High fire hazard of releasing considerable toxicants and heat is regarded as a notorious issue for hindering the further application of epoxy resin (EP). Hence, a hierarchical structure (MLBCN) based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets is rationally constructed as flame retardant additive for EP. Concretely, the incorporation of 1.0 wt% MLBCN leads to the decreases of 31.9% and 25.3% in peak heat release rate and total heat release, separately, reflecting the impeded heat release. Meanwhile, the peak smoke production rate and total smoke release are reduced by 37.1% and 33.4%, respectively, corroborating the hindered fire toxicity. The clear evidence for inhibited emissions of toxic CO and NO gases can be acquired from TG-IR spectra. These results collectively confirm the efficacy of MLBCN in reducing the toxicants generation and fire hazard of EP, deriving from its physical barrier, chemical catalyzing and charring promotion actions. Besides, the tensile and flexural strength are improved by 43.9% and 10.6%, by adding 1.0 wt% MLBCN, demonstrating the promoted mechanical performance. Overall, using MLBCN achieves the simultaneous enhancements in fire safety and mechanical capability of polymer. This work may provide valuable inspirations for constructing multicomponent hierarchical structure, optimizing their prospects in polymer-matrix composite and other areas.

Constructing hierarchical structure based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets towards reducing toxicants generation and fire hazard of epoxy resin

High fire hazard of releasing considerable toxicants and heat is regarded as a notorious issue for hindering the further application of epoxy resin (EP). Hence, a hierarchical structure (MLBCN) based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets is rationally constructed as flame retardant additive for EP. Concretely, the incorporation of 1.0 wt% MLBCN leads to the decreases of 31.9% and 25.3% in peak heat release rate and total heat release, separately, reflecting the impeded heat release. Meanwhile, the peak smoke production rate and total smoke release are reduced by 37.1% and 33.4%, respectively, corroborating the hindered fire toxicity. The clear evidence for inhibited emissions of toxic CO and NO gases can be acquired from TG-IR spectra. These results collectively confirm the efficacy of MLBCN in reducing the toxicants generation and fire hazard of EP, deriving from its physical barrier, chemical catalyzing and charring promotion actions. Besides, the tensile and flexural strength are improved by 43.9% and 10.6%, by adding 1.0 wt% MLBCN, demonstrating the promoted mechanical performance. Overall, using MLBCN achieves the simultaneous enhancements in fire safety and mechanical capability of polymer. This work may provide valuable inspirations for constructing multicomponent hierarchical structure, optimizing their prospects in polymer-matrix composite and other areas. 

Progress in tribological research of SiC ceramics in unlubricated sliding-A review

A review of tribological properties for boron carbide ceramics

The wettability of the metal/SiC system is not always excellent, resulting in the limitation of the widespread use of SiC ceramic. In this paper, three implantation doses of Si ions (5 × 1015, 1 × 1016, 5 × 1016 ions/cm2) were implanted into the 6H-SiC substrate. The wetting of Cu-(2.5, 5, 7.5, 10) Sn alloys on the pristine and Si-SiC were studied by the sessile drop technique, and the interfacial chemical reaction of Cu-Sn/SiC wetting couples was investigated and discussed. The Si ion can markedly enhance the wetting of Cu-Sn on 6H-SiC substrate, and those of the corresponding contact angles (θ) are raised partly, with the Si ion dose increasing due to the weakening interfacial chemical reactions among four Cu-Sn alloys and 6H-SiC ceramics. Moreover, the θ of Cu-Sn on (Si-)SiC substrate is first decreased and then increased from ~62° to ~39°, and ~70° and ~140°, with the Sn concentration increasing from 2.5%, 5% and 7.5% to 10%, which is linked to the reactivity of Cu-Sn alloys and SiC ceramic and the variation of liquid-vapor surface energy. Particularly, only a continuous graphite layer is formed at the interface of the Cu-10Sn/Si-SiC system, resulting in a higher contact angle (>40°).

https://www.mdpi.com/2079-6412/10/9/906/pdf

Synthesis, Characterization and Wettability of Cu-Sn Alloy on the Si-Implanted 6H-SiC

Boron carbide (B4C) ceramics has many outstanding performance, such as extremely high hardness, low density, high melting point, high elastic modulus, high thermoelectromotive force, high chemical ...

Progress in pressureless sintering of boron carbide ceramics – a review

SiC-B4C ceramic composites with different ratios of SiC to B4C were produced. The relative density, mechanical properties, initial surface characteristics, dry sliding tribological properties against SiC ball and worn surface characteristics of the SiC-B4C ceramics were studied. Results of dry sliding tribological tests showed that, 40 wt. % SiC-60 wt. % B4C ceramic composite had the best tribological properties in SiC-B4C ceramic composites. A relief structure with height difference of 10−30 nm between B4C grains and SiC grains is formed after dry sliding. This relief structure, on the one hand, can reduce real contact area on interface, decreasing adhesion effect, and on the other hand, can fix or trap the wear pieces formed on sliding interface during the dry sliding process, reducing the abrasive wear. However, there is a limit to the beneficial influence of decreased adhesion effect and reduced abrasive wear, and an optimum proportion of relief structure. Pores can also fix or trap some wear pieces, reducing the abrasive wear. Under the condition of strong bonding between SiC grains and B4C grains, the SiC-B4C ceramic composites with higher porosity can obtain better tribological properties. In addition, it is observed by AFM that the depth of scratch on B4C grains is shallower than that on SiC grains. Hence, it is demonstrated by micro scale measurement that the wear rate of B4C is lower than that of SiC in this study.

Wei Zhang

Papers

Progress in tribological research of SiC ceramics in unlubricated sliding-A review

Progress in pressureless sintering of boron carbide ceramics – a review

Tribological properties of SiC-B4C ceramics under dry sliding condition

Influence of surface roughness parameters and surface morphology on friction performance of ceramics

Effect of nanorelief structure formed in situ on tribological properties of ceramics in dry sliding