The fiber was then directly pyrolyzed up to 1000°C in an ammonia gas flow and was further sintered up to 1800°C in a nitrogen flow. spectra and characteristic frequencies of inorganic ions. In the paper, the braided silica fiber reinforced silicon nitride and boron nitride amorphous composites (SiO2f/Si3N4–BN) was prepared through repeated infiltration of hybrid preceramic precursor and pyrolysis at high temperature in ammonia atmosphere. Elemental analyses and the spectroscopic data indicate that the resulting DEA-PB, DPA-PB, and HMD-PB polymers contain boron-bonded amino groups attached to the polyborazylene backbone. >65 wt %. 2,4,6-Trichloroborazine has been recognized as a desirable monomer for the preparation of high-performance boron nitride fibers through polymer derived ceramics route. After polymer-to-ceramic conversion, the mechanical performances of the ensuing BN fibers are analyzed in relation with the structure of the corresponding thermoplastic polymers. It was found that the yield of TCB could reach 98% using toluene as solvent. The infrared spectra and X-ray diffraction patterns of the aminoborazines are recorded. The structural evolution and chemical composition change during pyrolysis were characterized by chemical analysis, thermal gravimetry–mass spectrometry (TG–MS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The1H NMR spectrum of TAB purified by sublimation revealed that TAB forms a dimer in solution with coordination between B and N atoms at four sites. BN / 39 / fibers with poor mechanical properties were produced / 40 / [6]. The DEA-PB and DPA-PB polymers have lower molecular weights than the starting PB, with the highest amine concentrations in the lower molecular weight fractions, suggesting some backbone scission occurs during polymer modification. Water diffusion in fiber reinforced ceramic composites could reduce the flexural strength as a result of weakened fiber/matrix binding. The precursor was obtained as an intermediate material by the reaction of KBH4 and NH4Cl at 120 °C for 48 h. h-BN was obtained by heating the intermediate material at 1250 °C for 10 h. The sample obtained was characterized by X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetry (TG/DTA) and environment scanning electron microscopy (ESEM), which matched with h-BN. Based on fiber shape visualization using CCD camera during extrusion, appreciable melt-spinnable compounds are prepared between 160 and 185 °C. A polymer–mineral transition occurs since 400 to give amorphous hydrogenated fibers at 1000 °C. The preceramic polymer was composed of B3N3 hexagons linked mainly with = NCH2– units and had a chemical formula of BC2.4N1.63H8.6. 388 The results indicate that N-H, C-H, C-N bonds and B3N3 units exist in the structure of PTPiAB. 7, similar to the previous study, ... [9][10][11][12][13][14][15][16][17] On the other hand, there has been long standing interest in inorganic polymers containing B, Al, and Si in the polymer backbone. The chemical tailoring of BN or SIBCN molecular and polymeric precursors, achieved by the introduction of plasticizing pendent groups such as Si-CH3 and NCH3/N(H)CH3 in the structure, has been shown to improve the melt-spinnability of preceramic polymers. Melt-spinning of these three polymeric precursors exemplified that their ease of processing increases in the order 4 < 5 < 6. ... As one of the easily synthesized polymeric precursors to BN, poly[tris(methyalmino)borane] (PTMB) exhibited great potential in fabricating complex BN devices, such as fibers and coatings [13][14][15][16][17][18][19]. The melting point is 70°C. Trialkynylborazines have been prepared in excellent yields by reacting alkynyl-bis(diisopropylamino)borane with powdered ammonium chloride in toluene. This reaction is stereoselective and gives the β-isomers as major product. The microtexture of the fibers was featureless as glassy-like materials when fibers were exposed at temperatures below 1400°C. 3a) []. By continuing you agree to the use of cookies. Number of times cited according to CrossRef: 53. They report herein the simple high-yield synthesis of a new soluble poly(borazylene) polymer that has proven to be an almost ideal chemical precursor to boron nitride. Upon further heating to 1500°C, the microstructure changed from disordered nanocrystals embedded into an amorphous phase to a turbostratic phase. Borazine offers the advantage of being a colorless liquid with an adequate vapor pressure, which is used as a spray-pyrolysis precursor for the synthesis of BN NPs. IntroductionExperimental SectionResults and DiscussionConclusions. The X-ray diffraction, TEM and pore size analysis show that the structure of the materials consists in a mesoporous boron nitride with some intergranular macroporosity. / 56 / Up to now, the mechanisms which govern both the / 57 / fabrication of the ceramic fibers and the evolution of / 58 / their behavior during pyrolysis annealing are not well-/ 59 / established. Engineering ceramics in the system Si–O–C–N–B manufactured from preceramic silicon containing polymers gain in significance with increasing availability of advanced precursor materials such as poly(carbosilane), -(silazane), -(siloxane) or -(borosilazane). The present chapter describes the methodology which has been employed to convert preceramic polymers into group III nitride materials. Among this, [2-n-propylamino-4,6-bis(methylamino)]borazine (PAB) derived polymer (PPAB) has become an attractive precursor to BN fibers. / Here we reported the facile synthesis of hexagonal boron nitride (h-BN) fibers for efficient removal of methylene blue (MB) from water. Initial stages of degradation were accompanied by liberation of ammonia in addition to the expected aniline or methylamine; this was most pronounced for the methyl borazine. Pyrolyses of B-triamino-N-triphenyl-, B-triamino-N-trimethyl-, and B-trianilino-borazines were performed between 150 and 300°C. Tri(methylamino)borazine (MAB) is converted to BN inside the mesopores of silica or carbon molecular sieves through a mild thermal process. The DPA-PB polymers were melt-spun using a crude ram extruder to yield continuous polymer fibers 30−40 μm in diameter. 382, / [16] M. Hubacek, M. Ueki, T. Sato, V. Brozek, Thermochim. The B-triamino-, B-tris-(methylamino)-, and B-tris-(dimethylamino)- derivatives of N-trimethyl- and N-triphenylborazine have been prepared and characterized. The thermal decomposition, i.e., pyrolysis, of inorganic/organometallic polymers (preceramic polymers) in an oxygen-free atmosphere is a chemical process which is implemented to prepare the so-called Polymer-Derived Ceramics (PDCs). Their microstructure/microtexture was studied by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy investigations. The evolution of composition and structure of precursor PABZ into BN ceramic during curing and pyrolysis process was investigated by FTIR, TG, XRD techniques and chemical analysis. Boron nitride (BN) fibers were efficiently prepared from a B-aminoborazine-based polymer according to the Polymer-Derived Ceramic (PDC) route via melt-spinning and heat-treatments up to 1800°C in a controlled atmosphere. After cured treatment the thermal pyrolysis of PABZ in ammonia atmosphere was took place, and inorganic degree and crystallinity of products were better, which was more suitable for preparation of high purity hexagonal BN (h-BN) ceramic. Therefore, the fiber strength increased, while the fiber modulus also increased because of an improvement of the basal layer orientation along the fiber axis. A series of boron nitride fibers were prepared by varying the tension applied on a same lot of poly(methylamino)borazine fibers during their pyrolytic conversion at 1800°C. Am. The softening point (Ts) can be adjusted according to the equation Ts = 1.43Tsyn – 125.7, in which the Tsyn was between 130°C and 170°C. The carbon template elimination is carried out by thermal treatment under air or under ammonia. Boron nitride is obtained after the removal of the hard template using an ammonia thermal treatment (carbon template) or an HF treatment (silica template). In general, borazine pyrolysis and NH 3-BH 3 CVD yield monolayer or uneven bilayer films, as the completion of the first h-BN layer yields a surface with a sharply lower sticking/reaction probability relative to the original (usually transition metal) substrate. The chemical composition of samples analyzed by X-ray Photoelectron Spectroscopy (XPS) gives a B/N ratio close to 1. Mechanical properties of such amorphous fibers were poor at these temperatures.

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