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Digital light processing (DLP) is one of the most important additive manufacture technologies to fabricate ceramic parts with complex geometries. Compared with pure photosensitive resin, the cure performance of ceramic suspensions is obviously different due to the optical property change after the addition of ceramic powders. In this paper, a unique oxidation process was used to modify the optical properties of nitride powders including AlN and Si3N4. The properties of oxidized ceramics were investigated and the cure performance of ceramic suspensions was then characterized. The effect of oxidation time on cure performance was evaluated. The results showed that for AlN, oxidation process leads to the smaller cure depth and smaller excess cure width as compared with non-oxidized AlN and for Si3N4, oxidation process leads to the larger cure depth and larger excess cure width as compared with non-oxidized Si3N4, indicating that both refractive index and light absorbance of ceramic powders have obvious effects on cure behaviors. Additionally, the cure behavior of oxidized ceramic suspension in this study shows that the relationship of cure depth vs. incident energy agrees well with Beer- Lambert model, but the excess cure width vs. incident energy is not consistent with quasi Beer-Lambert model due to the nature of digital micromirror device (DMD).

It remains challenging to broaden the application fields of ceramics, largely because the hardness and brittleness of ceramics mean that they cannot undergo shape reconfiguration. In this study, we developed an ultraviolet light-curable preceramic polymer slurry, and this slurry was used for digital light processing printing of flexible green parts in designed shapes. These parts were subsequently transformed into complex structures by an assisted secondary molding strategy that enabled the morphology of their green and pyrolyzed forms to be well controlled. The collapse of bulk pyrolyzed parts was avoided by impregnating their precursors with silicon nitride (Si3N4) particles. The effects of different proportions of Si3N4 on the weight loss, shrinkage, density, porosity, and mechanical properties of the pyrolyzed composites were investigated, and the bending strength and Vickers hardness of the composites with 10 wt.% Si3N4 were found to be 130.61 ± 16.01 MPa and 6.43 ± 0.12 GPa, respectively.

The bending strength of silicon nitride (Si3N4) plays a vital role in its application and is influenced by various process factors. Current experimental methods for investigating Si3N4 ceramics exhibiting low efficiency and high cost are incapable of systematically analysing the effect of process factors on the bending strength of Si3N4 ceramics and quantitatively predicting the optimum process parameters. In this study, machine learning (ML) approaches based on extreme gradient boosting (XGBoost) were applied to predict and analyse the bending strength of Si3N4 ceramics. Because the classification model of XGBoost is easily interpretable, the factors affecting the bending strength could be quantitatively evaluated. The current model can provide a suitable order of adding sintering additives to obtain excellent bending strength in Si3N4 ceramics. Although this study focuses on the bending strength of Si3N4 ceramics, the new approach reported herein is applicable for the in silico design and analysis of other ceramic materials.

In this study, the chemical precipitation coating (CP) process was creatively integrated with DLP-stereolithography based 3D printing for refining and homogenizing the microstructure of 3D printed Al2O3 ceramic. Based on this novel approach, Al2O3 powder was coated with a homogeneous layer of amorphous Y2O3, with the coated Al2O3 powder found to make the microstructure of 3D printed Al2O3 ceramic more uniform and refined, as compared with the conventional mechanical mixing (MM) of Al2O3 and Y2O3 powders. The grain size of Al2O3 in Sample CP is 64.44% and 51.43% lower than those in the monolithic Al2O3 ceramic and Sample MM, respectively. Sample CP has the highest flexural strength of 455.37±32.17 MPa, which is 14.85% and 25.45% higher than those of Samples MM and AL, respectively; also Sample CP has the highest Weibull modulus of 16.88 among the three kinds of samples. Moreover, the fine grained Sample CP has a close thermal conductivity to the coarse grained Sample MM because of the changes in morphology of Y3Al5O12 phase from semi-connected (Sample MM) to isolated (Sample CP). Finally, specially designed fin-type Al2O3 ceramic heat sinks were successfully fabricated via the novel integrated process, which has been proven to be an effective method for fabricating complex-shaped Al2O3 ceramic components with enhanced flexural strength and reliability.

Combined pollution caused by organic pollutants and heavy metals is common in polluted sites and wastewater. Engineering artificial microbial consortia offers a promising approach to address this complex issue. However, the mutualistic interactions and the critical function of specific microbe within microbial consortia remain unclear. In this study, based on division of labor, we respectively co-cultured two Cr(VI)-reducing strains, Paenarthrobacter nitroguajacolicus C1 and Pseudomonas putida C2, with an atrazine-degrading strain, Paenarthrobacter ureafaciens AT. After 5 days, up to 95 % Cr(VI) and 100 % atrazine were removed from the cocultures. Strain AT degraded nearly all atrazine and contributed only to a fraction of Cr(VI) reduction, whereas C1 promoted 41 % Cr(VI) transformation to Cr(III) fixed in cells, and C2 promoted 91 % Cr(VI) transformation to soluble Cr(III). Metabolic analyses of the cocultures and monocultures demonstrated that AT provided C1 with isopropylamine by passive diffusion and C2 with other effective nitrogen resources by cell-cell surface contact to promote their growth. Soil experiments also showed that treatments with AT and C2 achieved the highest Cr(VI) reduction and no atrazine residue. Our results indicate that engineering artificial microbial consortia based on division of labor and metabolic interactions is effective in promoting highly efficient bioremediation of combined pollution.

Digital light processing (DLP) based stereolithography opens new possibilities for fabricating ceramic accessories with complex structures. The cure depth is a critical criterion for analyzing the production efficiency of ceramic accessories. As predicted using the absorption model, the absorbance from the photoinitiator and dye has a direct effect on the cure depth. In this study, blue-colored powder composed of 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) and CoAl2O4 powder was prepared through ball-milling. The cure depth of a single layer exposed to varying energy levels was measured, and the values of the depth sensitivity Sd and critical energy Ec were also calculated. The results showed that the absorbance of blue-colored 3Y-TZP powder increased with CoAl2O4 content, which increased the critical energy Ec and depth sensitivity reciprocal 1/Sd. Compared with the pure 3Y-TZP, the cure depth decreased, which was attributable to the absorbance of CoAl2O4. In addition, blue-colored accessories were fabricated using the DLP method, and the microstructures of the accessories were characterized through scanning electron microscopy.

Yttria (Y2O3) is the most popular lining material for the inner walls of plasma chambers, owing to its well-known resistance against corrosion by reactive fluorinated plasma. Yttria has a relatively lower toughness and strength compared to alumina (Al2O3) and zirconia (ZrO2). The present work aims to explore the strengthening and toughening of yttria by doping with zirconia, while retaining its good corrosion resistance. Ceramics with zirconia to yttria molar ratios of 2:8 and 5:5 (named 20ZY and 50ZY, respectively) were fabricated by pressure sintering in Ar atmosphere. The corrosion of the prepared ceramics in reactive fluorinated plasma (C4F8/CHF3/Ar) was investigated and compared with that of yttria as a control. The results indicated that 20ZY exhibited excellent corrosion resistance, comparable to that of yttria, while the fracture toughness and flexural strength showed increases of 87% and 44%, respectively. 50ZY exhibited a further improvement in fracture toughness and flexural strength, but at the price of a much lower resistance against plasma corrosion. A percolation model was proposed to interpret the observed plasma corrosion behaviors.

In groundwater, deep soil layer, sediment, the widespread of xenobiotic organic contaminants (XOCs) have been leading to the concern of human health and eco-environment safety, which calls for a better understanding on the fate and remediation of XOCs in anoxic matrices. In the absence of oxygen, bacteria utilize various oxidized substances, e.g. nitrate, sulphate, metallic (hydr)oxides, humic substance, as terminal electron acceptors (TEAs) to fuel anaerobic XOCs degradation. Although there have been increasing anaerobic biodegradation studies focusing on species identification, degrading pathways, community dynamics, systematic reviews on the underlying mechanism of anaerobic contaminants removal from the perspective of electron flow are limited. In this review, we provide the insight on anaerobic biodegradation from electrons aspect — electron production, transport, and consumption. The mechanism of the coupling between TEAs reduction and pollutants degradation is deconstructed in the level of community, pure culture, and cellular biochemistry. Hereby, relevant strategies to promote anaerobic biodegradation are proposed for guiding to an efficient XOCs bioremediation.

WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting (SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co cemented carbides with different Co contents (12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20Co and WC-32Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co cemented carbides with Co content as low as 12 wt%. The comparison between horizontal (perpendicular to the SLM laser beam) and vertical (parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12Co, WC-20Co, and WC-32Co.

The status of oxygen impurity in β-Si3N4 lattice and its impact on β-Si3N4 phonon spectrum were studied using the first principle calculation based on density functional theory. The dependence of in silico thermal conductivity of β-Si3N4 upon lattice oxygen was quantitatively addressed. This study also confirms that rare-earth La doping has a pinning effect on oxygen, which underlies, in mechanism, for the increase of thermal conductivity of β-Si3N4 ceramic by restraining oxygen diffusion inside β-Si3N4 lattice. The theoretical prediction above is consistent in trend with the reported experimental results. In addition, in silico modulus values of β-Si3N4 ceramic were also revealed declined with increasing oxygen impurity.

The feasibility of selective laser melting (SLM) was investigated for manufacturing WC-20Co cemented carbide in this study. Both the microstructure analysis and finite element simulation were used ...

To improve the thermal and mechanical properties of Al2O3/AlN composite ceramics, a novel heterogeneous precipitation coating (HPC) approach was introduced into the fabrication of Al2O3/AlN ceramics. For this approach, Al2O3 and AlN powders were coated with a layer of amorphous Y2O3, with the coated Al2O3 and AlN powders found to favor the formation of an interconnected YAG second phase along the grain boundaries. The interconnected YAG phase was designed to act as a diffusion barrier layer to minimize the detrimental interdiffusion between Al2O3 and AlN particles. Compared with samples prepared by a conventional ball-milling method, the HPC Al2O3/AlN composites exhibited less AlON formation, a higher relative density, a smaller grain size and a more homogeneous microstructure. The thermal conductivity, bending strength, fracture toughness and Weibull modulus of the HPC Al2O3/AlN composite ceramics were found to reach 34.21 ± 0.34 W m−1 K−1, 475.61 ± 21.56 MPa, 5.53 ± 0.29 MPa m1/2 and 25.61, respectively, which are much higher than those for the Al2O3 and Al2O3/AlN samples prepared by the conventional ball-milling method. These results suggest that HPC is a more effective technique for preparing Al2O3/AlN composites with enhanced thermal and mechanical properties, and is probably applicable to other composite material systems as well.

In this work, Al2O3-AlN composite ceramics with high bending strength and thermal conductivity were fabricated by Digital Light Processing (DLP). The influence of AlN content on the rheological and cure behavior of Al2O3-AlN suspensions, as well as the microstructure, thermal conductivity, and bending strength of Al2O3-AlN ceramics, were systematically investigated. The result shows that the viscosity and cure ability of the suspensions were decreased with the increase of AlN content, which are beneficial to the spreading and printing accuracy of the suspensions. Besides, the bending strength of ceramics can be improved due to the residual stress by the introduction of AlN. Approaches were employed to minimize the formation of AlON in Al2O3-AlN ceramics by optimizing the amount of AlN and the sintering temperature. The thermal conductivity and bending strength of Al2O3-AlN ceramics were 31.72 ± 0.45 W/(m·K) and 572.73 ± 59.40 MPa, respectively, which are much higher than those of Al2O3 ceramics fabricated under the same condition. Finally, complex-shaped Al2O3-AlN ceramics components have been successfully fabricated by DLP, which may provide an opportunity to broaden the application of Al2O3-AlN composite ceramics in heat dissipation components.

Flexible pipes are extensively used to connect seabed and floating production systems for the development of deep-water oil and gas. In the top connection area, end fitting (EF) is the connector between the flexible pipe and floating platform, as a critical component for structural failure. To address this issue, a combined numerical and experimental prediction method is proposed in this paper to investigate the failure behavior of flexible pipes EF considering tensile armor and epoxy resin debonding. In order to analyze the stress distribution of the tensile armor and the damage state of the bonding interface as the tensile load increases, a finite element model of the EF anchorage system is established based on the cohesive zone model (CZM). Additionally, the effects of the epoxy resin shear strength (ss) and the steel wire yield strength (ys) on the structural load-bearing capacity are discussed in detail. The results indicate that wire strength and interface bonding have a substantial effect on the anchorage system’s failure behavior, and the low-strength wire anchorage system has a three-stage failure behavior with wire yielding as the predominant failure mode, while the high-strength wire anchorage system has a two-stage failure behavior with interface debonding as the predominant failure mode.

In this study, the light absorption of the pure ZrO2 and three types of colorful ZrO2 mixtures were investigated. It was found that the absorbance of colored ZrO2 powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO2 powder. The cure behavior investigation on the ceramic suspensions of the above four types of ZrO2 powders during DLP process shows that as the colorant content increases, the cure depth and excess cure width both decrease due to the ceramic absorbance. The cure depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the cure width shows that the excess cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO2 accessories were successfully fabricated.

Biofertilizers are substances that promote plant growth through the efficacy of living microorganisms. The functional microbes comprising biofertilizers are effective mediators in plant-soil systems in the regulation of nitrogen cycling, especially in nitrification repression. However, the deterministic or stochastic distribution of the functional hotspot where microbes are active immediately after biofertilization is rarely investigated. Here, pot experiments with oil-seed rape (

Petroleum hydrocarbon-contaminated sites have been mainly remediated through the surfactant-enhanced soil leaching method. However, the commonly used chemical surfactants have poor biocompatibility and are prone to form residues in fields. Therefore, the purpose of this research is to establish an effective system of biosurfactant remediation in the field and provide instructions for common bioremediation challenges. First, wild-type Bacillus amyloliquefaciens A3, which produced lipopeptide biosurfactant, was used to improve the production of biosurfactant by atmosphere and room temperature plasma (ARTP) mutagenesis. Second, the mutant 1-24 was selected from a total of 174 mutants due to the outstanding yield. Subsequently, 1-24 was applied in the soil column leaching experiments and removed 45.44% of petroleum hydrocarbons by changing the relevant enzyme activities. Biosurfactant addition and 1-24 inoculation effectively activated a portion of the petroleum hydrocarbons in the soil columns, and 1-24 presented potential as a desired candidate for bioremediation. This is the first report of using ARTP mutagenesis to improve the production of biosurfactants. Simultaneously, we first propose a theoretical system in which the yield of biosurfactant was increased using ARTP mutagenesis for strains and applied the mutants in situ soil bioremediation. This research indicated that the theoretical system was useful in soil columns to simulate field remediation conditions, providing practical references for the bioremediation of contaminated soil.

Surfactant-enhanced remediation (SER) is one of the most effective methods for petroleum hydrocarbon-contaminated sites compared to single physical and chemical methods. However, biosurfactants are not as commonly used as chemical surfactants, and the actual remediation effects and related mechanisms remain undefined. Therefore, to comprehensively compare the remediation effects and biological mechanisms of biosurfactants and chemical surfactants, soil column leaching experiments including two biosurfactants (rhamnolipids and lipopeptide) and three commercially used chemical surfactants (Tween 80, Triton X-100, and Berol 226SA) were conducted. After seven days of leaching, rhamnolipids exhibited the highest petroleum hydrocarbon removal rate of 61.01%, which was superior to that of chemical surfactants (11.73-18.75%) in n-alkanes C10-C30. Meanwhile, rhamnolipids exhibited a great degradation advantage of n-alkanes C13-C28, which was 1.22-30.55 times that of chemical surfactants. Compared to chemical surfactants, biosurfactants significantly upregulated the soil's biological functions, including soil conductivity (80.90-155.56%), and soil enzyme activities of lipase (90.31-497.10%), dehydrogenase (325.00-655.56%), core enzyme activities of petroleum hydrocarbon degradation, and quorum sensing between species. Biosurfactants significantly changed the composition of Pseudomonas, Citrobacter, Acidobacteriota, and Enterobacter at the genus level. Meanwhile, chemical surfactants had less influence on the bacterial community and interactions between species. Moreover, the biosurfactants enhanced the microbial interactions and centrality of petroleum hydrocarbon degraders in the community based on the network. Overall, this work provides a systematic comparison and understanding of the chemical- and bio-surfactants used in bioremediation. In the future, we intend to apply biosurfactants to practical petroleum hydrocarbon-contaminated fields to observe realistic remediation effects and compare their functional mechanisms.

The discovery of heterotrophic nitrification-aerobic denitrification (HN-AD) microorganisms has opened a new window for wastewater treatment. The underlying mechanism of HN-AD, however, is not fully understood because of the phylogenetic diversity of HN-AD microbes. The isolation and characterization of new HN-AD microorganisms are encouraging for furthering the understanding of this process. In this study, we found an

The levels of organic pollutants, in particular polycyclic aromatic hydrocarbons (PAHs), are increasing worldwide, yet we lack clarity on how these pollutants affect microbial communities of different trophic levels, including protists, fungi, and bacteria. Herein, we conducted soil microcosm incubation experiments to investigate the effects of pyrene, a typical PAH, on microbial communities along concentration gradients from 0 to 500 mg kg

Constructed wetlands (CWs) can remove nitrogen (N) through plant assimilation and microbial nitrification and denitrification, while it also releases large greenhouse gas nitrous oxide (N

Due to high light absorption and high refractive index of silicon nitride (Si3N4) ceramic, it is difficult to prepare Si3N4 slurry with favourable curing ability, high solid loading and low viscosity at the same time, and thus the high quality Si3N4 parts are hard to fabricate via Digital Light Processing (DLP). In this paper, oxidation process was used to enhance the curing behavior of Si3N4 slurry, and then silane coupling agent (KH560) was used to improve the rheological properties of the oxidized Si3N4 slurry. The effect of Si3N4 slurry with oxidation and modification on its rheological behavior, light absorption, curing ability and stability have been systematically investigated. A Si3N4 slurry with abundant photocuring ability, high solid loading, low viscosity and reliable stability was fabricated by the oxidized (1h) and KH560 (1wt.%) modified Si3N4 powders, and the dense Si3N4 ceramic parts were produced by this slurry via DLP 3D printing. Subsequently, the influence of oxidation and modification on microstructure, mechanical properties and thermal conductivity have been investigated. Finally, the performances of the DLP 3D printed samples are close to the isostatic cool pressing (ICP) fabricated samples. Consequently, DLP has well potential to fabricate high-performance Si3N4 ceramics.

Elucidating the relative importance of species interactions and assembly mechanisms in regulating bacterial community structure and functions, especially the abundant and rare subcommunities, is crucial for understanding the influence of environmental disturbance in shaping ecological functions. However, little is known about how polycyclic aromatic hydrocarbon (PAH) stress alters the stability and functions of the abundant and rare taxa. Here, we performed soil microcosms with gradient pyrene stresses as a model ecosystem to explore the roles of community assembly in determining structures and functions of the abundant and rare subcommunities. The dose–effect of pyrene significantly altered compositions of abundant and rare subcommunities. With increasing pyrene stresses, diversity increased in abundant subcommunities, while it decreased in the rare. Importantly, the abundant taxa exhibited a much broader niche width and environmental adaptivity than the rare, contributing more to pyrene biodegradation, whereas rare taxa played a key role in improving subcommunity resistance to stress, potentially promoting community persistence and stability. Furthermore, subcommunity co-occurrence network analysis revealed that abundant taxa inclined to occupy the core and central position in adaptation to the pyrene stresses. Stochastic processes played key roles in the abundant subcommunity rather than the rare subcommunity. Overall, these findings extend our understanding of the ecological mechanisms and interactions of abundant and rare taxa in response to pollution stress, laying a leading theoretical basis that abundant taxa are core targets for biostimulation in soil remediation.

In-situ SiAlON reinforced BN-matrix ceramics were prepared by hot pressing sintering, and the effects of different rare earth oxides on the thermal shock resistance of the materials were investigated. The effects of rare earth oxides on the phase composition, microstructure, bending strength, thermal properties and thermal shock resistance of the composites were studied. The results show that the phase composition and bending strength of ceramics with different rare earth oxides had no obvious change. However, the influence on the thermal expansion coefficient of the material was notable. The thermal expansion coefficient of the ceramics with CeO2 increased by 24.6% compared with Sm2O3 in the test temperature range. After 50 cycles of thermal shock at Δt = 1150 °C, the residual strength of ceramics with CeO2 was down to 157.1 MPa, decreased by 40.6% compared with the one tested in room temperature. And the Sm2O3-added ceramics reduced by 34.7%–167.1 MPa after thermal shock. The decrease of the residual strength of ceramics is mainly caused by the internal stress generated by the mismatch between the growth of quartz and SiAlON phase in the matrix and the thermal expansion coefficient of the matrix. However, no macro cracks were observed on the surface of the samples after thermal shock.

The phyllosphere, which supports a large number of microorganisms, represents the interface between the aboveground parts of plants and air. In this study, four nifH clone libraries were constructed from the phyllosphere of Pyrus serotina (L), Vitis vinifera (P), Prunus armeniaca (X), and Prunus avium (Y). Clones related to Skermanella (L, 12.1%; X, 15.6%; Y, 62.5%; P 70.8%), Bradyrhizobium (X, 2.1%; P, 15.1%; L, 63.7%), Erwinia (X, 68.8%), Pseudomonas (L, 3.3%; P, 7.6%), and Chroococcidiopsis (P, 0.9%; L, 4.4%, X; 5.2%, Y; 19.6%) were present at high percentages, highlighting their critical role in contributing nitrogen to the phyllosphere ecosystem. The 16S rDNA sequence analysis suggested that phyllosphere-associated bacteria were affiliated with a wide range of taxa, encompassing members from Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Cyanobacteria, Tenericutes, and Deinococcus–Thermus. Additionally, the abundance of the nifH gene and 16S rDNA was assessed with quantitative PCR. The number of copies of nifH and 16S rDNA ranged from 1.14 × 103to 1.49 × 104and from 3.72 × 106to 7.02 × 107copies/g fresh leaf sample, respectively. In conclusion, our work sheds light on the microbial communities of the phyllosphere that are important for plant growth. Moreover, we observed a unique composition of nitrogen-fixing bacteria in each phyllosphere sample, suggesting the existence of specific interactions between these functional microorganism and plants, which may provide information or be a reference for the development of bacterial fertilizers.

The radial oxygen loss (ROL) of wetland plants is a crucial factor that can influence the efficiency required for nitrogen (N) removal and microbial activities responsible for N removal in constructed wetlands (CWs). However, the shift of microbial community in different niches in response to ROL has been rarely studied. This study aims to unravel the link between the ROL and microbial response in sediment, water and rhizoplane by a surface flow CW planted with Myriophyllum aquaticum for treating high-strength swine wastewater. Ti3+-citrate colorimetric method demonstrated that M. aquaticum was a wetland species with a ROL of 0.019 mg/h/plant. Using quantitative polymerase chain reactions (qPCR) and high-throughput sequencing of microbial 16S rRNA gene, we demonstrated that the abundance of facultative anaerobic denitrifiers in the rhizoplane was the most of the three niches, that in the water (5–10 cm) was the less and that in the sediment was the least. Acinetobacter was enriched and dominated amongst denitrifiers in the water. Denitrifiers in the rhizoplane were mainly dominated by enriched Pseudomonas, Aeromonas, and Acinetobacter. The theoretical calculation of oxygen sources and consumptions indicated that water reaeration should support the oxygen demands for nitrification in the aerobic layer (0–5 cm), and the ROL could stimulate the growth of facultative anaerobic denitrifiers in the rhizoplane and water (5–10 cm) to achieve denitrification within CW systems.

In this paper, Hot Pressing Flowing Sintering (HPFS) was successfully applied to the consolidation of silicon nitride ceramics at low sintering temperature. Fine-grained α/β-Si3N4 with high density was fabricated by HPFS at 1550 °C. The low temperature densification process was based on the hot pressing flow enhanced particle rearrangement mechanism. The shear stress which generated in the flowing process helped enhance the particle rearrangement with the lubrication of the liquid phase, which lead to collapse of the pores. The densification process was finished with minimum grain growth. Meanwhile, the rod-like β-Si3N4 nuclei was textured during the flowing process. The (101)/(210) ratio of β-Si3N4 was 0.09 on the plane perpendicular to the hot-pressing direction. The Vickers hardness and flexural strength of the sintered sample was 19.59 ± 0.36 GPa and 1022 ± 138 MPa, respectively.

5 wt% of different types of rare earth oxides (Re2O3, Re = Lu, La, Yb, Y, Nd, Er, Sm, Ce, Dy, Eu, Gd) and 2 wt% MgO as additives were selected in this study based on previous studies on rare earth oxide additive concentrations. The effects of rare earth oxide type on the microstructure, phase composition, thermal conductivity, mechanical properties, and dielectric properties of silicon nitride ceramics were systematically investigated. Samples doped with rare earth oxides with smaller ionic radii (such as Yb2O3, Lu2O3, Er2O3, and Dy2O3) showed higher thermal conductivity. Samples doped with Eu2O3 and Yb2O3 showed fine-grained microstructures due to inhibition of dissolution, diffusion, and re-precipitation of silicon nitride. Silicon nitride ceramics doped with Eu2O3 showed the lowest thermal conductivity and dielectric constant (

Si3N4 ceramic is difficultly fabricated by digital light processing (DLP) based stereolithography method, due to a large refractive index difference between Si3N4 powder and resin. In this paper, a surface oxidation approach of Si3N4 powder for improving cure depth is proposed. The results showed that, the amorphous SiO2 layer was uniformly attached onto the surface of Si3N4 powder by surface oxidation, and the absorbance of Si3N4 powder decreased as increasing oxidation degree. Moreover, the cure depth of the suspension significantly increased because of a smaller absorbance and a refractive index difference at the interface between oxidized Si3N4 powder and resin. At the exposure energy of 500 mJ/cm2, the cure depth of the raw Si3N4 powder was 34 µm. After oxidizing at 1150 °C and 1200 °C for 1 h, the cure depth effectively increased to 42 µm and 51 µm, respectively. Finally, the complex-shaped Si3N4 parts were successfully fabricated using surface-oxidized Si3N4 powder via DLP method.

In this study, we propose an integrated approach which combines 3D printing and liquid precursor infiltration together to prepare alumina-toughened zirconia (ATZ) composite. Controllable manipulation of the microstructure of the composite could be realized through different infiltration times and sintering temperature. The 3D-printed ATZ with infiltration and post-CIP sintered at 1550 °C possesses the highest relative density (98.11%), hardness (12.65 ± 0.24 GPa) and fracture toughness (6.42 ± 0.33 MPa m1/2). The rates of increase in the performance compared with the undoped zirconia sintered at 1550 °C are 1.8%, 8.4% and 34.6%, respectively. The dominated toughening mechanism of ATZ could be attributed to the effect of Al2O3 inclusion on crack deflection and energy absorption. The 3D-printed ATZ sample with infiltration followed by CIP sintered at 1550 °C shows the lowest aging rate and the lowest phase transformation depth compared with 3Y-TZP (Tetragonal Zirconia Polycrystal). Our integrated approach could not only realize the complex and ultrafine shape free of molds, but also suppress the low temperature aging behavior of dental implants, which has baffled dentists for a long time.

In this paper, BN–SiO2 porous ceramics with high porosity have been successfully fabricated using bottom-up digital light processing (DLP) stereolithography and pressureless sintering. The phase composition, microstructure, compressive strength, dielectric properties and porosity of the porous material were investigated. The results show that the skeleton of the porous material was composed of h-BN, and the silica was ‘coated’ on the surface of the h-BN particles. The dielectric constant, dielectric loss, compressive strength and porosity of the material were 1.41–1.45, 1.85 × 10−3–1.93 × 10−3, 11.2 MPa, 77.2%, respectively. These characteristics make the h-BN–SiO2 porous ceramics useful in wave-transmitting field.