Solid state aging

The density of the CusSns may increase with the aging time, especially in the quenched solder joints from high reflow temperatures and long reflow time, because the fast cooling rate suppressed the precipitation of the CusSns phase during solidification. The subsequent solid state aging provided an opportunity for the supersaturated Cu to precipitate (Ref 7). However, if the eutectic Sn-Ag-Cu solder joints are attached to... 

At least four separate studies have reported void formation in the 8-Cu3Sn phase and degradation of the joint strength after long-term solid state aging. An SEM photo of a cross section of a Cu/eutectic Sn-Pb interface after baking for 20 days at 125 °C (257 °F) is shown in Fig. 7. 

FIG. 12 Optical micrograph of the interface between 37Pb-63Sn solder and copper (Cu) showing the intermetallic compoxmd layer that developed after solid-state aging at 135 °C for 400 days. (Courtesy of Sandia National Laboratories.)... 

FIG. 15 SEM micrographs showing development of the intermetallic compound layer between 37Pb-63Sn and An base metal following solid-state aging for 90 days at (a) 70"C and (b) 100 C. (Courtesy of Sandia National Laboratories.)... 

Thick-film metal compositions are elemental metals Ag, Pt, Au as well as alloy compositions Au-Pd, Au-Pt, Au-Pt-P4 Ag-Pd, and Ag-Pt. (A limited number of HMC assemblies use Cu-and Ni-based, thick-film systems.) Lead-tin solder joints made to these metal compositions present several challenges. First, the elemental hlms, Ag and Au, exhibit relatively fast dissolution rates in Pb-Sn solder. Excessive dissolution can risk complete consumption of the thick film and loss of the conductor pad. Second, rapid solid-state intermetallic compound layer growth occurs between the thick-film compositions and Pb-Sn solders, even at modest service temperatures [54-57]. The consequences of solid-state aging are a thick, brittle intermetallic compound layer and loss of the thick film layer. 

Hyperpure silicon can be doped with boron, gallium, phosphorus, or arsenic to produce silicon for use in transistors, solar cells, rectifiers, and other solid-state devices which are used extensively in the electronics and space-age industries. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

Solid-state NMR methods have been much used to study the characteristics of the network chains themselves, particularly with regard to orientations [265], molecular motions [266], and their effects on the diffusion of small molecules [267], Aspects related to the structures of the networks include the degree of cross-linking [268,269], the distributions of cross-links [270] and stresses [271], and topologies [272,273]. Another example is the use of NMR to clarify some issues in the areas of aging and phase separation [274],... 

In a study on the thermal and UV ageing of two commercial polyfoxymethy-lene) (POM) samples, one of which was a copolymer (see related study discussed later under Section 4.3, thermogravimetric analysis (TGA)), used in car interior applications, involving both DSC and TGA, isothermal OIT measurements were made at several different temperatures [8]. One conclusion from this study was that "extrapolation of the OIT data from high temperatures (molten state) to ambient temperatures in the solid state does not reflect effective antioxidant performance at room temperature", and thus measurements close to the melting point are not appropriate for reliable lifetime estimations. 

The unbranched polymer produced by P. polycephalum and related Physarum strains has a weight average molecular weight between 40,000 and 60,000 Daltons and a polydispersity of 1.5-3.0 depending on the culture conditions and the age of the samples [111]. The acid form of poly-/ -malate does not show either a Tg or a Tm in the solid state, by DSC analysis, below its thermal decomposition temperature of 185 °C. 

In the present work, we use quantitative solid-state 13C NMR spectroscopy to study the polymerization process of multiacrylates and the effects of thermal history/aging on the free radical life in polymultiacrylates. 

Solid-state NMR spectroscopy was also used to examine the post reaction behavior of pTrMPTrA samples prepared in bulk as thin films, as described in the experimental. All of the spectra in this aging study required a minimum of 720 scans on approximately 50 mg of sample with a 100 s pulse delay to achieve adequate signal/noise. Under these conditions, reliable peak areas could be obtained from the curve fits of the carbonyl region. Figure 3 depicts the evolution of the solid state spectrum of the sample stored under N2 over time and upon heating. The area of the peak at 174 ppm for the carbonyl adjacent to the reacted double bond increases as the peak at 166 ppm for pendant unsaturation decreases. The results of the aging study are given in Table I. 

Three different forms of beryllium hydroxide in the solid state have been described (10, 52, 53, 100). The amorphous form of Be(OH)2 is obtained as a gelatinous precipitate when alkali is added to a beryllium-containing solution at ambient temperatures. The gelatinous precipitate is slowly transformed into the metastable a form when the mixture is allowed to stand. The stable fi form is obtained after the mixture has aged for some months or by precipitation at 70°C. The value of log K for the equilibrium between a and (3 forms,... 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

Elemental sihcon has some of the most important apphcations in this electronic age. One of the major apphcations is in computer chips. The single crystals of crystadine sihcon are used for solid-state or semiconductor devices. 

The EM studies show that the novel glide shear mechanism in the solid state heterogeneous catalytic process preserves active acid sites, accommodates non-stoichiometry without collapsing the catalyst bulk structure and allows oxide catalysts to continue to operate in selective oxidation reactions (Gai 1997, Gai et al 1995). This understanding of which defects make catalysts function may lead to the development of novel catalysts. Thus electron microscopy of VPO catalysts has provided new insights into the reaction mechanism of the butane oxidation catalysis, catalyst aging and regeneration. 

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