NdF3—NaF—LiF熔体电导率的研究

采用三因子一次正交回归设计实验，研究了NdF3-NaF－LiF熔体的电导率，得出了该体系电导率的数学模型，分析了温度、NdF3浓度、NaF与LiF的摩尔比对电导率的影响。结果表明，提高温度、降低NdF3浓度、降低NaF与LiF的摩尔比均能提高电导率。所得研究结果可为稀土氟盐电解选择廉价电解质成分提供依据。     

New functionally gradient materials in the Ti−Si−C system

A new ceramic functionally gradient material (FGM) with controlled hardness and fracture toughness is presented. Very hard SiC and soft, fracture resistant Ti₃SiC₂ ceramics were manufactured as one multilayered composite. This composite was prepared by hot-pressing from SHS-derived powders. Microstructure and indentation tests proved the FGM structure. Mining and Metallurgy University, Krakow, Poland. Published in Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 42–45, March–April, 1999.     

金属铝在KF - LiF - Na3AlF6- Al2O3体系中的溶解度

用等温饱和法研究了金属铝在KF - LiF - Na3 AF6 - Al2O3体系中的溶解过程,实验结果表明:体系温度980℃,分子比(n( NaF)/n(AlF3))=2.3时,溶解度随着钾盐和锂盐含量的增加而增大;钾盐和锂盐质量分数分别为7％时,铝的溶解度(质量分数)分别达到0.148％和0.242％,并且锂盐比钾...     

Alloy compositions and phase diagram for the Sc−Ru−Rh system. IV. Solidus surface of the Sc−ScRu−ScRh partial system

A projection has been constructed for the solidus surface of the partial, Sc−ScRu−ScRh system on the concentration triangle from data obtained by microstructure analysis, x-ray diffraction, microprobe analysis, differential thermal analysis, and the measurement of temperatures for the start of melting by the Pirani-Alterthum method. It is found that ternary compounds are not formed in this system. The solidus surface has regions representing solid solutions based on β-scandium and phases based on the binary compounds Sc₅Ru₃, Sc₂Ru, Sc₁₁Ru₄, Sc₂Rh, and Sc₃Rh, as well as ones for the δ and η phases (continous solid solution series formed between isostructural phases of CsCl type based on ScRu and ScRh as well as Sc₅₇Rh₁₃ based on Sc₅₇Ru₁₃ and Sc₅₇Rh₁₃). Other components of the solidus surface are twelve lineated surfaces, which bound two-phase volumes, and five isothermal surfaces, which correspond to nonvaiant four-phase equilibria involving the liquid, which occur at temperatures of 1150, 1055, 1045 (two equilibria), and 1000°C. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 55–63, July–August, 1999.     

Na3AlF6-K3AlF6-AlF3熔体的电导率研究

通过连续改变电导池常数法(CVCC),用自制的电导率测试装置研究KCl溶液与熔融KCl的电导率。实验证明连续改变电导池常数法能满足于一般的科学实验要求,自制的电导率测试装置能满足常温实验和高温实验的电导率测试要求。通过此装置测定了钾冰晶石在(Na3AlF6+K3AlF6)熔体中的含量为40%,AlF3在(Na3AlF6+K3AlF6+AlF3)混合熔体中的含量分别为0、20%、24%和30%的电导率,实验还讨论了AlF3含量对电导率的影响。     

Density of Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3 molten salt melt for Al–Sm alloy

Samarium (Sm) has been widely used in making aluminum (Al)–Sm magnet alloy materials. The research team for this study developed a molten salt electrolyte system which directly produces Al–Sm alloy to replace the energy intensive conventional distillation technology. In this study, molten melt density was measured and operation conditions were optimized to separate Al–Sm alloy product from the fluoride molten melt electrolysis media based on density differences. Archimedes' principle was applied to measure density for the basic molten fluoride system (BMFS: Na₃AlF₆–AlF₃–LiF–MgF₂) electrolysis media in the temperature range from 905 to 1055 °C. The impact of temperature (t) and the Al₂O₃ and Sm₂O₃ addition ratio (w_(Al2O3), w_(Sm2O3)) in the basic fluoride system on molten melt density was examined. The fluoride molten melt density relationship was determined to be: ρ = 3.11701 ? 0.00802w_(Al2O3) + 0.027825w_(Sm2O3) ? 0.00117t. The test results showed that molten density decreases with increase in temperature and Al₂O₃ addition ratio, and increases with the addition of Sm₂O₃, and/or Al₂O₃ + Sm₂O_3. The separation of Al–Sm (density 2.3 g/cm³) product melt from the BMFS melt is achieved by controlling the BMFS density to less than 2.0 g/cm³. It is concluded that the optimal operation conditions to control the BMFS molten salt density to less than 2.0 g/cm³ are: maintain addition of Al₂O₃ + Sm₂O₃ (w_(Al2O3) + w_(Sm2O3)) < 9% of Na₃AlF₆, Al₂O₃/Sm₂O₃ ratio (w_(Al2O3):w_(Sm2O3)) > 7:3, and temperature between 965 and 995 °C.     

K3AlF6-Na3AlF6-AlF3铝电解体系密度的研究

采用流体静力称重法研究了K<,3>AlF<,6>-Na<,3>AlF<,6>-AlF<,3>铝电解质体系的密度.探讨了K<,3>AlF<,6>,AlF<,3>含量和温度与K<,3>AlF<,6>-Na<,3>AlF<,6>-AlF<,3>体系密度的关系.实验结果表明:K<,3>AlF<,6>-Na<,3>AlF<,6>-AlF<,3>体系密度与温度成较好的线性关系,温度升高,密度降低;随着AlF<,3>含量的降低,体系的密度对温度的变化更加敏感.相同过热度下,固定KR(钾冰晶石含量),随着AlF3含量的增加,体系的密度呈现出不同的变化规律,相同过热度条件下,对于较低的KR=0.1值,随着AlF<,3>含量的增加,体系的密度逐渐下降,对于较高的KR=0.5值,随着AlF<,3>含量的增加,体系密度先降低后增加,存在最低点.相同过热度下,固定AlF<,3>含量,随着KR增加,体系密度也呈现出不同的变化规律,当AlF<,3>为22%,随着KR增大,体系密度变化不大;当AlF<,3>为26%,30%,随着KR增大,体系密度先降低后增加.     

Composites with a functional gradient in the systems Si3N4−Al2O3−Y2O3−TiC

Composites with a functional gradient in the system Si₃N₄−Al₂O₃−Y₂O₃−TiC were made by laminating and sintering ceramic films obtained by tape casting. The films had high contents of TiC and Al₂O₃ and were of different thicknesses. Materials with a high density and high fracture toughness (K_1c≈9.3 MPa·m^1/2) were obtained. Warsaw Polytechnic Institute. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 1–7, July–August, 1999.     

Na3AlF6-K3AlF6-AlF3电解质体系铝溶解度的研究

采用质量差法研究了不通电时Na3AlF6-K3AlF6-AlF3体系中铝的溶解度。实验首先测定了不同时间内铝溶解的情况,并确定铝饱和溶解的时间为3 h。主要研究了初晶温度、过热度、电解质组成,以及电解质融化之后的熔盐深度对铝溶解度的影响。实验选用刚玉坩埚盛装电解质。测试结果表明,初晶温度为670～900℃的电解质,铝的溶解度为0.05%～0.50%(质量分数)。在初晶温度较低的电解质中,铝的溶解度较低,反之较高。对于某个特定体系来说,提高过热度会增加铝的溶解度。电解质的组成对铝溶解度的影响是:增大KR,可以降低铝的溶解度;AlF3含量增加,铝溶解度降低;对于KR=30,AlF3=26%(质量分数)的电解质,出现了异常的情况。另外,减少电解质的用量,降低熔盐的深度,也会造成铝的挥发损失,并最终导致铝的溶解增加。总之,影响铝溶解度的因素是多方面的,抑制铝的溶解损失,可以从改变电解质的组成、降低初晶温度、减少铝的挥发等方面着手。     

Texture evolution in the presence of precipitates in Fe−3% Si alloy

Texture evolution by grain growth in the presence of MnS or MnS and AIN precipitates in Fe−3% Si alloy was investigated by X-ray diffraction (vector method) and ECP (selected area electron channelling pattern). Texture evolved by grain growth varied with the intensity of the inhibitors in the following manner: when an inhibitor intensity is higher than a critical value, the orientation N having the highest I_CΣi value in the matrix becomes major orientation after grain growth. Here the I_CΣi value denotes an intensity of orientations with Σi type coincidence orientation relationship with a given orientation N (except Σ1 and Σ3 type coincidence orientations). When an inhibitor intensity is weaker than the critical value, the orientation (N) having the highest P_CNΣi value in the matrix becomes major orientation after grain growth. Here the P_CNΣi value denotes an product of a intensity of the given orientation (I_N) and the I_CΣi value. With an weaker inhibitor level, I_N being more dominant and with a stronger inhititor level, I_CΣi being more dominant under the same P_CNΣi value. The inhibitor effect of P_CNΣi1 value increases with increasing in the inhibitor intensity, where P_CNΣ1 is a product of the intensity of the given orientation (I_N)     

熔盐Na3AlF6-K3AlF6-AlF3系中氧化铝的饱和溶解度

采用旋转氧化铝片法研究了Na3AlF6-K3AlF6-AlF3体系的氧化铝溶解度,其中电解质组成为:K3AlF6占K3AlF6和Na3AlF6质量总和的0～50%,AlF3占23%～29%,对该范围的氧化铝溶解度提出了相关系数为0.994的经验计算公式和等氧化铝浓度图。研究结果表明:随着AlF3含量增加,氧化铝溶解度降低,AlF3含量小于25%的区域氧化铝溶解度较高;随着钾冰晶石的增加,均出现相同的趋势,氧化铝溶解度先增加后减少,在K/(K+Na)含量为10%～40%时相对较高些;为了确保氧化铝溶解度大于4%,熔体温度必须高于840℃,故该复合冰晶石体系比较有潜力实现的低温电解温度是850℃。     

Molecular Dynamics Calculation of the Self-Diffusion Coefficients in Molten LiF–RbBr and LiF–CsBr Mixtures

Classical molecular dynamics simulation is used to calculate the self-diffusion coefficients of the ions that make up reciprocal molten LiF–RbBr and LiF–CsBr mixtures at a temperature of 1420 K over the entire concentration range. The microscopic motion of the fluoride ion is shown to change qualitatively as a function of the nature of the cation forming the nearest environment. For example, the nearest environment of the fluoride ion in a reciprocal LiF–RbBr mixture at a low rubidium bromide concentration favors an increase in its self-diffusion coefficient despite the fact that the system density increases in this case.     

Oxidation of alloys of the system Ni−Ta. I. Oxidation of the intermetallic Ni3Ta

Oxidation kinetics for the intermetallic Ni₃Ta in air at 600–1000°C are studied by a thermogravimetric method. The alloy has an ordered crystal structure (D¹³ _2h-Pmmn) with rhombic lattice parameters a=0.512 nm, b=0.423 nm, and c=0.452 nm. The kinetic isotherms of Ni₃Ta oxidation are described by a parabolic equation. With t≤800°C there is a periodic increase in the rate constant of parabolic oxidation, but with t>800°C there is a periodic decrease of it. In the range 850–875°C the alloy oxidation rate decreases as a result of scale sintering. Oxygen diffusion slows down in the compact scale. X-ray and metallographic analysis of the scale that forms on Ni₃Ta indicates that it contains NiO, NiO·Ta₂O₅, Ta₂O₅ and also Ni and the solid solution Ni(Ta). These phase components are distributed in layers of the scale: NiO (first), NiO+NiO·Ta₂O₅ (second), NiO·Ta₂O₅+Ni+Ta₂O₅ (third), Ta₂O₅+Ni(Ta) (fourth). With a low temperature and short periods of heating there is no Nio·Ta₂O₅ or Ni(Ta) in the scale. Oxidation of Ni₃Ta is controlled by oxygen diffusion in the scale over the direction towards the alloy. With t>850°C this mechanism changes. By analogy with oxidation of tantalum it is assumed that structural changes in the Ta₂O₅ lattice may be responsible for this. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 80–87, March–April, 1999.     

Electro-reductive stripping of cerium in the TBPHNO3 two-phase system

The stripping of cerium (IV) from loaded organic solvent (30% TBP-70% dichloromethane) by valency change with two-phase electrolysis was studied experimentally. The results show that the average current efficiency and the electrical energy consumption are in the range of 50–70% and 1.0–2.0 kW/kg cerium, respectively. The effects of various parameters on cerium stripping were also studied. The selected parameters were agitation speed, rate of nitrogen bubbling, organic and aqueous acidities, surfactant addition and density ratio. The density ratio (defined as density of the organic phase to that of the aqueous phase) is a dominant factor for the process studied.     

Thermodynamics of the Na2O−P2O5 system

The activity of Na₂O in the melts of the Na₂O?P₂O₅ system has been determined using a high temperature electrochemical cell with a Na₂O?WO₃ melt at the reference electrode and fused silica as the solid electrolyte as shown below. $$_{Na_2 O - WO_3 melt}^{Pt(s),O_2 (g)} \left| {_{fused silica}^{ Na^ + } } \right|_{Na_2 O - P_2 O_5 melt}^{O_2 (g), Pt(s)} $$ The thermodynamics of the Na₂O?P₂O₅ binary system in the composition range of 50 to 75 mole pet Na₂O has been studied. The activities of Na₂O and P₂O₅ in the melt have been carefully analyzed. The free energy of four sodium phosphates has been evaluated with the help of the phase diagram of this system. Based on this study, a solid-state phase transformation for the 3Na₂O·P₂O₅ compound has been suggested at a temperature below 1217 K. The entropy of the transformation is near zero. The enthalpy of transformation is estimated to be 101.51 kJ/mole 3Na₂O·P₂O₅.     

Effect of Heat Treatment in the Temperature Range 400−1300°C on the Properties of Nanocrystalline ZrO2−Y2O3−CeO2 Powders

Powder Metallurgy and Metal Ceramics - The properties of nanocrystalline powders of compositions (mol.%) 97 ZrO2–Y2O3, 95 ZrO2–3 Y2O3–2 CeO2, 92.5 ZrO2–2.5 Y2O3–5...     

K3AlF6-Na3AlF6-AlF3体系组成对α-Al2O3溶解度和溶解速度的影响

采用EDTA络合滴定法研究了粉末状α-Al2O3在K3AlF6-Na3AlF6-AlF3体系中的溶解度和溶解速度.探讨了K3AlF6、AlF3含量和温度对氧化铝在K3AlF6-Na3AlF6-AlF3体系中溶解度和溶解速度的影响,并测定了K3AlF6-Na3AlF6-AlF3体系初晶温度30℃以上溶解度和溶解速度,比较了含钾冰晶石熔盐体系和传统钠冰晶石基熔盐体系Al2O3溶解度方面的差异.实验结果表明:K3AlF6-Na3AlF6-AlF3体系中的α-Al2O3溶解速度很快,在5～10 min内溶解已经达到饱和;850℃时,KR每增加0.2,Al2O3溶解度增加约0.5%(质量分数);随着K3AlF6含量的增加Al2O3溶解度相应的增加,相对于高钾冰晶石含量体系而言,较低K3AlF6含量时,增加K3 AlF6的量对提高氧化铝溶解度幅度更加显著;与传统钠冰晶石电解质体系相比K3AlF6-Na3AlF6-AlF3体系Al2O3的溶解度明显增大,当KR≥0.3时,差异愈加显著.     

Solid-liquid surface energy in the AlMg system

The solid-liquid surface energy and the grain boundary energy have been measured by a direct method in the AlMg system. It was found that the average solid-liquid surface energy was 0.149 J/m² and the average grain-boundary energy was 0.295 J/m². The results are compared with those obtained previously in the AlSi and AlCu systems (solid-liquid 0.169, 0.163 J/m² and grain-boundary 0.336, 0.325 J/m² respectively). The thermal conductivities of both the solid and the liquid were also measured and were found to be 0.12, 0.046 and 0.045 W/K mm respectively for solid Al-17 wt% Mg, solid Al-35 wt% Mg and liquid Al-35 wt% Mg.