核壳型HMX@TATB复合炸药造型粉制备技术研究

核壳型HMX@TATB复合炸药不仅能够显著降低HMX炸药的感度,还能有效保持HMX的高能量密度水平,在未来钝感弹药和安全型高能推进剂领域展现了较好的应用前景,而核壳型HMX@TATB复合炸药基PBX的制备研究对其相关性能测试和后期应用研究起重要作用。本研究探索了核壳型HMX@TATB复合炸药为基PBX造型粉制备过程中的转速、温度和粘结剂的滴加速度等工艺参数对造粒包覆的影响,得到了稳定的百克级核壳型HMX@TATB为基PBX造型粉的造粒工艺。     

核壳结构Ni—Fe/Al复合粉在HTPE固体推进剂中的应用研究

采用EDS(能量色散光谱)方法分析了核壳结构Ni—Fe/Al复合粉和普通Al粉在微观结构上的区别:Al粉完全被纳米Ni、Fe粉包裹,呈现出明显的核—壳结构,改善了Al粉的抗氧化性能。用该核壳结构Al粉完全替代普通Al粉应用于HTPE(嵌段端羟基共聚醚)推进剂中,研究了推进剂的工艺性能、力学性能和燃烧性能。结果表明,Ni、Fe包覆核壳结构Al粉有助于降低HTPE推进剂的压强指数,且能有效提高HTPE推进剂的燃烧效率和比冲,在金属燃烧剂领域中有广泛的潜在应用前景。     

核壳型二氧化钛复合纳米材料研究进展

核壳材料由中心核和外部壳层组成，因其组成、大小、结构的不同，性能优于普通材料。二氧化钛具有优异的光、电和化学等特性可作为理想的核壳材料。从二氧化钛作为核壳型复合纳米材料的核、壳及核壳结构的载体3个方面出发，介绍了核壳型结构的二氧化钛复合纳米材料的分类、制备、性质及应用概况，并对其发展前景及存在问题进行了简要概述。     

核壳结构聚合物复合粒子的合成与表征

过去几十年,由于核壳结构聚合物复合粒子在合成聚合物材料的抗冲改性和增韧、涂料、粘合剂等诸多领域的成功应用而备受关注。本文综述了核壳结构聚合物复合粒子的制备方法,从热力学和动力学２ 个方面探讨了形成核壳结构聚合物复合粒子的条件,介绍了该类粒子的表征方法。     

核壳型纳米SiO2-聚丙烯酸酯复合乳液的制备及应用

本文根据核壳乳液聚合理论,以硅烷偶联剂表面处理的纳米S iO2为种子,采用优化的乳液聚合工艺,制备核壳型纳米S iO2-聚丙烯酸酯复合乳液,并以其为基料制备建筑涂料。实验结果表明,纳米S iO2经硅烷偶联剂表面处理后,提高了其在聚合体系中的分散稳定性和与聚合物的相容性。所制备的复合乳液粒子具有核壳结构,以其为基料制备的建筑涂料的耐沾污性、耐洗刷性和耐候性等性能大大高于国家标准中优等品的水平。     

PMMA/PAN核壳复合粒子的制备与表征

用无皂乳液聚合法制备粒径分布较窄的单分散聚甲基丙烯酸甲酯(PMMA)乳液粒子后,以此乳液粒子为种子,以丙烯腈为壳层单体,用种子乳液聚合法制备了粒径分布更窄、具有核壳结构形态的PMMA／聚丙烯腈(PAN)复合粒子,测定了核及核壳粒子粒径及其分布,并用透射电镜表征了其核壳形态特征。结果表明,PMMA／PAN核壳粒子的壳层厚度约为20nm,粒径分布要比PMMA粒子的窄。     

核壳结构复合粒子对聚丙烯流变性能的影响

采用乳液聚合方法,分别以甲基丙烯酸甲酯(MMA)、苯乙烯(ST)为壳,以高岭土为核制备具有核壳结构的共聚物。将制得的两种核壳结构复合粒子添加到聚丙烯(PP)中,对PP进行改性。结果表明:共混体系为非牛顿假塑性流体,其表观黏度随剪切速率的增大而减小;共混物非牛顿流动指数下降,剪切速率上升,流变性能改善;加入核壳结构复合粒子后,共混物黏流活化能增大,从而黏温依赖性增大。     

金包覆的核壳结构纳米材料的制备进展

金、银等贵金属纳米材料具有独特的光学、电学和催化性能以及良好的生物兼容性,其在化学、物理、生物和医学等领域具有广泛的应用。以贵金属纳米金作为核或壳,制备成核壳结构复合纳米材料,这样的核壳材料同时具有核和壳的性质以及其他优越的性能,因此受到研究者的广泛青睐。金包覆纳米颗粒制备核壳结构的方法众多,主要对金包覆所形成的核壳型纳米材料的制备方法进行综述。     

Fe_2O_3/TiO_2核壳结构纳米粒子的制备和表征

采用液相沉淀法制备具有核壳结构的Fe2O3/TiO2纳米复合颗粒。研究了用硫酸亚铁水解制备纳米氧化铁,再以TiCl4为前驱物,以乙醇、尿素、硫酸胺为介质在氧化铁表面合成具有核壳结构的Fe2O3/TiO2纳米复合颗粒的方法。用XRD,TEM,EDS对样品进行表征。讨论了其形成机理。     

硅溶胶/聚丙烯酸酯复合乳液的结构和性能研究

采用普通乳液聚合的方法,制备了硅溶胶/聚丙烯酸酯复合乳液.通过透射电镜(TEM)、傅里叶红外光谱仪(FT-IR)和动态激光散射仪(DLS)等对复合乳液中乳胶粒子的结构进行表征,并对复合乳液的涂膜性能进行研究.结果表明,所制备的复合乳液粒子具有核-壳结构,其中核是纳米级的SiO2粒子,壳是聚丙烯酸酯.性能测试结果表明,核-壳结构的存在使得复合乳液的涂膜在硬度、附着力和化学稳定性等方面均优于纯丙乳液及硅溶胶/聚丙烯酸酯的共混乳液.     

含超细高氯酸铵核-壳型复合材料的制备

用超临界流体沉积技术中的SAS法制备了超细HMX,AP,CL-20以及Al—FPM2602核-壳型复合材料。通过氟橡胶FPM2602在超细HMX,AP,CL-20和Al混合物表面的沉积,达到对混合物进行包覆改性的目的。吸湿性试验表明,该核壳型复合材料的抗湿能力得到明显提高。对该超细核壳型复合材料进行了撞击感度、火焰感度、爆发点测试。结果表明,与未包覆的混合物相比,该超细核-壳型复合材料的性能有了一定的提高。超临界流体沉积技术中的SAS法是制备含水溶性超细含能复合材料的绿色环保方法。     

Synthesis and characterization of carbon-encapsulated iron/iron carbide nanoparticles by a detonation method

Carbon-encapsulated iron-based nanoparticles with a core-shell structure were produced by detonation decomposition of explosive mixture precursors containing iron ion components. The size and magnetic properties of the as-prepared composite particles were revealed by X-ray powder diffraction, transmission electron microscopy and magnetic measurements. Results showed that the different sizes of the iron-based nanocrystal core and the thickness of the carbon shell could be yielded by adjusting the component materials of the explosive precursors during the course of these detonation chemical reactions. The composite particles had a body-centered cubic iron or iron carbide core with a coating of graphitic or amorphous carbon layers. Magnetic measurements indicated these composite nanoparticles were magnetic at the room temperature, with some variation in the values of saturation magnetization, remanences and coercive forces that depend on the size and grain composition.     

Fabrication of core-shell structured MWCNT-Ti(TiC) using a one-pot reaction from a mixture of TiCl3, TiH2, and MWCNTs

Multi-walled carbon nanotubes (MWCNTs) coated with metal titanium or carbide layers were prepared by heating a mixture of TiCl₃, TiH₂, and MWCNTs under vacuum. The resulting MWCNT-Ti(TiC) materials had a uniform and conformal core-shell structure. The thickness of the Ti(TiC) layer was determined by the deposition temperature and time. The amount of TiC in the shell depended primarily on the deposition temperature. Whether a metal or carbide coating was obtained was determined by controlling the deposition temperature. Ti(TiC)-coated MWCNTs showed better field emission properties than did pristine MWCNTs. This deposition method should prove to be a versatile route for fabricating other one-dimensional core-shell materials.     

Refractory filler sands with core-shell composite structure for the taphole nozzle in slide-gate system of steel ladles

Refractory sand used for filling the taphole nozzle in slide-gate system of steel ladle needs to form a suitable sintered crust to prevent molten metal from direct contact with the gate system which, when opened, permits flow of metal from the ladle through the taphole well. Conventional filler sand consists of powdered mixtures of at least two compositions with suitable particle size and mass ratio. We herein propose a novel core-shell-structured composite particle as the refractory sand. Silicon carbide (SiC) particles with an average diameter of 50 μm were oxidized in air at 1100-1600 °C to form SiC@SiO₂ core-shell structure. As the oxidation temperature increases, silica weight-ratio increases from 0.8 to 7.9 wt.%, equivalent to a calculated shell thickness of 20-157 nm, respectively. The crust thickness can be tailored by adjusting the shell thickness. X-ray photoelectron spectroscopy, X-ray diffractometry, and scanning electron microscopy were used to characterize the core-shell structure.     

PP/POE/BaSO4三元复合体系力学性能研究

采用两步法制备工艺,首先制备BaSO4填充(乙烯/辛烯)共聚物(POE)母料,再将母料与聚丙烯(PP)共混制得两种具有不同界面相互作用的PP/POE/BaSO4三元复合体系。研究表明,采用表面处理的BaSO4所制备的PP/POE/BaSO4三元复合体系呈核-壳结构;采用未经表面处理的BaSO4所制备的PP/POE/BaSO4三元复合体系为完全相分离结构;具有核-壳结构的三元复合体系的拉伸屈服强度、缺口冲击强度大于具有完全相分离结构的三元复合体系,但前者的弯曲弹性模量小于后者。     

Preparation and characterization of composite resin by vinyl chloride grafted onto poly(BA-EHA)/poly(MMA-St)

Crosslinked poly(butyl acrylate-co-2-ethylhexyl acrylate)/poly(methyl methacrylate-co-styrene) (ACR I) latex was synthesized by multi-stage emulsion polymerization. A series of grafting vinyl chloride (VC) composite latices were prepared by emulsion copolymerization in the presence of core-shell ACR I latex. The effects of ACR I amount and its core/shell ratio on particle diameters of the composite latices and mechanical properties of the prepared materials were investigated. The grafting efficiency (GE) of VC grafted onto ACR I increases with an increasing ACR I content. Transmission electron microscope (TEM) study indicates that ACR I latex particles have a regular core-shell structure obviously. However, when styrene content in the shell of ACR I is more than 70 percent of the shell by weight, ACR I latex particles have an irregular core-shell morphology like sandwich. The composite latex particles synthesized by core-shell ACR I latex grafting VC have a clear three-layered core-shell structure. Dynamic mechanical analysis (DMA) study reveals that the compatibility between ACR I and PVC is well improved. With increasing ACR I content, the loss peak in low temperature range for every composite sample becomes stronger and stronger and gradually shifts to a higher temperature. Scanning electron microscope (SEM) graphs showed that the fractured surface of the composite sample exhibited better toughness of the material. TEM graphs showed that ACR I was uniformly dispersed in the PVC matrix.     

PMMA/PAN核-壳粒子制备工艺研究

加入适量的引发剂,通过无皂乳液聚合,以聚甲基丙烯酸甲酯( PMMA)核体为种子乳液,制备了PMMA/PAN核-壳乳液.实验中分别对引发剂量、丙稀腈( AN)滴加量对PMMA/PAN壳层厚度及其粒径和粒径分布的影响进行了较详细的研究,确定了种子乳液聚合法制备PMMA/PAN核-壳结构聚合物粒子的实验方法及条件.通过激光粒度仪、扫描电镜和透射电镜对核-壳粒子的形态结构进行了表征,证明了PMMA/PAN复合粒子的核-壳结构.     

核壳型复合聚合物乳液合成工艺研究

以乳化单体加料的种子聚合技术,合成了聚丙烯酸乙酯/聚苯乙烯核壳型复合聚合物乳液.确定了种子聚合过程中乳化剂补加量与聚合单体量之间的定量关系和合理的单体加料速率.该体系所得聚台物乳液的乳胶粒是“翻转型”的核壳结构.     

Promoting in situ formation of core-shell structured carbides in high-Cr cast irons by boron addition

M₇C₃ carbide is an important reinforcing phase in high-Cr cast irons, ferrous alloys, metal-matrix composites, and hardfacing overlays. However, the mismatch at the carbide/matrix interface due to the differences in structure and mechanical strength between the carbide and metallic matrix may lower the resistance of the material to mechanical attack, such as wear, corresponding to increased risk of interfacial failure or the role of the interfacial mismatch as a stress raiser for crack initiation. Recent studies on high-Cr cast irons (HCCI; Fe-45%Cr-%C series) show that core(M₇C₃)-shell(M₂₃C₆) structured carbides (CSSCs) help minimize the misfit stress at the interface between carbide and matrix, thus enhancing their resistance to wear. However, such core-shell structured carbide does not always form. It is of importance to understand the mechanism responsible for the formation of CSSC for maximized benefits. In this study, we conducted thermodynamic analysis to investigate the conditions for in situ forming CSSCs in HCCIs and determine the probability of generating CSSCs through alloying elements. Both thermodynamic analysis and first-principles calculations demonstrate that the core-shell structured carbide can be in situ formed in HCCIs by alloying with elements such as boron, which increases the stability of M₂₃C₆ with lowered energy. Relevant experiments were performed to verify the theoretical analysis and prediction.