(SiC)P表面化学修饰及其热力学机理分析

利用简单的化学镀技术,通过改进前处理工艺,实现了(SiC)p的表面化学改性.通过对反应条件的分析比较,确定了最佳温度为40℃、pH值9.0;采用SEM、EDS和XRD,对修饰前、后(SiC)p的物相、晶形、成分等进行了研究,获得了镀层连续,无光滑(SiC)p裸露的较高质量的改性碳化硅复合粉体[简写为(Ni/SiC)p].同时对(SiC)p表面改性的热力学机理给出初步分析,并从理论上验证了反应条件.     

SiC颗粒的表面修饰及结构表征

利用简单的化学镀方法,实现了SiC颗粒的表面化学修饰.通过对酸性、碱性修饰液的比较研究,证实在相同条件下,碱性镀液的修饰效果较好;采用SEM,TEM,EDS和XRD,对修饰前、后的SiCP的物相、晶形、成分等进行了研究,初步表征了Ni/SiC颗粒复合粒子的微结构;并考察了热处理对修饰后SiC颗粒的影响.     

纳米SiC表面接枝修饰的XPS研究

聚合物在纳米粒子表面接枝后,可在其表面建立起空间位阻稳定层,提高纳米粒子的分散稳定性及其与树脂基体的相容性.本文采用缩聚法在纳米SiC表面接枝了聚缩醛,X射线光电子能谱(XPS)的分析结果表明,经过聚缩醛接枝改性的纳米SiC表面Si2p峰明显降低,而C1s峰和O1s峰明显地增长,对C1s、Si2p峰精细扫描及分峰拟合表明,纳米SiC表面碳元素中有38.4%属于接枝物聚缩醛的有机碳,而79.8%的Si元素结合能增加了2.5eV,由此表明,纳米SiC表面形成了良好的表面修饰层,接枝物聚缩醛以化学键结合于纳米SiC表面;对比XPS和热失重分析(TG)的数据结果,可以推测,聚缩醛主要分布在纳米SiC的表面,而在体相中独立存在的几率较小.     

Ni-P-(Ni/SiC)P化学复合镀层的研究

为解决裸(SiC)p在实际应用中存在的不足,采用简单的化学镀方法对其表面进行改性,得到了包覆型的改性(Ni/SiC)p,以(Ni/SiC)p为第二相粒子制备了Ni-P-(Ni/SiC)p化学复合镀层,经扫描电镜、能量散射仪、硬度等测试,并与常见的Ni-P化学镀层、Ni-P-(SiC)p化学复合镀层比较,结果显示:Ni-P-(Ni/SiC)p镀层具有组成均匀、硬度高、镀层耐磨损等优点,为(SiC)p增强金属镀层及基体材料的研究提供了一个新的思路.     

Ni-P-(Ni/SiC)P镀层及其工艺条件的研究

为解决Ni-P-(SiC)P镀层中基体的金属键与增强体的共价键间相容性差,增强体颗粒易脱落,镀层性能降低等问题.采用简单的化学镀方法实现了(SiC)P表面修饰、改性,得到了涂覆型改性(Ni/SiC)P,以(Ni/SiC)P为第二相粒子制备了Ni-P-(Ni/SiC)P化学复合镀层,并初步分析了复合镀机理.实验结果表明:温度、pH值、搅拌速率及(Ni/SiC)P加入量对Ni-P-(Ni/SiC)P镀层的沉积速率及沉积量有较大的影响,本实验条件下的最佳温度为82~86℃;最佳pH值为4.2~4.6;最佳搅拌速率为200 r/mim;最佳粒子加入量10 g/L.SEM、EDS分析显示Ni-P-(Ni/SiC)P镀层均匀、致密,Ni、P、Si沉积量大,耐磨性实验证明Ni-P-(Ni/SiC)P化学复合镀层硬度、耐磨性优于常见的Ni-P、Ni-P-(SiC)P镀层.经表面修饰、改性后得到的(Ni/SiC)P可以进一步提高Ni-P-(SiC)P镀层的使用性能.     

MH/Ni电池负极材料储氢合金表面修饰及性能研究

探索了一种储氢合金表面修饰的新方法,应用HF和CuSO4混合溶液对MH/Ni电池负极AB5型储氢合金进行表面处理.研究了HF含量对合金表面修饰的影响,考察了修饰后合金电极的电化学性能,应用交流阻抗分析了表面处理对合金性能影响的作用机理.结果表明,表面修饰使合金表面活性增加,导电性增强,使合金电极具有更好的活化速度和高倍率放电能力.另外,表面修饰还抑制了合金的粉化、氧化,改善了合金电极的循环性能.因此,表面修饰合金作为MH/Ni电池负极材料可以更好的满足电动车用动力型电源的性能要求.     

SiC纳米/微米粒子表面修饰、涂覆的研究进展

回顾了近些年SiC纳米/微米微粒表面修饰、涂覆的研究进展,分析了影响SiC粒子表面修饰、涂覆的主要因素,并进一步论述了该领域现阶段的发展水平及存在的问题,预测了它的发展前景.     

Ni修饰层对SnO2薄膜气敏性能影响

采用磁控溅射技术在SnO2薄膜表面修饰金属Ni，研究Ni修饰量对SnO2薄膜气敏性能影响。对Ni-SnO2薄膜进行表面成分分析，发现Ni的表面含量和化学价态对Ni-SnO2薄膜气敏性能影响至关重要。Ni的表面修饰量在3．4％-8．8％之间将有效提高SnO2薄膜对低浓度氢气的敏感性能。180℃工作温度下，表面含Ni3．4％的SnO2薄膜对1000ppm的氢气灵敏度最高为59．6，同时响应时间和恢复时间降低至15s和125s。Ni修饰量增加到23．4％，薄膜的气敏性能恶化，这是因为修饰层过厚，阻碍气体与SnO2材料接触。同时，XPS证实NiO是增加SnO2薄膜气敏性能的主要物质，增敏机理解释为Ni氧化后形成的NiO在SnO2薄膜上形成p-n结，促进元件的电导变化，从而提高了薄膜的气敏性能。     

SDBS修饰碳纳米管及其增强聚乳酸复合材料的制备与表征

采用十二烷基苯磺酸钠(SDBS)对碳纳米管进行表面修饰,并以其为增强体,利用溶剂蒸发法制备了碳纳米管/聚乳酸复合材料.采用红外吸收光谱、偏光显微镜、扫描电镜及拉伸实验研究了SDBS修饰的碳纳米管表面形貌和结构以及碳纳米管/聚乳酸复合材料的链结构、聚集态结构和力学性能.SDBS修饰可使碳纳米管均匀分散于有机溶剂中,并改善...     

汽车缸套表面磁场辅助电沉积Ni-SiC纳米复合镀层研究

在汽车缸套表面使用磁场辅助电沉积法制备Ni-SiC纳米复合镀层。利用扫描电镜(SEM)、原子力显微镜(AFM)、透射电镜(TEM)及X射线衍射仪(XRD)对Ni-SiC纳米复合镀层的表面结构及成分进行研究。当镀液中SiC含量为6 g/L时,SiC纳米粒子团聚倾向最小,Ni-SiC纳米复合镀层表面平整、紧密。当SiC纳米颗粒含量为6 g/L时,Ni-SiC纳米复合镀层表面颗粒粒径进一步减小,并均匀分布于镀层表面。XRD分析可知,在汽车缸套表面镀层中存在Ni晶粒和SiC粒子。当镀液中SiC纳米颗粒含量为6 g/L时,Ni-SiC镀层中Ni晶粒和SiC粒子的平均晶粒尺寸分别为50.62 nm和39.32 nm。     

(Ni/SiC)P为第二相粒子的复合镀层研究

为增加(SiC)P与金属基体间的润湿性,采用化学镀方法对(SiC)P进行了低成本的表面涂覆改性,得到全包覆的改性(Ni/SiC)P,以其为第二相粒子制备出Ni-P-(Ni/SiC)P化学复合镀层,观测了该镀层的形貌、成分及厚度,并与常见的Ni-P化学镀层、Ni-P-(SiC)P化学复合镀层比较。结果显示:Ni-P-(Ni/SiC)P镀层组织均匀、沉积量大,镀层厚度明显增加。     

Improvement of the tool life of a micro-end mill using nano-sized SiC/Ni electroplating method

High mechanical properties of a tungsten carbide micro-end-mill tool was achieved by extending its tool life by electroplating nano-sized SiC particles (< 100 nm) that had a hardness similar to diamond in a nickel-based material. The co-electroplating method on the surface of the micro-end-mill tool was applied using SiC particles and Ni particles. Organic additives (saccharin and ammonium chloride) were added in a Watts bath to improve the nickel matrix density in the electroplating bath and to smooth the surface of the co-electroplating. The morphology of the coated nano-sized SiC particles and the composition were measured using Scanning Electron Microscope and Energy Dispersive Spectrometer. As the Ni/SiC co-electroplating layer was applied, the hardness and friction coefficient improved by 50%. Nano-sized SiC particles with 7 wt% were deposited on the surface of the micro-end mill while the Ni matrix was smoothed by adding organic additives. The tool life of the Ni/SiC co-electroplating coating on the micro-end mill was at least 25% longer than that of the existing micro-end mills without Ni/SiC co-electroplating. Thus, nano-sized SiC/Ni coating by electroplating significantly improves the mechanical properties of tungsten carbide micro-end mills.     

纳米SiC-MoS2/Ni基复合电刷镀层组织与耐磨性能

通过对纳米SiC颗粒进行表面修饰处理,采用电刷镀技术制备纳米SiC-MoS2/Ni基复合刷镀层,分析探讨了纳米SiC和MoS2的含量对镀层形貌和耐磨性能的影响。结果表明,镀液中加入经表面修饰的纳米SiC颗粒可以提高镀层硬度,同时在干滑动磨损试验条件下,纳米SiC-MoS2复合刷镀层具有良好的耐磨减摩性能。     

Brazing of SiC to a wrought nickel-based superalloy using CoFeNi(Si, B)CrTi filler metal

Newly-developed CoFeNi(Si, B)CrTi brazing filler metal was used for joining of SiC to a wrought nickel-based superalloy (GH3044). The brazing alloy was fabricated into brazing foils by a rapid solidifying technique, and the brazing temperature was fixed at 1150 °C. The SiC/GH3044 joints using single interlayer Ni or triple interlayers of Ni/W/Ni showed very low strength, and this was because the Ni severely interfered with the normal reactions between the SiC and the brazing alloy. When using triple interlayers of Kovar/W/Ni for the SiC/GH3044 joining, the joint strength was remarkably elevated to 62.5-64.6 MPa. Kovar has a low coefficient of thermal expansion. Moreover, when Kovar was used as an interlayer neighboured to the brazed SiC, it basically ensured the normal interfacial reactions between the brazed SiC and the used brazing alloy. These two factors should account for the improvement of the joint strength.     

化学镀Ni-P-SiC镀层的微观组织结构特征

对化学镀Ni-P-SiC复合镀层的微观组织结构特征进行了研究，结果表明，SiC微粒弥散分布在复合镀层中，Ni-P合金主要作为粘结金属包络着SiC微粒，两之间存在电子转移，发生了界面反应，反应扩散层为10^-1nm级，界面结合紧密，无孔隙和裂纹等缺陷。元素存在形态主要表现为Ni和P以单质的形式存在，Si以共价健SiC的形式存在，Ni－Ni之间以金属键进行结合。     

SiC颗粒表面金属化工艺及显微组织分析

为改善碳化硅颗粒与金属的润湿性,本文研究了在碳化硅颗粒表面金属化即沉积Ni-P层的工艺方法.首先采用表面清洁处理,继而采用粗化和活化敏化工艺对平均尺寸为5μm的Si C颗粒进行预处理,实现了在化学镀镍前在碳化硅表面产生微小的缺陷,并吸附Pd作为催化活性物质,为后序化学镀过程Ni-P的吸附、形核、长大提供了有利条件.利用正交试验方法,结合增重百分率和镍元素的相对含量等指标,研究了化学镀液的成分对镀层组织及形貌的影响.研究发现,当化学镀液中[Ni~(2+)]浓度为0.25 mol/L、[NH_4~+]浓度为0.6 mol/L,[Ni~(2+)]/[H_2PO_2~-]浓度之比为0.4、柠檬酸浓度为0.1 mol/L及pH为10,温度为45℃时,SiC颗粒表面完全包覆Ni-P.通过比较实验可知,预处理中活化敏化过程对后续Ni-P合金的包覆有重要促进作用.同时,化学镀液各成分中对施镀效果的影响顺序为:溶液中[Ni~(2+)]浓度pH柠檬酸三钠的含量温度[Ni~(2+)]/[H_2PO_2~-]浓度之比[NH_4~+]浓度.     

SiCP/AZ80镁基复合材料的界面与断口特征

本文用SEM,TEM研究了SiC颗粒增强AZ80镁合金复合材料的界面结构和断口形貌。结果表明,SiC颗粒与镁合金界面结合紧密,没有发生界面化学反应,但在界面处可以观察到Mg₁₇Al₁₂共晶相在SiC表面形核生长。对复合材料断口观察表明,SiC颗粒与镁合金界面之间的粘结强度大于基体的撕裂强度,SiC颗粒的聚集、团聚是导致复合材料断裂的主要原因,且复合材料的断裂形式趋向脆性断裂。     

回火温度对Ni-P基化学镀层显微硬度和耐蚀性的影响

研究了回火温度对Ni P基化学镀层显微硬度和耐蚀性的影响。结果表明 ,Ni P、Ni Co P、Ni Co P SiC 3种镀层的硬度随着回火温度的升高总体上呈上升趋势 ,并在一定温度范围内出现了硬度峰值 ;3种镀层的腐蚀率随回火温度的升高而增大 ,在 40 0℃时达到最大值     

Microstructure and mechanical properties of diffusion bonded SiC/steel joint using W/Ni interlayer

This paper describes the design and examination of W/Ni double interlayer to produce a joint between SiC and ferritic stainless steel. Diffusion bonding was performed by a two steps solid state diffusion bonding process. Microstructural examination and mechanical properties evaluation of the joints show that bonding of SiC to steel was successful. EDS and XRD analysis revealed that W₅Si₃ and WC were formed at SiC/W interface. The diffusion products at W/Ni interface, Ni-rich solid solution Ni(W) or intermetallic compound Ni₄W, was found to be dependent on the second step joining temperature. Neither intermediate phases nor reaction products was observed at Ni/steel interface for the joints bonded at the temperature studied. The average tensile strength of 55 MPa which is insensitive to the second step process was measured for as-bonded SiC/steel joint and the failure occurred at SiC/W interface. The hardness near the various bonded interfaces was also evaluated.