3D打印氧化硅陶瓷的制备及性能研究

随着陶瓷3D打印技术的发展,3D打印高性能陶瓷越来越受关注,在航空航天领域得到快速应用.通过研究分散剂、浆料pH、氧化硅粉体粒径和固相含量对浆料粘度和流动性的影响,可制备出粘度低、固相含量高、流动性好的陶瓷浆料.测试了不同固相含量对SiO2陶瓷的弯曲强度、烧成收缩率、气孔率和致密度的影响.结果表明:在68vol%的固相含量条件下,烧结后SiO2陶瓷的致密度达到74.32%,烧成收缩率为0.95%.     

浆料直写成形ZrO_2陶瓷制备及烧结

为浆料直写成形工艺制备了一种高固相含量的水基ZrO_2陶瓷浆料,并用该工艺打印陶瓷坯体,1350～1550℃烧结后制备ZrO_2陶瓷样品。研究烧结温度对样品收缩率、密度、气孔率、相结构、力学性能、微观形貌和表面质量的影响,并与其他制造工艺进行性能比较。结果表明:在1550℃烧结2 h,直写成形ZrO_2陶瓷综合性能最佳,其晶粒细小、显微结构均匀、致密性好,相对密度、抗弯强度、硬度和断裂韧性分别为99.2%、676MPa、12.5 GPa和6.2 MPa·m~(1/2)。在挤出增材制造工艺中,烧结样品具有高的致密度和优异的力学性能。     

一种新型的水系流延工艺制备中温SOFC电解质YSZ薄膜

采用-种新型的水系流延工艺制备中温SOFC电解质YSZ薄膜浆料.研究了同时添加粘结剂和分散剂的浆料的流变性,不同含量粘结剂对这种浆料粘度的影响,该工艺对流延片的干燥特性、生坯密度和坯片烧结性能的影响.实验结果表明:该浆料的假塑性程度和浆料的粘度随着B-1070的含量增加而减小;发现采用该工艺的干燥时间明显缩短;YSZ坯片的生坯密度大大提高,相对密度达到55.3%.所得流延素坯在1450℃保温2小时烧结能获得相对密度达98.5%的YSZ电解质薄膜.     

注浆成型B_4C/SiC复相陶瓷的工艺及性能研究

碳化硅陶瓷注浆成型工艺中浆料的分散稳定性和烧结工艺对碳化硅陶瓷的性能至关重要。采用真空无压烧结,以α-SiC超细粉为原料,B_4C为烧结助剂,研究分散剂、粘结剂、烧结助剂、烧结温度及保温时间等因素对浆料流动性、烧结特性与显微结构的影响规律。研究结果表明:在固含量为70%的SiC浆料中添加0.5 wt%TMAH和0.4 wt%PF,浆料的剪切粘度为184.75 m Pa·s,静置48 h没有明显沉降,符合注浆要求。在烧结温度为2000℃保温60 min的条件下,样品获得最佳烧结密度为2.719 g/cm~3。     

浆料直写成形Zr02陶瓷制备及烧结

为浆料直写成形工艺制备了一种高固相含量的水基Zr02陶瓷浆料,并用该工艺打印陶瓷坯体,1350～1550℃烧结后制备Zr02陶瓷样品.研究烧结温度对样品收缩率、密度、气孔率、相结构、力学性能、微观形貌和表面质量的影响,并与其他制造工艺进行性能比较.结果表明:在1550℃烧结2h,直写成形Zr02陶瓷综合性能最佳,其晶粒...     

聚合物模板法制备氧化铝-氧化锆泡沫陶瓷

将发泡聚苯乙烯小球(epispastic polystyrene,EPS)排列成有序的模板,通过离心成型技术制备孔壁致密、孔径均匀的Al2O3-ZrO2泡沫陶瓷.观察了EPS模板的可压缩特性,分析了浆料固相含量对离心成型过程中物质分离现象的影响,研究了不同烧结温度对Al2O3-ZrO2泡沫陶瓷的烧结密度、孔隙率和压缩强度的影响并表征了宏观孔结构和孔壁断面的微观结构.结果表明:用50%(体积分数)固相含量的浆料可制备出孔壁均匀的样品,在样品的不同部位,Al2O3和ZrO2的分布及相对含量基本相同,物质分离现象被很好的抑制.随着烧结温度的从1 450 ℃提高到1 600 ℃,Al2O3-ZrO2泡沫陶瓷的烧结密度增加、孔隙率降低.在1 550 ℃烧结2 h,样品的抗压强度可达2.07 MPa.     

Al2O3凝胶注模成型及添加TiO2烧结助剂的影响

采用有机单体丙烯酰胺与交联剂N, N?-亚甲基双丙烯酰胺发生凝胶作用,使Al2O3浆料凝胶成型. 对分散剂添加量、浆料的pH值和分散时间对陶瓷浆料粘度的影响、TiO2烧结助剂的加入对最终陶瓷烧结密度的影响和添加烧结助剂后高温烧结陶瓷表面形态的变化做了研究. 结果表明,添加TiO2 5%、在1300℃时的常压烧结密度可达到理论值的97%.     

A l2O3凝胶注模成型及添加T i O2烧结助剂的影响

采用有机单体丙烯酰胺与交联剂N, N-亚甲基双丙烯酰胺发生凝胶作用,使Al2O3浆料凝胶成型. 对分散剂添加量、浆料的pH值和分散时间对陶瓷浆料粘度的影响、TiO2烧结助剂的加入对最终陶瓷烧结密度的影响和添加烧结助剂后高温烧结陶瓷表面形态的变化做了研究. 结果表明,添加TiO2 5%、在1300oC时的常压烧结密度可达到理论值的97%.     

陶瓷部件的浆料打印快速成型

采用Sanders公司的四打印头快速成型机进行了陶瓷部件的浆料打印成型实验,实际测试了所用四打印头快速成型机的打印工作条件,考察了石蜡和挥发性介质两种浆料技术路线,并采用石蜡为介质制备了钛酸钡陶瓷浆料,研究了其流变性能,实验表明,虽然偶联剂的加入可以降低石蜡介质浆料的粘度,但是粘度足够低的可打印浆料的固相含量太低[约3％（in volume)以下],打印成型后不能完全烧结,因此,要通过打印成型出可完全烧结的陶瓷部件只能采用挥发液体作为浆料介质,以便在打印成型过程中通过介质挥发提高成型部件的固相含量。     

CaO-B2O3-SiO2玻璃陶瓷系生料带流延工艺研究

采用正交实验研究固含量、粘结剂和增塑剂对CBS(CaO-B2O3-SiO2)玻璃体系浆料粘度、生坯性能影响.利用STATISTICA 6.0分析表明:固含量、PVB和DBP的交互作用分别对浆料粘度和生料带的可揭膜程度影响最大,单因素及其交互作用对生坯密度均无显著影响.固含量50wt%.相对CBS玻璃粉料添加2wt%蓖麻油,7.5wt%PVB、4.5wt?P时,制备的浆料粘度为2.1 Pa.s.较适合流延,生坯体积密度达到1.6g.cm-3,且生料带较易从流延机上剥离.875℃低温烧结试样,在100Hz微波频率下测试,介电常数为6.56,介电损耗1.57×10-3.     

The Influence of Polyethylene Imine on the Gelcasting of SiC With Two Different Initiators

In the present work, polyethylene imine (PEI) is used as dispersant to prepare SiC slurry for aqueous gelcasting. When ammonium persulfate (APS) is used as initiator, PEI accelerates the polymerization of monomers and the solidification of gelcasting slurry at 25°C. The reason is that tertiary amine in the structure of PEI and APS form a redox system as initiator. SiC gelcating slurry with PEI and APS solidifies in 2 min at 25°C, which makes the operation of casting impossible. However, when another initiator, 2, 2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (AZIP·2HCl), is used, PEI does not accelerate but delays the polymerization of monomers because of the chain transfer. SiC gelcasting slurry in the presence of PEI and AZIP·2HCl has good fluidity and long idle time at 25°C. The slurry can be poured into the mold easily and solidifies in 5 min at 45°C. Therefore, PEI can be used as dispersant with the initiator of AZIP·2HCl in the gelcasting process, while PEI cannot act as dispersant when the initiator is APS.     

发泡浆体流变特性对轻质混凝土匀质性的影响

为改善轻质混凝土匀质性,提升轻质混凝土力学性能,本文通过建立Herschel-Bulkley(H-B)塑性黏度计算模型,探究了发泡浆体流变特性对泡沫沉降和浆体中陶粒分布的影响。结果表明：随增稠剂掺量的增加,轻质混凝土发泡浆体的屈服应力和基于非线性H-B模型η_H-B=0.016 67K(80ⁿ-20ⁿ)(η_H-B为H-B模型得出的发泡浆体塑性黏度;K为一致性系数;n为流动指数)得到的塑性黏度增大,导致发泡浆体沉降距下降,陶粒在浆体中的分形维数提高;当发泡浆体塑性黏度大于1.74 Pa·s、屈服应力大于92.87 Pa时,可制备抗压强度大于10 MPa的轻质混凝土。由此可见,优化发泡浆体流变特性是克服陶粒在发泡浆体中易上浮问题的关键,可有效改善轻质混凝土匀质性,提升轻质混凝土力学性能。     

不同粒径煤矸石浆液的流变性能试验

煤矸石浆液的流变性能影响注浆的可泵性,可通过调节粒径和水矸比对流变性能进行调控。本文测试了新鲜煤矸石浆液的流变性能、流动度及流动时间,研究了不同粒径(100目、150目、200目、250目、300目,分别对应150μm、106μm、74μm、58μm和48μm)及水矸比(1.0、1.5、2.0)对煤矸石浆液流变性能的影响,探讨了流变参数、流动度及流动时间的变化规律,并提出了注浆建议。结果表明：水矸比是煤矸石浆液流变性能的主控因素,煤矸石浆液在水矸比为1.0时,符合Herschel-Bulkley模型,颗粒粒径会影响浆液的屈服应力和塑性黏度,屈服应力为2.5～3.6 Pa;在水矸比为1.5、2.0时,符合Bingham模型,颗粒粒径只影响浆液的屈服应力,屈服应力为0.1～0.7 Pa。不同粒径煤矸石浆液的流动度均不低于365 mm,流动时间在27～31 s。为提高浆液的可泵性,可考虑采用较大的水矸比(≥1.5)和较长的搅拌时间(>800 s)。     

Lattice-structured SiC ceramics obtained via 3D printing,gel casting,and gaseous silicon infiltration sintering

In view of technical difficulties in preparing ceramics with complex shapes, gel casting combined with 3D printing was here adopted to prepare silicon carbide ceramic green body, and gaseous silicon infiltration sintering was used to prepare 3D lattice-structured ceramics. The preparation of the slurry, gel curing, and ceramic molding was investigated. Results demonstrate that the ratio of components affects the fluidity and stability of slurry. However, when volume fraction of the solid phase of the slurry reaches 56%, the viscosity of slurry is only 300 mPa s, and drying shrinkage rate of green body is 6.6%; these characteristics make slurry suitable for 3D complex model injection molding. Furthermore, both the temperature and the initiator affect gel curing speed. As the temperature and initiator content increase, the induction and gel time are rapidly shortened. When demolding at 300 °C and when gaseous silicon infiltration sintering is carried out at 1550 °C, a 3D lattice-structured ceramic with relative density of 87% and average compressive strength of 433 MPa can be obtained.     

生物质水煤浆流变特性研究

以福建无烟煤、水葫芦、添加剂等制备生物质水煤浆,研究了其流变特性。结果表明：添加3％～3．5％的水葫芦及1％的分散剂制得的生物质水煤浆粘度在0．8～1．2Pa·s之间,且稳定性较好。生物质含量提高,生物质水煤浆的粘度逐渐上升;分散剂含量为1％时,能够制得流变性较佳的生物质水煤浆;搅拌强度的增加能够使生物质水煤浆的粘度降低;当温度低于60℃时生物质水煤浆的粘度随温度升高而下降;当温度高于60℃时,生物质水煤浆的粘度随温度升高而上升。     

SiC浆料的流变性能研究

为制备结构均匀的多孔SiC陶瓷的料浆,本文比较了不同质量分数(40%~60%)的SiC浆料的剪切应力和黏度随剪切速率的变化.结果表明:浆料的等电点在3.6左右,Zeta电位值随着pH值的增加而减小,碱性环境下分散效果更好;用Casson方程拟合浆料的剪切应力,相关系数在0.98以上,随着固相含量的增加,拟合的极限粘度和屈服应力增加;当剪切速率达到100 s-1时,固相含量为40%~55%浆料的粘度都在1 Pa·s以下,固相含量为60% 的浆料粘度大概是2.1 Pa·s.     

再生微粉泡沫保温材料的制备及性能研究

采用湿泡沫拌合法以再生微粉(RP)为主要原料制备了泡沫保温材料,通过测量泡沫的稳定时间、浆体的流动特性与凝结过程,结合试件的抗压强度、干密度、孔隙率以及导热系数等指标,探讨了浆体组成对泡沫存活状态的影响规律以及RP的最大掺量。结果表明:泡沫的稳定性与浆体的黏度、凝结过程存在适宜的匹配状态,当水固比为0.80、浆体黏度为1.7 Pa·s左右、终凝时间小于30 min时,预制泡沫具有较好的存活状态;RP的最大掺量可达70%,所制备泡沫保温材料的抗压强度为1.15 MPa,导热系数为0.118 W/(m·K),符合JG/T 266—2011泡沫混凝土标准A06等级要求。     

原油流动性改进剂H89-2的制备及应用研究

含蜡原油流动性改进剂Ｈ８９－２系三元共聚物。以烯烃、烯烃基脂肪酸酯和烯属不饱和酰胺或烯属磺酸盐为主要原料，在含自由基引发剂的溶剂中，温度：５５～８５℃；压力：５～９ＭＰａ；时间：３～８ｈ共聚而成。综合评定表明：Ｈ８９－２对青海原油降凝、降粘、降屈服值效果显著，添加量１５０×１０－６，原油凝点从３１．５℃降至１２℃；表观粘度从５１５８．９ＭＰａ·ｓ降至７９．２ＭＰａ·ｓ；屈服值从７３．６Ｐａ降至０Ｐａ。     

Preparation of alumina by aqueous gelcasting

The alumina ceramic was prepared by aqueous gelcasting. The effects of zeta potentials, solid loading, dispersant content and milling time on the alumina suspension were studied systematically. The dispersant content has remarkable effects on the viscosity of the suspension. The appropriate dispersant concentration for alumina aqueous slurry with the solid loading of 55 vol.% is 0.6 wt.%. It can be seen that all suspensions (50–56 vol.% solid loading) exhibited a shear-thinning behavior and relatively low viscosity, which was suitable for casting. The degree of shear thinning and the viscosity at high shear rates increased with increasing volume fraction of solid. As the milling time prolongs, viscosity of the suspension decreases first, then the plateau appears and the average diameter keeps changeless. When the milling time was shorter than 20 h, the viscosity of slurries decreased gradually as the time of milling increased. After 20 h milling, the viscosity of the slurry tended to be consistent. Therefore, the ball milling time should be equal to or more than 20 h to obtain a stable suspension at equilibrium. The time available for casting the slurry (idle time) can be controlled by the amounts of initiator and catalyst added to the slurry as well as by the processing temperature. Micrograph of the gelcast green body was homogeneous.     

Rheology of simulated radioactive waste slurry and cold cap during vitrification

During the vitrification of radioactive waste in a Joule‐heated melter, aqueous melter feed slurry forms a cold cap, a reacting and melting material, which floats on the surface of the molten glass. The rheological behavior of the feed affects cold cap formation and shape, and is vital for modeling the feed‐to‐melt conversion process. We used slurry feed simulant and fast‐dried slurry solids representing the cold cap to investigate the rheological behavior of the feed as it transforms into glass. Both low‐temperature and high‐temperature rheometry were performed and a new scheme was applied to estimate the feed viscosity. This study shows that the conversion advances in four sequential stages that form distinct regions in the cold cap: (i) a fast‐spreading boiling slurry from which water evaporates, (ii) a porous solid region (viscosity > 10⁸ Pa s) containing reacting solids and molten salts, (iii) a plastic region in which glass‐forming melt connects the refractory solids (~10⁸ to ~10⁶ Pa s), and (iv) a viscous foam layer in which the viscosity drops from ~10⁵ to ~10¹ Pa s. The implications for the mathematical modeling of the cold cap are discussed.