CN109180209A - 一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法 - Google Patents
一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法 Download PDFInfo
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Abstract
本发明公开了一种采用原位自生法制备碳化硅纳米线增强石墨‑碳化硅复合材料的方法,该方法将所需量的纳米碳化硅颗粒、白砂糖粉、纳米二氧化硅粉和石墨粉混合后在高温加压条件下通过碳热还原反应,制备出以石墨和碳化硅复合相为基体,碳化硅纳米线为增强体的陶瓷基复合材料。本发明制备方法制得的复合材料利用原位自生技术,在复合粉体上直接生成弥散分布的碳化硅纳米线(SiCnw)增强体,生产成本低,比单一的SiC材料和石墨材料具有更优越的耐磨性能和力学性能。
Description
技术领域
本发明涉及一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,属于冶金技术领域。
背景技术
现代碳化硅(SiC)陶瓷基复合材料具有耐高温、耐磨损、耐腐蚀、高硬度以及质量轻等优良特点,可以承受传统金属材料难以胜任的严酷工作环境,这就大大降低了汽车、机械、石油化工等工业领域耐热、耐磨、耐腐蚀部件对钴(Co)、锗(Ge)、钨(W)、锰(Mn)和铂(Pt)等贵重金属的依赖。另外,在航空、航天等国防领域,对轻质、耐热、高强复合材料、陶瓷材料的运用将直接导致飞行器有效载荷的增加和能耗的降低。但是,目前SiC陶瓷材料存在着脆性大的弱点,很容易因存在裂纹、孔隙、杂质等细微缺陷而破碎,引起不可设想的恶果。通过在SiC陶瓷基复合材料中加入SiCnw增强体,使得SiC陶瓷基复合材料的断裂韧性和塑性大大提高,解决SiC陶瓷基复合材料的增韧问题。石墨和石墨制品具有超强的耐高温性、良好的导热性、抗热震性、化学稳定性和抗侵蚀等性能,被广泛地应用在冶金、化工、高能物理、航天、电子等方面,可以作为耐火砖、坩埚、增碳剂、电极、润滑剂和半金属摩擦材料等等。一种采用原位自生法制备碳化硅纳米线/(石墨-碳化硅)复合材料的方法的开发很有必要,该方法制得的碳化硅纳米线/(石墨-碳化硅)复合材料比单一SiC和石墨材料具有更优越的耐磨性能和力学性能,在高温、高压或高速等恶劣的工作环境中具有更广泛的应用前景。
发明内容
发明目的:本发明所要解决的技术问题是提供一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,该方法制得的碳化硅纳米线增强石墨-碳化硅复合材料比单一的SiC和石墨材料具有更优越的耐磨性能和力学性能。
发明内容:为解决上述技术问题,本发明所采用的技术方案为:
一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,该方法将所需量的纳米碳化硅颗粒、白砂糖粉、纳米二氧化硅粉和石墨粉混合后在高温加压条件下经过碳热还原反应,制备出以石墨和碳化硅复合相为基体,碳化硅纳米线为增强体的陶瓷基复合材料。
进一步说,上述采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,具体包括如下步骤:
步骤1,制备碳源:将所需量的白砂糖球磨后得到白砂糖浆料;白砂糖浆料经旋转蒸发、干燥、过筛处理后得到预用的碳源粉末;提供原位自生生长的SiCnw的碳源;
步骤2,将所需量的纳米碳化硅颗粒、石墨粉、纳米二氧化硅粉以及步骤1的白砂糖粉末混合得到混合物料,混合物料经球磨、干燥、过筛后得到混合粉末,有利于后期烧结试样的成分均匀;
步骤3,装模:将步骤2得到的混合粉末装入到石墨模具中;
步骤4,预压及烧结:将步骤3中石墨模具进行装炉,进行预压成型和高温高压烧结,得到碳化硅纳米线增强的石墨-碳化硅复合材料。
其中,步骤1中,将直径为6mm和3mm的氮化硅研磨球按质量比1∶1混合后再与白砂糖按球料体积比3∶1装入研磨罐中,采用此参数的磨球质量比和球料体积比,有利于球磨机的球磨产能达到较佳状态,并且可以达到良好的粉碎效果;用AR(分析纯)无水乙醇把球粉浸泡满,球磨12~24h,球磨罐的转速为200~300r/min,以达到最好的球磨效果。
其中,步骤1中,旋转蒸发过程为:将球磨后的白砂糖浆料装入蒸馏瓶中,旋转蒸发温度为60~70℃,转速为45~90r/min,真空度为30~100Pa,蒸发时间为看不到液滴滴到收集瓶为止。因为无水乙醇的沸点为78℃,通过加温加压可以达到球磨介质-无水乙醇的沸点,从而被蒸发;同时,因为直接干燥容易造成所加入的原料由于轻重问题而产生干燥过程中的“重者沉积”现象,通过旋转蒸发,可以保持原料一直处于均匀分布的状态。
其中,步骤2中,将直径为6mm和3mm的氮化硅研磨球按质量比1∶1混合后再与混合物料按球料体积比3∶1装入研磨罐中,球磨12~24h,球磨罐的转速为200~300r/min。按一定的直径和比例来安排磨球是为了达到最优的球磨产能效果;同时,采取上述的球磨时间和转速可以达到最好的球磨效果。
其中,步骤1和步骤2中,干燥温度为80~120℃,干燥时间为12~24h;过筛过程为:用孔径为0.075mm的筛网过筛200目。这个步骤的干燥在旋转蒸发之后,是由于旋转蒸发不能保证干燥彻底,因此加此步骤。过筛是为了细化颗粒直径,有利于烧结进行以及提高烧结的密度及强度。
其中,步骤3中,将一定质量的混合粉末装入石墨模具中,要保证粉体上面的平整,以免在热压烧结过程中由于粉体受力不均,造成施压过程中模具的断裂。
其中,步骤4中,预压步骤为:将装有混合粉末的石墨模具放入烧结炉腔体中央后,关上炉门抽真空;当真空度达到10Pa以下时,通入高纯氩气,当炉内Ar气压力达到大气压时,打开排气阀,保持炉内为流动Ar气气氛,作为保护气体,并保持炉内压力为大气压;预压压力为10~30MPa,保压时间0.5~3min。预压成型可以降低压缩率,减小压料腔体尺寸和空气含量,从而有利于传热和减少气泡量。
烧结步骤为:预压后,再以5~12℃/min的升温速率将温度升至1400~1600℃并保温0.5~4小时,在压力低的状态下达到此温度,是为了更有效地将腔体内的空气排出;再以2~5MPa/min的速率加压至10~50MPa,并以8~12℃/min的升温速率将温度升温至1700~1900℃,并保温保压0.5~4小时,在高温高压共同作用下,达到烧结致密化的作用;此后随炉降温到室温,并在开始降温的同时泄压,泄压速率为3~8MPa/min。
其中,制备得到的碳化硅纳米线增强石墨-碳化硅复合材料,其与以自身为摩擦副相互摩擦的常温摩擦系数为0.1~0.2,磨损率为10-7~10-6。其硬度为25~40GPa,抗弯强度为500~1200MPa,断裂韧性为6~10MPa·m1/2。
相比于现有技术,本发明技术方案具有的有益效果为:
本发明制备方法制得的复合材料利用原位自生技术,在复合粉体上直接生成弥散分布的碳化硅纳米线(SiCnw)增强体,生产成本低,比单一的SiC材料和石墨材料具有更优越的耐磨性能和力学性能;本发明制备方法制得的复合材料可用做自润滑材料,具有使用寿命长、耐磨损、硬度和强度高的优点。
本发明制备方法的原位自生法采用的原料为白砂糖、二氧化硅,原料来源广泛、价格低,工艺简单且价格低廉,并适合大规模工业化生产;相比于直接加入碳化硅纳米线进行热压烧结生成复合材料,原位生成是基于化学发应,所以生成物的尺寸更加细小、增强体分布更加均匀,有利于复合材料综合性能的提升。
附图说明
图1是本发明方法SiCnw增强(Gr/SiCp)复合材料的制备工艺流程图;
图2是原位自生生长合成的SiCnw的显微形貌图;
图3是本发明制得的SiCnw增强(Gr/SiCp)复合材料的显微形貌图。
具体实施方式
下面结合具体实施例来对本发明技术方案做进一步说明。
以下实施例均以碳化硅粉(纳米碳化硅颗粒)(SiCp)纯度大于98%,粒度小于10μm;纳米二氧化硅粉(Nano-SiO2)纯度大于98%,粒度小于50nm,非晶或者结晶态;市售白砂糖(C12H22O11)粉末;石墨粉(Graphite,Gr)纯度大于99%,粒度小于500nm为原料。
本发明SiCnw增强Gr/SiC复合材料的制备方法,其发明原理为:分别以C12H22O11和Nano-SiO2粉为原位合成的碳源和硅源,在高温加压条件下经过碳热还原反应,制备出SiCnw增强(Gr-SiCp)的陶瓷基复合材料。
此发生的化学方程式为:
C12H22O11(l)+4SiO2(s)=4SiCnw(s)+11H2O(l)+8CO(g)
在成分设计中,按照反应物进行了完全反应进行设计。本发明通过充分机械研磨来使粉体混合均匀,使各相均匀分布。复合材料的致密度通过阿基米德排水法测量得到;表面形貌通过扫描电子显微镜观察获得;摩擦系数和磨损率由摩擦磨损试验机测定;弯曲强度测试采用三点弯曲法;断裂韧性测试采用单边切口梁法。
实施例1
如图1所示,本发明采用原位自生法制备SiCnw增强(Gr-SiCp)复合材料的方法,包括如下步骤:
步骤1,将市售白砂糖(C12H22O11)在球磨机上用直径为3mm和6mm的氮化硅(Si3N4)混合研磨球进行球磨(直径为3mm和6mm的氮化硅研磨球的混合质量比为1∶1),其中球料的体积比为3∶1,球磨介质为AR无水乙醇;球磨24小时后,把C12H22O11粉体放入旋转蒸发器中,其中温度为60℃,真空度为70Mpa,转速为90r/min,蒸发球磨介质-无水乙醇液体。接着把粉体放在烘箱中于80℃下烘干,过筛200目,得到备用的C12H22O11粉末;C12H22O11粉末,其纯度大于95%,粒度小于2mm;
步骤2,将200目的C12H22O11粉末和纯度大于98%、粒度小于50nm、非晶或者结晶态的纳米二氧化硅(nano-SiO2)粉末按照质量百分比64wt%∶45wt%的比例加入(按照上述C12H22O11(l)+4SiO2(s)=4SiCnw(s)+11H2O(l)+8CO(g)的化学反应式,质量百分比64wt%∶45wt%的C12H22O11∶nano-SiO2,完全反应将原位生成30%wt的SiCnw增强体);外加质量百分比50%的纳米碳化硅颗粒(SiCp),纳米碳化硅颗粒纯度为98%、粒度小于10μm以及质量百分比20%的石墨粉(Graphite,Gr),石墨粉纯度为99%,粒度小于500nm,进行混合;磨球为d=6mm和3mm的Si3N4研磨球混合,磨球质量混合比例为1∶1,球料质量比为3∶1,装入研磨罐中,球磨时间为12h,球磨转速为300r/min,混合均匀后的粉体放入旋转蒸发器中,蒸发温度为60℃,转速为90r/min,真空度为70Pa,蒸发约40min;干燥温度为80℃,时间为12h;过筛200目,得到混合粉末;
步骤3,将混合粉末倒入到装有阴模的石墨模具中,整平粉末上表面后,合上阳模;
步骤4,将上述模具放入热压烧结炉腔中,通入氩气,保持炉内压力为大气压,加压到10MPa,预压成型;再以8℃/min的升温速率将温度升至1400℃并保温1h;在此阶段,以3MPa/min的速率加压至40MPa,并以10℃/min的升温速率升温至1900℃,保温、保压1h;最后以随炉冷却降至室温,得到SiCnw增强(Gr-SiCp)复合材料。
所得材料采用阿基米德法测量得到的致密度为95%;在400℃的高温摩擦条件中,保持0.15的摩擦系数,磨损率相对常规SiC陶瓷材料降低了78%;三点弯曲法测得弯曲强度为700MPa,单边切口梁法测得断裂韧性为6.8MPa·m1/2。
实施例2
如图1所示,本发明采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,包括如下步骤:
步骤1,同实施例1;
步骤2,各成分比例和热压烧结的温度相比实施例1中有所不同:200目的白砂糖(C12H22O11)粉末,纯度大于98%、粒度小于50nm、非晶或者结晶态的纳米二氧化硅粉末(nano-SiO2)按照质量百分比53.4wt%∶37.5wt%的比例(按照上述C12H22O11(l)+4SiO2(s)=4SiCnw(s)+11H2O(l)+8CO(g)的化学反应式,质量百分比53.4wt%∶37.5wt%的C12H22O11∶nano-SiO2,完全反应将原位生成25wt%的SiCnw增强体),外加纯度为98%、粒度小于10μm,质量分数为55%的SiCp和其纯度为98%、粒度小于10μm、质量分数为20%的石墨粉进行混合;磨球为d=6mm和3mm的Si3N4研磨球混合,磨球混合比例为1∶1,球料质量比为3∶1,装入研磨罐中,球磨时间为12h,球磨转速为300r/min,混合均匀后的粉体放入旋转蒸发器中,蒸发温度为70℃,转速为90r/min,真空度为80Pa,蒸发约30min;干燥温度为90℃,时间为12h;过筛200目,得到混合粉末;
步骤3,将混合粉末倒入到圆形的石墨模具中,整平粉末上表面后,合上阳模;
步骤4,将上述模具放入热压烧结炉腔中,通入保护气体氩气,保持炉内压力为大气压,加压到10MPa,保压2min,预压成型;再以12℃/min的升温速率将温度升至1000℃并保温1h;并以8℃/min的升温速率升温至1800℃,同时,在这个阶段中以3MPa/min的速率加压至30MPa,保温、保压1.5h;最后以随炉冷却降至室温,得到SiCnw增强(Gr-SiCp)复合材料。
将获得的复合材料进行致密度分析,发现致密度达到95%。SiCnw均匀分布在基体材料中。
所得复合材料采用阿基米德法测量得到的致密度为96%;在400℃的高温摩擦条件中,保持0.11的摩擦系数,磨损率相对SiC陶瓷材料降低了92%;三点弯曲法测得弯曲强度为830MPa,单边切口梁法测得断裂韧性为8.0MPa·m1/2。
如图2所示,本发明方法制得的SiCnw/(Gr-SiCp)复合材料中,原位自生合成的SiCnw,为纳米线形貌,长度分布在20~30μm,直径为20~60nm。如图3所示,本发明方法制得的SiCnw/(Gr-SiCp)复合材料中,在(Gr-SiCp)上直接生成弥散分布的碳化硅纳米线增强体;Graphite显示出鳞片层状结构,鳞片大小约为10μm,厚度约0.5μm;SiCp显示出等轴状形貌,平均粒径为0.5μm左右。
本发明SiCnw/(Gr-SiCp)复合材料可用于固体润滑剂,在高温和摩擦的作用下,在摩擦表面形成一层无定形的微米级和亚微米级SiO2薄膜(在高温和大气环境中,空气中的氧会参与进来,碳化硅将会被氧化成SiO2),起到自润滑作用,并且SiCnw增加了薄膜层的塑性变形能力,降低摩擦应力。复合材料在400℃的高温摩擦条件中,保持0.2以下的摩擦因数。复合材料的致密度达到95%以上(致密度和材料的孔隙率密切相关,是影响复合材料强度的一个重要因素);抗弯强度大于500MPa,比传统高强纯石墨材料和纯碳化硅材料抗弯强度至少提高了148%和19%;断裂韧性(由于碳化硅纳米线为纤维增韧相,并且均匀分布在基体材料中,在进行断裂韧性试验时,由于增韧相的交错分布,起到了显著的增韧效果)大于6MPa·m1/2,比纯SiC材料至少提高了80%。本发明制备出的复合材料明显提高了SiC材料的断裂韧性,并且生产成本低,合成工艺简单。
Claims (9)
1.一种采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:该方法为:将所需量的纳米碳化硅颗粒、白砂糖粉、纳米二氧化硅粉和石墨粉混合后在高温加压条件下经过碳热还原反应,制备出以石墨和碳化硅复合相为基体,碳化硅纳米线为增强体的陶瓷基复合材料。
2.根据权利要求1所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于,具体包括如下步骤:
步骤1,制备碳源:将所需量的白砂糖球磨后得到白砂糖浆料;白砂糖浆料浆料经旋转蒸发、干燥、过筛处理后得到白砂糖粉末;
步骤2,粉体混合:将所需量的纳米碳化硅颗粒、纳米二氧化硅粉、石墨粉以及步骤1的白砂糖粉末混合得到混合物料,混合物料经球磨、干燥、过筛后得到混合粉末;
步骤3,装模:将步骤2得到的混合粉末装入到石墨模具中;
步骤4,预压及烧结:将步骤3中石墨模具进行装炉,进行预压成型和高温高压烧结,得到碳化硅纳米线增强的石墨-碳化硅复合材料。
3.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤1中,将直径为6mm和3mm的氮化硅研磨球按质量比1∶1混合后再与白砂糖按球料体积比3∶1装入研磨罐中,用无水乙醇把球粉浸泡满,球磨12~24h,球磨罐的转速为200~300r/min。
4.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤1中,旋转蒸发过程为:将球磨后的白砂糖浆料装入蒸馏瓶中,旋转蒸发温度为60~70℃,转速为45~90r/min,真空度为30~100Pa,蒸发时间为看不到液滴滴到收集瓶为止。
5.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤2中,将直径为6mm和3mm的氮化硅研磨球按质量比1∶1混合后再与混合物料按球料体积比3∶1装入研磨罐中,球磨12~24h,球磨罐的转速为200~300r/min。
6.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤1和步骤2中,干燥温度为80~120℃,干燥时间为12~24h;过筛过程为:用孔径为0.075mm的筛网过筛200目。
7.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤3中,将一定量的混合粉末装入石墨模具中,并将粉体整平,合上阳模冲头。
8.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:步骤4中,预压步骤为:将装有混合粉末的石墨模具放入烧结炉腔体中央后,关上炉门抽真空;当真空度达到10Pa以下时,通入高纯氩气,当炉内Ar气压力达到大气压时,打开排气阀,保持炉内为流动Ar气气氛,并保持炉内压力为大气压;预压压力为10~30MPa,保压时间0.5~3min;
烧结步骤为:预压后,再以5~12℃/min的升温速率将温度升至1400~1600℃并保温0.5~4小时,接着再以2~5MPa/min的速率加压至10~50MPa,并以8~12℃/min的升温速率将温度升温至1700~1900℃,并保温保压0.5~4小时,此后随炉降温到室温,并在开始降温的同时泄压,泄压速率为3~8MPa/min。
9.根据权利要求2所述的采用原位自生法制备碳化硅纳米线增强石墨-碳化硅复合材料的方法,其特征在于:制备得到的碳化硅纳米线增强石墨-碳化硅复合材料,其与以自身为摩擦副相互摩擦的常温摩擦系数为0.1~0.2,磨损率为10-710-6;硬度为25~40GPa,抗弯强度为500~1200MPa,断裂韧性为6~10MPa·m1/2。
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