Delamination Fracture Related to Tempering in a High-Strength Low-Alloy Steel

The delamination or splitting of mechanical test specimens of rolled steel plate is a phenomenon that has been studied for many years. In the present study, splitting during fracture of tensile and Charpy V-notch (CVN) test specimens is examined in a high-strength low-alloy plate steel. It is shown that delamination did not occur in test specimens from plate in the as-rolled condition, but was severe in material tempered in the temperature range 500 °C to 650 °C. Minor splitting was seen after heating to 200 °C, 400 °C, and 700 °C. Samples that had been triple quenched and tempered to produce a fine equiaxed grain size also did not exhibit splitting. Microstructural and preferred orientation studies are presented and are discussed as they relate to the splitting phenomenon. It is concluded that the elongated as-rolled grains and grain boundary embrittlement resulting from precipitates (carbides and nitrides) formed during reheating were responsible for the delamination.

Design, synthesis and photodynamic antimicrobial activity of ruthenium trischelate diimine complexes

In this study, we describe, for the first time, the synthesis and photophysical and microbiological investigation of ruthenium trischelate diimine complexes designed so as to possess properties specifically suited for use in Photodynamic antimicrobial chemotherapy (PACT). Of the three compounds investigated, one ([Ru(dmob)(3)]Cl-2) has demonstrated considerable promise as a photosensitiser for use in PACT. As a result, this compound is now the subject of comprehensive chemical, toxicological and formulation studies.

The electrochemical oxidation of catechol and dopamine on platinum in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF4]): Adsorption effects in ionic liquid voltammetry

The electrochemical oxidation of catechol and dopamine has been studied at a platinum micro-electrode (10 pm diameter) in two room temperature ionic liquids (RTILs): 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BE4]). For catechol in [C(2)mim][NTf2], an electrochemically quasi-reversible oxidation peak was observed at 1.1 V vs. Pt with a back peak at 0.4 V vs. Pt. This is assigned to the two-electron oxidation of catechol to doubly protonated o-benzoquinone. Double-step chronoamperometry gave a diffusion coefficient for the catechol and the oxidised species which is 3.8 x 10(-11) m(2) s(-1) for both. For catechol in [C(4)mim][BF4], a two-electron oxidation wave was observed at 1.0 V vs. Pt with no back peak. Another peak at less positive potential was also observed at 0.6 V vs. Pt in [C(4)mim][BF4] but not in [C(2)mim][NTf2] which is assigned to the adsorption of electrochemically formed neutral o-benzoquinone on the platinum electrode. The oxidised protonated o-benzoquinone is suggested to be deprotonated by the [BF4](-) anion, but not by the [NTf2](-) anion: hence adsorption of the neutral species at the platinum electrode, not the charged species. For dopamine in both RTILs, two chemically irreversible oxidation peaks were observed at 0.75 V and 1.1 V vs. Pt, and assigned to the oxidation of dopamine to the corresponding semi-quinone and the quinone. Potential-step chronoamperometry was carried out on the oxidation waves of dopamine in [C(2)mim][NTf2] and the diffusion coefficient of species in solution was calculated to be 6.85 x 10(-12) m(2) s(-1) and confirmed that the waves corresponded to one and two electron processes. A third wave was observed at 1.8 V vs. Pt which is attributed to the oxidation of the amine group to a radical cation with likely subsequent follow up chemistry. In [C(4)mim][BF4] a peak at less positive potential was observed for dopamine, similar to catechol which is assigned to the adsorption of the neutral quinone species on the platinum electrode formed by the reaction of the removal of protons from the oxidised dopamine with the [BF4](-) anion. (C) 2009 Elsevier B.V. All rights reserved.

The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

The reduction of guanine was studied by microelectrode voltammetry in the room temperature ionic liquids (RTILs) N-hexyltriethylammonium his (trifluoromethanesulfonyl) imide [N-6.2.2.2][N(Tf)(2)], 1-butyl-3-methylimidazolium hexafluorosphosphate [C(4)mim] [PF6], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide [C(4)mpyrr][N(Tf)(2)], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C-4mim][N(TF)(2)], N-butyl-N-methyl-pyrrolidinium dicyanamide [C(4)mpyrr][N(NC)(2)] and tris(P-hexyl)-tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P-14,P-6,(6,6)][FAP] on a platinum microelectrode. In [N-6,N-2,N-2,N-2][NTf2] and [P-14,P-6,P-6.6][FAP], but not in the other ionic liquids studied, guanine reduction involves a one-electron, diffusion-controlled process at very negative potential to produce an unstable radical anion. which is thought to undergo a dimerization reaction, probably after proton abstraction from the cation of the ionic liquid. The rate of this subsequent reaction depends on the nature of the ionic liquid, and it is faster in the ionic liquid [P-14,P-6,P-6.6[FAP], in which the formation of the resulting dimer can be voltammetrically monitored at less negative potentials than required for the reduction of the parent molecule. Adenine showed similar behaviour to guanine but the pyrimidines thymine and cytosine did not; thymine was not reduced at potentials less negative than required for solvent (RTIL) decomposition while only a poorly defined wave was seen for cytosine. The possibility for proton abstraction from the cation in [N-6,N-2,N-2,N-2],[NTF2] and [P-14,P-6,P-6.6][FAP] is noted and this is thought to aid the electrochemical dimerization process. The resulting rapid reaction is thought to shift the reduction potentials for guanine and adenine to lower values than observed in RTILs where the scope for proton abstraction is not present. Such shifts are characteristic of so-called EC processes where reversible electron transfer is followed by a chemical reaction. (C) 2009 Elsevier B.V. All rights reserved.

Platinum resistant cancer cells conserve sensitivity to BH3 domains and obatoclax induced mitochondrial apoptosis

Resistance to cisplatin chemotherapy remains a major hurdle preventing effective treatment of many solid cancers. BAX and BAK are pivotal regulators of the mitochondrial apoptosis pathway, however little is known regarding their regulation in cisplatin resistant cells. Cisplatin induces DNA damage in both sensitive and resistant cells, however the latter exhibits a failure to initiate N-terminal exposure of mitochondrial BAK or mitochondrial SMAC release. Both phenotypes are highly sensitive to mitochondrial permeabilisation induced by exogenous BH3 domain peptides derived from BID, BIM, NOXA (which targets MCL-1 and A1), and there is no significant change in their prosurvival BCL2 protein expression profiles. Obatoclax, a small molecule inhibitor of pro-survival BCL-2 family proteins including MCL-1, decreases cell viability irrespective of platinum resistance status across a panel of cell lines selected for oxaliplatin resistance. In summary, selection for platinum resistance is associated with a block of mitochondrial death signalling upstream of BAX/BAK activation. Conservation of sensitivity to BH3 domain induced apoptosis can be exploited by agents such as obatoclax, which directly target the mitochondria and BCL-2 family.

Deformation of titanium alloy Ti-6Al-4V under dynamic compression

Deformation localisation is the main reason for material failure in cold forging of titanium alloys and is thus closely related to the production yield of cold forging. In the study of the influence of process parameters on dynamic compression, considering material constitutive behaviour, physical parameters and process parameters, a numerical dynamic compression model for titanium alloys has been constructed. By adjusting the process parameters, the severity of strain localisation and stress state in the localised zone can be controlled thus enhancing the compression performance of titanium alloys.

Relationship between microstructure and deformation behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy

The relationship between microstructure and deformation and damage behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy has been studied using several experimental techniques, including optical microscopy, scanning electron microscopy and microhardness measurements. It was found that the deformation behaviour during dynamic compression was closely related to deformation parameters. After dynamic deformation, the deformation shear band that formed in the titanium alloy had microhardness similar to that of the matrix. However, the microhardness of the white shear band was much higher than the matrix microhardness. The effects of deformation parameters, including deformation rate and deformation degree, on deformation localisation were investigated. Based on the results from the present work, the microstructure and deformation processing parameters can be optimised. In addition, treatment methods after dynamic compression were explored to restore alloy properties. Using post-deformation heat treatment, the microstructure and property inhomogeneity caused by shear bands could be largely removed.

Origin of Low CO2 Selectivity on Platinum in the Direct Ethanol Fuel Cell

Calculated answer: First-principles calculations have been applied to calculate the energy barrier for the key step in CO formation on a Pt surface (see picture; Pt blue, Pt atoms on step edge yellow) to understand the low CO2 selectivity in the direct ethanol fuel cell. The presence of surface oxidant species such as O (brown bar) and OH (red bar) led to an increase of the energy barrier and thus an inhibition of the key step. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Platinum(II) phosphine and orotate complexes with aminopyridine co-ligands, and their molecular recognition via hydrogen bonding

The new complexes [Pt(dppp)(py)(2)][OTf](2), 1, [Pt(dppp)(2-ap)(2)][OTf](2), 2, [(dppp)Pt(mu -OH){mu -NH(C5H3N)NH2}Pt(dppp)][OTf](2), 3 (py=pyridine, 2-ap=2-aminopyridine, NH(C5H3N)NH2=2,6-diaminopyridine anion, dppp = 1,3-bis(diphenylphosphino)propane, OTf=O3SCF3) have been prepared via reactions between [Pt(dppp)(OTf)(2)] and pyridine, 2-aminopyridine or 2,6-diaminopyridine (2,6-dap) respectively. The amines exhibit a range of co-ordination modes. Pyridine and 2-aminopyridine co-ordinate to platinum through endo-nitrogen atoms in complexes 1 and 2, the latter existing as a pair of rotomers due to the steric hindrance introduced by the 2-substituent. However, 2,6-diaminopyridine co-ordinates to platinum through the exo-nitrogen of one amino group, to give the unusual mu -amido complex 3. Reaction of the known orotate chelate complex [Pt(PEt3)(2)(N,O-HL)] [HL=orotate, the dianion of 2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid (orotic acid)] with 2,6-dap gave [Pt(PEt3)(2)(2,6-dap)(N-HL)] 4, which contains an unconventional monodentate orotate ligand. In this co-ordination mode the orotate retains an ADA hydrogen bonding site and was found to co-crystallise with 2,6-dap via complementary ADA:DAD triple hydrogen bonds to give [Pt(PEt3)(2)(N-HL)(2,6-dap)].2,6-dap, 5. Complex 5 exhibits a helical chain structure of associated [1+1] adducts in the solid state.

Synthesis and characterisation of new platinum-acetylide complexes containing diimine ligands

A new class of platinum-bipyridyl compounds has been synthesized by the dehydrohalogenative reaction of [4,4'-bis(tert-butyl)-2,2'-bipyridyl]platinum dichloride [PtCl2((t)Bu(2)bipy)] 1 with terminal alkynes HC=CR, in the presence of copper(I) iodide and diisopropylamine. The products [Pt(C=CR)(2)((t)Bu(2)bipy)] (R=C6H4NO2-p 2, C6H5 3, C6H4CH3-p 4 or SiMe3 5), have been characterised by spectroscopic and analytical methods, and a single crystal molecular structure determination has been carried out on 4. Extended Huckel molecular orbital calculations have also been carried out, and the results are used to help rationalise the voltammetric, EPR and spectroelectrochemical properties of the new compounds. These show that compounds 3, 4 and 5 undergo a one-electron bipyridyl based redox process, but that 2 has an unresolved two-electron process located on the nitro groups.

Sequential C-H and C-Ru bond formation and cleavage during the thermally induced rearrangement of aryl ruthenium(II) complexes with [C6H3(CH2NMe2)(2)-2,6](-) as a bidentate eta(2)-C,N coordinated ligand. The crystal structures of the isomeric pairs [RuCl{eta(6)-C10H14}{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,n}] (n = 4 or 6) and [Ru(eta(5)-C5H5){(eta(2)-C,N-C6H3(CH2NMe2)(2)-2,n} (PPH3)] (n = 4 or 6)

New air-stable ruthenium(II) complexes that contain the aryldiamine ligand [C6H3(CH2-NMe2)(2)-2,6](-) (NCN) are described. These complexes are [RuCl{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,6}(eta(6)-C10H14)] (2; C10H14 = p-cymene = C6H4Me-Pr-i-4), [Ru{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,6}(eta(5)-C5H5)(PPh3)] (5), and their isomeric forms [RuCl{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,4}(eta(6)-C10H14)] (3) and [Ru{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,4}(eta(5)-C5H5)(PPh3)] (6), respectively. Complex 2 has been prepared from the reaction of [Li(NCN)](2) with [RuCl2(eta(6)-C10H14)](2), whereas complex 5 has been prepared by the treatment of [RuCl{eta(3)-N,C,N-C6H3(CH2NMe2)(2)-2,6}(PPh3)] (4) with [Na(C5H5)](n). Both 2 and 5 are formally 18-electron ruthenium(II) complexes in which the monoanionic potentially tridentate coordinating ligand NCN is eta(2)-C,N-bonded, In solution (halocarbon solvent at room temperature or in aromatic solvents at elevated temperature), the intramolecular rearrangements of 2 and 5 afford complexes 3 and 6, respectively. This is a result of a shift of the metal-C-aryl bond from position-1 to position-3 on the aromatic ring of the NCN ligand. The mechanism of the isomerization is proposed to involve a sequence of intramolecular oxidative addition and reductive elimination reactions of both aromatic and aliphatic C-H bonds. This is based on results from deuterium labeling, spectroscopic studies, and some kinetic experiments. The mechanism is proposed to contain fully reversible steps in the case of 5, but a nonreversible step involving oxidative addition of a methyl NCH2-H bond in the case of 2. The solid-state structures of complexes 2, 3, 5, and 6 have been determined by single-crystal X-ray diffraction. A new dinuclear 1,4-phenylene-bridged bisruthenium(II) complex, [1,4-{RuCl(eta(6)-C10H14)}(2){C-6(CH2NMe2)(4)-2,3,5,6-C,N,C',N'}] (9) has also been prepared from the dianionic ligand [C-6(CH2NMe2)(4)-2,3,5,6](2-) (C2N4). The C2N4 ligand is in an eta(2)-C,N-eta(2)-C',N'-bis(bidentate) bonding mode. Compound 9 does not isomerize in solution (halocarbon solvent), presumably because of the absence of an accessible C-aryl-H bond. Complex 9 could not be isolated in an analytically pure form, probably because of its high sensitivity to air and very low solubility, which precludes recrystallization.

Platinum bis-acetylide complexes with the 4,4'-dimethyl-2,2'-bipyridyl ligand

[Pt(Me(2)bipy)Cl-2](Me(2)bipy = 4,4'-dimethyl-2,2'-bipyridine) and HC=CC6H4-4-R react in the presence of diisopropylamine and CuI as catalyst to give the platinum bis-acetylides [Pt(Me(2)bipy)(C=CC6H4-4-R)(2)] R = H, Me, NO2. Initial spectroscopic, electrochemical and reactivity studies are presented. (C) 1997 Elsevier Science S.A.

Double cyclometalation via carbon-silicon bond cleavage by palladium(II) acetate. X-ray structure of a cationic 1,4-dipalladated benzene ring and selective synthesis of heterobimetallic 1,4-phenylene-bridged platinum(II)-palladium(II) complexes

The disilylated compound 1,4-bis(trimethylsilyl)-2,3,5,6-tetrakis((dimethylamino)methyl)benzene, (Me(3)Si)(2)C2N4, 4, can be electrophilically palladated selectively at the C-Si bonds to afford the neutral 1,4-bis(palladium) complex [(AcOPd)(2)(C2N4)], from which the dicationic [(LPd)(2)(C2N4)](2+) (L = MeCN) organometallic species are accessible. The monosilylated species (Me(3)Si)(H)C2N4, 5, can be used for the preparation of the dicationic heterodinuclear platinum(II)-palladium(II) species [(LPd)(LPt)(C2N4)](2+) (L = MeCN) via a sequence of transmetalation of the organolithium derivative of 5 with [PtCl2(SEt(2))(2)], followed by a C-Si bond palladation reaction.