The chemical composition, microstructure, strength, and thermal stability of polymer-derived Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers fabricated by Dow Corning and COI Ceramics, Inc., and nitrogen-treated Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers, referred to as Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} and Super Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} SiC fibers, were investigated and compared. The baseline Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers fabricated by both vendors as well as the nitrogen-treated Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers are composed mostly of beta-SiC(∼97wt%)\beta-\mathrm{SiC}(\sim 97 \mathrm{wt} \%) with small amounts of TiB_(2)(∼2wt%)\mathrm{TiB}_{2}(\sim 2 \mathrm{wt} \%), amorphous carbon ( ∼1wt%\sim 1 \mathrm{wt} \% ) and trace amounts of B_(4)C\mathrm{B}_{4} \mathrm{C}. Most of the amorphous carbon is segregated at the core/interior of the fibers. Both baseline and nitrogen-treated Sylramic ^(TM){ }^{\mathrm{TM}} SiC fibers have similar grain size and pore size distribution, except for a thin layer of in-situ grown crystalline BN (30-70 nm) on the surface of Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} and Super Sylramic ^(TM){ }^{\mathrm{TM}}-iBN fibers. Wide variation in strength within a batch as well as between batches is observed in both baseline and nitrogen-treated Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers but both types of fibers are microstructurally stable at temperatures to 1800^(@)C1800{ }^{\circ} \mathrm{C} in argon and nitrogen environments compared to Nicalon ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} and Tyranno®-SA SiC fibers. Under the same creep condition, Super Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} fibers show better creep resistance compared to Sylramic ^(TM){ }^{\mathrm{TM}}, Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN}, HiNicalon ^("TM ")-S{ }^{\text {TM }}-S, and Tyranno ^(®){ }^{\circledR}-SA fibers. Possible reasons for strength variability and the mechanism of in-situ BN formation on Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers are discussed. 聚合物衍生的 Sylramic 的化学成分、微观结构、强度和热稳定性 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 由 Dow Corning 和 COI Ceramics, Inc. 制造的纤维以及经过氮化处理的 Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 纤维，称为 Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} 和超级系统 ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} 对 SiC 纤维进行了研究和比较。基线 Syramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 两家供应商制造的纤维以及经过氮化处理的 Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 纤维主要由 beta-SiC(∼97wt%)\beta-\mathrm{SiC}(\sim 97 \mathrm{wt} \%) 与少量的 TiB_(2)(∼2wt%)\mathrm{TiB}_{2}(\sim 2 \mathrm{wt} \%) ，无定形碳（ ∼1wt%\sim 1 \mathrm{wt} \% ）和微量的 B_(4)C\mathrm{B}_{4} \mathrm{C} 。大多数无定形碳偏析在纤维的芯/内部。基线和氮处理的Sylramic ^(TM){ }^{\mathrm{TM}} SiC纤维具有相似的晶粒尺寸和孔径分布，除了Sylramic表面上的一薄层原位生长的晶体BN（30-70 nm） ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} 和超级系统 ^(TM){ }^{\mathrm{TM}} -iBN纤维。在基线和氮处理的 Sylramic 中观察到批次内以及批次之间的强度差异很大 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 纤维，但两种类型的纤维在一定温度下微观结构均稳定 1800^(@)C1800{ }^{\circ} \mathrm{C} 与尼卡龙相比，在氩气和氮气环境中 ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} 和 Tyranno®-SA 碳化硅纤维。在相同蠕变条件下，Super Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} 与 Sylramic 纤维相比，纤维表现出更好的抗蠕变性 ^(TM){ }^{\mathrm{TM}} , 系统 ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} , 海尼卡隆 ^("TM ")-S{ }^{\text {TM }}-S ，和泰拉诺 ^(®){ }^{\circledR} -SA纤维。强度变异的可能原因以及 Sylramic 上原位 BN 形成的机制 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 讨论了纤维。
1. Introduction 一、简介
For the development of next generation SiC//SiC\mathrm{SiC} / \mathrm{SiC} composites for turbine applications, small diameter SiC fibers ( < 20 mum<20 \mu \mathrm{~m} ) are required that are microstructurally stable not only during fabrication, but also during use conditions of the composites. In addition, the reinforcing fibers should also display better creep resistance and strain-to-failure capability than the composite matrix to achieve required creep and cyclic durability in the composites. A variety of polymer-derived SiC fibers with wide variation in moduli and creep resistances have been commercially produced, but none have creep resistance equivalent to or better than chemically vapor deposited (CVD) SiC, which exhibits a steady-state creep rate of 10^(-9)10^{-9} to 10^(-10)10^{-10} /s at 1400^(@)1400^{\circ} Cat stresses up to 275 MPa [1,2]. 为了下一代的发展 SiC//SiC\mathrm{SiC} / \mathrm{SiC} 用于涡轮机应用的复合材料、小直径 SiC 纤维（ < 20 mum<20 \mu \mathrm{~m} ）不仅在制造过程中而且在复合材料的使用条件下都要求微观结构稳定。此外，增强纤维还应表现出比复合材料基体更好的抗蠕变性和应变失效能力，以实现复合材料所需的蠕变和循环耐久性。各种聚合物衍生的碳化硅纤维在模量和抗蠕变性方面差异很大，但没有一种具有与化学气相沉积 (CVD) 碳化硅相当或更好的抗蠕变性，化学气相沉积 (CVD) 碳化硅的稳态蠕变速率为 10^(-9)10^{-9} 到 10^(-10)10^{-10} /秒在 1400^(@)1400^{\circ} Cat 应力高达 275 MPa [1,2]。
The first generation of small diameter polymer-derived SiC fibers was based on melt spinnable polycarbosilane (PCS) and polytitanocarbosilane (PTC) polymer compositions that were developed by 第一代小直径聚合物衍生的 SiC 纤维基于可熔融纺丝的聚碳硅烷 (PCS) 和聚钛碳硅烷 (PTC) 聚合物组合物，这些聚合物组合物由
Yajima et al. in the early 1970 s [3,4]. In the 1980 s, these fibers were commercially produced by Nippon Carbon and Ube companies, Tokyo, Japan as CG Nicalon ^("TM "){ }^{\text {TM }} and Tyranno ^(®){ }^{\circledR} LoxM SiC fibers, respectively and are essentially composed of silicon oxycarbide (SIOC) phase [5-9]. However, this phase at temperatures > 1000^(@)C>1000^{\circ} \mathrm{C} decomposed and caused significant loss in strength as well as modulus [10-12]. 矢岛等人。 20 世纪 70 年代初 [3,4]。 20 世纪 80 年代，这些纤维由日本东京的 Nippon Carbon 和 Ube 公司进行商业化生产，名称为 CG Nicalon ^("TM "){ }^{\text {TM }} 和泰拉诺 ^(®){ }^{\circledR} LoxM SiC 纤维分别主要由碳氧化硅 (SIOC) 相组成 [5-9]。然而，这个阶段在温度 > 1000^(@)C>1000^{\circ} \mathrm{C} 分解并导致强度和模量显着损失[10-12]。
To reduce silicon oxycarbide phase and improve thermal stability, the spun PCS and PTC precursor fibers were cured in the electron beam, pyrolyzed under anaerobic conditions, and then densified in a controlled environment [13-15]. The resulting fibers consists of beta\beta-SiC crystallites, free-carbon aggregates, and a poorly organized intergranular phase of silicon and carbon atoms [16,17][16,17]. This led to commercialization of second generation SiC fibers, Hi-Nicalon ^(TM){ }^{\mathrm{TM}} and Tyranno ^(®){ }^{\circledR} LoxE. Although, the second generation SiC fibers exhibited slightly better thermal stability than the first generation SiC fibers, they still degraded in strength and showed poor creep resistance at temperatures > 1300^(@)C>1300^{\circ} \mathrm{C} due to residual SiOC and free-carbon phases [18,19][18,19]. 为了减少碳氧化硅相并提高热稳定性，纺成的PCS和PTC前体纤维在电子束中固化，在厌氧条件下热解，然后在受控环境中致密化[13-15]。所得纤维由以下组成 beta\beta -SiC 微晶、游离碳聚集体以及组织不良的硅和碳原子晶间相 [16,17][16,17] 。这导致了第二代 SiC 纤维 Hi-Nicalon 的商业化 ^(TM){ }^{\mathrm{TM}} 和泰拉诺 ^(®){ }^{\circledR} 洛克斯E。尽管第二代SiC纤维的热稳定性比第一代SiC纤维稍好，但它们的强度仍然下降，并且在一定温度下的抗蠕变性较差 > 1300^(@)C>1300^{\circ} \mathrm{C} 由于残留的 SiOC 和游离碳相 [18,19][18,19] 。
To develop fully crystalline, near stoichiometric, creep resistant polymer-derived SiC fibers, different processing routes were followed after spinning PCS and PTC polymer and curing the polymer fiber either by electron beam irradiation or by a combination of oxidizing and reducing environments to significantly reduce or completely eliminate SiOC phase and excess carbon. This effort resulted in the development of third generation SiC fibers such as Hi-Nicalon ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} from Nippon Carbon, Sylramic ^(TM){ }^{\mathrm{TM}} from Dow Corning, and Tyranno®-SA from Ube Industries. 为了开发完全结晶、接近化学计量、抗蠕变的聚合物衍生 SiC 纤维，在纺丝 PCS 和 PTC 聚合物并通过电子束辐照或通过氧化和还原环境的组合来固化聚合物纤维后，采用了不同的加工路线，以显着减少或减少彻底消除SiOC相和多余的碳。这项努力促成了第三代 SiC 纤维的开发，例如 Hi-Nicalon ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} 来自 Nippon Carbon、Sylramic ^(TM){ }^{\mathrm{TM}} 来自道康宁 (Dow Corning) 的Tyranno®-SA，以及来自宇部兴产 (Ube Industries) 的 Tyranno®-SA。
Nippon Carbon used the first two processing steps similar to those of Hi-Nicalon ^("TM "){ }^{\text {TM }} SiC fibers (i.e., spinning of PCS polymer into fibers and curing the fibers in electron beam radiation), but then the fiber was heat treated in a hydrogen environment to reduce the carbon content from a C//Si\mathrm{C} / \mathrm{Si} atomic ratio from 1.39 to 1.05 near stoichiometric ratio and further sintered at higher temperatures to achieve polycrystalline ceramic fibers [20,21]. Nippon Carbon 使用了与 Hi-Nicalon 类似的前两个处理步骤 ^("TM "){ }^{\text {TM }} SiC纤维（即将PCS聚合物纺成纤维并在电子束辐射下固化纤维），但随后将纤维在氢气环境中进行热处理以减少碳含量 C//Si\mathrm{C} / \mathrm{Si} 原子比从1.39到1.05接近化学计量比并进一步在更高温度下烧结以获得多晶陶瓷纤维[20,21]。
Ube Industries explored the potential of controlling the chemistry of the PCS by grafting a metal into its chemical structure and developed a polyaluminocarbosilane, synthesized by reaction of aluminum acetylacetonate with PCS. The addition of aluminum in the PCS chains is considered to help the cross-linking of the polymeric fibers and also plays an important role as a sintering aid [22,23]. By this route, amorphous SiAlCO fibers are obtained after spinning polymer polyaluminocarbosilane, curing the green fibers in air, and pyrolyzing the fibers at temperatures to 1300^(@)C1300^{\circ} \mathrm{C} under inert gas. The resulting ceramic SiAlCO fibers are densified by sintering at temperatures > 1700^(@)C>1700{ }^{\circ} \mathrm{C}. Additions of aluminum claimed to favor formation of a smooth surface and densified SiC during the sintering process [24]. This fiber is commercialized as Tyranno®-SA3 SiC fibers. 宇部工业公司探索了通过将金属接枝到其化学结构中来控制 PCS 化学的潜力，并开发了一种聚铝碳硅烷，该聚铝碳硅烷是通过乙酰丙酮铝与 PCS 反应合成的。在PCS链中添加铝被认为有助于聚合物纤维的交联，并且作为烧结助剂也发挥着重要作用[22,23]。通过该路线，将聚合物聚铝碳硅烷纺丝，在空气中固化绿色纤维，并在一定温度下热解纤维，得到非晶态 SiAlCO 纤维。 1300^(@)C1300^{\circ} \mathrm{C} 在惰性气体下。所得陶瓷 SiAlCO 纤维通过在一定温度下烧结而致密化 > 1700^(@)C>1700{ }^{\circ} \mathrm{C} 。据称，添加铝有利于在烧结过程中形成光滑的表面和致密的 SiC [24]。这种纤维作为 Tyranno®-SA3 SiC 纤维进行商业化。
Dow Corning, in the late 1980s, used commercially available Tyr-anno®-LoxM SiC fibers from Ube Industries as a precursor for fabrication of fully crystalline, near stoichiometric SiC fiber. Dow Corning fabricated the SiC fiber by a batch process of deoxidation of Tyranno®LoxM SiC fiber in B_(2)O_(3)\mathrm{B}_{2} \mathrm{O}_{3} and an argon environment, and then sintering the fiber in an argon environment at ∼1800^(@)C\sim 1800^{\circ} \mathrm{C} [25]. This fiber is fully crystalline, near stoichiometric SiC , and contains minor phases of TiB_(2)\mathrm{TiB}_{2} and carbon. Dow Corning later commercialized this fiber as Sylramic ^(TM){ }^{\mathrm{TM}} SiC fiber. This fiber is currently fabricated by COI Ceramics, Inc. (henceforth COIC). To improve their environmental stability and creep resistance, these fibers were heat treated in a nitrogen environment at 1800^(@)C1800^{\circ} \mathrm{C} to create a thin layer of in-situ BN coating on the fiber surface [26]. The in-situ BN coating can be created by heat treating Sylramic ^(TM){ }^{\mathrm{TM}} fibers either in 0.1MN//m^(2)0.1 \mathrm{MN} / \mathrm{m}^{2} flowing N_(2)\mathrm{N}_{2} gas or in 3.52MN//m^(2)3.52 \mathrm{MN} / \mathrm{m}^{2} static N_(2)\mathrm{N}_{2}. Although the mechanism of the in-situ BN formation on the fiber surface is not clearly known, it is hypothesized that as-fabricated Sylramic ^(TM){ }^{\mathrm{TM}} fiber contains excess free boron, and when the fiber is heat treated at high temperatures in a N_(2)\mathrm{N}_{2} environment, the excess boron migrates to the fiber surface and reacts with N_(2)\mathrm{N}_{2} to form a BN coating [26] 道康宁公司在 20 世纪 80 年代末使用宇部工业公司 (Ube Industries) 的市售 Tyr-anno®-LoxM SiC 纤维作为制造全结晶、接近化学计量的 SiC 纤维的前体。道康宁通过 Tyranno®LoxM SiC 纤维的间歇脱氧工艺制造了 SiC 纤维。 B_(2)O_(3)\mathrm{B}_{2} \mathrm{O}_{3} 和氩气环境，然后在氩气环境中在 ∼1800^(@)C\sim 1800^{\circ} \mathrm{C} [25]。这种纤维是完全结晶的，接近化学计量的 SiC，并含有少量的相 TiB_(2)\mathrm{TiB}_{2} 和碳。道康宁后来将这种纤维商业化，命名为 Sylramic ^(TM){ }^{\mathrm{TM}} 碳化硅纤维。这种纤维目前由 COI Ceramics, Inc.（以下简称 COIC）制造。为了提高其环境稳定性和抗蠕变性，这些纤维在氮气环境中进行了热处理 1800^(@)C1800^{\circ} \mathrm{C} 在纤维表面形成一层薄薄的原位 BN 涂层 [26]。原位 BN 涂层可通过热处理 Sylramic 形成 ^(TM){ }^{\mathrm{TM}} 纤维要么在 0.1MN//m^(2)0.1 \mathrm{MN} / \mathrm{m}^{2} 流动的 N_(2)\mathrm{N}_{2} 气体或在 3.52MN//m^(2)3.52 \mathrm{MN} / \mathrm{m}^{2} 静止的 N_(2)\mathrm{N}_{2} 。尽管纤维表面上原位 BN 形成的机制尚不清楚，但假设所制造的 Sylramic ^(TM){ }^{\mathrm{TM}} 纤维含有过量的游离硼，当纤维在高温下进行热处理时 N_(2)\mathrm{N}_{2} 环境中，多余的硼迁移到纤维表面并与 N_(2)\mathrm{N}_{2} 形成BN涂层[26]
The chemical composition, microstructure, strength, and creep resistance of as-fabricated and heat-treated Hi-Nicalon ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} and Tyr-anno®-SA SiC fibers have been investigated [27-35]. Similarly, the strength and creep resistance of Dow Corning as-fabricated Sylramic ^(TM){ }^{\mathrm{TM}} SiC and nitrogen-treated Sylramic ^(TM){ }^{\mathrm{TM}} SiC fibers, referred to as Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} fibers have been studied [36-40]. However, untreated and nitrogen-treated Sylramic ^(TM){ }^{\mathrm{TM}} SiC fibers have not been fully characterized. Currently, there is significant variation in the strength of Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers fabricated by COIC from batch-to-batch and within a batch. It is not clear whether this variability is caused by manufacturing issues at the current vendor or preexisted even when the fibers were fabricated by Dow Corning. Therefore, understanding the source of strength variability and improving strength of these fibers is critical for development of ceramic matrix composites (CMCs). In addition, nitrogen-treated Sylramic ^("TM "){ }^{\text {TM }} SiC fibers show potential for development of CMCs at temperatures to 1482^(@)C1482^{\circ} \mathrm{C} compared to other third generation SiC fibers, but the mechanism for in-situ BN formation and thermal stability of nitrogen-treated Sylramic ^("TM "){ }^{\text {TM }} SiC fibers are unknown [38,39][38,39]. Also if in-situ BN coating on Sylramic ^("TM "){ }^{\text {TM }} SiC fibers can be grown to thickness 制造和热处理后的 Hi-Nicalon 的化学成分、微观结构、强度和抗蠕变性 ^(TM)-S{ }^{\mathrm{TM}}-\mathrm{S} 和 Tyr-anno®-SA SiC 纤维已得到研究 [27-35]。同样，道康宁制造的 Sylramic 的强度和抗蠕变性 ^(TM){ }^{\mathrm{TM}} SiC 和氮化处理的 Syramic ^(TM){ }^{\mathrm{TM}} SiC纤维，简称Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN} 纤维已被研究[36-40]。然而，未经处理和氮处理的Sylramic ^(TM){ }^{\mathrm{TM}} SiC 纤维尚未完全表征。目前，Sylramic的强度存在显着差异 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} COIC 在批次间和批次内制造的纤维。目前尚不清楚这种变化是由当前供应商的制造问题引起的，还是在纤维由道康宁公司制造时就已经存在了。因此，了解强度变异的来源并提高这些纤维的强度对于陶瓷基复合材料（CMC）的开发至关重要。此外，经过氮处理的Sylramic ^("TM "){ }^{\text {TM }} SiC 纤维显示出在以下温度下开发 CMC 的潜力： 1482^(@)C1482^{\circ} \mathrm{C} 与其他第三代 SiC 纤维相比，但氮化处理的 Sylramic 的原位 BN 形成机制和热稳定性 ^("TM "){ }^{\text {TM }} SiC纤维尚不清楚 [38,39][38,39] 。另外，如果在 Sylramic 上进行原位 BN 涂层 ^("TM "){ }^{\text {TM }} SiC 纤维可以生长至一定厚度 ∼0.5 mum\sim 0.5 \mu \mathrm{~m} by controlling the heat-treatment conditions, then the need for deposition of additional chemical vapor infiltration (CVI) BN coating during fabrication of composites can be avoided. ∼0.5 mum\sim 0.5 \mu \mathrm{~m} 通过控制热处理条件，可以避免在复合材料制造过程中沉积额外的化学气相渗透（CVI）BN涂层。
The objectives of this study are several: first, to compare the composition, microstructure, and strength of Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers as fabricated by Dow Corning and COIC, and nitrogen-treated Sylramic ^(TM){ }^{\mathrm{TM}} SiC fibers; second, to determine factors controlling strength variability between batches as well as within the batch of Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers fabricated by COIC; third, to study the possible mechanism of in-situ BN formation; and lastly, to measure creep resistance and thermal stability of nitrogen-treated Sylramic ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} fibers. 这项研究的目的有几个：首先，比较 Sylramic 的成分、微观结构和强度 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 由 Dow Corning 和 COIC 制造的纤维以及经过氮化处理的 Sylramic ^(TM){ }^{\mathrm{TM}} 碳化硅纤维；其次，确定控制批次之间以及批次内 Sylramic 强度变异性的因素 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} COIC制造的纤维；第三，研究原位BN形成的可能机制；最后，测量经过氮化处理的 Sylramic 的抗蠕变性和热稳定性 ^(TM)SiC{ }^{\mathrm{TM}} \mathrm{SiC} 纤维。
2. Material and characterization methods 2 材料及表征方法
2.1. Material and fiber heat-treatment 2.1.材料和纤维热处理
Several batches of Sylramic ^("TM "){ }^{\text {TM }} SiC fibers were purchased from two different fiber vendors: Dow Corning, Midland, MI and COIC, Long Beach, CA. The as-fabricated fiber tows had a polyvinyl alcohol (PVA) sizing. For brevity, these fibers are referred to as Sylramic ^("TM "){ }^{\text {TM }} fibers from now on. For all characterization work, the as-fabricated fiber tows were heat treated in argon at 1100^(@)C1100^{\circ} \mathrm{C} for 2 h to remove PVA sizing, and for tow strength measurement, desized tows were resized with uniform layer of PVA. 多批次Sylramic ^("TM "){ }^{\text {TM }} SiC 纤维购自两个不同的纤维供应商：密歇根州米德兰的道康宁公司和加利福尼亚州长滩的 COIC。制成的纤维丝束具有聚乙烯醇（PVA）浆料。为简便起见，这些纤维被称为 Sylramic ^("TM "){ }^{\text {TM }} 纤维从现在开始。对于所有表征工作，将制造好的纤维束在氩气中进行热处理，温度为 1100^(@)C1100^{\circ} \mathrm{C} 2小时以除去PVA浆料，并且为了测量丝束强度，将退浆的丝束用均匀的PVA层重新上浆。
To create a thin layer of in-situ BN coating on fiber surface, ∼1.3m\sim 1.3 \mathrm{~m} Sylramic ^(TM){ }^{\mathrm{TM}} fiber tow was wrapped on a graphite mandrel, and then heat treated in a graphite-lined furnace in 0.1MN//m^(2)0.1 \mathrm{MN} / \mathrm{m}^{2} flowing N_(2)\mathrm{N}_{2} gas or in a hot isostatic press (HIP) under 3.52MN//m^(2)3.52 \mathrm{MN} / \mathrm{m}^{2} static N_(2)\mathrm{N}_{2} gas at 1800^(@)C1800^{\circ} \mathrm{C} for 1 hh as described in the patent [26]. Henceforth, the Sylramic ^("TM "){ }^{\text {TM }} fibers heat treated in 0.1MN//m^(2)0.1 \mathrm{MN} / \mathrm{m}^{2} flowing N_(2)\mathrm{N}_{2} gas, and 3.52MN//m^(2)3.52 \mathrm{MN} / \mathrm{m}^{2} static N_(2)\mathrm{N}_{2} are referred to as Sylramic ^(TM)-iBN{ }^{\mathrm{TM}}-\mathrm{iBN}