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排序方式: 共有3367条查询结果,搜索用时 15 毫秒
51.
Lucas F. de Lima Cristiane C. Maciel André L. Ferreira Rafael J. G. Rubira Carlos J. L. Constantino Marystela Ferreira 《应用聚合物科学杂志》2021,138(5):49750
In this paper, we report the controlled fabrication of layer-by-layer (LbL) films deposited on gold substrates with three different supramolecular architectures using polypyrrole (Ppy) and magnetite nanoparticles (Fe3O4-np), besides conventional poly(allylamine hydrochloride) (PAH) e poly(vinyl sulfonic acid) (PVS) polyelectrolytes, demonstrating the synergistic effect between Ppy and Fe3O4-np such as a result of their interaction. Modified gold electrodes were analyzed by contact angle (wettability), surface plasmon resonance (SPR), raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The (Fe3O4-np/Ppy)3 architecture was also evaluated by scanning electron microscopy. The modified gold electrodes present more homogeneous covering, higher electron transfer and a decrease of resistance with the incorporation of the nanostructured materials such as Ppy and Fe3O4-np forming (Fe3O4-np/Ppy)3 LbL film. The results carried out in this study suggest that the (Fe3O4-np/Ppy)3 LbL film can be applied as a possible electrochemical or optical non-enzymatic sensor for analytical detection. 相似文献
52.
Anna Raffaela de Matos Costa Juliana Cysneiros Lima Raquel dos Santos Lhaira Souza Barreto Mariana Alves Henrique Laura Hecker de Carvalho Yêda Medeiros Bastos de Almeida 《应用聚合物科学杂志》2021,138(36):50916
This work deals with the rheological, morphological, and thermal properties of composites having poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and their blends as matrices, and rice husk ash (RHA) as a filler. The study determines the effect of composition on the change in viscosity and rate of degradation during processing in a torque rheometer. Our data indicates that thermal stability and degradation during processing depend on matrix composition and filler concentration. SEM micrographs show both partial adhesion of the filler to the matrices and filler pullout. Optical microscopy shows particle agglomeration and that agglomerate size increased with filler content. FTIR investigates the shifting of absorption bands of PET/PA6 composite after the addition of RHA and attributes the selective dispersion of RHA to the formation of hydrogen bonds. Our data supports the idea that filler employed here is an option to develop polymer composites with improved properties. 相似文献
53.
Carla G. Luciano Larissa Tessaro Rodrigo V. Lourenço Ana Mônica Q. B. Bittante Andrezza M. Fernandes Paulo J. A. Sobral 《应用聚合物科学杂志》2021,138(42):51246
Research on biopolymers-based active films produced with natural antioxidants and/or antimicrobials has gained attention over the last few years; however, anti-mold activity has been less studied than those of anti-bacteria. The aim of this work was the development and characterization of bi-layer films based on gelatin with natamycin and/or “Pitanga” leaf hydroethanolic extract in the second thin layer in order to determine the effects of these bioactive compounds on bi-layered film properties. The films were characterized regarding their moisture content and solubility in water, optical properties, microstructure, mechanical and thermal properties, water contact angle, water vapor permeability, UV/visible light transmission, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and antioxidant and anti-mold activities. Active films presented activity against Penicillium spp and Aspergillus niger and demonstrated antioxidant activity, as measured by ABTS •+ and DPPH • methods. Neither additive used in the films' second layer significantly affected the films' moisture content, thermal properties or the molecular interactions of the polymer matrix, assessed by FTIR, although some mechanical properties were affected, and the water contact angle. In conclusion, bi-layer films have reduced the quantity of additives required to maintain the antioxidant and anti-mold activities, as compared to similar monolayer films of the same thickness. 相似文献
54.
Pamela Sierra Garcia Juliana Aristéia de Lima Carlos Henrique Scuracchio Sandra Andrea Cruz 《应用聚合物科学杂志》2021,138(29):50703
This work aims to investigate the effect of adding vulcanized or partially devulcanized rubbers on recycled polypropylene (PPr), considering thermomechanical and morphological properties. The study proposes to better understand how structural changes underwent by rubber (after the devulcanization) contributed to improving the mechanical properties of the PPr. The PPr/rubber blends were prepared by a co-rotating twin-screw extruder and then were injected. The blends composed of the most devulcanized rubbers by microwaves with refined microstructure showed higher values of elongation at break and toughness. Data showed that the devulcanization process applied to the rubber interfered positively in its adhesion to the PPr. Data from dynamic mechanical analysis and atomic force microscopy indicated that the most devulcanized rubbers presented an interface more connected to PPr. These chemical interactions possibly impacted the mechanical properties of the PPr. Moreover, dilatation processes favored the fracture mechanisms of the PPr when rubber was added to it. 相似文献
55.
The mismatch between the thermal expansion coefficients of ceramics and metals and the differential stresses it causes at
the interface create problems in metal to ceramic joining. Research has been con-ducted to solve this problem in thermal barrier
coating technology. Previous studies have considered met-al-ceramic multilayers or graded-coatings, which include a metallic
bond coat. In this study, a graded plasma-sprayed metal-ceramic coating is developed using the deposition of premixed metal
and ceramic powders without the conventional metallic bond coat. Influences of thickness variations, number, and composition
of the layers are investigated. Coatings are prepared by atmospheric plasma-spraying on In-conel 718 superalloy substrates.
Ni-Cr-Al and ZrO2 -8 % Y2O3 powders are used for plasma spraying. Ad-hesive and cohesive strength of the coatings are determined. The concentration profile
of the elements is determined by x-ray energy-dispersive analysis. The microstructure and morphology of the coatings are investigated
by optical and scanning electron microscopy (SEM). Results show that the mixed metal-ce-ramic coating obtained with the deposition
of premixed powders is homogeneous. The morphology and microstructure of the coatings are considered satisfactory. 相似文献
56.
Elastic modulus measurements via laser-ultrasonic and knoop indentation techniques in thermally sprayed coatings 总被引:1,自引:0,他引:1
R. S. Lima S. E. Kruger G. Lamouche B. R. Marple 《Journal of Thermal Spray Technology》2005,14(1):52-60
Nondestructive techniques for evaluating and characterizing coatings were extensively demanded by the thermal spray community;
nonetheless, few results have been produced in practice due to difficulties in analyzing the complex structure of thermal
spray coatings. Of particular interest is knowledge of the elastic modulus values and Poisson’s ratios, which are very important
when seeking to understand and/or model the mechanical behavior or to develop life prediction models of thermal spray coatings
used in various applications (e.g., wear, fatigue, and high temperatures). In the current study, two techniques, laser-ultrasonics
and Knoop indentation, were used to determine the elastic modulus of thermal spray coatings. Laser-ultrasonics is a noncontact
and nondestructive evaluation method that uses lasers to generate and detect ultrasound. Ultrasonic velocities in a material
are directly related to its elastic modulus value. The Knoop indentation technique, which has been widely used as a method
for determining elastic modulus values, was used to compare and validate the measurements of the laser-ultrasonic technique.
The determination of elastic modulus values via the Knoop indentation technique is based on the measurement of elastic recovery
of the dimensions of the Knoop indentation impression. The approach used in the current study was to focus on evaluating the
elastic modulus of very uniform, dense, and near-isotropic titania and WC-Co thermal spray coatings using these two techniques.
Four different coatings were evaluated: two titania coatings produced by air plasma spray (APS) and high-velocity oxyfuel
(HVOF) and two types of WC-Co coatings, conventional and multimodal (nanostructured and microsized particles), deposited by
HVOF.
The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), 5–8 May, 2003, Basil R. Marple and Christian Moreau, Eds., ASM International,
2003. 相似文献
57.
Anderson da Silva Soares Telma Woerle de Lima Daniel Vitor de LuPcena Rogerio Lopes Salvini GustavoTeodoro Laureano Clarimar Jose Coelho 《计算机技术与应用:英文》2013,(9):466-475
The multiple determination tasks of chemical properties are a classical problem in analytical chemistry. The major problem is concerned in to find the best subset of variables that better represents the compounds. These variables are obtained by a spectrophotometer device. This device measures hundreds of correlated variables related with physicocbemical properties and that can be used to estimate the component of interest. The problem is the selection of a subset of informative and uncorrelated variables that help the minimization of prediction error. Classical algorithms select a subset of variables for each compound considered. In this work we propose the use of the SPEA-II (strength Pareto evolutionary algorithm II). We would like to show that the variable selection algorithm can selected just one subset used for multiple determinations using multiple linear regressions. For the case study is used wheat data obtained by NIR (near-infrared spectroscopy) spectrometry where the objective is the determination of a variable subgroup with information about E protein content (%), test weight (Kg/HI), WKT (wheat kernel texture) (%) and farinograph water absorption (%). The results of traditional techniques of multivariate calibration as the SPA (successive projections algorithm), PLS (partial least square) and mono-objective genetic algorithm are presents for comparisons. For NIR spectral analysis of protein concentration on wheat, the number of variables selected from 775 spectral variables was reduced for just 10 in the SPEA-II algorithm. The prediction error decreased from 0.2 in the classical methods to 0.09 in proposed approach, a reduction of 37%. The model using variables selected by SPEA-II had better prediction performance than classical algorithms and full-spectrum partial least-squares. 相似文献
58.
59.
A steady-state interval operability methodology is introduced here for multivariable non-square systems with fewer inputs than output variables to be used in the design of model-based constrained controllers (MPC, DMC). For such systems, set-point control is not possible for all the outputs and interval control is needed. The proposed iterative approach enables the selection of the needed interval constraints systematically, so that the tightest possible control is achieved without rendering the control problem infeasible. The application of this methodology to high-dimensional industrial problems characterizing processes of Air Products and Chemicals and DuPont shows that very significant reduction of the constrained region can be achieved from the steady-state point of view. Ratios of the initial to the calculated volume of the constrained regions examined range between 104 and 108. 相似文献
60.
A simulation of the profile of holographically recorded structures in photoresists is performed. In addition to its simplicity this simulation can be used to take into account the effects that arise from exposure, photosensitization, development, and resolution of positive photoresists. We analyzed the effects of isotropy of wet development, nonlinearity of the photoresist response curve, background light, and standing waves produced by reflection at the film-substrate interface by using this simulation, and the results agree with the experimentally recorded profiles. 相似文献