SiC陶瓷的低溫?zé)Y(jié)及其結(jié)構(gòu)與性能
發(fā)布時(shí)間：2018-10-30 14:18
【摘要】：SiC陶瓷具有硬度大、強(qiáng)度高、熱膨脹系數(shù)低、耐磨損、抗腐蝕等優(yōu)異性能,作為機(jī)械密封件及耐磨、耐腐蝕件的應(yīng)用前景廣闊。本文開發(fā)一種無保護(hù)氣氛下的SiC陶瓷低溫常壓燒結(jié)新技術(shù),采用原料顆粒級配、燒結(jié)助劑類型及含量、粘結(jié)劑選擇與含量、壓制壓力、燒結(jié)工藝(燒結(jié)溫度、保溫時(shí)間)等的優(yōu)化設(shè)計(jì),低溫?zé)Y(jié)制備力學(xué)性能優(yōu)良的SiC陶瓷材料,并對其結(jié)構(gòu)與性能的關(guān)系開展研究。相比于CaO-Al2O3-Y2O3和BaO-Al2O3-CaO而言,BaO-Al2O3-Y2O3體系助燒效果更佳。在無保護(hù)氣氛下燒結(jié),該燒結(jié)助劑與SiC粉體表面氧化形成Si02反應(yīng)形成粘度適中且與SiC顆粒表面潤濕性良好的助燒熔體,借助于液相粘性壓緊效應(yīng)和液相快速傳質(zhì),促進(jìn)SiC陶瓷內(nèi)的物質(zhì)傳輸,加速致密化。該助燒熔體在SiC陶瓷燒結(jié)后的冷卻過程中大多以鋇長石晶體(BAS)的形式析出,同時(shí),還析出Y2Si2O7、CaAl2Si2O8等氧化物第二相,有效避免了形成脆性玻璃相對SiC陶瓷結(jié)構(gòu)與性能的不利影響。燒結(jié)SiC陶瓷中SiC顆粒與第二相結(jié)合緊密,SiC相斷口較為平整,呈現(xiàn)主體解理斷裂特征,第二相斷口粗糙,增大了斷裂裂紋擴(kuò)展的路徑,有利于提高SiC陶瓷材料的韌性。采用3.5μm和0.5μm兩種粒徑的SiC粉體,按3：1的重量比級配,添加5 wt%的石蠟粘結(jié)劑,在400 MPa的壓制壓力下壓制的陶瓷素坯致密度最大(2.00g/cm3)。添加含量為30 wt%的BaO-Al2O3-Y2O3燒結(jié)助劑,采用獨(dú)特的埋粉工藝,于1550℃保溫30 min燒結(jié)制備的SiC陶瓷的性能最佳,其密度、抗彎強(qiáng)度和斷裂韌性分別達(dá)到3.14g/cm3、520 MPa和6.7 MPa·m1/2。
[Abstract]:SiC ceramics have excellent properties such as high hardness, high strength, low coefficient of thermal expansion, wear resistance, corrosion resistance and so on. In this paper, a new low temperature and atmospheric pressure sintering technology for SiC ceramics in unprotected atmosphere is developed. The raw material particle gradation, sintering assistant type and content, binder selection and content, pressing pressure, sintering process (sintering temperature, etc. The optimum design of holding time etc., the preparation of SiC ceramics with excellent mechanical properties by low temperature sintering, and the study on the relationship between structure and properties were carried out. Compared with CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO, the effect of BaO-Al2O3-Y2O3 system is better than that of CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO. When sintered in unprotected atmosphere, the sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. The sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. Promote material transport in SiC ceramics and accelerate densification. During the cooling process of SiC ceramics, most of these melts are precipitated in the form of barium feldspar crystal (BAS), and the second phase of oxides such as Y _ 2Si _ 2O _ 7 and CaAl _ 2Si _ 2O _ 8 are also precipitated. The unfavorable effect of brittle glass formation on the structure and properties of SiC ceramics was effectively avoided. The SiC particles in the sintered SiC ceramics are closely combined with the second phase, and the SiC phase fracture surface is relatively flat, showing the main cleavage fracture characteristics. The second phase fracture surface is rough, which increases the path of fracture crack propagation, and is conducive to improving the toughness of SiC ceramics. Two kinds of SiC powders, 3.5 渭 m and 0.5 渭 m, were prepared by 3:1 gradation, and 5 wt% paraffin binder was added. The maximum density (2.00g/cm3) of the ceramic blank was obtained under the pressure of 400 MPa. The properties and density of the SiC ceramics sintered at 1550 鈩，
本文編號：2300242
[Abstract]:SiC ceramics have excellent properties such as high hardness, high strength, low coefficient of thermal expansion, wear resistance, corrosion resistance and so on. In this paper, a new low temperature and atmospheric pressure sintering technology for SiC ceramics in unprotected atmosphere is developed. The raw material particle gradation, sintering assistant type and content, binder selection and content, pressing pressure, sintering process (sintering temperature, etc. The optimum design of holding time etc., the preparation of SiC ceramics with excellent mechanical properties by low temperature sintering, and the study on the relationship between structure and properties were carried out. Compared with CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO, the effect of BaO-Al2O3-Y2O3 system is better than that of CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO. When sintered in unprotected atmosphere, the sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. The sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. Promote material transport in SiC ceramics and accelerate densification. During the cooling process of SiC ceramics, most of these melts are precipitated in the form of barium feldspar crystal (BAS), and the second phase of oxides such as Y _ 2Si _ 2O _ 7 and CaAl _ 2Si _ 2O _ 8 are also precipitated. The unfavorable effect of brittle glass formation on the structure and properties of SiC ceramics was effectively avoided. The SiC particles in the sintered SiC ceramics are closely combined with the second phase, and the SiC phase fracture surface is relatively flat, showing the main cleavage fracture characteristics. The second phase fracture surface is rough, which increases the path of fracture crack propagation, and is conducive to improving the toughness of SiC ceramics. Two kinds of SiC powders, 3.5 渭 m and 0.5 渭 m, were prepared by 3:1 gradation, and 5 wt% paraffin binder was added. The maximum density (2.00g/cm3) of the ceramic blank was obtained under the pressure of 400 MPa. The properties and density of the SiC ceramics sintered at 1550 鈩，
本文編號：2300242
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