it allows the manufacturing of parts with complex shapes and dimensions close to the finals (near-net shape), and the addition of alloying elements reaching a satisfactory structural homogeneity, and porosity. The pore production by space-holder technique constitutes of mixing organic compounds with metal powder, which when removed by thermal treatment prior structures are kept in place. The objective of this study is to obtain porous implants of commercially pure titanium (cpTi) and Ti-13Nb-13Zr alloy by PM with space-holder technique and albumin as an additive. For the processing of the samples were used hydride titanium powder (TiH2) to obtain cpTi samples, and metal powders of Ti, Nb and Zr in the stoichiometric proportions for obtaining the alloy samples. The samples were prepared by mixing the metallic powder to the albumin (30wt%) and filling a silicone model that was pressed isostatically (140 MPa). The thermal treatment was performed in an oxidizing atmosphere (350°C/1h) for the decomposition of organic material. The sintering was performed at a temperature of 1300°C (1h/cpTi, 3h/Alloy) in high vacuum furnace (10-5 mBar) to all samples. The calculated porosity showed a significant difference between the samples cpTi (40%) and alloy (60%). The samples surface characterization showed very rough with high specific surface area. Samples of cpTi presented formation of necks arising from sintering. In the alloy samples were observed homogenous microstructure with the presence of α and β phases composing the Widmanstätten structure. It is possible to conclude that the same amount albumin allowed the formation of pores in the microstructure of cpTi and alloy although in different proportions, without harming the sintering of both and allowing diffusion of the alloy elements.

scholarly journals One-step fabrication of recyclable and robust fluorine/polymer-free superhydrophobic fabrics

RSC Advances ◽  
2017 ◽  
Vol 7 (39) ◽  
pp. 24374-24381 ◽  
Author(s):  
Sheng Wang ◽  
Sanding Wu ◽  
Jiazhang Zhang ◽  
Tao Wang
Keyword(s):  
Surface Energy ◽  
Heating Process ◽  
Pet Fabric ◽  
Low Surface Energy ◽  
Alkyl Groups ◽  
One Step ◽  
Vacuum Heating

Without using any low-surface-energy fluoro-containing groups or long alkyl groups, via a simple vacuum heating process, we prepared a robust superhydrophobic TiO2/PET fabric.

Hot electron generation via vacuum heating process in femtosecond laser–solid interactions

2001 ◽  
Vol 8 (6) ◽  
pp. 2925-2929 ◽  
Author(s):  
L. M. Chen ◽  
J. Zhang ◽  
Q. L. Dong ◽  
H. Teng ◽  
T. J. Liang ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Heating Process ◽  
Hot Electron ◽  
Electron Generation ◽  
Vacuum Heating ◽  
Laser Solid Interactions

scholarly journals Comparison between Microwave and Microwave Plasma Sintering of Nickel Powders

2011 ◽  
Vol 672 ◽  
pp. 289-292 ◽  
Author(s):  
Aidan P. Breen ◽  
Barry Twomey ◽  
Greg Byrne ◽  
Denis P. Dowling
Keyword(s):  
Nickel Powder ◽  
Microwave Plasma ◽  
Treatment Time ◽  
Rupture Strength ◽  
Tube Furnace ◽  
Heating Process ◽  
Metal Powders ◽  
Volumetric Heating ◽  
Plasma Sintering ◽  
Plasma Microwave

The objective of this study is to investigate the use of microwave plasma treatments as a processing technology for the sintering of metal powders. The volumetric heating process achieved with microwaves is considerably more efficient compared with resistance heating. The sintering study was carried out on 20 mm diameter by 2 mm thick compacted discs of nickel powder, with mean particle size of 1 µm. The discs were fired in a 5 cm diameter microwave plasma ball, under a hydrogen atmosphere at a pressure of 2 kPa. There was an increase in fired pellet transverse rupture strength (TRS) with plasma treatment duration. The mechanical properties of the sintered nickel discs were compared based on TRS, Rockwell hardness tests and density measurements. The morphology of the sintered discs was compared using microscopy and SEM. Comparison disc sintering studies were carried out using both a non plasma microwave and tube furnace firing. Using the microwave plasma sintering process full sintered disc strength of ≈1000 N (based on 3-point bend tests) was achieved after a 10 minute treatment time. In contrast the sintering time in the tube furnace treatment involved total processing time of up to 6 hours. The non plasma microwave system involved intermediate treatment periods of 2 hours. The degree of sintering between the individual nickel powder particles can be precisely controlled by the duration of the treatment time in the plasma.

TLP Bonding of DS Ni Base Superalloy, GTD-111 Using Mixed Powder of Base Metal and Filler Metal

2006 ◽  
Vol 15-17 ◽  
pp. 894-899
Author(s):  
Bong Keun Lee ◽  
Tae Kyo Han ◽  
Woo Young Song ◽  
C.H. Ye ◽  
Chung Yun Kang
Keyword(s):  
Base Metal ◽  
Filler Metal ◽  
Transient Liquid Phase ◽  
Early Time ◽  
Isothermal Solidification ◽  
Mixing Ratio ◽  
Metal Powders ◽  
Directionally Solidified ◽  
Mixed Powder ◽  
Base Superalloy

The effect of a mixed powder on the wide gap transient liquid phase diffusion bonding of a directionally solidified Ni base superalloy, GTD-111 was investigated. The mixed powder consisted of a mixture of a powdered Ni base filler (GNi-3) and powdered base metal (GTD-111). The range of the base metal powder was 40 to 70wt%. Bonding was performed at a temperature of 1463K, using various holding time. In the case of a lower 50wt%, the base metal powders completely melted and base metal mating at the interface dissolved at an early time, and extent of dissolution of base metal decreased with increasing mixing ratio. Liquid was eliminated by isothermal solidification, which was controlled by the diffusion of B into the base metal. The solids in the bonded interlayer grew epitaxially from the mating base metal inward from the insert metal and the number of grain boundaries formed at the bonded interlayer corresponded with those of the base metal. The finishing time for isothermal solidification was about 74ks. In the case 60wt% and higher, the base metal powders partially melted and remained in the vicinity of bonded interlayer. The solid was formed from the remaining powder and base metal mating at the interface. Finally, the bonded interlayer underwent the poly-crystallization when isothermal solidification was complete. The contents of Al and Ti in the bonded interlayer with a holding of 74ks were equal to that of the base metal.

Anti-Corrosion Properties of Composite WC-Ni Based Brazing Coatings

2011 ◽  
Vol 347-353 ◽  
pp. 1605-1608
Author(s):  
Da Quan Zhang ◽  
Li Xin Gao ◽  
Huan Wu
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
316L Stainless Steel ◽  
Vacuum Furnace ◽  
Corrosion Properties ◽  
Mixed Powder ◽  
Weight Loss Method ◽  
Loss Method ◽  
Superior Corrosion Resistance ◽  
Scanning Electron

The flexible metallic cloth was made of mixed powder consisting of WC and organic blend. A brazing coating was obtained through the high temperature brazing of the metallic cloth in vacuum furnace. The anti-corrosion of the brazing coating was investigated by weight-loss method and electrochemical measurements. The surface morphology observation was conducted by the scanning electron microscopy (SEM). The results show that the composite coating has superior corrosion resistance compared with 316L stainless steel.

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