In this work, titanium nitride (TiN) coating was used as a passive layer to inhibit metal catalytic coking during hydrocarbon fuel cracking on the microchannel inner surface of stainless steel 304 (SS304) tubes. In order to obtain an inert and effective passive coating, TiN coating was prepared in SS304 tubes with 2 mm inside diameter and 700 mm length by atmospheric pressure chemical vapor deposition (APCVD) using a TiCl4–H2–N2 system. The coating’s thickness, phase composition, morphology, and chemical composition were investigated by metalloscopy, X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), respectively. Characterization results indicated that TiN coating had a relatively complete cubic-phase crystal form with a N/Ti ratio of 1:1, presenting small star-shaped crystals on the whole. The inhibition effects of TiN coating on the morphologies and amounts of coke were studied by SEM and EDX after n-hexane thermal cracking at 600 °C and 3.3 MPa for 20 min. Under these conditions, different contributions to carbon deposition were discussed including oxidative reactions and pyrolysis of n-hexane. Along the axial length of the bare tube, stunted and clubbed cokes formed by autoxidation near the distance of 100 mm; granular metal carbides and filamentous cokes formed by metal catalysis near the distances of 350 and 600 mm, respectively. However, no morphologies of carbon deposits on a TiN-coated tube surface were observed after thermal cracking of n-hexane at 600 °C and 3.3 MPa for 20 min. At distances of 100, 350, and 600 mm away from the tube inlet, the carbon atomic percentages of coke in these three areas were 27.28%, 58.04%, and 99.69% for the bare tube, larger than those of 5.76%, 15.73%, and 30.66% for the TiN-coated tube, respectively. The results showed that the inhibition effect of APCVD TiN coating on coke growth is superior to that of other coatings (e.g., alumina coating). The reason is that TiN coating not only creates a barrier between the hydrocarbon fuels and metal surface to inhibit related catalytic coke formation but also minimizes carbon deposits by absorbing C atoms.

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Interactions among nutrients have been widely recognized in plants and play important roles in crop growth and yield formation. However, the interplay of Cu and N in rice plants is not yet clear. In this study, rice plants were grown with different combinations of Cu and N supply. The effects of Cu-N interaction on the growth, yield production, Cu and N transport, and gene expression levels were analyzed. The results showed that the effect of N supply on rice growth and yield formation was more pronounced than that of Cu supply. The Cu supply significantly improved the uptake of N (by 9.52–30.64%), while the N supply significantly promoted the root-to-shoot translocation of Cu (by 27.28–38.45%) and distributed more Cu (1.85–19.16%) into the shoots and leaves. The results of qRT-PCR showed that +Cu significantly up-regulated the expression levels of both NO3− and NH4+ transporter genes OsNRTs and OsAMTs, including OsNRT1.1B, OsNRT2.1, OsNRT2.3a, OsNRT2.4, OsAMT1.2, OsAMT1.3, and OsAMT3.1. Meanwhile, +N significantly up-regulated the expression levels of Cu transporter genes OsHMA5 and OsYSL16. In addition, the supply of Cu up-regulated the expression levels of OsGS1;2, OsGS2, and OsNADH-GOGAT to 12.61-, 6.48-, and 6.05-fold, respectively. In conclusion, our study demonstrates a synergistic effect between Cu and N in rice plants. It is expected that our results would be helpful to optimize the application of N and Cu fertilizers in agriculture.