The current state-of-the-art metal additive manufacturing (AM) process still cannot meet the high industry requirements in terms of surface roughness. In addition, there are limited ISO/ASTM standards on the post-processing of metal AM components. Considerable efforts have been made to close these current gaps and challenges for standardization. In this review, First, all the existing ISO/ASTM standards under the jurisdiction of ASTM Committee F42 on additive manufacturing technologies are briefly discussed. Second, two of the most promising additive manufacturing processes: powder bed fusion (PBF) and directed energy deposition (DED), as well as their common defects of AM components, are thoroughly reviewed. The build quality, surface finish characteristics, and dimensional integrity of the as-built AM components are still not satisfactory (i.e., Ra > 5 µm and Rz > 100 µm). Third, the review is focused on identifying potential solutions to surface-finish complex additive manufactured geometries and reduce the surface roughness to meet the industry requirements (i.e., Ra < 1 µm and Rz < 20 µm). Current state-of-the-art surface finishing techniques, their material removal mechanisms, process parameters, advantages, and limitations to post-process PBF components are discussed. The technical gaps and future perspectives in enhancing the surface quality of AM components are outlined.

Laser powder bed fused (L-PBF) components have poor surface finish quality that hinders their use in practical applications. Surface finishing the complex passages in the L-PBF components is particularly challenging. We aimed to produce a consistent surface finish on the internal passages of direct metal laser sintered (DMLS) Inconel 625 fuel nozzles-regardless of the as-built non-uniform surface-using a multi jet hydrodynamic finishing technique. We effectively harnessed the hydrodynamic intensity and surface finished the fuel injection/spray tips comprising multiple branches. We found profile and areal surface roughness reduced up to 90 % across all branches. Also, the peak height above the core surface Spk at the nozzle inlet reduced by 40-75 %. X-ray computed tomography (X-CT) inspection post-finishing showed that roundness and circularity of the injection/spray tips improved, while most critical nozzle dimensions were within the tolerance. The results lend further credence that the proposed technique: Multi jet hydrodynamic cavitation abrasive finishing (MJ-HCAF) can be used to surface-finish and deploy the L-PBF fuel nozzles in practical applications-ensuring safe implementation.

3D printing is emerging as an enabling technology for a wide range of new applications. From fundamentals point of view, the available materials, fabrication speed, and resolution of 3D printing processes must be considered for each specific application. This review provides a basic understanding of fundamentals of 3D printing processes and the recent development of novel 3D printing materials such as smart materials, ceramic materials, electronic materials, biomaterials and composites. It should be noted that the versatility of 3D printing materials comes from the variety of 3D printing systems, and all the new printers or processes for novel materials have not gone beyond the seven categories defined in ISO/ASTM standard. However, 3D printing should never be seen as a standalone process, it is becoming an integral part of a multi -process system or an integrated process of multiple systems to match the development of novel materials and new requirements of products. (C) 2017 Elsevier Ltd. All rights reserved.

This conference paper mainly comprises three parts: (1) a brief introduction to the current state of research; (2) a clear description of the additive manufacturing technique and fabrication methods; (3) a brief description of the structure-performance relationship. The idea is based on the notion that membranes with 'controlled architecture' could achieve enhanced performance, and that additive manufacturing techniques, also known as 3D printing, have a great potential in fabricating membranes with controlled architecture.

3D printing is an emerging technology and has attracted massive attention in recent years. This article focuses on the recent developments on enhancing the membrane module design with 3D printing technology. With the recent advancement of 3D printing technology, breakthroughs in fabricating novel membrane module components are expected in the near future. Improvement of 3D printing technologies in terms of resolution, materials and speed should assure the production of various membrane module components with high efficiency.

Membrane biofouling is a critical barrier for prolonged membrane operations. In the current study, silver nanocomposite osmotic membranes were fabricated to impart anti-microbial properties. The PAN–Ag nanocomposite substrates were prepared using one-step phase inversion. With additional crosslinked layer-by-layer (xLbL) assembly on the nanocomposite substrates, xLbL3.0-Ag nanocomposite osmotic membranes were obtained. At the silver nanoparticle (AgNP) loading concentration of 0.02wt.%, water permeability of xLbL3.0-Ag(0.02) nanocomposite osmotic membrane increased by 24.4% compared with the AgNP-free control. In addition, the silver nanocomposite membranes exhibited excellent anti-biofouling performances, with ~6log colony-forming units (CFU) reduction against Gram-positive Bacillus subtilis and ~5log CFU reduction against Gram-negative Escherichia coli at an AgNP loading of 0.10wt.%. Water flux reduced to 66.9% (AgNP-free control) and 88.2% (xLbL3.0-Ag(0.10) nanocomposite osmotic membrane) of their respective original values for membranes fouled by Comamonas testosteroni I2 in PRO test mode. This study presents a convenient method to synthesize nanocomposite osmotic membranes with excellent anti-biofouling property for potential use for pressure retarded osmosis (PRO). Our results provide significant implications for anti-fouling nanocomposite osmotic membrane fabrication as well as PRO fouling control.

The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4–30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores.

Internal concentration polarization (ICP) in substrate layer is one of the most critical bottlenecks of the forward osmosis (FO) process. In this study, we explored the use of metal–organic frameworks (MOFs) as a removable filler to prepare MOF-based porous matrix membranes (PMMs) for improving the mass transfer in the FO substrates and hence controlling the ICP. MOF-based porous matrix substrates (PMSs) with three different types of MOFs were prepared via phase inversion by adding MOF particles into the polyacrylonitrile (PAN) dope solution. A thin selective layer was prepared using a layer-by-layer (LbL) deposition method on top of the porous matrix FO substrate. The bond dissociation energy (BDE) between metal ions and organic linker of MOF particles played an important role for the selection of fillers of PMMs. For MOF particles with lower BDE (<~200kJ/mol), the corresponding MOF-based porous matrix FO membranes had higher membrane bulk porosity. This study shows the effect of different types of MOF particles in MOF-based porous matrix FO substrate for controlling the ICP in FO application for the first time, which provides an additional dimension for ICP control in osmotically-driven membrane processes.

Pressure-driven membranes with high porosity can potentially be fabricated by removing template, such as low water stability metal-organic frameworks (MOFs) or other nanoparticles, in polymeric matrix. We report on the use of benign MOFs as green template to enhance porosity and interconnectivity of the water treatment membranes. Significantly enhanced separation performance was observed which might be attributed to the mass transfer coefficient of the substrate layer increased in ultrafiltration (UF) application.

Silica gel (SG)-polyaciylonitrile (PAN) composite forward osmosis (FO) membranes have been synthesized and characterized in the present work. The incorporation of SG particles into the PAN support layer significantly changed its water permeability and salt rejection rate. In the range of 0.25-1.0 wt.% SG loading, water permeability of membranes were enhanced after the embedment of SG, most likely due to the both porous nature of SG and the enhanced substrate porosity. However, a reduction in both water permeability and salt rejection was observed if further increase in SG loading (2.0 wt.%), possibly as a result of the agglomeration of SG. The most permeable SG-PAN FO membrane (M1.00, with 1.0 wt.% SG loading) had a significantly higher water permeability compared to the control pure PAN FO membrane (M0.00). This membrane achieved high FO water fluxes of >100 L/m(2) h was achieved by using the 1 M MgCl2 as the draw solution (DS) and 0-10 mM NaCl as the feed solution (FS). To the best knowledge of the authors, this is the first study reporting the development and application of SG-PAN mixed matrix FO membranes (MMMs) based on layer-by-layer assembly. (C) 2014 Elsevier B.V. All rights reserved.

AbstractThe conversion of substrates bearing an aryl substituent proceeds through intramolecular 1,3‐dipolar cycloaddition of the azide substituent to the allyl moiety followed by copper‐catalyzed ring‐opening of the bicyclic product and oxidation with molecular oxygen.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A copper(II)-catalyzed reaction of alpha-azido-N-allylamide synthetic under an oxygen atmosphere resulted in the formation of 2-formyl pyrazinones. The present transformation was characterized by the following steps: 1) 1,3-dipolar cycloaddition of the azido part onto the intramolecular alkene to give bicyclic aziridine intermediates; 2) further copper(II)-catalyzed oxygenation-oxidation of the aziridines to give 2-formyl pyrazinones.

AbstractOptimized reaction condition including a Rh/Cu‐bimetallic catalyst system.

ChemInformVolume 41, Issue 43 Heterocyclic Compounds ChemInform Abstract: Copper-Catalyzed Synthesis of Azaspirocyclohexadienones from α-Azido-N-arylamides under an Oxygen Atmosphere. Shunsuke Chiba, Shunsuke Chiba Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this authorLine Zhang, Line Zhang Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this authorJian-Yuan Lee, Jian-Yuan Lee Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this author Shunsuke Chiba, Shunsuke Chiba Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this authorLine Zhang, Line Zhang Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this authorJian-Yuan Lee, Jian-Yuan Lee Div. Chem. Biol. Chem., Sch. Phys. Math. Sci., Nanyang Technol. Univ., Singapore 637371, SingaporeSearch for more papers by this author First published: 30 September 2010 https://doi.org/10.1002/chin.201043094Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume41, Issue43October 26, 2010 RelatedInformation

Additive manufacturing is an emerging advanced manufacturing technology and provides a new digital manufacturing tool with higher degree of design freedom for designer. However, there are some potential technical challenges, such as lack of part screening methodology as well as design consideration for additively manufactured components. Therefore, the main objective of this paper is to propose a part screening methodology via a two-steps approach for reducing of the weight of test chamber components used as a case study. Two designs for additive manufacturing methodologies: (1) topology optimization; (2) generative design was used to optimize components and to achieve up to 50% weight reduction. Some further design consideration and recommendations are also provided for the future applications for various industries.