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By Lijuan Li, Zheng Lu, Xin Xia, Qijie Zhai, Qingchun Li

"Pulsed current and pulsed magnetic field have been applied to the bainite transformation of Cr5 steel. Three groups of experiments were conducted. In the first group, ordinary resistance furnace was used for heat treatment. The Cr5 specimens were rapidly heated up to austenitization temperature 940 °C, held for 20 min, air cooled to bainite transformation temperature 350 °C, held for 10, 20, or 40 min and then air cooled to room temperature. The second and the third group shared the same temperature-time curve with that of the first group, but their heat resources came from the Joule heat produced by pulsed current. 1.5 T pulsed magnetic field was exerted on the third group specimens when they were held at 350 °C, but the second group specimens did not undergo the treatment of magnetic field. It was found that both pulsed current and pulsed magnetic field obviously retarded the bainite transformation. The phenomena were discussed in terms ofliterature results.IntroductionApplying pulsed current and pulsed magnetic field technology are very pronnsmg ways to change the microstructure of materials by affecting the phase transformation process. People had found that pulsed current dramatically influences the behaviors of materials, for example, electromigration effect [l], the solidification of metals and alloys [2, 3], electroplasticity [4, 5], crystallization of amorphous alloys [6], healing of metal materials [7] and so on. As to pulsed magnetic field technology, a lot of effort had been spent on grain refinement in solidification of metals [8, 9], recrystallization of cold-worked metals and alloys [10] and Fe-based alloys solid-state phase transformation [11, 12]. Though application of pulsed current and pulsed magnetic field technology have proliferated in recent years, investigation on their effects on solid/solid phase transformation, especially bainite transformation, is lacking. The aim of this paper is to show the effects of pulsed current treatment (C-T) and the combined treatment of pulsed current and pulsed magnetic field (CM-T) on bainite transformation of commercial Cr5 steel"

Jan 1, 2014

By Zhenbo Zhao

The processes and equipment for INLRFH (Isothermal Normalizing by Utilizing the Residual Forged Heat) of alloy carburizing steel products are presented. It is shown that four key parameters: namely (I) cooling rate before isothermal normalizing, (IT) the lowest cooling temperature before isothermal normalizing, (111) isothermal normalizing temperature and (IV) isothermal normalizing time, should be controlled. The prediction and calculation of these parameters can be achieved on the basis of components treated and the technical requirements of the steel parts by an on-line expert system. The cost-reductions due to the energy savings resulting from implementing this system for automotive parts heat-treatment are most promising.

Jan 1, 1999

By Chengyi Ding, Xuewei Lv, Senwei Xuan, Jie Qiu, Yun Chen, Kai Tang

Isothermal reduction kinetics of CF2 by 30% CO and 70% N2 at 1123, 1173 and 1223 K was investigated by TGA in this study. The reduction rate analysis indicated that reduction of CF2 comprises three stages during the whole reduction process, Apparent activation energy of samples CF2 reduction is 34.37 kJ/mol. The ln-ln analysis implied the reduction of CF2 was expressed initially by a 2D subsequently by 3D shrinking layer reaction.

Mar 1, 2017

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Sergio N. Monteiro

Polymer matrix composites have been applied in components such as helmets and shielding for which toughness is a major requirement. Natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with different amounts, up to 30% in volume, of a promising high strength natural fiber from the Amazon region known as curaua. The results showed a remarkable increase in the notch toughness with the amount of incorporated curaua fibers. This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

Jan 1, 2009

By Carlos Maurício F. Vieira, Lázaro A. Pizatto, Marcus Paulo Cardoso, Sergio Neves Monteiro, Joao Victor C. Nunes, Gustavo S. R. Matheus, Frederico M. Margem

The interest in composites with natural fibers is due, among other factors, to the growing worldwide concern with the preservation of environment and renewable raw materials. The natural fibers have many particular properties that make them an attractive alternative to traditional synthetic fibers. The advantages of using these fibers are: low cost, renewability, biodegradability, low toxicity, abundance and specific strength. The searching for new suitable, economically viable and technologically advanced materials justifies the accomplishment of this work that aims at comparing the mechanical behavior of polyester matrix composites with epoxy matrix composites reinforced with hemp fibers Izod impact tested. The specimens with dimensions: 10 63 12.7 mm, made in different volume fractions of fiber: 0–30 vol%. The samples were tested at PANTEC pendulum model XC-50 located at LAMAV/UENF. With this research was possible to analyse the mechanical properties of these two new materials.

Mar 1, 2018

By Fernanda de Paula, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Carlos Maurício. F. V, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Jan 1, 2015

By Ygor Macabu de Moraes, Jean Igor Margem, Carolina Gomes Dias Ribeiro, Frederico Muylaert Margem, Sergio Neves Monteiro, João Batista Vasconcelos

A natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with one or two layers of batt malva and jute fibers. The results showed are markable increase in the notch toughness with increasing layers of mauve blankets and jute.This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

Mar 1, 2017

By Carlos Maurício F. Vieira, Giulio R. Altoé, Maria Carolina A. Teles, Sergio N. Monteiro, Maycon A. Gomes, Frederico M. Margem, Gabriel O. Glória

Due to growing concern about the ambient impacts, the society is demanding for materials that are environmentally friendly. The lignocellulosic fibers, like PALF fibers, appears like an option to replace the synthetic ones in composites with polimerics matrices. Besides the environmental advantages, the lignocellulosic fibers have economical and some properties advantages like the low density in comparison with the synthetic fibers. Nowadays the lignocellulosic are used in industries, like the automobile and aerospace. This objective of this study was to analyze the absorbed impact energy of the composites reinforced with PALF fibers. The fibers were incorporated into the polyester matrix with volume fraction from 0 to 30%. The results showed increase in the absorbed impact energy with the increase of the percentage of fiber incorporated. The fracture surface of the specimens were analyzed by SEM (scanning eléctron microscope) and indicates that the PALF fibers act as reinforcement for the polyester matrix.

Mar 1, 2017

By Pertti Koukkari

The novel Jarogain process combines treatment of the jarosite residue of zinc manufacturing and processing of arc furnace dust from steelmaking to a holistic recovery technology. The new hydrometallurgical approach is targeted to recover the major constituents (Fe, Zn, Pb) as well as valuable components such as Ag, Au, In and Ga from the jarosite-dust mixture as reusable concentrates. The fractionation process proposed by VTT and Aalto University takes advantage of jarosite being readily fine powder and directly available for wet chemical processing. Jarogain process provides an energy efficient opportunity for jarosite utilization as value added products. The experimental proof-of-concept of key stages of the process will be outlined with a comparison of available pyrometallurgical treatments of jarosite waste. The techno-economical assessment is based on estimated investment and variable production cost using the discounted cash flow (DCF) analysis.

By P. Maraboutis

Iron removal by precipitation as jarosite from Fe-Ni-Co sulfate solutions, (synthetic or real, resulting from laterites leaching) has been investigated. Precipitation was carried out at 95 C, and at an initial pH 1.6, which was either kept constant with CaCO3 or Li2CO3 additions, or left to drift with the evolution of the reaction to lower values. The precipitation of K-, NH4- and Na- jarosite was initially examined using synthetic solutions. In all cases, hydronium ions were incorporated into the precipitate as well. Residual iron in solution was lower (0.2-1 g/1) and equilibrium was achieved faster (within 4-8 h) when precipitating K¬jarosite at constant pH, using CaCO3 for neutralization. Nickel and cobalt losses were small. Na- jarosite precipitation was also studied from real solutions with high initial iron content, under constant pH=1.5, controlled with CaCO3 additions, and it was shown that low residual iron concentration in solution (0.3-0.5 g/1) can be achieved again, with relatively small nickel and cobalt losses. The thickening and filtration characteristics of the precipitates were excellent in all cases examined.

Jan 1, 1988

By F. Elgersma

A high purity electrolysis solution is essential for hydrometallurgical zinc winning processes. For this reason ferric iron containing compounds such as jarosite are precipitated as iron and impurity collector during the calcine leaching. Jarosite thus forms a chemical waste and creates environmental problems. This research contributes to the development of a wet jarosite treatment process, where less contaminated jarosite is produced which can act as an iron source. The present work studies jarosite precipitation kinetics and the uptake of zinc cations in batch and continuous experiments. The distribution coefficient for zinc in continuous experiments is constant for a wide ratio of zinc over ferric ions in the solution. Addition of NH, + ions in batch experiments accelerates the conversion rate equivalent to the driving force increment. Addition of 50,2-ions above the stoichiometric ratio increases the conversion rate less then could be expected from the increase in the estimated driving force. Zinc ions tend to retard the conversion rate. An increasing reaction temperature increases the conversion rate. Below 75 ?C the conversion rate approximates zero.

Jan 1, 1990