应用双波长分光光度法测定锌合金中的铝

本文研究了在ph≈3.3的酸度下,以二甲酚橙显色,应用双波长法测定锌基合金中0.5％～25％的铝,大量锌可应用双波长直接消除干扰.本法操作简单、准确,适合大批量试样的分析。     

变系数线性常微分方程组的解法研究

变系数线性微分方程组,除一阶以外,没有求解的一般方法。文(1)利用一种特殊变换研究一类方程组的解,仅对二阶和三阶情形得到若干可积类型。本文利用另一种特殊变换,对三阶和四阶情形进行研究,得到较为实用的结果,而且解法简便。     

外源性雄激素连续三年生理诱导雄麝二次泌香的研究

本文报道了应用外源性雄激素连续三年生理诱导雄麝二次泌香实验过程中,雄麝诱导泌香期的生理特征及诱导产香量的变化规律,探讨了雄激素生理诱导技术对雄麝自然泌香量的影响。实验结果表明:应用外源性雄激素连续三年诱导雄麝均可使其产生诱导香,提高麝香年产量,雄麝诱导泌香期的行为及体征和自然泌香期一样:雄麝连续三年诱导产香量呈逐年下降趋势。实验中还发现:雄激素连续三年诱导雄麝产香实验不影响雄麝自然产香量。     

家养麝死亡规律探讨

本文总结了林麝死亡规律,分析了林麝死亡的原因。结果表明林麝的死亡率和其年龄、性别及季节有着密切的关系,导致林麝死亡的主要原因是化脓病的感染。     

断口—倾斜面的扫描电镜观察

本文提出了采用断口—倾斜面金相试样在扫描电镜中直接观察断口形态、裂纹扩展以及显微组织之间相互关系的实验方法;介绍了这种断口—倾斜面金相试样的制作过程,以及运用这一实验技术研究钢中细小析出相与微裂纹作用的典型实例。     

Density functional theory simulation of heterogeneous polymerization reactions during biomass hydrothermal carbonization

Carbonaceous microspheres formed through heterogeneous polymerization reactions during hydrothermal carbonization of biomass showed a considerable effect on the mass yield and physicochemical properties of hydrochar. In exploring the growth mechanism of carbonaceous microspheres, the heterogeneous polymerization reaction of four typical organic components (5-hydroxymethylfurfural, furfural, phenol, and p-xylene) with the surficial functional groups of carbonaceous microspheres was investigated using density functional theory (DFT). Nucleophilic addition and dehydration are the main forms of polymerization reactions, and the former shows a lower reaction energy barrier than the latter by 100 kJ/mol, indicating that the nucleophilic addition reactions likely occur compared to dehydration reactions. And phenol likely promotes the growth of microspheres. In addition, the surficial furan ring structure of carbonaceous microspheres opened through ring opening, hydrogen atom transfer, and molecular space structure conversion in sequence. Among these reaction steps, the furan ring opening through hydration was the rate-limiting reaction step, which showed the highest energy barrier with a value of 394.51 kJ/mol. However, the ring opening of furan rings could form more active sites, such as carbonyl groups, for subsequent polymerization reactions, indicating an increased potential for further reactions with aqueous-phase organic components.     

Evaluation of fracture behavior of lightweight magnesia-based refractories via wedge splitting test along with acoustic emission detection

The effect of spinel powder on the fracture behavior and mechanical properties of lightweight magnesia-based refractories containing microporous magnesia aggregates with high apparent porosity (37.4%) were investigated by the wedge splitting test (WST) with the digital image correlation and acoustic emission. With the addition of spinel powder, lightweight magnesia spinel refractories showed a higher cold compressive strength compared with lightweight pure magnesia refractories. From the WST, the addition of spinel powder increased the specific fracture energy and characteristic length of lightweight magnesia spinel refractories, which improved the crack propagation resistance. The increased tortuosity of main crack and a higher ratio of crack propagation along the aggregates/matrix interface were main reasons for reducing the brittleness of lightweight magnesia spinel refractories. Besides, acoustic emission (AE) signal activity indicated that the propagation of pregenerated micro-cracks by the thermal mismatch and the development of fracture progress zone were primary ways to consume energy in lightweight magnesia spinel refractories. The reduced proportion of crack propagation within aggregates was also detected by the peak frequency of AE signals in lightweight magnesia spinel refractories. For microporous magnesia aggregates with high apparent porosity (37.4%), lightweight magnesia spinel refractories also showed reduced brittleness fracture behavior than lightweight pure magnesia refractories.     

Effect of Ga3+ ion doping on emission thermal stability and efficiency of MgAl2O4:Cr3+ phosphor

In this work, we fabricated a novel spinel-type phosphor material MgAl_2−xGa_xO₄ doped with Cr³⁺ by the high-temperature solid-state sintering method. The crystal field environment of the spinel was tuned by replacing the Al ions with Ga³⁺ ions of different concentrations. The cell volume and D_q/B gradient increase from 2.82 to 2.62 with increasing Ga³⁺ ion doping concentration. This also implies a gradual decrease in the field strength of the crystal. Based on this, the excitation spectra of MgAl_1.995−xGa_xO₄:0.5%Cr³⁺ phosphors yield a redshift. Increasing the Ga³⁺ ion doping concentration also improves the emission intensity and thermal stability of the phosphors, and the emission intensity of the Ga³⁺-doped phosphors is significantly increased. For a Ga/Al ratio of 1, the thermal stability of the phosphor emission is optimal. The emission intensity at 140°C can maintain 76% of the emission intensity at room temperature, indicating that appropriate Ga³⁺ ion doping can improve the emission efficiency and thermal stability of the phosphors.     

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.