Low-temperature heat conduction characteristics of diamond/Cu composite by pressure infiltration method

In this paper,diamond/CuCr and diamond/CuB composites were prepared using the pressure infiltration method.The physical property measurement system(PPMS)was adopted to evaluate the thermal conductivity of diamond/Cu and MoCu composites within the range of100–350 K,and a scanning electron microscope(SEM)was utilized to analyze the microstructure and fracture appearance of the materials.The research indicates that the thermal conductivity of diamond/Cu composite within the range of100–350 K is 2.5–3.0 times that of the existing MoCu material,and the low-temperature thermal conductivity of diamond/Cu composite presents an exponential relationship with the temperature.If B element was added to a Cu matrix and a low-temperature binder was used for prefabricated elements,favorable interfacial adhesion,relatively high interfacial thermal conductivity,and favorable low-temperature heat conduction characteristics would be apparent.

Effect of specific pressure on fabrication of 2D-C_f/Al composite by vacuum and pressure infiltration

Carbon fiber reinforced aluminum matrix （Cf/Al） composite has many excellent properties, and it has received more and more attention. Two-dimensional （2D） Cf/Al composites were fabricated by vacuum and pressure infiltration, which was an integrated technique and could provide high vacuum and high infiltration pressure. The effect of specific pressure on the infiltration quality of the obtained composites was comparatively evaluated through microstructure observation. The experimental results show that satisfied Cf/Al composites could be fabricated at the specific pressure of 75 MPa. In this case, the preform was infiltrated much more completely by aluminum alloy liquid, and the residual porosity was seldom found. It is found that the ultimate tensile strength of the obtained Cf/Al composite reached maximum at the specific pressure of 75 MPa, which was improved by 138.9% compared with that of matrix alloy.

Effect of Al2O3sf addition on the friction and wear properties of (SiCp+Al2O3sf)/Al2024 composites fabricated by pressure infiltration

Aluminum(Al) 2024 matrix composites reinforced with alumina short fibers(Al_2O_(3sf)) and silicon carbide particles(SiC_p) as wear-resistant materials were prepared by pressure infiltration in this study. Further, the effect of Al_2O_(3sf) on the friction and wear properties of the as-synthesized composites was systematically investigated, and the relationship between volume fraction and wear mechanism was discussed. The results showed that the addition of Al_2O_(3sf), characterized by the ratio of Al_2O_(3sf) to SiC_p, significantly affected the properties of the composites and resulted in changes in wear mechanisms. When the volume ratio of Al_2O_(3sf) to SiC_p was increased from 0 to 1, the rate of wear mass loss(K_m) and coefficients of friction(COFs) of the composites decreased, and the wear mechanisms were abrasive wear and furrow wear. When the volume ratio was increased from 1 to 3, the COF decreased continuously; however, the K_m increased rapidly and the wear mechanism became adhesive wear.

Threshold pressure and infiltration behavior of liquid metal into fibrous preform

A dynamic measuring apparatus was developed to investigate the infiltration process of liquid metal into the fibrous preform. 10% （volume fraction） chopped carbon fiber preforms were infiltrated with magnesium alloy under different infiltration pressures. The threshold pressure and flow behavior of liquid metal infiltrating into the preforms were calculated and measured. The microstructure of obtained Ct4Mg composites was observed. The results indicate that the measured threshold pressure for infiltration was 0.048 MPa, which was larger than the calculated value. The infiltration rate increased with the increase of infiltration pressure, but the increase amplitude decreased gradually. The tiny pores in the composites could be eliminated by increasing the infiltration pressure. When the infiltration pressure rose to 0.6 MPa, high quality C1/Mg composite was obtained.

On the liquid-phase technology of carbon fiber/aluminum matrix composites

The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers’surface.This paper aims to solve these problems.The theoretical and experimental dependence of porosity on the applied pressure were determined.The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown.The correlation among the strength of the carbon fiber reinforced aluminum matrix composite,the fracture surface,and the degradation of the carbon fiber surface was discussed.

高低温对碳纤维/环氧树脂复合材料高压气瓶的性能影响

为了获得T1000碳纤维/环氧树脂复合材料高压气瓶环境适应能力,有效地掌握气瓶高低温适应性固有规律,以容积50 L、工作压力30 MPa的复合材料气瓶(钛为内衬、碳纤维/环氧树脂为复合层)为研究对象,首先介绍了高低温循环下带压气瓶(在-40~80℃范围内成功通过热真空、热循环验证,具备高压承载能力)的热真空、热循环试验数据,然后采用与气瓶相同复合材料的拉伸试样(缠绕角分别为0°和90°),通过高低温极限摸底试验获得了复合材料经历不同梯度高低温后的拉伸性能数据,通过数据比对分析获得了高低温影响拉伸强度衰减的规律。同时,提出了一种高低温极限摸底试验的可靠性评估方法。结果表明,在-50~100℃范围内,试样拉伸强度及断裂伸长率变化较小;当温度高于100℃时,纤维和树脂的性能发生衰减,导致拉伸强度明显降低;当温度低于-50℃时,树脂的性能发生衰减,纤维受到的影响较小。试样高低温极限摸底试验的可靠度大于0.999,表明采用拉伸试样高低温拉伸强度数据的替代方式具有较高的等效性。

界面聚合法制备低压中空纤维纳滤复合膜

现有中空纤维纳滤膜在实际应用中能耗较高.采用干湿法纺丝技术制备聚砜(PSf)中空纤维超滤膜作为基膜,分别选用哌嗪(PIP)和均苯三甲酰氯(TMC)为水相单体和有机相单体,通过界面聚合工艺的优化,成功制备了低压中空纤维纳滤膜.用扫描电子显微镜和原子力显微镜对膜表面形貌进行表征,用傅里叶变换红外光谱仪和X射线光电子能谱仪分析膜表面的化学结构和元素组成,测试了复合膜的表面水接触角、Zeta电位、截留分子量和孔径分布,研究了单体浓度、界面聚合反应时间以及测试压力对复合膜性能的影响并确定了最佳的工艺条件.结果表明,优化的低压中空纤维纳滤膜具有低交联度的聚酰胺功能层,在0.2 MPa的测试压力下,纯水通量达到(16.0±0.4)L/(m^(2)·h),对质量浓度为1 g/L的盐溶液的截留率为Na_(2)SO_(4)(94.2%±0.9%)>MgSO_(4)(92.2%±0.9%)>MgCl_(2)(51.0%±0.5%)>NaCl(9.5%±0.3%),表现出优异的Na_(2)SO_(4)/NaCl选择性.

一种考虑应变率的复合材料动态压缩响应预测模型

本文提出一种考虑应变率效应的复合材料动态压缩响应预测模型,该模型基于人工神经网络,根据材料的弹性模量等属性参数即可预测其不同应变率下的动态压缩响应。建立了T300/QY8911预浸料制备的碳纤维增强复合材料高应变率压缩响应预测模型,预测了该材料应变率为517 s^(-1)、721 s^(-1)和1070 s^(-1)时的动态压缩响应,并开展试验,对预测结果进行了验证。结果表明,预测结果与试验结果吻合度较高,应力最大误差仅为-1.5856%,应变最大误差仅为1.7037%。

低浸渗压力制备纤维增强铝基复合材料

利用液态浸渗技术制备了氧化铝纤维增强铝基复合材料。研究结果表明，在低压下使液态合金浸渗纤维预制件制备铝基复合材料是可行的。在浸渗过程中，液态合金的温度对浸渗压力有较大影响。所制备的复合材料具有均匀的显微组织，基体中的共晶组织可依附在纤维表面形核生长。

硅溶胶强化辅助制备C纤维增韧氧化铝结合莫来石陶瓷基复合材料

通过氧化铝先驱体溶液循环浸渍热解结合硅溶胶浸渗强化的方法制备了三维C纤维预制体增韧的氧化铝结合莫来石陶瓷基复合材料 ,研究了氧化铝浸渗工艺对试样增重率、气孔率以及热处理温度对试样内气孔尺寸和分布的影响 ,分析了复合材料物相、微结构以及复合材料的力学性能。结果表明 ,硝酸铝饱和溶液浸渗纤维预制体并热解后试样的增重率和开气孔率呈类似抛物线曲线 ;由于硝酸铝分解生成氧化铝的煅烧温度不同 ,氧化铝晶态及物理特性不同 ,试样内气孔尺寸和分布差别较大 ;选择经过 115 0℃预处理的试样进行硅溶胶浸渗 ,然后 14 0 0℃处理 2h ,氧化硅与氧化铝完全反应生成莫来石 ,获得了较为致密的复合材料 ,室温三点弯曲强度和断裂应变分别为 180MPa和 2 .2 %。

低浸渗压力制备短纤维增强铝硅合金复合材料

利用液态浸渗技术制备了氧化铝纤维增强铝基复合材料。结果表明 ,在低压下使液态合金浸渗纤维预制件制备铝基复合材料是可行的 ,在浸渗过程中 ,液态合金的温度对浸渗压力有较大影响。所制备的复合材料组织均匀 。

低浸渗压力制备氧化铝/锌合金复合材料

利用液态浸渗技术制备了氧化铝／锌合金复合材料。研究结果表明，在低浸渗压力下制备金属基复合材料是可行的；在浸渗过程中，液态金属的温度对浸渗压力有较大影响。所制备的复合材料具有均匀的凝固组织，纤维与基体中的活性元素的相互作用有利于锌合金的共晶组织生核和长大。

复合材料轴结构力学性能预测及铺层方案设计

针对连续纤维增强金属基复合材料轴结构力学性能预测问题,考虑纤维呈四边形和六角形两种周期性排列方式,基于细观力学有限元方法,建立六种代表体积元(RVE)模型,计算该材料的宏观力学性能参数,并与已有的三种细观力学模型计算结果进行对比分析。在此基础上,以低压涡轮轴为研究对象,将选定的RVE模型预测所得的宏观力学性能参数应用于该纤维增强复合材料轴结构的铺层方案设计中,利用数值模拟方法计算该轴结构在给定弯矩、扭矩作用下的变形量和应力,并分析铺层角度、厚度及铺层顺序对轴结构抗弯、抗扭性能的影响规律。研究发现纤维按某种特定的铺层角度组合铺设,可有效提高轴结构的抗弯、抗扭性能,通过计算分析提出了铺层设计方案。

碳纤维增强铝基复合材料的低压铸造

本文分析了液态金属浸渗静力学和动力学。通过实验测定渗透系数。分四种情况讨论了C/Al浸渗复合过程和复合质量。指出,润湿并不是低压力下制备复合材料的必要条件。通过控制纤维分布状态,使纤维成束分布,在不润湿的情况下,也可以在低压力下制造高质量复合材料。最后用非均匀浸渗技术制出高强度C/Al复合材料。

碳纤维增强酚醛树脂/石墨复合材料双极板的低温热模压试验研究

介绍了国外制备树脂/石墨复合材料双极板的研究结果。研究了低温热模压成型工艺制备酚醛树脂/石墨复合材料双极板,结果表明:酚醛树脂含量为15wt%时,复合材料的导电性能满足双极板的要求,但力学性能偏低。提出了碳纤维增强的解决方案,研究了碳纤维表面处理方法以及碳纤维含量对复合材料导电性能与力学性能的影响。得到对碳纤维进行液相氧化处理,碳纤维含量3wt%是综合性能较好的一种试验方案。采用低温热模压工艺制备低成本酚醛树脂/石墨复合材料双极板,双极板材料的性能突破必将促进燃料电池的商业化发展。

挤压铸造短纤维增强金属基复合材料浸渗过程分析

在分析挤压铸造金属基复合材料浸渗条件的基础上，建立了液态金属在短纤维预制件中的浸渗和压力分布模型，计算结果表明：（１）当外加压力不足以使短纤维预制件产生变形之前，其浸渗距离和浸渗前端的压力分别为：Ｘｆ＝１－Ｆ１－Ｖｆ∫ｔ０ｕｄｔ和Ｐｓ＝μｕＫ０１－Ｆ１－Ｖｆ∫ｔ０ｕｄｔ－４Ｖｆ０γｃｏｓθｄｆ（１－Ｖｆ０）（２）当外加压力使短纤维预制件产生变形之后，其浸渗距离和浸渗前端的压力分别为：Ｘｆ＝１－Ｆ１－Ｖｆ∫ｔ１０ｕｄｔ＋∫ｔｔ１ｕ（１－Ｆ）Ｋ（１－Ｖｆ）ｄｔ和Ｐｓ＝μｕＫ０１－Ｆ１－Ｖｆ∫ｔ１０ｕｄｔ＋μｕ∫ｔｔ１ｕ（１－Ｆ）Ｋ（１－Ｖｆ）ｄｔ－４Ｖｆγｃｏｓθｄｆ（１－Ｖｆ）

低压浸渗法制备Gr（C）／Mg复合材料

对用低压浸渗法制备石墨（碳）长纤维镁基复合材料进行了研究。结果表明，制备工艺条件对复合状况、界面反应及复合材料性能均有明显影响。通过纤维表面ＳｉＯ２涂层处理和优化浸渗工艺，可成功地制备出高性能的复合材料，拉伸断裂强度可达５０９ＭＰａ，模量亦可达１４２ＧＰａ。

辣椒膳食纤维的低温超高压改性

低温超高压技术作为一种新兴的食品加工技术,在膳食纤维提取改性中具有独特的优势,该文探讨了低温超高压对辣椒渣膳食纤维构成及物理化学特性的影响,结果表明:当设定压强300 MPa,在60℃下处理40min,SDF含量稍有降低,IDF含量有所提高,TDF几乎没有变化。但是经过改性处理,膳食纤维的持水力、持油力、膨胀力分别提高到原来的1.4,1.6,1.2倍。为进一步了解和提高膳食纤维的生理活性、综合开发利用等提供重要的依据。

纤维增强复合材料涡轮轴结构静强度计算与分析

基于适用于纤维增强复合材料的细观力学代表体积元(RVE)法和材料强度失效参数计算公式,计算体积分数为40%的SCS-ULTRA纤维增强TC17基复合材料的力学性能参数和强度失效参数,建立以实际某型号发动机低压涡轮轴为背景,并用SCS-ULTRA纤维增强TC17基复合材料代替原有高温合金材料,应用复合材料宏观强度准则中的蔡—吴张量失效准则,对其进行静强度计算与失效判定,总结作为衡量趋近失效程度的蔡—吴强度指数随轴结构复合材料铺层数的变化规律,同时对铺层总数为27层的轴结构进行给定载荷下的强度计算,得出轴结构内部每一铺层的强度指数及铺层强度指数随铺层位置、45°铺角不同的变化规律,并预测在极限载荷下轴结构铺层首先出现失效的情况。

中空纤维反渗透复合膜的制备及分离性能研究

通过间苯二胺水溶液和均苯三甲酰氯的正己烷溶液的界面缩聚反应,以聚砜中空纤维超滤膜为基膜,制备了聚芳香酰胺反渗透复合膜。用扫描电镜对复合膜的表面及断面进行表征,探索了复合膜在不同操作条件以及进液性质下的分离性能。研究结果表明:中空纤维反渗透复合膜具有良好的耐压密性和稳定性,在0.7MPa下具有良好的分离性能。此复合膜对NaCl、KCl、CaCl2、MgCl2、MgSO4、Na2SO4等无机盐水溶液的脱盐率不低于93.5%,通量大于21L/(m2.h);对天津市大港、小站两地的苦咸水具有优异的淡化性能;对天津市自来水中的盐分也有良好的去除率。