The CVD diamond film with favorable adhesion and relatively thinner thickness is essential facing for its application on drills for machining carbon fiber reinforced plastics (CFRP), with regard to either the tool lifetime or the machining quality. A 500-nm-thick CrN layer was deposited by the cathode arc technique on slight chemical etched WC–Co 6[Formula: see text]wt.% drill, and nano-crystalline diamond (NCD) is subsequently deposited by the hot filament chemical vapor deposition (HFCVD) technique. The same NCD film is also deposited on the drills pretreated only by the slight chemical etching or the CrN interlayer, which are adopted as comparisons in the present study. The nucleation and growth of diamond film and the cutting performance of the coated drills are systematically studied. The results show that the drill pretreated by the slight chemical etching and CrN interlayer can acquire highest nucleation density (ND) compared to the other pretreatment methods as it sufficiently prevents the Co diffusion. The diamond-coated drill with deep chemical etching was used for comparison to study the machining quality when drilling CFRP. During machining the CFRP, the failure mode of the diamond-coated drill is mainly the delamination and peeling off of the diamond film at areas with stress concentration, while the diamond-coated drill pretreated by slight chemical etching [Formula: see text] CrN interlayer can retard such failure. The exit hole quality of CRFP machined by drill pretreated with slight chemical etching [Formula: see text] CrN interlayer is better than that by drill pretreated with deep chemical etching, which is ascribed to the different cutting edges of the drills.
The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e., low part-per-trillion level), selective, and humidity-resistant detection of gaseous nitric oxide in air remains challenging. In the field, humidity can have dramatic effects on the accuracy and selectivity of gas sensors, confounding data, and leading to overestimation of gas concentration. Highly selective and humidity-resistant gaseous NO sensors based on laser-induced graphene were recently reported, displaying a limit of detection (LOD) of 8.3 ppb. Although highly sensitive (LOD = 590 ppq) single-wall carbon nanotube NO sensors have been reported, these sensors lack selectivity and humidity resistance. In this report, we disclose a highly sensitive (LOD = 2.34 ppt), selective, and humidity-resistant nitric oxide sensor based on a whispering-gallery mode microtoroid optical resonator. Excellent analyte selectivity was enabled via novel ferrocene-containing polymeric coatings synthesized via reversible addition–fragmentation chain-transfer polymerization. Utilizing a frequency locked optical whispering evanescent resonator system, the microtoroid's real-time resonance frequency shift response to nitric oxide was tracked with subfemtometer resolution. The lowest concentration experimentally detected was 6.4 ppt, which is the lowest reported to date. Additionally, the performance of the sensor remained consistent across different humidity environments. Lastly, the impact of the chemical composition and molecular weight of the novel ferrocene-containing polymeric coatings on sensing performance was evaluated. We anticipate that our results will have impact on a wide variety of fields where NO sensing is important such as medical diagnostics through exhaled breath, determination of planetary habitability, climate change, air quality monitoring, and treating cardiovascular and neurological disorders.
In this study, a top-down approach was employed for the fabrication of flame-retardant wood aerogels. The process involved the removal of lignin and the removal of hemicellulose utilizing NaOH concomitantly with the incorporation of ZnO and urea. Subsequently, an in situ reaction with boric acid was conducted to prepare flame-retardant wood aerogels. The morphology, chemical composition, thermal stability, and flame retardancy of the samples were studied. The results show that the NaOH treatment transformed the wood into a layered structure, and flame-retardant particles were uniformly distributed on the surface of the aerogel. The peak heat release rate (PHRR) and total heat release (THR) of the flame-retardant aerogel were significantly reduced compared with the control samples. Meanwhile, its vertical burning test (UL-94) rating reached the V-0 level, and the Limiting Oxygen Index (LOI) could exceed 90%. The flame-retardant wood aerogel exhibited excellent flame retardancy and self-extinguishing properties.
The present paper reports a new way to improve the wear resistance of coated carbide tools by increases in TiC content and the addition of TaC in substrates. The results suggest that the average grain size of the substrate increased with the increases in TiC (0–14 wt.%) content, and the hardness of the TiAlN coating deposited on the substrate exhibits a similar trend. In addition, the adhesion strength of the TiAlN-coated carbide increases with increasing TiC content, which can be attributed the formation of the (Ti,W)C phase and the similar hardness of the substrate and coating. The addition of TaC into the substrates inhibits the grain growth and thereby causes the hardness and adhesion strength of the TiAlN coatings to improve from 24.6 GPa and 16.7 N to 30.1 GPa and 17.3 N, respectively. In turning tests, the TiAlN coating deposited on the substrates with the TaC addition achieved the best wear resistance in turning stainless steel because it possessed the highest substrate and coating hardness and sufficient adhesion strength. However, the TiAlN coating deposited on the substrates with a higher TiC content shows the better wear resistance in turning titanium (TC4), which can be attributed to it having the highest adhesion strength.
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