本文選題：碳化硅 + 大尺寸�。� 參考：《北京科技大學(xué)》2015年博士論文

【摘要】：大尺寸碳化硅結(jié)構(gòu)陶瓷件在許多特殊工況及部位具有迫切的應(yīng)用需求。本文結(jié)合行業(yè)需求,選取耐腐蝕、耐磨損特種離心泵用大尺寸、復(fù)雜形狀碳化硅陶瓷葉輪作為對(duì)象展開(kāi)研究工作。論文的主要內(nèi)容包括以下幾個(gè)方面： 將造粒技術(shù)引入到凝膠注模成型技術(shù)中,通過(guò)噴霧造粒和壓塊造粒使初始亞微米級(jí)碳化硅粉末平均粒徑由0.51μ m粗化至40μ m和8.2μ m,顯著降低了陶瓷漿料的粘度。由噴霧造粒和壓塊造粒配制的陶瓷漿料(50vo1%,剪切速率為100s-1)粘度分別為未造粒粉末漿料的1/2.5和1/3.5。壓塊造粒粉末配制的漿料粘度比噴霧造粒粉末漿料低58mPa·s。噴霧造粒和壓塊造粒粉末制備的凝膠注模生坯彎曲強(qiáng)度分別達(dá)到未造粒粉末生坯的3倍和3.5倍。存在于生坯和漿料中的造粒粉末團(tuán)粒在燒結(jié)過(guò)程中徹底消失,兩種造粒粉末制備的燒結(jié)樣品彎曲強(qiáng)度達(dá)到了相同的水平,均為未造粒級(jí)粉末燒結(jié)樣品的2.2倍。 采用凝膠注模工藝制備了短切碳纖維增強(qiáng)增韌的固相燒結(jié)碳化硅復(fù)合陶瓷材料(Csf/SiC)。隨著Csf添加量的增加,凝膠注模漿料的粘度單調(diào)增高；彎曲強(qiáng)度和斷裂韌性均為先增高后降低,當(dāng)5wt%Csf時(shí)彎曲強(qiáng)度達(dá)到最大值420MPa,比純碳化硅材料彎曲強(qiáng)度提高80MPa,比模壓成型復(fù)合材料彎曲強(qiáng)度最大值高30MPa；而斷裂韌性在7.5wt.%Csf時(shí)達(dá)到最大值4.61MPa·m1/2,比純碳化硅材料斷裂韌性提高0.88MPa·m1/2,比模壓成型復(fù)合材料斷裂韌性局0.4MPa·m1/2,主要增韌增強(qiáng)機(jī)制為纖維拔出和纖維斷裂,其中凝膠注模中的有機(jī)物裂解產(chǎn)生的裂解碳包裹在碳纖維表面,對(duì)纖維增強(qiáng)增韌效果具有促進(jìn)作用。 采用凝膠注模成型大尺寸、復(fù)雜形狀碳化硅陶瓷葉輪,利用造粒技術(shù)粗化初始粉末,顯著降低了漿料的粘度,經(jīng)葉輪結(jié)構(gòu)特征優(yōu)化和模具設(shè)計(jì),控溫控濕干燥及濕坯受力狀態(tài)平衡控制,抑制了干燥裂紋的產(chǎn)生；經(jīng)燒結(jié)支撐設(shè)計(jì)和溫度場(chǎng)控制,克服燒結(jié)變形問(wèn)題,最終制備出復(fù)雜形狀陶瓷葉輪樣品(160mm),材料相對(duì)密度達(dá)96%,密度偏差0.5%,彎曲強(qiáng)度為420MPa。用戶耐磨損性能臺(tái)架對(duì)比試驗(yàn)表明,本文研制的陶瓷葉輪磨損率僅為廠家主導(dǎo)產(chǎn)品超高分子量聚乙烯葉輪的1/l0。目前尚未見(jiàn)到該類大尺寸固相燒結(jié)體系碳化硅陶瓷葉輪產(chǎn)品及制備技術(shù)的相關(guān)報(bào)道。
[Abstract]:Large-size silicon carbide structure ceramic parts have urgent application needs in many special working conditions and parts.In this paper, the large size and complex shape of silicon carbide ceramic impeller for special centrifugal pump with corrosion resistance and wear resistance is selected as the research object.The main contents of the thesis include the following aspects:The granulation technology was introduced into the gel injection molding technology. The average particle size of the initial submicron silicon carbide powder was coarsened from 0.51 渭 m to 40 渭 m and 8.2 渭 m by spray granulation and pressing granulation, which significantly reduced the viscosity of the ceramic slurry.The viscosity of ceramic slurry prepared by spray granulation and press granulation is 1 / 2.5 and 1 / 3.5of that of ungranulated powder size, respectively, with shear rate of 100s-1.The viscosity of the slurry prepared by pressing granulated powder is lower than that of spray granulated powder size, 58mPa s.The bending strength of the gel injection mould blank prepared by spray granulation and pressing granulation powder is 3 and 3.5 times of that of the ungranulated powder blank, respectively.The sintering strength of the sintered samples prepared by the two kinds of granulated powders has reached the same level, and the bending strength of the sintered samples is 2.2 times of that of the ungranulated powder sintered samples.The short cut carbon fiber reinforced and toughened solid phase sintered silicon carbide composite ceramic material was prepared by gel casting process.With the increase of Csf content, the viscosity of gel casting paste increases monotonously, and the bending strength and fracture toughness increase first and then decrease.The maximum bending strength of 5wt%Csf is 420 MPA, which is 80 MPA higher than that of pure silicon carbide, and 30 MPa higher than the maximum bending strength of molded composites, while the fracture toughness of 7.5wt.%Csf reaches the maximum value of 4.61MPa M1 / 2, which is higher than that of pure silicon carbide.To improve the fracture toughness of 0.88MPa M1 / 2, compared with 0.4MPa M1 / 2, the main toughening and reinforcing mechanisms are fiber pull-out and fiber fracture.The pyrolytic carbon produced by the organic cracking in the gel casting mold is wrapped on the surface of carbon fiber, which can promote the reinforcing and toughening effect of the fiber.The large size and complex shape silicon carbide ceramic impeller was molded by gel injection, and the initial powder was coarsened by granulating technology. The viscosity of the slurry was significantly reduced, and the impeller structure was optimized and die design was carried out.Temperature-controlled wet drying and force balance control of wet billet can restrain the production of drying crack and overcome the problem of sintering deformation through sintering support design and temperature field control.Finally, the ceramic impeller sample with complex shape was prepared. The relative density of the material was 96, the density deviation was 0.5 and the bending strength was 420 MPA.The wear resistance of the ceramic impeller developed in this paper is only 1 / 10 of that of the UHMWPE impeller produced by the manufacturer.At present, there are no reports on the product and preparation technology of silicon carbide ceramic impeller for this kind of large scale solid-phase sintering system.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ174.7

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