Synthesis, Structure and CVD Studies of the Group 13 Complexes [Me₂M{tfacnac}] [M = Al, Ga, In; Htfacnac = F₃CC(OH)CHC(CH₃)NCH₂CH₂OCH₃]

A family of group 13 metal dimethyl complexes of the general form [Me2M{ MeC(O)CHC(NCH2CH2OMe)CF3}] (M = Al (2), Ga (3) or In (4)) have been synthesised by reaction of the isolated free ligand (1) with the corresponding trimethyl-metal reagents. The isolated complexes (2-4) were characterised by elemental analysis, NMR spectroscopy, and the molecular structures of the complexes were determined by single crystal X-ray diffraction which reveals the compounds to be monomeric 5 coordinate complexes with coordination of the pendent ether bearing lariat in the solid state. Thermogravimetric analysis showed complexes 2-4 all to have residual masses, at 200 °C, of 2.4% or less well below the value for the respective metal oxides, and vapour pressure measurements show the indium complex (4) to be an order of magnitude less volatile (0.09 Torr at 80 oC) than the Al (2) or Ga (3) derivatives despite being isoleptic systems. Complexes 2-4 have all been investigated for their utility in the LP-MOCVD growth of the respective metal oxides in the absence of additional oxidant at 400 °C on silicon substrates

Validation of the NG-18 equations for thick walled pipelines

The applicability of the flow stress dependent NG-18 equations to thick wall pipelines such as those used to transport dense phase carbon dioxide (CO2) is demonstrated. A comparison between the components of the NG-18 equations and BS 7910 shows that the factor MT for though-wall defects and MP for part-wall defects in the NG-18 equations are very close to the reference stress solutions in BS 7910 Annex P, which are applicable to thick wall pipe. Thus, by inference, the flow stress dependent form of the NG-18 equations is also applicable to thick wall pipe. A further comparison with experimental failure data for thick wall pipes shows that the flow stress dependent NG-18 equations are applicable to wall thicknesses of up to 47.2 mm when the full-size equivalent upper shelf Charpy V-notch impact energy is at least 50 J. The results suggest that in principle, the flow stress dependent NG-18 equations may be used as limit state functions in models to calculate the failure frequency due to third party external interference, for high toughness, thick wall pipelines such as those required for dense phase CO2 pipelines

Can Limit State Design be used to Design a Pipeline Above 80% SMYS?’, OMAE

ABSTRACT This paper contains the results of a preliminary study, undertaken by C-FER and Andrew Palmer and Associates, for BP Exploration, to demonstrate the feasibility of utilizing limit states design procedures for the design of large diameter, onshore pipelines in remote areas. The objective of the study was to determine if a higher design factor can be justified than that currently specified for such a region; specifically if an increase in the basic design factor, F, from approximately 0.72 to 0.85 could be justified, thereby allowing the pipeline wall thickness to be reduced and a substantial weight saving to be achieved. The work included reliability analyses for three limit state failure scenarios: burst of undamaged pipelines, burst of corroded pipelines and burst of pipelines containing dents and gouges. Results presented show: (1) the calculated probability of rupture for a new pipe (i.e., with no damage, corrosion or other forms of deterioration); (2) the probabilities of failure for pipes containing corrosion or dent/gouge defects; and (3) the effects of a higher design pressure for each limit states scenario. The paper discusses the results, comments on the feasibility of justifying higher design factors and discusses the importance of an appropriate pipeline maintenance management system for monitoring and controlling structural integrity for the full life of a pipeline

Synthesis and characterization of fluorinated β-ketoiminate zinc precursors and their utility in the AP-MOCVD growth of ZnO:F

A novel family of zinc bis beta-ketoiminate complexes 2b-2h have been synthesized by reaction of the isolated free ligands (1a-h) with dimethylzinc. The isolated zinc complexes were characterized by elemental analysis, NMR spectroscopy, and in the case of 2b-d and 2f-h, the molecular structures of the complexes were determined by single crystal X-ray diffraction which reveals the compounds to be pseudo-octahedral 6-coordinate, monomeric homoleptic complexes in the solid state. TG analysis showed complexes 2b-f all to have residual masses at 400 °C of 10% or less, well below the value for ZnO and thus indicative of volatility. Of these systems 2b [Zn{MeC(O)CHC(NCH2CH2OMe)CF3}2] has been investigated for its utility in the AP-MOCVD growth of F –doped ZnO (ZnO:F) in the absence of additional oxidant at 400 °C on glass and silicon substrates

Tailoring precursors for deposition:synthesis structure and thermal studies of cyclopentadienyl copper(I) isocyanide complexes

We report here the synthesis and characterization of a family of copper­(I) metal precursors based around cyclopentadienyl and isocyanide ligands. The molecular structures of several cyclopentadienylcopper­(I) isocyanide complexes have been unambiguously determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis of the complexes highlighted the isopropyl isocyanide complex [(η⁵-C₅H₅)­Cu­(CNⁱPr)] (<b>2a</b>) and the <i>tert</i>-butyl isocyanide complex [(η⁵-C₅H₅)­Cu­(CN^tBu)] (<b>2b</b>) as possible copper metal chemical vapor deposition (CVD) precursors. Further modification of the precursors with variation of the substituents on the cyclopentadienyl ligand system (varying between H, Me, Et, and ⁱPr) has allowed the affect that these changes would have on features such as stability, volatility, and decomposition to be investigated. As part of this study, the vapor pressures of the complexes <b>2b</b>, [(η⁵-MeC₅H₄)­Cu­(CN^tBu)] (<b>3b</b>), [(η⁵-EtC₅H₄)­Cu­(CN^tBu)] (<b>4b</b>), and [(η⁵-ⁱPrC₅H₄)­Cu­(CN^tBu)] (<b>5b</b>) over a 40–65 °C temperature range have been determined. Low-pressure chemical vapor deposition (LP-CVD) was employed using precursors <b>2a</b> and <b>2b</b> to synthesize thin films of metallic copper on silicon, gold, and platinum substrates under a H₂ atmosphere. Analysis of the thin films deposited onto both silicon and gold substrates at substrate temperatures of 180 and 300 °C by scanning electron microscopy and atomic force microscopy reveals temperature-dependent growth features: Films grown at 300 °C are continuous and pinhole-free, whereas films grown at 180 °C consist of highly crystalline nanoparticles. In contrast, deposition onto platinum substrates at 180 °C shows a high degree of surface coverage with the formation of high-density, continuous, and pinhole-free thin films. Powder X-ray diffraction and X-ray photoelectron spectroscopy (XPS) both show the films to be high-purity metallic copper

1,8-Bis(silylamido)naphthalene complexes of magnesium and zinc synthesized through alkane elimination reactions

The reactions between magnesium or zinc alkyls and 1,8-bis(triorganosilyl)diaminonaphthalenes afford the 1,8-bis(triorganosilyl)diamidonaphthalene complexes with elimination of alkanes. The reaction between 1,8-C10H6(NSiMePh2H)2 and one or two equivalents of MgnBu2 affords two complexes with differing coordination environments for the magnesium; the reaction between 1,8-C10H6(NSiMePh2H)2 and MgnBu2 in a 1:1 ratio affords 1,8-C10H6(NSiMePh2)2{Mg(THF)2} (1), which features a single magnesium centre bridging both ligand nitrogen donors, whilst treatment of 1,8-C10H6(NSiR3H)2 (R3 = MePh2, iPr3) with two equivalents of MgnBu2 affords the bimetallic complexes 1,8-C10H6(NSiR3)2{nBuMg(THF)}2 (R3 = MePh2 2, R3 = iPr3 3), which feature four-membered Mg2N2 rings. Similarly, 1,8-C10H6(NSiiPr3)2{MeMg(THF)}2 (4) and 1,8-C10H6(NSiMePh2)2{ZnMe}2 (5) are formed through reactions with the proligands and two equivalents of MMe2 (M = Mg, Zn). The reaction between 1,8-C10H6(NSiMePh2H)2 and two equivalents of MeMgX affords the bimetallic complexes 1,8-C10H6(NSiMePh2)2(XMgOEt2)2 (X = Br 6; X = I 7). Very small amounts of [1,8-C10H6(NSiMePh2)2{IMg(OEt2)}]2 (8), formed through the coupling of two diamidonaphthalene ligands at the 4-position with concomitant dearomatisation of one of the naphthyl arene rings, were also isolated from a solution of 7

The effect of pre-strain on the fracture toughness of line pipe steel

Oil and gas pipelines are designed using recognised pipeline design codes, which typically limit the applied stresses and strains to below yield. Pipelines may be subjected to higher plastic strains before they enter service and during operation, either intentionally, as a result of the method of installation, or a requirement of the design and operation, or accidentally; examples include reeling, denting, ground movement, frost heave and earthquake loading. The material subjected to high plastic strain, or pre-strain, will have different material properties to those of the ‘virgin’ material. Plastic deformation causes work hardening; the yield strength is increased, but the strain hardening capacity and the ductility of the material are reduced. The published literature on the effects of pre-strain indicates that it has a detrimental effect on the fracture toughness of steel. Pre-strain reduces the resistance to crack initiation and crack growth, and increases the transition temperature. Therefore, pre-strain will affect the response of the material to operational loads and its resistance to defects. Conventional design practice does not explicitly consider the effect of pre-strain on the material properties. The trends towards using high strength line pipe steels, and to designing to operate at higher stresses and strains, mean that historical experience and empiricism may become inappropriate or non-conservative. The development of more accurate methods for assessing mechanical damage, to replace the existing semi-empirical methods, will require that the effects of pre-strain be explicitly considered. OUTLINE OF THE STUDY This thesis describes an investigation of the effect of static, tensile pre-strain on the fracture toughness of line pipe steels, with the objective of understanding and quantifying the effect of pre-strain on toughness. The study comprises experimental, numerical and theoretical analyses. The study has identified the reasons for the effect of pre-strain on toughness, and the properties of the virgin material that determine the severity of the effect. A model for predicting the effect of pre-strain on toughness has been developed. The material tested in the experimental study was an API 5L X80 line pipe steel. Samples of the virgin material were subject to pre-strains of approximately 2.7 percent and 6.5 percent engineering strain. The lower level of pre-strain is similar to that in a pipeline subject to frost heave, whilst the higher level of pre-strain is similar to that caused by denting. For comparative purposes, samples of the virgin material were also artificially strain aged. Tensile, notched tensile, fracture toughness (J-integral and crack tip opening displacement), and Charpy V-notch impact tests of virgin, pre-strained and strain aged material were conducted. The numerical study was based on the material and test specimen geometries considered in the experimental study. The finite element (FE) analyses were conducted using ABAQUS/Standard v6.2. Large scale, non-linear geometry effects were considered. The constitutive model assumed isotropic hardening. The effect of softening due to void growth was included using the modified Gurson-Tvergaard model of porous metal plasticity. Axi-symmetric FE analyses of the notched tensile geometries and the experimental results were used to calibrate the plane strain FE model of a compact tension test specimen. The effect of the properties of the virgin material on the reduction in toughness caused by pre-strain was investigated. A theoretical model of the effect of static, tensile pre-strain on fracture toughness was derived using the local approach to fracture. The effect of pre-strain is expressed in terms of the ratio of the fracture toughness of the pre-strained material to that of the virgin material. The HRR singularity was used to describe the stress and strain field around the crack tip. A stress-modified, critical strain-controlled model was used for ductile fracture. A critical stress-controlled model was used for cleavage (brittle) fracture. RESULTS OF THE STUDY The trends of the published data, the experimental data, the numerical analyses and theoretical model are consistent. Tensile pre-strain increases the yield and tensile strength (the yield to tensile ratio tends to unity), and reduces the strain at the tensile strength, the percentage elongation at fracture and the true fracture strain. It reduces the critical fracture toughness and the fracture initiation toughness, and reduces the tearing resistance at higher levels of pre-strain. In the experimental study, the 2.7 percent pre-strain reduced the toughness of the virgin material (expressed in terms of δm) by approximately 14 percent (average of six tests), and the 6.5 percent pre-strain reduced the toughness by approximately 30 percent (average of four tests). Reasonable agreement was obtained between the predictions of the theoretical model for ductile fracture and the test data reported here and in the published literature. The effect of tensile pre-strain on toughness can be attributed to: • the increase in the yield strength, • the decrease in the strain hardening capacity, and • the decrease in the fracture strain. This conclusion is supported by the observation that the trends in the tensile properties and toughness of strain aged material, or material subject to high strain rates, are similar to those seen in pre-strained material. Material damage, in the form of the nucleation and growth of voids during the introduction of pre-strain, is not a significant factor in the reduction in toughness caused by pre-strain. The stresses and strains around the crack tip are higher in the pre-strained material compared to the virgin material. If the fracture mechanism is ductile, the void growth rate is higher, so crack initiation and stable crack growth occur at lower applied values of J and δ. If the fracture mechanism is cleavage, the Weibull stress is higher, with similar implications for crack initiation and unstable crack growth. Consequently, the fracture toughness is reduced by pre-strain. The increase in the transition temperature caused by pre-strain can also be explained in terms of the effect of pre-strain on the stress and strain field around the crack tip. The properties of the virgin material that influence the effect of pre-strain on toughness are: • the yield strength, • the ductility, • the strain hardening behaviour, • the volume fraction of void nucleating particles, and • the transition temperature. The effect of pre-strain will be greatest when the fracture mechanism changes from ductile to cleavage, i.e. when the fracture mechanism of the virgin material is ductile, and then the pre-strained material is within the transitional region or on the lower shelf. Fracture toughness tests of different steels subject to tensile pre-strain can be compared if the test data is expressed in terms of two ratios: • the ratio of the toughness of the pre-strained material to that of the virgin material, and • the ratio of the true pre-strain to the true fracture strain (measured in a tensile test) of the virgin material. The true fracture strain can be replaced by the true strain at the tensile strength of the virgin material, albeit with an increase in the scatter of the test data. A semi-empirical relationship, based on the theoretical model, is proposed for predicting the effect of pre-strain on toughness. The relationship is expressed in terms of the true strain at the tensile strength of the virgin material. The relationship is conservative with respect to the test data reported here and in the published literature. Tensile pre-strain reduces toughness. The study has shown that the effect of pre-strain on toughness is greater for virgin materials with a low ductility (defined by the strain at the tensile strength or the fracture strain), or a low strain hardening capacity. Consequently, the effect of pre-strain on toughness will be more severe in older line pipe steels, compared to modern steels, and more severe in modern high grade line pipe steels, compared to modern low grade steels