[FePt/C]n多层膜的结构和磁学性能

采用磁控溅射方法制备FePt（50nm）和[FePt（2nm，3nm，5nm）／C（1nm）]。膜，并在550℃退火30min，研究了周期数（n）对FePt／C系列多层膜结构及磁学性能的影响。结果表明：退火后多层膜的矫顽力在总膜层厚度约为30nm时出现最大值；随着n的增大，多层膜的饱和磁化强度和晶粒尺寸均不断增大；C的加入可以有效降低晶粒间交换耦合作用。刚此可以通过控制周期数得到县仃合适的微观结构和高的磁学性能的FePt／C多层膜，从而满足超高密度磁记录介质的要求。     

Pt缓冲层厚度对FePt薄膜合金相转变和磁性能的影响

利用磁控溅射法制备了具有Pt缓冲层的[FePt]50多层膜.通过x射线衍射(XRD)分析和磁性测量研究了不同缓冲层厚度对样品微结构演变和磁性能的影响.结果表明,随着Pt缓冲层厚度(t≤8.6 nm)的增加,薄膜合金的有序化温度明显降低,晶粒尺寸逐渐减小FePt薄膜样品点阵常数c/a的比值逐渐减小,有序度参数S逐渐增大;同时样品的矫顽力也随着缓冲层厚度的增加而增大,在425℃退火的样品,其矫顽力由缓冲层厚度t=0时的398 kA/m增加到t=8.6nm时的523 kA/m(接近无缓冲层样品在500℃退火的值),平均变化率为14.53 kA·m-1/nm,有效地降低了样品的退火温度;与此同时,剩磁比逐渐减小,从0.68减少到0.56.     

Cu含量对FePt薄膜退火温度的影响

采用共溅射方法存玻璃基片上制备了（FePt）1-xCux合金薄膜，FePt合金中添加Cu可以有效降低退火温度，（FePt）1-xCux（x=19．5％）在350℃退火后可以使面内矫顽力Hc〃，达到200kA／m，垂直矫顽力Hc⊥达到280kA／m左右，而纯FePt仅有几千A／m。X射线衍射结果表明退火后形成的FePtCu三元合金是降低退火温度的主要原因。剩磁曲线分析表明Cu的加入不能明显降低晶粒间交换耦合作用。（FePt）1-xCux在400℃退火可以得到10^-24m^3的磁激活体积。     

Co／Ti非晶多层膜晶化过程中结构及磁性的变化

利用双对向靶溅射方法在室温下制备Ｃｏ／Ｔｉ非晶多层膜，并采用原位退火透射电镜和原位热重法，观测了Ｃｏ／Ｔｉ多层膜结构与磁性随温度的变化，结果表明：退火温度ｔａ为４００℃时，薄膜开始晶化，Ｃｏ，Ｔｉ颗粒析出并粗化；ｔａ＞６００℃时，具有铁磁性的Ｃｏ单质完全消失，全部转化为Ｃｏ２Ｔｉ相．热磁测量在３９０及５２０℃附近出现了两个明显的磁性转变峰，与薄膜结构变化对应．适当温度（４００—５２０℃）的退火可获得高饱和磁化强度的Ｃｏ－Ｔｉ颗粒膜．     

CoPt和CoPt／Ag合金薄膜的结构和磁性能

用磁控溅射法在玻璃基片上制备了具有等原子比组成的不同厚度的CoPt薄膜及不同Ag底层厚度的CoPt／Ag薄膜。真空退火后的结果表明，膜厚对CoPt薄膜的微观结构和磁性能有着重要的影响，膜厚较薄时（δ≤15nm）有利于易磁化轴（c轴）垂直于膜面取向，从而具有高的垂直磁各向异性；Ag底层可以诱导L10-CoPt相的形成并使c轴垂直择优取向，且Ag底层越厚其诱导效应越强。     

磁场取向对Sm-Co／a-Fe交换耦合双层膜矫顽力的影响

微磁学理论为基础，采用三维动力学模型研究了Sm—Co／a-Fe双层膜的内禀矫顽力与外场取向的关系，以预测交换耦合双层膜（硬磁层和软磁层）磁性体系的磁性。结果表明：随外场角度（外磁场方向与硬磁层易轴间的夹角1的增大，内禀矫顽力减小；但当软磁层厚度小于其临界尺寸或软磁层厚度远大于其临界尺寸时，出现局域极小及局域极大现象：外场角度较小时，随软磁层厚度的增加，内禀矫顽力出现一峰值；这表明适当方向的外场有助于获得比较高的内禀矫顽力。采用能垒分析法对此结果进行定性解释。     

Ru籽晶层对CoCrPt-SiO_2垂直记录层形貌及结构的影响

采用磁控溅射方法,制备了以不同厚度Ru薄膜为籽晶层的CoCrPt-SiO2垂直磁记录薄膜。利用原子力显微镜(AFM)、透射电镜(TEM)分析Ru薄膜的结构和形貌,并研究了其结构对CoCrPt-SiO2薄膜表面形貌、粗糙度及结构的影响。结果表明,CoCrPt-SiO2记录层的晶粒尺寸和粗糙度均随着Ru籽晶层厚度的增加而增加,薄而粗糙的籽晶层适合于高密度磁记录介质。对于CoCrPt-SiO2记录层晶粒的优化,厚度为70nm的Ru籽晶层有利于记录层薄膜晶粒的完全隔离,从而提高了磁记录性能。     

Cr和CrTi底层对CoCrPt薄膜介质的磁和结构性能的影响

为了改善记录介质的磁性能,研究了溅射Cr和CrTi底层对Co68Cr17Pt15性能的影响。发现在玻璃盘基和CoCrPt磁性层之间引入100nm厚的Cr底层,可使介质矫顽力从56kA·m-1增加到127kA·m-1,同时剩磁比和矫顽力矩形比分别增加66%和74%。同时还发现Cr底层厚度对介质磁性能有较大影响。考虑到减小Cr底层和磁性层的晶格匹配,在Cr底层里添加Ti元素,当Ti原子分数达到1.5%时,即使在室温下溅射,薄膜也有好的面内磁滞回线,此时矫顽力可达到160kA·m-1。X射线衍射表明在介质中引入Cr和CrTi底层,由于薄膜能更好的沿着垂直于易磁化轴方向生长而使介质性能提高。     

NiFeSiMnMo/Cu/NiFeSiMnMo多层膜结构中磁性层厚度对巨磁阻抗效应的影响

在康宁玻璃上用真空蒸镀法沉积NiFeSiMnMo/Cu/NiFeSiMnMo多层膜,对所沉积单层膜的软磁性能随膜厚的变化和多层膜的巨磁阻抗效应随磁性层(NiFeSiMnMo)厚度的变化进行分析.实验结果表明:NiFeSiMnMo单层膜随厚度的增加,矫顽力增大,软磁性能变差;退火后的多层膜的纵向巨磁阻抗比(GMI ratio)的最大值随磁性层NiFeSiMnMo的厚度增加而增加.     

最高面记录密度的涂覆型磁带

日本富士胶片公司和美国IBM公司采用在记录介质上涂覆Ba铁氧体方法制造磁带,使其信息记录和再生密度达到85．9Gb／m^2,创全球之最。具体方法：将Ba铁氧体均匀地细化到1600nm,以提高矫顽力,防止热稳定性劣化,再使磁性粒子均匀分散到粘结剂中,使涂覆在磁带上的磁记录层薄细化（纳米级）,最后与IBM公司记录磁头技术结合起来,就可以大大提高磁记录密度。     

Structural, mechanical and corrosion properties of TiOxNy/ZrOxNy multilayer coatings

Results on the deposition and characterization of TiO_xN_y/ZrO_xN_y multilayers, with bilayer periods of 20 and 400 nm, are presented. The coatings were deposited on TiNiNb alloy substrates by the pulsed magnetron sputtering method. The elemental composition, hardness, adhesion and corrosion resistance of the coatings were analyzed.As resulted from the XPS analysis, the individual layers consisted of a mixture of titanium or zirconium oxynitrides and corresponding oxides. X-ray analysis revealed that the coatings were amorphous. Only slight differences between the microhardness and adhesion values of the coatings with small and large bilayer period Λ were found. The experiments also showed that the multilayered coatings improved the corrosion resistance of the uncoated alloy and reduced the amount of ion release in artificial body fluids.     

MOCVD growth and characterizations of BxAl1−xAs and BxAl1−x−yInyAs alloys

Zinc-blende B_xAl_1−xAs and B_xAl_1−x−yIn_yAs alloys have been grown on exactly oriented (0 0 1)GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). The influence of susceptor coating, growth temperature and gas-phase boron mole fraction on boron incorporation into AlAs has been comprehensively investigated. It has been found that boron incorporation into AlAs could be enhanced and the optimal growth temperature range of B_xAl_1−xAs alloys changed from 580 °C to 610 °C when SiC-coated graphite susceptors were replaced by the non-coated ones. In this study, the maximum boron composition x of 2.8% was achieved for the pseudomorphically strained B_xAl_1−xAs alloys. AFM measurements show that RMS roughness of B_xAl_1−xAs alloys increased sharply with the increase of gas-phase boron mole fraction. Raman spectra of B_xAl_1−xAs alloys show a linear increase of the BAs shift with boron composition x. Based on BAlAs deposition, bulk B_xAl_1−x−yIn_yAs (x = 1.9%) quaternary alloy was grown lattice-matched to GaAs successfully. Moreover, 10-period BAlAs/GaAs and BAlInAs/GaAs MQW heterostructures were also demonstrated.     

生物医用NiTi形状记忆合金腐蚀研究进展

镍钛形状记忆合金(NiTi-SMA)具有较好的耐腐蚀和机械性能,在口腔和临床医学中有着大量而广泛的应用。NiTi-SMA腐蚀后释放Ni²⁺会引发细胞毒性和过敏反应,进一步提高NiTi-SMA的耐蚀性是目前生物医学材料领域发展的核心之一。本文对近年来国内外有关口腔医学和临床医学中常用NiTi-SMA的腐蚀研究现状进行了总结,同时也对NiTi-SMA增材制造及表面改性技术进行了评述,以期为开发高性能抗腐蚀生物医用NiTi-SMA提供一定的指导意义。     

Li掺杂Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3高熵陶瓷的制备及介电性能研究

近年来,在高熵合金基础上发展起来的高熵陶瓷逐渐引起了研究者的广泛关注,其出现为开发高性能的无机非金属材料提供了新的设计思路。本文采用固相法制备了BaMO3基钙钛矿型高熵陶瓷Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%),并研究了Li含量对高熵陶瓷物相结构、微观形貌及介电性能的影响。结果表明,Li含量对陶瓷结构的影响不大,陶瓷均保持立方钙钛矿结构,且无杂相产生;陶瓷的晶粒尺寸相对较均匀。当x = 0时,即B位七元等摩尔比Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3高熵陶瓷,其介电常数达到了最大值2920 (@100 Hz),相较于已报道的不掺Li的六元高熵钙钛矿陶瓷Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3提升了近50倍。     

Hydrothermal synthesis of superconductors Ba1−xKxBiO3 and double perovskites Ba1−xKxBi1−yNayO3

Superconductors Ba_1−xK_xBiO₃ and body-centered double perovskites Ba_1−xK_xBi_1−yNa_yO₃ have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures T_C of Ba_1−xK_xBiO₃ decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level.     

Magnetic phase diagrams of the TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 systems

The a.c. susceptibility and high field magnetization on TbRh_2−xPd_xPd_xSi₂ and TbRu_2−xPd_xSi₂ compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves.     

High strength and good ductility of casting Al-Cu alloy modified by PrxOy and LaxOy

A modified Al-Cu alloy with high tensile strength and ductility of about 574.0 MPa and 10.4%, respectively, was obtained by adding multiple rare earth oxides (Pr_xO_y and La_xO_y) as modifier. Compared with the unmodified Al-Cu alloy, the tensile strength and ductility of the modified sample were increased by 24.3% and 42.5%, respectively. The improvement both in the strength and ductility may attribute to the finer crystal grains and dendrites, more homogeneously distributed θ′ phase precipitates and the intermetallic compounds formed at the crystal grain boundaries as well as in the space of the dendrites.     

Si3N4/Ti/Cu/Ni/Cu/Ti/Si3N4二次部分瞬间液相连接强度

采用Ti/Cu／Ni中间层对Si3N4陶瓷进行二次部分瞬间液相(PTLP)连接，研究连接工艺参数对Si3N4／Ti/Cu／Ni连接强度的影响，同时研究了连接强度随试验温度的变化规律。结果表明，在该试验条件下，室温连接强度随着二次连接温度的提高和二次保温时间的延长而提高，改变连接工艺参数对Si3N4／Ti/Cu／Ni二次PTLP连接界面反应层厚度无明显影响；连接强度在试验温度400℃时达到最大，随后随试验温度升高，连接强度降低，但在800℃前，其高温强度具有很好的稳定性。     

Thermoelectric properties of Sn1−x−yTiySbxO2 ceramics

Thermoelectric properties of Sn_1−x−yTi_y Sb_xO₂ ceramics were investigated in detail. The addition of Sb into SnO₂ matrix increased the electric conductivity, σ. The increase in the σ value should be caused by the increase in the carrier concentration. The Seebeck coefficients of all the samples were negative, which means that these samples have n-type conduction. The samples of this study have porous structure. The maximum Z value of all the samples measured in this study was 2.4 × 10⁻⁵ K⁻¹.     

Power factor of La1−xSrxFeO3 and LaFe1−yNiyO3

The electrical conductivity (σ), Seebeck coefficient (S), and power factor (σS²) of perovskite-type LaFeO₃, La_1−xSr_xFeO₃ [0.1 ≤ x ≤ 0.4] and LaFe_1−yNi_yO₃ [0.1 ≤ y ≤ 0.6] were investigated in the temperature range of 300–1100 K to explore their possibility as thermoelectric materials. The electrical conductivity of LaFeO₃ showed semiconducting behavior, and its Seebeck coefficient changed from positive to negative around 650 K with increasing temperature. The electrical conductivity of LaFeO₃ increased with the substitutions of Sr and Ni atoms, while its Seebeck coefficient decreased. The Seebeck coefficient of La_1−xSr_xFeO₃ was positive, whereas that of LaFe_1−yNi_yO₃ changed from positive to negative with increasing Ni content. The substitutions of Sr and Ni were effective in increasing the power factor of LaFeO₃; 0.0053 × 10⁻⁴ Wm⁻¹ K⁻² for LaFeO₃ (1050 K), 1.1 × 10⁻⁴ Wm⁻¹ K⁻² for La_1−xSr_xFeO₃ (x = 0.1 at 1100 K) and 0.63 × 10⁻⁴ Wm⁻¹ K⁻² for LaFe_1−yNi_yO₃ (y = 0.1 at 1100 K).