Liquid cooling of non-uniform heat flux of chip circuit by submicrochannels

Sumbmicrochannels have been placed on the hotspots in a non-uniform heat generated chip circuit to increase the liquid/solid interaction area and then to enhance the heat dissipation. Main microchannels width is 185µm, which is twice the width of the submicrochannels and also includes the wall thickness of 35µm, and wall height is 500µm. The chip dimension is 10mm×10mm and the hotspot is 4mm×10m. Different positions of the hotspot have been investigated e.g. upstream, middle and downstream. Uniform heat flux is 100W/cm2 while for the hot spot is 150 W/cm2. Single channel simulation reveals that the downstream hotspot gives a lower temperature of the chip circuit surface; however the upstream hotspot has more uniform temperature distribution. A special design of manifold was adopted to ensure an equal mass distribution through the microchannels

Alkali Metal Complexes of Phosphine-Borane-Substituted Benzyl Ligands and Their Application in the Synthesis of B-H\ub7\ub7\ub7Sn Stabilized Dialkylstannylenes

\ua9 2024 The Authors. Published by American Chemical Society.The benzyl-substituted phosphine-boranes PhCH2P(BH3)R2 [R = iPr (1H), Ph (2H), Cy (3H)] are accessible through either the reaction between R2PCl and PhCH2MgBr, followed by treatment with BH3\ub7SMe2 or the reaction between R2P(BH)3Li and PhCH2Br. Treatment of 1H, 2H, or 3H with nBuLi, PhCH2Na, or PhCH2K gave the corresponding alkali metal complexes [{iPr2P(BH3)CHPh}Li(THF)]2 (1Li), [{Ph2P(BH3)CHPh}Li(OEt2)2] (2Li), [{Cy2P(BH3)CHPh}Li(TMEDA)] (3Li), [iPr2P(BH3)CHPh]Na (1Na), [{Ph2P(BH3)CHPh}Na(THF)2]2 (2Na), [Cy2P(BH3)CHPh]Na(THF)0.5 (3Na), [{iPr2P(BH3)CHPh}K]∞ (1K), [{Ph2P(BH3)CHPh}K(THF)]∞ (2K), and [{Cy2P(BH3)CHPh}K.0.5PhMe]∞ (3K). X-ray crystallography revealed that, while 2Li and 3Li crystallize as monomers, 1Li and 2Na crystallize as borane-bridged dimers. The potassium complexes 1K, 2K, and 3K all crystallize with polymeric structures, in which the monomer units are linked to each other through a range of both bridging BH3 groups and multihapto interactions between the potassium cations and the aromatic rings. The reactions between two equivalents of either 1Li or 3Li and Cp2Sn gave the corresponding dialkylstannylenes [{R2P(BH3)CHPh}2Sn] [R = iPr (1Sn), Cy (3Sn)]. These compounds were isolated as mixtures of the rac and meso diastereomers. X-ray crystallography reveals that rac-1Sn and rac-3Sn crystallize as discrete monomers each exhibiting two agostic-type B-H\ub7\ub7\ub7Sn contacts

Slow proton transfer to coordinated carboxylates: studies on [Ni(O₂CR){PhP(CH₂CH₂PPh₂)₂}]⁺ (R = Et or Ph)

<div><p>The reactions between [Ni(O₂CR)(triphos)]⁺ (R = Et or Ph, triphos = PhP(CH₂CH₂PPh₂)₂) and mixtures of lutH⁺ and lut (lut = 2,6-dimethylpyridine) have been studied in MeCN at 25.0 °C using stopped-flow spectrophotometry. The kinetics and spectroscopic changes indicate an equilibrium reaction, presumably involving protonation of an oxygen site (the only sites on the complex containing lone pairs of electrons). Proton transfer is slow and comparison of the kinetic data shows that the rates are insensitive to the R substituent. Using the kinetic data, the p<i>K</i>_as of [Ni(HO₂CR)(triphos)]²⁺ (p<i>K</i>_a = 14.5) have been calculated showing that when coordinated to the {Ni(triphos)}²⁺ site, RCO₂H is about 8 p<i>K</i>_a units more acidic than the free acid. Comparison of the kinetic results on the reactions of [Ni(O₂CR)(triphos)]⁺ with mixtures of lutH⁺ and lut and those of the analogous [Ni(S₂CR)(triphos)]⁺ show that protonation at oxygen is at least 7.6 × 10³ times faster than to sulfur, and the coordinated carboxylic acid is <i>ca.</i> 8 p<i>K</i>_a units less acidic than the corresponding coordinated carboxydithioic acid.</p></div

Liquid Cooling of Non-Uniform Heat flux of Chip Circuit by Submicrochannels

Abstract -Sumbmicrochannels have been placed on the hotspots in a non-uniform heat generated chip circuit to increase the liquid/solid interaction area and then to enhance the heat dissipation. Main microchannels width is 185µm, which is twice the width of the submicrochannels and also includes the wall thickness of 35µm, and wall height is 500µm. The chip dimension is 10mm×10mm and the hotspot is 4mm×10m. Different positions of the hotspot have been investigated e.g. upstream, middle and downstream. Uniform heat flux is 100W/cm 2 while for the hot spot is 150 W/cm 2 . Single channel simulation reveals that the downstream hotspot gives a lower temperature of the chip circuit surface; however the upstream hotspot has more uniform temperature distribution. A special design of manifold was adopted to ensure an equal mass distribution through the microchannels

Mechanism of proton transfer to coordinated thiolates: Encapsulation of acid stabilizes precursor intermediate

Earlier kinetic studies on the protonation of the coordinated thiolate in the square-planar [Ni(SC6H4R′-4)(triphos)]+ (R′ = NO2, Cl, H, Me or MeO) by lutH+ (lut = 2,6-dimethylpyridine) indicate a two-step mechanism involving initial formation of a (kinetically detectable) precursor intermediate, {[Ni(SC6H4R′-4)(triphos)]⋯Hlut}2+ (KR1), followed by an intramolecular proton transfer step (kR2). The analogous [Ni(SR)(triphos)]BPh4 {R = Et, But or Cy; triphos = PhP(CH2CH2PPh2)2} have been prepared and characterized by spectroscopy and X-ray crystallography. Similar to the aryl thiolate complexes, [Ni(SR)(triphos)]+ are protonated by lutH+ in an equilibrium reaction but the observed rate law is simpler. Analysis of the kinetic data for both [Ni(SR)(triphos)]+ and [Ni(SC6H4R′-4)(triphos)]+ shows that both react by the same mechanism, but that KR1 is largest when the thiolate is poorly basic, or the 4-R′ substituent in the aryl thiolates is electron-withdrawing. These results indicate that it is both NH⋯S hydrogen bonding and encapsulation of the bound lutH+ (by the phenyl groups on triphos) which stabilize the precursor intermediate. © The Royal Society of Chemistry 2015