Co掺杂ZnO薄膜的制备及其红外反射性能研究

目的 提高真空保温管道中红外反射层的红外反射性能。方法 以四水合醋酸钴和二水合乙酸锌为金属离子源,利用溶胶-凝胶法制备了不同Co掺杂量的ZnO溶胶(Zn1–xCoxO,x=0, 0.02, 0.04, 0.06, 0.08, 0.10)。进一步采用提拉法在镜面316L不锈钢表面制备薄膜,经450 ℃退火处理3 h后得到所需样品。利用热重-差示扫描量热法(TG-DSC)表征Zn1–xCoxO凝胶在热处理时发生的干燥、晶化过程。利用X射线衍射仪(XRD)分析表征不同Co掺杂量的薄膜中的物相组成。利用场发射扫描电子显微镜(FE-SEM)观察薄膜表面的微观形貌。利用能谱仪分析(EDS)热处理后薄膜表面的元素分布情况。利用UV-Vis-NIR分光光度计测试涂层的红外反射性能。结果 所得的Zn1–xCoxO溶胶在基体表面铺展良好,经热处理后晶粒分布均匀,表面致密无明显缺陷;涂敷Zn1–xCoxO薄膜后,样品红外反射性能得到明显改善,由纯基体的0.6355提升至最佳值0.8131(其中,x=0.06)。同时,XRD结果表明掺杂并未导致样品物相的改变,薄膜材料仍然保持稳定的六角纤锌矿结构,但随着Co掺杂量的提高,样品在(101)晶面发生择优取向。经28 d 400 ℃有氧热处理后,试样仍能保持0.8018的较高反射率。结论 通过在红外反射层表面涂敷Zn1–xCoxO薄膜,不但可有效提高其红外反射率,还可对内部金属基体起到良好的保护作用,从而提高热力管道的隔热性能和使用寿命。     

Co-Sn单相合金深过冷凝固时Co3Sn2 相生长形貌的演变机制

开展了(Co₆₀Sn₄₀)_100-xNb_x (x=0,0.4,0.6,0.8,at%)单相合金的深过冷凝固实验,研究了Co₃Sn₂相生长形貌的演变机制。结果表明,在小过冷度下,Co₃Sn₂相在x=0,0.4以海藻状的模式进行生长,随着添加的Nb含量增加至0.6at%,其生长形貌转变为树枝晶,并在x=0.8进一步转变为分形海藻晶,这主要是由于界面能各向异性和动力学各向异性的变化。随着过冷度的增加,(Co₆₀Sn₄₀)_99.4Nb_0.6合金中Co₃Sn₂相生长形貌在过冷度大于28 K时从树枝晶转变为分形海藻,当过冷度高于143 K时转变为密集海藻。少量的Nb添加在小过冷度和中间过冷度时能提高Co₃Sn₂相的生长速度,但是在大过冷度下会显著降低生长速度。Co₃Sn₂相生长速度随过冷度变化规律的转变对应其生长形貌从分形海藻向密集海藻的转变。     

Sn_(0.35-0.5x)Co_(0.35-0.5x)Zn_xC_(0.30)复合材料的制备及电化学性能

采用固相烧结和球磨相结合的方法制备了锂离子电池负极复合材料Sn_0.35-0.5xCo_0.35-0.5xZn_xC_0.30 (摩尔分数x分别为0, 0.05, 0.10, 0.15和0.20), 考察了Zn添加量对材料结构和电化学性能的影响. 烧结粉末样品的XRD分析表明, 随着Zn含量的增多, 在CoSn主相基础上, 先形成少量CoSn₂相, 随后形成少量Co₃Sn₂, Zn和Sn相. 大部分 Zn原子固溶于CoSn相. 电性能分析表明, 随着Zn含量的增加, 首次放电容量和充放电效率都呈现先增加而后趋于稳定的趋势, 当x=0.15时, 首次放电容量和充放电效率都接近最大值, 分别为343 mA-h/g和73.8%; 经过 25 cyc充放电后放电容量保持了首次放电容量的87.6%. 这表明Zn原子固溶引起的晶格畸变和多种相生成导致相界数量的增多, 加快了Li⁺动力学扩散速度, 从而显著改善了电化学性能. 选择烧结粉末样品Sn_0.275Co_0.275Zn_0.15C_0.30进行球磨, 晶粒和颗粒的细化使样品的放电容量显著提升, 但对首次放电效率和循环性能改善不明显.     

Mn1-xZnxFe2O4 (0≤x≤1)纳米粉体的模板辅助溶胶凝胶法制备及其磁性能研究

通过模板辅助溶胶-凝胶法制备了一系列的Mn_1-xZn_xFe₂O₄(0≤x≤1,步长为0.2)纳米粉体。利用XRD和VSM对材料的物相和磁性能进行了表征,主要研究了Mn_1-xZn_xFe₂O₄分子式中Zn含量的变化对样品的微观结构和磁性能的影响。实验结果表明,具有不同Zn含量的Mn_1-xZn_xFe₂O₄样品均为尖晶石结构;随着Zn含量的增加,样品的晶面间距d、平均晶粒尺寸D、饱和磁化强度M_s和居里温度T_c都呈现出下降的趋势,而样品的矫顽力H_c则呈现出先升高后降低的趋势。分析认为,M_s的下降可以用Yafet-Kittel倾角理论解释,T_c的降低归因于晶格中反铁磁性耦合的降低,而H_c的变化则主要是由于材料的磁晶各向异性常数K₁的变化引起的。     

Ni48Co1Mn37In14- x Al x 磁性记忆合金马氏体相变、力学性能和耐腐蚀性能

采用电弧熔炼的材料制备方法，研究了微量的主族元素Al掺杂对Ni₄₈Co₁Mn₃₇In_14-xAl_x (0≤x≤2)磁性形状记忆合金显微组织、晶体结构、马氏体相变、力学性能和耐腐蚀性能的影响。结果表明：用Al替代部分In，合金的晶粒尺寸明显减小，掺杂2at%的Al元素，平均晶粒尺寸缩小到10 μm左右，大约为未掺杂样品的三十五分之一；当Al掺杂量在0.25at%~2at%时，金属Al完全固溶到基体中，而且Al在合金中的固溶度随掺杂量的增加有所提升，当Al掺杂量为2at%时，Al在基体中的固溶度接近2at%；随着Al对In的取代，室温下合金由L2₁立方奥氏体与单斜6M马氏体的两相结构转变为单一的6M调制马氏体相结构，晶胞体积逐渐减小，马氏体相变温度呈现上升趋势；合金抗压强度不断增大，Ni₄₈Co₁Mn₃₇In₁₂Al₂的抗压缩断裂强度与Ni₄₈Co₁Mn₃₇In₁₄相比提高了160%，压缩应变也由5.46%增加到6.36%；适量的Al替代In后，合金在人工海水中的耐腐蚀性能总体呈现不断增强的趋势，Ni₄₈Co₁Mn₃₇In₁₂Al₂合金的耐腐蚀性能明显高于Ni₄₈Co₁Mn₃₇In₁₄合金，且其耐腐蚀性接近于304不锈钢。     

Cr掺杂SnS_2纳米花的微观结构与光学性能

以曲拉通为修饰剂,通过水热法合成花状Sn_(1-x)Cr_xS_2纳米晶(x=0、0.01、0.03、0.05和0.07),研究Cr掺杂浓度对样品的晶体结构、形貌和光学性能的影响。XRD、EDS和XPS结果表明,所有样品具有结晶良好的六方纤锌矿结构,Cr~(3+)以替代Sn~(4+)的形式掺杂进入到SnS_2晶格中。随着Cr掺杂量的增加,晶格常数发生膨胀。紫外可见吸收光谱(UV-vis)发现掺杂样品的光学带隙发生蓝移现象。傅里叶红外光谱(FT-IR)的吸收峰位并没有随着掺杂浓度的增加而发生变化。掺杂SnS_2样品的光致发光(PL)谱图出现紫光、蓝光、黄光和红光4个发光峰。随着掺杂浓度增加,发光强度呈现明显的减小趋势,以纳米花Sn_(0.95)Cr_(0.05)S_2样品的最低。色度图CIE表明,Sn_(1-x)Cr_xS_2样品显示黄色荧光发光。     

MAGNETIC PROPERTIES OF Co1-xNixFe2O4/SiO2 NANOCOMPOSITES

采用溶胶--凝胶法制备了Co_1-xNi_xFe₂O₄/SiO₂(0 ≤x ≤1.0)纳米复合材料. 利用XRD, TEM, 振动样品磁强计(VSM)和Mossbauer谱测试了900℃热处理样
品的结构、晶粒尺寸和磁性. 结果表明, 样品中Co_1-xNi_xFe₂O₄铁氧体的平均晶粒尺寸在15---20 nm之间, Ni²⁺的掺杂引起CoFe₂O₄晶胞体积减小. VSM结果表明, 随Ni²⁺含量的增加, 样品的比饱和磁化强度和矫顽力变小. Mossbauer谱表明, 室温下各样品均处于磁有序状态, 样品的内磁场随Ni²⁺含量的增加而变小.     

有机纳米颗粒复合Co掺杂ZnO热电性能研究

有机-无机纳米结两端有机材料的离散轨道能级与无机半导体的连续能带差异减小时,使得纳米结界面具有选择性散射不同能量载流子的特征,有利于提高赛贝克系数和热电性能。本文利用溶胶-凝胶法合成了具有有机-无机纳米结结构的聚对苯撑(PPP)纳米复合Zn_1-xCo_xO材料。研究结果表明,较高电导率和赛贝克系数使Zn_0.925Co_0.075O/9 wt% PPP呈现较大的功率因子。另外,有机-无机纳米界面上的界面散射大大降低了热导率。因而,合成的纳米复合材料最大ZT值达到0.22,是Zn_0.925Co_0.075O基体材料的5倍。这一实验结果表明纳米结效应是提高块体热电材料热电性能的有效途径。     

简单一步法合成Co9S8氧还原反应电催化剂

采用低温回流技术,以Co₄(CO)₁₂和S粉为原料,在1, 6-己二醇溶剂中一步合成了钴硫化物催化剂。用X射线衍射仪和扫描电子显微镜对合成的化合物进行了表征。XRD分析表明合成样品为立方结构的Co₉S₈化合物,其SEM图片显示了花椰菜状的表面形貌。Co₉S₈化合物表现出良好的氧还原催化活性,开路电位为0.75 V(vs. NHE)。在电荷转移控制电位区,电极反应传递系数和塔菲尔斜率分别为0.50和119 mV。同时,将催化剂的催化活性和电化学稳定性与商业铂催化剂进行了比较。     

PREPARATION AND MAGNETIC ANISOTROPY OF NANOCRYSTALLINE Fe0.13(CoxNi1-x)0.87FINE FIBERS

以柠檬酸和金属盐为原料, 采用有机凝胶--热还原法制备了纳米晶Fe_0.13(Co_xNi_1-x)_0.87(x=0.20, 0.30, 0.50, 0.80) 微细纤维. 采用FTIR, XRD和SEM等对纤维前驱体和热还原产物的结构、物相和形貌进行了分析; 采用振动样品磁强计 (VSM) 对纤维的磁性进行了 测试. 结果表明: 纤维直径分布在0.3---2 μm之间, 表面光滑, 长径比大, 组成纤维的晶粒尺寸约为34 nm. Fe_0.13(Co_xNi_1-x)_0.87微细纤维表现出明显的磁各向异性, 该性能主要受磁晶各向异性、形状各向异性和静磁相互作用等因素影响.纤维的易磁化方向为其轴向方向, 难磁化方向为径向方向, 所制备的Fe_0.13(Co_0.50Ni_0.50)_0.87纤维的剩磁比M_r/M_s(剩余与饱和磁化强度比)最大, 达到0.48.     

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。     

Ag/LaNixCo1-xO3触点材料的制备及电接触性能研究

本文运用溶胶-凝胶燃烧法合成了双钙钛矿型LaNixCo1-xO3(LNCO)纳米材料,利用粉末冶金和热挤压技术制备了相应的Ag/LNCO触点材料及元件样品。重点考察了不同Ni、Co含量对Ag/LNCO触点材料微观结构、物相组成、物理性能、力学性能及电寿命服役能力的影响,对其电弧侵蚀失效行为进行了研究,并与SnO2粉体增强Ag基触点材料进行对比。结果表明:溶胶凝胶法合成的LNCO纳米颗粒粒径为20-30 nm,经粉末冶金工艺制备的Ag/LaNi0.5Co0.5O3触点材料电学性能和电寿命都优于Ag/SnO2触点材料,其电阻率低至2.10 μΩ?cm,电寿命性能达到51287次。表明Ag/LaNi0.5Co0.5O3触点材料性能较佳,是一种可以取代Ag/CdO的新型触点材料。     

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.     

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.     

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.     

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.