Diamond Nucleation Studies on Refractory Metals and Nickel

1994 ◽  
Vol 339 ◽  
Author(s):  
S. D. Wolter ◽  
B. R. Stoner ◽  
P. C. Yang ◽  
W. Lui ◽  
J. T. Glass
Keyword(s):  
High Temperature ◽  
Initial Data ◽  
Refractory Metal ◽  
Hydrogen Absorption ◽  
Substrate Material ◽  
Diamond Growth ◽  
Relative Importance ◽  
Lattice Match ◽  
Diamond Nucleation ◽  
Temperature Pretreatment

ABSTRACTDiamond nucleation has been investigated on a variety of potential heteroepitaxial substrate materials. Previous work in this laboratory has demonstrated heteroepitaxial nucleation on both Si and SiC substrates via bias-enhanced nucleation (BEN). In this study the effects of BEN of diamond on refractory metal substrates is investigated in detail. Initial data suggest a strong correlation between the carbide forming nature of the substrate material and the rate of nucleation during biasing. Our second avenue of research involves low pressure diamond growth on nickel. This material is a promising material due to its close lattice match and recent evidence of epitaxy reported by other researchers. To form heteroepitaxial diamond on nickel a high temperature pretreatment routine has been established and is the basis for this area of research. The relative importance of hydrogen absorption during this routine is explored and correlated to the formation and degree of diamond epitaxy.

WIELAND DURO TANTALUM

Alloy Digest ◽  
2020 ◽  
Vol 69 (11) ◽  
Keyword(s):  
High Temperature ◽  
Powder Metallurgy ◽  
Physical Properties ◽  
Tensile Properties ◽  
Refractory Metal ◽  
Temperature Performance

Abstract Wieland Duro Tantalum is unalloyed tantalum that is produced from powder metallurgy consolidated ingots. It is a versatile refractory metal that is used in demanding applications requiring resistance to high temperature and corrosion. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on low and high temperature performance as well as machining and joining. Filing Code: Ta-14. Producer or source: Wieland Duro GmbH.

Processing high-temperature refractory-metal silicide in-situ composites

JOM ◽  
1999 ◽  
Vol 51 (4) ◽  
pp. 32-36 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
P. R. Subramanian
Keyword(s):  
High Temperature ◽  
Refractory Metal ◽  
Metal Silicide ◽  
In Situ Composites

Fracture and Fatigue of Niobium Silicide Alloys

2008 ◽  
Vol 1128 ◽  
Author(s):  
David M. Herman ◽  
Bernard P Bewlay ◽  
Laurent Cretegny ◽  
Richard DiDomizio ◽  
John Lewandowski
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Refractory Metal ◽  
Fatigue Behavior ◽  
Metal Phase ◽  
Metal Silicide ◽  
Alloy Composite ◽  
Niobium Silicide ◽  
Composite Properties

AbstractThe fracture and fatigue behavior of refractory metal silicide alloys/composites is significantly affected by the mechanical behavior of the refractory metal phase. This paper reviews some of the balance of properties obtained in the alloys/composites based on the Nb-Si system. Since some of the alloy/composite properties are dominated by the behavior of the refractory metal phase, the paper begins with a review of data on monolithic Nb and its alloys. This is followed by presentation of results obtained on Nb-Si alloys/composites and a comparison to behavior of some other high temperature systems.

Seed Germination Ecology of Itchgrass (Rottboellia cochinchinensis)

Weed Science ◽  
2011 ◽  
Vol 59 (2) ◽  
pp. 182-187 ◽  
Author(s):  
Grace E-K. Bolfrey-Arku ◽  
Bhagirath S. Chauhan ◽  
David E. Johnson
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
Seedling Emergence ◽  
Soil Surface ◽  
The Philippines ◽  
Integrated Weed Management ◽  
Burial Depth ◽  
Soil Burial ◽  
Dark Regime ◽  
Temperature Pretreatment

Itchgrass is a weed of many crops throughout the tropics and one of the most important grass weeds of rainfed rice. Experiments were conducted in the laboratory and screenhouse to determine the effects of light, alternating day/night temperatures, high temperature pretreatment, water stress, seed burial depth, and rice residue on seed germination and seedling emergence of itchgrass in the Philippines. Two populations were evaluated and the results were consistent for both populations. Germination in the light/dark regime was greater at alternating day/night temperatures of 25/15 C than at 35/25, 30/20, or 20/10 C. Light was not a requirement for germination, but a light/dark regime increased germination by 96%, across temperature and population. A 5-min high temperature pretreatment for 50% inhibition of maximum itchgrass germination ranged from 145 to 151 C with no germination when seeds were exposed to ≥ 180 C. The osmotic potential required for 50% inhibition of maximum germination was −0.6 MPa for itchgrass, although some seeds germinated at −0.8 MPa. Seedling emergence was greatest for seeds placed on the soil surface, and emergence declined with increasing soil burial depth; no seedlings emerged from seeds buried at 10 cm. The addition of rice residue to soil surface in pots at rates equivalent to 4 to 6 Mg ha−1reduced itchgrass seedling emergence. Since seedling emergence was greatest at shallow depths and germination was stimulated by light, itchgrass may become a problem in systems where soil is cultivated at shallow depths. Knowledge gained in this study could contribute to developing components of integrated weed management strategies for itchgrass.

Improvement of Dielectric Performance of a Prototype AlN High Temperature Chip-level Package

2011 ◽  
Vol 2011 (HITEN) ◽  
pp. 000052-000057 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
High Temperatures ◽  
Substrate Surface ◽  
Substrate Material ◽  
Glass Coating ◽  
Temperature Dependent ◽  
High Temperature Electronics ◽  
Dielectric Performance ◽  
Parasitic Parameters

Aluminum nitride (AlN) has been proposed as a packaging substrate material for reliable high temperature electronics operating in a wide temperature range. However, it was discovered in a recent study that the dielectric properties of some commercial polycrystalline AlN materials change quite significantly with temperature at high temperatures. These material properties resulted in undesired large and temperature-dependent parasitic parameters for a prototype chip-level package based on an AlN substrate with the yttrium oxide dopant. This paper reports a method using a coating layer of a commercial thick-film glass on the AlN substrate surface to significantly reduce both the parasitic capacitances and parasitic conductances between neighboring inputs/outputs (I/Os) of a prototype AlN chip-level package. The parasitic parameters of 8-I/Os low power chip-level packages with the insulating glass coating were characterized at frequencies from 120 Hz to 1 MHz between room temperature and 500°C. These results were compared with the parameters of AlN packages without the glass coating. The results indicate that the parasitic capacitances and conductances between I/Os of the improved prototype AlN packages are significantly reduced and stable at high temperatures. The method using a glass coating provides a feasible way to mitigate the temperature dependence of dielectric properties of AlN and further utilize AlN as a reliable packaging substrate material for high temperature applications.

scholarly journals Coating Reactions on Vanadium and V-Si-B Alloys during Powder Pack-Cementation

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4099
Author(s):  
Georg Hasemann ◽  
Chad Harris ◽  
Manja Krüger ◽  
John H. Perepezko
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Refractory Metal ◽  
Pack Cementation ◽  
Solid Solution Phase ◽  
Major Drawback ◽  
Three Phase ◽  
Structural Applications ◽  
New Type ◽  
Refractory Metal Alloys

Alloys in the V-Si-B system are a new and promising class of light-weight refractory metal materials for high temperature applications. Presently, the main attention is focused on three-phase alloy compositions that consist of a vanadium solid solution phase and the two intermetallic phases V3Si and V5SiB2. Similar to other refractory metal alloys, a major drawback is the poor oxidation resistance. In this study, initial pack-cementation experiments were performed on commercially available pure vanadium and a three-phase alloy V-9Si-5B to achieve an oxidation protection for this new type of high temperature material. This advance in oxidation resistance now enables the attractive mechanical properties of V-Si-B alloys to be used for high temperature structural applications.

scholarly journals A Microscopy and FTIR and PL Spectra Study of Polycrystalline Diamonds from Mengyin Kimberlite Pipes

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Zhijun Yang ◽  
Rong Liang ◽  
Xiangqing Zeng ◽  
Mingsheng Peng
Keyword(s):  
Growth Period ◽  
Diamond Growth ◽  
Dissolution Process ◽  
Diamond Nucleation ◽  
Pl Spectra ◽  
Nucleation Stage ◽  
Diamond Single Crystals ◽  
Mantle Fluids ◽  
Higher Temperature ◽  
P Type

The results of a microscopy and FTIR and PL spectra study of the natural polycrystalline diamonds from the Mengyin kimberlite pipes show that they can be classified as the euhedral faceted polycrystalline diamonds (EFPCDs) and anhedral rounded polycrystalline diamonds (ARPCDs). Different diamond grains or their points were formed in different conditions or processes. They were not formed in diamond nucleation stage, but in the diamond growth period. They probably originated from the relatively deeper mantle and were formed in the environment like the peridotitic (P) type diamond single crystals. The EFPCDs did not undergo a remarkable dissolution process during their formation and were possibly fast formed shortly before the kimberlite eruption. The ARPCDs not only were formed at a higher temperature than the EFPCDs but also underwent a notable dissolution process and had been stored relatively longer in the mantle. Fluids or melts probably participated in the formation of the ARPCDs or modified them during the period of their storage in the mantle.

Plastic Deformation of Approximants: Dislocations vs. Phason Lines

1998 ◽  
Vol 553 ◽  
Author(s):  
H. Klein ◽  
M. Feuerbacher ◽  
P. Schall ◽  
K. Urban
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Single Crystals ◽  
Periodic Lattice ◽  
Length Scale ◽  
Relative Importance ◽  
Line Lattice ◽  
Burgers Vector ◽  
Mechanisms Of Plastic Deformation

AbstractDeformation experiments were performed on single crystals of the ξ-AIPdMn approximant in bending geometry at high temperature. Two different mechanisms of plastic deformation are shown to exist in this phase: one based on dislocations and another novel mechanism based on the motion of phason lines. Burgers vector and line directions of dislocations were determined. Phason lines are shown to build a periodic lattice. The interaction of a dislocation with the phason line lattice results in dislocations on another length scale. This meta-dislocation in the periodic phason line lattice has a Burgers vector of magnitude 165 Å. The relative importance of phason lines and dislocations for the plastic deformation is discussed as a function of the orientation of the sample with respect to the bending geometry.

The Effect of NaCl(g) in High Temperature Oxidation

1982 ◽  
Author(s):  
J. G. Smeggil ◽  
N. S. Bornstein
Keyword(s):  
High Temperature ◽  
Sodium Chloride ◽  
Gas Turbine ◽  
High Temperature Oxidation ◽  
Condensed State ◽  
Relative Importance ◽  
Protective Oxide ◽  
Temperature Oxidation ◽  
High Temperature Materials ◽  
Nacl Vapor

Sodium chloride can be present in gas turbine hot sections in the vapor as well as the condensed state. Particles containing sodium chloride may randomly break from compressor components, then impinge upon and stick to turbine components further down the gas path. However, NaCl vapor can deleteriously affect processes involving the formation and maintenance of protective oxide layers on turbine components. The relative importance of these two distinctly different mechanisms involving NaCl in corrosion processes is currently unknown. Numerous studies have dealt with the effect on corrosion behavior of Na2SO4-NaCl condensed mixtures with appreciable amounts of NaCl. However, the possibility that low NaCl vapor activities effect major changes in oxide scale formation and retention is equally as probable as that involving condensed NaCl. Therefore, the results presented here will deal with effects of low activities of NaCl vapor (0.1–100 ppm) upon scales formed by selected high temperature materials.

Sign in / Sign up

Export Citation Format

Share Document