Effect of heat treatment on microstructure and tensile strength of KD-II SiC fibers in argon and oxidation atmosphere

Huan Yin,Fenghao Yang,Guangmin Hu,Maozhong Yi 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.4

The polycarbosilane derived KD-II SiC fibers were heat treated in argon atmosphere at temperatures from 1000 °C to 1800°C and in oxidation atmosphere at temperatures from 1000 °C to 1500 °C for 1 hour, respectively. The effect of heat treatmenton microstructure of all fibers were characterized by X-ray diffraction, scanning electron microscopy, transmission electronmicroscopy, X-ray photoelectron spectroscopy and Atomic Force Microscopeand, and the tensile strength of fibers wereevaluated by monofilament tensile test and Weibull model. The results reveal that the fibers of heat treatment in argonatmosphere can maintain their original tensile strength (~2.5 GPa) up to the temperature at 1200 °C. After that, their tensilestrength starts to decline, especially when the temperature exceeds 1400 °C a sharp strength degradation is observed. Throughdetailed characterization, we find that the reasons for the strength degradation of fibers heat treatment in argon atmosphereinclude the appearance of surface defects, growth of β-SiC grains and decomposition of SiCxOy amorphous phase. Correspondingly, the fibers heat treated in oxidation atmosphere have lower tensile strength compared with those fibers heattreatment in argon atmosphere at the same temperature. Furthermore, their tensile strength starts to degenerate at 1000 °C,and only 30% of original strength is retained when the temperature reached 1500 °C. Obviously, for fibers heat treatment inoxidation atmosphere, their tensile strength degradation starting temperature is lower and degradation speed is faster thanthose fibers heat treatment in argon atmosphere. This can be attributed to the interface stress existed between silica layer withinternal fibers, the surface cracks caused by the thermal stress and the growth of β-SiC grains.

PIERCE STALKS OF EXCHANGE RINGS

Huanyin Chen 대한수학회 2010 대한수학회지 Vol.47 No.4

We prove, in this article, that a ring R is a stable exchange ring if and only if so are all its Pierce stalks. If every Pierce stalks of R is artinian, then 1R = u + v with u, v ∈ U(R) if and only if for any a ∈ R, there exist u, v ∈ U(R) such that a = u + v. Furthermore, there exists u ∈ U(R) such that 1R ± u ∈ U(R) if and only if for any a ∈ R,there exists u ∈ U(R) such that a ± u ∈ U(R). We will give analogues to normal exchange rings. The root properties of such exchange rings are also obtained.

UNIT-REGULARITY AND STABLE RANGE ONE

Huanyin Chen 대한수학회 2010 대한수학회보 Vol.47 No.3

Let R be a ring, and let Ψ(R) be the ideal generated by the set {x ∈ R | 1 + sxt ∈ R is unit-regular for all s, t ∈ R}. We show that Ψ(R) has “radical-like” property. It is proven that Ψ(R) has stable range one. Thus, diagonal reduction of matrices over such ideal is reduced.

2×2 invertible matrices over weakly stable rings

Huanyin Chen 대한수학회 2009 대한수학회지 Vol.46 No.2

A ring R is a weakly stable ring provided that aR+bR=R implies that there exists y∈R such that a+by∈R is right or left invertible. In this article, we characterize weakly stable rings by virtue of 2×2 invertible matrices over them. It is shown that a ring R is a weakly stable ring if and only if for any A∈GL_2(R), there exist two invertible lower triangular L and K and an invertible upper triangular U such that A=LUK, where two of L,U and K have diagonal entries 1. Related results are also given. These extend the work of Nagarajan et al. A ring R is a weakly stable ring provided that aR+bR=R implies that there exists y∈R such that a+by∈R is right or left invertible. In this article, we characterize weakly stable rings by virtue of 2×2 invertible matrices over them. It is shown that a ring R is a weakly stable ring if and only if for any A∈GL_2(R), there exist two invertible lower triangular L and K and an invertible upper triangular U such that A=LUK, where two of L,U and K have diagonal entries 1. Related results are also given. These extend the work of Nagarajan et al.

ON QUASI-STABLE EXCHANGE IDEALS

Huanyin Chen 대한수학회 2010 대한수학회지 Vol.47 No.1

We introduce, in this article, the quasi-stable exchange ideal for associative rings. If I is a quasi-stable exchange ideal of a ring R, then so is Mn(I) as an ideal of Mn(R). As an application, we prove that every square regular matrix over quasi-stable exchange ideal admits a diagonal reduction by quasi invertible matrices. Examples of such ideals are given as well.

On separative refinement monoids

Huanyin Chen 대한수학회 2009 대한수학회보 Vol.46 No.3

We obtain two new characterizations of separativity of refinement monoids, in terms of comparability-type conditions. As applications, we get several equivalent conditions of separativity for exchange ideals. We obtain two new characterizations of separativity of refinement monoids, in terms of comparability-type conditions. As applications, we get several equivalent conditions of separativity for exchange ideals.

Weakly stable conditions for exchange rings

Huanyin Chen 대한수학회 2007 대한수학회지 Vol.44 No.4

A ring R has weakly stable range one provided that aR +bR = R implies that there exists ay 2 R such that a + by 2 R is rightor left invertible. We prove, in this paper, that every regular elementin an exchange ring having weakly stable range one is the sum of anidempotent and a weak unit. This generalize the corresponding result ofone-sided unit-regular ring. Extensions of power comparability and powercancellation are also studied.1. IntroductionA ring R is said to be an exchange ring if for every rightR-module A andany two decompositionsA = M N =Li2 I Ai, whereMR = RR and I is anite index set, there exist submodulesA0i Ai such thatA = M (Li2 I A0i).It is well known that regular rings,-regular rings, unitC-algebras of realrank zero, semiperfect rings, left or right continuous rings and clean rings areall exchange rings. For general theory of exchange rings, we refer the readersto [10]. Following Wei and Tong (cf. [11]), a ringR is said to have weakly

ON SB-RINGS

Huanyin Chen 대한수학회 2008 대한수학회지 Vol.45 No.3

In this paper, we introduce a new class of rings, SB-rings. Weestablish various properties of this concept. These shows that, in severalrespects, SB-rings behave like rings satisfying unit 1-stable range. Wewill give necessary and sufficient conditions under which a semilocal ringis a SB-ring. Furthermore, we extend these results to exchange ringswith all primitive factors artinian. For such rings, we observe that theconcept of the SB-ring coincides with Goodearl–Menal condition. Thesealso generalize the results of Huh et al., Yu and the author on ringsgenerated by their units

Strongly $\Pi$-regular Morita contexts

Huanyin Chen 대한수학회 2003 대한수학회보 Vol.40 No.1

In this paper, we show that if the ring of a Morita context $(A,B,M,N,\psi ,\phi )$ with zero pairings is a strongly $\pi$-regular ring of bounded index if and only if so are $A$ and $B$. Furthermore, we extend this result to the ring of a Morita context over quasi-duo strongly $\pi$-regular rings.

On exchange ideals

Huanyin Chen 대한수학회 2005 대한수학회보 Vol.42 No.2

In this paper, we investigate exchange ideals and get some newcharacterization of exchange rings. It is shown that an ideal Iof a ring R is an exchange ideal if and only if so is QM_2(I).Also we observe that every exchange ideal can be characterized by