Deep learning-based tomographic imaging of ECT for characterizing particle distribution in circulating fluidized bed

The gas and solids in a circulating fluidized bed (CFB) are heterogeneously dispersed and a multiscale flow regime may form both in time and space. Accurate measurement of the fluidizing process is significant for investigating the multiscale gas–solid flow characteristics and the design, optimization, and control of CFBs in various applications. This article develops a deep learning-based tomographic imaging of electrical capacitance tomography (ECT) to characterize the particle concentration distribution in a CFB. The deep tomographic imaging approach is realized through training a well-designed convolutional neural network (CNN) with the numerically built dataset. Simulation results demonstrate that the average values of the relative image errors reconstructed by CNN in the test set are 0.1110 and 0.1114 for the 60 and 100 mm pipes, respectively, which are better than the average values of 0.1819 and 0.2519 by the Landweber algorithm. With the verification of the trained model based on the prepared data can image the unseen typical flow patterns better than Landweber, it is further used to investigate the particle flow characteristics of a lab-scale CFB. Experimental results reveal that the developed deep tomographic imaging of ECT can successfully measure the fluidized particle distribution in both the 60 and 100 mm pipes, showing good prediction and generality of the designed CNN model. A flow regime transformation from “annular” flow to “core-annular” flow and pneumatic conveying is observed under the tested conditions. Besides, the flow regime would be highly affected by the fluidized gas flow rate and the initial bed height.     

3D printing of bioactive macro/microporous continuous carbon fibre reinforced hydroxyapatite composite scaffolds with synchronously enhanced strength and toughness

Continuous carbon fibre (CF) reinforced HA (CF/HA) composite scaffolds were prepared using a self-designed and manufactured 3D printer. The optimised design of nozzle structure and the tailored viscoelastic property of HA inks ensured compound extrusion of monofilament and multifilament CF with HA rod. The composite scaffolds designed using the CAD programme and sintered via a suitable process exhibited a hierarchical macro/microporous structure and contained approximately 50% HA and 50% β-TCP. The continuous CF synchronously enhanced the strength and toughness of the scaffolds. The compressive strengths of 1CF/HA and 5CF/HA were 11.4 ± 1.7 MPa and 16.3 ± 2.6 MPa, respectively, which were approximately double and triple compared with that of HA scaffolds. The fracture toughness of 1CF/HA was approximately double that of HA scaffolds and close to that of cortical bone. In vitro and in vivo studies demonstrated that 1CF/HA also had apatite formation capability and adequate bone regeneration capacity.     

Long‐term microstructural changes in solid oxide fuel cell anodes: 3D reconstruction

Microstructural changes in solid oxide fuel cell anodes after long‐term operation have been characterized by sequential sectioning with a focused ion beam, followed by scanning electron microscopy imaging and three‐dimensional reconstruction. The anodes were porous composites of Ni and Y₂O₃‐stabilized ZrO₂ (YSZ). The cells were operated at 800°C for 2, 4, and 8 kh, and at 925°C for 2 and 4 kh. For each specimen, the volume fraction, surface area, particle diameter, and tortuosity have been calculated for each phase (Ni, YSZ, and pores). The dependence of these microstructural parameters on the volume of sample analyzed was monitored; sufficiently large volumes were analyzed so as to eliminate any effect of sample volume. Gradients in volume fraction of Ni and porosity developed during fuel cell operation, with Ni fraction increasing, and pore fraction decreasing, at the electrolyte/anode interface. The magnitudes of these gradients increased with time.     

3D structure of oil droplets in hardened geopolymer emulsions

Geopolymer (GP) cements have the ability to integrate huge amounts of organic oils by direct emulsion in the fresh paste. Moreover, the oil emulsion remains stable during GP hardening. This allows to design tailored GP/oil (GEOIL) composites for an array of industrial applications. Using 3D X-ray micro-Computed Tomography (micro-CT), this research determines the spatial distribution of an industrial oil emulsion inside a GP cement (emulsification in the fresh state, imaging in the hardened state), depending on the oil volume fraction (from 5% to 60% total volume). The oil droplet size distribution, mean distance between droplets, and connectivity of the oil system are determined quantitatively.     

3D characterization of cubic boron nitride (CBN) composites used as tool material for high precision abrasive machining processes

Cubic boron nitride (CBN) composites are widely used as cutting tool materials for high precision abrasive machining processes. They are composed of super hard CBN abrasives and a softer binder. CBN abrasives are one of the hardest materials. They are embedded in the binder which can be metallic, polymeric or ceramic. The binder supports the abrasives and offers suitable toughness. The two components are consolidated by sintering processes under high pressure and temperature. Hence, abrasive particles exhibit an irregular spatial distribution in terms of size, location and orientation. In this work, X-ray computed tomography (CT scan) is used to investigate the geometrical properties of CBN abrasives in the volume regarding quantity, dimension and shape. A three-dimensional (3D) model is generated and the CBN abrasives are correspondingly characterized. The contribution includes both detailed explanation of CT scan and 3D modeling implementation, as well as quantification analysis of the key microstructural features for CBN composites.     

A biopolymer‐based 3D printable hydrogel for toxic metal adsorption from water

Herein, we describe a 3D printable hydrogel that is capable of removing toxic metal pollutants from aqueous solution. To achieve this, shear‐thinning hydrogels were prepared by blending chitosan with diacrylated Pluronic F‐127 which allows for UV curing after printing. Several hydrogel compositions were tested for their ability to absorb common metal pollutants such as lead, copper, cadmium and mercury, as well as for their printability. These hydrogels displayed excellent metal adsorption with some examples capable of up to 95% metal removal within 30 min. We show that 3D printed hydrogel structures that would be difficult to fabricate by conventional manufacturing methods can adsorb metal ions significantly faster than solid objects, owing to their higher accessible surface areas. © 2019 Society of Chemical Industry     

Shell membrane-aided synthesis of 3D porous flower-like Co2(OH)3Cl-MnO2 hybrid composites for high performance supercapacitors

Three-dimensional (3D) flower-like Co₂(OH)₃Cl-MnO₂ nanostructures were fabricated inside eggshell through a facile and effective method. Inspired by semipermeable membranes, a shell membrane was selected as an interface for ion diffusion. In specific, an eggshell with shell membrane was employed as a multifunctional reactor to separate the components of the precursor solution. OH^- ion diffusion was performed through porous eggshell membrane. The electrochemical measurements demonstrated that the hybrid composite achieves high capacitance 3.709?F/cm² at 1?mA/cm² (2061?F/g with the mass loading of 1.8?mg/cm²) and an excellent cycling stability (71% specific capacitance retained after 5000 cycle numbers), exhibiting a superior electrochemical performance compared to pure Co₂(OH)₃Cl or MnO₂. Moreover, an asymmetric supercapacitor was assembled by Co₂(OH)₃Cl-MnO₂-2 and activated carbon as positive and negative electrode, respectively (Co₂(OH)₃Cl-MnO₂-2//AC ASC), which exhibits high capacitance (134.8?F/g at 0.2?A/g), excellent energy density (42.2?W?h/kg at 150.3?W/kg), and remarkable cycling stability (80% capacitance retention after consecutive 5000 cycle numbers).     

Thiol-yne 3D Printable Polymeric Resins for the Efficient Removal of a Model Pollutant from Waters

A new 3D printable resin formulation is developed and optimized from commercially available thiol (pentaerythritol tetrakis(3-mercaptopropionate); PETMP) and alkyne (3-butyn-1-ol; BA) monomers. Printed objects are characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The extraction efficiency of the printed thiol-yne device is then investigated using a model dye – malachite green (MG). The results displayed excellent dye removal efficiency with > 95% MG removed within 5 min. The 3D-printed devices are reusable and show 100% removal over six cycles after washing with deionized water and methanol. The presence of surface hydroxyl groups derived from the BA monomer is shown to enhance dye adsorption in comparison to control materials. The printing procedure and resin formulation are robust and consistent when devices from different resin batches are compared for MG dye removal. The thiol-yne 3D printed devices demonstrated excellent dye removal (> 99%) from water samples collected from a tap and a nearby river source. The successful development of this resin provides a new thiol-yne-based resin system for stereolithography (SLA) 3D printing for the removal of organic dyes from wastewater and presents a potential for broad applications in water treatment.     

Synthesis and incorporation of rod-like nano-hydroxyapatite into type I collagen matrix: A hybrid formulation for 3D printing of bone scaffolds

Over the recent years, nanometric hydroxyapatite (HA) has gained interest as constituent of hybrid systems for bone scaffold fabrication, due to its biomimicry and biocompatibility. In this study, rod-like nano-HA particles were introduced in a type I collagen matrix to create a composite mimicking the bone composition. HA nano-rods (40−60 nm × 20 nm) were synthesised by hydrothermal method involving the use of an ammonium-based dispersing agent (Darvan 821-A) and fully characterised. The homogeneous dispersion of HA nanoparticles throughout the final hybrid formulation was achieved through their suspension in a collagen solution in presence of Darvan 821-A. The resulting homogeneous collagen/nano-HA suspension proved to be suitable for extrusion printing applications, showing shear thinning and sol-gel transition upon simil-physiological conditions. Furthermore, mesh-like structures were printed in a gelatine-supporting bath by means of a commercial bioprinter further demonstrating the potential of the designed hybrid system for the fabrication of 3D bone-like scaffolds.     

Calibration of cohesive parameters for a castable refractory using 4D tomographic data and realistic crack path from in-situ wedge splitting test

Crack propagation in an alumina castable refractory with mullite-zirconia aggregates was investigated in-situ using a wedge splitting test performed inside a laboratory tomograph. Four-dimensional (i.e., 3D space and time) data from digital volume correlation were used to investigate the influence of a realistic crack path on the simulation of the fracture process. A cohesive law was chosen, since toughening mechanisms were present, and calibrated via finite element model updating. When a straight crack path was assumed instead of the experimental crack path, a 10% higher fracture energy and a 35% higher cohesive strength were calibrated. Although the force alone could be used in the minimized cost function, the kinematic information gives valuable insight into the trustworthiness of the geometrical hypotheses assumed in the finite element model. Such framework can be applied to study nonlinear fracture processes for different materials with complex toughening mechanisms such as crack deflection or branching.     

Evaluation of the Usability of a Low-Cost 3D Printer in a Tissue Engineering Approach for External Ear Reconstruction

The use of alloplastic materials instead of autologous cartilage grafts offers a new perspective in craniofacial reconstructive surgery. Particularly for regenerative approaches, customized implants enable the surgeon to restore the cartilaginous framework of the ear without donor site morbidity. However, high development and production costs of commercially available implants impede clinical translation. For this reason, the usability of a low-cost 3D printer (Ultimaker 2+) as an inhouse-production tool for cheap surgical implants was investigated. The open software architecture of the 3D printer was modified in order to enable printing of biocompatible and biologically degradable polycaprolactone (PCL). Firstly, the printing accuracy and limitations of a PCL implant were compared to reference materials acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). Then the self-made PCL-scaffold was seeded with adipose-tissue derived stem cells (ASCs), and biocompatibility was compared to a commercially available PCL-scaffold using a cell viability staining (FDA/PI) and a dsDNA quantification assay (PicoGreen). Secondly, porous and solid patient-customized ear constructs were manufactured from mirrored CT-imagining data using a computer-assisted design (CAD) and computer-assisted manufacturing (CAM) approach to evaluate printing accuracy and reproducibility. The results show that printing of a porous PCL scaffolds was possible, with an accuracy equivalent to the reference materials at an edge length of 10 mm and a pore size of 0.67 mm. Cell viability, adhesion, and proliferation of the ASCs were equivalent on self-made and the commercially available PCL-scaffolds. Patient-customized ear constructs could be produced well in solid form and with limited accuracy in porous form from all three thermoplastic materials. Printing dimensions and quality of the modified low-cost 3D printer are sufficient for selected tissue engineering applications, and the manufacturing of personalized ear models for surgical simulation at manufacturing costs of EUR 0.04 per cell culture scaffold and EUR 0.90 (0.56) per solid (porous) ear construct made from PCL. Therefore, in-house production of PCL-based tissue engineering scaffolds and surgical implants should be further investigated to facilitate the use of new materials and 3D printing in daily clinical routine.     

Machine learning enabled integrated formulation and process design framework for a pharmaceutical 3D printing platform

The pharmaceutical manufacturing sector needs to rapidly evolve to absorb the next wave of disruptive industrial innovations—Industry 4.0. This involves incorporating technologies like artificial intelligence and 3D printing (3DP) to automate and personalize the drug production processes. This study aims to build a formulation and process design (FPD) framework for a pharmaceutical 3DP platform that recommends operating (formulation and process) conditions at which consistent drop printing can be obtained. The platform used in this study is a displacement-based drop-on-demand 3D printer that manufactures dosages by additively depositing the drug formulation as droplets on a substrate. The FPD framework is built in two parts: the first part involves building a machine learning model to simulate the forward problem—predicting printer operation for given operating conditions and the second part seeks to solve and experimentally validate the inverse problem—predicting operating conditions that can yield desired printer operation.     

In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu₂O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu₂O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu₂O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu₂O-CTAB exhibits better lithium storage performance (2.9 mAh cm^?2 at 0.5 mA cm^?2) than bare CuO/Cu₂O (1.8 mAh cm^?2 at 0.5 mA cm^?2).