Metals obtain optimum conditions of metallurgical and physical properties through a heat treatment. Brass is one of the copper alloys which has many applications in everyday life and in the industry. Brass is one of t...Metals obtain optimum conditions of metallurgical and physical properties through a heat treatment. Brass is one of the copper alloys which has many applications in everyday life and in the industry. Brass is one of the copper alloys which has many applications in everyday life and the industry. In this work, the influence of the precipitation heat treatment temperature on the metallurgical microstructure, structure, thermal properties, and microhardness of an alpha brass is analyzed. Samples were heat treated by precipitation for 2 h at 300°C, 400°C, 500°C, 600°C, and 700°C. The best mechanical properties were found at 500°C of precipitation heat treatment temperature. Specimens were characterized by scanning electron microscopy, X-ray diffraction, Vickers microhardness, photothermal radiometry, and photoacoustic to study the thermal diffusivity and conductivity, as well as the heat capacity. The inverse of the full width at the half maximum analysis showed that the crystallinity decreased as the precipitation heat treatment temperature increased. Metallurgical microstructure and microhardness were correlated to the precipitation heat treatment temperatures to determine the effect on the metallurgical and mechanical properties, as well as the effect on the thermal properties of alpha brass.展开更多
<p> The concentrations and distribution of naturally occurring radionuclides <span><span><span><span>(</span><sup><span>238</span></sup><span>U, </s...<p> The concentrations and distribution of naturally occurring radionuclides <span><span><span><span>(</span><sup><span>238</span></sup><span>U, </span><sup><span>235</span></sup><span>U, </span><sup><span>234</span></sup><span>U, </span><sup><span>230</span></sup><span>Th, </span><sup><span>226</span></sup><span>Ra, </span><sup><span>210</span></sup><span>Pb, </span><sup><span>232</span></sup><span>Th, </span><sup><span>228</span></sup><span>Ra, and </span><sup><span>40</span></sup><span>K)</span></span></span></span><span><span><span><span> were determined by alpha and gamma spectrometry in soil and sediments collected from Luilu and Dilala rivers located in the mining district of Kolwezi (Lualaba Province) of the Democratic Republic of the Congo. The average concentrations of </span><sup><span>238</span></sup><span>U and </span><sup><span>226</span></sup><span>Ra in the analyzed samples were 5</span></span></span></span><span><span><span> </span></span></span><span><span><span>-</span></span></span><span><span><span> </span></span></span><span><span><span>10 times higher than the world average values for soil provided by the </span></span></span><span><span><span>United Nations Scientific Committee on the Effects of Atomic Radiation. However,</span></span></span><span><span><span><span> the average concentrations of </span><sup><span>232</span></sup><span>Th were found similar to the world average. In both river basins, artisanal mining activities and</span></span></span></span><span><span><span> mineral washing sites displayed the higher concentration values of radionuclides. The mean values of health risk indices calculated for those sites were found sig</span></span></span><span><span><span>nificantly higher compared to world average levels. Radiation protection measures seem needed to ensure the radiation safety of local populations.</span></span></span> </p> <p> <span><span><span><br /> </span></span></span> </p> <p> <span style="font-size:16px;"><strong>Graphical Abstract</strong></span> </p> <p> <span><展开更多
文摘Metals obtain optimum conditions of metallurgical and physical properties through a heat treatment. Brass is one of the copper alloys which has many applications in everyday life and in the industry. Brass is one of the copper alloys which has many applications in everyday life and the industry. In this work, the influence of the precipitation heat treatment temperature on the metallurgical microstructure, structure, thermal properties, and microhardness of an alpha brass is analyzed. Samples were heat treated by precipitation for 2 h at 300°C, 400°C, 500°C, 600°C, and 700°C. The best mechanical properties were found at 500°C of precipitation heat treatment temperature. Specimens were characterized by scanning electron microscopy, X-ray diffraction, Vickers microhardness, photothermal radiometry, and photoacoustic to study the thermal diffusivity and conductivity, as well as the heat capacity. The inverse of the full width at the half maximum analysis showed that the crystallinity decreased as the precipitation heat treatment temperature increased. Metallurgical microstructure and microhardness were correlated to the precipitation heat treatment temperatures to determine the effect on the metallurgical and mechanical properties, as well as the effect on the thermal properties of alpha brass.
文摘<p> The concentrations and distribution of naturally occurring radionuclides <span><span><span><span>(</span><sup><span>238</span></sup><span>U, </span><sup><span>235</span></sup><span>U, </span><sup><span>234</span></sup><span>U, </span><sup><span>230</span></sup><span>Th, </span><sup><span>226</span></sup><span>Ra, </span><sup><span>210</span></sup><span>Pb, </span><sup><span>232</span></sup><span>Th, </span><sup><span>228</span></sup><span>Ra, and </span><sup><span>40</span></sup><span>K)</span></span></span></span><span><span><span><span> were determined by alpha and gamma spectrometry in soil and sediments collected from Luilu and Dilala rivers located in the mining district of Kolwezi (Lualaba Province) of the Democratic Republic of the Congo. The average concentrations of </span><sup><span>238</span></sup><span>U and </span><sup><span>226</span></sup><span>Ra in the analyzed samples were 5</span></span></span></span><span><span><span> </span></span></span><span><span><span>-</span></span></span><span><span><span> </span></span></span><span><span><span>10 times higher than the world average values for soil provided by the </span></span></span><span><span><span>United Nations Scientific Committee on the Effects of Atomic Radiation. However,</span></span></span><span><span><span><span> the average concentrations of </span><sup><span>232</span></sup><span>Th were found similar to the world average. In both river basins, artisanal mining activities and</span></span></span></span><span><span><span> mineral washing sites displayed the higher concentration values of radionuclides. The mean values of health risk indices calculated for those sites were found sig</span></span></span><span><span><span>nificantly higher compared to world average levels. Radiation protection measures seem needed to ensure the radiation safety of local populations.</span></span></span> </p> <p> <span><span><span><br /> </span></span></span> </p> <p> <span style="font-size:16px;"><strong>Graphical Abstract</strong></span> </p> <p> <span><
