Fe-Al金属间化合物的第一性原理研究综述

Fe-Al金属间化合物具有密度低、比强度高、抗高温氧化和耐腐蚀性良好等优点,且成本低廉,成为镍基高温合金潜在的替代结构材料。综述了利用第一性原理计算研究元素掺杂/微合金化对Fe-Al金属间化合物及涂层的室温脆性、高温强度、界面结合、抗高温氧化及耐腐蚀性能影响的研究进展,设计了第一性原理研究B2型Fe-Al合金耐氯化盐腐蚀机理的理论计算方案,展望了第一性原理计算应用于Fe-Al合金及涂层材料研究的发展方向。

含酚类煤化工废水自还原Fe^(3+)类芬顿体系研究

煤化工废水水质复杂,难降解有机物及氨氮含量高,给废水处理带来较大难度。现有的煤化工废水处理技术(混凝法、吸附法、膜生物反应法等)具有成本高、运行不稳定、预处理效果差等缺陷,难以满足煤化工行业发展的需要。为了高效处理煤化工废水,本文利用煤化工废水中酚类有机物的还原性促进Fe^(3+)/Fe^(2+)的循环,提出了一种利用Fe^(3+)/H_(2)O_(2)类芬顿体系处理煤化工废水的方法。实验结果表明:Fe^(3+)/H_(2)O_(2)体系中COD、TOC、TN、NH3-N的去除率可以达到74.63%、52.62%、10.46%、15.11%;相比于其他体系,Fe^(3+)/H_(2)O_(2)体系出水色度明显降低,UV-Vis光谱下降幅度最大,铁泥量也明显减少。Q-TOF分析结果表明:废水中主要的8种有机物为酚类或具有醛基、羰基、羧基、碳碳双键或者酯基等还原性的官能团。通过测定COD去除率和pH、Fe^(3+)/Fe^(2+)、H_(2)O_(2)等含量随时间的变化趋势,提出了Fe^(3+)/H_(2)O_(2)体系去除有机物的机理:废水中的还原性有机物将Fe^(3+)还原为Fe^(2+),促进Fe^(3+)/Fe^(2+)循环,生成的Fe^(2+)与H_(2)O_(2)发生芬顿反应,实现废水中有机污染物的去除。利用控制变量法,确定了最佳运行工况为:Fe_(2)(SO_(4))_(3)添加量为1.0 g/L、H_(2)O_(2)添加量为50 mmol/L、反应温度为30℃、初始pH为6.8。在此工况下,反应60 min后,煤化工废水的COD、TOC、TN、NH_(3)-N去除效果良好,色度明显降低,BOD_(5)和COD的比值(B/C)从0.17提升至0.47,可生化性大幅提高。本文证实了利用含酚类煤化工废水自还原Fe^(3+)/H_(2)O_(2)体系的可行性,降低了运行成本,可为后续研究及工程应用提供理论基础。

Fe^(Ⅳ)化合物的定性鉴定及稳定性分析

由高铁酸盐 (FeⅥ)的碱性溶液得到一亮绿色溶液 ,该溶液在一定条件下极为稳定 .经过氧化性试验、酸化试验、红外光谱和紫外可见光谱对照试验及排除性试验 ,确认该亮绿色溶液为FeⅣ 化合物 .实验证明 ,FeⅢ 对FeⅣ 绿色碱性溶液无催化作用 ,但对FeⅥ 有强催化作用 ,这是相同条件下FeⅣ

酸性Fe(Ⅲ)溶液催化氧化S(Ⅳ)的研究

利用酸性铁离子溶液在鼓泡反应器中进行了模拟烟道气SO2脱出实验研究.在总铁离子浓度为1 72×10-2～4 12×10-1mol·L-1、总S(Ⅳ)浓度为3 32×10-5～7 81×10-5mol·L-1、O2含量1%～10%(干重)、pH为0 8～2 2、温度为25～32℃的范围内,研究了水合Fe(Ⅲ)离子与氧化物之间的配合物反应.实验证明,在合适的操作条件下存在一个最佳脱硫效果的总铁离子浓度(0 13mol·L-1),在Fe(Ⅲ)离子浓度较低的情况下(小于0 13mol·L-1),反应液中的配合物主要是二聚羟合铁离子,其与亚硫酸配合物的形成与分解从而产生亚硫酸自由基是反应速度的控制步骤.当Fe(Ⅲ)离子浓度超过0 13mol·L-1后,由于多聚羟合铁离子、硫酸铁配合物等多核配位体的形成,使其在与亚硫酸根形成配合物时受到大基团的空间阻碍效应,使反应率下降.通过实验结果和理论分析,提出了脱硫反应为配位催化氧化自由基反应机理.

Fe(Ⅱ)-Ce(Ⅳ)双中间体库仑滴定的电极伏安行为及Cr(Ⅵ)测定

采用循环伏安法研究了Fe(Ⅱ)-Ce(Ⅳ)双中间体恒电流库仑滴定体系及工作电极的电化学行为,优化了电解液组成,探讨了S2-和Cl-等的干扰机理。在优化的分析条件下,方法用于测定工业废水中μg级的Cr(Ⅵ),与分光光度法对照,相对误差小于3%,回收率在93.9%～98.9%之间。该法简便、快速、灵敏、准确,且不受试样颜色、浊度及沉淀的影响,无需配制标准溶液,可连续测定。

薄层树脂相预浓集与光度法联用同时测定痕量Fe(Ⅲ)和Mo(Ⅳ)的研究

在酸性条件下,Fe（Ⅲ）和Mo（Ⅳ）可与邻苯二酚生成有色配阴离子Fe（Ⅲ）-邻苯二酚体系和Mo（Ⅳ）-邻苯二酚体系,该二配阴离子易与Cl-型717#阴离子交换树脂中的Cl-进行等离子对交换缔合,形成三元等离子对缔合体系R＋（阴离子交换树脂）-Fe（Ⅲ）-邻苯二酚体系和R＋-Mo（Ⅳ）-邻苯二酚体系.两种三元缔合体系的最大吸收波长分别为520和402nm,与水相中最大吸收波长相同,对比度△λ=118nm,互不干扰,故而建立了薄层树脂相光度法同时测定Fe（Ⅲ）和Mo（Ⅳ）的新方法.方法灵敏度高,εFe520（Ⅲ）=4.8×10^4L·mol^-1·cm^-1,比水相光度法提高16倍,εMo402（Ⅳ）=1.0×10^5L·mol^-1·cm^-1,比水相光度法提高24倍;精密度理想;选择性强.实测了合成水样和天然水样中Fe（Ⅲ）和Mo（Ⅳ）,加标回收率分别为97%～99%和97%～101%,检出限分别为35和28ng/mL,线性范围分别为0～12和0～9.6μg/mL.与AAS法测定值相比较,结果令人满意.

Fe（Ⅱ）对Cr（Ⅳ）─I~－体系诱导反应机理的研究

本文考查了下Ｆｅ（Ⅲ）－Ｉ－、Ｃｒ（Ⅳ）－Ｉ－及Ｃｒ（Ⅳ）－Ｉ－Ｆｅ（Ⅱ）体系的反应曲线，证明由于Ｆｅ（Ⅱ）的引入，体系产生Ｃｒ（Ｖ）中间体并快速氧化Ｉ－；通过实验确定Ｃｒ（Ⅳ）－Ｉ－－Ｆｅ（Ⅱ）体系的化学计量关系，导出了诱导反应的机理及速率方程，并通过反应曲线的研究进一步证实了反应机理。

过硫酸盐氧化Fe(Ⅱ)生成Fe(Ⅳ)降解二甲基异莰醇和土臭素的效能和机理

二甲基异莰醇(2-MIB)和土臭素(GSM)是水体中常见的嗅味物质。采用Fe^(2+)活化过硫酸盐(PDS)体系降解2-MIB和GSM,并研究反应过程中的降解路径和机理。试验结果表明,Fe^(2+)/PDS体系在pH值为3.0、PDS浓度为1.0 mmol/L、Fe^(2+)的浓度为1.0 mmol/L的条件下,可以使2-MIB降解率达到99.10%,GSM的降解率达到83.08%。以四亚甲基亚砜(TMSO)作为指示物,探究了Fe^(2+)活化PDS体系降解2-MIB和GSM的反应活性物质是高价铁[Fe(Ⅳ)]。应用该体系在处理深圳某水库水时,2-MIB和GSM的降解率分别为99.01%和80.03%,处理效果良好,为该体系在实际应用提供理论基础。

西地碘片联合FE复合酶漱口液对ROU患者EGF、E-selectin水平的影响

目的通过观察复发性口腔溃疡(ROU)患者表皮生长因子(EGF)、E-选择素(E-selectin)水平变化,评价西地碘片联合FE复合酶漱口液治疗的应用价值。方法选取我院于2019年3月至2020年12月收治的160例ROU患者,随机分为对照组和研究组,各为80例。对照组接受FE复合酶漱口液,研究组在此基础上联合西地碘片。对比两组疗效、唾液EGF、E-selectin水平变化、免疫功能,随访5个月,观察两组患者复发情况。结果研究组的临床总有效率高于对照组(P<0.05)。研究组治疗后EGF、E-selectin水平更低(P<0.05)。与对照组相比,研究组治疗后CD8^(+)更低,CD3^(+)、CD4^(+)、CD4^(+)/CD8^(+)更高(P<0.05)。研究组随访期间的复发率低于对照组(P<0.05)。结论西地碘片联合FE复合酶漱口液治疗ROU患者,可提高机体免疫功能,降低EGF、E-selectin水平,具有较好的临床应用价值。

Extended x-ray absorption fine structure study of MnFeP_(0.56)Si_(0.44) compound

The Mn Fe P0.56Si0.44 compound is investigated by x-ray diffraction, magnetic measurements, and x-ray absorption fine structure spectroscopy. It crystallizes in Fe2P-type structure with the lattice parameters a = b = 5.9823(0) and c = 3.4551(1) and undergoes a first-order phase transition at the Curie temperature of 255 K. The Fe K edge and Mn K edge x-ray absorption fine structure spectra show that Mn atoms mainly reside at 3g sites, while 3f sites are occupied by Fe atoms. The distances between the absorbing Fe atom and the first and second nearest neighbor Fe atoms in a 3f-layer shift from 2.65 and 4.01 in the ferromagnetic state to 2.61 and 3.96 in the paramagnetic phase. On the other hand, the distance between the 3g-layer and 3f-layer changes a little as 2.66 –2.73 below the Curie temperature and2.68 –2.75 above it.

Magnetic properties and magnetocaloric effects in NaZn_(13)-type La(Fe,Al)(13)-based compounds

In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.

Dechlorination of Chlorinated Aliphatic Compounds by Micro-scale Al-Zn-Mg/Fe Powders as Advanced Zero-valent Iron

Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advanced zero-valent iron are highly effective for degradation of chlorinated organic compounds. The efficiency of degradation for carbon tetrachloride and perchloroethylene is higher than 99% within a period of 2 h. The efficiency of degradation for trichloroethylene by MAF after storing for one month is equivalent to that by freshly prepared nano-size zero-valent iron particles.

Magnetostriction of Pseudobinary Compounds Pr_(0.15)Tb_xDy_(0.85-x)Fe_2(x=0 to 0.85)

The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.

Modification ofβ-Al_5FeSi Compound in Recycled Al-Si-Fe Cast Alloy by Using Sr,Mg and Cr Additions

The effects of Sr,Mg,Cr,Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated.The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-likeβ-Al-5FeSi phases （β-compound） into the fibrousα-Al-8Fe-2Si （α-compound）.The additions of Sr and Sr/Mg were less effective to modify theβ-compound into theα-compound,while the eutectic Si was fully modified into the fibrous morphology.A small secondary dendrite arm spacing （DAS） was found in the Sr-added,Cr-added and Sr/Cr-added alloys,especially in a steel mold.The Sr,Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously.A sludge phase was found in the addition of Cr-added,Sr/Cr-added and Mg-added alloys,especially in the graphite mold casting.The volume fraction ofβ-compounds was decreased by the addition of various modifying elements. The Cr and Sr/Cr combined additions are very effective to modify theβ-compound for the recycled Al-Si-Fe based alloys.

A Density Functional Study on the Geometries of Compounds Fe(HCN)_n^+ (n = 1～6)

The possible geometries of Fe(HCN)n (n = 1~6) compounds were studied by using + DFT/UB3LYP/6-31G(2df) method. The structure and ground state of each fragmental ion are C∞v (4Σ+ or Σ ), D∞h (4Σg ), D3 (4A1 ), C2 or Td or C3v (4A1), and D3 (4A1 ) or C4 ( A1 ) sequentially 6 + + ′ ′ ′ 2 ′ h v h v with n = 1～5. For the compound Fe(HCN)6 , the possible geometry was not obtained. The + sequential incremental interaction energy (–?(?E)), dissociation energy (?D0), enthalpy (–?(?H)) and Gibbs free energy (–?(?G)), and frequencies for HCN-Fe(HCN)n + -1 were also calculated, and the results are all in good agreement with the experiments. The bond length of Fe–N is lengthened with the increase of cluster size, and the strength of Fe+–N coordination bond varies nonmon- tonically as increasing the number of ligands. The Fe+–N bond of Fe(HCN)2 is the strongest in all + compounds.

Thermal expansion anomaly and spontaneous magnetostriction of Tb_2Fe_(15)Cr_2 compound

The structural and magnetic properties of Tb2Fe15CF2 compound were investigated by means of X-ray diffraction and magnetization measurements. Tb2Fe15Cr2 compound has a hexagonal Th2Ni17-type structure. Negative thermal expansion was found in Tb2Fe15Cr2 compound from 372 to 452 K by X-ray dilatometry. The coefficient of the average thermal expansion is α^- =-3.14×10^-5 K^-1. The magnetostrictive deformations from 292 to 450 K were calculated. The result showed that the spontaneous volume magnetostrictive deformation ms remains nearly constant with increasing temperature up to 360 K, but decreases with the further increase of temperature. The spontaneous linear magnetostrictive deformation λc along the c axis decreases with increasing temperature. The spontaneous linear magnetostrictive deformation, λa, in the basal-plane increases with increasing temperature up to 360 K, but decreases with further increasing temperature.

Structural and Magnetic Properties of Sm_3(Fe,Ti)_(29) and Sm_3(Fe,Ti)_(29)X_y (X=H, N) Compounds

The alloy with nominal composition Sm_2(Fe0.94Ti0.06)17 is prepared by arc-melting, hydrogenation and nitrogenation processes. The Sm_2(Fe0.94Ti0.06)17 alloy has a single phase of Sm_3(Fe, Ti)29 with the Nd_3(Fe, Ti)29-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300℃. The hydrogenation at 800℃ mainly shows a HDDR process. The HD and nitrogenation at 500℃ result in increasing the Curie temperature of the alloy by 72℃ and by 158℃ due to lattice expansions, respectively. The anisotropic and isotropic Sm_3(Fe. Ti)29N_y magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm_3(Fe, Ti)29N_y powders achieved in the above two processes are: (i) B_r=0;82 T, _iH_c=4.48 kA/cm. (BH)_max=54.3 kJ/m^3, (ii) B_r=0.68 T, _iH_c=8.14 kA/cm, (BH)max=66.4 kJ/m^3.

Cu、Mg、Ni、Ti、V掺杂Fe_(3)Al的力学和电子性能的第一性原理计算

采用基于密度泛函理论的第一性原理方法计算金属间化合物Fe_(3)Al掺杂合金元素前后的弹性常数、泊松比和态密度,分析不同合金元素对金属间化合物Fe_(3)Al力学和电学性能以及态密度的影响。结果表明:Ni和Mg可以提高Fe_(3)Al的塑性,Cu、Ti和V会增加Fe_(3)Al的脆性。韧性最高的3种化合物的共价性和结构稳定性强弱都是Fe_(12)MgAl_(3)>Fe_(11)NiAl_(4)>Fe_(11)MgAl_(4)。Mg掺杂会降低Fe-Al之间的离子键,而Ni掺杂会增强Fe-Al之间的离子键。

Negative Thermal Expansion of the Dy_2Fe_(16)Cr Compound

Structural, thermal expansion, and magnetic properties of the Dy_2Fe_(16)Cr compound are investigated by means of x-ray diffraction and magnetization measurements. The Dy_2Fe_(16)Cr compound has a hexagonal Th_2Ni_(17)-type structure. There exists a negative thermal expansion resulting from a strong spontaneous magnetostriction in the magnetic state of the Dy_2Fe_(16)Cr compound. The average thermal expansion coefficient is-0.794 × 10^(-5)/K in the temperature range 292–407 K. The spontaneous magnetostrictive deformation and the Curie temperature are discussed.

Spin and Orbital Magnetisms of NiFe Compound:Density Functional Theory Study and Monte Carlo Simulation

The self-consistent ab initio calculations based on the density functional theory approach using the full potential linear augmented plane wave method are performed to investigate both the electronic and magnetic properties of the NiFe compound. Polarized spin within the framework of the ferromagnetic state between magnetic ions is considered. Also, magnetic moments considered to lie along （001） axes are computed. The Monte Carlo simulation is used to study the magnetic properties of NiFe. The transition temperature To, hysteresis loop, coercive field and remanent magnetization of the NiFe compound are obtained using the Monte Carlo simulation.