NdF3-LiF-Nd2O3系熔盐密度的研究

用阿基米德法研究了ＮｄＦ３－ＬｉＦ体系熔盐的密度。采用二因子二次回归正交设计，得出密度（ρ）与ＮｄＦ３含量（ｃ）、温度（ｔ）的回归方程，讨论了ＮｄＦ３含量及温度对熔体密度的影响，并考察了加入Ｎｄ２Ｏ３对体系密度的影响。     

Montecarlo calculations of ionic structure in silicate and alumino-silicate melts

Results on structures of molten silicates and alumino-silicates calculated with the Montecarlo method are reported. The structure of the ions is in agreement with Masson’s hypotheses; in fact ions of the type Si_nO _(3n+1 ⁽²ⁿ⁺²⁾ with chains even 30 + 35 atoms long have been found. The spatial configurations of the polymer ions are dependent on the vacancy-silicon interaction energy and therefore on the nature of the cation. The linear chain configuration is more frequent as the interaction energy becomes stronger.     

Electrodeposition of chromium from ionic melts

Information on the chemistry and electrochemistry of chromium in ionic melts is analyzed. Data on chemical reactions with chromium compounds, the electroreduction of chromium, and its electrodeposition (in the form of cathodic deposits) are discussed.     

氟化钕中杂质氧、氮的测定方法研究

研究了NdF3中杂质氧、氮的测定方法。针对NdF3高温易挥发、分解的特点和F2可能产生的腐蚀性，选择适宜的加热温度、使用镍助熔剂和适宜的浴料，选用标准坩埚进行试验，并在加热炉出口安装卤素陷阱，获得了满意的分析测定效果。对含氧0．57％，含氮0．022％的试样，分析精密度为氧5．9％，氮6．7％，加标回收率氧为95％～100％，氮为90％～1050%。该方法也可用于其他稀土氟化物分析。     

Computerized Simulation of the Structure of Molten DyF_3-LiF System

The structure of molten DyF_3-LiF system has been simulated by Monte Carlo method.Theradial distribution functions(RDFs)and the local structure have been obtained.It is concluded that F~- ionsdistribute closely around Dy~(3+) ions.There exist some fissures and holes between F~- ions and Li~+ ions.There are mainly two kinds of ionic types:the complex ions like DyF_n~(3-n) clusters with the central Dy~(3+) ions(the main ionic clusters are octahedral complex ions like DyF_6~(3-))and the“free”Li~+ ions.Moreover,somecomplex ions like DyF_n~(3-n) clusters are connected to one another by flourine-bridge,forming more compli-cated ionic clusters like Dy_m~(3m-n) F_n.By calculating the potential energies of all types of ions,it is concludedthat Li~+ ions have the highest potential energy in the molten system,which are current-carrying ions in theelectrolytic conductance.     

Wettability and interfacial behaviour of NdF3-LiF-Nd2O3 on TiB2-based ceramics

Wettability of TiB2-based ceramics by NdF3-LiF-Nd2O3 melt was studied using sessile drop technique in this paper. Wetting ex-periment was carried out under inert atmosphere at 1050 ℃. Chemical reactions which occurred on the solid-liquid interface and solid-gas interface during wetting process were discussed by thermodynamic calculations combined with X-ray diffraction (XRD) patterns. Micromorphoiogy and element distribution of fracture surface at the interfacial region of solid/liquid system were analyzed by scanning elec-tron microscope (SEM) equipped with energy dispersive spectrometry (EDS). Contact angles of the drop were determined as a function of time in order to describe the wetting process, and wetting phenomenon was interpreted fi'om a viewpoint of interface structure. The results showed that wetting was a dynamic wetting process with characteristics of reactive wetting. Penetration and oxidization phenomena during the experiment had great effect on wetting process.     

NdF3-LiF-Nd2O3体系粘度的研究

采用坩埚扭摆法研究了 Nd F3- L i F熔盐体系的粘度 ,讨论了 Nd F3含量及温度对体系粘度的影响 ,并考察了加入 Nd2 O3对体系粘度的影响。合理地解释了个别组分熔盐粘度出现异常的现象     

NdF3-LiF-Nd2O3体系表面张力的研究

用拉筒法研究了 Nd F3- L i F体系的表面张力。采用二因子二次回归正交设计 ,得出表面张力 (σ)与Nd F3含量 (C)、温度 (t)的回归方程 ,讨论了 Nd F3含量、温度对表面张力的影响 ,并考察了加入 Nd2 O3 对体系表面张力的影响     

Nd2O3-NdF3-LiF熔盐体系中电导率及钕溶解度的测定

研究了Nd2O3-NdF3-LiF熔盐体系中电导率及钕的溶解度，并根据实验数据拟合了回归方程，分析TN度、LiF浓度、Nd2O3浓度对两种物理性质的影响。结果表明，升高温度，提高LiF浓度以及降低Nd2O3浓度可以提高熔盐体系的电导率；而降低温度，降低LiF浓度以及提高Nd2O3浓度可以减少钕在熔盐中的溶解度。所得研究结果可为电解氟盐法生产钕选择合理的电解质成分提供依据。     

PrF3-NdF3-DyF3-LiF electrolyte system for preparation of Pr-Nd-Dy alloy by electrolysis

The application of Pr-Nd-Dy alloy in the field of high-performance Nd-Fe-B permanent magnet materials has great potential. The composition of the PrF₃-NdF₃-DyF₃-LiF (PND-LiF) electrolyte system used in the production of Pr-Nd-Dy alloys, the distribution of F, Li, RE and other elements in the electrolyte and their occurrence state were studied in this paper. The effect of temperature and lithium fluoride addition on electrolyte conductivity was revealed using the continuous conductivity cell constant (CVCC) method. The thermal analysis method was used to study the influence of lithium fluoride addition on the electrolyte's liquidus temperature and the optimal process conditions for the production of Pr-Nd-Dy alloy were determined. The results show that the overall distribution of praseodymium neodymium fluoride and lithium fluoride is uniform in the electrolyte and dysprosium fluoride is distributed between praseodymium-neodymium fluoride and lithium fluoride. Praseodymium-neodymium oxide is embedded in praseodymium neodymium fluoride in spotty pattern. The electrolyte's conductivity is increased as the temperature and lithium fluoride addition are going up, while the liquidus temperature is going down with increasing lithium fluoride addition. The best electrolysis process conditions for the PND-LiF system to produce praseodymium neodymium dysprosium alloy are as follows: temperature 1050 °C and 15.56 wt% PrF₃-62.22 wt% NdF₃-11.11 wt% DyF₃-11.11 wt% LiF.     

Metallothermic synthesis of boride-containing powder of chromium and molybdenum in ionic melts

Synthesis conditions of boride-containing chromium and molybdenum powders with the joint reduction of metal oxides and boron compounds in NaCl and NaF-NaCl melts at T = 1123–1173 K are considered. The content of boride phases in the composition of Cr-CrB and Mo-MoB composites is shown to reach 40–60%. The specific surface of chromium and molybdenum powders is 23.38 × 10⁵ and 18.43 × 10⁵ m^?1, respectively.     

Electrical conductivity of REF_3-LiF(RE=La and Nd) molten salts

The electrical conductivity of REF3-LiF(RE=La and Nd) molten salts(xREF_3=5 mol%-40 mol%) was systematically measured over the temperature range from 1223 to 1423 K by using continuously varying cell constant(CVCC) method.Electrical conductivity values of LaF3-LiF and NdF_3-LiF molten salts within the studied ranges are 4.11-9.39 and 3.62-9.51 S/cm,respectively.The composition and temperature dependences of electrical conductivity and the factor of RE_2 O_3 on electrical conductivity were investigated.The electrical conductivity nonlinearly decreases with the increasing mole percent of REF_3 for the changing of structural ion in molten salts.A good linear relationship between the natural logarithm of electrical conductivity(lnκ) and the reciprocal of the absolute temperature(T~(-1)) can be interpreted by the trend that electrical conductivity linearly increases with increasing temperature.Although it is an important factor of RE_2 O_3 on electrical conductivity,the influence of RE_2 O_3 on conductivity is small for the very limited solubility of RE_2 O_3 in REF_3-LiF molten salts.The results of this work supplement the present electrical conductivity data of rare earth fluoride electrolyte.     

Interfacial phenomena in the reactions of AI and Al-Ti melts with KF-AIF3 and NaF-AIF3 melts

The interfacial phenomena occurring during the contacting of Al and Al-Ti melts with KF-AlF₃ liquid fluxes have been investigated by optical examination of quenched metal drops previously immersed in the liquid fluxes. A range of temperatures between 690 °C and 840 °C was em-ployed. Reactions in the Al-Ti/KF-AlF₃ system involve the formation of TiAl₃ at the metal/ flux interface. This TiAl₃ is wetted by the KF-AlF₃ melt, and at 690 °C the TiAl₃ is dispersed in the KF-AlF₃. At 720 °C and above, a metal/flux emulsion is found in which there are high levels of K₂TiF₆ in the flux as a result of the dispersion of the TiAl₃ surface layer in the flux. At low K₂TiF₆ levels, the TiAl₃ is dispersed in the metal. Addition of Mg or Ca to the system in the form of MgF₂ or CaF₂ has been found to inhibit the formation of TiAl₃, thus also inhibiting the metal/flux emulsification. A certain critical level of Mg or Ca is required to prevent emul-sification. The results obtained for the Al-Ti/NaF-AlF₃ system were in all cases similar to those found for the Al-Ti/KF-AlF₃ system. M.S. LEE, formerly Graduate Student, Department of Materials, Imperial College, London.     

Prediction of surface tension in metallic and ionic melts in thermophysical database system

A so-called excess surface tension model in a thermophysical database of IDMSKM system is described in this paper. The functional expression for excess Gibbs energy of mixing with mole fraction for binary solutions by Redlich & Kister has been applied to correlate excess surface tension defined in this paper with mole fraction for the same, therefore, the surface tension could be represented in a quaternary polynomial function of mole fraction. The predicted surface tension values by this model demonstrate a reasonable accuracy in binary metallic as well as ionic systems. The model exhibits a better generality than the previous ones for surface tension evaluations, hence its application could be expected to expand.     

X-ray diffraction study of the structure of Al-Ni melts

The structures of Al-Ni melts with 0, 10, 18, 25, 28, 32, 40, 75, 90, and 100 at % Ni are studied by X-ray diffraction. The structural models of the melts, which were analyzed by the Voronoi-Delaunay transformation method, are reconstructed by a procedure that is inverse to the Monte Carlo method using experimental structure-factor curves. The parameters characterizing atomic ordering at short and longer distances are determined to change nonmonotonically in the range 10–40 at % Ni with an extreme in the vicinity of the melt containing 28 at % Ni. In this concentration range, nickel atoms are predominantly located in the pentagonal rings of polytetrahedral clusters of the icosahedral type; these atoms are ～4.1 Å from each other. Such clusters generate a prepeak in the structure-factor curves of the melts in the range 10–40 at % Ni.     

Solubility and thermodynamic properties of Y2O3 in LiF-YF3 melts

A systematic investigation was undertaken to measure the solubility of Y₂O₃ in several LiF-YF₂ melts, with the YF₃ composition ranging from 20 to 50 mole pct, in the temperature range of 998 to 1273 K. Experimental results showed that the solubility of Y₂O₄ in the melts increased with increase in temperature and also with increased YF₃ content. The activity of Y₂O₃ was calculated using the free energy of fusion of Y₂O₃, . The was deduced from the values of enthalpy, heat of fusion, and melting point of Y₂O₃. From the known values of activity, the activity coefficients of Y₂O₃ as a function of temperature and melt composition were calculated. Considering the ionic nature of the melt, activity coefficients were also calculated using Temkin’s ideal mixing and electrically equivalent fraction methods. The thermodynamic data, such as integral molar enthalpy, entropy, and free energy of formation, were calculated as a function of composition and temperature. The calculated thermodynamic data showed that the melt exhibited a negative deviation from ideal conditions.