Modeling Self-Propagating Exothermic Reactions in Multilayer Systems

1997 ◽  
Vol 481 ◽  
Author(s):  
S. Jayaraman ◽  
A. B. Mann ◽  
O. M. Knio ◽  
D. Van Heerden ◽  
G. Bao ◽  
...  
Keyword(s):  
Critical Thickness ◽  
Temperature Profiles ◽  
Bilayer Thickness ◽  
Free Standing ◽  
Multilayer Systems ◽  
Exothermic Reactions ◽  
Multilayer Foils ◽  
Reaction Characteristics ◽  
Reactive Foils ◽  
Experimental Values

ABSTRACTSelf-propagating reactions in free-standing multilayer foils provide a unique opportunity to study very rapid, diffusion-based transformations in non-equilibrium material systems. To fully understand the coupling between mass and thermal diffusion controlling these reactions and to optimize the commercial use of reactive foils, we have undertaken analytical and numerical modeling. Our analytical model predicts an increase in the reaction velocities with decreasing bilayer thickness down to a critical bilayer thickness and a reversal in this trend below the critical thickness. Predicting reaction characteristics such as the flame thermal width, the reaction zone width and the effect of variations in material properties with temperature has proven analytically intractable. To overcome these limitations, we have also used numerical methods to determine the composition and temperature profiles ahead of the reaction front for different multilayer periods and premixing. The results are compared with experimental values where possible.

Soldering and Brazing Metals to Ceramics at Room Temperature Using a Novel Nanotechnology

2006 ◽  
Vol 45 ◽  
pp. 1578-1587 ◽  
Author(s):  
A. Duckham ◽  
J. Levin ◽  
T.P. Weihs
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Thermal Stresses ◽  
Local Heat ◽  
Bonding Process ◽  
Free Standing ◽  
Multilayer Foils ◽  
Heats Of Mixing ◽  
Reactive Foils ◽  
Low Temperature Process

This paper reviews a new, low-temperature process for soldering and brazing ceramics to metals that is based on the use of reactive multilayer foils as a local heat source. The reactive foils range in thickness from 40μm to 100μm and contain many nanoscale layers that alternate between materials with large heats of mixing, such as Al and Ni. By inserting a free-standing foil between two solder (or braze) layers and two components, heat generated by the reaction of the foil melts the solder (or braze) and consequently bonds the components. The use of reactive foils eliminates the need for a furnace, and dramatically reduces the heating of the components being bonded. Thus ceramics and metals can be joined over large areas without the damaging thermal stresses that are typically encountered when cooling in furnace soldering or brazing operations. This paper draws on earlier work to review the bonding process and its application to a variety of ceramic-metal systems. Predictions of thermal profiles during bonding and the resulting residual stresses are described and compared with results for conventional soldering or brazing processes. The microstructure, uniformity, and physical properties of the reactive foil bonds are reviewed as well, using several different ceramic-metal systems as examples.

NanoBond® Assembly – A Rapid, Room Temperature Soldering Process

2011 ◽  
Vol 2011 (1) ◽  
pp. 000521-000526
Author(s):  
Jacques Matteau
Keyword(s):  
Room Temperature ◽  
New Technology ◽  
Local Heat ◽  
Temperature Sensitive ◽  
Ignition Process ◽  
Light Emitting ◽  
Exothermic Reactions ◽  
Soldering Process ◽  
Order Of Magnitude ◽  
Reactive Foils

Indium Corporation of America has commercialized a new technology that will revolutionize how manufacturers join components using solder materials. (See Figure 1) The joining process is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano-engineered materials, in which self-propagating exothermic reactions can be ignited at room temperature through an ignition process. By inserting a multilayer foil between two solder layers and two components, heat generated by the reaction in the foil melts the solder and consequently bonds are completed at room temperature in air, argon or vacuum in approximately one second. The resulting metallic joints exhibit thermal conductivities two orders of magnitude higher, and thermal resistivity’s an order of magnitude lower, than current commercial TIMs. The use of reactive foils as a local heat source eliminates the need for torches, furnaces, or lasers, speeds the soldering processes, and dramatically reduces the total heat that is needed. Thus, temperature-sensitive or small components can be joined without thermal damage or excessive heating. In addition, mismatches in thermal contraction on cooling can be avoided because components see very small increases in temperature. This is particularly beneficial for joining metals to ceramics. The fabrication and characterization of the reactive foils is described, and the value proposition for NanoBonding is presented. This presentation also shows the applicability of this platform technology to many areas of packaging including Thermal Interface Materials, microelectronics, optoelectronics, and Light Emitting Diodes (LEDs)

Theoretical Investigation of Fluorinated and Hydrocenated Diamond Filks

1992 ◽  
Vol 270 ◽  
Author(s):  
Mark R. Pederson ◽  
Warren E. Pickett
Keyword(s):  
Density Functional ◽  
Film Growth ◽  
Growth Models ◽  
Diamond Films ◽  
Diamond Surface ◽  
Free Standing ◽  
Level Shifts ◽  
Reconstructed Surface ◽  
Experimental Values ◽  
Diamond Film Growth

ABSTRACTTo investigate some of the fundamental differences between halogen and hydrogen assisted diamond film growth we have performed several calculations related to the <100> diamond surface. The models used in these investigations include ten-layer periodic slabs of free standing fluorinated diamond films as well as isolated clusters [C21F6H20]. For purposes of comparison, we have also performed calculations on models of the hydrogenated <100> surface. The calculations are performed within the density-functional framework using LCAO and LAPW computational methods. We have considered two geometries of a monofluoride surface. The first surface, best described as an ideal l×l surface with a monolayer of ionically bonded fluorines, exhibits a metallic density of states in contrast to a 2×l reconstructed surface with chemically bonded fluorines that is found to be insulating. We compare theoretical carbon core level shifts with experimental values and discuss growth models based on these surface calculations.

Strength, fracture and erosion properties of CVD diamond

1993 ◽  
Vol 342 (1664) ◽  
pp. 261-275 ◽  
Keyword(s):  
Experimental Studies ◽  
Chemical Vapour ◽  
Theoretical Work ◽  
Cvd Diamond ◽  
Bulge Test ◽  
High Modulus ◽  
Free Standing ◽  
Multilayer Systems ◽  
Erosion Properties ◽  
Bulk Diamond

Theoretical and experimental studies have been made on the effect of high modulus coatings on the stress fields generated by indentation and impact onto a flat half-space. The theoretical work used finite-element techniques and it shows that a high modulus coating can have a significant effect on the maximum tensile stresses generated in the substrate providing there is a good bond at the coating/substrate interface. Because it is technically difficult to deposit layers of more than a few micrometres thickness without residual stresses causing debonding, double and multilayer systems have also been examined theoretically. A variety of techniques have been used to determine the strength, modulus, expansion coefficient, thermal conductivity and other physical properties of chemical vapour deposition CVD diamond layers. These are briefly reviewed and data from our own studies using such techniques as the vibrating reed, bulge test and indentation are present. The erosion properties of both CVD coated substrates and CVD free-standing layers are presented for both liquid drop and solid particle erosion. Finally, a study has also been made of the frictional properties of various CVD diamond layers in a range of environments; data are compared with our earlier work on bulk diamond.

Modeling and characterizing the propagation velocity of exothermic reactions in multilayer foils

1997 ◽  
Vol 82 (3) ◽  
pp. 1178-1188 ◽  
Author(s):  
A. B. Mann ◽  
A. J. Gavens ◽  
M. E. Reiss ◽  
D. Van Heerden ◽  
G. Bao ◽  
...  
Keyword(s):  
Propagation Velocity ◽  
Exothermic Reactions ◽  
Multilayer Foils

Fabrication and Performance Characterization of Al/Ti Multilayer Energetic Films

2012 ◽  
Vol 557-559 ◽  
pp. 1782-1786
Author(s):  
Cheng Yang ◽  
Yan Hu ◽  
Rui Qi Shen ◽  
Ying Hua Ye ◽  
Shou Xu Wang ◽  
...  
Keyword(s):  
Exothermic Reaction ◽  
Rf Magnetron Sputtering ◽  
Multilayer Films ◽  
Atomic Ratio ◽  
Bilayer Thickness ◽  
Relative Thickness ◽  
Exothermic Reactions ◽  
And Performance ◽  
Dsc Curves

Al/Ti multilayer films with bilayer thicknesses of 50nm, 100nm and 200nm were prepared by RF magnetron sputtering alternate Al and Ti layers. The relative thickness of Al and Ti layers was maintained at a 1:1 ratio in order to obtain a 1:1 atomic ratio. XRD measurements show that the compound of AlTi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ti multilayer films with bilayer thicknesses of 50nm, 100nm and 200nm are 457.99 J∙g-1, 493.42 J∙g-1 and 696.81 J∙g-1, respectively. The exothermic reaction in Al/Ti multilayer films lead to more intense electric explosion. Al/Ti multilayer bridge films with modulation period of 50nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.

Exothermic reactions in cold-rolled Ni/Al reactive multilayer foils

2008 ◽  
Vol 23 (2) ◽  
pp. 367-375 ◽  
Author(s):  
X. Qiu ◽  
J. Graeter ◽  
L. Kecskes ◽  
J. Wang
Keyword(s):  
Phase Evolution ◽  
Reaction Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Exothermic Reactions ◽  
X Ray ◽  
Multilayer Foils ◽  
Cold Rolled ◽  
Two Peaks ◽  
Evolution Sequence

Exothermic reactions in cold-rolled Ni/Al reactive multilayer foils were investigated in this study. A two-stage reaction process was observed in the self-propagating reactions in the cold-rolled foils that were ignited by a point-source flame. Foils taken out of the flame after completing the first stage of the reaction process were compared to those allowed to complete both stages. Differences in the phase-evolution sequence from the two types of foils were studied by differential scanning calorimetry (DSC), using slow and controlled heating of the samples. Several exothermic peaks could be identified from the DSC thermograms for both types of foils. Using the DSC, both the as-cold-rolled and partially reacted foils were heated to each peak temperature to identify the reaction product associated with each peak. X-ray diffraction and scanning electron microscopy analyses showed that the first two peaks corresponded to the formation of Al3Ni, while the third peak corresponded to the formation of AlNi.

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