Magnetic material arrangement in oriented termites: a magnetic resonance study

Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g=2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite’s body (abdomen + thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5 ± 0.3 nm in diameter and an effective magnetic anisotropy constant, K_eff between 2.1 and 3.2 × 10⁴ erg/cm³. A sudden change in the double integrated spectra at about 100 K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system.     

Properties of blends containing two liquid crystalline polymers

Blends containing two, wholly aromatic, naphthalene-based liquid crystalline polymers (LCPs) are studied. Experimental results show that the viscosities of the resulting blends are lower than the parent LCPs over the entire shear-rate range investigated. The orientation development following capillary flow demonstrates, that over a defined blend composition range, some blends have higher orientability than the constituent polymers. This is further manifested in the tensile and flexural properties of injection-molded specimens. A detailed analysis indicates that in the composition range where synergistic effects are observed in orientation development as well as in mechanical properties, only one glass transition temperature is detected. This suggests that “miscibility” is desirable for obtaining maximum properties in these blend systems.     

PNL分子在正、负电性纳米银上的吸附取向

制备了两种不同电性的纳米银粒子的脉体,发现当邻菲罗啉分子分别吸附在这两种纳米银上时,其表面增强喇曼谱有明显的不同.在正电性纳米银上,面外弯曲模式受到增强,而在负电性纳米银上,面内伸缩模式受到增强,通过分析增强谱的差异表明,分子在这两种不同电性胶态纳米银表面上可能分别以平躺及站立方式吸附.     

Influence of particle orientation on retrieving cirrus cloud properties by use of total and polarized reflectances from satellite measurements

The influence of ice crystal orientation was investigated on retrieving cirrus optical thickness (τ) and aspect ratio of ice crystals (Q) from satellite measurements using the total and polarized reflectances at a wavelength of . We considered columnar and plate like hexagonal ice crystals whose long axes are randomly oriented in the horizontal plane (2D model) with some amplitude of oscillation expressed by a Gaussian distribution function with the standard deviation of σ.The retrieved τ and Q values significantly depend on the assumption of σ, in particular for the plate type. Furthermore, the relationship between σ and the retrieved values depends on the solar, satellite, and target geometries. In our case study, for one target area, τ value retrieved using the 2D model with σ=5° was approximately twice larger than that using the 2D model with σ=20°, while the retrieved Q value was not significantly influenced by σ. For another target area, the τ(Q) retrieved using the 2D model with σ=5° was about 1.5 (1.8) times larger than that retrieved using the 2D model with σ=20°.     

Description of the state of deformation of ethylene–tetrafluoroethylene alternating copolymer films estimated by using a model proposed in terms of orientation of crystallites within a rod

To study the deformation mechanism of ethylene–tetrafluoroethylene alternating copolymer films caused by elongation, a model relating crystal orientation to the orientation of the rods was proposed. The orientation distribution of crystallites within the rod was given as the correlation with the rod orientation. The distribution functions of a given reciprocal lattice vector of the crystal plane were derived from the two functions of the crystallites and of rods with several parameters representing the orientation of rods and the rotation of crystallites within a rod. By choosing suitable values of the parameters, the calculated functions were in good agreement with the results of X-ray diffraction experiments. From the values of the parameters to give the best fit between calculated and observed results, it turned out that the characteristic orientation of the c-axis is mainly due to the preferential orientation of the rod with respect to a stretching direction and is hardly affected by the rotation of crystallites within the rod. Using the two orientation functions concerning rods and crystallites, Hv light scattering was formulated by introducing an interparticle interference effect of the rods. The calculated results assumed the characteristic profile of the observed patterns as the superposition of broadleaf lobes and a sharp pattern of streaks. Received: 28 April 2000 Accepted: 30 September 2000     

碱性品红分子在正、负电性纳米银上的吸附取向

制备了两种不同电性的纳米银粒子的胶体,发现当碱性品红分子分别吸附的在这两种纳米银上时,其表面增强拉曼谱在谱线的强度及谱线数目上均有有明显的不同。在正电性纳米银上,主要是面内模式得到增强,且碱性品红特征峰的强度是I1589>I1524>I1371。而在负电性纳米银上,面内伸缩模式及面外弯曲模式均得到增强,且碱性品红特征峰的强度是I1588<I1520=I1371,通过分析增强谱的差异表明,分子在这两种不同电性胶态纳米银表面上可能分别以垂直及倾斜方式吸附。     

用非偏振拉曼光谱表征聚合物的取向行为

采用非偏振激光为拉曼光源表征了聚丙烯纤维、尼龙6扁丝以及聚乙烯管材等3种取向的聚合物样品。实验表明,当入射光作用于样品的不同面(方向)时,所得到的拉曼光谱存在明显的差异。这一结果为表征聚合物取向开创了新思路,并拓宽了拉曼光谱技术的应用范围。     

Carbon-content dependent effect of magnetic field on austenitic decomposition of steels

The transformed microstructures of the high-purity Fe-0.12C alloy and Fe-0.36C alloy heat treated without and with a 12 T magnetic field have been investigated to explore the carbon-content dependent field effect on austenitic decomposition in steels. Results show that, the field-induced transformed morphology characteristics in different alloys differ from each other. In the Fe-0.12C alloy, the pearlite colonies are elongated along the field direction, and shaped by the chained and elongated proeutectoid ferrite grains in the field direction. However, in the Fe-0.36C alloy, the field mainly reduces the amount of Widmänstatten ferrite and elongates the formed proeutectoid ferrite grains in the field direction. No clear field direction alignment is obtained. The magnetic field also demonstrates carbon-content dependent effect on the texture of the formed ferrite. It clearly enhances the 〈001〉 fiber of the ferrite in the transverse field direction in the Fe-0.36C alloy. This field effect is related to the crystal lattice distortion induced by carbon solution and this impact becomes stronger with the increase of the carbon content. For the Fe-0.12C alloy, this field effect is greatly reduced due to the reduced carbon oversaturation in ferrite and elevated formation temperature. The orientation relationships (ORs) between the pearlitic ferrite and the pearlitic cementite in both alloys are less affected by the magnetic field. No obvious changes in the either type of the appearing ORs and their number of occurrences are detected.     

Influence of pineapple leaf fiber and it's surface treatment on molecular orientation in,and mechanical properties of,injection molded nylon composites

The objective of his work is to show that pineapple leaf fiber (PALF) can be used successfully to reinforce a high melting polymer such as nylon. One of the most important barriers to the utilization of lignocellulosic materials in polymer matrix composites is their limited temperature resistance. As a consequence, they are mostly used to reinforce low melting temperature polymers such as polyethylene and polypropylene as well as polystyrene. However, this work reveals that PALF can be used to reinforce nylon. This is because of its very low lignin content. Nylon 6/66 composites containing a fixed amount of 20 wt % PALF in the form of short and fine fibers were prepared with a laboratory twin screw extruder and then injection molded. The mechanical properties of three types of PALF, i.e. untreated, alkaline- and silane-treated, were studied. Significant improvements in modulus and heat distortion temperature were obtained. The crystalline structure and orientation in the injected composites were investigated with synchrotron wide angle x-ray scattering (WAXS). It was found that both PALF and nylon crystallites oriented well along the flow direction and this is the key factor for the improvements observed.     

Film morphology, orientation and performance of dodecyl/carboxyl functional polysiloxane on cotton substrates

A novel polysiloxane (RCAS) bearing dodecyl and carboxyl side groups was synthesized by reaction of a dodecyl/amino functionalized polysiloxane with maleic anhydride. Film morphology, molecular orientation and performance of the synthesized polysiloxane on cotton substrates were investigated by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray photoelectron microscope (XPS) and so on. Affected by the dodecyl and polar carboxyl side groups, RCAS formed a semi hydrophilic, macroscopic smooth but actually uneven siloxane film with many pillar-likes or small humps on the treated substrate surfaces. On the natural cotton surface, RCAS may take such an orientation to form its film that the Si-CH₃, Si-C₁₂H₂₅ groups projected outward into air, while the carboxyl groups pointed inward to the substrate, interacting with the hydroxyls of the cotton substrates in ester and hydrogen bonds or twisted away from the negatively charged cotton fiber surface. As a result of such a film-formation, RCAS provided the treated fabric with not only a good wettability of about 22.96 s and a whiteness of 88.44°, but also an improved softness as well as thickening handle.