具有良好可再生性的新型二氧化硅磁性氧化石墨烯纳米复合材料

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles (NPs) were prepared by coating the Fe₃O₄ NPs with a SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO₂ on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composite where Fe₃O₄@SiO₂ NPs are firmly encapsulated by GO nanosheets. The optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.     

微波预处理对复杂铜矿磨矿及浮选动力学的影响

The effect of CaCO₃, Na₂CO₃, and CaF₂ on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe₃PO₇ and apatite was investigated. The results revealed that Na₂CO₃ had the most significant effect on iron recovery and dephosphorization, followed by CaCO₃, the effect of CaF₂ was negligible. The mechanisms of CaCO₃, Na₂CO₃, and CaF₂ were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe₃PO₇ was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO₃ reacted with Fe₃PO₇ to generate an enormous amount of Ca₃(PO₄)₂ and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na₂CO₃, the phosphorus in Fe₃PO₇ migrated to nepheline and Na₂CO₃ improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF₂ reacted with Fe₃PO₇ to form fine Ca₃(PO₄)₂ particles scattered around the iron particles, making the separation of iron and phosphorus difficult.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

一种超重力燃烧合成制备高性能高熵合金的新方法

A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr_0.9FeNi_2.5V_0.2Al_0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients.     

利用皮秒激光烧蚀制备非球形铝纳米颗粒

We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl₃) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed.     

窄板坯结晶器内连铸工艺参数对钢液流场的影响

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.     

电渣重熔脱硫技术研究进展

Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed.     

Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al₂O₃?Na₂O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na₄Ca₃(AlO₂)₁₀ was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na₄Ca₃(AlO₂)₁₀, CaO·Al₂O₃, and 12CaO·7Al₂O₃, and the content of Na₄Ca₃(AlO₂)₁₀ could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na₄Ca₃(AlO₂)₁₀ occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na₄Ca₃(AlO₂)₁₀ was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na₄Ca₃(AlO₂)₁₀ was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.     

含细夹层的分矿充填层中流动特性的可视化

Ore particles, especially fine interlayers, commonly segregate in heap stacking, leading to undesirable flow paths and changeable flow velocity fields of packed beds. Computed tomography (CT), COMSOL Multiphysics, and MATLAB were utilized to quantify pore structures and visualize flow behavior inside packed beds with segregated fine interlayers. The formation of fine interlayers was accompanied with the segregation of particles in packed beds. Fine particles reached the upper position of the packed beds during stacking. CT revealed that the average porosity of fine interlayers (24.21%) was significantly lower than that of the heap packed by coarse ores (37.42%), which directly affected the formation of flow paths. Specifically, the potential flow paths in the internal regions of fine interlayers were undeveloped. Fluid flowed and bypassed the fine interlayers and along the sides of the packed beds. Flow velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity (1.8 × 10?5 m/s) suddenly increased. Fluid stagnant regions with a flow velocity lower than 0.2 × 10?5 m/s appeared in flow paths with a large diameter.     

齿轮的成型磨削

本文介绍一种提高齿轮精度的加工方法—成型磨削法。本方法是采用成型砂轮磨削齿型,比双碟型砂轮磨削生产效率要高。同时所需设备比蜗杆磨齿简单。因此,是一种很有价值的、先进的齿轮磨削方法。     

无单元法在箱形基础中的应用研究

无单元法采用滑动最小二乘法来构造形函数 ,将无单元法用于弹性地基箱形基础的挠度及内力的计算中 ,推导了无单元法刚度矩阵公式 ,编制了相应的程序 ,并给出了算例 .计算结果表明 ,用无单元法解决箱基础问题是合理可行的     

产品质量的定量综合评估方法

提出产品质量定量化综合评估的一种方法———模糊综合评判法 .文中介绍了这种方法的有关概念与基本原理 ;为了应用方便 ,特别提出了确定评价向量的一种简单方法 ,提出了确定权系数的UFD法 ,提出了在模糊子集中定义序关系的二次加权法 .这些方法可直接用于实际工作中     

等波纹线性相位FIR滤波器的1种设计方法

介绍了一种用Remez函数设计等波纹线性相位FIR滤波器的设计方法,并利用MATLAB强大的功能进行仿真。仿真结果表明,设计结果的各项性能指标均达到较高的要求,并且证明该方法是一种优化的设计方法。在同样的技术指标下,用这种方法设计得到的滤波器要比窗函数法和频率采样法得到的滤波器的长度均要小,而且设计过程简单易行。     

钛催化渗氮工艺提高工（模）具钢性能的研究

研究了钛催化渗氮的新工艺方法,对多种材料进行了渗氮处理。实验结果表明,这种方法与传统的气体氮化法或盐浴氮化法相比,具有化合物层厚度增加,表面硬度高,渗氮速度快,生产效率高的优点。是一种提高工具钢和模具钢性能的有效方法。     

人参皂苷超声水提取法的改进

以人参总皂苷、 人参皂苷-Rb₁,-Rb₂,-Rb₃,-Rc,-Rd,-Re,-Rf,-Rg₁和-Rg₂等9种主要单体皂苷的收率为指标, 利用超声波提取器提取,大孔吸附树脂法去除杂质, 高效液相色谱法测定含量, 比较稀醋酸提取法和常规超声水提取法的优劣. 结果表明, 稀醋酸提取法所得总皂苷和各 单体皂苷收率均比常规超声水提法明显提高, t检验证明两种提取方法有显著的差异（P<0.001）.稀醋酸提取法对常规超声水提法进行改进, 此法 收率高、 纯度大、 操作简便, 适合工业化生产.     

市政道路工程质量综合评价的可拓方法

介绍了可拓评价方法的基本原理,探讨了该方法在市政道路工程质量综合评价中的应用,并根据实际情况采用可拓方法选取权重,与文献中已有的权重进行比较,实例分析结果表明不同权重下的评价结果基本一致,可拓评价方法是合理可行的．     

基于超松弛迭代的MHSS加速方法

修正的Hermite/反Hermite分裂(MHSS)迭代方法是一类求解大型稀疏复对称线性代数方程组的无条件收敛的迭代算法。基于超松弛(SOR)迭代技术,本文提出一类MHSS加速方法,分析了MHSS加速方法的收敛性质,给出了MHSS加速方法中参数ω的选取办法。数值实验证明了新方法能够有效地提高MHSS求解线性代数方程组的求解效率。     

改进的重力加载比例法在非均质边坡稳定性分析中的应用

为了解决强度折减法在非均质黄土边坡稳定性计算中的局限性,采用改进的重力加载比例法研究了山西某非均质黄土边坡的稳定性。首先,运用三轴试验抗剪参数,采用Mohr-Coulomb屈服准则,不相关流动法则,应用有限元分析软件建立数值分析模型,分析了计算得到的水平位移与实测的水平位移,验证了改进的重力加载比例法在该边坡中的适用性。然后,将其计算精度和时效与强度折减法的对比,结果表明:对于该非均质边坡,改进的重力加载比例法计算的安全系数与传统的有限元计算方法得到的安全系数的误差为3%,强度折减法计算结果的误差为7.6%;并且改进的重力加载比例法简化了计算过程,减少了计算过程中人工的干预,使得计算速度更快。     

一个求解非线性最小二乘问题的新方法

在Gauss-Newton(G-N)方法和Levenbery-Marquardt(L-M)方法(阻尼最小二乘法)的基础上给出了一种新的求解非线性最小二乘问题的方法，它是通过寻求新的非线性方程组的数值方法来实现的，首先给出了不用计算导数的求解非线性方程组的收敛迭代方法，该方法是建立在求解动力系统的稳定点的基础上，采用了较稳定的常微分方程初值问题的数值方法进行迭代求解，并采用Steffensen加速技术以提高收敛速度，最后，给出了用Matlab试算的数值例子、试验结果表明了该方法的有效性。