The preparation of dense Si_(3)N_(4)-based ceramics has attracted great attention because of the achievable improvements in their mechanical properties and high-temperature oxidation resistance.In this work,advanced d...The preparation of dense Si_(3)N_(4)-based ceramics has attracted great attention because of the achievable improvements in their mechanical properties and high-temperature oxidation resistance.In this work,advanced dense boron-containingα/β-Si_(3)N_(4)/Si monoliths were prepared via a high pressure‒high temperature technique in which polymer-derived amorphous SiBN powders were used as raw materials.The crystallization behavior and phase transformation of the polymer-derived amorphous samples were studied in the temperature range from 1400 to 1800℃.The results demonstrate that the incorporation of boron in the Si_(3)N_(4)matrix suppresses the phase transformation fromα-Si_(3)N_(4)toβ-Si_(3)N_(4).Furthermore,the mechanical properties of the as-prepared samples were measured,and the maximum hardness and fracture toughness of boron-rich SiBN samples reached 14.8 GPa and 7.96 MPa·m1/2,respectively.The hardness of the obtained boron-rich SiBN samples is stable up to 300℃.In addition,the oxidation behavior of the samples prepared at 1400 and 1600℃ was investigated at 1400℃ for 50 h.The results show that the incorporation of boron significantly improved the oxidation resistance of the samples because of the formation of borosilicate/cristobalite.This work provides guidance for the synthesis of boron-containingα/β-Si_(3)N_(4)-based ceramics with excellent mechanical properties and oxidation resistance.展开更多
Polyaniline nanofibers （PANI NFs） are introduced to construct a wind-driven triboelectric nanogenerator （TENG） as a new power source for self-powered cathodic protection. PANI NFs serve as a friction layer to gene...Polyaniline nanofibers （PANI NFs） are introduced to construct a wind-driven triboelectric nanogenerator （TENG） as a new power source for self-powered cathodic protection. PANI NFs serve as a friction layer to generate charges by harvesting wind energy as well as a conducting layer to transfer charges in TENG. A PANI NFs-based TENG exhibits a high output performance with a maximum output voltage of 375 V, short current circuit of 248 μA, and corresponding power of 14.5 mW under a wind speed of 15 m/s. Additionally, a self-powered anticorrosion system is constructed by using a PANI-based TENG as the power source. The immersion experiment and electrochemical measurements demonstrate that carbon steel coupled with the wind-driven TENG is effectively protected with an evident open circuit potential drop and negative shift in the corrosion potential. The smart self-powered device is promising in terms of applications to protect metals from corrosion by utilizing wind energy in ambient conditions.展开更多
基金support from the National Natural Science Foundation of China(No.12204254)the Natural Science Foundation of Zhejiang Province(No.LQ23A040005)+1 种基金the Program for Science and Technology Innovation Team in Zhejiang(No.2021R01004)support from the Technical University of Darmstadt,Germany.Zhaoju Yu thanks the Natural Science Foundation of China(Nos.51872246 and 52061135102)for financial support.
文摘The preparation of dense Si_(3)N_(4)-based ceramics has attracted great attention because of the achievable improvements in their mechanical properties and high-temperature oxidation resistance.In this work,advanced dense boron-containingα/β-Si_(3)N_(4)/Si monoliths were prepared via a high pressure‒high temperature technique in which polymer-derived amorphous SiBN powders were used as raw materials.The crystallization behavior and phase transformation of the polymer-derived amorphous samples were studied in the temperature range from 1400 to 1800℃.The results demonstrate that the incorporation of boron in the Si_(3)N_(4)matrix suppresses the phase transformation fromα-Si_(3)N_(4)toβ-Si_(3)N_(4).Furthermore,the mechanical properties of the as-prepared samples were measured,and the maximum hardness and fracture toughness of boron-rich SiBN samples reached 14.8 GPa and 7.96 MPa·m1/2,respectively.The hardness of the obtained boron-rich SiBN samples is stable up to 300℃.In addition,the oxidation behavior of the samples prepared at 1400 and 1600℃ was investigated at 1400℃ for 50 h.The results show that the incorporation of boron significantly improved the oxidation resistance of the samples because of the formation of borosilicate/cristobalite.This work provides guidance for the synthesis of boron-containingα/β-Si_(3)N_(4)-based ceramics with excellent mechanical properties and oxidation resistance.
基金Thanks for the financial support of the National Natural Science Foundation of China （Nos. 21573259 and 21603242）, the outstanding youth fund of Gansu Province （No. 1606RJDA31） and the ＂Hundred Talents Program＂ of Chinese Academy of Sciences （D. A. W.）.
文摘Polyaniline nanofibers （PANI NFs） are introduced to construct a wind-driven triboelectric nanogenerator （TENG） as a new power source for self-powered cathodic protection. PANI NFs serve as a friction layer to generate charges by harvesting wind energy as well as a conducting layer to transfer charges in TENG. A PANI NFs-based TENG exhibits a high output performance with a maximum output voltage of 375 V, short current circuit of 248 μA, and corresponding power of 14.5 mW under a wind speed of 15 m/s. Additionally, a self-powered anticorrosion system is constructed by using a PANI-based TENG as the power source. The immersion experiment and electrochemical measurements demonstrate that carbon steel coupled with the wind-driven TENG is effectively protected with an evident open circuit potential drop and negative shift in the corrosion potential. The smart self-powered device is promising in terms of applications to protect metals from corrosion by utilizing wind energy in ambient conditions.
