Substrate and material transfer effects on the surface chemistry and texture of diamond-like carbon deposited by plasma enhanced CVD
Diamond-like carbon (DLC), a thin amorphous carbon film, has many uses in tribological systems. Exploiting alternative substrates and interlayers can enable control of the hardness and modulus of the multi-layer system and improve wear or friction properties. We utilise XPS and AFM to examine DLC concurrently coated on an epoxy interlayer and a steel substrate by plasma enhanced chemical vapour deposition (PECVD). sp 2 /sp 3 ratios were calculated both by deconvolution of the XPS C1s line and analysis of the C KLL Auger spectrum. Altering the substrate causes changes in the carbon bonding configuration, evident with the same trend through both analysis methods, though with differing absolute values, related to hydrogen and oxygen content. There is significant variation in the microscale surface texture, exhibited both by average roughness values and size and uniformity of surface asperities. This suggests that alteration to the film surface structure is a factor to be considered in addition to interface adhesion, hardness and elastic modulus, in investigating substrates and interlayers for tribological coatings. Examination of a DLC film separately produced on a steel substrate, in comparison with that produced concurrently with DLC coating of epoxy, shows the possibility of effects on the chemistry of the film through transfer of material from adjacent samples within the plasma deposition, related to heating, out-gassing or sputtering processes. The possibility of such contamination has implications in coating parameter design and coating of multiple samples with PECVD.
Coatings and surface treatments for enhanced performance suspensions for future gravitational wave detectors
Further improvements in the low frequency sensitivity of gravitational wave detectors are important for increasing the observable population of astrophysical sources, such as intermediate mass compact black hole binary systems. Improvements in the lower stage mirror and suspension systems will set challenging targets for the required thermal noise performance of the cantilever blade springs, which provide vertical softness and, thus, isolation to the mirror suspension stack. This is required due to the coupling between the vertical and horizontal axes due to the curvature of the Earth. This can be achieved through use of high mechanical Q materials, which are compatible with cryogenic cooling, such as crystalline silicon. However, such materials are brittle, posing further challenges for assembly/jointing and, more generally, for long-term robustness. Here, we report on experimental studies of the breaking strength of silicon at room temperature, via both tensile and 4-point flexural testing; and on the effects of various surface treatments and coatings on durability and strength. Single- and multi-layer DLC (diamond-like carbon) coatings, together with magnetron-sputtered silica and thermally-grown silica, are investigated, as are the effects of substrate preparation and argon plasma pre-treatment. Application of single- or multi-layer DLC coatings can significantly improve the failure stress of silicon flexures, in addition to improved robustness for handling (assessed through abrasion tests). Improvements of up to 80% in tensile strength, a twofold increase in flexural strength, in addition to a 6.4 times reduction in the vertical thermal noise contribution of the suspension stack at 10 Hz are reported (compared to current Advanced LIGO design). The use of silicon blade springs would also significantly reduce potential ‘crackling noise’ associated with the underlying discrete events associated with plastic deformation in loaded flexures.
A Historical Introduction to the Law of Obligations
1 PROLOGUE: THE PREHISTORY OF THE ENGLISH LAW OF OBLIGATIONS 2 STRUCTURAL FOUNDATIONS 3 UNITY AND FRAGMENTATION OF THE MEDIAEVAL LAW OF CONTRACT 4 TRESPASS, TRESPASS ON THE CASE, AND THE MEDIAEVAL LAW OF TORT 5 THE SUBSTANTIVE LAW OF TORTS 6 THE SUBSTANTIVE LAW OF CONTRACT PART 2 THE TRIUMPH OF TRESPASS ON THE CASE 7 TORT, PROPERTY, AND REPUTATION: THE EXPANSION OF THE ACTION ON THE CASE 8 THE RISE OF THE ACTION OF ASSUMPSIT PART 3 THE MODERN LAW OF TORT AND CONTRACT 9 TRESPASS, CASE, AND THE MORAL BASIS OF LIABILITY 10 THE LAW OF TORTS IN THE NINETEENTH CENTURY: THE RISE OF THE TORT OF NEGLIGENCE 11 THE LAW OF TORTS IN THE TWENTIETH CENTURY: EXPANSION AND COLLAPSE OF THE TORT OF NEGLIGENCE 12 FOUNDATIONS OF THE MODERN LAW OF CONTRACT 13 THE RISE OF THE WILL THEORY THE WILL THEORY AND THE CLASSICAL MODEL OF CONTRACT 14 THE DECLINE OF THE WILL THEORY: LEGAL REGULATION AND CONTRACTUAL FAIRNESS PART 4 UNJUST ENRICHMENT 15 UNJUST ENRICHMENT 16 LEGAL CHANGE AND LEGAL CONTINUITY