Electroless deposition of Ni on template of halloysite and its magnetic property

Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The electroless deposition of Ni is catalyzed by the Pd particles, which results in a uniform layer of Ni-P alloy on halloysite. The alloy is of a nanocrystalline structure, of which the average diameter is about 6 nm. After being heat-treated at 400 ℃, it contains both Ni and Ni12P5 crystal, meanwhile, the Ni crystal gets larger with an average size of 51.9 nm.The content of phosphorous in the Ni layer has a great influence on crystal structure. The metallized halloysite has a higher inherent coercive force, and a much lower saturation magnetization in its as-plated state, while after heattreatment, the inherent coercive force decreases drastically. These magnetic properties have great relationship with the superparamagnetism of Ni nanocrystalline and the stress anisotropy in Ni layer.     

埃洛石的结构特性、表面改性及应用研究进展

首先介绍了不同水合程度的埃洛石纳米管(HNTs)的内部分子结构和卷曲机制。其次,讨论了HNTs自身的阻燃性、表面吸附性和生物相容性等性能。重点综述了HNTs表面改性方法,如表面包覆改性、插层改性、表面活性剂改性等,以及HNTs表面改性后的应用。最后,对HNTs的研究前景进行了展望。     

缓蚀剂在埃洛石上的担载与释放规律研究

将粘土矿埃洛石经碱刻蚀改性,用SEM、FT-IR和BET手段对其进行表征,后作为载体与2-巯基苯并咪唑的乙醇和丙酮溶液担载制得复合体,用分光光度法研究了缓蚀剂与粘土矿埃洛石的担载和释放规律。结果表明碱刻蚀改性去除了埃洛石内表面的一部分氧化铝层,使埃洛石的比表面积和孔容增加8.66%、51.90%。在丙酮溶液中,缓蚀剂与埃洛石的担载量达到9%且该复合体在腐蚀介质中实现缓蚀剂的缓慢释放,2min可达到Q235钢的最高缓蚀效率所需的缓蚀剂质量浓度。该复合体可望用作防腐涂层中缓蚀剂缓释填料。     

Characterization and evaluating the mechanical performance of halloysite nanotubes reinforced acrylonitrile butadiene styrene/polycarbonate composites exposed to aggressive environmental conditions

Developing light weight polymer based composites dispersed with novel reinforcements which can function well in the presence of aggressive environments is an active research field in the materials engineering. Hence, in the current work, halloysite nanotubes (1 %, 2 %, 4 %, 6 %, 8 % and 10 % by weight) were reinforced into acrylonitrile butadiene styrene/polycarbonate blend and the role of reinforcing phases on the mechanical performance under aggressive environmental conditions has been evaluated. Hardness was measured as gradually increased in the composites with the increased content of the reinforcements. Impact strength of the composites was observed as increased in the composites up to 4 % reinforcement and further decreased. Increased strength was measured for the composite up to 2 % reinforcement. Ductility of the composites was decreased as reflected form the decreased % of elongation with the higher fraction of reinforcements due to induced brittleness. The composites were exposed to diluted sulfuric acid for 3 h and 6 h at 60 °C and then subjected to tensile loading. With the increased time of exposure, composites with 1 % and 2 % reinforcement exhibited relatively better performance.     

MCPA6/埃洛石纳米管复合材料性能研究

以氢氧化钠为催化剂,N–乙酰己内酰胺为活化剂,原位聚合制备MCPA6/埃洛石纳米管(MCPA6/HNT)复合材料,并利用凝胶渗透色谱、场发射扫描电子显微镜、差示扫描量热、热重分析和力学性能测试等方法研究HNT用量对复合材料结构和性能的影响。结果表明,HNT的引入使得PA6的分子量下降,分子量分布变宽;经硅烷偶联剂(KH–550)处理后的HNT能均匀分布在MCPA6中,且与基体具有较好的界面性能;HNT可以明显提高复合材料的结晶速率、结晶度以及分解温度;随着HNT含量增加,体系的拉伸强度和缺口冲击强度呈先增大后减小的趋势,而断裂伸长率逐渐下降,当HNT含量为1.5%时,MCPA6/HNT的综合力学性能最佳,拉伸强度和缺口冲击强度分别较MCPA6提高21.3%和14.9%。     

埃洛石纳米管／水性环氧树脂复合材料的性能

采用超声分散与机械搅拌混合方法制备了埃洛石纳米管(HNTs)/水性环氧树脂复合材料。通过TEM、SEM对HNTs及复合材料进行了表征,并分析了HNTs含量对水性环氧树脂乳液的流变行为、乳胶膜的热稳定性及涂膜性能的影响。结果表明:HNTs可在水性环氧树脂体系中均匀分散,使复合材料由脆性断裂转变为韧性断裂;但当w(HNTs)5%时,复合材料出现明显团聚,最佳添加量为w(HNTs)=2%,此时复合体系的热稳定性增强,热分解温度由358℃提高到365℃,剪切速率为10 s-1时,黏度由0.73 Pa·s增加到0.85 Pa·s;HNTs起到类交联点的作用;储能模量提高了8.1倍,内耗降低,复合体系呈现假塑性和明显的触变性,稳定性增强,水性环氧树脂乳胶膜的耐水性得到改善,与未添加HNTs的环氧树脂相比,当w(HNTs)=5%时,吸水率由27.8%降低到15.9%,涂膜的硬度由3H提高到4H,柔韧性由1 mm提高到0.5 mm。但当w(HNTs)5%时,体系结构与稳定性会被破坏,导致涂膜综合性能下降。     

Properties of phyllosilicate-based porous ceramics shaped by conventional tape casting and freeze tape casting

Silicate ceramics were shaped using tape casting (TC) and freeze tape casting (FTC) processes from three clays labeled HCR, KORS, and KCR. These clays exhibited mass content of 77% halloysite–10 Å, 29% kaolinite, and 98% kaolinite minerals, respectively. After casting the slurries, the dried tapes were sintered at 1200°C. The microstructure changes were characterized before and after sintering using scanning electron microscopy. The apparent porosity of TC samples was lower (36–47 vol.%) compared to values obtained with FTC samples (67–79 vol.%). The latter samples exhibited a highly textured porosity, with micron-sized pores aligned perpendicular to the tape surfaces. Upon sintering, the porosity of TC samples tended to decrease conversely to the case of FTC samples. Such behavior seemed related to the simultaneous effect of organic additives and ice templating. Consequently, the FTC samples showed a relatively low mechanical strength of 3–7 MPa and thermal conductivity of .14– .22 W m⁻¹ K⁻¹. After sintering, the mullite crystallization contributed to strengthen the bulk materials, helping to compensate for the detrimental effect of porosity on the stress to rupture and on thermal conductivity values.     

Inner surface modification of halloysite nanotubes and its influence on morphology and thermal properties of polystyrene/polyamide‐11 blends

The asymmetry of halloysite surface chemistry was used to perform a selective modification of its inner surface via grafting of a synthesized styrene/(methacryloyloxy)methyl phosphonic acid copolymer. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) and pyrolysis gas chromatography/mass spectrometry were used to evidence and quantify the grafting. Then, raw and hybrid nanoparticles were incorporated in polystyrene (PS)/polyamide‐11 (PA11) blends (80/20 and 60/40 wt%). Scanning electron micrographs showed differences in localization of the halloysite nanotubes (HNTs), since raw halloysite is concentrated in the PA11 phase while modified halloysite is also located at the PS/PA11 interface, leading to a better interfacial adhesion between PS and PA11. An inhibiting effect of modified halloysite on PA11 coalescence was evidenced by measuring the particle size distribution of the extracted nodules. Moreover, the presence of modified halloysite at the interface shows an improvement in terms of thermal stability as observed by TGA, but with no significant effects on PA11 crystallization behaviour as shown by differential scanning calorimetry results. Rheological measurements were carried out to study the influence of the surface modification of halloysite on the blend morphology. A gel‐like behaviour was observed for the (60/40 wt%) HNTs reinforced composition that was enhanced in the case of 10% functionalized halloysite. © 2016 Society of Chemical Industry     

埃洛石对水性超薄膨胀型钢结构防火涂料防火性能的影响

以聚丙烯酸酯乳液为基体树脂,多聚磷酸铵、三聚氰胺、季戊四醇等为主阻燃剂,埃洛石纳米管(HNTs)为阻燃协效剂,制备了水性超薄膨胀型钢结构防火涂料,采用模拟大板燃烧法和锥形量热仪对其耐火性能进行了研究,并用扫描电镜观察了膨胀炭层的表面形貌。结果表明:HNTs对防火涂料的耐火性能影响显著,当阻燃体系中HNTs含量为10.86%时,HNTs与主阻燃剂之间有阻燃增效作用,所制备防火涂料的耐火时间为107 min,点燃时间为24 s,热释放速率峰值与点燃时间比为4.97,燃烧残余量高达48.36%,且燃烧残余物表面致密,显示出优异的耐火性能。     

Polystyrene/Polyolefin Elastomer Blends Loaded with Halloysite Nanotubes: Morphological,Mechanical, and Gas Barrier Properties

Herein, a simple melt-blending method is utilized to disperse of halloysite nanotubes (HNTs) in polystyrene/polyolefin elastomer (PS/POE) blends. Based on morphological studies, the PS/POE/HNT nanocomposite containing up to 3 phr HNTs shows excellent nanofiller dispersion, while those filled with 5 phr HNTs exhibit nanofiller aggregation. To overcome the nanofiller aggregation issue, the polypropylene-grafted-maleic anhydride (PP-g-MA) compatibilizer is added to the PS/POE/HNT nanocomposite, which results in improved mechanical properties for the nanocomposite sheets. Furthermore, the addition of compatibilized HNTs to the PS/POE blends leads to decreased O₂ and N₂ gas permeabilities. Besides, incorporating POE, HNTs, and PP-g-MA leads to a decrease in water vapor transmission of PS. In the end, the experimentally-determined mechanical properties and gas permeabilities of the nanocomposite sheets are compared to those predicted by prevalent theoretical models, revealing a good agreement between the experimental and theoretical results. Molecular-dynamics simulations are also carried out to calculate the gas diffusion coefficients in the different sheets to further support the experimental findings in this study. Overall, the PS/POE/HNT/PP-g-MA nanocomposite sheets fabricated in this work demonstrate excellent mechanical and gas barrier properties; and hence, can be used as candidate packaging materials. However, the strength of the resulting PS/POE blend may be inferior to that of the virgin PS.