Xiaoliang SHI
,
Gangqin SHAO
,
Xinglong DUAN
,
Runzhang YUAN
,
null
,
null
,
null
材料科学技术（英）
Nanocrystalline tungsten carbide-cobalt (WC-Co) composite powders produced through spray thermal decomposition-continuous reduction and carburization technology were used to prepare Φ3.25 mm×38 mm ultrafine tungsten carbide-cobalt (WC-Co) cemented carbide rods through vacuum sintering plus sinterhip technology. The microstructure, Vickers hardness, density and Rockwell A hardness (HRA), transverse rupture strength (TRS), saturated magnetization and coercivity force were tested. The results show that the average grain size of the sintering body prepared through vacuum sintering plus sinterhip technology was 430~nm; transverse rupture strength (TRS) was 3850 MPa; Vickers hardness was 1890 and Rockwell A hardness of sintering body was 93. High strength and high hardness ultrafine WC-Co cemented carbide rods used to manufacture printed circuit board (PCB) drills were obtained.
关键词:
Nanocrystalline
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null
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null
,
null
Jiansen NI
,
Hui XU
,
Mingyuan ZHU
,
Qiang LI
,
Bangxin ZHOU
,
Yu
,
a DON
材料科学技术（英）
Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 bonded magnets were prepared by melt-spun and subsequent heat treatment. Magnetic properties of Br=0.68 T, JHc=716 kA/m, (BH) max=77 kJ/m3 were achieved. The addition of Cr element shows to be significantly advantageous in reducing grain size and increasing the intrinsic coercivity.
关键词:
null
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Nanocrystalline
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Melt-spinning
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Ma
Ruiting MA
材料科学技术（英）
Nanocrystalline nickel zinc ferrite powders (NixZn1-xFe2O4, A for x=0, B for x=0.2, C for x=0.5, D for x=0.8 and E for x= 1) were synthesized by polyacrylamide gel method. X-ray diffraction (XRD), transmission electron microscopy (TEM) and wave-guide were used to characterize the composition. The XRD results show that the dried gel powders are amorphous, and the characteristic peaks of the spinel Ni0.5Zn0.5Fe2O4 appear after the gel is calcined at 400℃ for 1 h. When the calcining temperatures are 600 and 800℃, the average grain sizes are identified by TEM to be 10 and 30 nm, respectively. The NixZn1-xFe2O4 powders have both dielectric loss and magnetic loss in the frequency range of 8.2–11.0GHz. With the increase of Ni2+ ions content, the dielectric parameters (ε′) and permeability (u′) of the NixZn1-xFe2O4 powders decrease while the dielectric loss (ε"), magnetic loss (u") and the reflection loss increase.
关键词:
Nanocrystalline
,
ferrite
,
electromagnetic
Jianxin WANG
,
Qin WANG
,
Xianping WANG
,
Chun LI
,
Qianfeng FANG
材料科学技术（英）
A cost-effective technique, including nanocrystalline powder preparation using a modified Pechini method and a two-step low-temperature sintering route, was developed for the synthesis of high performance La2Mo2O9-based oxide-ion conductors. The optimum parameters of the compaction pressure, the first step and the second step sintering temperatures for the synthesis of fine grained, high density and uniform La2Mo2O9-based oxide-ion conductors were determined by a series of sintering experiments. High density and uniform sintered La2Mo2O9 samples with average grain size from 0.8 to 5 μm and La1.96K0.04Mo2O8.96 sample with average grain size as small as 500 nm were synthesized by using this cost-effective method. The impedance measurement results show that the as-fabricated La2Mo2O9-based ceramics possess much higher ionic conductivity than that obtained by solid state reaction method. It is found that in the range of 0.8{5 μm the grain size of dense La2Mo2O9 samples prepared from the nanocrystalline powders has little influence on their conductivities.
关键词:
Oxide ion conductor
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null
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null
,
null
Ruiting MA
材料科学技术（英）
Nanocrystalline Co0.5Zn0.5Fe2O4 ferrite was synthesized by polyacrylamide gel method. The electromagnetic and microwave absorption properties of the ferrite were investigated. The results indicated that calcining temperature of the ferrite had a significant influence on the effective properties of the ferrite. When the calcining temperature was 500, 600 and 700℃, the average size of particles was 10, 30 and 80 nm, respectively. The dielectric loss (ε") and magnetic loss (u") of the ferrite was around 0.65 and 0.29 at 8.2 GHz, respectively. Microwave absorption properties of the ferrites were simultaneously influenced due to the strong correlation between reflection loss and electromagnetic parameters of the ferrite.
关键词:
Polyacrylamide gel
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null
,
null
