Ti对Gd1-xTix合金晶体结构和磁热效应的影响

用真空电弧熔炼炉制备Gd1-xTix(x=0.0005,0.001,0.002)系列合金,并对其晶体结构、居里温度、绝热温变进行研究.室温XRD分析发现:该系列合金仍保持与纯Gd相同的相结构;材料的居里温度比纯Gd的居里温度稍微降低;其最大绝热温变△Tad值有所上升;在低磁场下,Gd1-xTix系合金可以部分替代Gd作为室温磁制冷材料.     

H原子对Gd5Si1.72Ge2.28合金低场磁性能和磁熵变的影响

为了提高Gd5(SixGe1-x)4(0.2<x≤0.5)系合金的居里温度同时保持该类合金的大磁热效应,使用商业蒸馏Gd为原材料,用非自耗电弧炉熔炼出Gd5Si1.72Ge2.28母合金,然后将该合金粉末在贮氢合金用PCT设备上进行吸氢,获得了Gd5Si1.72Ge2.28Hx合金.磁性测量结果表明,H原子的引入,使合金的居里温度从246 K提高到297 K;同时,合金在居里温度附近的最大磁熵变从-7. 6 J*kg-1*K-1下降到-4.2 J*kg-1K-1(0～1.5 T),但与同纯度的Gd相比,Gd5Si1.72Ge2.28Hx合金的磁熵变仍然比Gd的磁熵变(-3.1 J*kg-1*K-1,0～1.5 T)高出35%.     

(Gd_(1-x)R_x)_5Si_4(R=Dy、Ho)磁制冷材料的晶体结构以及居里温度研究

为了探索室温附近温度范围内的磁制冷材料 ,作者研究了 (Gd1 xDyx) 5Si4(x =0 1、0 2、0 3、0 3 5 )和 (Gd1 xHox) 5Si4(x =0 0 5、0 15、0 2 5 )系列合金的晶体结构、居里温度。结果发现 :该系列合金仍保持Gd5Si4的Ge4Sm4正交型结构 ;随着x量的增加 ,样品的晶格常数逐渐减小 ,居里温度TC在 3 40K～ 2 60K连续可调 ,并呈线性减小趋势 ;改变R的含量可以得到单一的居里温度值 ,该值和计算值基本吻合     

铸态及快淬态Mm(NiMnSiAlCu)4.3Co0.6-xFex(x=0～0.4)电极合金的电化学性能

用XRD,TEM及SEM测试了稀土基AB5型贮氢合金Mm(NiMnSiAlCu)4.3Co0.6-xFex(x=0～0.4) 的微观结构,并全面测试了合金在铸态及快淬态下的电化学性能.研究结果表明,铸态合金为双相结构,主相为CaCu5型相,还有少量Ce2Ni7相,经快淬处理后,第二相减少.对铸态合金,随Fe含量的增加,合金的容量有所降低,循环稳定性得到改善.对快淬态合金,当铁含量大于0.2时,合金的容量急剧下降,而循环稳定性大幅度增加.这主要是由于铁的加入使合金的微观结构发生了变化.     

MA制备GdSiGeDy合金系室温磁制冷性能研究

机械合金化(MA)是一种材料固态非平衡加工新技术.本文主要探讨稀土元素Dy在机械合金化工艺条件下对磁制冷合金GdSiGe磁熵变的影响,发现用机械合金化制备的GdSiGeDy合金系室温磁制冷材料不仅有光滑的磁熵变曲线,而且研究表明,由于元素Dy的加入在磁熵变达到单质Gd的两倍情况下大量减少使用昂贵元素Ge的结果,具有明显经济效益.     

Gd_(60-x)Ho_xCo_(20)Al_(20)非晶合金的磁热效应研究

本文利用单辊熔体快淬法成功制备了Gd_(60-x)Ho_xCo_(20)Al_(20)(x=0-40)非晶合金,并系统研究了其磁性和磁热效应。研究发现:通过Ho替代Gd可实现相变温度在44~112K宽温区内连续可调,并在各自相变温度附近发生铁磁(亚铁磁)—顺磁二级相变。在0~5T外磁场变化下,Gd_(60-x)Ho_xCo_(20)Al_(20)非晶合金磁熵变峰值分别为7.91(x=0),9.22(x=10),8.85(x=20),8.56(x=30),9.83(x=40)J·kg-1·K-1,Gd30Ho30Co20Al20和Gd20Ho40Co20Al20非晶合金的半高宽分别为~60K和~70K,磁制冷效率为~590和~599J·kg-1,有望应用于液氮温区制冷。     

反应温度对LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2组织结构及电化学性能的影响

在共沉淀法合成Ni0.4Co0.2Mn0.4(OH)2的基础上制备了锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2.通过XRD,SEM和电化学测试对不同反应温度下LiNi0.4Co0.2Mn0.4O2正极材料的结构、形貌及电化学性能进行了测试和表征.测试表明随着反应温度的提高,c/a和I(003)/I(104)值也在增加,表明温度的升高可以减少锂镍离子的混排,使层状结构更加完整,进而电化学性能也更优异.900℃下反应所得到的样品,以0.2C放电,其首次放电容量为148.3mAh/g,库伦效率最高可达9.8%.循环40个周期后容量保持率为93.9%,具有较好的电化学性能.     

Nd2-xCexFe17(x=0.5,0.8,1.0)合金磁热效应的研究

用真空高频磁悬浮炉制备了Nd2-xCexFe17(x=0.5,0.8,1.0)合金,并用直接测量法测量了样品在1.3 T磁场下的磁热效应.研究表明,合金的居里温度和绝热温度ΔT ad最大值均随Ce原子分数x的增加而逐渐降低.     

La(Fe0.94Co0.06)11.8Si1.2循环磁化过程中微观结构的演变

电弧熔炼制备的铸态La(Fe0.94Co0.06)11.8Si1.2合金在1 373 K(120 h)热处理之后冰水快淬得到了NaZn13相金属间化合物.将材料应用于自制磁热循环装置中,在其居里点Tc附近进行磁化-去磁化循环处理.经过绝热循环磁化5千次后,通过扫描隧道显微镜观察到化合物La(Fe0.94Co0.06)11.8Si1.2的磁畴细化;通过HRTEM观察到化合物晶粒内部出现了应变区,在[001]方向聚集了大量的位错线.循环磁化8千次后,晶粒内部出现了亚晶界、微观裂缝结构等不可逆结构演变.磁畴结构与微观结构的演变是相互联系、相互影响的,经过不断的循环磁化去磁化处理,材料将会出现磁热性能和结构的同时衰变.     

铸态及快淬态La2Mg(Ni0.85Co0.15)9Crx(x=0～0.4)贮氢合金的电化学性能

为了提高La-Mg-Ni系(PuNi3型)贮氢合金的电化学循环稳定性,在La2Mg(Ni0.85Co0.15)9合金中加入微量Cr,用铸造及快淬工艺制备了La2Mg(Ni0.85Co0.15)9Crx(x=0,0.1,0.2,0.3,0.4)贮氢合金.研究了Cr含量对铸态及快淬态合金微观结构及电化学性能的影响.XRD,SEM及TEM的分析结果表明,铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3型结构)、LaNi5相和一定量的LaNi2相.随Cr含量的增加,铸态合金中LaNi2相的量增加.电化学测试结果表明,Cr的加入提高了铸态及快淬态合金的循环稳定性,但使合金的容量下降.当Cr添加量从0增加到0.4时,铸态合金的容量从396.3 mAh/g下降到355.6 mAh/g,循环寿命从72次增加到97次;快淬态(30 m/s)合金的容量从364.2 mAh/g下降到334.2 mAh/g,循环寿命从100次增加到131次.Cr添加使铸态合金的放电电压特性和活化性能得到改善.     

Microstructure characteristics and effect of grain orientation on magnetic properties of Fe_(63)Co_(32)Gd_5 alloy ribbons

By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.     

Thermoelectric properties of quaternary Mg_2Sn_(0.4)Si_(0.6-x)Ge_x alloys

Quaternary alloys Mg2Sn0.4Si0.6-xGex(x=0,0.02,0.05,0.08 0.1,and 0.2) were prepared using induction melting followed by hot-pressing.Relative densities of the sintered samples were over 97% of the theoretical values.Multiple phases were detected in the samples.It was found that the Seebeck coefficient was sensitive to the content of Mg2Ge and a maximum value of about 350 μV·K-1 was obtained.The introduction of Ge increases the electrical conductivity and the thermal conductivity simultaneously.The mechanism ...     

Single-negative properties of Ba_2Co_（1.8）Cu_（0.2）Fe_（12）O_（22） and Ba_3Co_2Fe_（23.4）Zn_（0.6）O_（41） hexagonal ferrites

The electromagnetic properties of Ba2Co1.8Cu0.2Fe12O22 (Co2Y) and Ba3Co2Fe23.4Zn0.6O41 (Co2Z) were studied by measuring microwave scattering parameters.In the transmission spectra of Ba2Co1.8Cu0.2Fe12O22,a forbidden band emerges due to ferromagnetic resonance,and the permeability will turn to negative in the vicinity of the ferromagnetic resonance frequency.In the complex permittivity spectra of Ba3Co2Fe23.4Zn0.6O41,the negative permittivity can be obtained due to dielectric resonance.Therefore,Co2Y and Co2...     

Effect of annealing time on the exchange coupling interactions and microstruc-ture of nanocomposite Pr_(7.5)Dy_1Fe_(71)Co_(15)Nb_1B_(4.5) ribbons

The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Interaction domains derived from strong exchange coupling interactions be- tween hard and soft magnetic grains were imaged using magnetic force microscopy (MFM). Maximum remanence, intrinsic coerciv- ity, and maximum energy product values were obtained in the ribbons annealed at 700°C for 15 min, which were composed of Pr2(Fe, Co)14B, α-(Fe, Co), and slight Pr2(Fe, Co)17 phases. Although Jr, Hci, and (BH)max decreased gradually with further increase of an- nealing time, it is emphasized that comparatively high Jr and Hci and (BH)max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.     

Inducing effect of Pb(Zr_(0.4)Ti_(0.6))O_3 thin film derived by different processes in BiFeO_3/Pb(Zr_(0.4)Ti_(0.6))O_3 multilayer capacitor at room temperature

BiFeO3/PZT multilayer capacitor was prepared on Pt(100)/Ti/SiO2/Si(100) substrate. PZT buffer layer was derived by MOCVD method (label: PZT1) and sputtering method (label: PZT2) respectively. XRD analysis indicated that high (110) orientation of BFO in the BFO/PZT1 structure was achieved. SEM analysis indicated a better microstructure in the BFO/PZT1 structure compared with BFO/PZT2. The remnant polarization of the BFO/PZT1 was 82.5 μC/cm2 at an applied voltage of 8 V, compared with that of 25.2 μC/cm2 in the BFO/PZT2 structure. The BFO/PZT1 multilayer exhibited little polarization fatigue (<1.5%) upon 1×1010 switching cycles, at an applied voltage of 4 V. The leakage current density was about 2×10?7 A/cm2 at an applied voltage 4 V, in the BFO/PZT1 capacitor. All the results indicated that PZT can act as an inducing layer to the BFO and the MOCVD derived PZT has more inducing effect to the BFO thin film at room temperature.     

Effect of Sintering Temperature on Low Frequency Response Properties of Ba_(0.6)Sr_(0.4)TiO_3 Ceramic

Ba_(0.6)Sr_(0.4)TiO_3 ceramic was synthesized by the sol-gel method combined with the solidstate reaction. Phase composition and microstructure analyses indicate that pure BST phase with aggregated nanograins can be achieved. The dielectric properties change with sintering temperature, and reach the maximum at suitable temperatures. The highest dielectric constant of 4351 is obtained at 100 Hz for 1 275 ℃ sintered sample that is 2 times greater than that of the original sample, which indicates the dielectric properties can be modulated by grain size and density. The results show that Ba_(0.6)Sr_(0.4)TiO_3 is a promising candidate for microwave applications.     

Enhanced Thermoelectric Performance of Non-equilibrium Synthesized Fe_(0.4)Co_(3.6)Sb_(12-x)Ge_x Skutterudites via Randomly Distributed Multi-scaled Impurity Dots

The p-type Ge doped Fe_(0.4)Co_(3.6)Sb_(12-x)Ge_x skutterudites with multi-scaled impurity dots(500 nm-2 mm) were successfully prepared by using melt-quenching(MQ) and subsequent spark plasma sintering(SPS) technique. Compared with traditional method, the new technology significantly shortened the processing time from several days to less than 24 hours. The phase of impurity dots was demonstrated to be CoSb through analysis of X-ray diffraction(XRD) and energy-dispersive spectrum(EDS). Impurity dots were induced by Ge substitution of Sb in the non-equilibrium synthesized process. Due to the abandonment of the long reaction of annealing crystallization, a few of Ge atoms would fail to substitute Sb site of skutterudite in this non-equilibrium synthesized process, leading to that the multi-scaled impurity dots randomly distributed in the matrix of skutterudite Fe_(0.4)Co_(3.6)Sb_(12-x)Ge_x. The combination of multi-scaled impurity dots scattering long wavelength heat-carrying phonons and the point defect scattering short and middle wavelength heat-carrying phonons dramatically made the 22.2% reduction of lattice thermal conductivity. As a result, compared with unsubstituted sample of Fe_(0.4)Co_(3.6)Sb_(12), the maximum ZT value was increased by 30.5%. Thus, the two marked features of this new synthesis process, the shortened preparation time and the enhanced thermoelectric performance, would make a promising commercial application in the future.     

Dielectric tunable properties of BaTi_4O_9-doped Ba_(0.6)Sr_(0.4)TiO_3 microwave composite ceramics

BaTi4O9-doped Ba0.6Sr0.4TiO3 (BST) composite ceramics were prepared by the conventional solid-state reaction and their structure, dielectric nonlinear characteristics and microwave dielectric properties were investigated. The secondary phase of the orthorhombic structure Ba4Ti13O30 is formed among BST composite ceramics with the increase of BaTi4O9. At the same time, a duplex or bimodal grains size distribution shows fine grains in a coarse grain matrix. The degree of frequency dispersion of dielectric permittivity below Tm is increased initially and then decreased with respect to BaTi4O9. As the BaTi4O9 content increases, the tunability of composite ceramics decreases, while the Q value increases. Inter-estingly, 70 wt% BaTi4O9-doped BST has a tunability ~4.0% (under 30 kV/cm biasing) versus a permit- tivity ~68 and quality factor ~134.1 (at ~3.2 GHz).     

AgGa0.6In0.4Se2晶体的制备与表征

以高纯单质为原料,按AgGa1-xInxSe2(x=0.4)化学计量配比配料(富1%Se),在双层石英安瓿中,用机械和温度振荡相结合的方法,合成出高纯单相多晶料.差热分析表明,其熔点和凝固点分别为804.3℃和775.6℃.采用带有籽晶袋、内壁镀碳的双层石英安瓿,用改进的垂直布里奇曼法生长出尺寸为Ф20 mm×60mm、结构完整.的AgGa0.6In0.4S2单晶体.经X射线衍射仪和红外分光光度计等分析表明,晶体为黄铜矿结构,晶格常数为a=0.602 32 nm,c=1.118 33 nm,其显露面和易解理面为(112)面;厚度约为2 mm的晶片在波长0.836-19.65μm 范围内透过率接近或超过60%,禁带宽度约为1.48 eV.结果表明,改进方法生长的AgGa1-xInxSe2晶体的结构完整,光学质量高,可用于中远红外非线性光学器件制备.     

Dy_（0．65）Tb_（0．25）Pr_（0．1）Fe_x合金的显微组织和磁致

采用金相、Ｘ射线衍射、电子探讨显微分析、交流初始磁化率和标准应变测试技术研究了Ｄｙ０．６５Ｔｂ０．２５Ｐｒ０．１Ｆｅｘ合金的显微组织、居里温度和磁致伸缩．结果表明：合金的基体为ＭｇＣｕ２型立方结构的（Ｄｙ，Ｔｂ，Ｐｒ）Ｆｅ２相，当Ｘ≤１．８０时，第二相为富稀土相，当Ｘ≥１．８５时，为（Ｄｙ，Ｔｂ，Ｐｒ）Ｆｅ３ｅ相，合金的居里温度在１．８０≤Ｘ≤１．８５区间略有增加，当Ｘ＞１．８５时，变化很小．合金的磁致伸缩约在ｘ＝１．８０时呈现出一个峰值．