scholarly journals Diffusion-Controlled Processes in Microwave-Fired Oxide Ceramics

1990 ◽  
Vol 189 ◽  
Author(s):  
Mark A. Janney ◽  
Hal D. Kimrey
Keyword(s):  
Experimental Work ◽  
Diffusion Coefficients ◽  
National Laboratory ◽  
Oxide Ceramics ◽  
Oak Ridge ◽  
Enhanced Diffusion ◽  
Controlled Processes ◽  
The Past ◽  
Diffusion Controlled ◽  
Satisfactory Theory

ABSTRACTProcessing oxide-based ceramics using microwave heating leads to a number of unexpected results, which can only be interpreted in terms of enhanced diffusion. Enhanced sintering has been observed in alumina and zirconia. Accelerated grain growth in dense, hot-pressed alumina has been demonstrated. Increased diffusion coefficients have been observed for diffusion of oxygen in sapphire. As yet, a satisfactory theory to account for these phenomena has not been developed. This paper reviews the experimental work conducted at the Oak Ridge National Laboratory during the past four years on the processing of oxides in both 2.45 and 28 GHz microwave furnaces.

scholarly journals Nonlinear Crack Growth Monitoring

2000 ◽  
Author(s):  
Donald E. Welch ◽  
Lee M. Hively ◽  
Ray F. Holdaway
Keyword(s):  
Crack Propagation ◽  
End Of Life ◽  
Crack Growth ◽  
National Laboratory ◽  
Growth Monitoring ◽  
High Quality ◽  
Oak Ridge ◽  
The Past ◽  
Fiberglass Composite ◽  
Nonlinear Crack

Abstract Structures subject to crack growth spend 90–95% of their lifetime in nucleation of very tiny flaws into measurable crack sizes. Due to the large variation in initial flaw sizes and the mathematics of flaw growth, the fatigue lifetimes, even of high-quality structures, can vary by a factor of as much as 10 to 20 even in a small fleet. This large variation in fatigue lifetimes leads to conservative statistics, which often prompts the premature retirement or overhaul of structures, since they focus on the weakest members of the fleet, while the remainder of the fleet is sound. In the past two years, Oak Ridge National Laboratory (ORNL) has developed a new Griffith energy-based technique that can provide useful warning of the impending failure of a structure due to end-of-life crack propagation. This technique has been demonstrated by test and analysis in fiberglass composite for tension-tension fatigue.

scholarly journals Determination of Grain Boundary Diffusion Coefficients in C-Regime by Hwang-Balluffi Method: Silver Diffusion in Pd

2009 ◽  
Vol 289-292 ◽  
pp. 763-767 ◽  
Author(s):  
Z. Balogh ◽  
Z. Erdélyi ◽  
Dezső L. Beke ◽  
Alain Portavoce ◽  
Christophe Girardeaux ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Controlled Processes ◽  
Diffusion Controlled ◽  
Arrhenius Function ◽  
Data Points ◽  
Accumulation Kinetics

Diffusion controlled processes play a crucial role in the degradation of technical materials. At low temperatures the most significant of them is the diffusion along grain boundaries. In thin film geometry one of the best methods for determining the grain boundary (GB) diffusion coefficient of an impurity element is the Hwang-Balluffi method, in which a surface sensitive technique is used to follow the surface accumulation kinetics. Results of grain boundary diffusion measurements, carried out in our laboratory by this method in three different materials systems (Ag/Pd, Ag/Cu and Au/Ni) are reviewed. In case of Ag diffusion along Pd GBs the surface accumulation was followed by AES method. The data points can be well fitted by an Arrhenius function with an activation energy Q=0.99eV

A Review of Molten Salt Reactor Xenon Analysis Literature

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
T. J. Price ◽  
O. Chvala
Keyword(s):  
Molten Salt ◽  
Void Fraction ◽  
Experimental Work ◽  
National Laboratory ◽  
A Priori ◽  
Molten Salt Reactor ◽  
Oak Ridge ◽  
Sensitive Dependence ◽  
Oak Ridge National Laboratory ◽  
Work Done

Abstract This paper presents a review of xenon analyses literature related to molten salt reactors (MSRs). A brief primer of reactor xenon theory is presented for fluid fueled reactors. A review of xenon analysis literature is presented for both the work done by the Oak Ridge National Laboratory, and the later work in academia. A review of experimental work is presented. The paper concludes with describing some of the difficulties in establishing a priori xenon models and includes a commentary on the sensitive dependence of the molten salt reactor xenon behavior on the circulating void fraction.

Revision of NNSA Packaging Certification Division’s Safety Guide 100 (SG-100)

2004 ◽  
Author(s):  
Matthew R. Feldman
Keyword(s):  
National Laboratory ◽  
Lessons Learned ◽  
National Standards ◽  
Guidance Document ◽  
Package Design ◽  
Oak Ridge ◽  
The Past ◽  
Nuclear Security ◽  
Analytical Tools ◽  
Transportation Technologies

The Transportation Technologies Group (TTG) of Oak Ridge National Laboratory (ORNL) is currently tasked, by National Nuclear Security Administration (NNSA) Service Center (SC), Office of technical Support (OTS), National Security Department (NSD), Packaging Certification Division (PCD), to revise the Defense Programs’ Safety Guide 100 (SG-100). SG-100, formally entitled “Design Guide for Packaging and Offsite Transportation of Nuclear Components, Special Assemblies, and Radioactive Materials Associated with the Nuclear Explosives and Weapons Safety Program” is being revised to reflect current regulations as well as to incorporate lessons learned over the past several years. SG-100 was last published in 1994 as Revision 1, and has served as the key guidance document for the development of Defense Programs’ Type B package designs as well as their testing and testing and certification. Since that time, there have been two major revisions to the U.S. packaging and transportation regulations (due to revisions to US federal regulations, IAEA guidelines, and national standards), re-engineering of the DOE establishing the semi-autonomous NNSA, as well as numerous improvements in the analytical tools and methodologies used in package design and confirmatory review. This revision to SG-100 will capture these changes as well as reflect various lessons learned from certification reviews which have taken place over the past decade. TTG has also been tasked by PCD to present a workshop based on the revised SG-100 in September 2004.

Microwave Processing of Ceramics: Guidelines Used at the Oak Ridge National Laboratory

1992 ◽  
Vol 269 ◽  
Author(s):  
Mark A. Janney ◽  
Hal D. Kimrey ◽  
James O. Kiggans
Keyword(s):  
National Laboratory ◽  
Thermal Conditions ◽  
Microwave Processing ◽  
Thermal Gradients ◽  
Exothermic Reactions ◽  
Oak Ridge ◽  
The Past ◽  
Heating And Cooling ◽  
Oak Ridge National Laboratory ◽  
Insulation Systems

ABSTRACTTo make meaningful comparisons between conventional and microwave processing of materials, one must conduct experiments that are as similar as possible in the two environments. Particular attention must be given to thermal conditions, sample parameters, and furnace environment. Under thermal conditions, one must consider temperature measurement (pyrometer or thermocouple, sheath type, and arcing of thermocouples), thermal history (heating and cooling rates, thermal gradients), and exothermic reactions. Regarding sample parameters, one must. consider sample size, and packing powders and insulation systems. With respect to furnaces, one must consider differences in atmosphere, impurities, and uniformity of heating. Examples will be drawn from diffusion, grain growth, sintering, nitridation, and drying experiments conducted at the Oak Ridge National Laboratory (ORNL) over the past six years.

The Cyclic Carburization Process by Bi-velocity Method

2015 ◽  
Vol 34 (4) ◽  
Author(s):  
Bartek Wierzba ◽  
Jolanta Romanowska ◽  
Krzysztof Kubiak ◽  
Jan Sieniawski
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Stress Distribution ◽  
Stress Field ◽  
Diffusion Coefficients ◽  
Numerical Solutions ◽  
Concentration Profiles ◽  
Controlled Processes ◽  
Diffusion Controlled ◽  
Diffusive Component

AbstractThe paper presents numerical analysis of the cyclic external fluxes on diffusion process. It is shown, that the cycles characteristics strongly affects the concentration profiles and stress distribution in material. Calculations were performed using the bi-velocity method with the stress field factor. Moreover, the more general model describing the cyclic carburization process influenced by self stress was formulated. Numerical solutions were obtained assuming composition dependent diffusion coefficients. The results of simulation were compared with the experimental data. The model proposed in this paper may be applied to other diffusion controlled processes with the external flux of the diffusive component.

scholarly journals Landscape Level Interactions Among Ungulates, Vegetation, and Large-Scale Fires in Northern Yellowstone National Park

1990 ◽  
Vol 14 ◽  
pp. 179-181
Author(s):  
Monica Turner ◽  
William Romme ◽  
Linda Wallace
Keyword(s):  
Populus Tremuloides ◽  
Large Scale ◽  
National Laboratory ◽  
Model Development ◽  
Field Studies ◽  
Full Time ◽  
Oak Ridge ◽  
The Past ◽  
Substantial Progress ◽  
Made In

Substantial progress has been made in both the modeling and field studies during the first six months of research funding. Yegang Wu, Jennifer O'Hara, and Michael O'Hara all began working full time for the project on September 1, 1990. Wu is based at Oak Ridge National Laboratory (ORNL) and is working primarily on model development and analyses using the geographic information system (GIS) located in Yellowstone. The O'Hara's are based in Yellowstone and are working full time on the field studies. Here we describe our progress during the past six months for each main area of the proposed work: 1. field studies, including aspen (Populus tremuloides) and grassland sampling, and 2. model development and GIS analyses.

Plug-in scripts for EFTEM automation

1996 ◽  
Vol 54 ◽  
pp. 546-547
Author(s):  
N. D. Evans ◽  
M. K. Kundmann
Keyword(s):  
Electron Microscopy ◽  
National Laboratory ◽  
Oak Ridge ◽  
Multiple User ◽  
Transmission Electron ◽  
Short Period ◽  
User Facility ◽  
Instrument Control ◽  
And Control ◽  
Research Equipment

Post-column energy-filtered transmission electron microscopy (EFTEM) is inherently challenging as it requires the researcher to setup, align, and control both the microscope and the energy-filter. The software behind an EFTEM system is therefore critical to efficient, day-to-day application of this technique. This is particularly the case in a multiple-user environment such as at the Shared Research Equipment (SHaRE) User Facility at Oak Ridge National Laboratory. Here, visiting researchers, who may oe unfamiliar with the details of EFTEM, need to accomplish as much as possible in a relatively short period of time.We describe here our work in extending the base software of a commercially available EFTEM system in order to automate and streamline particular EFTEM tasks. The EFTEM system used is a Philips CM30 fitted with a Gatan Imaging Filter (GIF). The base software supplied with this system consists primarily of two Macintosh programs and a collection of add-ons (plug-ins) which provide instrument control, imaging, and data analysis facilities needed to perform EFTEM.

Quantitative surface damage studies by H.R.E.M.

1989 ◽  
Vol 47 ◽  
pp. 632-633
Author(s):  
S. R. Singh ◽  
H. J. Fan ◽  
L. D. Marks
Keyword(s):  
Solar Wind ◽  
Quantitative Analysis ◽  
Surface Science ◽  
Surface Damage ◽  
Space Environment ◽  
Oxygen Desorption ◽  
The Past ◽  
Diffusion Controlled ◽  
Original Observation ◽  
Substantial Interest

Since the original observation that the surfaces of materials undergo radiation damage in the electron microscope similar to that observed by more conventional surface science techniques there has been substantial interest in understanding these phenomena in more detail; for a review see. For instance, surface damage in a microscope mimics damage in the space environment due to the solar wind and electron beam lithographic operations.However, purely qualitative experiments that have been done in the past are inadequate. In addition, many experiments performed in conventional microscopes may be inaccurate. What is needed is careful quantitative analysis including comparisons of the behavior in UHV versus that in a conventional microscope. In this paper we will present results of quantitative analysis which clearly demonstrate that the phenomena of importance are diffusion controlled; more detailed presentations of the data have been published elsewhere.As an illustration of the results, Figure 1 shows a plot of the shrinkage of a single, roughly spherical particle of WO3 versus time (dose) driven by oxygen desorption from the surface.

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