寒冷地区结冰现象对混凝土面板堆石坝接缝止水体系的影响

针对北方冬季寒冷低温条件,研究了结冰现象对止水体系锚固系统安全性的影响程度。通过实验室模型试验,模拟测定了不同降温速率下结冰所产生的冻胀对锚固系统的拉拔破坏力值及冰与螺栓冻结强度、冰与扁钢压条及橡胶盖板的冻结强度等参数。研究了冻融循环对膨胀螺栓C30混凝土的锚固力及不同灌封型式的影响。在分析水位变化引起的冰盖对止水锚固系统的破坏作用基础上,结合试验测试结果,提出了寒冷地区止水锚固体系设计施工中应注意的主要问题和建议。     

Improving performance of proton ceramic electrolysis cell perovskite anode by Zn doping

As an important renewable energy, hydrogen energy becomes an important part of the future energy system. Proton ceramic electrolysis cell (PCEC) enables the efficient, clean, large-scale preparation of hydrogen, which is a new type of energy conversion device, attracting the attention of many researchers. Sr₂Fe_1.4Zn_0.1Mo_0.5O_6-δ (SFZM) anode materials were developed to investigate the effect of B-site doping of Zn on the electrochemical properties of the Sr₂Fe_1.5Mo_0.5O_6-δ (SFM) materials. The results reveal that the doping of Zn increases the concentration of oxygen vacancies and improves the electrocatalytic activity, which in turn improves the performance of the material. A current density of 408 mA cm⁻² has been achieved at 1.3 V when the SFZM-based single cell was operated in an electrolysis mode (50% H₂O in air) at 600 °C, higher than SFM-based single cells (286 mA cm⁻² at 1.3 V). In addition, the SFZM-based single cell exhibited good durability in a stability test at an electrolysis current density of 408 mA cm⁻². This work confirms that SFZM is a promising material for proton ceramic electrolysis cell anode.     

Structure and thermal properties of SrCe1-xSnxO3 (x=0.1 … 0.5) as a promising thermal barrier coating

Gas turbines efficiency growth is primarily associated with an increase in the operating temperature of the combustion chamber, which places new stringent requirements on the materials of thermal barrier coatings. Strontium cerate doped with tin SrCe_{1- x}Sn_xO₃ where x = 0.1 … 0.5, was proposed as a promising material. The research has shown that the lightly doped solid solution SrCe_1-xSn_xO₃ has an orthorhombic Pnma structure at x < 0.3, whereas at a high content of Sn⁴⁺ the monoclinic structure P2₁/m becomes more favorable. Thermogravimetric analysis (TGA) in reducing atmosphere (5%H₂ in Ar) shows no mass lost as a result of unchangeable charge of Ce⁴⁺ and Sn⁴⁺. An increase in the distortion of the crystal lattice, due to the large difference in the ionic radii of Ce⁴⁺ and Sn⁴⁺, leads to a deterioration in the symmetry of the crystal lattice, a reduction of thermal conductivity (from 1.9 to 1.4 W m⁻¹ K⁻¹ at 1000 °C) and at the same time, growth of hardness and porosity. The increase in porosity, along with an increase in the required temperature of solid-state synthesis, indicates an enhancement in the melting point of the obtained materials. For the compounds with an orthorhombic structure, the thermal expansion coefficient increases with a growth in the Sn content, achieving a highest point 12.47·10⁻⁶ K⁻¹ at 1100 °C for x = 0.3. The combination of the revealed properties and their comparison with advanced refractories makes the solid solution, primarily SrCe_0.5Sn_0.5O₃, a promising material for application as thermal barrier coatings.     

Preparation of In0.5Sc1.5Mo3O12 nanofibers and its negative thermal expansion property

Orthorhombic In_0.5Sc_1.5Mo₃O₁₂ nanofibers were prepared by electrospinning followed by a heat treatment. The effects of post-annealing temperatures on the phase composition, microstructure and morphology were investigated by XRD, SEM, HRTEM and XPS. Negative thermal expansion (NTE) behaviors of the In_0.5Sc_1.5Mo₃O₁₂ nanofibers were analyzed by high-temperature XRD. Results indicate that the as-prepared In_0.5Sc_1.5Mo₃O₁₂ nanofibers show an amorphous structure with smooth and homogeneous shape. The average diameter of the as-prepared In_0.5Sc_1.5Mo₃O₁₂ nanofibers is around 515 nm. Well crystallized orthorhombic In_0.5Sc_1.5Mo₃O₁₂ nanofibers could be prepared after post-annealing at 550 °C for 2 h with an average diameter of about 192 nm. The crystallinity of In_0.5Sc_1.5Mo₃O₁₂ nanofibers gradually improved with the increase of annealing temperature. However, too high post-annealing temperature leads to a damage of sample's fiber structure. The high-temperature XRD results reveal that In_0.5Sc_1.5Mo₃O₁₂ nanofibers show an anisotropic NTE, and the coefficients of thermal expansion (CTEs) along a-axis and c-axis were −5.95 × 10⁻⁶ °C⁻¹ and -3.54 × 10⁻⁶ °C⁻¹, while the one along b-axis is 5.61 × 10⁻⁶ °C⁻¹. The volumetric CTE of In_0.5Sc_1.5Mo₃O₁₂ nanofibers is −3.90 × 10⁻⁶ °C⁻¹ and the linear one is 1.3 × 10⁻⁶ °C⁻¹ in 25–700 °C.     

Determinations of Ce solid solution mechanism and limit thermal conductivity of YTaO4 ceramics

x mol% CeO₂-YTaO₄ (x = 0, 3, 6, 9, 12) ceramics have been synthesized by the spark plasma sintering (SPS) technique. We focus on the changes in lattice distortion, bonding length, thermal conductivity, thermal expansion, and phase stability of the prepared samples. XRD, Raman, and XPS are used to determine the chemical valence and solid solution mechanism of Ce in the lattice of YTaO₄, while its effects on thermal/mechanical properties are elucidated from microstructures. Y³⁺ is substituted via Ce³⁺, and all samples maintain a monoclinic phase. The limit thermal conductivity (1.2 W?m^?1?K^?1, 900 °C) is realized in 9 mol% CeO₂-YTaO₄, and the thermal expansion coefficients are increased to 10.2 × 10^?6 K^?1 at 1200 °C. Furthermore, the exceptional phase stability and mechanical properties of all samples indicate that they can provide good thermal insulation at high temperatures, and have higher working temperatures than the current YSZ thermal barrier coatings.     

新疆大石峡水利枢纽混凝土碱-硅酸反应抑制研究

新疆大石峡水利枢纽混凝土选用的骨料存在碱活性,可能导致工程产生碱骨料破坏问题,本文研究了当地粉煤灰和矿粉对碱-硅酸反应(ASR)的影响,并采用XRD和SEM-EDS测试分析了水化产物和界面过渡区的形态。结果表明：粉煤灰掺量≥20%(质量分数)或矿粉掺量≥40%(质量分数)都能显著抑制碱-硅酸反应;在纯水泥样品界面过渡区可以观察到无定形相,在含有粉煤灰或矿粉的样品中未观察到无定形相,这意味着碱-硅酸反应发生在纯水泥样品中;添加粉煤灰或矿粉降低了界面过渡区物相的Ca/Si摩尔比,抑制了碱-硅酸反应。     

Thermal expansion and Young's modulus evolution of fused silica and crystalline silica-containing materials

Fused silica bricks (FSBs) with exceptional thermal shock resistance are frequently used to repair localized damage in coke ovens and are hold promising candidates for the efficient construction of new coke ovens. To maximize their utilization, the effects of thermal history on the thermal expansion and Young's modulus evolution of FSBs were investigated in comparison to crystalline silica bricks (CSBs). Due to the gradual phase transformation of fused silica into cristobalite, the thermal expansion of FSBs are sensitive to the thermal cycle; both silica materials exhibit an increase in thermal expansion after five cycles at 1200°C, whereas the thermal expansion of CSBs is five times greater than that of FSBs. When the testing temperature is less than 1000°C, Young's modulus of CSBs is more sensitive to the thermal history, which is caused by phase transformation-induced microcracks. This sensitivity reduces when the testing temperature is 1200°C, as microcracks healed by liquid phase as well as the softening of residual glass phase. By contrast, when the testing temperature is 1200°C, Young's modulus of fused silica specimens is sensitive to the thermal history owing to the microcracks caused by the gradual phase transformation of fused silica to cristobalite.     

菜籽膨化浸出工艺改造实践

研究了将菜籽预榨浸出改造为膨化浸出的工艺设备和操作参数的调整。实践证明：膨化浸出不仅可以提高产量、降低能耗，而且可以增加精炼率，改善油脂和菜籽粕的质量。     

电化学氧化羊毛表面的物理性质

通过电解锰酸钾化合物的水溶液得到高锰酸钾饱和盐溶液并对羊毛表面进行氧化．将电化学氧化前后的羊毛进行表面结构、断裂强度、摩擦系数的测定，对电化学氧化与高锰酸钾饱和盐溶液直接氧化后的羊毛进行比较与研究．结果表明：羊毛表面结构的改变对羊毛物理性质有显著影响，电化学氧化较高锰酸钾直接氧化后的羊毛具有明显优势．     

提高脱硫系统扩容改造后的供电可靠性

为满足珠海电厂脱硫系统扩容改造取消旁路后厂用电系统供电的稳定性和可靠性,通过对电厂的厂用电系统进行分析、综合考虑,设计了脱硫系统厂用电的改造方案。经过对比,选取每台发电机脱硫系统配置3段6 kV母线的改造方案,以满足脱硫系统改造后供电系统安全、稳定运行的需求。按优选的电气方案改造后,效果良好。