若干成纤工艺条件对氧化锆纤维坯体性能的影响

以氧氯化锆为主要原料,以氧化钇为相稳定剂,以醋酸和柠檬酸为有机助剂,采用溶胶凝胶法制备多晶氧化锆纤维。研究胶体黏度、氧化锆含量和甩丝盘转速对纤维坯体性能的影响。试验发现:当溶胶内氧化锆质量分数为27.62%左右、黏度为27 P左右时,制得的纤维坯体直径细且分布均匀;随着胶体黏度的上升,纤维的平均直径呈上升趋势;甩丝盘转速在4 000~5 500 r/min时,成纤性相对较好,且纤维的平均直径随着转速的增加而略有下降,而直径分布变化不明显。     

溶胶—凝胶法微晶氧化锆纤维的研究

溶胶—凝胶法制备氧化锆纤维其结构的均与微晶化对使用性能至为重要,近年来,对此研究报道较多。通常以Y_2O_3为稳定剂的Y-PSZ纤维经过一定热处理过程可获得≤0.5 μm晶粒度的微晶结构。 采用溶胶—凝胶法制备氧化锆陶瓷材料,当进行热处理时锆质凝胶无机高分子转化成的无定形ZrO2将逐步晶化。本文对3.6 mol％Y_2O_3-ZrO_2纤维的制备及热处理中晶化现象进行了研究,并初步探讨了晶核剂的加入对晶化的影响。所制Y-PSZ纤维直径5～1μm,1400 ℃处理2h后,晶相为t-ZrO_2。和极少量m-ZrO2,晶粒度均小于0.1 μm。     

不锈钢纤维长度对不锈钢纤维毡均匀度的影响

不锈钢纤维毡是否均匀主要取决于毡中纤维束及断丝的百分率。采用丝径分别为Φ８μｍ,Φ１２μｍ,Φ２０μｍ的不锈钢纤维为原料,经剪切,开松,铺毡,然后取样检测毡样中的纤维束及断丝百分率。发现铺毡纤维束百分率随长度的缩短而减少,但断丝的百分率则增加,只有当纤维的长度适当时铺出的毡均匀,不同直径的纤维对应不同的最佳纤维长度。     

溶胶－凝胶法制备钇铝石榴石纤维

以氯化铝、金属铝粉、氧化钇、冰醋酸为原料,采用溶胶—凝胶法制备了钇铝石榴石纤维。研究氯化铝和金属铝粉比例以及醋酸的加入,对前驱体溶胶纺丝性能的影响。结果表明,加入醋酸可得到纺丝性能良好的前驱胶体溶胶。凝胶纤维在1 000℃煅烧2 h,全部结晶为钇铝石榴石,纤维直径10~40μm。     

溶胶-凝胶法制备95多品氧化铝纤维

以结晶氯化铝、铝粉和硅溶胶为主要原料,用溶胶-凝胶法制备95多晶氧化铝纤维.研究了PEG的加入量和胶体黏度对纤维平均直径和单丝拉伸强度的影响,并对不同温度烧成的纤维单丝拉伸强度和比表面积进行了对比.结果表明:当PEG加入质量分数为4%、胶体黏度为30 Pa·s时,纤维平均直径为3.7 μm,且拥有较好的强度;纤维的比表...     

溶胶黏度、氧化铝含量和旋转盘转速对凝胶纤维直径的影响

采用溶胶凝胶法制备多晶氧化铝纤维,在聚合氯化铝先驱体溶胶中加入5%的硅溶胶和一定的聚乙烯醇及表面活性剂等,真空浓缩制得具有可成纤性的溶胶;在高速旋转盘的离心力作用下甩制成纤维坯体。在固定其他工艺参数的条件下,讨论了在离心力成纤过程中溶胶的黏度、氧化铝含量和旋转盘的转速对凝胶纤维直径的影响。当溶胶内的氧化铝含量在24%左右,黏度为0.2～0.35 Pa.s时,溶胶呈现为牛顿型流体,具有较好的成纤性,制得的纤维坯体细而均匀;而对于黏度为0.35 Pa.s的溶胶,当旋转盘的旋转速率达到300 r/s时,凝胶纤维被再次细化,直径减小至4.4μm。     

溶剂种类对溶胶-凝胶法制备氧化锆阻氢膜层的影响

以正丙醇锆为前驱体,采用溶胶-凝胶法在ZrH_(1.8)表面制备氧化锆阻氢膜层,研究溶剂种类对溶胶-凝胶法制备氧化锆阻氢膜层的影响。采用扫描电子显微镜(SEM)、 X射线衍射仪(XRD)对所制氧化锆阻氢膜层的表面形貌、截面形貌以及相结构进行分析;利用划痕仪考察膜层与基体的结合力,采用真空脱氢实验对膜层的阻氢性能进行评估。研究结果表明,正丙醇为溶剂时,可制得均匀连续、致密的氧化锆膜层,且膜层与基体结合较紧密,膜层平均厚度超过10μm,阻氢效果较好,膜层的氢渗透降低因子(PRF)值可达12.5;乙醇为溶剂时,所制膜层由单斜相氧化锆(M-ZrO_2)和四方相氧化锆(T-ZrO_2)组成,而异丙醇、正丙醇、正丁醇为溶剂时,所制氧化锆膜层由单一的四方相氧化锆(T-ZrO_2)构成。     

热处理气氛对Sol-Gel法在ZrH_(1.8)表面制备氧化锆膜层的影响

采用溶胶凝胶技术,以正丙醇锆为前驱体,在氢化锆表面制备氧化锆防氢渗透层。研究了当热处理温度为600℃时,不同热处理气氛对溶胶凝胶法制备的氧化锆膜层的截面形貌、表面形貌、物相组成以及阻氢性能的影响。利用扫描电子显微镜(SEM)、激光共聚焦显微镜(CLSM)、X射线衍射仪(XRD)和涡流测厚仪分别测试了氧化锆膜层的截面形貌、表面形貌、相结构及厚度。利用真空脱氢实验对膜层的阻氢性能进行评估。研究结果表明,当热处理气氛中有氧存在时,可在氢化锆表面制得连续、致密的氧化锆膜层;而当热处理气氛中无氧存在时,所制备的氧化锆膜层不连续、均匀性差。热处理气氛中有氧时制备的氧化锆膜层的阻氢效果较无氧时要好,膜层厚度为10.1μm,渗透降低因子(PRF)值为8.4。而不同热处理气氛对氧化锆膜层的物相组成没有显著影响,膜层主要由单斜相氧化锆M-ZrO_2和四方相氧化锆TZrO_2组成,并以单斜相氧化锆M-ZrO_2为主。     

气电纺丝法制备硅铝增强氧化铈纳微纤维

通过在聚乙烯吡咯烷酮/硝酸铈(PVP/Ce(NO_3)_3)纺丝液中添加一定比例硅铝溶胶,结合气电纺丝法和高温煅烧工艺成功制备出硅铝增强氧化铈(CeO_2)纳微纤维。采用SEM、XPS、XRD等手段研究了添加比例、电压、风压、煅烧温度等对纤维形貌与结构的影响。结果表明,适量硅铝溶胶的加入,有助于提高PVP/Ce(NO_3)_3纺丝液的粘度;当PVP/Ce(NO_3)_3纺丝液与硅铝溶胶比为6∶1(纺丝液粘度为2.85 Pa·s),纺丝电压为38 kV,风压0.08 MPa时,纺丝效果最佳,制得初生纤维连续、光滑,经高温煅烧后得到纤维材料蓬松、柔软,纤维直径约为1μm~2μm,长度可在10 mm以上;其晶型结构为CeO_2的立方晶系,Si/Al存在一定程度上抑制了CeO_2晶粒的生长,有利于改善纤维的柔韧性。     

添加ZrO2对YAG纤维物相和形貌的影响

以氯化铝、金属铝粉、氧化钇、氧氯化锆、醋酸为原料,采用溶胶-凝胶法制备了钇铝石榴石(YAG)纤维,并研究添加ZrO2对YAG纤维的物相和形貌的影响.结果表明,添加ZrO2的YAG纤维物相仍为钇铝石榴石相,纤维表面光滑且直径均匀;ZrO2可作为YAG纤维的增韧相.     

Luminescence of EPDM rubber ultrafine fibers containing nanodispersed Eu-complexes

Polyvinylpyrrolidone/ethylene-propylene-diene terpolymer (PVP/EPDM) sheath/core fibers, with the incorporation of Eu(TTA) 3 Phen (TTA=2-thenoyltrifluoroacetone, Phen=1,10-phenanthroline) complex (Eu-complex) in EPDM, were prepared by coaxial electrospinning. The composite fibers were further vulcanized by peroxide. Scanning electron microscopy (SEM) observations showed that the composite fibers had an average diameter of about 200 nm and a smooth surface. The dispersion of Eu-complexes in the fibers was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The studies revealed that the Eu-complex was dispersed in the EPDM fibers in the form of molecular clusters and/or nanoparticles with a diameter smaller than 10 nm. Fluorescence spectra and Judd-Ofelt parameters analysis showed that the luminescent quantum efficiency of the composite fibers was greatly improved when the Eu-complex content was 15 wt.%, because the fine dispersion of Eu-complex in EPDM facilitated the increase of radiative transition rate of the composite fibers over that of the neat complex powder.     

静电纺丝法制备氧化钴纳米纤维

采用硝酸钴与聚乙烯吡咯烷酮(polyvinylpyrrolidone, PVP)为原料制备纺丝液, 利用扫描电子显微镜、同步热分析仪、X-射线衍射仪以及透射电子显微镜对前驱体纤维及煅烧后纤维进行表征与分析, 研究静电纺丝技术制备氧化钴纳米纤维的可行性及最佳实验条件。结果表明: 在PVP(K30)质量分数为43%, 硝酸钴质量为2 g以及最佳设备参数条件下, 可以制备出直径约600 nm、均匀光滑的硝酸钴/PVP前驱体纤维, 经600℃高温煅烧后, 可得到直径约30 nm的氧化钴纳米纤维。     

Temperature-dependence mechanism of tensile strength of Si-Ti-C-0 Fiber-Aluminum matrix composites

The mechanism for the temperature dependence of the tensile strength of unidirectional hybrid type Si-Ti-C-O (Tyranno) fiber-reinforced aluminum matrix composite, in which SiC-particles are dispersed in the matrix, is discussed, focusing on the temperature dependencies of the stress concentration arising from broken fibers and critical length and their influences on the composite strength, by means of a shear-lag analysis and a Monte Carlo simulation. The main results are summarized as follows. The softening of the matrix at high temperatures raises the composite strength from the point of decrease in stress concentration, but on the other hand, it also reduces strength from the point of increase in critical length, which reduces the stress-carrying capacity of broken fibers over a long distance. The reason why the measured strength of composite decreased with increasing temperature could be attributed to the predominacy of the latter effect over the former one. The results of the simulation indicated that the hybridization of the composites improved room-temperature and high-temperature strengths through the strengthening of the matrix.     

A metallographic study of extruded reinforced composites based on iron and copper

Microprobe analysis has been applied to the boundary layers between fibers and matrix to examine the phase composition in relation to mode of extrusion for composite materials based on iron and copper as reinforced with molybdenum and steel fibers. The width of the interaction zone varies from 2 to 4 µm. The phases correspond to the phase diagrams for these systems. Fractography indicates the failure mechanism for reinforced composites under conditions of stress and strain. At the points of application of shock loads, there is planar transverse fracture in the fibers by the cleavage mechanism. The peripheral layers are subject to viscous failure in the fibers with the formation of necks. Extrusion produces plastic strain uniform throughout the fiber length, and there are no breaks in the fibers, which provides conditions for complete realization of the strength of the reinforcing phase.     

A metallographic study of extruded reinforced composites based on iron and copper

Microprobe analysis has been applied to the boundary layers between fibers and matrix to examine the phase composition in relation to mode of extrusion for composite materials based on iron and copper as reinforced with molybdenum and steel fibers. The width of the interaction zone varies from 2 to 4 µm. The phases correspond to the phase diagrams for these systems. Fractography indicates the failure mechanism for reinforced composites under conditions of stress and strain. At the points of application of shock loads, there is planar transverse fracture in the fibers by the cleavage mechanism. The peripheral layers are subject to viscous failure in the fibers with the formation of necks. Extrusion produces plastic strain uniform throughout the fiber length, and there are no breaks in the fibers, which provides conditions for complete realization of the strength of the reinforcing phase.     

聚乙烯吡咯烷酮对纳米羟基磷灰石形貌的影响及其机理分析

以Ca(NO3)2.4H2O,(NH4)2HPO4为反应物,聚乙烯吡咯烷酮(PVP)为添加剂,在水热条件下,成功制得了椭球状(长径比1-1.5)的纳米羟基磷灰石(HA)。采用X射线衍射(XRD)、傅里叶变换红外吸收光谱(FTIR)和透射电子显微镜(TEM)等测试手段对所制得的纳米HA进行表征,结果表明PVP能较大程度地影响纳米HA的形貌。纳米HA颗粒的长径比随着PVP浓度的增加而减小,当PVP浓度为1.0%(质量分数)时,纳米HA长径比达最小值(1.5左右)。PVP对纳米HA形貌的调控机制可能是Ca2+与PVP形成配位键和PVP在纳米HA上吸附2种机理协同作用的结果。     

Dynamic Deformation Behavior of Zr-Based Amorphous Alloy Matrix Composites Reinforced with STS304 or Tantalum Fibers

The Zr-based amorphous alloy matrix composites reinforced with stainless steel (STS) or tantalum (Ta) continuous fibers were fabricated without pores or defects by liquid pressing process, and their dynamic deformation behaviors were investigated. Dynamic compressive tests were conducted by a split Hopkinson pressure bar, and then the test data were analyzed in relation to the microstructures and the deformation modes. In the STS-fiber?Creinforced composite, the STS fibers could interrupt the propagation of cracks initiated in the matrix and promoted the continuous deformation without fracture according to the strain-hardening effect of the fibers themselves. The Ta-fiber?Creinforced composite showed the higher yield strength than the STS-fiber?Creinforced composite, but the cracks were not interrupted properly by the Ta fibers according to the lower ductility and strain hardening of the Ta fibers. Both the Ta and STS fibers favorably affected the strength and ductility of the composites by interrupting the propagation of cracks formed in the amorphous matrix, by dispersing the stress applied to the matrix, and by promoting deformation mechanisms such as fiber buckling. The STS-fiber?Creinforced composite showed the higher compressive strength and ductility than the Ta-fiber?Creinforced composite because the STS fibers were higher in the resistance to deformation and fracture than the tantalum fibers.     

Stability of the directionally solidified eutectics NiAl-Cr and NiAl-Mo

The eutectics NiAl-Cr with cylindrical chromium fibers and NiAl-Mo with faceted molybdenum fibers were heated at 1400°C to determine the stability of the composite structure and to compare the stability of the nonfaceted fibers with that of the faceted fibers in the NiAl matrix. Fiber size and size distribution and number of fibers per unit area were measured as a function of time at temperature. The number of fibers in the NiAl-Cr eutectic decreased continuously reaching half the initial value in about 30 h at temperature. Spheroidization of the fibers occurred and was complete in 160 h. In the NiAl-Mo eutectic, the number of fibers per unit area remained constant to 150 h and the fiber size was constant to 331 h at 1400°C. In NiAl-Cr, the cylindrical chromium fibers first formed pinchedoff segments at random diameter variations along the length of the fibers. The segments gradually shortened and thickened and finally spheroidized. The faceted molybdenum fibers remained stable because the Mo-NiAl interface is constrained to lie in the facet plane which inhibits the formation of faults leading to pinching off of the fibers.     

Correlation of tensile strength with fracture modes of KAOWOOL- and SAFFIL-reinforced 339 aluminum

The tensile strengths of composites of 339 aluminum reinforced with either SAFFIL or KAOWOOL fibers are compared over the temperature range of 20°C to 300°C. For this type of composite, in which the discontinuous fibers are randomly oriented, the fibers perpendicular to the applied stress play a critical role, which in turn creates a dependence upon the interfacial bond strength. The KAOWOOL fibers form a strong interfacial bond so that tensile failure occurs either in the matrix at 300 °C or by fiber cleavage at 20°C. In the T5 condition, the SAFFIL interface is weaker than the matrix alloy so that failure occurs by delamination of the transverse fibers. Thus, although the SAFFIL fibers are 40 pct stronger than the KAOWOOL fibers, the T5 composites have the same ultimate tensile strengths. A T6 heat treatment promotes an interfacial reaction with magnesium. This strengthens the SAFFIL interface so that failure occurs primarily in the matrix, producing higher composite strengths. The reaction with the KAOWOOL fibers is so extensive that the matrix, and therefore the composite strength, is drastically decreased. When account is taken of the different fracture modes, together with the matrix strengths as determined by nanoindentation, the calculated values of composite strength are in good agreement with experiment.     

Correlation of tensile strength with fracture modes of KAOWOOL- and SAFFIL-reinforced 339 aluminum

The tensile strengths of composites of 339 aluminum reinforced with either SAFFIL or KAOWOOL fibers are compared over the temperature range of 20 °C to 300 °C. For this type of composite, in which the discontinuous fibers are randomly oriented, the fibers perpendicular to the applied stress play a critical role, which in turn creates a dependence upon the interfacial bond strength. The KAOWOOL fibers form a strong interfacial bond so that tensile failure occurs either in the matrix at 300 °C or by fiber cleavage at 20 °C. In the T5 condition, the SAFFIL interface is weaker than the matrix alloy so that failure occurs by delamination of the transverse fibers. Thus, although the SAFFIL fibers are 40 pct stronger than the KAOWOOL fibers, the T5 composites have the same ultimate tensile strengths. A T6 heat treatment promotes an interfacial reaction with magnesium. This strengthens the SAFFIL interface so that failure occurs primarily in the matrix, producing higher composite strengths. The reaction with the KAOWOOL fibers is so extensive that the matrix, and therefore the composite strength, is drastically decreased. When account is taken of the different fracture modes, together with the matrix strengths as determined by nanoindentation, the calculated values of composite strength are in good agreement with experiment.