To address the thermal fade problem of brake pads, a boron-modified phenolic resin with better temperature resistance is intended to be developed. By introducing B-O bonds and high-temperature-resistant units, the thermal decomposition temperature of the phenolic resin will be increased. The modified resin is obtained through a step-growth polymerization reaction and then incorporated into the brake pad formulation to be hot-pressed into samples. The thermal decomposition temperature of the resin is measured by TGA, and the thermal fade performance of the brake pad samples is analyzed through friction and wear experiments. The results show that the introduction of B-O bonds and the doping of nano-alumina have increased the thermal decomposition temperature of the phenolic resin to 480 °C, meeting the expectation. Brake pads molded with this resin as an adhesive showed significantly better thermal degradation than those made with ordinary phenolic resin. Meanwhile, during the braking process, the brake pads made from this resin form a complete and continuous friction film, demonstrating good mechanical properties and thermal fade performance. The wear amount under the entire braking test is also acceptable. In addition, an exploration of the thermal fade mechanism is carried out.

A detailed thermodynamic equilibrium analysis in the chemical vapor deposition of HfC as coatings for ceramic matrix composites with HfCl_{x(x = 2–4)}-C_yH_z(CH₄, C₂H₄ and C₃H₆)-H₂-Ar system has been investigated using the FactSage code. To protect the excellent performance of the composites, we demand a suitable composition and yield of condensed phases. They have been examined as functions of the inject reactant ratios of HfCl_x/(HfCl_x + C_yH_z) and H₂/(HfCl_x + C_yH_z), temperatures, and pressures. The results show that the HfCl₄ species are the optimal Hf-source in the deposition process. The ideal ratio parameters for production of single phase HfC are Log[H₂/(HfCl₄ + C_yH_z)] = 2 and Hf/C = 1. And the optimum temperature condition is above 1200 K. A lower pressure of 5 kPa is found to be more favorable for the deposition of a pure HfC phase. The co-deposition of HfC with C or Hf will be easily obtained by only controlling the ratios of HfCl₄/(HfCl₄ + C_yH_z) and H₂/(HfCl₄ + C_yH_z). The HfCl₄-C₃H₆-H₂ precursor system should be the best choice in the experiment due to a higher yield of HfC at the same deposition conditions. The results in this work will be helpful for the further experiment investigation under different deposition conditions and put forward a new idea in exploration of the preparation method of coatings for ceramic matrix composites. Graphical abstract

To achieve effective antioxidation of on-site repair coating for C/C brake materials in the full temperature range (500–900 °C), lead glass and bismuth glass were introduced into the borosilicate glass to acquire the protective coatings. Before preparing coating samples, the thermal gravity characteristics of the lead/bismuth–borosilicate glass powders were analyzed by TG/DSC. The results revealed that the temperature at which weight gain begins was 495 °C and 545 °C, respectively. The oxidation behaviors of the lead- and bismuth-modified borosilicate glass coatings were compared at 500 °C, and the antioxidation properties of the former were further examined from 500 to 900 °C. The oxidation results indicated that mixing lead glass with borosilicate glass realized effective oxidation resistance in the full temperature range. With a lead content of 20%, the lead–borosilicate glass coating was able to protect C/C substrates from oxidation. The corresponding weight loss of the lead-glass-coated samples was −1.89% when oxidized at 500 °C for 10 h, while the weight loss was −2.55% when further oxidized at 900 °C for 10 h. However, mixing bismuth glass with borosilicate glass was difficult to achieve the oxidation resistance of the coating at 500 °C due to the significant phase separation.