高砷锑烟尘中砷、锑分离研究进展

以不同价态砷、锑氧化物挥发性和水相热力学性质区别为切入点,综述了高砷锑烟尘中砷、锑物相的分离方法。分析了焙烧法和浸出沉淀法分离砷、锑的机理、过程和效果,并对各方法的优缺点进行了讨论。     

真空条件下含砷锑复杂铜镍合金中元素As,Sb的蒸发规律的研究

根据真空冶金原理,以分离含砷锑复杂铜镍合金中的元素砷和锑为目的,采用真空蒸馏法研究含砷锑复杂铜镍合金在真空(10~30 Pa)的条件下蒸馏过程中As,Sb的蒸发规律,考察蒸馏温度、恒温时间、多元合金中其他组元对As,Sb蒸发的影响。实验结果表明:随着蒸馏温度及恒温时间的延长,As,Sb的蒸发量和挥发率均增大。X射线衍射分析表明:当蒸馏温度低于1473 K时,残留物中的As与Cu形成的化合物Cu3As及Cu5As2,阻碍了As的彻底挥发;当蒸馏温度高于1473 K时,残留物中的As与Cu形成的化合物Cu3As及Cu5As2发生分解,使得As元素挥发得更为彻底;蒸馏温度从1573升至1673 K的过程Sb与Cu,Ni形成的化合物部分分解,Sb的挥发率明显增大。     

高砷粗铅真空蒸馏脱除砷的研究

采用鼓风炉熔炼高砷粗铅为原料,对其真空蒸馏脱除砷进行理论分析和实验研究,考察蒸馏温度、恒温时间对砷脱除率、金属铅直收率的影响。理论分析结果表明:砷与铅的饱和蒸气压差异较大,且两者不形成金属间化合物,在较低的蒸馏温度条件下,高砷粗铅真空蒸馏可以有效地脱除砷。实验结果表明:在系统压力为5~15 Pa,蒸馏温度为973 K,蒸馏时间为30 min的条件下,砷的脱除率为80%,铅的直收率为97%,粗铅中铜的存在对砷的脱除有较大的影响。此工艺为粗铅真空蒸馏脱除砷提供新的方法,对粗铅采用真空蒸馏精炼除砷具有一定的指导意义和应用价值。     

锡砷化合物真空热分解的从头算分子动力学模拟

为研究锡砷化合物真空下热分解的机理,对Sn_4As_3和SnAs化合物进行真空条件下热分解的热力学计算,得到它们30 Pa的条件下开始发生反应的温度。采用基于密度泛函理论的平面波赝势法计算得到Sn_4As_3和SnAs的稳定结构,在此基础上用从头算分子动力学的方法模拟了它们在1463 K,30 Pa和1373 K,30 Pa条件下的热分解过程,并计算了Sn_4As_3和SnAs(100)面的热分解。过程计算结果表明,在模拟条件下超胞内砷的脱除可能分步进行,并且更倾向于以As_2的形式分解。表面的Sn-As键比晶胞内部更加容易分离。     

真空蒸馏法处理铜砷锑合金综合回收铜银的研究

从理论上分析了采用真空蒸馏法处理铜砷锑合金综合回收其中有价金属铜银的可行性,并通过实验探讨了蒸馏温度、保温时间、真空度、元素As,Sb对Cu与Ag分离和富集效果的影响。结果表明:在蒸馏温度1673 K,保温时间150 min,系统残压20~30 Pa条件下,残余物中Cu含量可达82.8%,直收率为92%左右,残余物中Ag含量可降至100×10-6,表明Cu,Ag基本完全分离,挥发物中Ag含量可达0.88%,直收率为93%左右,Cu,Ag分离和富集效果显著。As,Sb因为与Cu的相互作用力很强,容易形成多种不易挥发的化合物,导致其实际挥发性和理论计算结果相差很大。产出的含Ag 0.9%左右的挥发物可以继续采用真空蒸馏法富集Ag,然后把富集Ag得到的残余物投入粗铅精炼环节,和粗铅中原有的Ag一同按传统工艺产出。含Cu80%左右的残余物可以采用改进后的硝酸-硝酸铜电解液电解精炼产出阴极铜。     

用氯化焙烧法脱除炼铜炉渣中的铜

对炼铜炉渣进行氯化焙烧可脱除渣中的铜,有利于在后续工艺回收渣中的铁。以热力学计算分析为基础,研究了在炼铜炉渣氯化焙烧过程中铜和铁的行为特征。结果表明:在一定范围内提高焙烧温度、延长焙烧时间及增加CaCl_2、FeSO_4的加入量,都有利于提高渣脱铜效率;FeSO_4的加入量大于0.15时分解产物中生成过量的SO_2,导致系统中FeO的含量激增。FeO较易被氯气氯化造成渣中铁损失严重,且使铜脱除效果降低。在焙烧温度为1373K、焙烧时间为30min、氧气流量为0.40L·min-1、CaCl_2添加量为0.20(CaCl_2与炼铜炉渣质量比)和FeSO_4加入量0.15(FeSO_4与炼铜炉渣质量比)的工艺条件下,处理后炼铜炉渣的含铜率由1.06%降至0.11%,表明用氯化焙烧法可有效脱除渣中的铜。     

Ga_(2)O_(3)真空碳热还原实验研究北大核心CSCD

本文研究了Ga_(2)O_(3)真空碳热还原过程中还原温度、C:Ga_(2)O_(3)、保温时间对实验结果的影响。研究结果表明:在还原温度1323 K、C:Ga_(2)O_(3)(摩尔比)为4、保温时间150 min的最佳实验条件下,冷凝物以均匀颗粒状富集在冷凝盖上,Ga_(2)O_(3)还原率为68.19%,还原产物冷凝收得率为59.37%,冷凝物物相为金属镓和少量歧化反应生成的Ga_(2)O_(3),金属镓在冷凝过程得到充分富集,且与Ga_(2)O_(3)良好分离。     

利用熔融分步还原法优化铜渣贫化效果及渣型结构

根据铜渣中物相成分及熔池熔炼过程工艺特点,对高温条件下熔融铜渣还原过程热力学以及实验过程进行了研究。传统的铜渣一步还原金属回收法,产物中往往得到大量金属合金,降低了熔渣中金属回收率,为避免还原程度控制不当生成金属合金,本实验采用分步还原法分别对铜渣中的有价金属铜、铁进行回收,分析了熔池温度、助熔剂CaO和还原剂炭粉添加量对渣还原贫化过程中贫化效果的影响,掌握了还原过程中渣结构的类型转变。结果表明,温度1350℃,沉降时间40min,熔渣中CaO控制量为22%(质量分数,下同),还原剂炭粉添加量为2.29%时,渣中Cu_2O的还原率达到95.36%,而还原剂炭粉量控制为8%时,渣中铁相沉降率和金属化率分别达到83.13%和85.30%。此时,由于贫化条件的适当控制,避免了铜铁金属混合物的还原析出,实现了渣中铜铁相的深度贫化,促进了铜熔渣贫化效果。此外,铜渣还原贫化过程中,由于助熔剂CaO和还原剂炭粉的添加,熔渣中铁氧化物被控制进行逐步还原,促使渣型由结构复杂的SiO_2-Fe_3O_4-FeO高粘度渣系逐步转变为结构简单、低粘度、低熔点的CaO-Al_2O_3-SiO_2三元渣系,体系渣型得到了有效优化,为后续铜渣的资源化利用提供了性能稳定的渣型。     

液相色谱-原子荧光光谱法测定饲料中的无机砷及其他砷形态

建立了饲料中4种砷形态的(即As(Ⅲ)、As(Ⅴ)、MMA、DMA)的液相色谱-原子荧光光谱(LC-AFS)测定方法。利用1%的三氯乙酸提取饲料中的砷化合物,经过液相色谱分离,原子荧光光谱仪测定。该方法前处理条件温和,能防止砷化合物在提取过程中转化而造成的假阳性。饲料中的4种砷形态的加标回收率为90.2%～105.1%,相对标准偏差(RSD)≤5.8%。方法定量限As(Ⅲ):0.007 mg/kg,As(Ⅴ)0.023 mg/kg,MMA:0.010 mg/kg,DMA:0.010 mg/kg。本方法选择性好,能够有效的消除基体干扰。可作为饲料中无机砷检测的确证方法。     

真空蒸馏-分级冷凝法处理铜浮渣的应用研究

铜浮渣是粗铅火法精炼除铜过程的产物,针对铜浮渣现有工艺流程长,环境污染,工作环境差等缺点,本文采用"真空蒸馏-分级冷凝"的方法,对铜浮渣进行脱硫和脱铅以及回收铜银锑的应用研究,对金属及硫化物的饱和蒸气压进行了理论分析,考察了蒸馏温度,恒温时间对铅和硫的脱除率和铜银锑的直收率的影响。实验结果表明:在蒸馏温度1523 K、炉内压强20~160 Pa、保温4.5 h的条件下,一级冷凝物为含硫10%的硫化物,二级冷凝物为含铜1.17%的粗铅,残留物为含铅0.46%,含硫0.21%的铜银锑合金。     

The heat capacities of U3As4 and Th3As4

The heat capacities of the arsenides of uranium (U₃As₄) and thorium (Th₃As₄) have been measured in the temperature range 5–300 K. A sharp -shaped anomaly at 195.8 K, associated with the ferromagnetic transition, was observed in U₃As₄. The smooth specific heat curve C _p(T) for nonmagnetic analog Th₃As₄ has been used to determine the lattice contribution to the heat capacity of U₃As₄. The resulting magnetic entropy at 290 K has been estimated as 10.67 J/K mole of U atom, which is close to the theoretical R ln 4 value. This fact is interpreted in terms of crystal field interactions in the crystal lattice with S₄ point symmetry. Critical entropy and enegy parameters are compared with the theoretical predictions for 3d Ising and Heisenberg models. The critical coefficients are also considered.     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

Aging martensite above As temperature

Abstract

Maraging steel is normally aged at 480 to 510°C whereas its A_s is below 560°C. In the present study, the specimens were aged at 510°C and 570°C for durations of180 and 10 min, respectively. The hardness, tensile strength, notch tensile strength, and phases formed were determined. The kinetics of the aging process were studied and the activation energies determined. The distribution of precipitates formed was studied using TEM. The results show that a short exposure at 570°C can impart properties comparable to those of the traditionally aged material.     

Removal of As(V) and As(III) by reclaimed iron-oxide coated sands

This paper aims at the feasibility of arsenate and arsenite removal by reclaimed iron-oxide coated sands (IOCS). Batch experiments were performed to examine the adsorption isotherm and removal performance of arsenic systems by using the IOCS. The results show that the pH(zpc) of IOCS was about 7.0 +/- 0.4, favoring the adsorption of As(V) of anion form onto the IOCS surface. As the adsorbent dosage and initial arsenic concentration were fixed, both the As(V) and As(III) removals decrease with increasing initial solution pH. Under the same initial solution pH and adsorbent dosage, the removal efficiencies of total arsenic (As(V) and As(III)) were in the order as follows: As(V)>As(V)+As(III)>As(III). Moreover, adsorption isotherms of As(V) and As(III) fit the Langmuir model satisfactorily for the four different initial pH conditions as well as for the studied range of initial arsenic concentrations. It is concluded that the reclaimed IOCS can be considered as a feasible and economical adsorbent for arsenic removal.     

Alloying (In,Mn)As and (Ga,Mn)As: Ferromagnetic (In,Ga,Mn)As Lattice-Matched to InP

An effect of alloying two ferromagnetic semiconductors (In,Mn)As and (Ga,Mn)As on the ferromagnetic properties of resultant (In,Ga,Mn)As alloys is reported. For conditions close to lattice-matching to InP substrates, y = 0.53 in (In _y Ga_1–y )_1–x Mn _x As, ferromagnetism up to Curie temperatures T _C = 100–110 K could be achieved for a Mn composition x = 0.13. Trends in the Curie temperature in (In,Ga,Mn)As are compared with (Ga,Mn)As and (In,Mn)As as a function of Mn content. Hole concentrations determined from magnetotransport, taking into account the anomalous Hall contribution to Hall resistance, gives p/Mn = 0.03 ratio to Mn composition in metallic case for x = 0.13. We mention the possible role of chemical ordering (short range) of Mn impurity atoms on hole concentration and, consequently, for the ferromagnetic properties.