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Mississauga, Canada

Zhao C.,McMaster University | Jain M.K.,McMaster University | Bruhis M.,McMaster University | Lawcock R.,Gates Canada Inc.
Powder Technology

A major advantage of the powder metallurgical (P/M) manufacturing process is its ability to shape powder directly into a final component with a primary goal of a high quality, homogeneity of density and mechanical properties and productivity. In this research, powder die filling, powder transfer and powder compaction process have been studied in succession using a novel experimental set-up that utilizes a high strength transparent wall section to observe and record the particle movement and powder compaction during the entire sequence leading up to the formation of a green part. The natural powder pattern itself, as observed from the transparent wall section, is utilized for obtaining full-field displacement and strain measurement. The test set-up and the strain measurement technique offer a means of quickly obtaining density distribution data in select cases. In addition to the above, several powder flow characteristics during die filling, powder transfer and powder compaction under a range of test conditions have been noted through a series of high-speed photographic recordings. The observations reveal increased porosity in the die wall region due to friction and formation of shear bridges during powder transfer stages during suction filling. Spatial density data from optical strain measurements in the top, middle and bottom regions of the die are consistent with similar bulk density measurements from mass and volume of the 3 regions. © 2011 Elsevier B.V. Source

Solomon I.,University of Galati | Solomon I.,Gates Canada Inc. | Solomon N.,Stefan Cel Mare University of Suceava
Canadian Metallurgical Quarterly

This paper presents the influence of temperature variation and iron substitution with Co on the structure, electrical and magnetic properties of amorphous Fe75-xCoxCr1B7Si 17 alloys (x=1, 4, 7 and 10 at%), obtained by the melt-spinning technique. The amorphous structure of tested materials was examined by X-ray diffraction (XRD), Mössbauer spectroscopy and scanning electron microscopy (SEM) methods. The thermal behaviour associated with the crystallization temperature of the glassy samples was measured using differential scanning calorimetry (DSC). The electrical resistivity of the amorphous alloys was measured between -160 and 750°C under neutral atmosphere. The electrical and magnetic properties were determined by Wheatstone bridge and by the Bitter technique and the Ferrotester method, respectively. Experimental results confirmed the utility of the applied investigation methods and the influence of the Co content and annealing process on the structure, electrical and magnetic properties of examined amorphous alloys. The studied amorphous alloys are soft magnetic materials and exhibit excellent electrical properties. © Canadian Institute of Mining, Metallurgy and Petroleum. Source

Solomon I.,University of Galati | Solomon I.,Gates Canada Inc. | Solomon N.,Stefan Cel Mare University of Suceava
Canadian Metallurgical Quarterly

The aim of this paper was to investigate the effect of increasing cobalt content on the corrosion resistance of the Fe-Co-Cr-B-Si alloys in dilute mineral acids. The corrosion rates in 0.5N HCl, 1N HCl and IN H 2SO4 significantly decrease with an increase in Co content. The high corrosion resistance of the Fe-Co-Cr-B-Si alloys is also due to the formation of a chromium-enriched passive film. Generally, the corrosion resistance of chromium-bearing alloy is improved by alloying with various metalloids but it is lowered by the addition of boron and silicon. The corrosion behaviour of the amorphous Fe75-xCoxCr1B 7Si17 (where x=1, 4, 7 and 10 at% Co) alloys obtained by the melt-spinning technique was studied using the gravimetric method. The best results were obtained with Fe65Co10Cr1B 7Si17 alloy. The studied amorphous alloy ribbons exhibit not only excellent physical properties which are useful for many electric and magnetic applications such as magnetic sensors, power transformers, etc., but also a very good corrosion resistance which extend their application domain. © Canadian Institute of Mining, Metallurgy and Petroleum. Source

Kraemer J.D.,Georgetown University | Cabrera O.A.,Georgetown University | Singh J.A.,Center for the Programme of Research in South Africa | Singh J.A.,Gates Canada Inc. | And 4 more authors.
International Journal of Tuberculosis and Lung Disease

In low-income countries, tuberculosis (TB) control measures should be guided by ethical concerns and human rights obligations. Control programs should consider the principles of necessity, reasonableness and effectiveness of means, proportionality, distributive justice, and transparency. Certain measures - detention, infection control, and treatment to prevent transmission - raise particular concerns. While isolation is appropriate under certain circumstances, quarantine is never an acceptable control measure for TB, and any detention must be limited by necessity and conducted humanely. States have a duty to implement hospital infection control to the extent of their available resources and to provide treatment to health care workers (HCWs) infected on the job. HCWs, in turn, have an obligation to provide care unless conditions are unreasonably and unforeseeably unsafe. Finally, states have an obligation to provide adequate access to treatment, as a means of preventing transmission, as broadly as possible and in a non-discriminatory fashion. Along with treatment, states should provide support to increase treatment adherence and retention with respect for patient privacy and autonomy. Compulsory treatment is almost never acceptable. Governments should take care to respect human rights and ethical obligations as they execute TB control programs. © 2011 The Union. Source

Zhang B.,McMaster University | Jain M.,McMaster University | Zhao C.,McMaster University | Bruhis M.,McMaster University | And 2 more authors.
Powder Technology

Theory and experimental calibration of density dependent modified Drucker-Prager/Cap (DPC) model are presented by using a novel instrumented cubic die in powder compaction tests. The cubic die is designed for directly determining the loading and unloading forces and displacements of powder compact inside the die in compaction and transverse directions without any additional calibration. The cap surface parameters and elastic properties are characterized by fitting stress and strain curves recorded during loading and unloading at different green density values and the plastic material parameters for failure surface are obtained by additional radial and axial compressive tests. The experimental data is subsequently used in the simulation of cubic die compaction to verify the results from the density dependent modified DPC model. © 2010 Elsevier B.V. Source

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