Si对碳化硅纤维烧结性能的影响

本文以Ｓｉ元素为烧结助剂,成功地实现了ＳｉＣ陶瓷纤维的液相烧结,并对纤维烧结体的力学性能及显微结构进行了分析。实验结果表明,由于Ｓｉ元素的存在,在烧结过程中Ｓｉ转变为液相,使碳化硅纤维的烧结温度降为１８００℃,纤维的抗拉强度达到６００ＭＰａ;Ｓｉ的加入量最佳值是１０％,而大于或小于该值时,纤维的抗拉强度均低于６００ＭＰａ。     

氧化铝、碳化硅陶瓷纤维的成型与烧结

本文以纳米级氧化铝和碳化硅微粉为原料 ,采用挤压烧结工艺 ,成功地制备出氧化铝和碳化硅陶瓷纤维。对纤维的烧结特性进行了分析 ,测试了纤维的拉伸强度 ,用SEM观察了纤维断口形貌。结果表明 :由于采用纳米微粉为原料 ,使陶瓷纤维的烧结温度降低 ,氧化铝纤维在 1 2 0 0℃烧结后 ,相对密度达到 99 5 % ,拉伸强度为 840Mpa ;碳化硅纤维 1 80 0℃烧结后 ,密度高于 95 % ,拉伸强度为72 0MPa。     

Sialon陶瓷的常压烧结

在Si3N4,Al2O3,AIN和Y2O3混合料常压烧结过程中,由于过程反应生成SiO,CO,N2等气相物质和由于Si3N4原料在高温常压下分解压高,从而常压烧结致密化过程始终伴随着一个失重的塑致密化过程。为了解决这一问题,作者研究了填料成分、烧结温度、烧结时间等工艺条件对Sialon陶瓷常压烧结密度的影响,分析了烧结过程的物理化学机制和致密化机制。4种填料分别为Si3N4,Si3N4 SiO2,Si3N4 Al2O3 AIN和Si3N4 Al2O3 AIN BN。被烧料典型配方为：Si3N465%-70%,Al2O320%-25%,AIN10%,另加6％Y2O3。当填料成分为70％Si3N4 24%Al2O3 3%AIN 3%BN时,制得了相对密度达99％,抗弯强度达612．2MPa的常压烧结Sialon陶瓷。研究结果表明：对于通式为Si6-zAlzOzN8-z的Sialon陶瓷,当Z＝2时,其最佳烧结温度为1750℃,烧结时间为40min;Sialon的烧结过程是1个多因素控制的瞬时液相烧结过程。     

超声处理对Mg-9Al-xSi(x=1,6)合金不同形貌Mg_2Si相形成机制的影响

为了探讨超声处理对不同形貌Mg_2Si相形成机制的影响,本文采用超声辅助原位自生的方法成功制备了以Mg_2Si为增强相的镁合金材料。利用XRD、OM、SEM等分析测试手段,研究了超声处理对Mg_2Si微观形貌、大小及分布的影响。结果表明:经超声处理后,Mg-9Al-1Si合金中共晶Mg_2Si相由粗大汉字状变成短棒状、条状,团聚现象得到改善,分布更加均匀,使其抗拉强度和伸长率显著提高,分别由93 MPa和4.9%提升到172 MPa和12.3%;Mg-9Al-6Si合金中初生Mg_2Si相大量减少,由粗大多角状变成小块状或颗粒状,且内部无空洞、棱角趋于圆化,汉字状Mg_2Si相大量增加,使其抗拉强度和伸长率分别达到108 MPa和3.2%。这主要由于声空化产生的瞬态高温、高压及声流效应对合金液中元素及温度分布产生影响,使得凝固过程改变所致。     

放电等离子烧结含铝Ti_3SiC_2相的形成规律研究

用放电等离子烧结工艺以元素粉为原料制备 Ti3Si C2 材料时 ,掺入适量铝能改善 Ti3Si C2 的反应合成。应用 X-射线衍射和扫描电子显微镜研究不同烧结温度下材料的相组成和显微结构特征。结果表明 :含铝 Ti3Si C2 相在 110 0℃开始大量形成 ,经 115 0～ 12 5 0℃烧结 ,能制备纯净致密含铝 Ti3Si C2 固溶体材料。铝的固溶降低了 Ti3Si C2 的化学热稳定性 ,使其分解温度降低至 130 0℃。     

以单质Si、C原料制备反应烧结碳化硅的研究

以 C- Si坯体融渗 Si的方法制备反应烧结碳化硅 ,研究了坯体中 Si含量对素坯结构、物相组成以及材料性能的影响。 C转化为 Si C时的体积效应是引起坯体毛细管阻塞的主要原因。 Si粉的掺入提供了精细地调整坯体结构的手段 ,使 Si C的转化率得以提高。烧结过程研究表明 ,预掺 Si使部分 Si C的合成反应提前进行 ,反应发热得以减缓。当调整坯体中 C含量为 0 .84 g/ cm3时 ,制得了密度与断裂强度分别为 3.0 9g· cm- 3和 5 5 0± 2 5 MPa的反应烧结碳化硅材料     

LaB6多晶材料的制备工艺研究

利用真空热压烧结技术在真空热压烧结炉中制备了LaB6 多晶材料 .测试了采用不同烧结工艺制备的LaB6 多晶的性能 ,研究了烧结温度、压力和保温时间对多晶体致密度和弯曲强度的影响 ,从而确定了最佳的烧结工艺参数为烧结温度 2 10 0℃ ,压力 5 0MPa ,保温时间 2h .这一工艺条件下制备的LaB6 多晶致密度达 92 % ,弯曲强度达 110MPa .     

氮化硅-氧化镁-氧化钇陶瓷的常压烧结

采用常压烧结工艺制备了Si3N4-MgO-Y2O3陶瓷材料,克服了热压工艺的缺陷。Y2O3的添加量对烧结陶瓷材料的致密化行为和机械性能有很大的影响。常压烧结Si3N4-MgO-Y2O3陶瓷材料,当氧化钇含量(质量分数)为4%~5%时,相对密度达99%,抗弯强度达950 MPa,断裂韧性7.5 MPa.m1/2。     

Ca对Mg-6Al-1Nd合金显微组织和性能的影响

为了研究Ca元素对Mg-6Al-1Nd合金微观组织、力学性能和阻燃性能的影响规律,采用了金属型重力铸造方法制备了Mg-6Al-1Nd-x Ca合金.通过金相显微镜、扫描电镜、万能拉伸试验机和热分析仪等分析测试手段对Mg-6Al-1Nd-x Ca合金的显微组织、力学性能和阻燃性能进行了表征.结果表明:Ca元素的加入可减少β-Mg17Al12含量,生成Al-Ca金属间相;随着Ca质量分数的增加,镁合金试样中的Al-Ca金属相增多,试样的室温抗拉强度和延伸率降低,阻燃性能升高;不含Ca元素的Mg-6Al-1Nd合金的抗拉强度为235 MPa,当Ca元素增加到2.5%时,Mg-6Al-1Nd-2.5Ca合金的抗拉强度仅为154 MPa,但该合金的着火点可达850℃.     

Fe-Ni-Cu-C合金粗粉注射成形件的力学性能和微观组织

对平均粒度为60μm的Fe-Ni-Cu-C合金粗粉进行了注射成形。分析了烧结温度、保温时间和烧结气氛对烧结件力学性能和微观组织的影响。结果表明,在1 225℃,保温1 h,H2和N2(体积分数)比为1∶3时得到的烧结件具有最好的力学性能,其抗拉强度为360 MPa,屈服强度为171MPa,硬度为54 HRB。     

碳化硅-二硼化钛复合陶瓷性能研究

采用无压烧结,利用小分子的B、C作为烧结助剂在2180℃获得了相对密度为96％的SiC—TiB2复合材料,XRD分析显示在烧结过程中无新相产生,从烧结体的显微形貌可以看出,在烧结过程中有包晶现象,SiC颗粒有明显长大趋势．大的晶粒存在使烧结体的力学性能降低,主要表现为抗弯强度和断裂韧性不高,分别只有158．6MPa和2．85MPa·m^1/2．     

THE CHARACTERISTICS OF THE PRESSURELESS SINTERED Si_3N_4-MgO-Ce0_2 CERAMICS

An investigation of the pressureless sintering of Si3N4 with MgO-CeO2 revealed that MgO-CeO2 is a most effective sintering aid for silicon nitride. The amount of MgO-CeO2 and sintering conditions have a strong influence on the densification behaviour and mechanical properties of the sintered materials. The effect of the additive and sintering conditions are discussed. The silicon nitride pressureless sintered with MgO-CeO2 retained a relative density of 98. 5% and a bending strength of 950 MPa. The Si Mg-Ce-O-N system is of great value for application and theoretical study.     

Effects of sintering atmosphere on the microstructure and mechanical property of sintered 316L stainless steel

1　ＩＮＴＲＯＤＵＣＴＩＯＮＰｒｅｓｓ/ｓｉｎｔｅｒ (Ｐ/Ｍ )ｉｓａｃｏｍｍｏｎｌｙｕｓｅｄｔｅｃｈｎｏｌｏｇｙｆｏｒｆａｂｒｉｃａｔｉｏｎｏｆｐｏｗｄｅｒｍｅｔａｌｌｕｒｇｙ31 6Ｌｓｔａｉｎｌｅｓｓｓｔｅｅｌ.Ｙｅｔ,ｔｈｅａｓ ｓｉｎｔｅｒｅｄｄｅｎ ｓｉｔｙｉｓａｂｏｕｔ 90 %ｏｆｔｈｅｏｒｅｔｉｃａｌｄｅｎｓｉｔｙｗｉｔｈｌｏｗｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓ.ＳｏｍｅｒｅｓｅａｒｃｈｅｒｓｓｔｕｄｉｅｄａｄｄｉｎｇｅｌｅｍｅｎｔｓｌｉｋｅＢ ,Ｐ ,Ｓｉ,Ｃｕ ,Ａｌ,ｅｔｃ .ｔｏｆｏｒｍｌｏ…     

THE ROLE OF MgO-CeO_2 IN THE DENSIFICATION OF Si_3N_4

An investigation of the pressureless sinteringof Si_3N_4 with MgO-CeO_2 reveals that Mgo-CeO_2 is a muchmore effective sintering aid for silicon nitride than eitherMgO or CeO_2.The amount of MgO-CeO_2 and MgO/CeO_2weight ratio has a strong influence on the densification be-haviour and mechanical properties of the sintered materials.The Silicon nitride pressureless sintered with MgO-CeO_2 re-tains a relative density of 98.5%,a bending strength of 950MPa.The Si-Mg-Ce-O-N system is of great value for appli-cation and theoretical study.     

添加氧化钙的硅酸锆陶瓷的性能

以硅酸锆和硝酸钙为原料,采用湿磨的方法实现原料的均匀混合,制备了系列的添加氧化钙的硅酸锆陶瓷,利用阿基米德法和X-射线衍射技术对硅酸锆陶瓷的密度、物相变化进行了表征,测试了其显微结构和抗折强度,重点讨论氧化钙添加量和烧成温度对硅酸锆陶瓷的影响.结果表明,1 450℃和1 500℃烧结试样的体积密度随氧化钙添加量改变有较小变化,1 550℃烧结试样密度则随着氧化钙添加量增大而减小,密度最大值可达4.19克/立方厘米;样品的物相由硅酸锆和单斜氧化锆及少量稳定氧化锆组成,主晶相为硅酸锆;硅酸锆陶瓷有较多的气孔,是其致密度小的主要原因,硅酸锆陶瓷的主要断裂方式是沿晶断裂;硅酸锆陶瓷的抗折强度随着烧成温度的升高明显降低,随氧化钙添加量增大而先减小再增大,抗折强度最高可达186.0兆帕.     

Microstructures and properties of WC-20Co-1Y_2O_3 cemented carbide by hot-press and liquid phase sintering

1　INTRODUCTIONInRef .[1],averyinterestingandinexplicablefindingwasreportedthataspecialwhisker likeWCgrainstructure ,mostintherangeof 10 0 2 0 0nmindiameterand 1 2mminlength ,wasformedinWC 2 0Co 1Y2 O3cementedcarbidepreparedbyhot pressbelowtheeutectictemperature .ItwasmentionedinthepaperthatWCpowderwithFisherSubsiereSizer(FSSS)of 1μm ,ultrafineCopowder ,andY2 O3powderof 1μmwereusedastherawmaterialsofWC 8Cocementedcarbide .However ,whetherthesamerawmaterialswereusedinWC 2 0Co …     

基于普通纸张的蜂窝陶瓷载体材料的设计与性能研究

以普通纸张为原料,采用凝胶-溶胶技术对纸张进行处理,并通过折叠、粘贴等仿生设计,经低温炭化、高温碳热还原反应及气相渗硅等方式制备出SiC/Si蜂窝陶瓷载体复合材料.采用XRD、SEM、TEM和三点弯曲等分析测试手段对其相组成、微观结构和力学性能进行分析.结果表明,陶瓷纸炭化以后为非晶态的碳;经真空炉烧结后的相组成为β-SiC相、Si相和残留的C相.三点弯曲实验表明,SiC/Si陶瓷复合材料的强度超过200MPa.多孔碳化硅的气孔率随着排硅时间的增加而增加,其强度和韧性随着排硅时间的增加而减小.     

Shape memory effect during preparation of alumia ceramic tubes

Pure alumina ceramic tube and 95 alumina ceramic(the ceramic with 95.84% alumina) tube were prepared by using self-prepared alumina micrometer powder without agglomeration as raw material. The ceramic green was shaped by isostatic pressing and sintered at different temperature from 800 to 1 600 ℃ for 2 h. The 95 ceramic tube sintered at 1 550 ℃ for 2 h had mean particle size of 4 μm, bend strength of 437 MPa and volume density of 3.714 g/cm3. Shape memory effect during sintering was observed. XRD results showed that no phase transition occurred during shape memory process, which indicated that shape memory effect was not caused by phase transition. Several probable causes of the alumina ceramic shape memory effect were discussed in this paper.     

Synthesis and Sintering of Mg2Si Thermoelectric Generator by Spark Plasma Sintering

Raw Mg,Si powder were used to fabricate Mg2Si bulk thermoelectric generator by spark plasma sintering (SPS).The optimum parameters to synthesize pure Mg2Si powder were found to be 823 K,0 MPa,10 min with excessive content of 10wt% Mg from the stoichiometric Mg2Si.Mg2Si bulk was synthesized and densified simultaneously at low temperature (823 K) and high pressure (higher than 100 MPa) from the raw powder,but Mg,Si could not react completely,and the sample was not very dense with some microcracks on the surface.Then,Mg,Si powder reacted at 823 K,0 MPa,10 min in SPS chamber to form Mg2Si green compact,again sintered by SPS at 1023 K,20 MPa,5 min.The fabricated sample only contained MgESi phase with fully relative density.     

Comparative study of β-Si3N4 powders prepared by SHS sintered by spark plasma sintering and hot pressing

β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200℃ lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa.m1/2.