彭 能,蘇玉長,肖方明

1.中南大學(xué)材料科學(xué)與工程學(xué)院,湖南長沙410083;2.廣東省工業(yè)技術(shù)研究院(廣州有色金屬研究院),廣東廣州510650

La-Mg-Ni系儲氫合金儲氫性能研究

彭 能1,2,蘇玉長1,肖方明2

1.中南大學(xué)材料科學(xué)與工程學(xué)院,湖南長沙410083;2.廣東省工業(yè)技術(shù)研究院(廣州有色金屬研究院),廣東廣州510650

采用快淬法制備了不同鎂含量的La-M g-Ni系儲氫合金,并研究了La-M g-Ni系儲氫合金的儲氫特性.結(jié)果表明,La-Mg-Ni系儲氫合金主要由LaNi5和LaNi3兩相組成;隨著鎂含量的增加,儲氫合金的吸放氫平臺壓力降低,吸氫量提高;與化學(xué)計量比儲氫合金相比,非化學(xué)計量比的儲氫合金平臺壓力提高;在1173 K熱處理4 h后,儲氫合金具有較好的吸/放氫平臺性能,其吸氫量可達(dá)1.59%.

快淬法;La-M g-Ni系儲氫合金;儲氫性能

商品化AB5型儲氫合金儲氫量低、生產(chǎn)成本較高,儲氫容量的提升空間不大,從而限制了其在燃料電池中的應(yīng)用.而AB3型La-M g-Ni系合金具有儲氫量大、放電容量高、活化快等優(yōu)勢,近年來成為各高校、科研院所及企業(yè)的研究熱點[1-7].但是該合金的相關(guān)研究仍處于實驗階段,尚存在放電容量不穩(wěn)定、循環(huán)壽命差等問題.我們采用常規(guī)真空負(fù)壓快淬爐,通過添加覆蓋劑,選擇合適的熔煉工藝條件,解決了熔煉過程中鎂大量揮發(fā)導(dǎo)致合金成分不穩(wěn)定的問題,獲得了成分均勻的La-M g-Ni系納米晶儲氫合金.在前期工作[8-9]的基礎(chǔ)上,本文研究了鎂含量及熱處理工藝對合金儲氫性能的影響.

1 實驗部分

1.1 合金粉的制備

實驗用原材料為La,Ce,Ni,Co,M n,A l和M g,其純度均大于99.9%.在氬氣保護(hù)的快淬爐中,通過添加覆蓋劑對原材料進(jìn)行熔煉,合金液保溫一段時間后經(jīng)冷卻銅輥制得0.05～1.5 mm厚的合金片.在850～1020℃熱處理后,采用機械球磨制得一系列La-M g-Ni儲氫合金.

1.2 性能測試

采用日本 RIN T-1100型 X射線衍射儀(Cu Kα靶)分析儲氫合金的相結(jié)構(gòu).采用上海冶金所的 YJ-1全自動 P-C-T測試儀對合金的吸放氫性能進(jìn)行表征.

2 結(jié)果與討論

2.1 合金的相組成

圖1為不同M g含量La-M g-Ni系儲氫合金的X-射線衍射圖.圖 1表明,La-M g-Ni合金主要由LaNi5和LaNi3兩相組成;當(dāng)鎂含量增加時,LaNi5相減少,LaNi3相增加,說明鎂能夠促進(jìn)LaNi3相的形成[10].此外,由于 M g原子半徑(1.72×10-10mm)小于La原子半徑(2.74×10-10mm),當(dāng) M g替代A側(cè)的La后,導(dǎo)致晶軸收縮,晶胞體積變小.這一點可以由隨著鎂含量不斷增加,合金的特征峰逐漸向高角度方向偏移的結(jié)果來證實.

圖1 儲氫合金的XRD圖Fig.1 XRD pattern of hydrogen sto rage alloy

2.2 La-Mg-Ni系儲氫合金的儲氫性能

2.2.1 鎂含量對合金儲氫性能的影響

不同鎂含量的La-M g-Ni系儲氫合金 PCT曲線如圖2所示.由圖2可知,隨著鎂含量提高,儲氫合金的吸放氫平臺壓力降低,吸氫量提高.M g含量較高時,儲氫合金平臺壓力較低,這是由于生成的氫化物過于穩(wěn)定使部分氫無法釋放出來,導(dǎo)致儲氫合金放氫量減少,平臺區(qū)域變窄.當(dāng) M g摩爾分?jǐn)?shù)為0.3時,儲氫容量較高,其吸氫量可達(dá)到1.54%.

圖2 在298K不同鎂含量儲氫合金的PCT曲線Fig.2 PCT curve of hydrogen sto rage alloys w ith different Mg content at 298K

2.2.2 非化學(xué)計量比對儲氫合金儲氫性能的影響

對儲氫材料進(jìn)行升溫真空脫氣后及吸放氫活化2次后,在室溫(298 K)下測試其吸放氫性能,其吸放氫PCT曲線如圖3所示.從圖3可知,與化學(xué)計量比的La0.7M g0.3Ni3.5合金相比,兩種非化學(xué)計量比的儲氫合金平臺壓力提高.其中La0.7M g0.3Ni3.25儲氫合金具有較好的平臺性能,平臺壓力較高,吸氫量達(dá)到1.45%.

圖3 在298K非化學(xué)計量比儲氫合金的吸放氫性能Fig.3 The hydrogen absorp tion and desorp tion p roperties of non-stoichiometric hydrogen storage alloy at 298K

2.2.3 熱處理對儲氫合金儲氫性能的影響

將La0.7M g0.3Ni3.5儲氫合金在1173 K熱處理4 h后,在室溫(298 K)下測試儲氫合金的吸/放氫性能,其吸放氫 PCT曲線如圖4所示.由圖4可知,經(jīng)熱處理后,La0.7M g0.3Ni3.5儲氫合金的平臺壓力和平臺性能提高,吸氫量達(dá)到1.59%.

3 結(jié) 論

采用快淬法制備了不同鎂含量的La-M g-Ni系儲氫合金,該合金主要由LaNi5和LaNi3兩相組成.隨著鎂含量的增加,儲氫合金的吸放氫平臺壓力降低,吸氫量提高.與化學(xué)計量比儲氫合金La0.7M g0.3Ni3.5相比,非化學(xué)計量比的儲氫合金平臺壓力提高.La0.7M g0.3Ni3.5儲氫合金在1173 K熱處理4 h后具有較好的吸/放氫平臺性能,其吸氫量可達(dá)到1.59%.

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Hydrogen storage properties of La-Mg-Ni hydrogen storage alloys

PENG Neng1,2,SU Yuchang1,XIAO Fangming2
1.College of M aterial Science and Engineering,Central South University,Changsha 410083,China;2.Guangdong Genera l Research Institute of Industrial Technology(Guangzhou Research Institute of N onferrous M etals),Guangzhou 510650,China

La-M g-Ni hydrogen storage alloys w ith different M g content were p repared by rapid quenching method and hydrogen storage p ropertiesof these alloyswere investigated.XRD results showed that theses alloyswere mainly composed of LaNi5and LaNi3;w ith the increase of M g content,the hydrogen absorption/desorp tion p lateau p ressure of the alloys lowered and their hydrogen absorp tion capacity increased;p lateau p ressure of the non-stoichiometric hydrogen sto rage alloys increased compared to the stoichiometric hydrogen sto rage alloy;after 4 hoursof heat treatment at 1173 K,the hydrogen sto rage alloy had good absorp tion/desorp tion p lateau performance w ith hydrogen abso rp tion capacity up to 1.59%.

rapid quenching method;La-M g-Ni hydrogen storage alloy;hydrogen storage p roperties

TG139.7

A

1673-9981(2011)02-0121-04

2010-11-24

彭能(1980—),男,湖南婁底人,工程師,碩士研究生.