Tailorable thermal expansion in leucite-pollucite materials derived from geopolymers for environmental barrier coatings

The K[AlSi₂O₆]-Cs[AlSi₂O₆] pseudo-binary system was synthesized by geopolymer crystallization. The thermal expansion properties of these materials were studied by in situ high-temperature X-ray diffraction to characterize thermal expansion behavior for potential application as environmental barrier coatings. Tailorable thermal expansion through changing cation stoichiometry allowed reduced thermal expansion mismatch with SiC_f/SiC composites compared to rare-earth-based coatings.     

Multidisciplinary approach for investigating the hot corrosion behavior of thermal barrier coatings

Herein, we propose a new multidisciplinary approach for investigating the corrosion behavior of thermal barrier coatings, combining the thermal-gradient mechanical fatigue method with hot corrosion tests. Corrosive salts (Na₂SO₄; V₂O₅) of varying concentrations (10−20 mg/cm²) were deposited on the surface of yttria-stabilized zirconia (YSZ) coatings to evaluate the microstructural changes occurring during the reaction, via thermal graded mechanical fatigue tests. The tests were conducted at a surface temperature of 1150 °C in 10 min cycles and underwent applied uniaxial tensile loads. The corrosion tests show that the ZrV₂O₇ plays an important role as an intermediate in the collapse of the lamellar structures during the reaction, which results from the repetitive precipitation of V₂O₅ and m-ZrO₂ from the ZrV₂O₇. The microstructure of corroded YSZ coatings exhibited a different degradation mechanism under a thermomechanical environment, compared with the testing under isothermal atmospheric conditions.     

带束层膨胀对轮胎接地印痕的影响研究

研究带束层膨胀对轮胎接地印痕的影响。对比多种普通带束层膨胀的钢丝帘线角度变化法则,分析普通带束层膨胀对轮胎接地印痕仿真准确性的影响;探讨0°带束层钢丝帘线的特性,提出考虑0°带束层预应变的轮胎性能仿真方法,并分析0°带束层预应变对轮胎接地印痕的影响。本研究结果可为轮胎的结构设计、工艺设计和仿真分析方面提供指导。     

热膨胀法判定建窑黑瓷烧成温度的应用研究

以热膨胀仪判定建窑黑瓷烧成温度的研究为例,综合运用多种测试方法对建窑黑瓷标本进行了系统研究,探讨如何从建窑黑瓷胎体重烧热膨胀曲线中筛选有效转折点的问题及其转折点的形成原因。研究表明:(1)建窑黑瓷胎体重烧热膨胀曲线上有三个转折点,分别为收缩转折点、膨胀转折点和急剧收缩点。其中第一个收缩转折点是判定其古代烧成温度的关键点。(2)建窑黑瓷胎体重烧热膨胀曲线上膨胀转折点和急剧收缩点的形成皆与其胎体中大量Fe_2O_3在高温下发生分解反应有关。该研究不仅为热膨胀仪测定建窑黑瓷烧成温度的应用研究提供判定依据,也将为科学认识古陶瓷胎体重烧热膨胀曲线上多个转折点的形成机理提供数据支持。     

Preparation and properties of TiC-Ni cermets using Ni-plated TiC

TiC powders were coated with Ni by a chemical plating technique and the pressed compacts sintered at 1623K. The density of the sintered bodies was 98–99%. Compared with mechanically-mixed powder, Ni-plated TiC powders gave a more uniform microstructure in which TiC particles were well dispersed in the Ni matrix. The cermets exhibited ductile fracture for TiC-70 vol.% Ni and brittle fracture for TiC-30 vol.% Ni. The flexural strength was improved by the homogeneous dispersion of TiC. The thermal expansion coefficient increased with a decrease in Ni content, following a nearly linear law of mixtures on the basis of volume fractions of pure TiC and Ni.     

TiB2 coating formed on nickel substrates by electroplating in molten salt of fluoride

The TiB2 coatings deposited over nickel substrate by electroplating was investigated, which is in molten salt of a fluoride mixture involving KF, NaF, K2 TiF6 and KBF4. Effects of temperature, cathodic current density (Jc) and duration on the coating's formation were examined. The composition, morphology and structure of the coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDS) and X-ray diffraction (XRD). The results show that the coatings, with black, smooth and uniform appearance, are composed of predominating TiB2 and small amounts of nickel titanium oxide (Ni0.75 Ti0.125 O). The coatings show a nodular morphology and the grain size is dependent on the Jc and ranges about 1 - 10 μm. There is a linear relationship between the coating's thickness and the time of electrolysis within certain duration range. The reduction of the potassium can take place simultaneously with the electrochemical synthesis of TiB2 as the Jc is in excess of certain level. The hardness of the TiB2 coatings is likely to be deteriorated due to the presence of potassium and Ni0.75Ti0.125 O in the coatings.     

Fabrication and properties of low oxygen grade Al2O3 dispersion strengthened copper alloy

The low oxygen grade Al2O3 dispersion strengthened copper alloy without hydrogen-fired expansion was fabricated by the technique of vacuum hot press and hot extrusion. The mechanical and electrical properties measurements and microstructures observation on as-hot extruded, as-cold drawn and as-annealed Cu-Al2O3 alloy were conducted. The results show that the addition of a suitable amount of boron in the alloy can lower the residual free oxygen content and then inhibit the hydrogen-fired expansion. The density, σb, σ0.2, hardness, δ and electrical conductivity of the alloy reach 8.86 g/cm^3 (relative density of 99.6%), 340MPa, 250MPa, HB95,24% and 93%(IACS) respectively after hot extruded with the extrusion ratio of 30:1. Its properties have no change after annealed at 900℃ for 1h. Its strength increases after cold drawing, while its ductility and electrical conductivity drop gradually. Various properties of the cold drawn alloy can recover to those of as-extruded after annealed at 900℃ for 1h without the occurrence of recrystallization.     

氯化物熔盐中Nd^3＋在液体Ga电极上还原的电化学行为

本文利用循环V-A法(CV)研究了Nd~(3+)在液体Ga电极上还原的电化学反应动力学。结果表明,Nd~(3+)在Ga电极上的还原是分步进行的。第一步在较高的电位扫描速度下为扩散控制的可逆电荷传递反应,即Nd~(3+)+e?Nd~(2+);在电位扫描速度较低时,随后的化学反应为第一步反应的控制步骤,即Nd~(3+)+e?快Nd~(2+)+mCl→慢NdCl_m~(2-m)。第二步为不可逆的电荷传递反应,即沉积的金属Nd与Ga合金化,Nd~(2+)+2e→Nd(Ga)。估算了该反应的标准反应速度常数为7.0×10~(-3)cm/s。     

Thermal expansion anomaly and spontaneous magnetostriction of Dy2AlFe14Mn2 compound

The structure and magnetic properties of Dy₂AlFe₁₄Mn₂ compound were investigated by X-ray diffractometry and magnetization measurements. Dy₂AlFe₁₄Mn₂ compound has a hexagonal Th₂Ni₁₇-type structure. Zero thermal expansion and negative thermal expansion were found in Dy₂AlFe₁₄Mn₂ compound in the temperature range from 184 to 264 K, and from 264 to 383 K, respectively, by X-ray dilatometry. The spontaneous magnetostrictive deformations from 104 to 400 K were calculated. The results show that the spontaneous volume magnetostrictive deformation increases firstly with increasing temperature, and then decreases with further increasing temperature.     

因瓦合金异质材料焊接工艺的研究

研究了因瓦合金异质材料焊接工艺,通过试验选择了理想的异质焊接材料EZNiFe-1,并且对其焊缝进行了力学性能试验,并制定了合理的焊接方案,最终成功地保证了焊缝的低膨胀特性.