An ammonium polyphosphate (APP) surface-modified by silane coupling agent was used as flame retardant in high-impact polystyrene (HIPS). A series of HIPS nanocomposites containing different mass fractions of APP (k-APP) surface-modified by silane coupling agent (3-aminopropyl triethoxysilane, KH 550) and carboxylic-functionalized MWCNTs (COOH–MWCNTs) were prepared by the melt blending method. A composite only containing APP was also prepared as a reference material. Scanning electron microscopy (SEM) was employed to investigate the dispersion of the fillers into the HIPS matrix, and it was found the hydrophobic groups on the k-APP surface would greatly enhance the dispersion and prevent agglomerations compared with APP. Furthermore, the COOH–MWCNTs also showed good dispersibility into the matrix. Mechanical tests of the nanocomposites revealed that k-APP exhibits a more beneficial effect on both tensile and flexural properties compared with APP. Thermogravimetric analysis (TGA) and cone calorimeter tests (CCT) were conducted to probe the thermal and flammability properties of the nanocomposites, respectively. The synergistic effects of k-APP and COOH–MWCNTs on mechanical, thermal and flammability properties were examined as well.

The lower flammability limit (LFL) is one of the most important parameters for evaluating the fire and explosion hazards of flammable gases or vapors. This study proposed quantitative structure−property relationship (QSPR) models to predict the LFL of binary hydrocarbon gases from their molecular structures. Twelve different mixing rules were employed to derive mixture descriptors for describing the structures characteristics of a series of 181 binary hydrocarbon mixtures. Genetic algorithm (GA)-based multiple linear regression (MLR) was used to select the most statistically effective mixture descriptors on the LFL of binary hydrocarbon gases. A total of 12 multilinear models were obtained based on the different mathematical formulas. The best model, issued from the norm of the molar contribution formula, was achieved as a six-parameter model. The best model was then rigorously validated using multiple strategies and further extensively compared to the previously published model. The results demonstrated the robustness, validity, and satisfactory predictivity of the proposed model. The applicability domain (AD) of the model was defined as well. The proposed best model would be expected to present an alternative to predict the LFL values of existing or new binary hydrocarbon gases, and provide some guidance for prioritizing the design of safer blended gases with desired properties.

316 L stainless steel is an ideal bipolar plate material for a proton exchange membrane fuel cell (PEMFC). However, the thickening of the passivation film on the stainless steel surface and the dissolution of corrosive ions during operation will affect the durability of the PEMFC. Herein, a heterogeneous layer is prepared on the surface of 316 L stainless steel through dual ion implantation of molybdenum ion and carbon ion combined with heat treatment to promote the corrosion resistance and conductivity of the bipolar plate. The ion implantation technique resulted in a uniform distribution of Mo and C elements on the surface of 316 L stainless steel, with a modified layer depth of about 70–80 nm. The electrical conductivity of the ion implanted samples was significantly improved, and the interfacial contact resistance was reduced from 464.25 mΩ × cm² to 42.49 mΩ × cm². Heat treatment enhances the surface homogenization, repairs the defects of irradiation damage, and improves the corrosion resistance of stainless steel. The corrosion current density of (Mo+C)-600 samples decreased from 1.21 × 10⁻⁸ A/cm² to 2.95 × 10⁻⁹ A/cm² under the long-term corrosion condition of 4 h. These results can provide guidance for the modification of stainless steel bipolar plates.

The broad use of (stainless steel) SS 316 L bipolar plates (BPs) in proton exchange membrane fuel cells relies (PEMFC) on high conductivity and corrosion resistance. To enhance the properties of stainless steel, this study applies ion implantation and heat treatment to form a non-homogeneous modified layer on SS 316 L. The injection of C and Mo ions on the SS 316 L surface caused irradiation damage, producing holes. But with the heat treatment of the ion-implanted samples, the irradiation-damaged surface will be repaired to a certain extent. The corrosion current density (I_corr) of the 600 °C sample in the kinetic potential test (5.32 × 10⁻⁴ A/cm²) was 54% lower than that of the naked SS 316 L (1.17 × 10⁻³ A/cm²). In the electrostatic potential test, the corrosion current of the 600 °C sample stabilized at a low value (about 0.26 μA/cm²), with the lowest concentration of dissolved metal ions (Fe²⁺ 2.908 mg/L). After anodic electrostatic potential polarization, the interfacial contact resistance (ICR) of (Mo+C)_600-1 was much lower than that of the untreated SS 316 L. Heat treatment experiments show that samples treated at 600 °C for 1 h exhibit significantly higher conductivity and anodic corrosion resistance than naked SS 316 L. This improvement is mainly due to the heat treatment under these conditions, which facilitated the formation of Mo carbides from the implanted C and Mo elements. Ion implantation and heat treatment enhance stainless steel surface conductivity and passive film corrosion resistance. These findings are useful in altering stainless steel BPs.