Ni-Cr／Ti／多元陶瓷连接界面微观结构与性能

在Ni-Cr合金表面磁控溅射一层Ti薄膜作为中间层,研究了Ni-Cr/Ti/多元陶瓷连接界面微观结构与性能.结果表明:Ni-Cr/Ti/瓷界面结合致密,无裂纹、孔隙等缺陷.Ni-Cr/Ti/瓷界面反应非常复杂,界面处形成的新物相有SnCr0.14Ox,NiCr2O4,Cr2O3,TiO2,A1Ti3和Ti2Ni.Ti中间层的厚度,烤瓷温度和烤瓷时间将影响Ni-Cr/Ti/瓷界面反应产物的种类、数量及分布,最终决定了界面结合强度.烤瓷温度990℃,烤瓷时间2.5min,Ni-Cr/瓷界面结合强度达40.2MPa;在Ni-Cr合金表面溅射Ti中间层厚度为3μm时,Ni-Cr/Ti/瓷界面结合强度可达到48.4MPa.     

钛表面的氧化对钛瓷结合强度的影响

研究了钛表面氧化对钛/瓷结合强度的影响, 并采用溶胶凝胶技术在钛表面制备SnO_x中间层, 研究SnO_x层对钛/瓷结合强度的影响. 结果表明：空气炉中800℃氧化3min后, 钛/瓷结合强度明显下降; 烤瓷炉中预氧化3min, 钛/瓷结合强度无明显变化. 热处理使钛表面生成一层金红石型氧化层, 钛/瓷剥脱主要发生在金红石氧化层与钛之间. 采用溶胶-凝胶法经300℃处理后在钛表面制得的SnO_x涂层, 可有效隔绝氧向Ti表面的扩散, 防止钛表面的过度氧化, 提高了钛/瓷结合强度. 经SnO_x涂层处理后, 钛/瓷剥脱主要发生在SnO_x涂层内.     

钛/瓷连接界面残余应力有限元分析

采用有限元法分析了钛/瓷、钛/ZrO2/瓷连接冷却过程中界面残余应力形成的大小和分布特征。结果表明,钛/瓷试样在结合界面处存在较大的残余应力。在平行于界面的方向上,陶瓷表面受拉应力的作用,易导致表面裂纹的产生。钛/瓷界面的边缘处存在较大的应力集中,尤其是结合界面位于Z向棱边的顶角处,应力集中较为明显,易导致瓷崩和瓷裂。ZrO2中间层可抑制钛表面过度氧化,缓和钛/瓷界面应力集中,提高钛/瓷结合强度,降低陶瓷层裂纹倾向。     

三维钛网表面双生物陶瓷涂层的制备及其性能

采用浸渍涂敷-烧结法首次在医用三维钛网表面制备出双生物陶瓷涂层,利用X射线衍射、场发射扫描电子显微镜对HA-BG/BG/Ti复合材料进行了微观表征,拉伸法测量了Ti基体与BG涂层的结合强度,模拟人体体液(SBF)评价复合材料的生物相容性.研究表明:该双生物陶瓷涂层的内层为生物玻璃(BG)涂层,外层为多孔结构的羟基磷灰石-生物玻璃(HA-BG)复合涂层.Ti基体被致密的BG涂层包覆,由于在BG/Ti界面发生化学反应,界面的结合强度提高,平均结合强度达27 MPa.生物相容性实验表明,HA-BG/BG/Ti复合材料表面会被一层整齐、致密的HA覆盖,具有良好的生物相容性.     

钛合金表面磁控溅射制备HA/YSZ梯度涂层

采用射频磁控溅射法在Ti6Al4V基体上制备了HA/YSZ生物梯度涂层.借助于XRD,SEM,EDS等对溅射涂层的相组成、微观形貌和界面状态进行了研究.实验结果表明:磁控溅射的生物梯度涂层呈非晶态,经过退火处理,可以使其转化为晶态,恢复缺失的OH-1;梯度涂层的微观表面凹凸不平,并呈现网状结构和较多的孔隙,后处理仍保持梯度涂层利于新骨生长的表面形貌,并使其转变为针状结晶.HA/YSZ梯度涂层与基体结合紧密,在涂层与基体界面结合处约5.0μm范围内存在Ti,Ca,P,Zr的相互扩散层,梯度涂层与基体的界面结合强度达60.5MPa.     

纤维涂层法制备SiCf/Cu复合材料及其性能分析

为研究纤维涂层法制备SiCf/Cu复合材料的性能特点,通过磁控溅射法先后将Ti6Al4V界面改性层和基体Cu涂层涂覆到SiC纤维表面,并通过真空热压法将被涂覆的纤维制备成SiCf/Cu复合材料.对Ti6Al4V涂层、Cu涂层以及复合材料进行了微观分析,并测试了复合材料的拉伸强度.研究表明,复合材料的Cu基体由致密而细小的晶粒组成;Ti6Al4V提高了纤维/基体界面结合强度,复合材料轴向抗拉强度高达500 MPa,界面脱粘主要发生在纤维表面的碳涂层与纤维之间.     

氧化预处理提高钢硅烷处理效果的机理分析

对钢表面进行了氧化预处理,采用扫描电镜、能谱和红外光谱研究了钢/氧化层/硅烷层/环氧涂层体系的界面结合特征,通过与未经氧化预处理的体系进行比较,研究氧化层对硅烷聚合方式、界面构象以及成键方式的影响.结果表明:钢表面氧化后,拉伸剪切破坏主要发生在硅烷/涂层界面,而未经氧化预处理的试样,弱相界面位于钢/硅烷界面.氧化层可以抑制硅烷自身的缩聚,促进硅烷在钢表面的定向吸附,显著提高钢/涂层界面结合强度.     

Ni-Cr/Ti/瓷界面反应机制

采用磁控溅射技术,在Ni-Cr合金表面溅射一层Ti薄膜作为中间层,研究了Ni-Cr/Ti/瓷界面组织结构,产物种类、分布及反应机制。结果表明:Ni-Cr/Ti/瓷界面反应复杂,界面处形成的新物相有Ti2Ni,AlTi3,TiO2,SnCr0.14OX,NiCr2O4和Cr2O3。高温烤瓷过程中,Ti与Ni以稳定的化合物Ti2Ni形式结合,同时Ti与陶瓷中Al2O3反应生成AlTi3化合物,与SnO2和SiO2发生置换反应生成TiO2,TiO2与陶瓷中氧化物结合,更好的实现了Ni-Cr合金与陶瓷的连接。     

仿生磷灰石涂层与钛基体结合强度的划痕法实验

本文采用碱热处理及SBF浸泡的方法在钛片上制备了仿生磷灰石涂层,并采用AES进行表面成分-深度分析,划痕法测定磷灰石涂层与基体的结合强度.结果显示,经碱热处理而制得的钛表面仿生磷灰石涂层与基体结合的界面为成分梯度界面,二者的结合要通过成分含量呈梯度变化的过渡层:Ca、P元素的含量从表面到基体逐渐下降,Ti元素的含量逐渐上升.热处理有利于提高涂层的基体结合强度,其原因是热处理使SBF中形成的磷灰石的晶核细小而均匀,使得表面涂层与基体之间的结合更为紧密.预钙化处理后形成的磷灰石涂层与金属之间仍为成分梯度界面,因此对涂层的基体结合强度影响不大.     

Ti/ZrN2/Al薄膜界面扩散反应的研究

利用直流磁控反应溅射法在Al基底上制备了ZrN2及Ti多层薄层,利用扫描俄歇微探针的深度剖析和线形分析技术研究了真空热处理对Ti/ZrN2/Al样品膜层之间的界面化学状态和相互作用的影响,研究结果表明,真空热处理使Ti/ZrN2/Al薄膜界面上发生了明显的界面扩散和化学反应,生成了TiNx物种,并且薄膜内层发生了严重的氧化反应。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.     

n-PbTep+−Pb1−xSnxTe heterojunctions prepared by a modified hot wall technique

$\text{n-PbTe}\text{p}{}^{\mathrm{+}}\text{?}\text{Pb}{}_{\mathrm{1?x}}\text{Sn}{}_{\mathrm{x}}\text{Te}$ heterojunctions with a long wavelength spectral cutoff (λ_c ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with R_oA equal to 170 Ω cm² and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given.     

Core-current-enhanced domain-wall pinning in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon

We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results.     

Reactive plasma deposited SixCyHz films

Si_xC_yH_z films have been prepared at 200°C by reactive plasma deposition from SiH₄ and CH₄ diluted in helium in a tubular reactor. These films have a ratio s (equal to $\text{Si}\text{(}\text{Si+C}\text{))}$ ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH₄-CH₄-He plasma have been performed and the results are related to the composition of the deposited layers.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.