等离子喷涂ZrO2-N iCoCrAlY 梯度涂层的成分分布与力学性能

在ZrO₂-NiCoCrAlY 梯度涂层中, 由基体到涂层表面, ZrO₂ 的含量逐渐增多,NiCoCrAlY 的含量逐渐减少,形成一种无宏观结合界面的成分连续变化的组织结构。随ZrO₂ 组元含量的升高, ZrO₂-NiCoCrAlY 复合涂层的密度基本呈线性降低; 涂层硬度则先降低后升高, 含60 vo l%ZrO₂ 的复合涂层具有最低的硬度值; 富含NiCoCrAlY 组元的复合涂层的孔隙率略低。与双层涂层相比, 成分梯度化的分布使梯度涂层的内聚强度和涂层与基体的结合强度都得到了明显地提高; 涂层与基体的结合界面是梯度涂层2基体体系中的最薄弱之处。     

电弧喷涂制备0Cr18Ni9/Al梯度涂层及其组织研究

研究了电弧热喷涂熔点差别大的不锈钢、铝金属丝材制备0Cr18Ni9/Al梯度涂层的制备工艺与涂层的微观组织.结果表明,成功制备了0Cr18Ni9/Al梯度涂层,提高了涂层中的Al含量,同时形成了金属间化合物FeAl相,涂层为层状结构.涂层界面结合良好,利于优化涂层结构.梯度涂层中的物相以机械混合方式存在.     

Cr2O3 梯度涂层的组织与耐磨性研究

采用等离子喷涂技术设计并制备了耐磨梯度涂层。涂层组织,以及显微硬度和磨损率测量结果表明,从基体到陶瓷层,通过涂层成分的逐渐变化,涂层的组织及性能均具有梯度涂层的特征。     

TiC0.81N0.48和TiC0.61N0.44O0.15涂层的热稳定性能

用中温化学气相沉积工艺制备TiC0.81N0.48和TiC0.61N0.44O0.15涂层,用显微维氏硬度计测定TiCN和TiCNO涂层的硬度,用X射线衍射仪和激光拉曼光谱仪分析涂层的结构,研究了TiCN和TiCNO涂层在700℃真空退火后的组织结构转变对硬度的影响。结果表明:真空退火后TiC0.81N0.48和TiC0.61N0.44O0.15涂层的硬度先下降,然后趋于稳定。TiC0.81N0.48和TiC0.61N0.44O0.15涂层在700℃真空退火时,C原子从TiCN晶格析出后先形成sp3C;随着退火时间的延长,sp3C逐渐向sp2C转变;随后sp2C团簇增加,无序程度降低,TiCN逐渐分解为TiC和TiN相。硬度的降低,是由于涂层内缺陷密度的减少使应力释放,还与高温下TiC0.81N0.48和TiC0.61N0.44O0.15涂层组织结构的转变,特别是sp3C和sp2C的形成有关。与TiC0.61N0.44O0.15涂层相比,在700℃真空退火时TiC0.81N0.48涂层组织转变的进程加快,热稳定性能较差。     

WC、ZrO2 、Cr2O3 和Al2O3 陶瓷颗粒/ 镍合金复合涂层微观组织结构的分形

采用等离子喷涂工艺, 制备了WC、ZrO₂ 、Cr₂O₃ 和Al₂O₃ 陶瓷颗粒/ 镍合金复合涂层。用X 射线衍射研究了陶瓷颗粒复合涂层相的分布; 用里氏硬度计测量陶瓷颗粒/ 镍合金复合涂层的硬度; 用CSS-1110 电子万能试验机研究陶瓷颗粒复合涂层的弯曲断裂性能。对涂层金相组织结构进行二值化处理, 利用Sandbox 法对陶瓷颗粒在金属基体中的分布进行研究, 得到了不同体积分数下陶瓷颗粒复合材料涂层的分维数。结果表明,陶瓷颗粒/ 镍合金复合涂层分维数随陶瓷颗粒含量的增加而增加, 与陶瓷颗粒种类无关; 陶瓷颗粒/ 镍合金复合涂层硬度和分维数随陶瓷颗粒直径减小而增加。随着分维数的增加, 复合涂层弯曲断裂角下降。      

陶瓷/金属等离子涂层显微组织特征及其图像分析

用扫描电镜和能谱仪研究了ZrO2陶瓷与NiCrAl金属等离子喷涂形成梯度涂层的显微组织特征；扫描电镜联机图像分析系统软件作为涂层质量的一种检验方法，对涂层特征显微组织进行了图像处理，对成分和孔隙率进行了定量计算，通过对计算结果的方差分析，对等离子喷涂工艺参数的调整提出了参考意见和措施。     

Y-TZP/LZAS微晶玻璃功能梯度涂层残余应力分析

为了提高钢基体微晶玻璃涂层的韧性,设计了Y-TZP/LZAS微晶玻璃功能梯度涂层。运用有限元软件,分析了梯度层数目、梯度层厚度和层间3Y-TZP体积组分差等参数对涂层/基体界面残余热应力的影响。结果表明,涂层表层主要分布为径向压应力;在涂层/基体界面的边缘区域应力集中较为严重;涂层/基体界面处的径向应力、轴向应力和剪切应力以及梯度层数目、梯度层厚度和3Y-TZP体积组分差均有密切关系。最后通过涂搪法制备了梯度涂层,测试了涂层表面残余应力,并与有限元结果对比,以验证模拟的准确性。     

双涂层和梯度涂层改善SiCf/Al界面性能的微观机制

研究双涂层（RD）和梯度涂层（RG）处理改善SiCf/Al界面和复合材料性能的微观机制。发现RD试样中纤维外涂层氮化硼（BN）阻档了Al向界面内层C的扩散，从而阻止Al,C脆性相的生成，同样RG试样中C，Si梯度分布阻碍Al,C脆性相的形成，故这二种涂层处理均较单C涂层较好地改善了界面和复合材料性能。     

Al2O3梯度涂层的制备及性能研究

为了克服无梯度陶瓷涂层中应力集中、易产生裂纹的缺陷,以提高涂层的结合强度,采用等离子喷涂方法制备了NiAl-Al-2O-3梯度陶瓷涂层,并对涂层的组织分布、结合强度、显微硬度和抗热震性进行了研究.结果表明,梯度涂层的组织表现出宏观的不均匀性和微观的连续性分布特征,NiAl过渡层的引入可有效地改善涂层的质量.本梯度涂层中Al-2O-3含量为80%时,涂层的显微硬度最高(达620 HV).涂层成分的梯度化有利于涂层的结合强度和抗热震性能的提高.     

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.     

K2(Rb2,Cs2,Tl2)TeBr6(I6) and Rb3(Cs3)Sb2(Bi2)Br9(I9) perovskite compounds

We systematize available experimental data on the crystal structure of the ternary halides K₂(Rb₂,Cs₂,Tl₂)TeBr₆(I₆) and Rb₃(Cs₃)Sb₂(Bi₂)Br₉(I₉), analyze the general trends in the properties of their single crystals, and examine the key features of the physicochemical interaction in related systems.     

Flux growth of single magnetic sublattice antiferromagnetic garnets Ca3 Fe2 Ge3 O12 and Ca3 Mn2 Ge3 O12

Magnetic single crystals garnets Ca₃ X₂ Ge₃ O₁₂ with X = Mn³⁺ or Fe³⁺ containing Ca²⁺ and Ge⁴⁺ are of great interest due to the rise of an antifer-romagnetic order in one definite octahedral site. The optimal conditions for obtaining single magnetic-sublattice garnets of large size (1 cm in diameter) have been analyzed. Two groups of solvents have been tested: Bi₂ O₃ or PbO based flux. The best results were obtained with PbO flux and starting composition : % Moles 44 PbO 1b 35 GeO₂ 1b 15 CaO 1b 6 X₂ O₃.     

Syntheses and structures of Ta2(WO2)0.87H0.26(PO4)4 and Ta2(MoO2)(PO4)4

Tantalum hydrogen phosphate, β-TaH(PO₄)₂, has a three-dimensional structure that is stable to remarkably high temperature (∼600 °C) presumably due to the presence of strong hydrogen bonds. Impedance measurements indicate a low conductivity, 2.0 × 10⁻⁶ S/cm at 200 °C in 5% H₂. In further studies aimed at enhancing the conductivity by aliovalent doping, we have investigated systematically the synthesis of compounds in the TaH(PO₄)₂-W₂P₂O₁₁ system at 380 °C. As a result, a new phase, Ta₂(WO₂)_0.87H_0.26(PO₄)₄, was identified and subsequently the molybdenum analog Ta₂(MoO₂)(PO₄)₄ was also prepared. The structures were determined by single crystal X-ray diffraction techniques. The structures of Ta₂(WO₂)_0.87H_0.26(PO₄)₄ and Ta₂(MoO₂)(PO₄)₄ can be formally derived from the structure of β-TaH(PO₄)₂ by the replacement of two P-OH protons with an MO₂²⁺ (M = Mo and W) group together with a change in the orientation of some phosphate tetrahedra.     

(K0.44,Na0.52,Li0.04) (Nb0.84,Ta0.10,Sb0.06)O3 Ferroelectric Ceramics

Recent progress in (K_0.44,Na_0.52,Li_0.043-based ceramics (KNN) with special emphasis on (K_0.44,Na_0.52,Li_0.040.84,Ta_0.10,Sb_0.06))O₃ (KNN-LT-LS) is reviewed concisely. The base KNN and its compositional derivatives are analyzed in terms of dopant-property relationships, which are then extended to the ternary derivatives. The effects of processing conditions such as humidity, precursor purity, and oxygen partial pressure during sintering are elaborated on from a phenomenological perspective. It is also shown that the spontaneous polarization is sensitive to the processing route chosen for synthesis (mixed oxide versus perovskite routes). Special attention is devoted to the discussion of the morphotropic phase boundary (MPB) dilemma in the KNN-LT-LS system, where it is shown that the origin of high piezoelectric activity is actually due to a polymorphic transition at room temperature. It is shown that prototype transducers based on pure and 1 mol% Ba²⁺ doped KNN-LT-LS exhibit performance metrics comparable to those fabricated using PZT-5H. Overall, KNNLT- LS ceramics show great promise for lead-free applications, although issues such as temperature dependence of properties and strong sensitivity to processing conditions remain as the 2 major challenges.     

Preparation of (NH4)Zr2(PO4)3 and HZr2(PO4)3

(NH₄)Zr₂(PO₄)₃ has been prepared, hydrothermally, from α-zirconium phosphate in three different ways; (1) from amine intercalates at 300°C, (2) from mixtures of ZrOCl₂·8H₂O in excess (NH₄)H₂PO₄ and (3) reaction of NH₄Cl with Zr(NaPO₄)₂. Ammonium dizirconium triphosphate is rhombohedral with a = 8.676(1) and $\text{c}\text{= 24.288(5)}\text{A}\text{?}$. It decomposed on heating to HZr₂(PO₄)₃. Below 600°C a complex, as yet unindexed, X-ray pattern was obtained. A very similar X-ray pattern was obtained by washing LiTi_0.1Zr_1.9(PO₄)₃ with 0.3N HCl. Heating this phase or NH₄Zr₂(PO₄)₃, above 600°C resulted in the appearance of a rhombohedral phase of HZr₂(PO₄)₃ with cell dimensions a = 8.803(5) and $\text{c}\text{= 23.23(1)}\text{A}\text{?}$. The protons were not completely removed until about 1150°C. Decomposition of (NH₄)Zr₂(PO₄)₃ at 450°C yielded an acidic gas whereas at 700°C NH₃ was evolved. A possible explanation for this behavior is presented.     

Dielectric properties of Pb3 (PO4)2 | Pb3 (AsO4)2

The dielectric constants of Pb₃ (PO₄)₂ | Pb₃ (AsO₄)₂ at room temperature are intrinsic and fulfill the Lyddane - Teller - Sachs relation. At higher temperatures the specific conductivity increases with an activation energy of 0.56 eV leading to Maxwell - Wagner polarization effects thereby increasing the effective dielectric constant. Corresponding peaks in ∈' (T) are extrinsic and not attributed to structural phase transformations.     

Bi3(FeO4)(MoO4)2 and Bi3(GaO4)(MoO4)2 - new compounds with scheelite related structures

The title compounds have been prepared for the first time. They have monoclinic structures related to the scheelite (CaWO₄) structure, and they represent the first example of trivalent cations on tetrahedral sites of the scheelite structure. A superstructure is observed due to an ordering of the cations on the tetrahedral sites.     

Hydrothermal Crystallization in the Systems La2(CO3)3 ? 6H2O-CaCO3(BaCO3)-R-H2O (R = Na2CO3, K2CO3, NaHCO3, KHCO3, NaCl, NH4Cl, CO(NH2)2)

Crystallization in the systems La₂(CO₃)₃ ⋅ 6H₂O-CaCO₃(BaCO₃)-R-H₂O (R = Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, NaCl, NH₄Cl, CO(NH₂)₂) was studied under hydrothermal conditions (400–450°C). The solid reaction products were found to contain LaOHCO₃ and NaLa(CO₃)₂. Detailed thermal decomposition schemes were proposed for these phases, and their lattice parameters were refined. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1366–1372. Original Russian Text Copyright ? 2005 by Nikol'skaya, Dem'yanets.     

Direct observation of ferroelasticity in Pb3(PO4)2  Pb3(VO4)2

Ferroelasticity has been established in the room temperature phase of Pb₃(P_xV_1-xO₄)₂, (x ≥ 0.8). The coercitive stress and the spontaneous strain have been determined and found to be 1.6 bars and ca. 3.5 · 10^?4 respectively. The effect of domain switching on double refraction and Raman spectra is clearly brought out.     

Crystal Structure of (H3O)6[(UO2)5(SeO4)8(H2O)5](H2O)5

Crystals of (H₃O)₆[(UO₂)₅(SeO₄)₈(H₂O)₅](H₂O)₅ were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 13.835(2), b = 13.4374(16), c = 14.310(3) Å, β = 108.004(14)°, V = 2530.1(7) Å ³] was solved by the direct method and refined to R ₁ = 0.090 for 4409 reflections with |F _hkl ≥ 4σ|F _hkl |. The structure is based on [(UO₂)₅(SeO₄)₈(H₂O)₅]⁶⁻ layers arranged parallel to the (101) plane; these layers have a unique topological structure. The U(1)O₆(H₂O) and U(3)O₆(H₂O) linked through selenate groups form chains running along [ [`1]\bar 1 01] direction. The chains are combined in layers by U(2)O₆(H₂O) bipyramids. The layers are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups located between the layers.