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A novel kind of g-C3N4 micro-nano bouquets were successfully prepared via a simple method using melamine and ammonium chloride as raw materials. X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), x-ray energy spectrometer (EDX), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM),fourier transform infrared spectrometer (FT-IR) and x-ray photoelectron spectroscopy (XPS) were used to characterize the as-synthesized samples. The results indicated that the samples presented graphitic C3N4 micro-nano bouquets. Every microstructure was composed of many petals cross gathered along with the different directions. And the tip of every single petal contained quantities of nano bouquet structures with smaller diameters. In addition, abundant nanoparticles/nanorods distributed and intertwined together on the surface of the nano bouquet structure, and then formed cocoon-like porous morphology. Besides, based on the experimental results, the reasonable chemical reactions and the corresponding growth mechanism during the preparation process of g-C3N4 micro-nano bouquets were proposed. Finally, the UV–vis results showed that the sample was a wide band gap (about 3.11 eV) semiconductor.

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In this paper, the novel boron nitride micron tubes (BNMTs) were used to reinforce commercial boron carbide (B 4 C) ceramics prepared via spark plasma sintering technology. The effects of the sintering parameters, sintering temperature, the holding time, and the BNMTs content on the microstructure and mechanical properties of B 4 C/BNMTs composite ceramics were studied. The results indicated that adding a proper amount of BNMTs could inhibit the grain growth of B 4 C and improve the fracture toughness of the B 4 C/BNMTs composite ceramics. The prepared composite ceramic sample with 5 wt% BNMTs at 1850 • C, 8 min and 30 MPa displayed the best mechanical properties. The relative density, hardness, fracture toughness, and bending strength of the samples were 99.7% ± .1%, 35.62 ± .43 GPa, 6.23 ± .2 MPa m 1/2 , and 517 ± 7.8 MPa, respectively.Therein, the corresponding value of hardness, fracture toughness, and bending strength was increased by 10.3%, 43.59%, and 61.5%, respectively, than that of the B 4 C/BNMTs composite ceramic without BNMTs. It was proved that the high interface binding energy and bridging effect between boron carbide and BNMTs were the toughening principle of BNMTs.