Microstructure formation and soldering in Sn-Ni alloys

This thesis develops the understanding of microstructure formation in binary Sn-Ni alloys during solidification and during soldering. Where past research has found metastable NixSny phases after solid-state ageing of Ni-Sn couples, it has been shown for the first time in this work that metastable NiSn4 forms in the Sn-Ni system during (i) solidification of Sn-rich Sn-Ni alloys as both a primary and a eutectic phase, (ii) soldering of Sn-Ni alloys to Ni-containing substrates as the βSn-NiSn4 eutectic and (iii) during storage of Sn-Ni electroplated couples as the interfacial intermetallic layer. It has been shown that NiSn4 is an orthorhombic phase with a superstructure closely related to oC20-NiSn4 and that NiSn4 is a metastable compound at all temperatures relevant to soldering. Furthermore, it has been shown that a second metastable phase, Ni3Sn7, forms occasionally during solidification. The research has concluded on the following reasons for NiSn4 formation: (i) NiSn4 has growth advantages over equilibrium Ni3Sn4 due to easier interface attachment kinetics; (ii) the existence of a low planar lattice disregistry (~5%) between NiSn4 and Sn results in highly reproducible low energy NiSn4/Sn orientation relationships; and (iii) Fe impurity levels typical for commercial purity solders result in FeSn2 crystals that act as heterogeneous nucleation sites for NiSn4. Investigation of Sn-Ni electroplated couples showed that the interfacial layer is metastable NiSn4 initially and that Ni3Sn4 nucleates and grows to consume the NiSn4 layer with time at temperature. A similar study on Sn-Ni solder joints showed that the interfacial layer is always Ni3Sn4. The results suggest that, in electroplated couples, metastable NiSn4 nucleates on βSn due to the low planar disregistry between the phases. In contrast, during soldering the interfacial intermetallic nucleates on the Ni substrate when the solder is liquid and the metastable NiSn4 has no nucleation advantages over equilibrium Ni3Sn4.Open Acces

The Formation of a Supply Chain Strategy for the Scientific and Technological Development of the Russian Federation Regions

There has been a substantial lag in the scientific and technological development of Russia. Supply chain strategy has become an increasingly important management tool to help organizations improve their business operations. Economic sanctions imposed by a number of countries concerning, first of all, the ban on modern technology transfer dictated the need for a fundamental revision of Russia’s model of economic development and brought the development of science and the creation of advanced technologies to the fore. The purpose of the article is to consider supply chain strategy for the scientific and technological development of Russian regions. The examples of Germany, Great Britain, the USA, and China are analyzed to summarize the advanced foreign experience and identify the features of the state management of scientific and technological development. Proposals for the formation of a strategic planning system for the scientific and technological development of Russian regions are formulated

Influence of the Southern area of the Ust-Luga commercial sea port on the channel regime of the Khabolovka river

The problem investigated in the framework of this work is devoted to the study of changes in the hydrological and channel regimes of the estuary region after the construction of the Southern Port area. The object of the study is the Khabolovka River, which flows into the Luga Bay. Based on the materials of channel surveys, the article gives a modern assessment of the general condition of the channel, presents data on manmade changes in the hydromorphological structure. After the conducted research, it was determined which consequences affecting the hydromorphological appearance of the considered section of the river have now occurred from the influence of various factors. Taking into account the performed and studied in detail analysis of riverbed transformations on the river section, it is possible to formulate the main conclusions and recommendations. As a result, a forecast of the further course and changes of the estuary area of the river is given if the necessary measures to protect against wind-wave influence are not carried out

Modeling and analysis of changes in the channel regime of the Kama river within the boundaries of 1639,0-1644,5 km during the development of the channel part of the Sidorovskoye occurrence

The problem studied in the framework of this work is devoted to issues related to the projected excavation of soil from the channel part of the Sidorovskoye sand and gravel deposit on the river. Kama. The channel part of the deposit is located at 1639.0-1644.5 km of the Nizhnekamsk sluice–mouth of the river. Vyatka, which is the upper part of the Kuibyshev reservoir. The paper presents the results of the analysis of channel reformations of the studied section of the river according to field data and hydraulic calculations performed to model the channel process in the section of the river. Kama, is located in the downstream of the N. Kamskaya HPP, taking into account the planned engineering measures related to the extraction of river alluvium from the channel open pit

2-(4,5,6,7,8,9-Hexahydro-6a-aza­phenyl­en-2-ylmethyl­ene)indan-1,3-dione

The title compound, C22H19NO2, has potential for use as a new nonlinear optical material. Mol­ecules are almost planar. One C atom of the heterocyclic ring system is disordered over two positions; the site occupancy factors are 0.6 and 0.4

Dipotassium 4,4′-(hexane-3,4-di­yl)bis­(benzene­sulfonate) dihydrate

The anion of the title compound, also called sygethin dihydrate, 2K+·C18H20O6S2 2−·2H2O, has crystallographic inversion symmetry. The K+ cation is surrounded by eight O atoms in a distorted cubic coordination geometry, forming extended K—O—S networks. There are also O—H⋯O hydrogen bonds

Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations

The conformational preference of the cyano group of the 1-cyano-1-silacyclohexane was studied experimentally by means of gas electron diffraction (GED) and dynamic nuclear magnetic resonance (DNMR) as well as by quantum chemical (QC) calculations applying high-level coupled cluster methods as well as DFT methods. According to the GED experiment, the compound exists in the gas-phase as a mixture of two conformers possessing the chair conformation of the six-membered ring and Cs symmetry while differing in the axial or equatorial position of the substituent (axial = 84(12) mol %/equatorial = 16(12) mol %) at T = 279(3) K, corresponding to an A value (Gax – Geq) of −1.0(4) kcal mol−1. Gas-phase CCSD(T) calculations predict an A value of −0.72 kcal mol−1 at 279 K. In contrast, the low-temperature 13C NMR experiments resulted in an axial/equatorial ratio of 35/65 mol % at 120 K corresponding to an A value of 0.14 kcal mol−1. An average value for ΔG#e→a = 5.6 ± 0.1 kcal mol−1 was obtained for the temperature range 110–145 K. The dramatically different conformational behaviour in the gas-phase (GED) compared to the liquid phase (DNMR) suggests a strong solvation effect. According to natural bond orbital analysis the axial conformer of the title compound is an example of stabilization of a form, which is not favored by electrostatic effects and is favored predominantly by steric and conjugation effects.A.V.B. and Yu.F.S. are grateful to the Ministry of Education and Science of Russia (State Contracts N 14.B25.31.0013) for financial support. S.A.Sh. thanks the Russian Foundation for Basic Research (Grant 14-03-0023-a). I.A., S.O.W., and N.R.J. thank the Icelandic Centre for Research (RANNIS) for financial support, Grants No 080038021 and 100040022. R.B. acknowledges support from the Icelandic Research Fund, grant no. 141218051