In-situ sensing, process monitoring and machine control in Laser Powder Bed Fusion: a review

Process monitoring and sensing is widely used across many industries for quality assurance, and for increasing machine uptime and reliability. Though still in the emergent stages, process monitoring is beginning to see strong adoption in the additive manufacturing community through the use of process sensors recording a wide range of optical, acoustic and thermal signals. The ability to acquire these signals in a holistic manner, coupled with intelligence-based machine control has the potential to make additive manufacturing a robust and competitive alternative to conventional fabrication techniques. This paper presents an overview of the state-of the art of in-situ process monitoring in laser powder bed fusion processes and highlights some current limitations and areas for advancement. Also presented is an overview of real-time process control requirements, which when combined with the emergent process monitoring tools, will eventually allow for in-depth process control of the powder bed fusion process, which is essential for wide-scale industrial credibility and adoption of this technology

Kinetics and mechanism of hydrogenolysis of a ruthenium(II) acyl complex

This thesis describes the results of kinetic investigations into the hydrogenolysis of the ruthenium-acyl complex dicarbonylchloro-(norbornenoyDbis(triphenylphosphine)ruthenium(II ),RuCl(CO⋅C₇H₉) (CO) ₂-(PPh₃)₂. 2. N,N-Dimethylacetamide (DMA) and toluene solutions of 2 react with one mole equivalent of H₂ to give HRuCl(CO)₂(PPh₃)₂, 3, and the unsaturated aldehyde product C₇H₉CHO, 4. The subsequent, relatively slow hydrogenation of 4 by a further mole of H₂ to give the saturated aldehyde C₇H₁₁-CHO, 5, was found to be catalyzed by 3. A detailed kinetic study on the hydrogenolysis of 2 in DMA solvent revealed a first-order rate dependence on [Ru][sub Total] an inverse dependence on added [PPh₃], and a first- to zero-order dependence on H₂pressure. The following mechanism is proposed to account for these observations: [See Thesis for Diagram] Values of k₁ and k₋₁/k₂ have been evaluated at 65°C (k₁ = 4.6±0.5x10⁻⁵ s⁻¹ k₋₁/k₂ = 1.7±0.2) and the activation enthalpy and entropy for the k₁ step determined (ΔH[sup ‡] = 69±7 kJmole⁻¹, Δs‡ = -126+13 JK⁻¹ mole⁻¹). New, and as yet incompletely characterized, ruthenium complexes of stoichiometry "RuCl(C₆H₉)(PPh₃)₂”, 6, HRuCl(C₆H₈)(C₆H₉)(PPh₃)₂-benzene solvate", 7, and RuCl₂(C₆H₈)(PPh₃)₂, 8, have been synthesized by the reactions of 1,4-cyclohexadiene (C₆H₈) with HRuCl(PPh₃)₃⋅C₆H₆ (complexes 6 and 7), and RuCl₂ (PPh₃)₃ (complex 8), respectively. Reactions of 6, 7, and 8 in DMA with H₂ and with CO were investigated, and the organic and inorganic products identified: [See Thesis for Diagram]Science, Faculty ofChemistry, Department ofGraduat

Activation of dihydrogen by ruthenium complexes containing chelating phosphines

The previously reported synthesis of dinuclear mixed-valence ruthenium complexes of general formula Ru₂Cl₅(P-P)₂, P-P = DPPP, DPPB, 5,5-CHIRAPHOS, or R.R-DIOP, has been extended to include other diphosphines: P-P = DPPN, DPPH, rac-DPPCP, rac-DPCYCP, S,S-BDPP, R- and S-BINAP, or S-PHENOP. The complexes are prepared by the reaction of RuCl₃P₂(DMA)-DMA, P = PPh₃ or P(p-tolyl)₃, with one equivalent of the appropriate diphosphine. The H₂-reduction of Ru₂Cl₅(P-P)₂ complexes in DMA, or in toluene in the presence of an added base, affords the corresponding dimeric Ru(II) complexes [RuCl(P-P)(µ-Cl)]₂, P-P = DPPN, R- or S-BINAP, or S,S-BDPP, which have been characterised by NMR spectroscopy. The [RuCl(P-P)(µ,-Cl)]₂ complexes (Structure I) show a great propensity to form trichloro-bridged dinuclear species (Structure II) in the presence of neutral coordinating ligands (L). A series of trichloro-bridged complexes of the type [(L)(P-P)Ru-(µ-Cl)₃RuCl(P-P)] (e.g. P-P = DPPB; L = NEt₃, NHBu₂, CO, DMA, PhCN, Mel) have been isolated or studied in situ and characterised spectroscopically. The molecular structure of the DMSO analogue shows an S-bonded DMSO ligand with an unsymmetrical arrangement of the chelating DPPB ligand (cf. Structure II). [ Formulas omitted ] The reaction of [RuCl(DPPB)(µ,-Cl)]₂ with H₂ has been investigated. In benzene or toluene, in the absence of an added base, dihydrogen adds reversibly to the ruthenium dimer to give the remarkably simple molecular hydrogen complex (L = η²-H₂; Structure II); the η²-H₂ ligand (with an H-H distance of 0.86 Å as estimated by ¹H NMR variable temperature spin-lattice relaxation data; T₁(min) - 12 ms at 300 MHz) is replaceable by N2. The reaction of [RuCl(P-P)(µ-Cl)]₂, P-P = DPPB or 5,5-CHIRAPHOS, with H₂ in the presence of NEt₃ as the added base yields the corresponding trinuclear Ru(II) hydride complex, [RuHCl(P-P)]₃, along with [(NEt₃)(P-P)Ru(u-Cl)3RuCl(P-P)]. The hydride complexes had been synthesised previously, albeit in low yields (<10%), and the crystal structure of the CHIRAPHOS derivative obtained. During the present work the original synthetic procedure has been modified to obtain the desired [RuHCl(P-P)]₃ complexes in ∼50% yield. In addition, these species have been characterised completely by NMR spectroscopy. The conversion of [RuCl(P-P)-((µ-Cl)]₂ to the corresponding hydride derivative likely proceeds via deprotonation by NEt₃ of the initially formed molecular hydrogen species. Under hydrogen atmosphere, [RuHClQDPPB)]₃ breaks down to form the dinuclear derivative [(η²-H₂)(DPPB)Ru(µ-H)(µ-Cl)₂RuH(DPPB)] containing a molecular hydrogen ligand, which has been identified by ¹H NMR T₁ measurements; similar complexes, but with a nitrile ligand (MeCN or PhCN) in place of the η²-H₂, have also been observed. Alternative routes to ruthenium complexes containing only one diphosphine per Ru ("RuII(P-P)") have been investigated. Some of the trichloro-bridged derivatives (e.g. L = amine, CO; Structure II, see above) are also accessible through reactions of the mixed-phosphine complex RuCl₂(DPPB)(PPh₃) with amines and aldehydes, respectively. Studies on the reactions of RuCl₂(DMSO)₄ or [RuCl(p-cymene)-(µ,-Cl)]₂ with one equivalent of diphosphines show that the nature and the distribution of product(s) (i.e. RuCl₂(P-P)₂ vs. "RuCl₂(P-P)") are greatly influenced by the chelate size of the diphosphine. The "RuCl₂(P-P)" species is observed only for those phosphines which form at least a six-membered ring upon coordination to the metal. Solid-state ³¹P NMR studies indicate that the structure of RuCl₂(DPPB)(PPh₃) is similar to that of RuCl₂(PPh₃)₃, which has been characterised previously by X-ray crystallography. Reactions of RuCl₂(DPPB)(PPh₃) with chelating ligands afford six-coordinate complexes of the type RuCl₂(DPPB)(L-L), L-L = PPh₂Py, DPPM, or norbornadiene; the corresponding hydridochloro derivatives are obtained when the reactions are conducted under an atmosphere of H₂ in the presence of Proton Sponge®. The dimeric [RuCl(P-P)(µ-Cl)]₂ and the trinuclear [RuHCl(P-P)]₃ complexes described in this study are effective catalyst precursors for the hydrogenation of various alkene, ketone, imine, and nitrile substrates under relatively mild conditions (30-100 °C, 1-12 atm of H₂). A detailed kinetic study on the hydrogenation of styrene catalysed by [RuCl(DPPB)(µ-Cl)]₂ shows a first-order dependence of the maximum rate on catalyst concentration, a first- to zero-order dependence on styrene concentration and a zero- to first-order dependence on the H₂ pressure. A mechanism involving formation of the molecular hydrogen (η²-H₂) complex (see above) followed by hydrogen transfer to the substrate is proposed to account for the observations, and the rate constants at 30 ºC for the various steps have been determined. Preliminary data on acetophenone and benzonitrile hydrogenation shows that the trinuclear hydride complexes are an order of magnitude more effective than the corresponding dimeric precursors.Science, Faculty ofChemistry, Department ofGraduat

Fish community diversity assessment of protected Saraiyaman wetland in the Ganga River basin, India

‘Saraiyaman’ along Gandak River in the Ganges basin is a protected natural oxbow lake. In spite of the protection mecha- nism, it has been unrecognised for its habitat services to the fish community by resource managers and local dwellers. To investigate fish diversity and habitat status of Saraiyaman, exploratory surveys were conducted from April 2017 to March 2021. The analysis resulted in distribution of 58 fish species belonging to 7 orders, 20 families and 40 genera. Cypriniformes was found as the most dominant order. Out of 58 species, 7 were evaluated under Near Threatened (NT) category. The high value of Shannon diversity index (H’ = 3.50) highlighted significance of habitat offered by Saraiyaman for diverse fish spe- cies and its potential to serve as a gene pool for conservation of endemic and threatened fish species of the Ganga basin. The loss of Saraiyaman’s connection from River Gandak, increasing encroachment by cropland and climate change have resulted in water level reduction, water area shrinkage, eutrophication, infestation of aquatic weeds, degradation in habitat condition for fish community, decline in fish population, especially vulnerable catfish Wallago attu, and lack of quality fish brooders. Hence, under influence of multiple stressors, Saraiyaman is leading towards marsh and land afterwards. The baseline information generated on habitat and fish diversity status and management measures suggested in the present study will help in restoration of the function and services of Saraiyaman through existing protection mechanism by ensuring the conservation and sustainable resource utilisation for achieving the wetland-associated CBD-Sustainable Development Goals