Comparative study on the electrochemical performance of LiFePO4 cathodes fabricated by low temperature 3D printing,direct ink writing and conventional roller coating process

Electrodes for lithium-ion batteries can be fabricated in many ways including conventional roller coating and 3D printing. Roller coating is a standardized process in current lithium-ion battery industry, while 3D printing has been used to fabricate three-dimensional (3D) unconventional electrodes with tailored geometries. Our previous study proposed a low temperature 3D printing process to fabricate highly-porous LiFePO₄ (LFP) electrodes. However, there still lack a study on the comparison of electrochemical performance of LFP electrodes fabricated via the three different fabrication processes including low temperature direct writing-based 3D printing (LTDW), room temperature direct ink writing (DIW) and roller coating process. In this study, we fabricated LFP cathodes using these three fabrication processes from LFP inks with different solid contents. By varying the solid content, LFP electrodes with different geometries (including width and thickness), morphologies and porous microstructures were obtained via LTDW and DIW. Mercury porosimetry was performed to examine the differences of the three types of LFP electrodes in porous microstructures. Electrochemical performance including charge/discharge, rate performance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the three types of electrodes were measured and compared. Results showed that electrode fabrication processes have important effects on the electrochemical performance of LFP electrodes depending on the ink solid content. LTDW-fabricated electrodes had the best performance at high solid content (≥0.467 g/mL) and conventional roller coated electrodes performed better at low solid content (≤0.356 g/mL). Relationships between ink solid content, fabrication process, resulting porous microstructures and electrochemical performance were discussed. Finally, an optimal specific capacity of ∼82 mAh.g-1 @ 10C was achieved at a solid content of 0.467 g/mL by LTDW process.     

Changes to bacterial community make‐up in a two‐phase anaerobic digestion system

Changes to microbial populations in a two‐phase anaerobic digestion system were studied over 34 weeks. Numbers of autofluorescent methanogenic and non‐methanogenic bacteria decreased significantly during start‐up, but did not change markedly either in the acid reactor or the upflow anaerobic filter for the remainder of the study. Although the proportion of autofluorescent methanogens increased in the acid reactor, the numbers of viable methanogens decreased 590‐fold. The numbers of viable methanogens increased 10‐fold in the port, decreased 10‐fold in the effluent and there was almost no change in the drain of the upflow anaerobic filter. The data indicated that bacterial attachment in the upflow anaerobic filter gave a 90% COD removal and a methane yield of 0.33 m³ CH₄ kg⁻¹ COD removed at an organic loading rate of 7 kg COD m⁻³day⁻¹. Epifluorescence microscopy of the seed sludge revealed a diverse methanogenic population of equally dominant groups of medium rods and filaments with Methanococcus, short rods, long rods and Methanosarcina also present. The medium rod‐shaped species remained the most dominant group in the acid reactor. As the volatile fatty acid concentration increased in the acid reactor the number of Methanosarcina and filament species decreased, becoming the least dominant groups. At the end of the operation, Methanococcus species were the dominant group in the upflow anaerobic filter having been washed from the biofilm. © 2000 Society of Chemical Industry     

Digestion of pre‐treated food waste in a hybrid anaerobic solid–liquid (HASL) system

The hybrid anaerobic solid–liquid (HASL) system was developed to be used in industrial‐scale operations to minimize the amount of food waste for disposal in Singapore. Thermal pre‐treatment of food waste at 70 °C for 2 h (experiment E1) or at 150 °C for 1 h (experiment E2) facilitated the hydrolytic and acidogenic processes in the acidogenic reactor and methanogenesis in the methanogenic reactor in the HASL system. The highest dissolved chemical oxygen demands in the effluents from the acidogenic reactors were 17 575, 19 980 and 24 235 mg dm^?3 in the control with food waste without thermal pre‐treatment and experiments E1 and E2, respectively. The maximum concentrations of methanogens in the methanogenic reactor were 2.3 × 10⁷, 3.8 × 10⁷, 4.3 × 10⁷ cells cm^?3 for the control and experiments E1 and E2, respectively. However, the performances of the methanogenic phase in terms of specific activity of methanogens did not differ significantly for the control and experiments E1 and E2. Use of thermally pre‐treated food waste halved the time to produce the same quantity of methane in comparison with anaerobic digestion of fresh food waste. The fluorescent measurements of co‐enzyme F₄₂₀ and oligonucleotide probe Arc915 specifically bound (hybridized) with 16S rRNA were used for monitoring of methanogens during anaerobic digestion of food waste. There was a linear correlation between these parameters and the concentration of methanogens in the effluent from the methanogenic reactor. Copyright © 2005 Society of Chemical Industry     

3D printed ceramic phosphor and the photoluminescence property under blue laser excitation

An Al₂O₃/YAG: Ce³⁺ ceramic phosphor was fabricated for high-flux laser lighting using the digital lighting process (DLP)-based 3D printing method for the first time. The photocurable ceramic suspension for 3D printing was prepared by blending well-treated Al₂O₃/YAG: Ce³⁺ composite powders with photosensitive resin monomers and photo-initiators. The printing parameters, debinding and sintering processes were designed delicately to fabricated the dense sub-millimeter-sized cylinder ceramic with high dimensional accuracy. The ceramic showed excellent luminescence property under blue laser excitation with a threshold of 20.7 W/mm², higher than that prepared via dry-pressing followed by vacuum sintering. The luminescence properties and the microstructures of both ceramics were further comparatively investigated to find the possible interpretations for improvement of laser flux for the 3D-printed ceramic. The present work indicated that the new developed 3D printing method was promising for preparing luminescent ceramics for high-flux laser lighting in a rapid, effective, low-cost and precision-controlled manner.     

Study on impedance spectra of La0.7Sr0.3MnO3 and Sm0.2Ce0.8O1.9-impregnated La0.7Sr0.3MnO3 cathode in single chamber fuel cell condition

Impedance spectroscopy was used to study the electrochemical performance of pure and ion-impregnated La_0.7Sr_0.3MnO₃ (LSM) cathodes on YSZ (Y₂O₃-stabilized ZrO₂) electrolytes in single chamber fuel cell conditions, i.e. a mixture gas with oxygen as oxidant, methane as fuel and nitrogen as dilute gas. Measurements were taken at the furnace temperature range of 550-750 °C and the CH₄/O₂ ratios from 1 to 2. Polarization resistances (R_p) for pure and impregnated LSM cathodes increased obviously as the CH₄/O₂ ratio increased at 650-750 °C. Polarization resistances of Sm_0.2Ce_0.8O_1.9 (SDC) impregnated LSM cathode were much smaller than the ones of pure LSM cathode under the same conditions. Overtemperatures were occurred at both cathodes due to the partial oxidation of methane.     

3D-printed polymer packing structures: Uniformity of morphology and mechanical properties via microprocessing conditions

Three-dimensional (3D) printing is an attractive approach to fabricate highly porous extremely lightweight structures for architecture antivibrational packaging. We report 3D printing processing of model packaging structures using biodegradable poly(lactic acid) (PLA) as a source material, with acrylonitrile butadiene styrene (ABS) utilized as a common 3D printing source material as a traditional benchmarked material. The effects of printing temperature, speed, and layer morphology on the layer-by-layer 3D-printed structures and their mechanical properties were considered. Three different characteristic morphologies were identified based on printing temperature; the microscopic surface roughness was dependent on the printing speed and layer height. We demonstrate that the mechanical performances and surface properties of 3D-printed PLA structures could be improved by optimization of printing conditions. Specifically, we evaluate that these PLA-based 3D structures printed exhibited better surface qualities and enhanced mechanical performance than traditional ABS-based structures. Results showed that the PLA-based 3D structures possessed the favorable mechanical performance with 34% higher Young's modulus and 23% higher tensile strength in comparison to the ABS-based 3D structures. This study provides guidelines for achieving high-quality 3D-printed lightweight structures, including smooth surfaces and durable mechanical properties, and serves as a framework to create biodegradable 3D-printed parts for human use.     

Bioprinting of Cartilage with Bioink Based on High-Concentration Collagen and Chondrocytes

The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen.     

Alumina-based filters made via binder jet 3D printing of alumina powder,colloidal silica infiltration,and sintering

Alumina-based, porous filter media was made via a binder jet 3D printing process consisting of an alumina powder printing step with subsequent heating, colloidal silica infiltration, drying, and sintering to consolidate particles yet retain a net open porous microstructure. The composites made were alumina-silica or alumina-mullite, where the silica sintering aid was used to densify and join the alumina particles. The resulting composite structures had open porosities in the 25–31 vol% range as measured by Archimedes density. Pressure drops were measured across the filter media at constant flow rates to compare disc shapes and complex, 3D printed filters based on the N95 design requirements. Complex, 3D-printed alumina composites were produced with acceptable pressure drops for N95 implementation.     

Application of 3D-Printed,PLGA-Based Scaffolds in Bone Tissue Engineering

Polylactic acid–glycolic acid (PLGA) has been widely used in bone tissue engineering due to its favorable biocompatibility and adjustable biodegradation. 3D printing technology can prepare scaffolds with rich structure and function, and is one of the best methods to obtain scaffolds for bone tissue repair. This review systematically summarizes the research progress of 3D-printed, PLGA-based scaffolds. The properties of the modified components of scaffolds are introduced in detail. The influence of structure and printing method change in printing process is analyzed. The advantages and disadvantages of their applications are illustrated by several examples. Finally, we briefly discuss the limitations and future development direction of current 3D-printed, PLGA-based materials for bone tissue repair.     

Comparative evaluation of full‐scale UASB reactors treating alcohol distillery wastewaters in terms of performance and methanogenic activity

In this study, two full‐scale upflow anaerobic sludge blanket (UASB) reactors, namely TUASB and CUASB, at the wastewater treatment plants of the Tekirdaǧ Alcohol (Raki) and Canakkale Alcohol (Cognac) distilleries were investigated in terms of performance, acetoclastic methanogenic capacity and microbial composition. The results were compared with a previously studied other UASB reactor (IUASB) at the wastewater treatment plant of the Istanbul Alcohol (Raki) Distillery from which the two reactors (TUASB and CUASB) were seeded. The IUASB reactor performed well achieving COD removal efficiencies of no lower than 85% at organic logding rates (OLRs) in the range of 6–11 kg COD m⁻³ day⁻¹ between 1996 and 2001. During the last one year of operation, between 2000 and 2001, performance of the CUASB reactor in terms of COD removal efficiency was 70–80% at OLRs in a range of 1–4.5 kg COD m⁻³ day⁻¹ whereas it was 60–80% at OLRs in a range of 2.5–8.5 kg COD m⁻³ day⁻¹ in the TUASB reactor. At the end of year 2000, specific methanogenic activity (SMA) tests were carried out to determine potential loading capacity and optimum operating conditions of the IUASB, CUASB and TUASB reactors. The potential methane production (PMP) rates of the CUASB, IUASB and TUASB reactors were measured as 230 cm³ CH₄ gVSS⁻¹ day⁻¹, 350 cm³ CH₄ gVSS⁻¹ day⁻¹ and 376 cm³ CH₄ gVSS⁻¹ day⁻¹ respectively. When the PMP rates were compared with actual methane production (AMP) rates obtained from the three UASB reactors, AMP/PMP ratios were evaluated to be 0.18, 0.12 and 0.13 for CUASB, TUASB and IUASB reactors respectively. This showed that the CUASB, TUASB and IUASB reactors were using only 18%, 12% and 13% of their potential acetoclastic methanogenic capacity respectively. These results can be interpreted that the three UASB reactors were underloaded compared with their potential acetoclastic methanogenic capacities. It was, therefore, recommended that the three UASB reactors should be loaded at higher organic loading rates or sludge withdrawn in order to maintain an AMP/PMP ratio of 0.6–0.7, which can ensure desired reactor performance with safer operation. Results of epifluoresence microscopic examinations showed that the percentage of total autofluorescent methanogens was approximately 30% of the total population in sludges from the TUASB and IUASB reactors whereas it was 20% in sludge from the CUASB reactor. The two UASB reactors treating raki distillery wastewaters contained sludges having a higher percentage of autofluorescent methanogenic population and higher acetoclastic methanogenic activity. Copyright © 2004 Society of Chemical Industry     

Active Materials for 3D Printing in Small Animals: Current Modalities and Future Directions for Orthopedic Applications

The successful clinical application of bone tissue engineering requires customized implants based on the receiver’s bone anatomy and defect characteristics. Three-dimensional (3D) printing in small animal orthopedics has recently emerged as a valuable approach in fabricating individualized implants for receiver-specific needs. In veterinary medicine, because of the wide range of dimensions and anatomical variances, receiver-specific diagnosis and therapy are even more critical. The ability to generate 3D anatomical models and customize orthopedic instruments, implants, and scaffolds are advantages of 3D printing in small animal orthopedics. Furthermore, this technology provides veterinary medicine with a powerful tool that improves performance, precision, and cost-effectiveness. Nonetheless, the individualized 3D-printed implants have benefited several complex orthopedic procedures in small animals, including joint replacement surgeries, critical size bone defects, tibial tuberosity advancement, patellar groove replacement, limb-sparing surgeries, and other complex orthopedic procedures. The main purpose of this review is to discuss the application of 3D printing in small animal orthopedics based on already published papers as well as the techniques and materials used to fabricate 3D-printed objects. Finally, the advantages, current limitations, and future directions of 3D printing in small animal orthopedics have been addressed.     

Quantitative analysis of microbial community structure in two-phase anaerobic digesters treating food wastewater

An acidogenic reactor with a 0.5-L working volume and a methanogenic digester with a 5-L of working volume were operated for 150 days on a continuous mode to investigate the structure of a microbial community during food wastewater treatment. During the steady state of anaerobic digestion, volatile solids (VS) removal efficiency in the pilot plant was approximately 65%. The bacterial population was higher than any other methanogens detected during the entire anaerobic process and treatment of raw food wastewater. Methanomicrobiales (MMB), Methanosarcinales (MSL), and Methanobacteriales (MBT) were detected during digestion. The methanogenic population present in the acidogenic reactor was directly affected by the archaeal community in raw food wastewater. However, the shift of microbial community in the methanogenic digester was relatively gradual. The performance of methanogenic digester might be more related to the change of microbial metabolism affected by the physicochemical properties of the input substrate.     

Manufacturing of a ceramic groove part based on additive and subtractive technologies

Ceramic stereolithography Three-Dimensional (SL-3D) printing has a unique advantage in forming ceramic parts with complex shapes. However, because of the effects of the slicing layer thickness, laser spot diameter, and curing inhomogeneity, its manufacturing dimensional accuracy still lags far behind traditional processing methods. In this study, a manufacturing process based on additive and subtractive technologies was used to prepare ceramic groove parts. The manufacturing process of ceramic groove parts is composed of SL-3D printing, debinding, micro-milling, and sintering processes. In order to improve the dimensional accuracy of ceramic groove parts, a model based on shrinkage compensation and micro-milling was proposed. The dimensional change pattern in the curing phase was modelled and a shrinkage compensation method was established to control the dimensional accuracy of the finished parts. A method to characterize the micro-chipping on machined edges of the workpiece was investigated by applying a micro-milling cutter to process the 3D-printed part pre-sintered at 1150 °C. The effectiveness of the proposed dimensional accuracy control method was verified by the case study of a ZrO₂ ceramic part.     

Porous (SiCw-Si3N4w)/(Si3N4-SiC) composite with enhanced mechanical performance fabricated by 3D printing

SiC whisker and Si₃N₄ whisker-reinforced Si₃N₄-SiC ((SiC_w-Si₃N_4w)/(Si₃N₄-SiC)) composite was synthesized by 3D printing for the first time, by the combination of printed-Si-body nitridation and chemical vapor infiltration-SiC methods. The mechanical properties of the composite could be optimized through the adjustment of SiC_w content and load direction. A SiC_w content of 3?wt% was found to be the optimal scheme, and accordingly, the average bulk density increased by 22.4%, the bending strength increased by 63.6%, the compressive strength parallel to the printing layer increased by 404.8%, and the compressive strength perpendicular to the printing layer increased by 157.1%, compared with the bulks without whiskers. The enhanced mechanical performance was mainly attributed to the process of densification by CVI, and the effect of the homogeneous whiskers bridging, pull-out and deflecting crack to expend energy. The achieved indices meet the requirements for 3D-printed porous ceramic matrix composite targeted for commercial and military field applications.     

Fe3O4-nanoparticle-functionalized 3D-printed injectable microgel

Magnetic Fe₃O₄ nanoparticles have attached attention in bone tissue engineering because of their superior magnetism and great biocompatibility. However, some disadvantages such as the potential risk of agglomeration impair their applications. Here, we proposed a hybrid magnetic nanocomposite microgel by the integration of Fe₃O₄ nanoparticles and digital lighting processing (DLP) three-dimensional (3D) printing technology. The 3D-printed microgels could be precisely customized by printing the mixture of gelatin methacryloyl (GelMA) solution and polydopamine-coated Fe₃O₄ nanoparticles, in which polydopamine decoration improved the hydrophilicity and distribution of the incorporated Fe₃O₄. The degradable microgels could be injected through a 22-G needle while retaining their original shape after injection. Interestingly, the addition of Fe₃O₄ nanoparticles into GelMA solution displayed improved printing accuracy. Moreover, these magnetic microgels were biocompatible in vitro and in vivo. After induction within osteogenic medium, addition of nanoparticles upregulated the osteogenic gene expression of rat bone mesenchymal stem cells (BMSCs). In a word, this work provides a magnetic microplatform, which shows great potential in bone tissue engineering.     

An approach to monitor the real-time deformation during heat treatment of 3D-printed glass

This study suggests a tool for a better control on the sintering/crystallization of 3D-printed bioactive glass-ceramics bodies. A small cantilever in form of a bar with square cross section attached to a base and inclined 34° with the horizon, was used to monitor the viscous flow and sintering/crystallization headway of a glass-ceramic systems. 3D printing and sintering of bioactive glass-ceramics is of great interest for medical care applications. Viscous flow ensures sufficient densification of the typically low density printed green bodies, while crystallization prevents the structure from collapsing under the gravitational load. As a model system, a bioactive glass called BP1 (48.4 SiO₂, 1 B₂O₃, 2 P₂O₅, 36.6 CaO, 6.6 K₂O, 5.6 Na₂O (mol%)), which has a chemical composition based on that of ICIE16, was employed in this work. In addition, ICIE16 was used as a reference glass. The results show that the suggested design is a very promising tool to track the real-time deformation of 3D printed glass-ceramic specimens and gives a good indication for the onset of crystallization as well.     

The influence of ammonium and methods for removal during the anaerobic treatment of poultry manure

The addition of exogenous NH₄Cl to poultry manure and synthetic medium was used to study the effect of ammonia-nitrogen on the activity and composition of a methanogenic consortium. Results indicated that the production of biogas and methane was not affected by the variation in NH₄Cl concentration within the range 2–10 g dm⁻³ (0·5–2·6 g N-NH₄ dm⁻³). At higher values of ammonium (10–30 g dm⁻³ or 2–8 g N-NH₄ dm⁻³) a significant decline in both parameters (by 50–60% for biogas and 80–90% for methane) was observed. A significant decrease in the numbers of bacteria of all physiological groups (especially proteolytic and methanogenic) was observed when more than 30 g NH₄Cl dm⁻³ (7·8 g N-NH₄ dm⁻³) was added to the fermentation medium. The addition of 10% (w/v) of powdered phosphorite ore enhanced the production of biogas and methane at NH₄Cl concentrations up to 30 g dm⁻³, and also changed the composition of the methanogenic consortium. A partial recovery in the numbers of proteolytic and methanogenic bacteria coupled with the decrease in the density of sulphate-reducers was observed. High concentrations (more than 50 g dm⁻³) of NH₄Cl seemed to cause irreversible inhibition of methanogenesis which could not be eliminated by the addition of phosphorites. ©1997 SCI     

EIS study of the service life of activated cathodes for the hydrogen evolution reaction in the chlor-alkali membrane cell process

Electrochemical impedance spectroscopy (EIS) has been used, in conjunction with steady-state and voltammetric techniques, to test the service life of the following activated cathodes for the hydrogen evolution reaction (h.e.r.): thermal Pt-based cathodes with high noble metal loading, modified thermal Pt-based cathodes with low noble metal loading and composite Ni + RuO₂ cathodes of large effective area. Ni mesh electrodes were also tested for comparison, since the Pt-based electrodes were supported on Ni meshes. The service life test was especially designed to highlight the robustness of the cathodes under conditions of polarity inversion and involved a sequence of galvanostatic polarisations in the h.e.r. range (to activate the electrodes), cyclic voltammetries taking the electrodes to potentials positive enough to evolve oxygen, slow potentiodynamic sweeps (to obtain pseudo-steady-state curves, and hence Tafel plots) and EIS measurements at various potentials in the h.e.r. range.EIS and steady-state results converged to indicate the strong activity and very good stability of the modified thermal Pt-based cathodes which underwent very little degradation upon polarity inversion. Composite Ni + RuO₂ cathodes were not as active as Pt-based electrodes, but withstood polarity inversion with very limited loss of their activity.     

煤矸石矿井填充过程中微生物作用的气体研究

以义马跃进矿的长焰煤、煤矸石、矿井水为研究对象,在添加接种物的情况下,研究产气量和甲烷含量,结果表明:试验过程中产生的甲烷的碳同位素值与煤矸石的碳同位素值接近,说明煤矸石参与了微生物作用;接种物的加入量与产气量和甲烷含量密切相关。因此,在进一步研究获取、利用生物气的同时,一定要预防地下水的污染。     

3D printing of cordierite honeycomb structures and evaluation of compressive strength under quasi-static condition

Ceramic honeycombs exhibit unique mechanical properties based on engineered formulations and geometry of cells. Extrusion of formable paste through a complex honeycomb die is the commonly practiced technique for the manufacturing of honeycombs globally. Extrusion die fabrication is a complex process which necessitates sophisticated infrastructure facilities that provide high geometrical accuracy and finish to produce defect free honeycombs. Furthermore, every configuration of honeycomb requires a specific tool. Additive manufacturing (AM)/ 3D printing is a rapid prototyping technique which offers flexibility in fabrication of honeycombs with desired geometries from a virtual model directly. Further, this does not require complicated dies. In this study, viscoplastic printable cordierite raw mix paste with a shear rate exponent of 0.87 was printed into honeycombs with hexagonal, square, and triangular cells using a ram type 3D printer. The printed honeycomb samples are found to possess good integrity and near net shape after drying. Sintered 3D-printed honeycomb samples of all configurations have exhibited cordierite as a major phase along with minor phases of magnesium aluminate (MgAl₂O₄) spinel, clinoenstatite (MgSiO₃), and corundum (Al₂O₃) with sintered density of 2.41-2.48 g/cc. The samples are also subjected to compression testing under quasi-static condition. The study demonstrates 3D printing as a viable and flexible technique for rapid prototyping of honeycombs with desired configurations and engineered properties.