Abstract:Abstract. The thermo-oxidative degradation behavior of the B-PF was studied using thermal gravimetry analysis (TGA-DTG) method. Compared with the unmodified resin (PF), the temperature at the maximum decomposing rate of the B-PF resin increases by 54 ℃ and its oxidative residues yield at 1000 ℃ enhances by 17.99 percent. The pyrolyzate of B-PF were further analyzed by XPS and XRD analysis. The analysis indicates that the boron element reacts with the air or oxygen-containing volatiles to generate boron nitride… Show more
“…For BC-30, new peaks were observed at 2 θ = 14.5°, 27.7° and 40.1° which is not observed in other systems. The peaks at 2 θ = 14.5° and 27.7° represent (101) and (021) planes of boron carbide (PDF 65-6874) present in the matrix of the carbon 33 and the peak at 2 θ = 40.1° corresponds to boron oxide (PDF 06-0643). 2 XRD of BC ceramics derived for BPF…”
C f /SiBOC was fabricated from 2D carbon fabric as reinforcement and slurry-containing boronmodified phenol formaldehyde (BPF) resin with silicon as matrix resin using reaction-bonded silicon carbide method. The processing involves synthesis of (BPF) resin by reacting various amount of boric acid with phenol formaldehyde resin, polymer to ceramic transformation at 1450°C under argon atmosphere, with and without silicon, thermal transformation of the polymer matrix composite into a ceramic matrix composite and evaluation of isothermal oxidation for ceramics and its composites at 1000, 1250 and 1500°C. The ceramic studies, confirmed the formation of B 4 C, SiC and SiB 4 (SiBOC) mixed phase and the role of boron as a catalyst for graphitisation of free carbon present in the ceramic. Oxidation of C f /SiBOC composite at various temperatures leads to the formation of borosilicate glass which heals the cracks, hindering the inwards diffusion of oxygen.
“…For BC-30, new peaks were observed at 2 θ = 14.5°, 27.7° and 40.1° which is not observed in other systems. The peaks at 2 θ = 14.5° and 27.7° represent (101) and (021) planes of boron carbide (PDF 65-6874) present in the matrix of the carbon 33 and the peak at 2 θ = 40.1° corresponds to boron oxide (PDF 06-0643). 2 XRD of BC ceramics derived for BPF…”
C f /SiBOC was fabricated from 2D carbon fabric as reinforcement and slurry-containing boronmodified phenol formaldehyde (BPF) resin with silicon as matrix resin using reaction-bonded silicon carbide method. The processing involves synthesis of (BPF) resin by reacting various amount of boric acid with phenol formaldehyde resin, polymer to ceramic transformation at 1450°C under argon atmosphere, with and without silicon, thermal transformation of the polymer matrix composite into a ceramic matrix composite and evaluation of isothermal oxidation for ceramics and its composites at 1000, 1250 and 1500°C. The ceramic studies, confirmed the formation of B 4 C, SiC and SiB 4 (SiBOC) mixed phase and the role of boron as a catalyst for graphitisation of free carbon present in the ceramic. Oxidation of C f /SiBOC composite at various temperatures leads to the formation of borosilicate glass which heals the cracks, hindering the inwards diffusion of oxygen.
“…23 To address the above problems, boron can be introduced into the main chain to modify the high-ortho phenolic resin and improve the thermal stability, mechanical properties, and electrical properties of the resin, and reduce the reactivity. [24][25][26][27][28] Boron-modified phenolic resins have been widely studied and reported. [29][30][31][32][33][34][35][36][37] Sun and Sun 38 investigated the optimization of the critical process parameters for the preparation of boron-containing phenolic resin (B containing PR).…”
Boron-modified high-ortho phenolic resins (BPRs) were prepared under normal pressure by using phenol and formaldehyde as raw materials, zinc acetate, and oxalic acid as catalysts, and boric acid as a modifier. Boron-modified phenolic fibers (BPFs) were prepared by melt spinning and curing in a mixture of formaldehyde and hydrochloric acid, followed by a heat treatment under high temperature. The structure, ortho–para ratio (O/P), molecular weight and distribution, spinnability, thermal stability, fiber strength, and morphology of the resins were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and fiber strength testing. The results showed that the addition of boric acid reduced the ortho reaction of the synthetic resin and the O/P value of phenolic resin. When the content of boric acid was 3 wt%, the thermal stability was the best, the O/P value was up to 3.26, and the weight average molecular weight (Mw) was 18745 g/mol. In Compared with the unmodified resin, the mass loss was increased by 33.7%, and finally the carbon yield was 51.2%. The tensile strength of the fibers reached 187.2 MPa and the elongation at break was 10.5%. By introducing boron into the molecular chain, the structure of the resin was improved, and the thermal stability and mechanical properties of the fibers were improved.
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