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Synthesis and Characterization of a Novel Preceramic Polymer for SiBNC Ceramic Fibers
Chenyu Zhang,Yong Liu,Yongjie Cui,Minqiang Jiang,Keqing Han,Hui Zhang,Muhuo Yu 한국섬유공학회 2018 Fibers and polymers Vol.19 No.5
A new approach for the synthesis of polymer precursor for quaternary SiBNC fibers is presented. The inexpensive, commercially available reactants n-propylamine (C3H7NH2), trichlorosilane (SiHCl3) and boron trichloride (BCl3) were used in a simple one-step reaction. The reaction mainly involved the co-polymerization between Si-Cl, B-Cl and N-CH2CH2CH3 with C3H7NH2 evaporation. Characterization of synthesized polymer was performed by FT-IR and NMR. The polymer has a relatively linear-chain chemical structure, and could be easily converted into flexible green fibers by melt-spun with diameter of 24 μm. After pyrolysis process at 1000 oC under nitrogen atmosphere, SiBNC ceramic fibers were obtained with a diameter of about 19 μm. Those fibers showed average tensile strength of 1.05 GPa and it remained in the amorphous state up to 1600 oC, which made them as the promising candidates for reinforcements in ceramic matrix composites for hightemperature application.
Baodong Liu,Zhenan Zhang,Minqiang Zhang,Xiaoxi Wang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3
This paper presents a comparative study on the composite structure of Corrugated Steel Plate (CSP) with normal and rubberized concrete. One CSP-normal-concrete plate and two CSP arch structures composited with diff erent concretes are established. A theoretical section-property deduction is derived, which demonstrated that the fl exural rigidity of such composite structure increased notably. Static and dynamic mechanical experiments are also conducted. Experimental results agree with expectations, and the measured results on plate structures verifi ed the eff ectiveness of the analytical and numerical solutions. Comparing the defl ection of two composite arches shows that the rubberized concrete composite arch has smaller fl exural and compressive stiff nesses, resulting in larger defl ection. The rubberized concrete composite arch has higher steel stress, lower concrete stress and better energy-dissipating capacity compared with the normal concrete composite arch. Therefore, the CSP-rubberized concrete composite structure is more suitable for anti-shock and earthquake-resistant structures.
Effects of environmental temperature and age on the elastic modulus of concrete
Shuzhen Yang,Baodong Liu,Yuzhong Li,Minqiang Zhang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.6
Concrete mechanical properties change constantly with age, temperature, humidity and the other environmental factors. This research studies the effects of temperature and age on the development of concrete elastic modulus by a series of prism specimens. Elastic modulus test was conducted at various temperatures and ages in the laboratory to examine the effects of temperature and age on it. The experimental results reveal that the concrete elastic modulus decreases with the rise of temperature but increases with age. Then, a temperature coefficient K is proposed to describe the effects of temperature and validated by existing studies. Finally, on the basis of K, analytical models are proposed to determine the elastic modulus of concrete at a given temperature and age. The proposed models can offer designers an approach to obtain more accurate properties of concrete structures through the elastic modulus modification based on actual age and temperature, rather than using a value merely based on laboratory testing.