scholarly journals EVALUATION OF THE VOLATILE SPECIES ASSOCIATED WITH THE K-AREA COMPLEX BLEND CANS (D5043)

2021 ◽  
Author(s):  
KASEY NIXON
Keyword(s):  
Volatile Species

Control of Void Formation in Adhesively Bonded Joints in the Presence of Filler

2020 ◽  
Vol 2020 (1) ◽  
pp. 000246-000258
Author(s):  
Nina S. Dytiuk ◽  
Thomas F. Marinis ◽  
Joseph W. Soucy
Keyword(s):  
Finite Element ◽  
Open Source ◽  
Void Formation ◽  
Adhesive Joints ◽  
Bonded Joints ◽  
Volatile Species ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Open Source Program ◽  
Source Program

Abstract Adhesively bonded joints are ubiquitous in electronic assemblies that are used in a wide range of applications, which include automotive, medical, military, space and communications. The steady drive to reduce the size of assemblies in all of these applications, while providing increased functionality, generates a need for adhesive joints of higher strength, improved thermal and electrical conductivity and better dielectric isolation. All of these attributes of adhesive joints are degraded by the presence of voids in them. The quest to minimize voids in bonded structures motivated a previous study of their formation in a solvent cast, die bond epoxy film, which undergoes a liquid phase transition during cure. That work is extended in this study by including the effects of various filler morphologies in the adhesive. Fillers are added to adhesives to facilitate handling of thin sheet formats, control bond line thickness and reduce coefficient of thermal expansion. As such, fillers are selected to be inert with respect to the adhesive chemistry, while being readily wetted by it in the liquid state. Common filler morphologies include woven and molded open meshes, fibers chopped to uniform length, and spheres of uniform or distributed diameters. Void formation is influenced by a number factors, which include wettability of the bonded surfaces, adsorbed water, amount of solvent retained in the film, volume of entrapped air, thermal profile of the cure schedule, and clamping pressure during cure. The presence of fillers in the adhesive adds the additional factors of constrained diffusion paths and increased area for void nucleation. We have changed our approach to modeling the diffusion of volatile species in adhesive joints from a finite difference calculation in a uniform adhesive medium used previously, to a finite element model of a complex diffusion space. The open source program Gmsh is used to generate the diffusion space from a set of input parameters. The calculations of concentration profiles and diffusion fluxes of volatile species at the void interface are made using the open source finite element program elmer. As done previously, the position of the void interface is updated by integrating the product of time and flux of diffusing species over the area of the interface. The internal pressure of the void is determined by application of the Young-Laplace equation, while Henry’s law is used to estimate the concentration of diffusing species adjacent to the void interface. The calculation proceeds for a time equivalent to the integral of the time temperature product required to achieve a 70% cure state of the adhesive, at which point the void interface is immobile. The experimental approach is the same as used previously, with the filled adhesive sandwiched between glass slides and cured on a hot plate while imaged through a microscope. Images are automatically captured and analyzed by using the open source program imageJ, which allows us to track the evolution of individual voids as well as the time dependent distribution of the void population. We are working to correlate these experimental results with the predictions of our finite element calculations to allow us to make insightful choices of adhesives and optimize our bonding processes.

scholarly journals Evaporative cooling of icy interstellar grains

2020 ◽  
Vol 633 ◽  
pp. A97 ◽  
Author(s):  
Juris Kalvāns ◽  
Juris Roberts Kalnin
Keyword(s):  
Thermal Desorption ◽  
Thermal Energy ◽  
Energy Content ◽  
Cosmic Ray ◽  
Numerical Code ◽  
Radiative Cooling ◽  
Volatile Species ◽  
Interstellar Clouds ◽  
Ice Surface ◽  
Interstellar Grains

Context. While radiative cooling of interstellar grains is a well-known process, little detail is known about the cooling of grains with an icy mantle that contains volatile adsorbed molecules. Aims. We explore basic details for the cooling process of an icy grain with properties relevant to dark interstellar clouds. Methods. Grain cooling was described with the help of a numerical code considering a grain with an icy mantle that is structured in monolayers and containing several volatile species in proportions consistent with interstellar ice. Evaporation was treated as first-order decay. Diffusion and subsequent thermal desorption of bulk-ice species was included. Temperature decrease from initial temperatures of 100, 90, 80, 70, 60, 50, 40, 30, and 20 K was studied, and we also followed the composition of ice and evaporated matter. Results. We find that grain cooling occurs by partially successive and partially overlapping evaporation of different species. The most volatile molecules (such as N2) first evaporate at the greatest rate and are most rapidly depleted from the outer ice monolayers. The most important coolant is CO, but evaporation of more refractory species, such as CH4 and even CO2, is possible when the former volatiles are not available. Cooling of high-temperature grains takes longer because volatile molecules are depleted faster and the grain has to switch to slow radiative cooling at a higher temperature. For grain temperatures above 40 K, most of the thermal energy is carried away by evaporation. Evaporation of the nonpolar volatile species induces a complete change of the ice surface, as the refractory polar molecules (H2O) are left behind. Conclusions. The effectiveness of thermal desorption from heated icy grains (e.g., the yield of cosmic-ray-induced desorption) is primarily controlled by the thermal energy content of the grain and the number and availability of volatile molecules.

scholarly journals Rationale for BepiColombo Studies of Mercury’s Surface and Composition

2020 ◽  
Vol 216 (4) ◽  
Author(s):  
David A. Rothery ◽  
Matteo Massironi ◽  
Giulia Alemanno ◽  
Océane Barraud ◽  
Sebastien Besse ◽  
...  
Keyword(s):  
Heliocentric Distance ◽  
Topographic Mapping ◽  
Space Weathering ◽  
Volatile Species ◽  
Origin And Evolution ◽  
Geological Processes ◽  
Physical Chemical ◽  
Crustal Origin ◽  
Northern And Southern Hemispheres

Abstract BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury’s surface than the suite carried by NASA’s MESSENGER spacecraft. Moreover, BepiColombo’s data rate is substantially higher. This equips it to confirm, elaborate upon, and go beyond many of MESSENGER’s remarkable achievements. Furthermore, the geometry of BepiColombo’s orbital science campaign, beginning in 2026, will enable it to make uniformly resolved observations of both northern and southern hemispheres. This will offer more detailed and complete imaging and topographic mapping, element mapping with better sensitivity and improved spatial resolution, and totally new mineralogical mapping. We discuss MESSENGER data in the context of preparing for BepiColombo, and describe the contributions that we expect BepiColombo to make towards increased knowledge and understanding of Mercury’s surface and its composition. Much current work, including analysis of analogue materials, is directed towards better preparing ourselves to understand what BepiColombo might reveal. Some of MESSENGER’s more remarkable observations were obtained under unique or extreme conditions. BepiColombo should be able to confirm the validity of these observations and reveal the extent to which they are representative of the planet as a whole. It will also make new observations to clarify geological processes governing and reflecting crustal origin and evolution. We anticipate that the insights gained into Mercury’s geological history and its current space weathering environment will enable us to better understand the relationships of surface chemistry, morphologies and structures with the composition of crustal types, including the nature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models for Mercury’s origin including the nature and original heliocentric distance of the material from which it formed.

An alternative interface for CE–ICP–MS cadmium speciation in metallothioneins based on volatile species generation

2005 ◽  
Vol 546 (2) ◽  
pp. 236-243 ◽  
Author(s):  
G. Álvarez-Llamas ◽  
M.R. Fernández de la Campa ◽  
A. Sanz-Medel
Keyword(s):  
Volatile Species ◽  
Icp Ms ◽  
Cadmium Speciation
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