硅粉表面改性及其分散效果评价

目的降低原状工业硅粉颗粒的团聚现象和聚集效应,提高其分散性,改善掺硅粉水泥基材料的力学及界面过渡区性能。方法采用表面化学修饰和机械分散两种改性方法,对硅粉进行表面改性。利用表面电位测试、紫外光谱分析、激光粒度分析、扫描电镜测试等试验手段,评价了改性前后硅粉颗粒的表面电位和减水剂分子吸附量、颗粒粒度分布,以及硅粉颗粒和硬化硅粉-水泥净浆的微观形貌。采用棱柱体试件,研究了改性硅粉对水泥-硅粉净浆抗折与抗压强度的影响。结果用氨丙基三乙氧基硅烷及磁力搅拌工艺对原状工业硅粉进行表面改性后,硅粉表面电位由-21 m V变为+3 m V,高性能聚羧酸减水剂吸附量提高了60%,硅粉中纳米级微细颗粒数量显著增加,大颗粒团聚现象明显降低,硅粉颗粒的分散性明显改善;改性硅粉使水泥-硅粉净浆的力学性能提高了11%~24%。结论采用氨基硅烷和磁力搅拌工艺对原状硅粉表面改性后,硅粉表面的电位由负值变为正值,减水剂吸附量显著增大,颗粒团聚性降低,纳米级颗粒数量增多,在水泥中分散性改善,水泥-硅粉水化产物的界面过渡区性能改善,掺硅粉水泥浆体的力学性能明显提高。     

活性元素对C/NiAl复合材料界面润湿及浸渗组织的影响

采用座滴法研究了真空、1800℃下NiAl在碳、TiC、SiC和ZrC上的润湿性,并通过铺展实验和熔渗实验优化了NiAl改性C/C复合材料的活性添加元素及添加量。采用真空熔渗法制备NiAl改性C/C复合材料,采用X射线衍射仪和扫描电镜分析了复合材料的微观结构和渗透机制。结果表明,NiAl与C或SiC的润湿性较差,与TiC或ZrC的润湿性很好;添加Ti能改善NiAl和C的润湿性,Ti粉含量为15%(质量分数)时,C/C复合材料熔渗NiAl的效果最佳,NiAl渗透层的厚度为0.8~0.9 mm;添加Ti利于C/C复合材料渗NiAl的主要原因是Ti与C反应形成TiC,改善了NiAl在C/C复合材料中的化学吸附和物理吸附特性,NiAl通过毛细管力作用渗入到C/C复合材料坯体中。     

表面改性纳米纤维素/羟基磷灰石纳米复合材料的制备与性能研究

目的 制备羟丙基纳米纤维素/羟基磷灰石(NCC-HPC/HA)纳米复合材料.方法 以环氧丙烷作为改性剂,对纳米纤维素(NCC)表面进行化学修饰,获得羟丙基纳米纤维素(NCC-HPC),以提高NCC的表面疏水性及改善其分散性.在此基础上,以NCC-HPC为成核点,采用共沉淀法制备NCC-HPC/HA纳米复合材料,研究复合材料的结构与性能.结果 采用共沉淀法在改性后的纳米纤维素表面成功地合成了羟基磷灰石纳米球.由分析证实,经环氧丙烷表面改性后的NCC,几乎没有发生晶体结构变化,疏水性得到了提高,再分散性得到了改善,且能稳定存在于水和其他有机溶剂体系中,NCC-HPC与水的接触角由17°增加到55.3°.NCC-HPC/HA纳米复合材料的表面均匀分布着钙、磷元素,其Ca/P原子比为1.64,接近真实骨的钙磷比.在2 MPa条件下压制的复合材料的力学性能显示,与未经表面修饰的NCC相比,经表面修饰的纳米纤维素制备的NCC-HPC/HA纳米复合材料的力学性能有所提升.拉伸强度可达到3.48 MPa,提高了6.7％;弯曲强度可达到5.22 MPa,提高了4.4％;压缩强度可达到2.11 MPa,提高了4.7％.结论 经羟丙基改性的NCC,疏水性得到提高,在水溶液中的分散性明显改善.以此为基础制备的NCC-HPC/HA纳米复合材料中,球状纳米羟基磷灰石(n-HA)均匀分布在线状NCC-HPC上,具有较好的力学性能和热稳定性,适用于骨组织工程应用.     

ZnO/TiO_2-纳米管光催化剂的制备与表征

采用改进的化学沉积法,用ZnO对TiO2-纳米管进行改性,制备ZnO/TiO2-纳米管的复合半导体材料。用X射线衍射仪、透射电镜、高分辨透射电镜、X射线能谱仪、比表面分析仪,紫外-可见光度计等研究样品的结构、表面形貌和化学组成。通过光降解甲基橙模拟污染物考察其光催化性能,并探讨ZnO粒子表面修饰增强TiO2-纳米管光催化活性的机制。结果表明:n(Zn)-n(Ti)为1-4的ZnO/TiO2-纳米管复合材料具有最佳的光催化活性;Zn和Ti的协同效应改善了复合材料的可见光响应性。     

氮化铝基导热复合材料的制备及性能

以AlN角形粉和AlN球形粉为填料,以PDMS为有机基体,制备不同固含量的导热复合材料,研究了AlN形态、AlN填充分数及粉体表面改性等对导热复合材料粘度及热导率的影响。研究结果表明,与角形AlN粉体相比,球形AlN粉体可显著降低复合材料的粘度,因而有利于获得更高的填充分数和更大的复合热导率。利用KH570对AlN粉体进行表面改性,有利于降低界面热阻,提高复合热导率,改性浓度(质量分数)为2.0%时,复合材料热导率可提高22.5%。     

氮化铝基导热复合材料的制备及性能

以AlN角形粉和AlN球形粉为填料,以PDMS为有机基体,制备不同固含量的导热复合材料,研究了AlN形态、AlN填充分数及粉体表面改性等对导热复合材料粘度及热导率的影响。研究结果表明,与角形AlN粉体相比,球形AlN粉体可显著降低复合材料的粘度,因而有利于获得更高的填充分数和更大的复合热导率。利用KH570对AlN粉体进行表面改性,有利于降低界面热阻,提高复合热导率,改性浓度(质量分数)为2.0%时,复合材料热导率可提高22.5%。     

硅烷对紫外线辐射下木粉/聚偏氟乙烯复合材料的影响（英文）

木粉表面分别经乙烯基三乙氧基硅烷(A151)、γ-氨丙基三乙氧基硅烷(KH550)、三氟丙基三甲氧基硅烷(TF3)和1H,1H,2H,2H-全氟癸基三甲氧基硅烷(TF17)修饰后,与聚偏氟乙烯(PVDF)熔融共混并挤出制备木塑复合材料(WPCs)。对暴露于紫外线辐照前后的复合材料进行力学测试、动态机械分析(DMA)和差示扫描量热分析(DSC)。结果表明,含有40 wt%TF3改性木粉的复合材料的抗弯曲和抗冲击性能得到显著提升,该复合材料在紫外线辐照条件下难以变联。TF17通过氟硅烷与PVDF之间产生的共价键使得复合材料暴露于紫外线辐照下容易交联。硅烷修饰填料表面可以改善填料粒子分散在聚合物基体中,但会阻断聚合物包埋于木材的毛细管中,这样能增加非晶态聚合物相的移动和降低木粉/聚偏氟乙烯复合材料的玻璃化转变温度(T_g)。暴露于紫外线辐照过程中,同时发生在复合材料固态非晶相和结晶相的交联和断链反应是相互竞争的。当非晶态相的反应占主导地位时,分子链重排和形成新的晶体,复合材料的熔融焓(AH_f)和结晶度(X_e)增加。     

CuxSiy改性C/C-SiC复合材料的制备及其性能

以针刺整体炭毡为预制体,采用化学气相渗透法(CVI)增密制备C/C多孔体,然后采用反应熔体浸渗法(RMI),将Cu与Si同时熔渗进C/C坯体中制备CuxSiy改性C/C-SiC复合材料.研究CuxSiy改性C/C-SiC复合材料的组织结构、力学性能和摩擦磨损性能,并与C/C-SiC复合材料进行对比.结果表明:CuxSiy改性C/C-SiC复合材料的弯曲强度和冲击韧性略低于C/C-SiC复合材料的;采用30Cr钢作对偶时,CuxSiy改性C/C-SiC复合材料的摩擦因数约为0.24,线磨损率小于4 μm·side-1·cycle-1,均与C/C-SiC复合材料的相近,但其摩擦表面温度降低约50 ℃;以自身材料作对偶时,CuxSiy改性C/C-SiC复合材料的摩擦磨损性能略低于C/C-SiC复合材料的.     

B、Si改性炭/炭复合材料及其摩擦磨损特性

以低密度的C/C复合坯体为预制体,分别采用反应熔渗(RMI)、化学气相沉积(CVD)、浸渍-原位反应技术对其进行陶瓷改性.结果表明:改性陶瓷分别以SiC和c-BN的形式渗入C/C复合坯体内.摩擦试验结果表明:采用RMI技术制备的C/C-SiC复合材料摩擦因数较高,高达0.3到0.9;采用CVD技术制备的C/C-SiC复合材料的摩擦因数在0.20～0.36之间;而采用浸渍-原位反应技术制备的c-BN改性C/C复合材料的摩擦因数较低,为0.10～0.20.SEM观察表明:采用RMI技术制备的C/C复合材料的摩擦表面粗糙、未形成完整的摩擦膜,而采用另两种技术制备的C/C复合材料均形成了较完整、致密的摩擦膜.     

纳米氧化铝掺杂酚醛/环氧聚合物基复合材料的制备及耐磨性能

目的 提高环氧树脂的耐磨性并改善其力学性能,探究纳米氧化铝掺杂酚醛/环氧复合材料的摩擦磨损行为并揭示其减摩耐磨机制。方法 以酚醛树脂(PF)改性环氧树脂(EP)为聚合物基体,将改性的纳米氧化铝(Nano-Al₂O₃)掺杂其中,制备不同配比的Nano-Al₂O₃掺杂PF/EP聚合物基复合材料。利用红外光谱仪(FTIR)对复合材料进行化学结构表征。通过泰伯磨损试验和硬度分析,对比不同含量Nano-Al₂O₃掺杂对PF/EP基复合材料耐磨性能的影响。借助扫描电镜(SEM)分析复合材料的断面形貌和磨损表面,探究复合材料的磨损机理和减摩耐磨机制。结果 FTIR测定证实了硅烷成功改性Nano-Al₂O₃,并参与到PF与EP的固化反应中。硬度分析及磨损试验表明,硅烷改性Nano-Al₂O₃和PF的加入都提高了复合材料的硬度和耐磨性。与纯EP相比,酚醛质量分数为30%,掺杂3%Nano...     

Fractography, fluidity, and tensile properties of aluminum/hematite particulate composites

This paper examines the effect of hematite (iron oxide) particles on the fluidity of the molten composite as well as the tensile properties and fracture behavior of the solidified as-cast aluminum composites. The percentage of hematite in the composite was varied from 1 to 7% in steps of 2% by weight. The vortex method was employed to prepare the composites. It followed from the results obtained that the ultimate tensile strength and Young’s modulus of the composite increased while the liquid fluidity and solid ductility decreased with the increase in hematite content in the composite specimens. The fluidity of the liquid was greater in a metal mold than in a sand mold, and it decreased with an increase in reinforcing particle size and increased with pouring temperature. The presence of the reinforcing particles altered the fracture behavior of the solid composites considerably. Final fracture of the composite occurred due to the propagation of cracks through the matrix between the reinforcing particles.     

铸造ZL101A／SiCp复合材料的研究

采用真空搅拌复合工艺制备了铸造ZL101A／SiC复合材料,研究了变质和细化处理对复合材料组织的影响。结果表明：变质和细化处理铸造 ZL101A／SiC复合材料制备工艺的重要处理措施,可明显改善复合材料的组织。利用透射电镜对AL／SiC界面特征及界面反应进行分析,同时对该复合材料的铸造性能（熔体合金流动性能、线收缩、体收缩和热裂倾向）以及力学和物理性能进行了测试。     

Fabrication of ultrahigh density ZnO-Al_2O_3 ceramic composites by slip casting

The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites.The Zeta potential of raw powders was measured.ZnO and Al2O3 powders have lower Zeta potential than-45 mV commonly at pH 8-10.3 with polyacrylic acid(PAA)added.The influence of pH and the mass fraction of the additives on the stability and fluidity of the suspensions added with PAA and polyethylene glycol(PEG) was investigated by experiments of viscosity and sedimentation.The suspensions have the lowest viscosity and the best stability at pH 9 with 0.2%PAA(mass fraction).The maximum density of green compacts is 66.6%of theoretical density(TD)with compacting and homogeneous green particles.An ultrahigh density sintered compact(99.6%TD)could be obtained after pressureless sintering at 1 400℃for 2 h.     

SiCp/A357复合材料流动性数值模拟与实验研究

搅拌铸造方法易于成型大尺寸复杂的复合材料零件,但是碳化硅颗粒加入使得复合材料的流动行为变得更加复杂,开展复合材料流动性研究至关重要。本文建立了SiCp/A357复合材料的流动模型,采用数值模拟及实验研究相结合的方法,研究了浇注温度及碳化硅体积分数对SiCp/A357复合材料流动性及流动充型过程碳化硅分布的影响。结果表明,随着浇注温度的提高SiCp/A357复合材料的流动性升高,这一趋势在半固态区间更为明显;但是随着浇注温度的提高,试样前端的碳化硅体积分数较末端减少加剧,复合材料中碳化硅的整体分布均匀性降低;随着碳化硅体积分数的增加SiCp/A357复合材料的流动性降低,且随着碳化硅体积分数的增加,试样前端碳化硅的体积分数减少程度减弱,整体的均匀性提高。上述的模拟结果与实验结果具有较好的一致性。     

Si及变质处理对Mg2Si/Mg复合材料的影响

分析了Mg-Si二元合金直接原位形成Mg2Si/Mg复合材料的过程,研究了Si含量以及变质处理对复合材料组织和性能的影响。试验结果表明,随着合金中Si含量的增加,合金的流动性降低,复合材料中原位Mg2Si的数量增多,树枝晶形态更为发达;对优化的Mg-8Si合金,进行混合稀土(MM)和Sb变质处理,可明显改善Mg2Si的形态和分布,但Sb变质的效果要好于MM。合金经质量分数为1.2%的Sb变质处理后,Mg2Si以颗粒状均匀分布在Mg基体中,从而使复合材料具有较好的耐磨性。     

A catalytic oxidation approach to coat copper powder with polyaniline

To improve the oxidation resistance of fine copper powder, a new catalytic oxidation method was used to coat copper microparticles with polyaniline. In the method, some copper on the surface of copper particles was converted into Cu²⁺, and with the catalysis of Cu²⁺ aniline was oxidized by hydrogen peroxide to form the polyaniline coating layer on copper particles. Detected by field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), it is proved that the composite particles have fine core-shell structure, their core are copper particles and their shell are mainly composed of compact polyaniline. The stability of the composites was tested by Thermogravimetric Analyzer (TGA) in nitrogen and in air. It is found that the particulate composite is more stable than copper particles in air.     

Microstructure and properties of mechanical alloying particles reinforced aluminum matrix composites prepared by semisolid stirring pouring method

Aluminum matrix composites reinforced with mechanical alloying particles(SiC_p) were fabricated by the semisolid stirring pouring method. The inf luence of mechanical alloying particles and Mg on the microstructure and mechanical properties of the composites was investigated by means of optical microscopy(OM), X-ray diffraction scanning(XRD), electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Results show that the addition of Mg converts the agglomerate mechanical al oying particles in ZL101 matrix composites into dispersed distribution in ZL101-Mg matrix composites, large matrix grains into f ine equiaxed matrix grains, and eutectic phase into f ine particles. So the mechanical properties of ZL101-Mg matrix composites are better than those of ZL101 matrix composites. The mechanical properties of ZL101/ZL101-Mg matrix composites are gradually increased with the increase of the volume fraction of mechanical alloying particles. When the volume fraction of mechanical alloying particles is 3%, the Vickers hardness and ultimate tensile strength of the ZL101/ZL101-Mg matrix composites reach their maximum values.     

Colloidal and thermal stability of polyaniline-coated multi-core shell polystyrene latexes prepared using sulfonated N-hydroxyethyl aniline

Conductive polymer particles, poly(sulfonated N-hydroxyethyl aniline, SHEA)–polyaniline–poly(SHEA)–polystyrene (PSHEA–PANI–PSHEA–PSt) multi-core shell composite particles, were synthesized by chemical oxidation polymerization and an effect of poly(SHEA) on the colloidal and thermal stability enhancement was investigated. The PSHEA–PANI–PSHEA–PSt particles showed spherical shape and nearly monodisperse particle size distribution. Elemental analysis, UV–vis spectra, and Raman spectra revealed that polyaniline (PANI) was successfully coated onto the poly(SHEA) modified polystyrene particles. Conductivity of the PSHEA–PANI–PSHEA–PSt particle was higher than that of PANI–PSt particle after annealing at elevated temperature due to the non-volatile properties of poly(SHEA) as a co-dopant compared with inorganic dopants such as HCl. XPS analysis unveiled that the PANI in the PSHEA–PANI–PSHEA–PSt particle was co-doped by sulfonic acid in poly(SHEA), which increased conductive thermal stability of the particles.     

Fluidity of Al–Si semisolid slurries during rheocasting by a novel process

Lower fluidity of semisolid metallic slurries considerably limits their mold filling ability in rheocasting processes. In this paper, rheo-centrifuged casting (RCC) process was introduced and its performance was evaluated in terms of casting fluidity. Slurries were continuously cooled and stirred until reaching the desired fraction liquids up on which they were poured into a rotating sand mold. It was found that fluidity of Al–7.1 wt% Si semisolid slurry increased approximately linearly with the square of the initial fraction liquid. Casting fluidity also showed a relationship in the form of exp(nr) with section thickness of the channel (r). The exponent n appeared to be a function of the external force (centrifugal force) and was independent of fraction liquid. Casting fluidity was also found to increase with slurry stirring speed due to lower flow resistance resulted from smaller and more rounded primary particles formed. Some degree of liquid segregation was observed along the length of the mold channels which was more severe for smaller casting cross sections. In summary, RCC process was proved as a viable method for improving the casting fluidity of the alloy.     

Microstructure and mechanical properties of AZ31 magnesium alloy reinforced by I-phase

The particles of Mg-Zn-Gd icosahedral quasicrystal master alloy were added into the AZ31 alloy by the repeated plastic working(RPW)process in order to improve the mechanical properties of the AZ31 alloy at room temperature.The microstructure and tensile properties of composites were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile testing machine at room temperature.The results suggest that the RPW process can effectively refine the matrix and make the I-phase particles distribute uniformly.The ultimate tensile strength and the yield strength of the composites reach their maximum values of 362.3 and 330.5 MPa,respectively,when the amount of I-phase particles added is10 %.Meanwhile,the elongation of the composites decreases sharply.