氧化锆/氧化铝复合纤维的制备

以硝酸铝、氯氧化锆和酒石酸为原料,聚乙烯吡咯烷酮(PVP)为纺丝助剂,用溶胶—凝胶法制备了氧化锆/氧化铝复合纤维。结果表明,凝胶纤维的长度随PVP掺量增加而增加,凝胶纤维最大长度为60cm;凝胶纤维在1 200℃烧结后,纤维的物相为α-Al2O3和四方ZrO1.88,纤维的直径为4μm,纤维表面光滑,直径均匀。     

不同原料凝胶注模制备莫来石陶瓷的结构与性能

分别以溶胶-凝胶法制备的莫来石粉末和分析纯级氧化铝/氧化硅混合粉末为原料,经过凝胶注模成形后,在1 400~1 600℃温度下无压烧结,制备莫来石陶瓷,研究原料种类及烧结温度对莫来石陶瓷的显微结构、力学性能和抗热震性能的影响。结果表明:以溶胶-凝胶法制得的莫来石粉末为原料时,随烧结温度升高,陶瓷的密度和抗弯强度都是先升高后降低,烧结温度为1 500℃时,材料的密度和抗弯强度最高,分别为3.13 g/cm~3和155.85MPa,经过5次1 400℃?100℃沸水间热震后抗弯强度保留率达54.99%。以氧化铝/氧化硅混合粉末为原料时,起始烧结温度降低,1 400℃下烧结的陶瓷即具有较高的密度和抗弯强度,分别为3.01 g/cm~3和106.40 MPa,热震后的抗弯强度保留率为77.80%。抗弯强度随烧结温度升高而下降,烧结温度为1 600℃时抗弯强度下降至74.21MPa。     

铬纤维复合模块与多晶莫来石纤维复合模块的比较分析

对含铬硅酸铝纤维复合模块和多晶莫来石纤维复合模块的结构进行研究,并重点对含铬硅酸铝纤维复合模块各组成部分的材质进行检测,在此基础上剖析了两种复合模块的优缺点.结果表明,多晶莫来石纤维复合模块的综合性能优于含铬硅酸铝纤维复合模块.     

碱度对腐泥土型红土镍矿烧结行为的影响

 为了研究腐泥土型红土镍矿在焙烧过程中物相转变及固结机制问题,通过微型烧结试验和三角锥法软熔特性试验,对原矿和焙烧后的团块进行了化学成分、X射线衍射(XRD)和软熔特性分析,并通过添加熔剂CaO改变团块碱度,结合冶金相图进行了分析。研究结果表明,自然碱度的红土镍矿经高温焙烧后主要由尖晶石(MgFe2O4)、镁橄榄石((Mg,Fe)2SiO4)和顽火辉石(MgSiO3)构成。随着碱度从0.5上升到2.0,顽火辉石相继转变为低熔点的透辉石(CaMgSi2O6)和高熔点的镁黄长石(Ca2MgSi2O7)以及镁蔷薇辉石(Ca3MgSi2O8)。红土镍矿的软熔温度也随碱度的提高先降低后升高,在碱度为1.0时达到最低点。结合冶金相图分析得知,通过改变碱度可以显著增加红土镍矿烧结过程液相量,红土镍矿烧结理想的黏结相为透辉石。     

脱硫枪用莫来石—刚玉浇注料流动性的研究

以天然莫来石、电熔莫来石、刚玉粉为主要原料,研究了粒度级配、微粉种类和加入量、减水剂种类和加入量的对脱硫枪用莫来石—刚玉浇注料流动性的影响：先研究硅微粉加入量分别为2％、3％、4％、5％对浇注料流动性的影响;然后将硅微粉加入量固定为2％或3％,研究α—Al2O3微粉加入量分别为0、2％、4％、6％时对浇注料的流动性影响;最后研究三聚磷酸钠、六偏磷酸钠、SM、FDN四种减水剂对莫来石-刚玉浇注料流动性的影响,三聚磷酸钠和六偏磷酸钠的加入量分别选取0．1％、0．15％、0．2％、0．25％,SM加入量选取0．2％、0．3％、0．4％、0．5％,FDN的加入量选取0．1％、0．15％、0．2％、0．25％。试验结果表明：硅微粉对流动性的改善作用优于氧化铝微粉,但二者共用时对流动性的改善作用比单用硅微粉更好,此时最适宜的加入量为硅微粉％、氧化铝微粉2％;本试验中最适宜的减水剂是六偏磷酸钠,最佳加入量为0．15％。     

刚玉／莫来石—硼化锆陶瓷材料的烧结工艺及显微结构

研究了常压条件下刚玉／莫来石—硼化锆陶瓷材料的烧结工艺及其显微结构。实验表明，在中性气氛下，适当地选择氧化物比例，加入一定量的添加剂，并控制好烧结温度，材料可以致密烧结。通过正交实验选出优良配方的刚玉与莫来石比值应为３∶２。添加剂的加入量为５％，烧结温度为１６８０℃。     

热镀锌层表面复合氧化硅膜层的制备及性能

为改善热镀锌层的耐蚀性能,本文采用溶胶-凝胶法(sol-gel)在热镀锌层上涂覆有机-无机复合氧化硅膜层.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、粘结法和孔隙率试验对不同氧化硅膜层形貌、结构、结合力及致密性进行测试分析,并通过电化学试验和浸泡试验对热镀锌层涂覆氧化硅膜层前后的耐蚀性能进行测试.结果表明,所...     

多晶莫来石纤维在连轧加热炉上的应用

为了节约能源、改善操作环境，广钢连轧厂在加热炉炉顶试用了多晶莫来石纤维。本文通过对材料的选用、施工以及使用效果进行分析，论述了多晶莫来石纤维可以在燃用重油的轧钢加热炉上使用。     

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。     

多晶莫来石纤维复合制品真空成型块在全氢罩式炉上的应用

介绍一种国产新型绝热材料多晶莫来石纤维复合制品真空成型块在引进全氢罩式炉上的应用及使用效果。     

化学镀碳纤维增韧补强莫来石基复合材料的研究

通过化学镀方法，在碳纤维表面分别镀上Ni、Cu和Cu Ni镀层，以这种表面改性碳纤维与莫来石陶瓷复合，制备表面改性碳纤维增韧补强莫来石基复合材料，研究各种碳纤维的含量对复合材料的横向断裂强度、断裂韧度、尺寸变化率和孔隙度等的影响规律。结果表明，碳纤维可以显著地提高材料的性能，表面改性碳纤维可以进一步提高材料性能，尤其是铜镍复合镀碳纤维的效果更好，其横向断裂强度可达基体横向断裂强度的2．3倍，断裂韧度可达基体断裂韧度的3倍，增韧补强后的复合材料的尺寸变化率和孔隙率变化不大。     

化学镀碳纤维增强羟基磷灰石复合材料的性能

通过化学镀方法,在碳纤维表面分别镀上Ni和Cu+Ni镀层,以这种表面改性碳纤维与羟基磷灰石陶瓷复合,制备表面改性碳纤维增韧增强羟基磷灰石复合材料,研究各种碳纤维的含量对复合材料的抗弯强度、断裂韧度、尺寸变化率和孔隙率的影响。结果表明,表面改性碳纤维可以显著提高材料的性能,尤其是铜镍复合镀碳纤维的效果更好,其断裂韧度可达基体断裂韧度的2.5倍,抗弯强度可达基体抗弯强度的3.4倍,增韧增强后的复合材料的尺寸和孔隙率变化不大。     

纤维分散对C/C-SiC复合材料力学性能的影响

利用温压-原位反应法制备短炭纤维增强C/C-SiC复合材料,研究纤维分散对复合材料力学性能的影响.结果表明: 利用分散短炭纤维制备的C/C-SiC复合材料,其抗弯强度和抗压强度分别达到56.6MPa和89.3MPa.该材料纤维之间孔隙少,纤维与基体接合界面多,弯曲时有纤维拔出,为假塑性断裂行为.压缩时无纤维拔出,为脆性断裂行为.最后,利用LI V C提出的束丝数学模型证明了纤维分散有利于提高C/C-SiC复合材料的力学性能.     

原位转化碳纤维增韧氧化铝复合材料的制备工艺

以聚丙烯腈预氧化纤维为先驱纤维,使其在真空烧结过程中原位转化生成碳纤维来增韧氧化铝陶瓷材料.利用热重–差热分析和X射线衍射研究了聚丙烯腈预氧化纤维的相结构和化学结构以确定制备复合材料的升温烧结工艺,并探讨了加压方式和聚丙烯腈预氧化纤维含量对复合材料组织结构和性能的影响.研究发现聚丙烯腈预氧化纤维在差热曲线上444℃左右的放热峰和X射线衍射图谱中17左右的衍射峰是由预氧化阶段残留的未充分氧化的聚丙烯腈分子引起的;而1073℃左右的吸热峰和25.5左右的衍射峰说明预氧化纤维在加热烧结过程中已开始向碳纤维转变.热压烧结制备的复合材料的力学性能明显优于无压烧结.随着聚丙烯腈预氧化纤维含量的增加,复合材料的密度和显微硬度降低,而断裂韧性则先升高后降低,当聚丙烯腈预氧化纤维体积分数为20%时,复合材料的断裂韧性最大,达9.39MPa·m1/2,说明原位碳纤维的生成提高了复合材料的断裂韧性,其增韧机制主要为纤维拔出和脱黏.      

Mechanical property and fracture behavior of squeeze-cast Mg matrix composites

The present study aims to investigate the microstructure and fracture properties of AZ91 Mg matrix composites fabricated by the squeeze-casting technique, with variations in the reinforcement material and applied pressure. Microstructural and fractographic observations, along with in situ fracture tests, were conducted on three different Mg matrix composites to identify the microfracture process. Two of them are reinforced with two different short fibers and the other is a whisker-reinforced composite. From the in situ fracture observation of Kaowool-reinforced composites, the effect of the applied pressure on mechanical properties is explained using a competing mechanism: the detrimental effects of fiber breakage act to impair the beneficial effects of the grain refinement and improved densification as the applied pressure increases. On the other hand, for the composites reinforced with Saffil short fibers, microcracks were initiated mainly at the fiber/matrix interfaces at considerably higher stress intensity factor levels, while the degradation of fibers was not observed even in the case of the highest applied pressure. This finding indicates that the higher applied pressure yields better mechanical properties, attributable to the Saffil short fibers having relatively high resistance to cracking. Although an improved microstructure was obtained by accommodating the appropriate applied pressure in the short fiber-reinforced composites, their mechanical properties were far below those of conventional A1 matrix composites. In this regard, the Alborex aluminum borate whisker is suggested as a replacement for the short fibers used in the present investigation, to achieve better mechanical properties and fracture toughness.     

Fibridization Effect on the Mechanical Behavior of PA66/PTFE Blend Based Fibrous Composites

The use of natural fiber along with the glass fiber in polymer composites is one of the present material combinations for automotive industries. This article deals with the hybrid effect of 10 wt% short glass fibers (SGF) and 10 wt% short basalt fibers (SBF) on the mechanical behavior of 80 wt% PA66/20 wt% Teflon (PA66/PTFE) blend. These composite materials were prepared by melt mixing method, by using twin screw extruder followed by injection molding. The mechanical performance of the composite materials was tested as per ASTM method. The experimentally determined mechanical properties were tensile behavior, flexural behavior and impact behavior. Hardness and density of the blended composites were also studied. Experimental results revealed that the effect of hybrid short fibers on the blend greatly enhanced the mechanical behavior. Increase in tensile strength and flexural strength by 33% and 57% respectively and 6% reduction in elongation was exhibited by the blend due to the hybrid effect of fibers. The synergistic effect between the fibers and the matrix blend improved the mechanical behavior. The strain rate of the hybrid composites was deteriorated due to the hybrid effect. The enhancement of load carrying capacity by 17.35, 8.5 and 36% was exhibited by SGF, SBF and hybrid fiber filled PA66/PTFE blend composites respectively. The impact strength of the hybrid composites was reduced due to the brittle nature of the hybrid filled composites. Fiber fracture, fiber pull out and fiber misalignment were the certain mechanisms observed during mechanical performance. The fractured surfaces were analyzed through Scanning Electron Microscopy photographs.     

Influence of fabrication technique on the fiber pushout behavior in a sapphire-reinforced NiAl matrix composite

Directional solidification (DS) of “powder-cloth” (PC) processed sapphire-NiAl composites was carried out to examine the influence of fabrication technique on the fiber-matrix interfacial shear strength, measured using a fiber-pushout technique. The DS process replaced the fine, equiaxed NiAl grain structure of the PC composites with an oriented grain structure comprised of large columnar NiAl grains aligned parallel to the fiber axis, with fibers either completely engulfed within the NiAl grains or anchored at one to three grain boundaries. The load-displacement behavior during the pushout test exhibited an initial “pseudoelastic” response, followed by an “inelastic” response, and finally a “frictional” sliding response. The fiber-matrix interfacial shear strength and the fracture behavior during fiber pushout were investigated using an interrupted pushout test and fractography, as functions of specimen thickness (240 to 730 μm) and fabrication technique. The composites fabricated using the PC and the DS techniques had different matrix and interface structures and appreciably different interfacial shear strengths. In the DS composites, where the fiber-matrix interfaces were identical for all the fibers, the interfacial debond shear stresses were larger for the fibers embedded completely within the NiAl grains and smaller for the fibers anchored at a few grain boundaries. The matrix grain boundaries coincident on sapphire fibers were observed to be the preferred sites for crack formation and propagation. While the frictional sliding stress appeared to be independent of the fabrication technique, the interfacial debond shear stresses were larger for the DS composites compared to the PC composites. The study highlights the potential of the DS technique to grow single-crystal NiAl matrix composites reinforced with sapphire fibers, with fiber-matrix interfacial shear strength appreciably greater than that attainable by the current solid-state fabrication techniques.     

Transverse strengths and failure mechanisms in Ti3Al matrix composites

Transverse mechanical properties have been measured, and damage mechanisms identified, in three Ti₃Al matrix composites with different interface compositions and residual stress states. Two of the composites contained SiC fibers with weak interfaces. Large improvements in transverse strength and rupture strain were found in one of these composites, in which brittle reaction products in the matrix around the fibers had been avoided by coating the fibers with Ag and Ta before consolidation. The third composite contained sapphire fibers that were strongly bonded to the matrix. Different damage mechanisms were observed in the strongly and weakly bonded composites. Insight into the damage mechanisms and their dependence on residual stress fields and interface properties is gained from comparison of the observations with analytical solutions of elastic stresses. The conditions for optimum transverse properties are discussed; the results indicate that strong interfacial bonding does not necessarily lead to optimum transverse strength of the composite.     

放电等离子烧结制备非连续石墨纤维/Cu复合材料

以磨碎中间相沥青基石墨纤维和铜粉为原料,通过放电等离子烧结(spark plasma sintering,SPS)制备非连续石墨纤维/Cu复合材料,对石墨纤维表面进行镀钛金属化处理,以改善材料的界面结合状况.研究SPS工艺参数、铜粉粒度搭配、石墨纤维表面镀钛以及石墨纤维含量对石墨纤维/Cu复合材料致密度及热导率的影响.结果表明,将平均粒度为12和80 μm的铜粉按1∶2的质量比搭配,再与表面镀钛石墨纤维按1∶1的体积比混合,采用35 MPa先加压后送热的加压方式,于895℃下进行放电等离子烧结,可获得致密度达99.6％、热导率为364 W/(m·K)的石墨纤维/Cu复合材料,是1种很有潜力的电子封装材料.石墨纤维表面镀覆的极薄Ti镀层,可使复合材料在二维平面方向上的热导率从196 W/(m·K)提高到364 W/(m·K).     

Effect of δ alumina fibers on the aging characteristics of 2024-based metal-matrix composites

The age-hardening precipitation reaction in aluminum matrix composites reinforced with discontinuous alumina fibers was studied using the differential scanning calorimetry (DSC) technique, microhardness tests, and transmission electron microscopy (TEM) observation. Composites fabricated with the 2024 alloy matrix were infiltrated through a ceramic preform using a squeeze-casting process. The alumina fibers had a considerable effect on the aging response of the matrix alloy in composites. Alumina fibers caused suppression of Guinier—Preston (GP) zone formation in composite that reduced the peak hardening during artificial aging. The suppression of GP zone formation in composites is believed to be due to the fiber-matrix interface, which acts as a sink for vacancies during quenching. Moreover, the presence of reinforcement does not alter the kinetics of the subsequent artificial aging of these Al₂O₃/2024Al composites.