涂料型La1-xSrxMnO3智能热控涂层的研究

以固相反应法制备了高纯度La0.8Sr0.2MnO3粉体,并以其为基料,磷酸二氢铝为粘结剂,采用涂覆工艺在铝基片上制备了涂料型La0.8Sr0.2MnO3热控涂层.采用XRD、EDS对La0.8Sr0.2MnO3粉体的成分进行了表征,用稳态卡计法测量了涂层在100~100℃温度区间内热辐射率随温度的变化,并测量了涂层的太阳吸收比.研究结果表明:粉体合成过程中,经过1200℃三次热处理制备的La0.8Sr0.2MnO3粉体纯度高,合成的粉体具有均匀的微米级粒径尺寸.通过适当调整浆料中La0.8Sr0.2MnO3粉体所占质量百分比,获得辐射率变化范围大于0.3的热控涂层,该性能与采用烧结工艺制备的La0.8Sr0.2MnO3陶瓷片材料在变温条件下的辐射率变化范围接近.该涂层在航天器热控技术中具有潜在的应用前景.     

微结构对Bi_2Sr_2Co_2O_y化合物电性能的影响

通过溶胶-凝胶法制备单相Bi2Sr2Co2Oy化合物,通过添加PEG20000和超声分散对化合物粉体微结构进行调控,采用SPS烧结得到了致密的块体.探索了微结构对Bi2Sr2Co2Oy化合物电性能的影响规律.结果表明,添加PEG20000和超声分散可以明显降低Bi2Sr2Co2Oy化合物粉体的晶粒尺寸,使烧结块体的晶粒尺寸大幅度减小,从而显著提高材料的电性能.温度为873K时,添加PEG20000并超声处理所制备样品烧结块体获得了最高ZT值0.041.     

BiMnO_3的高温高压合成及其结构和磁性研究

利用国产六面顶液压机,以Bi2O3、MnO2和Mn粉末为原料(n(Bi2O3)/n(MnO2)/n(Mn)=2∶3∶1),在高温高压条件下(3~5 GPa,600~800℃),制备了钙钛矿结构BiMnO3烧结体。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、振动样品磁强计(VSM)对烧结样品进行了测试分析,考察了烧结温度、压力对样品结构、组织形貌及磁性的影响。实验结果表明,当烧结温度为600℃时,钙钛矿结构BiMnO3晶粒开始形成,随着温度的升高,其相对含量增加,比饱和磁化强度逐渐增大,而比饱和磁化强度随着压力增大,先增大后减小;样品矫顽力随晶粒尺寸减小而减小。合成钙钛矿结构BiMnO3单相最佳实验条件为4 GPa,800℃,1 h,其居里温度为99 K,在90 K的测试温度条件下,最大的比饱和磁化强度为35 A·m2/kg,最小的矫顽力为37.6×79.6 A/m。     

La_(0.7)Sr_(0.3-x)Ca_xFe_(0.8)Co_(0.2)O_3(0.1≤x≤0.2)阴极材料溶胶-凝胶法合成与表征

以硝酸盐为原料,外加一定量PVA的溶胶-凝胶法制备La0.7Sr0.3-xCaxFe0.8Co0.2O3(LSCFC,0.1≤x≤0.2)系列阴极材料,XRD、SEM对LSCFC晶体结构、微观形貌以及与Ce0.8Sm0.2O2电解质相容性进行研究分析。实验结果表明:900℃煅烧2h,LSCFC形成了晶格膨胀的畸变钙钛矿结构,La0.7Sr0.2Ca0.1Fe0.8Co0.2O3相对LaFeO3晶胞体积膨胀率为43.85%,随着x从0.1增大到0.2,LSCFC晶胞体积膨胀率减小1.3%。La0.7Sr0.2Ca0.1Fe0.8Co0.2O3粉料与Ce0.8Sm0.2O2电解质在1200℃下烧结5h后具有良好的化学相容性。     

CaO对17Ni/(10NiO-NiFe2O4)金属陶瓷的致密化及力学性能的影响

采用冷压-烧结技术制备了CaO掺杂的17Ni/(10NiO-NiFe₂O₄)金属陶瓷惰性阳极。研究了CaO的添加量和烧结温度对17Ni/(10NiO-NiFe₂O₄)金属陶瓷的物相组成、 致密度和力学性能的影响。结果表明, CaO含量在小于5.0wt%范围内, 烧结样品由Ni、 NiO和NiFe₂O₄组成。CaO掺杂对17Ni/(10NiO-NiFe₂O₄)金属陶瓷具有明显的助烧作用。当烧结温度为1250℃时, CaO掺杂量为1.0wt%的样品致密度达到最大值97.87%, 继续增加CaO掺杂量将导致材料致密度的下降。当烧结温度从1250℃提高到1350℃时, 当CaO掺杂量小于0.5wt%时, 样品的致密度随烧结温度的提高而增加; 当CaO掺杂量大于或等于0.5wt%时, 样品的致密度随烧结温度的提高而降低。提高烧结温度和添加CaO均能促进陶瓷相晶粒长大。样品在1250℃烧结时, 其抗弯强度在CaO掺杂量为1.0wt%时达到极大值为150.66MPa。     

LSCF系钙钛矿型致密透氧膜的制备及其透氧性能

通过柠檬酸-EDTA络合法合成了不同的A位Sr取代的LSCF系钙钛矿型粉体材料La0.1Sr0.9Co0.8Fe0.2O3-δLa0.3Sr0.7Co0.8Fe0.2O3-δLa0.5Sr0.5Co0.8Fe0.2O3-δ和La0.8Sr0.2Co0.8Fe0.2O3-δ采用XRD测试手段对粉体及膜片的晶体结构进行了表征.用静压片法制备透氧膜,并测定了LSCF系钙钛矿膜的透氧量,分析了温度和A位Sr不同掺杂量等因素对膜透氧性能的影响.结果表明,该系列膜的透氧量均随着温度升高而增大,随着Sr掺杂量的增加而增大.并在850℃下对透氧膜100h透氧稳定性进行实验研究,结果表明,膜片的透氧量随时间没有明显变化,表现出良好的稳定性.     

La0.60Sr0.40-xNaxMnO3钙钛矿材料在室温附近磁电阻的温度稳定性

采用溶胶-凝胶法(sol-gel)制备了名义组分为La0.60Sr0.40-xNaxMnO3(x=0.00,0.10,0.15,0.20,0.30,0.33,0.35)的类钙钛矿型稀土锰氧化物多晶样品。发现用Na+替代部分Sr+2后,可使样品的居里温度降至室温附近,并且使样品的室温磁电阻比替代前明显增大。在1.8T的磁场作用下,样品La0.60Sr0.07Na0.33MnO3在292K时磁电阻为24.4%,比不含Na的La0.60Sr0.40MnO3增大了2.8倍;样品La0.60Sr0.25Na0.15MnO3在285K～345K温区内磁电阻保持在3.9%(±0.2%)左右,受温度影响不大,因此显著提高了样品的室温磁电阻和其温度稳定性。迄今为止还未见这类材料在室温附近具有如此宽范围和高温度上限的MR温度稳定性报道。这对于该类磁电阻材料的应用有很大意义。     

La0.8-xNdxNa0.2MnO3的磁卡效应研究

用溶胶-凝胶法制备系列样品La0.8-xNdxNa0.2MnO3(x=0.00,0.05,0.10,0.15和0.20)钙钛矿锰氧化物.研究温度范围在240～340 K、外磁场0～1T下该系列样品的居里温度和磁熵变.发现样品的居里温度TC随x增加而减小,而且x=0.20、温度为295K时,最大磁熵变△SM为1.68 J/kg·K.实验结果表明钙钛矿锰氧化物La0.8-xNdxNa0.2MnO3有可能作为室温下的磁致冷材料的候选者.     

(Bi_(0.8)La_(0.2)FeO_3)_(0.8)-(NiFe_2O_4)_(0.2)材料的合成及薄膜多铁性能

研究了Bi0.8La0.2FeO3单相陶瓷的合成,并采用脉冲激光沉积法,在SrTiO3(100)(STO)基底上,以La0.7Sr0.3MnO3(LSMO)为缓冲层,制备了(Bi0.8La0.2FeO3)0.8-(NiFe2O4)0.2(BLFO-NFO)多铁薄膜。通过X射线衍射仪和场发射扫描电子显微镜确定了BLFO-NFO多铁薄膜的显微结构,通过标准铁电测试系统(RT-66A)和振动样品磁强计(VSM)分别测试了BLFO-NFO多铁薄膜的铁电性能和铁磁性能。研究发现:BLFO-NFO多铁薄膜沿(100)方向外延生长,晶粒为70nm,它具有明显的电滞回线和磁滞回线。     

中温固体氧化物燃料电池SUS430/La0.8Sr0.2MnO3复合连接板材料制备研究

采用溶胶凝胶和等离子喷涂的方法,制备了SUS430/La0.8Sr0.2MnO3复合连接板材料.通过TG、IR和XRD分析了La0.8Sr0.2MnO3凝胶烧结过程;采用SEM、四探针法和氧化增重法分别研究了SUS430/La0.8Sr0.2MnO3复合连接板材料的形貌、电子导电能力和高温抗氧蚀能力.经比较研究发现,溶胶凝胶和等离子喷涂都可以制备出高性能的SUS430/La0.8Sr0.2MnO3复合连接板材料,陶瓷涂层致密度分别达到了94.6%和97%;且腐蚀速率由SUS430材料的104.93μg2·cm-4·h-1分别降低到26.91μg2·cm-4·h-1和20.39μg2·cm-4·h-1,在800C下它们的电导率分别为11.17s·cm-1和12.66s·cm-1.     

Synthesis and characterization of pure and doped (Na, Ca, Sr) nanograined LaMnO3 magnetoresistive ceramics

Pure and Na, Ca, and Sr doped lanthanum manganites (LaMnO3, La0.85Na0.15MnO3, La0.7Ca0.3 MnO3, La0.7Sr0.3MnO3) were prepared in form of bulk nano-structured materials through a two-step process. Nanometric powders were synthesized by the Pechini method and subsequently densified by Spark Plasma Sintering at 1273 K for 5 minutes under a pressure of 140 MPa. The method allowed the preparation of single phase manganites with a theoretical density above 98% together with a very limited growth of the grain size. Grain sizes below 70 nm were obtained for all materials except La0.85Na0.15MnO3 which showed a much larger grain size. Curie temperatures (Tc) and magnetoresistivity properties of the samples were measured by a Superconducting Quantum Interference Device (SQUID). The decrease in the resistivity below Tc occurred in a much wider range of temperature compared to ceramics having micron-size grains.     

煅烧温度对La_(0.6)Sr_(0.4)MnO_3晶体结构及电磁性能的影响

采用传统固相反应法在不同烧结温度下制备了La_(0.6)Sr_(0.4)MnO_3样品,通过X射线衍射仪(XRD)和扫描电镜显微镜(SEM)对样品进行了物相结构和微观组织分析,比较了不同烧结温度下样品的烧结性、介电性和铁磁性能。研究结果表明,当烧结温度从1100℃增加到1200℃时,La_(0.6)Sr_(0.4)MnO_3样品的介电损耗呈降低趋势,介电常数数值呈增加趋势,并在测量频率范围内显示负值。随着烧结温度的增加,La_(0.6)Sr_(0.4)MnO_3样品的铁磁性呈现先上升后下降的趋势。当烧结温度为1150℃时,其饱和磁化强度达到最大,为37.80A·m~2·kg~(-1)。说明可以通过改变煅烧温度来有效调节晶粒尺寸,从而改进La_(0.6)Sr_(0.4)MnO_3样品的介电性能和铁磁性能。     

Sr~(2+)掺杂及非化学计量LaFeO_3的溶剂热制备及光催化性能

利用简单的溶剂热法制备LaFeO_3、La_(0.8)Sr_(0.2)FeO_(3-δ)以及非化学计量的La_(0.8)Sr_(0.2)FeO_(3-δ)(x=0.97,1.03)纳米颗粒。采用XRD、TEM、UV-Vis、XPS等手段对样品的形貌和结构进行表征,以孔雀石绿(MG)光降解为模型反应,在最大吸收波长下(616.9nm)考察材料的光催化性能。结果表明:Sr~(2+)的掺入减小了晶粒尺寸,致使晶体产生晶格畸变并形成氧空位V··O,抑制电子-空穴重组,增大量子效率;掺入Sr~(2+)并改变非化学计量,使得催化剂在可见光区域有较强的光吸收,比表面积增大,其中(La_(0.8)Sr_(0.2))1.03FeO_(3-δ)的比表面积最大(20.164 4m2/g),可见光降解效率也最高(83.8%)。Sr~(2+)掺杂及非化学计量LaFeO_3的可见光催化活性均高于纯LaFeO_3。     

铬酸锶镧材料的制备和性能研究

利用Ｇｌｙｃｉｎｅ－Ｎｉｔｙｒａｔｅ－Ｐｒｏｃｅｓｓ合成了Ｌａ１－ｘＳｒｘＣｒＯ３－δ粉体材料,并采用ＸＲＤ,ＤＴＡ／ＴＧ、ＴＥＭ和粒度分析等方法,对粉体性能进行了研究。用Ａｒｃｈｉｍｅｄｅｓ法,直流四探针法和ＸＲＤ分别研究了烧结体的烧结性能,电性能和相结构。     

Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体的合成及气敏性质研究

采用复合碱媒介法(CHM),在合成BaMnO3和Ba0.5Sr0.5MnO3的基础上,以Sr(NO3)2、BaCO3以及MnO2和TiO2为原料,在200℃、24h的生长条件下,用20%的Sr离子替代20%的Ba离子,用50%的Ti离子替代50%的Mn离子成功合成了Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体。采用XRD、SEM及EDS对产物的晶相、形貌和成分进行了分析,对Ba0.8Sr0.2Ti0.5Mn0.5O3制作的电极进行了气敏性质的测定。     

Nanostructured La(Sr)CrO3 through gel combustion: sintering and electrical behavior

Nanostructured La(Sr)CrO3 (LSC) powders was prepared through glycine-nitrate gel combustion process. It was shown for the first time that the use of relatively inexpensive CrO3 as a starting material for chromium has a potential for the bulk preparation of sinter-active LSC powder. As-prepared powder when calcined at 700 degrees C resulted in LSC along with a small amount of SrCrO4 as a secondary phase. The powder was found to be composed of soft agglomerates with a particle size of approximately 70-270 nm. The average agglomerate size was found to be 0.95 microm. The cold pressing and sintering of the LSC powder at 1450 degrees C resulted in mono-phasic La0.8Sr0.2CrO3 with 94% of its theoretical density. This is the lowest sintering temperature ever reported for La0.8Sr0.2CrO3. The conductivity of the sintered La0.8Sr0.2CrO3 at 1000 degrees C was found to be approximately 18 S cm(-1).     

Stabilization of Ferromagnetic Order in La(0.7)Sr(0.3)MnO(3)-SrRuO(3) Superlattices

The study of spatially confined complex oxides is of wide interest, since correlated electrons at interfaces might form exotic phases. Here La(0.7)Sr(0.3)MnO(3)/SrRuO(3) superlattices with coherently grown interfaces were studied by structural techniques, magnetization, and magnetotransport measurements. Magnetization measurements showed that ferromagnetic order in ultrathin La(0.7)Sr(0.3)MnO(3) layers is stabilized in the superlattices down to layer thicknesses of at least two unit cells. This stabilization is destroyed, if the ferromagnetic layers are separated by two unit cell thick SrTiO(3) layers. The resistivity of the superlattices showed metallic behavior and was dominated by the conducting SrRuO(3) layers, the off-diagonal resistivity showed an anomalous Hall effect from both SrRuO(3) and La(0.7)Sr(0.3)MnO(3) layers. This shows that the La(0.7)Sr(0.3)MnO(3) layers are not only ferromagnetic but also highly conducting; probably a conducting hole gas is induced at the interfaces that stabilizes the ferromagnetic order. This result opens up an alternative route for the fabrication of two-dimensional systems with long-range ferromagnetic order.     

多孔 La0.6Sr0.4Co0.2Fe0.8O3-的制备及表征

多孔La0.6Sr0.4Co0.2Fe0.8O3-陶瓷具有一定的强度、良好的透气和电传导性能,可用于中温SOFC阴极支撑体和氧分离膜活性支撑体. 本文用固相反应法制备了多孔La0.6Sr0.4Co0.2Fe0.8O3-陶瓷. 考察了烧结条件、成型压力和有机添加剂量对孔隙率和孔径的影响. 研究发现气体渗透率随孔隙率线性增长,电导率随孔隙率的增大而下降,并满足关系式=0(1-P)3.1.     

Effect of annealing temperature on the electromagnetic properties of La0.8Sr0.2MnO3 prepared by sol–gel process

Journal of Materials Science: Materials in Electronics - La0.8Sr0.2MnO3 (LSMO) powder was prepared using the sol–gel method and treated at different annealing temperatures (AT), and the...