Numerical modeling of SiC by low-pressure chemical vapor deposition from methyltrichlorosilane

The development of functional relationships between the observed deposition rate and the experimental conditions is an important step toward understanding and optimizing low-pressure chemical vapor deposition(LPCVD)or low-pressure chemical vapor infiltration(LPCVI).In the field of ceramic matrix composites(CMCs),methyltrichlorosilane(CH3 SiCl3,MTS)is the most widely used source gas system for SiC,because stoichiometric SiC deposit can be facilitated at 900°C–1300°C.However,the reliability and accuracy of existing numerical models for these processing conditions are rarely reported.In this study,a comprehensive transport model was coupled with gas-phase and surface kinetics.The resulting gas-phase kinetics was confirmed via the measured concentration of gaseous species.The relationship between deposition rate and 24 gaseous species has been effectively evaluated by combining the special superiority of the novel extreme machine learning method and the conventional sticking coefficient method.Surface kinetics were then proposed and shown to reproduce the experimental results.The proposed simulation strategy can be used for different material systems.

Self-assembled synthesis of oxygen-doped g-C3N4 nanotubes in enhancement of visible-light photocatalytic hydrogen

Currently,photocatalytic water splitting is regarded as promising technology in renewable energy generation.However,the conversion efficiency suffers great restriction due to the rapid recombination of charge carriers.Rational designed the structure and doping elements become important alternative routes to improve the performance of photocatalyst.In this work,we rational designed oxygen-doped graphitic carbon nitride(OCN)nanotubes derived from supermolecular intermediates for photocata lytic water splitting.The as prepared OCN nanotubes exhibit an outstanding hydrogen evolution rate of 73.84μmol h^(-1),outperforming the most of reported one dimensional(1D)g-C_(3)N_(4) previously.Due to the rational oxygen doping,the band structure of g-C_(3)N_(4) is meliorated,which can narrow the band gap and reduce the recombination rate of photogene rated carriers.Furthermore,the hollow nanotube structure of OCN also provide multiple diffuse reflection during photocata lytic reaction,which can significantly promote the utilization capacity of visible light and enhance the photocatalytic water splitting performance.It is believed that our work not only rationally controls the nanostructure,but also introduces useful heteroatom into the matrix of photocatalyst,which provides an effective way to design high-efficiency g-C_(3)N_(4) photocatalyst.

Green intelligent fertilizers——A novel approach for aligning sustainable agriculture with green development

This review addresses the growing disparity between the current state of fertilizer production in China and the evolving demands of green agriculture in the 21st century. It explores major advances in fertilizers, proposes the concept of green intelligent fertilizers and develops new strategies aligned with the principles of green development in fertilizer industry and agriculture.Green intelligent fertilizers may be designed to maximize the synergistic effects among plants, soils, microorganisms, nutrient sources and the environment. This concept emphasizes the integration of industry and agriculture toward green development for entire industry chain, using an interdisciplinary approach to drive the green transformation of fertilizer industry, and promote green and sustainable development of agriculture. By bridging the gap between the current state of fertilizer industry and a growing need for environmentally responsible agricultural practices, this review highlights a path toward harmonizing fertilizer production with the imperatives of green agriculture.

Magnesium-fortified phosphate fertilizers improve nutrient uptake and plant growth without reducing phosphorus availability

Magnesium(Mg)deficiency can significantly limit crop yield and quality.Separate application of straight Mg fertilizer is unattractive because of additional labor costs.Meanwhile,bulk blending Mg with other macronutrient fertilizers is also a suboptimal solution because bulk blended fertilizers often yield poor nutrient distributions.One rapid and economical alternative to alleviating Mg deficiency is to co-granulate macronutrient fertilizers with Mg.However,few commercial products have implemented this approach.One of the barriers hindering the production of Mg-fortified phosphorus(P)fertilizers is the assumption that precipitation of P with Mg will reduce P solubility.In this study,four Mg compounds,anhydrous magnesium sulfate(MgSO_(4)),magnesium oxide(MgO),anhydrous magnesium chloride(MgCl_(2)),and dolomite(CaMg(CO_(3))_(2)),were co-granulated with mono-ammonium phosphate(MAP),and their granule strength,Mg and P availabilities,and agronomic effectiveness were evaluated.Results showed that there were no significant differences in P solubility between Mg-fortified MAP and MAP treatments.X-ray diffraction(XRD)indicated that the Mg species after co-granulation were boussingaultite(Mg(NH_(4))_(2)(SO_(4))_(2)·6H_(2)O),schertelite(Mg(NH_(4))_(2)H_(2)(PO_(4))_(2)·4H_(2)O),magnesium hydrogen phosphate(Mg(H_(2)PO_(4))_(2)),and dolomite(CaMg(CO_(3))_(2)).A pot experiment using an acidic soil demonstrated an average 9.6-fold increase in shoot Mg uptake,3.0-fold increase in shoot P uptake,and 3.2-fold increase in soybean shoot dry matter in Mg-fortified MAP treatments,compared to those in MAP treatment.The current study provides a simple,effective,and low-cost approach for the addition of Mg to macronutrient fertilizers,to minimize Mg deficiency.