核壳结构复合吸波材料研究进展

在综述电磁波材料吸波工作原理的基础上, 讨论了核壳结构材料在吸波领域的优势.重点介绍了近年来不同类型核壳结构复合吸波材料的研究进展, 主要包括铁氧体型、磁性金属微粉及其氧化物型、陶瓷型、导电聚合物型、碳系材料型等核壳结构复合吸波材料.同时对不同类型的核壳结构吸波材料的制备方法、组织结构和微波吸收性能进行了详细的归纳评述.最后对核壳结构复合吸波材料的发展趋势进行了展望, 主要包括多层核壳结构, yolk-shell结构以及与其他材料结构相复合的特殊结构, 为进一步研究核壳结构复合吸波材料提供参考.      

碳包覆CdS纳米颗粒的光学性能研究

采用水热法制备了核壳结构的碳包覆CdS纳米颗粒(CdS@C),利用X射线衍射、高分辨透射电子显微镜和光谱仪研究了碳包覆层对CdS@C的微观结构与光学性能影响.结果表明,碳包覆CdS纳米颗粒具有明显的核壳结构,内核为六方纤锌矿结构CdS,外壳为碳层.颗粒形貌主要为球形或椭球形结构,粒度均匀,分散性良好,粒径分布在20～6...     

空心碳纳米球的可控制备

采用乙酰丙酮铜为原料,通过金属有机物化学气相沉积大批量制备C/Cu壳/核纳米颗粒,并通过反应气氛调控C壳层的厚度。将C/Cu壳/核纳米颗粒在1 300℃的真空环境中退火,获得空心碳纳米球。通过透射电子显微镜、X射线衍射仪、拉曼光谱等表征手段,对退火前和退火后的样品进行对比分析,发现退火前和退火后的碳壳层的直径、厚度和石墨化程度都没有明显改变,但是样品的比表面积增大了一个数量级。因此,通过C/Cu壳/核纳米颗粒的真空退火,是实现空心碳球可控制备的一条简易途径。     

专利信息

一种贵金属／酚醛树脂核壳结构生物相容性材料及其制法 发明人：俞书宏;郭仕锐 本发明公开了一种贵金属／酚醛树脂核壳结构生物相容性材料及其制备方法,其特征在于：先采用苯酚、六亚基四胺和贵金属的盐溶液在120～180℃条件下反应2～10小时;得到核壳结构颗粒;然后以该核壳结构颗粒作载体,采用合成磁性纳米Fe3O4的方法,在160～200℃温度反应下5～10小时,合成包括Fe3O4修饰的贵金属／酚醛树脂／     

福建物构所基于电子束刻蚀实现中空核壳结构稀土上转换纳米晶的原位构筑

正由于稀土上转换纳米晶具有将近红外光转换成短波长可见-紫外光的上转换发光特性,同时中空核壳结构纳米晶具有高比表面积及丰富可调的孔道结构等优点,中空核壳结构稀土上转换纳米晶在生物传感及成像、药物缓释和医学诊疗等方面具有广泛的应用前景。通过在稀土上转换纳米晶表面外延生长均匀包覆同质壳层通常被认为是减少原有纳米晶表面缺陷密度,从而提高上转换发光效率的一种有效策略。然而,对于同质包覆核壳结构上转换纳米晶核壳界面结构尤其是界面缺陷是否被显著抑制等基础问题尚缺乏深入的实验研究。中科院福建物质结构研究所功能纳米结构设计与组装重点     

化学气相沉积法制备核/壳结构Co/C纳米颗粒的结构与热稳定性

以乙酰丙酮钴为原料,采用单步金属有机物化学气相沉积法,在600~800℃温度下制备碳包覆钴的核/壳结构Co/C纳米颗粒。利用X射线衍射、透射电镜和Raman光谱仪等对合成产物的元素组成和结构进行表征,研究合成温度对产物形貌和结构的影响,分析Co/C核/壳纳米颗粒的形成机理,并通过差式扫描量热分析/热重分析研究产物的热稳定性。结果表明,不同反应温度下的产物中,Co核的粒径均在10~60 nm之间,C壳层的厚度在10~20 nm之间。随合成温度从600℃升至800℃,Co核由HCP和FCC的混合结构逐步转变为单一的FCC结构,而C层的结晶度逐渐升高。核/壳结构Co/C纳米颗粒在空气气氛下从250℃开始缓慢氧化,结晶度高的C壳层对Co核具有更好的保护作用。     

碳包覆磁性金属纳米胶囊的制备及表征

采用直流电弧等离子体法制备出表面包覆碳膜的金属纳米颗粒,这种纳米颗粒通常被称为“纳米胶囊”。其表面包覆气密的碳膜,具有良好的抗氧化性和稳定性。在甲烷气氛中蒸发各种磁性金属可获得具有良好物理化学性能的磁性纳米胶囊。对这种纳米胶囊进行了Ｘ射线衍射、Ｘ光电子谱、俄歇能谱、氧含量测定及ＨＲＴＥＭ、磁性分析等研究,提供了确定纳米颗粒新型壳－核结构的可靠实验依据。     

超细Ni-C核-壳纳米颗粒的制备及其磁学和微波吸收性能

以乙酰酮丙镍为原料,通过金属有机物化学气相沉积,合成超细Ni-C核-壳纳米颗粒。采用XRD、Raman光谱仪、TEM和多功能物理测试系统对合成的纳米颗粒的物相、结构和磁学性能进行表征。这种超细纳米颗粒外表包覆一层厚度1~3 nm的C层,内部Ni核的平均粒径为13 nm。磁学测试表明,超细Ni-C核-壳纳米颗粒的饱和磁矩为24.5 emu/g,矫顽力为65.5 Oe,远低于直径超过20 nm的Ni-C核-壳纳米颗粒的对应值。微波吸收测试表明,超细Ni-C核-壳纳米颗粒和石蜡的混合物的最小反射损失值(RL_(min))为-48.7 d B,有效带宽(BW_(eff),RL≤-10dB)为7.4 GHz,是一种非常具有潜力的微波吸收材料。     

纳米WC-Co复合粉末形貌的影响因素

随着现代工业的快速发展,纳米WC-Co复合粉末得到越来越广泛的应用,具有巨大的市场发展潜力。分别以偏钨酸铵(AMT)、可溶性钴盐、有机碳和超纯碳黑为原材料,采用喷雾转化和连续低温还原碳化法制备纳米WC-Co复合粉末,研究雾化转速、转化温度、碳源的选取对纳米WC-Co复合粉末形貌的影响。研究表明:纳米WC-Co复合粉末呈空壳球形结构,晶粒尺寸在100 nm以下,壳体有大量孔隙并存在破裂现象,Co相以fcc结构存在。在一定范围内,随雾化转速降低,颗粒尺寸增大;随转化温度升高,粉末球形化程度降低;有机碳源制备的复合粉末比碳黑制备的颗粒尺寸更大,壳壁更薄。     

有机电解质溶液中Au晶种生长法合成Au核@Pt壳纳米粒

在柠檬酸钠溶液中,采用光化学Au晶种生长法合成Au核@Pt壳纳米粒子.应用UV-Vis、TEM和XPS等分析手段研究了Au@Pt纳米粒子的结构、形貌、化学状态等.研究结果表明,所合成的Au@Pt纳米粒子具有核-壳复合结构,平均粒径为7.3～10.2 nm     

Biologically active polymers: synthesis and antimicrobial activity of modified glycidyl methacrylate polymers having a quaternary ammonium and phosphonium groups

Polymers with antibacterial activity have been synthesized by chemical modification of poly(glycidyl methacrylate). The glycidyl methacrylate was polymerized by the free radical polymerization technique. The poly(glycidyl methacrylate) was hydrolyzed and was chloroacetylated using chloroacetyl chloride. The chloroacetylated product was modified to yield polymers with either quaternary ammonium or phosphonium salts. The antimicrobial activity of the modified glycidyl methacrylate polymers has been examined against a variety of test microorganisms by the cut plug and the viable cell counting methods using shake flask of ten times diluted nutrient broth medium. All three polymers obtained were inhibitory to the growth of Gram negative bacteria (Escherichia coli, Pseudomones aeruginosa, Shigella sp. and Salmonella typhae) and Gram positive bacteria (Bacillus subtilis and B. cereus) as well as the fungus (Trichophytun rubrum). It was found that the growth inhibitory effect varied according to the structure of the polymer and the composition of the active group and increased with increasing the concentration of the polymer. The tested polymers showed more antimicrobial activity against Gram negative bacteria and the fungus, whereas were less active against Gram positive bacteria.     

Methods of production, structure, and properties of film materials based on the carbon—nitrogen system (survey)

About 50 papers devoted to producing and investigating the properties of carbon nitride films are critically reviewed. It is shown that reasonable experimental confirmation of synthesis of the hypothetical β-C₃N₄ does not yet exist. Carbon nitride films can be produced practically by all PVD and CVD methods. They may contain up to 50% nitrogen, have an amorphous structure, and atoms in carbon nitride sp²-bonded. The microstructure of amorphous CN films is mostly based on two types of clusters—cyanogen polymers and graphite-like domains with carbon atoms partially substituted by nitrogen. The relation between two microstructure types depends on the deposition conditions and crucially influences the film properties. The smaller the graphite-like clusters size and the more chaotically they are oriented in the film the harder will be the film. The factor which influences most the type of film microstructure and properties is the ion bombardment of the film during the deposition. The small friction coefficient, high elasticity, and relatively high hardness of nitride carbon films may make them useful as protective coatings of a storage medium in computers.     

Isolation and identification of styrene-degrading Corynebacterium strains, and their styrene metabolism

By supplying styrene in the gas phase as the sole carbon and energy source, styrene-degrading aerobic microorganisms were readily isolated from soil samples. They were identified as Corynebacterium pseudodiphtheriticum and similar species, or Pseudomonas sp. Growth experiments on some aromatic compounds, resting-cell reactions with them, and the measurement of degrading enzyme activities suggest that Corynebacterium sp. AC-5 and St-5 strains metabolize styrene through styrene oxidation into styrene oxide, then convert it into phenylacetaldehyde by a reaction using styrene oxide isomerase, and phenylacetaldehyde is reduced to 2-phenylethanol. The Corynebacterium sp. ST-10 strain did not have styrene oxide isomerase, and metabolized styrene oxide by an unknown enzymatic reaction. Possible metabolism of styrene was proposed for the Corynebacterium strains.     

Structural Performance of RC Beams Poststrengthened with Carbon, Aramid, and Glass FRP Systems

The use of fiber-reinforced polymers (FRPs) to poststrengthen concrete structures started to be investigated in the mid-1970s and today is widely recognized as an attractive technique to be used in civil structures, especially when aggressive environments prevent the use of materials that are susceptible to corrosion, such as steel. Different FRP poststrengthening techniques have been developed and applied in existing structures, aiming to increase their load capacity. Most FRP systems used nowadays consist of carbon fibers embedded in epoxy matrix. Regardless of the advantages and the good results achieved using carbon fiber-reinforced polymers, some new possibilities, such as the use of prestressing and lower cost fiber materials, are being analyzed in an attempt to provide viable alternatives for a more efficient, safe, and rational use of FRP systems. The main purpose of the present work was to make a comparative analysis of the behavior of reinforced concrete beams poststrengthened with carbon, aramid, and glass FRP subjected to static loading tests. Experimental results were evaluated against theoretical ones obtained through an analytical model that considers a trilinear behavior for the load versus displacement curves. The experimental results indicate that all FRP systems applied have appropriate structural performance for use in poststrengthening applications of RC. The choice of the more suitable system would, therefore, be strongly influenced by circumstances regarding cost limitations and level of reinforcement required.     

Interactions of Polymer/Coke Blends with Molten Steel at 1823 K: Interfacial Phenomena

With an aim to recycle waste polymers as a carbon resource in steelmaking, in‐depth investigations have been carried out on polymer/coke blends and molten steel at 1823 K. Three polymers, namely high density polyethylene (HDPE), polyethylene terephthalate (PET), and bakelite were blended with metallurgical coke and devolatilized at 1473 K using a drop tube furnace. High temperature interactions of various chars with molten steel were investigated at 1823 K using the sessile drop technique in argon atmosphere; the influence of polymers on the interfacial phenomena and carbon dissolution was determined. While the residual volatiles from HDPE did not affect the chemical composition of interfacial products, the coverage of the interfacial region was somewhat slower than metallurgical coke. Oxygen present in PET was found to oxidize liquid steel leading to the formation of FeO at the interface modifying both the chemical composition and the morphology of the interfacial region. CaCO₃, present as a filler impurity in bakelite was found to act as a fluxing agent and lowered the melting point of the ash layer at the metal/carbon interface. The addition of polymers improved the overall carbon dissolution into molten steel by a small extent as compared to metallurgical coke. This study has shown that a variety of waste polymers can be utilized to partially replace metallurgical coke in steelmaking.     

Three new Sarcocystis species, Sarcocystis giraffae, S. klaseriensis, and S. camelopardalis (Protozoa: Sarcocystidae) from the giraffe (Giraffa camelopardalis) in South Africa

Three new Sarcocystis species recovered from muscle fibers of the skeletal musculature of a giraffe in South Africa are described based on light and electron microscopy. Sarcocystis giraffae n. sp. formed slim macrocysts with a parasite-induced connective tissue encapsulation of the host muscle fiber in which the plasma membrane of the latter remained unaltered. The sarcocyst wall represented a new ultrastructural type that is characterized by fingerlike villar protrusions with a hairlike projection at the tip, containing microtubules penetrating the ground substance. Sarcocystis klaseriensis n. sp. formed small filiform microcysts with kinked finger-shaped villar protrusions of the wall, containing scattered microtubules or filaments, and represented another new ultrastructural type. Sarcocystis camelopardalis n. sp. formed small filiform microcysts with straplike villar protrusions of the wall, containing chainlike osmiophilic structures, and represented again a new ultrastructural type.     

Nb、Ti、Al多元微合金化对低碳锰钢抗氧化性能的影响

研究了经Nb、Ti、Al多元微合金化后，低碳锰钢抗氧化性能的变化规律。通过氧化动力学曲线的测定，确定了此类钢抗氧化级别的温度区间。Nb、Ti、Al微合金元素对低碳锰钢高温抗氧化性能的作用，主要是改善钢的高温氧化膜结构，依靠Nb、Ti元素形成弥散分布的微细碳化物质点，阻止铁离子的扩散，从而降低钢的氧化速率，提高抗氧化性能。     

谈质材料对结晶器保护渣熔融特性的影响

 连铸过程通常采用调节配炭量和配炭方式来调节保护渣的熔化速度和熔融层状结构。本文通过单向加热炉模拟保护渣在结晶器内的熔化过程，研究了六种炭质材料对保护渣熔化速度和熔融结构的影响。结果表明：含量相同时对保护渣熔化速度的控制作用最强的是500目超细石墨，而后依次是：半补强炭黑、390石墨、中超炭黑、土状石墨、增碳剂；配炭方式相同时，保护渣的熔化温度越高，其熔化速度越慢；采用炭黑加石墨的配炭方式时保护渣的烧结层厚度随炭含量增加而减薄，且若炭黑量小于2%时形成多层熔融结构，否则将形成不含半熔层的三层结构。     

The chlorocatechol-catabolic transposon Tn5707 of Alcaligenes eutrophus NH9, carrying a gene cluster highly homologous to that in the 1,2,4-trichlorobenzene-degrading bacterium Pseudomonas sp. strain P51, confers the ability to grow on 3-chlorobenzoate

Alcaligenes eutrophus (Ralstonia eutropha) NH9, isolated in Japan, utilizes 3-chlorobenzoate as its sole source of carbon and energy. Sequencing of the relevant region of plasmid pENH91 from strain NH9 revealed that the genes for the catabolic enzymes were homologous to the genes of the modified ortho-cleavage pathway. The genes from strain NH9 (cbnR-ABCD) showed the highest homology (89 to 100% identity at the nucleotide level) to the tcbR-CDEF genes on plasmid pP51 of the 1,2,4-trichlorobenzene-degrading bacterium Pseudomonas sp. strain P51, which was isolated in The Netherlands. The structure of the operon, including the lengths of open reading frames and intervening sequences, was completely conserved between the cbn and tcb genes. Most nucleotide substitutions were localized within and proximal to the cbnB (tcbD) gene. The difference in the chloroaromatics that the two strains could use as growth substrates seemed to be due to differences in enzymes that convert substrates to chlorocatechols. The restriction map of plasmid pENH91 was clearly different from that of pP51 except in the regions that contained the cbnR-ABCD and tcbR-CDEF genes, respectively, suggesting that the chlorocatechol gene clusters might have been transferred as units. Two homologous sequences, present as direct repeats in both flanking regions of the cbnR-ABCD genes on pENH91, were found to be identical insertion sequences (ISs), designated IS1600, which formed a composite transposon designated Tn5707. Although the tcbR-CDEF genes were not associated with similar ISs, a DNA fragment homologous to IS1600 was cloned from the chromosome of strain P51. The sequence of the fragment suggested that it might be a remnant of an IS. The two sequences, together with IS1326 and nmoT, formed a distinct cluster on a phylogenetic tree of the IS21 family. The diversity of the sources of these IS or IS-like elements suggests the prevalence of ISs of this type.