腐蚀产物中Zn5(OH)8Cl2对纯Zn腐蚀行为的影响

目的 探究纯Zn腐蚀产物中碱式氯化锌(Zn5(OH)8Cl2,ZHC)对其腐蚀防护性能的影响以及腐蚀防护机理。方法 通过原位生长法在纯Zn表面制备一层ZHC膜。通过X射线光电子能谱仪(XPS)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS),分析了样品的物相组成和微观形貌。通过电化学阻抗谱(EIS)和动电位极化曲线(Tafel),评估了ZHC膜对纯Zn腐蚀防护性能的影响。结果 纯Zn表面先形成了一层致密细小的ZHC纳米片,铺满整个纯Zn表面后,在第一层ZHC上形成第二层较大尺寸的ZHC纳米片。预制备的ZHC膜可以使纯Zn的腐蚀电流密度从78.23 μA/cm²降低到2.08 μA/cm²,腐蚀电位从‒1.050 V(vs. SCE)提升到‒0.998 V(vs. SCE),并且随着ZHC制备时间的增加,阴极斜率(βc)逐渐增大,这表明ZHC可以有效阻碍电荷转移,抑制阴极的氧还原,减缓纯Zn的腐蚀速率,对Zn基体的腐蚀起到防护作用。在浸泡腐蚀过程中,ZHC可以抑制HZ的生成,减少絮状腐蚀产物的生成。在短期浸泡过程中,纯Zn的阻抗值随着预制备ZHC的增加而逐渐增大,这是因为生成的腐蚀产物填补ZHC纳米片的空隙,使腐蚀产物膜致密,ZHC膜对Zn基体能起到较好的防护作用。在长期浸泡过程中,ZHC/Zn的阻抗值下降,这是因为ZHC膜破裂,提供了新的腐蚀通道,导致ZHC膜对纯Zn的防护作用下降。结论 ZHC膜可以减缓纯Zn的腐蚀速率。对比纯Zn和ZHC/Zn在浸泡过程中的腐蚀行为可知,在短期浸泡过程中,随着预制备ZHC的增加,对纯Zn的防护性能逐渐提高;在长期浸泡腐蚀过程中,ZHC膜对纯Zn腐蚀的防护作用逐渐下降。     

Deformation and fracture of NiAl single crystals tested in torsion

Binary NiAl single crystals were tested in torsion. [001] oriented samples exhibited lower shear strength and higher shear strain to failure compared to [110] oriented samples. Transmission electron microscopy revealed an increasing dislocation density from the center of the sample to the outer surface. Most dislocations that were analyzed were of the b= <100= type, however, some 〈110〉 type dislocations were observed in the [110] oriented samples. Electron backscatter patterns and tilting experiments were used to determine the crystallography of two types of facets on failed samples: those near {112} and those ∼10° away from {001}.     

Selection of geotextiles for use with synthetic drainage products

The selection of a geotextile to be used in conjunction with a synthetic core in a drainage layer should be part of the design process. Due to the large number of variables affecting the performance of the drainage layer it may be difficult to evaluate which geotextile would provide the best performance for a particular application. The decision analysis technique described in the paper provides a logical and methodical approach for comparing index or design test data to rank the geotextile in each performance area expected to affect the overall performance of the drainage layer.     

Enhanced energy storage performance in samarium and hafnium co-doped silver niobate ceramics

Improving energy storage density and efficiency of antiferroelectric materials could promote their use within energy storage field, particularly in the context of pulsed power sources. In this study, Sm and Hf co-doped silver niobate (AgNbO₃; AN) ceramics were prepared using traditional solid-state method. Comprehensive analysis of crystal structure, microstructure, defects, absorbance, and energy storage performance of the material was conducted. Results reveal that co-doping increased the concentration of cation vacancies and band gap, decreased the M₁–M₂ and M₂–M₃ phase transition temperatures, and enhanced the antiferroelectric phase stability and energy storage performance. The (Ag_0.955Sm_0.015)(Nb_0.95Hf_0.05)O₃ ceramic exhibited energy storage density of 5.35 J/cm³ and energy storage efficiency of 73% at electric field (E) of 295 kV/cm, demonstrating significant improvement. The (Ag_0.955Sm_0.015)(Nb_0.95Hf_0.05)O₃ ceramic exhibited excellent thermal stability (<5% in the range of 25 °C-125 °C) and frequency stability (<3% in the range of 1–100 Hz under E = 290 kV/cm). Additionally, the (Ag_0.955Sm_0.015)(Nb_0.95Hf_0.05)O₃ ceramic exhibited ultrahigh discharge speed (∼18 μs) and high discharge energy density (4.9 J/cm³). These advantages make these ceramics promising materials for energy storage applications.     

Stability of low pressure chemical vapour deposition amorphous silicon

The study of the influence of phosphorous doping and hydrogen content on transport properties and thermally induced metastability of low pressure chemical vapour deposition a-Si is reported. Introduction of hydrogen causes change of dominant carrier transport mechanism at room temperature. The thermally induced metastability was observed in both unhydrogenated and hydrogenated P-doped a-Si films. In this paper we report our studies on the effect of the thermally induced metastability in unhydrogenated and hydrogenated films of LPCVD a-Si, as a function of phosphorous concentration.     

First time in-situ investigation of 2223 formation measured on (Bi,Pb)2Sr2Ca2Cu3O10+x thick films on Ag tape prepared by the screen printing technique

Detailed investigations were performed on the reaction kinetics of the superconducting BPSCCO 2223 phase in order to be able to improve tape processing and critical current density J_c of 2223 layers on Ag tape made by the organic binder method. The J_c values presently vary between 6–12 × 10³A/cm² (77 K, O T). To our knowledge, it is the first time that the formation of the 2223 has directly been observed employing in-situ high temperature X-ray diffraction (HTXRD). This measurement was carried out on screen printed samples of BPSCCO on Ag foil heated in a specially designed closed crucible preventing the evaporation of lead. The main findings are that the 2223 phase arises from the 2212 phase at 820–835°C within a short timescale of about 2–3 h. These results were correlated with measurements on a Simultaneous Thermal Analysis (STA) showing endothermic reactions which indicate the starting of partial melting at about 825–836°C. According to the literature we found that the reaction kinetics are controlled by diffusion processes under the presence of partial melt.     

Photoelectrochemical behaviour of Zn3In2S6 single crystals in aqueous solutions

The basic photoelectrochemical behaviour and some physical quantities of the ternary semiconductor n-Zn₃In₂S₆ have been investigated for the first time. From the photocurrent actions spectrum in 1M Na₂SO₄ a direct optical band gap energy (E_g) equal to 2.81 eV has been determined. From capacity measurements a flat band potential (V_FB 0 − 1.29 V SCE) has been calculated, as well as the donor density, the conduction and the valence band edge. With pH increasing, a shift of the photocurrent onset potential (V_on) to more cathodic values has been observed. The presence of redox systems such as Na₂S/NaOH, Na₂SO₃, K₃[Fe(CN)₆]/ K₄[Fe(CN)₆], Ce³⁺/Ce⁴⁺ improves the stability of the electrodes and produces reasonable photovoltages.     

杂质镓对纯铝表面锆钛转化膜的组织及耐腐蚀性能的影响

目的 探究杂质镓对纯铝锆钛转化膜的生长规律和防护性能的影响。方法 采用扫描电化学显微镜(SECM)技术表征了含镓纯铝表面锆钛转化膜在3.5%(质量分数)NaCl溶液中局部腐蚀的演变过程,结合X射线衍射仪(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)等技术分析了镓对纯铝锆钛转化膜的组织及成分的影响规律,采用开路电位法(OCP)、电化学阻抗技术(EIS)以及极化曲线(Tafel)等探究了杂质镓对纯铝表面转化膜的生长和耐腐蚀性能的影响规律。结果 锆钛转化膜主要由冰晶石Na₃AlF₆、氧化物(如TiO₂、ZrO₂、Al₂O₃)和有机金属络合物组成;杂质镓的添加会抑制铝表面转化膜的生长,破坏膜层的完整性。随镓含量(质量分数)从0%增大到0.5%,锆钛转化膜阻抗值从4.75×10⁴?·cm²不断减小到2.49×10³?·cm²,自腐蚀电流密度由0.45μA增加到13.4...     

High energy storage density and efficiency in AgNbO3 based relaxor antiferroelectrics with reduced silver content

Silver niobate based lead-free antiferroelectric ceramics have demonstrated great advantages, but the high consumption of noble metal silver may restrict their commercial application. In this work, Na⁺ and Ta⁵⁺ co-modified (Ag_1-xNa_x)(Nb_1-yTa_y)O₃ (100xNa-100yTa) ceramics were investigated, aiming to reduce the silver consumption and achieve good energy storage properties. The Na⁺ tended to increase M2-M3 phase transition temperature (T_M2-M3), while Ta⁵⁺ was more likely to reduce T_M2-M3. A new current peak (E_R) was observed for the first time in all current-electric field curves. As expected, a room temperature M2-M3 phase boundary with relaxor AFE property was realized in 40Na-65Ta with obviously reduced silver content, in which high recoverable energy storage density (W_rec) of 6.5 J/cm³ and good energy storage efficiency (η) of 78% were achieved. This work demonstrates a strategy to realize relaxor antiferroelectrics in AgNbO₃ based ceramics for energy storage performance, and promotes the commercialization potential.     

Efficient energy transfer of Ce to Nd in SrF2 transparent ceramics for enhancing NIR emission

High optical quality Nd³⁺ and Ce³⁺ co-doped SrF₂ (Nd³⁺, Ce³⁺: SrF₂) transparent ceramics were fabricated successfully by a simple hot-pressing (HP) method. The phase composition, in-line transmittance, absorption and emission spectra, as well as the detailed energy transfer of Nd³⁺ and Ce³⁺ were investigated. In addition, the Judd- Ofelt (J-O) theory was adopted to evaluate the luminescence property. The SrF₂ transparent ceramic samples exhibited excellent optical properties, up to 82 % at 400 nm and 92.5 % at 1054 nm. The fracture surface of SrF₂ transparent ceramic proved nearly dense microstructure and EDS results demonstrated uniform doping. The addition of cerium ions changed the crystal field environment of neodymium ions and shifted the emission peak to higher wavelengths at 796 nm excitation. Moreover, through the energy transfer process of Ce³⁺ to Nd³⁺, the occurrence of concentration quenching phenomenon was avoided under 298 nm excitation, and the emission cross-section of ⁴F_3/2→⁴I_11/2 increased to 3.1 × 10⁻²⁰ cm².