硝酸铈添加剂对7075铝合金微弧氧化陶瓷膜特性的影响

为进一步提高7075铝合金的表面耐磨性,在硅酸钠、六偏磷酸钠复合电解液中加入不同质量浓度的硝酸铈添加剂,运用微弧氧化技术在其表面原位生长出氧化铝陶瓷膜。采用涂层测厚仪、维氏硬度计、扫描电子显微镜(SEM)、X射线衍射议(XRD)等方法研究了硝酸铈添加剂对陶瓷膜厚度、显微硬度、表面形貌、相组成以及耐磨性的影响。结果表明:陶瓷膜主要由α-Al2O3和γ-Al2O3两相组成,当硝酸铈质量浓度为0.12g/L,陶瓷膜的厚度达到最大,约为18μm;硬度达到最高,约为916HV0.2;致密性最佳;陶瓷膜表现出更好的耐磨性能。     

磷酸盐体系电解液对铝合金微弧氧化层性能影响研究

采用微弧氧化法在铝合金(ZL101A)基体上制备陶瓷膜层。研究了不同电解液和添加剂对涂层硬度、厚度及相组成的影响。结果表明:膜层厚度、硬度随NaH2PO3和(NaPO3)6的增加而提高。XRD相结构分析表明:涂层中的主要相为γ-Al2O3、α-Al2O3和Mg2Al4Si5O18,随α-Al2O3相增多,膜层的耐蚀性升高。     

铝合金微弧氧化复合工艺制备陶瓷膜的油摩擦特性

为改善7075铝合金微弧氧化陶瓷膜性能,利用恒流-恒压复合工艺制备微弧氧化陶瓷膜。采用涂层厚度仪、显微硬度计测量陶瓷膜厚度、显微硬度;采用扫描电镜(SEM)和X射线衍射仪(XRD)分析陶瓷膜的表面形貌、磨痕形貌和相组成;采用摩擦磨损试验机研究陶瓷膜油摩擦特性。结果表明:在氧化时间为75 min(恒流)-30 min(恒压)时,陶瓷膜平均厚度达到81μm,陶瓷膜致密层硬度达到1648 HV;陶瓷膜主要由α-Al_2O_3和γ-Al_2O_3组成;微弧氧化陶瓷膜微孔结构有利于改善油润滑条件下的耐磨性;在油润滑条件下,摩擦系数和磨损量随着转速的增大而变大。     

铝合金表面微弧氧化涂层制备工艺设计

用微弧氧化技术对铝合金表面进行强化处理,利用正交试验设计优化试验方案,按五因素(Na2SiO3浓度、KOH浓度、H3BO3浓度、H2O2浓度、微弧氧化电压)、四水平得到正交表,合理安排微弧氧化试验,达到优化微弧氧化工艺条件的目的;并用综合平衡法评价各因素对陶瓷膜硬度和厚度影响的主次顺序和可能最优水平.结果表明,铝合金微弧氧化陶瓷膜的硬度和厚度受各因素水平的影响显著,其中Na2SiO3的浓度对陶瓷膜硬度和厚度两指标的影响最大;在最优工艺条件下(Na2SiO3浓度6 g/L、H3BO3浓度1.5 g/L、KOH浓度0.5 g/L、H2O2浓度X4、微弧氧化电压340 V),陶瓷膜致密层硬度达到1 700 HV,膜层总厚度约200 μm.     

铜基表面铸渗法Ni/Al2O3复合渗层的组织和性能

为了提高铜合金表面的耐磨性和抗高温氧化性,用负压铸渗工艺,在铜基表面制备了不同Al2O3含量的Ni/Al2O3复合渗层,渗层厚度0.5~2 mm。用扫描电镜(SEM)、X射线衍射和电子探针(EPMA)等方法,测定了渗层的显微结构、化学成分分布、硬度、结合强度等。结果表明:渗层包括复合渗层和过渡层,Al2O3颗粒分布均匀,渗层组织致密,界面结合良好,在Al2O3颗粒之间以及渗层与基体之间无裂纹产生;渗层主要由Ni基固溶体、Al2O3颗粒、Ni31Si12、Ni3B相组成,能显著地提高铜合金表面的硬度、强度和耐磨性。     

纯铝微弧氧化陶瓷层的相组成及性能

采用微弧氧化设备,在电压410 V、Na2SiO3浓度80 g/L、电流10 A、氧化时间12 min条件下,在纯Al表面获得了厚度为22 μm的陶瓷膜层.采用X射线衍射及扫描电镜并结合能谱仪研究了膜层的相组成、形貌及化学成分;分析了膜层相组成的形成机制.研究表明:膜层表面凸凹不平,它由膜层基体和大量的孔洞组成,主要包含O、Si、Al元素.组成相包含非晶相和晶相,非晶相包含SiO2和Al2O3,晶相为Al相.膜层的粗糙度为2.0 μm,显微硬度为2 200 HV,绝缘电阻值为5 MΩ.     

铝合金表面微弧氧化陶瓷层耐磨性

利用微弧氧化技术在7075铝合金表面形成微弧氧化陶瓷膜层,通过SEM、XRD手段分析了微弧氧化陶瓷层的显微结构、表面形貌和相组成,并在HIT-Ⅱ摩擦磨损试验机上测试了陶瓷膜层的摩擦学性能.结果表明:7075铝合金表面的微弧氧化陶瓷膜层由疏松层、致密层构成,其相组成主要是α-Al2O3和γ-Al2O3两相;氧化陶瓷层与基体结合良好,厚度为25～45μm,表面硬度可达到1900HV0.1左右;微弧氧化表面处理技术可以显著提高铝合金的表面耐磨性,在与GCr15钢球对磨时,膜层具有较低的磨损率,但摩擦因数相对较高.     

LY12铝合金微弧氧化尺寸变化及膜层相组成

采用螺旋测微器并结合涡流测厚仪,研究了LY12铝合金微弧氧化过程中的尺寸变化.在质量浓度为100 g/L的Na2SiO3溶液中,在电压为550 V、电流为25 A、氧化时间为75 min条件下,获得了厚度为30μm的稳定的陶瓷膜层.采用X 射线衍射仪及扫描电镜并结合能谱仪研究了膜层的相组成、形貌及元素分布;分析了膜层相组成的形成机理.研究表明,微弧氧化使试样尺寸变大、基体尺寸变小,膜层外延生长和基体损耗的厚度是等距离的.膜层是由膜层基体和大量的直径只有几微米的孔洞组成,主要包含O、Si和Al元素;组成相包含非晶相和晶相,非晶相包含Al2O3和SiO2,晶相为Al相.膜层显微硬度(HV)为2 200.     

纳米Cr2O3微粒对2024-T4微弧氧化膜结构及耐磨性能的影响

摘 要: 在含有不同浓度纳米Cr2O3微粒的硅酸盐体系电解液中对2024-T4铝合金进行微弧氧化处理,使用SEM观察陶瓷膜的表面形貌和截面形貌,使用EDS能谱仪分析膜层中各主要成分沿截面方向的分布,使用XRD分析陶瓷膜的相结构,使用纳米压痕硬度计测量陶瓷膜的硬度,使用粗糙度仪测量陶瓷膜的表面粗糙度,使用摩擦磨损试验机测量陶瓷膜的摩擦系数,使用激光共聚焦显微镜测量磨痕体积,评估磨损率,使用SEM观察磨痕形貌,结果表明：在电解液中加入纳米Cr2O3微粒后,制备的陶瓷膜中出现了Cr2O3相,电解液中纳米Cr2O3微粒浓度达到2.4g/L时,陶瓷膜的硬度最高,摩擦系数最小,磨损率最低,耐磨性最好。     

高Si压铸Al合金ADC12的微弧氧化表面改性

利用恒流微弧氧化技术,在以Na2SiO3和Na3PO4为主盐的电解液中,在高硅压铸Al合金ADC12表面制备了陶瓷膜．显微硬度及耐蚀性能测试表明,陶瓷膜显微硬度（HV）高达1430,能对基体金属提供有效的防护．涡流测厚及SEM研究显示,该陶瓷膜厚度分布比较均匀,具有双层结构．EDX和XRD分析表明,该微弧氧化陶瓷膜的主要元素组成为0,Al,Si和P;主要相组成为γ-Al2O3和α-Al2O3,同时含有少量χ-Al2O3,θ-Al2O3和Al2SiO5晶体．     

Crystal structures and structural relationships of KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2

The new phases KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe₂(SeO₂OH)(SeO₃)₃: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 ų, Z = 2; SrCo₂(SeO₂OH)₂(SeO₃)₂: space group P2ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 ų , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively.

The atomic arrangement in KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ is based on isolated MO₆ octahedra (M = Fe³⁺, Co²⁺), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se⁴⁺ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe₂(SeO₃)₄ by distance least squares refinement (program ).     

Raman active phonons of RFe3(BO3)4, R=La or Nd, single crystals

Oriented single crystals of RFe₃(BO₃)₄, with R=La or Nd, have been studied by Raman spectroscopy. Spectra with the relevant polarization configurations have been recorded in order to obtain the symmetry of the observed phonons. The factor group analysis and the correlation with the free (BO₃)³⁻ ion are done in order to identify most of the phonons associated with the two different types of (BO₃)³⁻ ion present in the crystal. The number and symmetries of the optical Raman active modes are 7A₁+19E, among which 4A₁+8E can be assigned as mostly due to (BO₃)³⁻ vibrations. 7A₁+18E modes were observed.

The highest energy peaks have been assigned to the regular planar (BO₃)³⁻ and to the three irregular (BO₃)³⁻ groups. The two lowest energy peaks of A₁ symmetry (around 180 and 300 cm⁻¹) are very probably related to the BO₃ rotatory mode and to Fe displacements. R ions do not participate in A₁ symmetry modes. The E mode around 90 cm⁻¹ (the lowest frequency mode) is probably due to the R ions which have the longest bonds and are the heaviest ions.     

孔道Al2O3/SiO2对NaAlH4-Tm2O3体系储氢性能的影响

以机械球磨法制备具有可逆吸放氢性能的NaAlH4-Tm2O3储氢材料体系。利用相同制备方法进一步研究两种不同孔道材料(大孔Al2O3与介孔SiO2)对NaAlH4-Tm2O3体系储氢性能的影响,测试样品的循环吸放氢性能,并对样品吸放氢前后的结构进行表征。结果表明:大孔Al2O3材料的添加并不能明显改善NaAlH4-Tm2O3体系的放氢速率和放氢量,而介孔SiO2的加入使NaAlH4-Tm2O3体系在150℃条件下5 h内的首次放氢量(质量分数)达到4.61%,高于NaAlH4-Tm2O3体系的4.27%,增加了约8.0%。此外,添加介孔SiO2的NaAlH4-Tm2O3体系放氢速率也有所提高。     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

Thermal cycle behavior of plasma sprayed La2O3, Y2O3 stabilized ZrO2 coatings

The effects of La₂O₃ addition on thermal conductivity, phase stability and thermal cycle life of Y₂O₃ stabilized ZrO₂ plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La₂O₃ addition, it tended to also result in lower phase stability and thermal cycle life of the coatings. Optimization of the composition and structure of the coatings improved these properties, and the optimized coatings showed prolonged thermal cycle life.     

Polymorphic phase transition-induced electrical behavior of BiCoO3-modified (K0.48Na0.52)NbO3 lead-free piezoelectric ceramics

(1 − x)(K_0.48Na_0.52)NbO₃-xBiCoO₃ [KNN-xBC] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. The effects of the BiCoO₃ addition on the phase structure, dielectric, piezoelectric and ferroelectric properties of KNN-xBC ceramics were systematically investigated. The polymorphic phase transition (PPT) from rhombohedral to orthorhombic phase around room temperature was identified in the composition range of 0.01 ≤ x ≤ 0.02, and the improved electrical properties were induced by this PPT. The KNN-0.01BC ceramics near PPT exhibit optimum electrical properties: d₃₃ ∼ 165 pC/N, k_p ∼ 0.40, P_r ∼ 31.0 μC/cm², and E_c ∼ 12.6 kV/cm. These results indicate that the enhanced piezoelectric properties for alkali niobate can be achieved by forming the coexistence of rhombohedral and orthorhombic phases.     

Surface modification of spherical LiNi1/3Co 1/3 Mn1/3O2 with Al2O3 using heterogeneous nucleation process

To improve the cycle stability at high voltage and high charge/discharge rate, spherical LiNi1/3Co1/3Mn1/3O2 was coated with Al2O3 by using heterogeneous nucleation process, and the physical and electrochemical properties were studied. The SEM images show that there is a uniform coating on the modified spherical LiNi1/3Co1/3Mn1/3O2. The electrochemical tests indicate that the properties of LiNi1/3Co1/3Mn1/3O2 coated with 0.5% aluminum oxide are the best. The initial capacities are 150 and 173 mA.h/g at the rate of I C in the voltage range of 2.7-4.3 V and 2.7-4.6 V, respectively, and the discharge capacities maintain about 99% and 85% after 30 cycles, respectively. While those of the bare LiNi1/3Co1/3Mn1/3O2 are only 90% and 75%, respectively. The CV tests of LiNi1/3Co1/3Mn1/3O2 show that Al203-coating can restrain the oxide-reduction peak currents fading during the charge/discharge course.     

Thermochemistry of GaBO3 and phase equilibria in the Ga2O3–B2O3 system

Employing a Tian-Calvet-type calorimeter operating in the scanning mode at temperatures from 1120 to 1220 K, the enthalpy change, Δ_dH, associated with the decomposition of GaBO₃ (=1/2β-Ga₂O₃+1/2B₂O₃(liq.)) and the corresponding decomposition temperature, T_d, were determined: Δ_dH=30.34±0.6 kJ/mol, T_d=1190±5 K. Using the transposed-temperature-drop method the thermal enthalpy, H(T)−H(295 K), of GaBO₃ was measured as a function of temperature, T, in the region from 760 to 1610 K; the results obtained are

[H(T)−H(295 K)]/(J/mol)=104.8·(T/K)−31 300 (760 K<T<1190 K),

[H(T)−H(295 K)]/(J/mol)=138.8·(T/K)−41 480 (1190 K<T<1590 K).

On the basis of the experimental results, the enthalpy and entropy of formation, Δ_fH and Δ_fS, respectively, of GaBO₃ from the component oxides were derived:

Δ_fH=−30.34 kJ/mol,Δ_fS=−25.50 J/(K·mol) at 1190 K,

Δ_fH=−10.55 kJ/mol,Δ_fS=−5.48 J/(K·mol) at 298 K.

The enthalpy versus temperature curve shows, apart from a step associated with the decomposition of GaBO₃, a further step at 1593 K which is attributed to a monotectic equilibrium.     

Li2CO3掺杂BaTiO3无铅压电陶瓷的低温烧结

以Li2CO3作为烧结助剂,采用传统固相烧结法制备BaTiO3陶瓷。研究了烧结温度(1000~1150℃)和Li2CO3添加质量分数(0%~5%)对BaTiO3陶瓷结构和电学性能的影响。结果表明:Li2CO3的掺入有效地促进了陶瓷的烧结,使BaTiO3的烧结温度从1300℃以上降低到1050℃。X射线衍射结果表明:未掺Li2CO3的BaTiO3陶瓷样品为四方相结构,掺Li2CO3的BaTiO3陶瓷样品为正交相结构。Li2CO3掺量为1%的陶瓷样品具有较高的致密度,且在1050℃时获得最大值,其相对密度可达94%。当烧结温度为1100℃时,BaTiO3陶瓷的压电常数d33获得最大值,且d33随着Li2CO3掺量的增加而降低。其中Li2CO3掺量为1%时陶瓷具有较好的电性能:d33=200pC/N,εr=1322,TC=115℃。     

Ba(Mg1/3Ta2/3)O3热障涂层的制备及抗热震性能研究

本文以BaCO₃、MgO、Ta₂O₅为原料,采用固相反应法合成了Ba(Mg_1/3Ta_2/3)O₃(简称BMT)陶瓷粉末,利用大气等离子喷涂技术制备了BMT/YSZ双层陶瓷涂层。利用XRD、SEM和金相显微镜检测了BMT粉体及涂层的物相组成和显微结构。采用水淬法考核了涂层的抗热震性能。结果表明：1450℃下煅烧4h可合成出具有复合钙钛矿结构的BMT粉末,粉末具有良好的高温相结构稳定性。等离子喷涂制备的BMT/YSZ涂层组织致密,涂层系统中各界面结合紧密。涂层在室温至1150℃间热震9次后发生片状剥落,剥落位置位于BMT层间,BMT材料低的断裂韧性和第二相Ba₃Ta₅O₁₅的存在是导致涂层失效的主要原因。