In this work, a stereolithography-based method of 3D printing was successfully used to fabricate a complex-shaped triangular zirconia cutting tool with a tool withdrawal groove and a honeycomb ...ceramic component. The sintered bodies displayed significant shrinkage after sintering, with the maximum shrinkage being 35.26%. The XRD pattern indicated that the crystalline phase of the parts was the t-ZrO2 phase, while SEM characterization revealed that the sintered bodies were composed of densely packed submicron-grade grains, without any discernible pores. The density of the parts was measured as 97.14% via Archimedes’ water displacement method, which is consistent with the results of SEM characterization. Additionally, the measured Vickers hardness and fracture toughness of the fabricated parts were 13.0597GPa and 6.0380MPam1/2, respectively. These values are close to the structural properties of common zirconia ceramics prepared by conventional approaches. Hence, a novel DLP-stereolithography-based 3D printing process for the fabrication of complex and dense zirconia ceramic parts has been proposed in this work.
We report a novel approach to fabricate dense zirconia-toughened alumina (ZTA) ceramics with excellent properties via an additive manufacturing process based on stereolithography. The XRD patterns ...show the ZTA sample consists of α-Al2O3 and t-ZrO2 with the dominance of α-Al2O3. The zirconia grain with the average size of 0.35µm is small enough to trigger the toughening behavior of zirconia in the ZTA. The prepared ceramics showed a density, Vickers hardness, bending strength, and fracture toughness of 4.26g/cm3, 17.76GPa, 530.25MPa, and 5.72MPam1/2, respectively. These properties are comparable to those for ceramics obtained through conventional ceramic processing.
In this study, Al2O3 ceramics were printed by stereolithography from particles with different particle size distributions, which are the micro-sized Al2O3, nano-sized Al2O3, and a mixture of both. ...The influence of the particle size and the debinding method on the density and morphology of the sintered bodies were investigated. The density of the samples containing both micro-sized and nano-sized alumina particles is highest among the three samples. Furthermore, the samples subjected to the vacuum debinding showed a higher density compared with the samples subjected to the traditional thermal debinding. The results suggest that the combination of a powder with a bimodal particle size distribution and the vacuum debinding process offers an effective way to print 3D ceramics with a good performance through stereolithography.
A dense defect-free alumina cutting tool was fabricated via stereolithography process. Different drying processes and debinding profiles were then tested and compared to find the optimal way for the ...preparation of the sintered body. The experimental results showed that using PEG400 as a liquid desiccant results in a lower deformation of the body compared to the natural drying process. Compared with vacuum debinding or air debinding, a two-step debinding process, which consisted of both a vacuum pyrolysis step and the following air debinding, is allowed to control the pyrolysis rate while suppressing the formation of defects in the alumina body. After optimization of the postprocessing, the relative density of the sample as high as 99.3%, and the Vickers hardness ∼17.5GPa. These properties are similar to the properties of alumina bodies prepared via the conventional shaping method.
Ulcerative colitis (UC) is an inflammatory disease of the digestive tract. Rauwolfia polysaccharide (Rau) has therapeutic effects on colitis in mice, but its mechanism of action needs to be further ...clarified. In the study, we explored the effect of Rau on the UC cell model induced by Lipopolysaccharide (LPS).
We constructed a UC cell model by stimulating HT-29 cells with LPS. Dextran sodium sulfate (DSS) was used to induce mice to construct an animal model of UC. Subsequently, we performed Rau administration on the UC cell model. Then, the therapeutic effect of Rau on UC cell model and was validated through methods such as Cell Counting Kit-8 (CCK8), Muse, Quantitative real‑time polymerase chain reaction (RT-qPCR), Western blotting, and Enzyme-linked immunosorbent assay (ELISA).
The results showed that Rau can promote the proliferation and inhibit the apoptosis of the HT-29 cells-induced by LPS. Moreover, we observed that Rau can inhibit the expression of NOS2/JAK2/STAT3 in LPS-induced HT-29 cells. To further explore the role of NOS2 in UC progression, we used siRNA technology to knock down NOS2 and search for its mechanism in UC. The results illustrated that NOS2 knockdown can promote proliferation and inhibit the apoptosis of LPS-induced HT-29 cells by JAK2/STAT3 pathway. In addition, in vitro and in vivo experiments, we observed that the activation of the JAK2/STAT3 pathway can inhibit the effect of Rau on DSS-induced UC model.
In short, Rauwolfia polysaccharide can inhibit the progress of ulcerative colitis through NOS2-mediated JAK2/STAT3 pathway. This study provides a theoretical clue for the treatment of UC by Rau.
•The results show that although the increased vertical stress, fracture surface roughness and intersection angle will increase the flow resistance, the temperature of fracture fluid will rise ...faster.•On the contrary, the increase of injection pressure will expand the fracture aperture and lead to the temperature of the fracture fluid rises slowly.•In addition, not all fractures contribute to the productivity of the hot dry rocks (HDRs) type of reservoirs, while only the interconnected fractures are effective.•The flow rate of production will increase when fracture density increases under the condition of connecting the injection well and production well, but the production temperature will decrease.•The relative importance of the individual parameter alone is not enough to directly measure the optimal engineering parameters, so considering the impact of multiple parameters comprehensively is crucial for EGS project development and directly affects its commercial viability.
In order to efficiently exploit geothermal energy, the reasonable configuration of fracture network should ensure the minimum water loss, high flow rate, high production temperature, and good connectivity between injection wells and production wells. To achieve the above objectives, the operating parameters of the EGS project should be balanced with the reservoir characteristics. In this paper, the THM coupling model is established in the finite element solver, which analyzes the influence of formation stress, injection pressure, roughness of fracture surface, fracture intersection angle, and fracture connectivity on fluid seepage pressure and outlet temperature. The accuracy of the model was verified by comparison to analytical solutions. The results show that although the increased vertical stress, fracture surface roughness and intersection angle will increase the flow resistance, the temperature of fracture fluid will rise faster. On the contrary, the increase of injection pressure will expand the fracture aperture and lead to the temperature of the fracture fluid rises slowly. In addition, not all fractures contribute to the productivity of the hot dry rocks (HDRs) type of reservoirs, while only the interconnected fractures are effective. The flow rate of production will increase when fracture density increases under the condition of connecting the injection well and production well, but the production temperature will decrease. The relative importance of the individual parameter alone is not enough to directly measure the optimal engineering parameters, so considering the impact of multiple parameters comprehensively is crucial for EGS project development and directly affects its commercial viability.
Projection based stereolithography (pSL) is widely applied to fabricate complicated ceramic parts. The preparation of ceramic suspension is critical for the process, especially, since large ...refractive index difference between ceramic and photosensitive resin would lead to an intense light scattering. In this paper, a ball-milling method is used to coat ZrO2 with paraffin that has a similar refractive index to that of resin, and the coated layer is measured to be around 10 nm. The modified ZrO2 is characterized by IR and TEM, and the photocuring behaviors are also investigated in terms of cure depth and excess cure width. The cure depth of modified ZrO2 increases by13.2% and 16.8% compared to the one without coating. At the same time, the excess cure width decreases by 77.1% and 62.7% using the same projection time. Moreover, ceramic ring prepared with the modified ZrO2 has a shrinkage of about 27.2%, and a density of 91.8%, smaller than the one prepared with ZrO2 without coating due to a burnout of paraffin. In conclusion, the paraffin coating layer could reduce the light scattering and thus improve the curing performance of ZrO2 suspension，especially, the excess cure width.
For four-wheel independent drive intelligent vehicle, the Model Predictive Control (MPC) is adopted to design the trajectory tracking controller through active steering and four-wheel independent ...drive/brake. The control objective is to follow a desired trajectory while taking into account the control actuator constraints and vehicle dynamic stability constraints. To reduce the computational complexity, a linear time-varying model predictive controller is designed to linearize the nonlinear vehicle model locally at each sampling point. The co-simulation of CarSim/Simulink shows that the designed controller has high tracking accuracy on the basis of ensuring vehicle stability and strong robustness to vehicle velocity and road adhesion coefficient. The trajectory tracking accuracy based on MPC is better than that of the preview driver model (PDM).
Silicon nitride (Si3N4) ceramics offer excellent thermal, mechanical and dielectric properties, which make Si3N4 a good candidate material for an application as electronic packaging material. For an ...application as a heat dissipation substrate, most studies focused on achieving a high thermal conductivity through long-time heat preservation and different kinds of heat treatments. Very few studies also considered the mechanical and dielectric properties. In addition, there have not been systematic researches about influence of additives concentration and type on the combination properties of Si3N4. Therefore, in this study, Si3N4 ceramic samples were prepared via hot pressing at 1800°C with a relatively short heat preservation step (2h), with different amounts of Y2O3 added as sintering additive. The effect of the initial concentration of the rare earth oxide on the chemical composition, microstructure, thermal conductivity, as well as the mechanical and dielectric properties of the Si3N4 ceramic samples was systematically studied.
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