Rheological, mechanical and transport properties of blown films of high density polyethylene nanocomposites

Novel magnetic–dielectric composite ceramic obtained from Y3Fe5O12 and CaTiO3

Anisotropy evolution of low density polyethylene greenhouse covering films during their service life

Environmental sustainability has been the subject of interest and concern in the industry, mainly due to the generation of waste. As the phenolic compounds are toxic to aquatic organisms, the maximum level of 0.5 ppm is considered as concentration limit for releases in freshwater bodies by the Federal CONAMA Resolution no. 43

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Universidade federal do rio grande do norte centro de tecnologia departamento de engenharia química programa de pós-graduação em engenharia química

Aluminum additions to brittle Fe–6.5 wt.% Si alloys made possible the mechanical processing of these alloys at lower temperatures and thus being determinant in the development of the texture. The aim of this work was to analyse the evolution of the crystallographic texture of a spray-formed (SF) Fe–6.5 wt.% Si–1.0 wt.% Al during rolling operation for thin sheets production. The SF deposit was warm-rolled and then air cooled to obtain partial recrystallisation. The initial texture (0 1 1) [ 0 1 ¯ 1 ] [1 0 0] (// to normal direction-ND) of the deposit was changed to approximately (0 1 3) [ 1 1 ¯ 0 ] [1 1 0] (8° from ND) after the last reduction step. The maxima intensities of texture was found at 700 °C (89% of reduction) showing the influence of rolling temperature; after warm-rolling the entire texture changes to a partial ND fibre running from {0 0 1} to {1 1 0}, with negligible Goss intensities. The transition away from an ND fibre texture in the lattermost case (99.5% reduction) was in turn associated with the near-absence of shear bands.

Evolution of the texture of spray-formed Fe–6.5 wt.% Si–1.0 wt.% Al alloy during warm-rolling

A tecnica de difracao de raios X tem sido amplamente utilizada para a determinacao de fases cristalinas em materiais cerâmicos. Em argilas, a grande quantidade de quartzo e seu elevado grau de orientacao dificultam a identificacao e caracterizacao das demais fases presentes. Baseando-se no principio da sedimentacao, e apresentado neste trabalho um metodo simples e confiavel para a determinacao de argilominerais em materiais argilosos.

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Um método simples de caracterização de argilominerais por difração de raios X

The refractoriness and thermal shock resistance of any material is deeply related to the crystalline and amorphous phases present. In 1969, H. M. Rietveld developed a software that provides the complete characterization of single or multiphase materials. For nearly thirty years, since it was developed, the Rietveld Method has not been extensively used in quantitative analysis of natural raw material. This study has the objective to use this methodology along with other ones, in order to quantify the amorphous phase in refractory bauxites, considering its facilities and drawbacks. Four techniques were chosen to determine the vitreous phase in refractories raw materials, using the Rietveld method as theoretical basis. The fifth technique, named chemical dissolution in fluorydric acid, was used as a comparison method. The results illustrated that, despite the efforts, none of the techniques studied can be applied as a fast and reliable method to determine the amorphous content in refractories.

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Determinação de fase vítrea em bauxitas refratárias

The biaxial molecular orientation of blown films made of blends of linear low density polyethylene (LLDPE) with low density polyethylene (LDPE) was characterized by two different methods: complete pole figures obtained by wide angle X-rays diffraction (WAXD) and polarized infrared spectroscopy (IR) using the Krishnaswamy approach. The molecular orientation of the blends amorphous phase was also evaluated by polarized IR. The crystallinity of the blown films was determined by WAXD. A good correlation between the X-ray pole figures and the polarized IR results was obtained. At all blends compositions, it was shown that the a-axis of the polyethylene orthorhombic cell was preferentially oriented along the machine direction, the orientation degree along this direction increasing with the increase of the LDPE amount in the blends. The b-axis changed its preferential orientation from film thickness in the 100/0 LLDPE/LDPE film to along the transverse direction with increasing LDPE in the blends. The c-axis changed its orientation from orthogonal to normal direction in the 100/0 LLDPE/LDPE film to along the film thickness with increasing LDPE in the blends. Polarized IR characterization showed a negligible orientation of the amorphous phase. The amount of crystallinity was dependent on blend composition decreasing with the increase of LDPE content in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2760–2767, 2006

Correlations between processing parameters, morphology, and properties of blown films of LLDPE/LDPE blends, part 2: Crystalline and amorphous biaxial orientation by WAXD pole figures

Magnetic Properties of Spray Formed Fe-6.wt%Si Alloy

High silicon steels (Fe-6.5wt%Si) are excellent soft magnetic materials due to their high electrical resistivity and very low magnetostriction. However, as the Si content is increased above 3.5wt% the alloys become too brittle to be hot/cold rolled, therefore limiting processing possibilities. It has been verified that the B2 long-range ordering is the main cause for material britlleness since it induces the formation of dissociated superlattice dislocations and the correlated high stress concentrations leading to premature fracture. The combination of Al addition and high solidification rates may changes the kinetic of these ordering reaction. In this work in-situ X-ray diffraction from a high-energy syncrotron radiation source was employed in order to study disorder/order reaction (A2→ B2 + DO3) in spray formed Fe-6.5wt%Si and Fe-5wt%Si-1.5wt%Al alloys at 350oC, 770oC and 798oC. It may be predict that the ordering reaction from A2 (disordered bcc) to B2 is suppressed above about 800oC in the Fe-6.5wt%Si alloy, but not below 600oC, where A2 transforms to B2 + DO3. The results of the present work showed that the addition of aluminium coupled with the solidification rates prevailing during spray forming processing avoid the B2 ordering reaction even at 350oC, but did not avoid the formation of DO3 for both alloys in all temperatures studied. Introduction Iron-based alloys containing 5.3-11.2wt%Si form two kinds of ordered structures: B2 (Pm3m) and DO3 (Fm3m) on the basis of the fundamental crystal lattice of bcc (Im3m) [1, 2]. Up to about 5.9wt% Si, the B2 structure is formed from A2 (disorded solid solution with bcc lattice) by unlikeatom pairing of the first nearest neighbors. A further increase of the silicon content leads to a phase transition towards the ordered DO3 structure through additional ordering between the second neighboring atoms. Between about 5.9 and 7.9wt% both structures can be observed [1,3]. The relative amount of these two structures depends on the sample conditions [4]. High silicon steels (Fe-6.5wt%Si) are excellent soft magnetic materials due to their high electrical resistivity and very low magnetostriction. However, as the Si content is increased above 3.5wt% the alloys become too brittle to be hot/cold rolled. It has been verified that the B2 long-range ordering is the main cause for material britlleness since it induces the formation of dissociated superlattice dislocations and the correlated high stress concentrations leading to premature fracture [4]. The presence of aluminum [5] and high solidification rates can alter the kinetic of these ordering reaction [4,6-8]. Therefore, alternative approaches such as Chemical Vapor Deposition of silicon and melt spinning to fabricate high silicon steel sheets have been reported [9]. These methods are expensive and unsuitable to produce wide sheet of commercial scale. Spray forming, a relative rapid solidification process, was propose as an alternative approach to fabricate high Si steels, although only limited results are available [6,10]. Journal of Metastable and Nanocrystalline Materials Online: 2004-07-07 ISSN: 2297-6620, Vols. 20-21, pp 553-556 doi:10.4028/www.scientific.net/JMNM.20-21.553 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-19/03/20,17:06:53) The aim of this work was to investigate the disorder/order reaction (A2→ B2 + DO3) using X-ray synchrotron diffraction in spray formed Fe-6.5wt%Si and Fe-5wt%Si-1.5wt%Al alloys at 350, 770 and 798oC. Experimental Procedure The molten alloys were superheated to 1650 °C and atomized by nitrogen at a pressure of 0.5 MPa in a static close-coupled atomizer. Details of the equipment used were described elsewhere [11]. The deposition distance was 280mm (Fe-5wt%Si-1.5wt%Al) and 360mm (Fe-6.5wt%Si). The gas/metal mass flow ratio was 0.12. The structures of the alloys were determined at 350, 770 and 798oC by high energy X-ray synchrotron radiation at the European Synchrotron Radiation Facility of Grenoble. The high intensity available at a synchrotron source enables to record a diffractogram in a few minutes with sufficient count rates and JCPDS database was used to identify the X-ray diffraction patterns obtained. Results and Discussion Table 1 summarizes the structures present at 350, 770 and 798oC for spray formed Fe-6.5wt%Si and Fe-5wt% Si-1.5wt% Al alloys. Fig. 1 shows the X-ray diffraction patterns (XRD). The results for were compared to Matsumura et al [1] and Swann et al [2] results. Table 1. Structures present at 350, 770 and 798oC for spray formed Fe-6.5wt%Si and Fe-5wt%Si-1.5wt% Al alloys.

Rogerio Machado

Papers

Um método simples de caracterização de argilominerais por difração de raios X

Determinação de fase vítrea em bauxitas refratárias

Correlations between processing parameters, morphology, and properties of blown films of LLDPE/LDPE blends, part 2: Crystalline and amorphous biaxial orientation by WAXD pole figures

Magnetic Properties of Spray Formed Fe-6.wt%Si Alloy

Order/Disorder Transformations in Spray Formed FeSiAl Alloys