scholarly journals Structured Alumina Substrates for Environmental Catalysis Produced by Stereolithography

2021 ◽  
Vol 11 (17) ◽  
pp. 8239
Author(s):  
Oscar Santoliquido ◽  
Francesco Camerota ◽  
Marco Pelanconi ◽  
Davide Ferri ◽  
Martin Elsener ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Catalytic Reduction ◽  
Combustion Engine ◽  
Periodic Structures ◽  
Three Dimensional ◽  
Precious Metals ◽  
Catalytic Efficiency ◽  
Active Phase ◽  
3D Print ◽  
3D Printed

Modern catalysts for internal combustion engine applications are traditionally constituted by honeycomb substrates on which a coating of the catalytically active phase is applied. Due to the laminar flow of the gases passing through their straight channels, these structures present low heat and mass transfer, thus leading to relatively large catalyst sizes to compensate for the low catalytic activity per unit of volume. Better conversion efficiency can be achieved if three-dimensional periodic structures are employed, because of the resulting gases’ tortuous paths. Furthermore, the increased catalytic activity implies a reduction in the overall catalyst volume, which can translate to a decreased usage of precious metals as active phase. By exploiting the ceramic Stereolithography technique (i.e., SLA) it is nowadays possible to accurately 3D print complex alumina-based lattices to be used as ceramic substrates for catalysis. In this work, closed-walls lattices consisting of a rotated cubic cell of 2 mm dimensions were designed, 3D printed via SLA and finally washcoated with V2O5-WO3-TiO2. The samples were tested for the selective catalytic reduction of NO by NH3 in a heated quartz glass reactor and the performance of the innovative 3D-printed substrate was compared with the catalytic efficiency of the conventional cordierite honeycombs.

scholarly journals Effect of Selected Commercial Plasticizers on Mechanical, Thermal, and Morphological Properties of Poly(3-hydroxybutyrate)/Poly(lactic acid)/Plasticizer Biodegradable Blends for Three-Dimensional (3D) Print

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1893 ◽  
Author(s):  
Přemysl Menčík ◽  
Radek Přikryl ◽  
Ivana Stehnová ◽  
Veronika Melčová ◽  
Soňa Kontárová ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Thermal Properties ◽  
Three Dimensional ◽  
Poly Lactic Acid ◽  
Mechanical And Thermal Properties ◽  
Modulated Differential Scanning Calorimetry ◽  
3D Print ◽  
3D Printed ◽  
Biodegradable Blends

This paper explores the influence of selected commercial plasticizers structure, which are based on esters of citric acid, on mechanical and thermal properties of Poly(3-hydroxybutyrate)/Poly(lactic acid)/Plasticizer biodegradable blends. These plasticizers were first tested with respect to their miscibility with Poly(3-hydroxybutyrate)/Poly(lactic acid) (PHB/PLA) blends using a kneading machine. PHB/PLA/plasticizer blends in the weight ratio (wt %) of 60/25/15 were then prepared by single screw and corotating meshing twin screw extruders in the form of filament for further three-dimensional (3D) printing. Mechanical, thermal properties, and shape stability (warping effect) of 3D printed products can be improved just by the addition of appropriate plasticizer to polymeric blend. The goal was to create new types of eco-friendly PHB/PLA/plasticizers blends and to highly improve the poor mechanical properties of neat PHB/PLA blends (with majority of PHB) by adding appropriate plasticizer. Mechanical properties of plasticized blends were then determined by the tensile test of 3D printed test samples (dogbones), as well as filaments. Measured elongation at break rapidly enhanced from 21% for neat non-plasticized PHB/PLA blends (reference) to 328% for best plasticized blends in the form of filament, and from 5% (reference) to 187% for plasticized blends in the form of printed dogbones. The plasticizing effect on blends was confirmed by Modulated Differential Scanning Calorimetry. The study of morphology was performed by the Scanning Electron Microscopy. Significant problem of plasticized blends used to be also plasticizer migration, therefore the diffusion of plasticizers from the blends after 15 days of exposition to 110 °C in the drying oven was investigated as their measured weight loss. Almost all of the used plasticizers showed meaningful positive softening effects, but the diffusion of plasticizers at 110 °C exposition was quite extensive. The determination of the degree of disintegration of selected plasticized blend when exposed to a laboratory-scale composting environment was executed to roughly check the “biodegradability”.

scholarly journals One-click preparation of 3D print files (*.stl, *.wrl) from *.cif (crystallographic information framework) data using Cif2VRML

2014 ◽  
Vol 29 (S2) ◽  
pp. S42-S47 ◽  
Author(s):  
Werner Kaminsky ◽  
Trevor Snyder ◽  
Jennifer Stone-Sundberg ◽  
Peter Moeck
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
New Materials ◽  
3D Print ◽  
3D Printed ◽  
Information Framework

Ongoing software developments for creating three-dimensional (3D) printed crystallographic models seamlessly from Crystallographic Information Framework (CIF) data (*.cif files) are reported. Color versus monochrome printing is briefly discussed. Recommendations are made on the basis of our preliminary printing efforts. A brief outlook on new materials for 3D printing is given.

scholarly journals Design of a Novel Three-Dimensional-Printed Two Degrees-of-Freedom Steerable Electrosurgical Grasper for Minimally Invasive Surgery

2018 ◽  
Vol 12 (1) ◽  
Author(s):  
Aimée Sakes ◽  
Kevin Hovland ◽  
Gerwin Smit ◽  
Jo Geraedts ◽  
Paul Breedveld
Keyword(s):  
Invasive Surgery ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Minimal Invasive ◽  
Activation Time ◽  
Medical Field ◽  
Active Electrode ◽  
3D Print ◽  
3D Printed ◽  
Specific Care

In current bipolar electrosurgical instruments, a high frequency electrical sinusoidal wave is passed through the patient's body from an active electrode to the return electrode to cut, coagulate, or desiccate tissues. Even though current bipolar electrosurgical instruments have proven effective in minimizing blood loss, advancement is needed to allow for improved dexterity and adaptability. With current advances in three-dimensional (3D)-print processes and its integration in the medical field, it has become possible to manufacture patient-and operation-specific instruments. In this study, we introduce the first 3D-printed steerable bipolar grasper (◻ 5 mm) for use in minimal invasive surgery. The grasper significantly improves dexterity by the addition of two planar joints allowing for ±65 deg for sideways and ±85 deg for up- and downward movement. The joints enable a significantly higher bending stiffness, 4.0 N/mm for joint 1 and 4.4 N/mm for joint 2, than that of currently available steerable instruments. The tip consists of two metallic movable jaws that can be opened and closed with angles up to 170 deg and allows for grasping and coagulating of tissues; reaching tissue temperatures of over 75 °C for an activation time of ∼5 s, respectively. In order to actuate the joint, tip, and electrosurgical system, as well as to tension the steering cables, a ring handle was designed. In summary, the 3D-printed steerable bipolar grasper provides the surgeon with electrosurgical capabilities, improved dexterity, improved stiffness, and the versatility that is needed to provide patient- and operation-specific care.

The effect of several parameters on catalytic denitrification of water by the use of H2 in the presence of O2 over metal supported catalysts

2013 ◽  
Vol 68 (10) ◽  
pp. 2309-2315 ◽  
Author(s):  
C. P. Theologides ◽  
P. G. Savva ◽  
G. G. Olympiou ◽  
N. A. Pantelidou ◽  
B. K. Constantinou ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Continuous Flow ◽  
Flow Reactor ◽  
Catalytic Reduction ◽  
Supported Catalysts ◽  
Batch Reactor ◽  
Particle Diameter ◽  
Active Phase ◽  
Reaction Selectivity ◽  
Continuous Flow Reactor

The present paper involves a detailed study of the selective catalytic reduction of nitrates in aqueous mediums by the use of H2 in the presence of O2 over monometallic and bimetallic supported catalysts. In this study, an attempt has been made to improve the denitrification efficiency (XNO3−, SN2) of several catalysts by regulating some experimental parameters that are involved in the process. Therefore, the effects of the type of reactor (semi-batch reactor vs continuous flow reactor), the nature of the active phase (Pd, Cu, and Pd-Cu) and the particle size of γ-Al2O3 spheres (particle diameter = 1.8 mm and 3 mm) on catalytic activity and reaction selectivity, as well as the adsorption capacity of γ-Al2O3 spheres for nitrates, were examined. As the review indicates, most of the research has so far been conducted on batch or semi-batch reactors. This study successfully demonstrates the benefits of using a continuous flow reactor in terms of catalytic activity (XNO3−, %) and reaction selectivity (SN2, %). Another important aspect of this study is the crucial role of bimetallic Pd-Cu clusters for the prevention of NH4+ formation. Moreover, the use of 1.8 mm diameter γ-Al2O3 spheres as a support was proved to significantly enhance the catalytic performance of bimetallic Pd-Cu catalysts towards nitrate reduction compared to 3 mm diameter γ-Al2O3 spheres. This difference may be attributed to mass (NO3−, OH−) transfer effects (external mass transfer phenomena).

Effect of Different Iron Sources on In-Situ Growth of Zeolitic Imidazolate Frameworks-8: For Efficient Oxygen Reduction Electrocatalysts

2021 ◽  
Vol 21 (10) ◽  
pp. 5319-5328
Author(s):  
Sha-Sha Luo ◽  
Yu-Meng Ma ◽  
Peng-Wei Li ◽  
Ming-Hua Tian ◽  
Qiao-Xia Li
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Oxygen Reduction ◽  
High Performance ◽  
Low Cost ◽  
Three Dimensional ◽  
Precious Metals ◽  
High Catalytic Activity ◽  
Zeolitic Imidazolate Frameworks ◽  
Wide Range

Transition metal and nitrogen co-doped carbon-based catalysts (TM-N-C) have become the most promising catalysts for Pt/C due to their wide range of sources, low cost, high catalytic activity, excellent stability and strong resistance to poisoning, especially Fe–N–C metal-organic frameworks (MOFs), which are some of the most promising precursors for the preparation of Fe–N–C catalysts due to their inherent properties, such as their highly ordered three-dimensional framework structure, controlled porosity, and tuneable chemistry. Based on these, in this paper, different iron sources were added to synthesis a sort of zeolitic imidazole frameworks (ZIF-8). Then the imidazole salt in ZIF-8 was rearranged into high N-doped carbon by high-temperature pyrolysis to prepare the Fe–N–C catalyst. We studied the physical characteristics of the catalysts by different iron sources and their effects on the catalytic properties of the oxygen reduction reaction (ORR). From the point of morphology, various iron sources have a positive influence on maintaining the morphology of ZIF-8 polyhedron. Fe–N/C–Fe(NO3)3 has the same anion as zinc nitrate, and can maintain a polyhedral morphology after high-temperature calcination. It had the highest ORR catalytic activity compared to the other four catalyst materials, which proved that there is a certain relationship between morphology and performance. This paper will provide a useful reference and new models for the development of high-performance ORR catalysts without precious metals.

scholarly journals Design and Characterization of Ag@Cu2O-rGO Nanocomposite for the p-Nitrophenol Reduction

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 43
Author(s):  
Chao Song ◽  
Shuang Guo ◽  
Lei Chen
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Catalytic Reduction ◽  
Catalytic Efficiency ◽  
Transmission Electron ◽  
Nitrophenol Reduction ◽  
Reduced Graphene ◽  
High Degree ◽  
Scanning Electron

In this paper, we designed Ag nanoparticles coated with a Cu2O shell, which was successfully decorated on reduced graphene oxide (rGO) via a solid-state self-reduction. The Cu2O, Ag@Cu2O, and Ag@Cu2O-rGO nanocomposites were synthesized and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis, and XPS to evaluate the properties of the composites. In order to compare the chemical catalytic activity, the Cu2O, Ag@Cu2O, and Ag@Cu2O-rGO nanocomposites were employed for the catalytic reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) in aqueous solution. The Ag@Cu2O-rGO nanocomposite exhibited excellent catalytic activity due to the intense interaction and high degree of electron transfer among Ag, Cu2O, and rGO. The rGO acted as the platform to bridge the isolated nanoparticles; furthermore, the electrons could quickly transfer from the Ag core to the Cu2O shell, which improved the chemical catalytic efficiency.

Analysis of the influence of polylactic acid (PLA) colour on FDM 3D printing temperature and part finishing

2018 ◽  
Vol 24 (8) ◽  
pp. 1305-1316 ◽  
Author(s):  
Juliana Breda Soares ◽  
João Finamor ◽  
Fabio Pinto Silva ◽  
Liane Roldo ◽  
Luis Henrique Cândido
Keyword(s):  
Polylactic Acid ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Fused Deposition Modelling ◽  
Process Conditions ◽  
Content Type ◽  
3D Print ◽  
Fused Deposition ◽  
3D Printed

Purpose This paper aims to analyse the effect of different polylactic acid (PLA) colours used on fused deposition modelling (FDM), considering the product finishing quality produced with the same process conditions. Design/methodology/approach The methodology adopted was to design a virtual modelling object and three-dimensional (3D) print it with FDM with different PLA colours (natural, green and black), using the same parameters. 3D scanning and scanning electron microscopy was used to analyse the model finishing of each sample. Fourier-transform infrared spectroscopy analysis, thermogravimetric analysis and dynamic mechanical analysis were used to characterize the material and verify if the colour affected its thermal behaviour. Findings Findings showed that different PLA colours lead to distinct 3D printed finishings under the same process conditions. Thermal analysis showed a reason for the printing finishing difference. The degradation temperatures and the glass temperatures vary depending on the PLA colour. This affects the FDM working temperature. Originality/value This study will contribute to improving the finishing quality of 3D printed products by collaborating to the determination of its process conditions.

scholarly journals Combining Materials Obtained by 3D-Printing and Electrospinning from Commercial Polylactide Filament to Produce Biocompatible Composites

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3806
Author(s):  
Pablo Romero-Araya ◽  
Victor Pino ◽  
Ariel Nenen ◽  
Verena Cárdenas ◽  
Francisca Pavicic ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
3D Printing ◽  
Three Dimensional ◽  
Fibrillar Structure ◽  
3D Print ◽  
3T3 Fibroblasts ◽  
Custom Made ◽  
3D Printers ◽  
3D Printed

The design of scaffolds to reach similar three-dimensional structures mimicking the natural and fibrous environment of some cells is a challenge for tissue engineering, and 3D-printing and electrospinning highlights from other techniques in the production of scaffolds. The former is a well-known additive manufacturing technique devoted to the production of custom-made structures with mechanical properties similar to tissues and bones found in the human body, but lacks the resolution to produce small and interconnected structures. The latter is a well-studied technique to produce materials possessing a fibrillar structure, having the advantage of producing materials with tuned composition compared with a 3D-print. Taking the advantage that commercial 3D-printers work with polylactide (PLA) based filaments, a biocompatible and biodegradable polymer, in this work we produce PLA-based composites by blending materials obtained by 3D-printing and electrospinning. Porous PLA fibers have been obtained by the electrospinning of recovered PLA from 3D-printer filaments, tuning the mechanical properties by blending PLA with small amounts of polyethylene glycol and hydroxyapatite. A composite has been obtained by blending two layers of 3D-printed pieces with a central mat of PLA fibers. The composite presented a reduced storage modulus as compared with a single 3D-print piece and possessing similar mechanical properties to bone tissues. Furthermore, the biocompatibility of the composites is assessed by a simulated body fluid assay and by culturing composites with 3T3 fibroblasts. We observed that all these composites induce the growing and attaching of fibroblast over the surface of a 3D-printed layer and in the fibrous layer, showing the potential of commercial 3D-printers and filaments to produce scaffolds to be used in bone tissue engineering.

Use of Three-dimensional Printing in the Development of Optimal Cardiac CT Scanning Protocols

2020 ◽  
Vol 16 (8) ◽  
pp. 967-977
Author(s):  
Zhonghua Sun
Keyword(s):  
Cardiovascular Disease ◽  
Cardiac Computed Tomography ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Aortic Diseases ◽  
Clinical Value ◽  
Three Dimensional Printing ◽  
Doctor Patient Communication ◽  
Medical Education And Training ◽  
3D Printed

Three-dimensional (3D) printing is increasingly used in medical applications with most of the studies focusing on its applications in medical education and training, pre-surgical planning and simulation, and doctor-patient communication. An emerging area of utilising 3D printed models lies in the development of cardiac computed tomography (CT) protocols for visualisation and detection of cardiovascular disease. Specifically, 3D printed heart and cardiovascular models have shown potential value in the evaluation of coronary plaques and coronary stents, aortic diseases and detection of pulmonary embolism. This review article provides an overview of the clinical value of 3D printed models in these areas with regard to the development of optimal CT scanning protocols for both diagnostic evaluation of cardiovascular disease and reduction of radiation dose. The expected outcomes are to encourage further research towards this direction.

Investigation of the Static Behavior and Failure Mechanisms of a 3D Printed Bio-Based Sandwich with Auxetic Core

2020 ◽  
Vol 12 (05) ◽  
pp. 2050051
Author(s):  
Khawla Essassi ◽  
Jean-Luc Rebiere ◽  
Abderrahim El Mahi ◽  
Mohamed Amine Ben Souf ◽  
Anas Bouguecha ◽  
...  
Keyword(s):  
Failure Mechanisms ◽  
Three Dimensional ◽  
Acoustic Emissions ◽  
Shear Stiffness ◽  
Tensile Tests ◽  
Sandwich Composite ◽  
Static Behavior ◽  
Flax Fibers ◽  
Data Points ◽  
3D Printed

In this research contribution, the static behavior and failure mechanisms are developed for a three-dimensional (3D) printed dogbone, auxetic structure and sandwich composite using acoustic emissions (AEs). The skins, core and whole sandwich are manufactured using the same bio-based material which is polylactic acid reinforced with micro-flax fibers. Tensile tests are conducted on the skins and the core while bending tests are conducted on the sandwich composite. Those tests are carried out on four different auxetic densities in order to investigate their effect on the mechanical and damage properties of the materials. To monitor the invisible damage and damage propagation, a highly sensitive AE testing method is used. It is found that the sandwich with high core density displays advanced mechanical properties in terms of bending stiffness, shear stiffness, facing bending stress and core shear stress. In addition, the AE data points during testing present an amplitude range of 40–85[Formula: see text]dB that characterizes visible and invisible damage up to failure.

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