Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature...Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature results in no grain growth. The orientation degree, microstructure, and magnetic properties were studied. Some grains＇ easy axes deviate from the orientation direction, possibly due to grain rotation during the hot pressing. By subsequent annealing, the magnetic properties were significantly enhanced. Especially, the squareness of the demagnetization curve was improved greatly.The enhancement of coercivity by annealing can be explained by an improvement of both grain boundaries and magnetic isolation, which decouples the exchange interaction between neighboring grains.展开更多
The sintering behavior of NiFe2 O4-10NiO/xNi cermet which was used as the most prospective inert anode materials for aluminum electrolysis was studied by examining the effects of raw powder particle size, sintering te...The sintering behavior of NiFe2 O4-10NiO/xNi cermet which was used as the most prospective inert anode materials for aluminum electrolysis was studied by examining the effects of raw powder particle size, sintering temperature, and the contents of Ni. The results show that fine particle size enables the powder to have high driving force for sintering. High temperature is beneficial to densification, but the ultra-high temperature does harm to the improvement of the density. The samples of NiFe2O4-10NiO/SNi has the highest relative density of 97.28 % when it is sintered at 1 350 ℃, but it decreases to 95.23 % when sintered at 1 400 ℃. Low addition of Ni has a great help to the sintering of NiFe2 O4-10NiO matrix. When the samples are sintered at 1 350 ℃ and the mass fraction of Ni is 5%, the highest relative density is gained, but the density decreases with the further increase of Ni contents. The low density of the sintered samples of NiFe2 O4-10NiO/17Ni is attributed to the high volume fraction of pores.展开更多
High niobium β-γ TiAl alloy(HNBG) was diffusion bonded using spark plasma sintering with pure Ti as interlayer. The joint microstructural evolution, growth kinetics and mechanical properties were investigated. The j...High niobium β-γ TiAl alloy(HNBG) was diffusion bonded using spark plasma sintering with pure Ti as interlayer. The joint microstructural evolution, growth kinetics and mechanical properties were investigated. The joint included three diffusion zones. The β/B2 phase formed in the Zone Ⅰ, α_(2)phase in the Zone Ⅱ, and β-Ti and α-Ti phases in the Zone Ⅲ. The thickness of β/B2 phase, the average grain size of α_(2)phase and the amount of β-Ti phase increased with the increase of bonding temperature or bonding time. The growth activation energies of β/B2 and α_(2)phases were 582 and 253 kJ/mol, respectively. The joint acquired at 1000 °C, 10 min and 10 MPa showed the maximum shear strength of 308 MPa. Fracture mainly occurred along the interfaces between Zone Ⅰ and HNBG alloy, and between Zone I and Zone Ⅱ. Fracture mechanism of the joint was characterized by brittleness rupture along the phase boundary.展开更多
The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that t...The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that the pre-sintered strontium ferrite powder is provided with a certain particle size distribution, which results in high-density magnets. The strontium ferrite particle has a laminar hexagonal structure with a size similar to ferrite single domain. Ferric oxide phase due to an incomplete solid phase reaction in the first sintering is discovered, which will deteriorate the magnetic properties of ferrite magnet. In addition, the waste ferrite magnets with needle shape arranging along C axis in good order into the powders are found, which have no negative effects on finished product quality.展开更多
动脉粥样硬化是心血管疾病重要的病理生理基础,延缓和防治动脉粥样硬化对于减少和降低心血管疾病的发病率及病死率具有重要意义。高密度脂蛋白(high density lipoprotein,HDL)通过参与介导胆固醇逆向转运(reverse cholesterol transport...动脉粥样硬化是心血管疾病重要的病理生理基础,延缓和防治动脉粥样硬化对于减少和降低心血管疾病的发病率及病死率具有重要意义。高密度脂蛋白(high density lipoprotein,HDL)通过参与介导胆固醇逆向转运(reverse cholesterol transport,RCT)在抗动脉粥样硬化的形成和进展中发挥了重要作用。Preβ-1高密度脂蛋白(prebeta-1 high density lipoprotein,Preβ-1HDL)作为HDL的一种亚类,是外周细胞移出胆固醇的最初接受体,直接参与了RCT的起始步骤,并在随后的胆固醇酯化及转运中起着重要作用。本文就Preβ-1HDL的结构、代谢及其与心血管疾病的关系作一简要综述。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51101167)the National Science and Technology Major Project,China(Grant No.2012ZX02702006-005)+2 种基金the Local Cooperation Project of Chinese Academy of Sciences(Grant No.DBSH-2011-013)the Natural Science Foundation of Zhejiang Province,China(Grant No.LQ14E010007)the Natural Science Foundation of Ningbo,China(Grant No.2014A610161)
文摘Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature results in no grain growth. The orientation degree, microstructure, and magnetic properties were studied. Some grains＇ easy axes deviate from the orientation direction, possibly due to grain rotation during the hot pressing. By subsequent annealing, the magnetic properties were significantly enhanced. Especially, the squareness of the demagnetization curve was improved greatly.The enhancement of coercivity by annealing can be explained by an improvement of both grain boundaries and magnetic isolation, which decouples the exchange interaction between neighboring grains.
基金Project(2005CB623703) supported by the National Key Fundamental Research and Development Programof China
文摘The sintering behavior of NiFe2 O4-10NiO/xNi cermet which was used as the most prospective inert anode materials for aluminum electrolysis was studied by examining the effects of raw powder particle size, sintering temperature, and the contents of Ni. The results show that fine particle size enables the powder to have high driving force for sintering. High temperature is beneficial to densification, but the ultra-high temperature does harm to the improvement of the density. The samples of NiFe2O4-10NiO/SNi has the highest relative density of 97.28 % when it is sintered at 1 350 ℃, but it decreases to 95.23 % when sintered at 1 400 ℃. Low addition of Ni has a great help to the sintering of NiFe2 O4-10NiO matrix. When the samples are sintered at 1 350 ℃ and the mass fraction of Ni is 5%, the highest relative density is gained, but the density decreases with the further increase of Ni contents. The low density of the sintered samples of NiFe2 O4-10NiO/17Ni is attributed to the high volume fraction of pores.
基金supported by the National Natural Science Foundation of China (Nos. 51871012, 52071021)Beijing Natural Science Foundation (No. 2162024)+1 种基金Fundamental Research Funds for the Central Universities, China (No. FRF-GF-20-20B)the National Key Basic Research Program of China (No. 2011CB605502)。
文摘High niobium β-γ TiAl alloy(HNBG) was diffusion bonded using spark plasma sintering with pure Ti as interlayer. The joint microstructural evolution, growth kinetics and mechanical properties were investigated. The joint included three diffusion zones. The β/B2 phase formed in the Zone Ⅰ, α_(2)phase in the Zone Ⅱ, and β-Ti and α-Ti phases in the Zone Ⅲ. The thickness of β/B2 phase, the average grain size of α_(2)phase and the amount of β-Ti phase increased with the increase of bonding temperature or bonding time. The growth activation energies of β/B2 and α_(2)phases were 582 and 253 kJ/mol, respectively. The joint acquired at 1000 °C, 10 min and 10 MPa showed the maximum shear strength of 308 MPa. Fracture mainly occurred along the interfaces between Zone Ⅰ and HNBG alloy, and between Zone I and Zone Ⅱ. Fracture mechanism of the joint was characterized by brittleness rupture along the phase boundary.
基金This work was financially supported by the Key Technologies R&D Program of Guangdong Province, China (No. 2004B10301009).
文摘The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that the pre-sintered strontium ferrite powder is provided with a certain particle size distribution, which results in high-density magnets. The strontium ferrite particle has a laminar hexagonal structure with a size similar to ferrite single domain. Ferric oxide phase due to an incomplete solid phase reaction in the first sintering is discovered, which will deteriorate the magnetic properties of ferrite magnet. In addition, the waste ferrite magnets with needle shape arranging along C axis in good order into the powders are found, which have no negative effects on finished product quality.
文摘动脉粥样硬化是心血管疾病重要的病理生理基础,延缓和防治动脉粥样硬化对于减少和降低心血管疾病的发病率及病死率具有重要意义。高密度脂蛋白(high density lipoprotein,HDL)通过参与介导胆固醇逆向转运(reverse cholesterol transport,RCT)在抗动脉粥样硬化的形成和进展中发挥了重要作用。Preβ-1高密度脂蛋白(prebeta-1 high density lipoprotein,Preβ-1HDL)作为HDL的一种亚类,是外周细胞移出胆固醇的最初接受体,直接参与了RCT的起始步骤,并在随后的胆固醇酯化及转运中起着重要作用。本文就Preβ-1HDL的结构、代谢及其与心血管疾病的关系作一简要综述。
