Dairy products are nutritious drink and can play a significant part in a healthy diet. The safety of dairy products decreases with increasing concentration of toxic compounds and environmental pollutants (especially h...Dairy products are nutritious drink and can play a significant part in a healthy diet. The safety of dairy products decreases with increasing concentration of toxic compounds and environmental pollutants (especially heavy metals). In the present study, the contamination of Al, Sn, As, Cd, Hg and Pb in dairy products (pasteurized milk, yogurt, yogurt drink, cheese) consumed in Arak, Iran, 2013 was evaluated using inductively coupled plasma mass spectrometry (ICP-SFMS) method. To meet the aim, 60 samples of 5 different brands, consisting of pasteurized milk, yogurt, yogurt drink, cheese (n = 15) were selected and analyzed for heavy metals content. 100% of the samples were positive regarding the total average and range concentration of Al, Sn, As, Cd, Hg and Pb in dairy products was 168.25 ± 92.2 (30.6 - 356.5), 5.9 ± 4 (1.1 - 16), 3.2 ± 1.95 (0.4 - 8.1), 4.55 ± 2.6 (0.6 - 10.6), 23.15 ± 10.4 (6.8 - 50.2) and 15.4 ± 8.53 (3.1 - 40.2) μg/kg, respectively. 28.3% (17 of 60 samples) of dairy products samples had lead (Pb) greater than EU limit and national Iranian standard (20 μg/kg). Statistical analysis indicated except about As in pasteurized milk and cheese there was no significant difference between products in terms of heavy metals content.展开更多
The effect of extrusion temperature and ratio on the microstructure, hardness, compression, and corrosion behavior of Mg-5Zn-1.5Y alloy were analyzed in this study. The microstructural observations revealed that the c...The effect of extrusion temperature and ratio on the microstructure, hardness, compression, and corrosion behavior of Mg-5Zn-1.5Y alloy were analyzed in this study. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg3Zn6Y and Mg3Zn3Y2 intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more dynamic recrystalized grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.展开更多
Two gating systems namely stepped and tapered runners were used to cast strip samples with different thicknesses by CO2/silicate process using sand grain sizes of AFS 151 and 171. To assess the effect of mould coating...Two gating systems namely stepped and tapered runners were used to cast strip samples with different thicknesses by CO2/silicate process using sand grain sizes of AFS 151 and 171. To assess the effect of mould coating on the properties of thin wall ductile iron, half of the moulds were coated whilst the rest were not coated. Molten metal with the carbon equivalent of 4.29% was prepared and poured at 1 450 ℃. Microstructure of the specimens was analyzed by optical and scanning electron microscopes. Count, area fraction, roundness and diameter of the graphite nodules of the samples were measured by image analyzer. Brinell hardness and tensile tests of all the samples were also conducted. The results show that by using stepped runner gating system with uncoated and coarse sand mould, roundness and count of the graphite nodules decrease whereas diameter and area fraction increase. Although fine sand and coated mould cause longer distance of molten metal travel, hardness and strength of the samples decrease.展开更多
The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by opti...The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by optical microscope,X-ray diffraction,scanning electron microscope and Feritscope,while the mechanical properties were determined by hardness and tensile tests.The results revealed that the content of retained austenite decreased by about 2% after multi-step tempering.However,the content of retained austenite increased from 3.6% to 5.1% by increasing multi-step tempering temperature.The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 ℃,while above 920 ℃,hardness and tensile strength decreased.In addition,the maximum values of hardness,ultimate and yield strength were obtained via triple tempering at 520 ℃,while beyond 520 ℃,the hardness,ultimate and yield strength decreased sharply.展开更多
基金the Ministry of Higher Education of Malaysia for the financial support (Vote No. Q.J130000.2524.04H18)Faculty of Mechanical Engineering of Universiti Teknologi Malaysia (UTM) for providing research facilities
文摘Dairy products are nutritious drink and can play a significant part in a healthy diet. The safety of dairy products decreases with increasing concentration of toxic compounds and environmental pollutants (especially heavy metals). In the present study, the contamination of Al, Sn, As, Cd, Hg and Pb in dairy products (pasteurized milk, yogurt, yogurt drink, cheese) consumed in Arak, Iran, 2013 was evaluated using inductively coupled plasma mass spectrometry (ICP-SFMS) method. To meet the aim, 60 samples of 5 different brands, consisting of pasteurized milk, yogurt, yogurt drink, cheese (n = 15) were selected and analyzed for heavy metals content. 100% of the samples were positive regarding the total average and range concentration of Al, Sn, As, Cd, Hg and Pb in dairy products was 168.25 ± 92.2 (30.6 - 356.5), 5.9 ± 4 (1.1 - 16), 3.2 ± 1.95 (0.4 - 8.1), 4.55 ± 2.6 (0.6 - 10.6), 23.15 ± 10.4 (6.8 - 50.2) and 15.4 ± 8.53 (3.1 - 40.2) μg/kg, respectively. 28.3% (17 of 60 samples) of dairy products samples had lead (Pb) greater than EU limit and national Iranian standard (20 μg/kg). Statistical analysis indicated except about As in pasteurized milk and cheese there was no significant difference between products in terms of heavy metals content.
文摘The effect of extrusion temperature and ratio on the microstructure, hardness, compression, and corrosion behavior of Mg-5Zn-1.5Y alloy were analyzed in this study. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg3Zn6Y and Mg3Zn3Y2 intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more dynamic recrystalized grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.
文摘Two gating systems namely stepped and tapered runners were used to cast strip samples with different thicknesses by CO2/silicate process using sand grain sizes of AFS 151 and 171. To assess the effect of mould coating on the properties of thin wall ductile iron, half of the moulds were coated whilst the rest were not coated. Molten metal with the carbon equivalent of 4.29% was prepared and poured at 1 450 ℃. Microstructure of the specimens was analyzed by optical and scanning electron microscopes. Count, area fraction, roundness and diameter of the graphite nodules of the samples were measured by image analyzer. Brinell hardness and tensile tests of all the samples were also conducted. The results show that by using stepped runner gating system with uncoated and coarse sand mould, roundness and count of the graphite nodules decrease whereas diameter and area fraction increase. Although fine sand and coated mould cause longer distance of molten metal travel, hardness and strength of the samples decrease.
文摘The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by optical microscope,X-ray diffraction,scanning electron microscope and Feritscope,while the mechanical properties were determined by hardness and tensile tests.The results revealed that the content of retained austenite decreased by about 2% after multi-step tempering.However,the content of retained austenite increased from 3.6% to 5.1% by increasing multi-step tempering temperature.The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 ℃,while above 920 ℃,hardness and tensile strength decreased.In addition,the maximum values of hardness,ultimate and yield strength were obtained via triple tempering at 520 ℃,while beyond 520 ℃,the hardness,ultimate and yield strength decreased sharply.
