Wei WU
,
Zai FENG
材料科学技术（英）
A systematic (Gd1-xREx)5Si4 (RE=Dy, Ho) alloys are investigated to estimate their magnetocaloric effect. The Curie points of (Gd1-x REx)Si4 alloys can tunable from 266 K to 336 K when RE=Dy, Ho; x=0~0.35 and 0~0.15, respectively, and decrease nearly linearly with increasing x. These alloys keep orthorhombic structures Ge5Sm4 and exhibit second order transition when they experience in a change magnetic field at about Curie points. The weight and voluminal magnetic entropy changes are about 3.5 J/(kg•K) and 23~29 mJ/(cm3•K) when magnetic field changes 0~2 T. The adiabatic temperatures changes (▽Tad) of these alloys at Curie points are larger than 1 K in a field change 0~1.4 T, the curve of ▽Tad is wide as that of Gd. The relative cooling power is about 0.8~0.9 J/cm3 when field changes 0~2 T, 55% of that of Gd. Comparing with Gd5(Si1-xGex)4, these alloys do not contain expensive element Ge, so that their cost are lower than the former. Because they could work at temperature region 260~340 K due to their Curie points can be tuned, which is an advantage comparing with Gd, these alloys are potential magnetic refrigerants working in a magnetic refrigerator with a low magnetic field at room temperatures.
关键词:
Magnetocaloric effect
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Wei WU
,
Lailong LUO
,
Guangwen CHU
,
Shengjun BAI
,
Haikui ZOU
,
Jianfeng CHEN
材料科学技术（英）
A novel route to prepare nanocomposites was illustrated through preparing overbased calcium petroleum sulfonate lubricating oil detergent, where the rotating packed bed (RPB) was used as reactor in place of conventional reaction vessel. The results showed that the carbonation efficiency is improved, the raw materials consumption is reduced, and the dispersibilities, sizes and morphologies of nano-sized CaCO3 particles in overbased detergent are enhanced. It is deduced reasonably that this route can be extensively applied to nanocomposites preparation in appropriate conditions and would be a platform technology in this field.
关键词:
Nanocomposite
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Wei WU
,
Xinjie LIU
,
Huimin HAN
,
Dazhi YANG
材料科学技术（英）
A modified electrolyte (CH3COOH-HClO4-A-B) for electropolishing (EP) of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy (AFM) revealed that the surface roughness (Ra) for EP sample (23.21 nm) was close to mechanical polishing (MP) sample (19.36 nm). Analysis by X-ray photoelectron spectroscopy (XPS) showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks0 solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV (vs SCE), while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.
关键词:
NiTi
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