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81.
采用热模拟技术研究GCr15轴承钢经不同温度共析转变,得到不同片层间距珠光体组织对接下来的保温过程中碳化物粒状倾向的影响。结果表明:通过降低共析转变温度得到了细小的珠光体组织,随着珠光体球团直径和片层间距的减小,经过相同保温处理后试样显微硬度减小,碳化物呈粒状倾向增大,在500℃共析转变后得到碳化物片层熔断的退化状态珠光体,碳化物的粒状倾向最大。 相似文献
82.
Extensive morphological studies on a syndiotactic polystyrene (sPS) sample prepared from compression molding were carried out using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). SAXS was conducted at 25C as well as at 150C to enhance the scattering contrast in order to obtain more reliable morphological parameters. The compression-molded sample was crystallized into a orthorhombic crystal lattice characterized by wide-angle X-ray diffraction (WAXD). A similar weight fraction of crystallinity, ca. 0.37, was obtained from both WAXD and differential scanning calorimetry measurements.In addition to the scattering peak at a scattering vector of ca. 0.36 nm–1 attributable to the presence of lamellar/amorphous layers, anomalous scattering at the zero angle was found from the SAXS intensity profiles. Based on the Debye–Bueche theory, the scattering profile of this peculiar zero-angle scattering was deduced and was subtracted from the raw intensity profile to obtain the intensity profile exclusively associated with the lamellar/amorphous structure. A consistent long period was obtained for SAXS measured either at 25 or 150C, provided that the appropriate subtraction of intensities due to the zero-angle scattering was conducted. Moreover, the lamellar thickness deduced from the one-dimensional correlation function was in good agreement with TEM results. A difference scattering pattern derived from SAXS measured at 150 and 25C was obtained and a comparison of the morphological parameters was provided as well. 相似文献
83.
84.
Yanhuizhi Feng Huai-Ling Gao Di Wu Yu-Teng Weng Ze-Yu Wang Shu-Hong Yu Zuolin Wang 《Advanced functional materials》2021,31(43):2105348
Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications. 相似文献
85.
Zhaoping Hou Xinhe Yang Zihan Tian Liangliang Liu 《International Journal of Applied Ceramic Technology》2023,20(5):2737-2746
Porous Al2O3 ceramic beads with a small-scale lamellar pore structure were prepared by the dripping-ice templating method. The densification behavior of lamellar walls and the attrition resistance of porous Al2O3 beads were investigated. For the two-dimensional structural lamellar walls, the intrinsic pores shrunk, and the necking area grew during the sintering process, leading to the densification of lamellar walls and the shrinking of porous beads. In addition, the two-dimensional lamellar walls and three-dimensional Al2O3 bulk are compared and possibilities of elaborating of the discrepancy in grain size and pore morphology are discussed. Attrition resistance was determined by a grinding test. The dominant attrition mechanism of porous Al2O3 beads is abrasion. High sintering temperature led to a decrease in the attrition rate due to a wider necking area and denser pore walls. 相似文献
86.
《International Journal of Hydrogen Energy》2020,45(36):18587-18599
A bicontinuous lamellar silica mordenite (HM@KCC-1) has been successfully synthesized by microemulsion technique assisted with mordenite-seed recrystallization, followed by protonation and impregnation with platinum (Pt). The catalysts were extensively characterized by XRD, N2 adsorption, FTIR, FESEM, TEM and ESR and the activity was tested in hydroisomerization of n-hexane. Fourier Transform-Infrared Spectroscopy (FT-IR) study through pyridine and 2,6- dimethylpyridine adsorption revealed that Pt/HM@KCC-1 possessed abundant Lewis acid sites and moderate Brønsted acid sites while Pt/HM possessed strong Lewis and Brønsted acid sites. At 300 °C, the conversion of n-hexane on Pt//HM@KCC-1 reached 75% with 98% isomer selectivity and 74% isomer yield. The enhancement of catalytic performance is attributed to the well-dispersed Pt nanoparticles, tuned acidic properties and improved textural properties which provided a well balance in the acid/metal functions. Thus, favours the reaction towards higher hydroisomerization selectivity, limiting the undesired consecutive cracking reaction. 相似文献
87.
The morphology of segmented polyurethane was studied with an electron microscope. Polymers were obtained by the prepolymer method from poly(ethylene adipate), 4,4-diphenylmethane diisocyanate and 1,4-butanediol. The unstained sample showed spherulites with fibrillar structure. Attempts were made to enhance the contrast in order to study the fibrillar structure more thoroughly. The staining method used to study the structure of lamellae is described. 相似文献
88.
J.P. FORESTIER 《International journal of cosmetic science》1992,14(2):47-63
Bien que le stratum corneum soit composé de cellules ‘mortes’, il est le siège d'une activité métabolique très importante. Mais, contrairement à la plupart d'autres tissus, cette activité a la particularité d'étre extra-cellulaire. Elle est due à des enzymes excrétées par les Corps d'Odland avec les bicouches céramidiques. Ces enzymes sont des hydrolases, elles sont identiques ou très proches de celles des lysosomes. Les principales activités observées correspondent à une (ou des) glycosidase(s), une phospholipase, une sphingomyélinase, une phosphatase, une (ou des) estérase(s), des sulfatases, des protéases. Comme les hydrolases des lysosomes, elles semblent peu spécifiques. Ce pool enzymatique pourrait jouer plusieurs rôles fondamentaux, notamment: 1. La transformation des bicouches gluco-céramidiques en bicouches ceramidiques plus lipophiles; 2. L'élimination de la membrane plasmique, dont certains produits du catabolisme, comme les acides gras et les céramides, peuvent être intégrés aux bicouches céramidiques; 3. La diminution de la cohésion entre les cornéocytes; 4. La protection contre l'intrusion de corps étrangers. Comme tout système enzymatique, les hydrolases extra-cellulaires, sont certainement soumises à des régulations. Plusieurs de ces régulations sont envisagées. A partir de considérations d'enzymologie, le pH de la base du stratum corneum peut être estiméà environ 5. En cosmétologie, les enzymes du stratum corneum sont mises à contribution pour rendre actifs des précurseurs. L'étude des conséquences des modifications de l'activité enzymatique sur l'état de la peau pourrait constituer une future voie de recherche extrêmement prometteuse. 相似文献
89.
Hexagonal (Hx-ZrO2) and lamellar (L-ZrO2) phases of zirconium oxide have been prepared using the supramolecular templating approach. Long chain primary alkyl amines led to the formation of lamellar phases, while quaternary ammonium surfactants gave hexagonal phases. The materials have been characterized by XRD, TG/DTG, IR, XPS, SEM and EDX techniques. The influence of various synthesis parameters such as (i) the ZrO2 surfactant ratio, (ii) the surfactant/water ratio, (iii) the nature of surfactant, (iv) the crystallization temperature and (v) the crystallization time have been investigated. The final solid products were found to be thermally unstable regardless of their structure. Removal of the surfactant from the mesopores by solvent extraction without damaging the structure was not possible. 相似文献
90.
The Sn-Zn system has a eutectic structure of a broken lamellar type. Dependence of the broken-lamellar spacing λ and the undercooling
ΔT on V and G were investigated, and the relationship between them was examined. A Sn-Zn (99.99%) high-purity eutectic alloy was melted
in a graphite crucible under vacuum atmosphere. This eutectic alloy was directionally solidified upward with a constant growth
rate V (8.30 μm/s) and different temperature gradients G (1.86–6.52 K/mm), and also with a constant temperature gradient (6.52 K/mm) and different growth rates (8.30–165.13 μm/s)
in a Bridgman-type directional solidification furnace. The lamellar spacings λ were measured from both transverse and longitudinal
sections of the specimen. The λ values from the transverse section were used for calculations and comparisons with the previous
works. The undercooling values ΔT were obtained using growth rate and system parameters K
1 and K
2. It was found that the values of λ decreased while V and G increased. The relationships between lamellar spacing λ and solidification parameters V and G were obtained by linear regression analysis method. The λ2
V, ΔTλ, ΔTV
−5, and λ3
G values were determined using λ, ΔT, V, and G values. The experimentally obtained values for the broken-lamellar growth (Sn-Zn eutectic system) were in good agreement
with the theoretical and other experimental values. 相似文献