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.     

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.     

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.     

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.     

奇异非线性四阶边值问题的正解

证明存在两个正数0<λ^*<λ_*<+∞, 使得奇异非 线性四阶边值问题y⁽⁴⁾(x)=λh(x)f(y(x)),0*)时, 无正解; 当λ∈(λ^*,+∞)时, 存在1个正解; 当λ∈(λ_*,+ ∞)时, 存在3个解, 其中有2个为正解, 只要f(y)在y=0处是超线性, 并在y=+∞处是次线 性的.     

关于函数域中相交多项式的一个注记

以Z表示有理整数环。设L为一个特征为p的域, f(x)=∑ⁿ_j=0a_jx^j∈L［x］,L［x］表示L上的多项式环。假定在L的某个代数闭包上, f(x)=a∏^r_i=1(x-η_i)^e_i。此处,a∈L,一切η_i是两两不同的,r,e₁,e₂,…,e_r是正整数,且r≥2, n=∑^r_j=1e_j。f的半判别式Δ(f)被定义为Δ(f)=a^2n-1∏_{1≤i,j≤ri≠j}(η_i-η_j)^{e_i e_j}。证明了下面的结果: 如果n1,e₂,…,e_r)有关的正整数m与G∈Z［x₀,x₁,…,x_n］,使得Δ(f)=1/mG(a₀,a₁,…,a_n)且m|n!。此外,当L为有限域时,还应用此结果研究了与环L［x］上相交多项式有关的一个问题。     

2m阶Schrödinger方程组在实指数Sobolev 空间中的整体小解

Schrödinger型方程是一类非常重要的发展方程.通过应用Banach不动点定理,该文研究了在任意维数空间中2m阶非线性Schrödinger方程组{iu_t+(-Δ)^mu=a|u|^α-1u|v|^β+1,x∈Rⁿ,t≥0,iv_t+(-Δ)^mv=b|u|^α+1|v|^β-1v,x∈Rⁿ,t≥0,u(x,0)=φ(x),v(x,0)=ψ(x),x∈Rⁿ在实指数Sobolev空间H^s_p1(Rⁿ)×H^s_p2(Rⁿ)中的整体小解.     

一类混合型数论函数的均值估计

设λ_f(n)是标准化的Hecke算子T_n的尖形式的傅立叶系数, σ(n)是除数和函数, φ(n)是欧拉函数。 利用解析的方法研究混合数论函数λ_f(n)σ^b(n)φ^c(n)的平均阶估计, 得到了上界估计∑_n≤xλ_f(n)σ^b(n)φ^c(n)≪x^b+c+1/2+ε,这里ε>0是任意的。     

非齐次核逆向Hilbert型积分不等式的最佳搭配参数及算子表达式

利用权函数方法, 在1/p+1/q=1(0λ1y^λ2)(λ₁λ₂>0)的逆向Hilbert型积分不等式, 给出其最佳搭配参数的充分必要条件, 并讨论其算子表达式.     

Banach空间中p阶Bessel列的扰动

应用算子论方法研究Banach空间X中p(1i}_i∈I, 定义了有界线性算子Tf: X^*→l^p, 建立了从全体p阶Bessel列组成的Banach空间B^p_X(I)到算子空间B(X^*,l^p)上的等距线性同构α: f→T_f, 并给出了p阶Bessel列的扰动定理.     

一个二元二次同余方程解的计数

设n是任意正整数,令Z_n是模n的剩余类环,并且Z^*_n是模n的即约剩余类环,即Z^*_n={s:1≤s≤n, gcd(s,n)=1}。通过利用同余理论与指数和的相关结果来研究集合T(a,b,c,n)={(x,y)∈(Z^*_n)²:ax²+by²+c≡0 mod n}的元素个数并给出集合T(a,b,c,n)元素个数的确切计算公式。     

亚纯函数微分多项式IM分担值的唯一性

研究了亚纯函数的微分多项式分担一个值的唯一性问题,证明了如果f(z)和g(z)为非常数亚纯函数,其零点和极点的重数至少为s,s为正整数,且满足(n+1)s≥24,n为正整数且n≥2。如果f ⁿf '和gⁿg'分担1 IM,则g(z)=c₁e^cz,f(z)=c₂e^-cz,其中c₁、c₂、c为常数,且满足(c₁c₂)ⁿ⁺¹c²=-1,或者f(z)=tg(z),其中tⁿ⁺¹=1。     

两类非线性微分—差分方程的整函数解

利用Nevanlinna值分布理论,研究了两类非线性微分-差分方程fⁿ+ωf^n-1f′+b(f′)ⁿ+qe^Qf(z+c)=ue^v和fⁿ+ω₁f^n-1f′+ω₂(f′)ⁿ+qe^Qf(z+c)=p₁e^λ₁z+p₂e^λ₂z的有限级整函数解的存在性,得到了两个结果,并举例证明文中所得结果是精确的。     

分数阶周期边值问题的上下解方法

应用上下解方法,研究分数阶周期边值问题x(δ)(t)=f(t,x(t)),t∈[a,a+T],a0,x(a)=x(a+T)解的存在性,其中:f是连续函数,f(a+T,x)=f(a,x),a0,T0是常数;δ∈(0,1].