富云母高岭石铝土矿拜耳法溶出性能研究

富云母高岭石铝土矿具有铝高、硅高和铝硅比低的特点,为有效开发利用该类型铝土矿,了解拜耳法溶出氧化铝工艺的适应性,获得适宜的溶出条件并提高溶出率,采用高压盐浴溶出试验研究溶出温度、溶出时间、循环母液苛性碱浓度、石灰添加量、矿石粒度和配料分子比对氧化铝溶出性能的影响。结果表明:该铝土矿适合采用拜耳法溶出,适宜溶出条件为:溶出温度260~280℃、溶出时间60min以上、循环母液苛性碱浓度220~240g/L、石灰添加量9%、矿石粒度0.28mm、配料分子比1.35~1.45。在此条件下,氧化铝实际溶出率达72%以上,相对溶出率达96%~98%。     

碱溶—碳分法生产氧化铝溶出效果研究

NaOH溶液溶出铝土矿是碱溶—碳分法生产氧化铝新工艺的核心技术之一。采用现有拜耳法生产设备进行预脱硅和高压溶出试验,研究用NaOH溶液溶出不同铝硅比(A/S)一水硬铝石型铝土矿的溶出效果,确定了适宜的工艺条件,并与生产现场拜耳法蒸发母液溶出的效果和生产效率进行了对比。结果表明,矿石的实际溶出率(η_实)随矿石A/S、苛性碱质量浓度(N_K)、配料分子比(α_(k配))和配料溶出率(η_配)的升高而升高,随石灰添加量的增加呈先升后降的趋势;在相同工艺条件下,现场母液与NaOH溶液溶出的效果基本保持在相同水平,但相同体积的NaOH溶液溶出矿石量是现场蒸发母液的1.71倍,循环效率则是现场蒸发母液的2.16倍;碱溶—碳分工艺预脱硅溶出的适宜条件为:矿石A/S4.0、预脱硅温度98℃、预脱硅时间6h、N_K=200g/L、石灰添加量11%、α_(k配)=1.3～1.5、η_配=90%、溶出温度273℃、溶出时间40min,此条件下A/S=8.65矿石的η_实可达87.75%。     

拜耳法高温溶出工艺实验研究

针对我国铝土矿高硅高铝,溶出困难的特点,着重研究碱法即拜耳法高温溶出铝土矿制备铝酸钠溶液的工艺过程。分别选用某铝厂母液和碱溶液浸出铝土矿,改变苛性碱浓度、温度、时间、液固比和矿石粒度,分析各因素对铝土矿中Al2O3的溶出率的影响,从而得到最佳的溶出条件。     

低铁铝精矿拜耳法浸出工艺研究

对桂西北某分选出的以一水硬铝石为主的低铁铝精矿进行浸出研究,考察了溶出温度、苛性碱浓度、石灰添加量及溶出时间对铝精矿浸出率的影响.结果表明,在浸出温度270℃,苛性碱浓度250 g/L,石灰添加量10%,浸出时间60 min的条件下,Al_2O_3的浸出率达到78.49%,相对浸出率达97.00%.浸出温度及石灰添加量有着最主要影响.     

浅析稳定溶出赤泥铝硅比的方法

如何通过一系列的办法提高氧化铝生产溶出赤泥的A/S合格率,分析了溶出温度、搅拌强度、循环母液浓度、矿石细度、溶出时间和母液添加量等因素对溶出A/S的影响,从浓度和配料方法等方面给出了调整措施。通过实践数据证明,A/S控制需要理论与实践经验的紧密结合。     

高硫铝土矿脱硫精矿拜耳法溶出氧化铝试验研究

研究了用拜耳工艺从高硫铝矿脱硫精矿中溶出铝。结果表明,拜耳工艺溶出过程中,以黄铁矿形式存在于脱硫精矿中的硫会随黄铁矿的溶解进入溶液;在溶解温度265℃、溶解时间60 min、循环母液Na_2O_k质量浓度235 g/L、分子比1.45、石灰用量为矿石质量7.5%条件下,铝土矿脱硫精矿中的氧化铝的相对溶出率为97.5%,硫溶出率为19.5%。     

贵州某高硫铝土矿中硫和铝的溶出行为

研究了贵州某高硫铝土矿中硫和铝的溶解行为,通过正交试验确定了苛性碱质量浓度、石灰添加量、温度和时间等参数的影响程度,利用回归法确定了各参数对硫和铝溶出率的影响。结果表明,在温度270℃、苛性碱质量浓度225g/L、石灰添加量5%、溶出时间60min条件下,硫溶出率为26.01%,氧化铝的相对溶出率维持在97%以上,后续脱硫成本较低。     

氧化铝生产中工业循环碱液选精矿溶出工艺研究

氧化铝生产中,针对选矿拜耳法选精矿溶出赤泥的A／S,特别是N／S居高不下的现状,用工业循环碱液在3L无机盐熔盐加热高压釜中对影响选精矿溶出效果的诸因素进行了系统研究。结果表明,选精矿拜耳法溶出的最佳工艺条件为：溶出温度260℃,溶出时间60min,配料[[C／S]]=2．0,配料αK=1．50,进料苛性碱Na2OK质量浓度200～210g／L。在此条件下,选精矿的溶出赤泥A／S降为1．55,赤泥中水化石榴石SiO2饱和系数降为1．0,赤泥的N／S存0．15以下。     

高铁三水铝石矿溶出动力学

研究了高铁三水铝石矿常压条件下的溶出动力学。分别考察了矿石粒度、氢氧化钠浓度、溶出温度、搅拌速度对溶出性能的影响。研究发现,常压条件下矿石溶出率大于90%。提高溶出温度或氢氧化钠浓度、减小矿石粒度均可加快矿石的溶出速度。综合考虑矿石粒度、氢氧化钠浓度和搅拌速度的影响,推导出高铁三水铝石矿溶出动力学经验方程为:1-2/3α-(1-α)~(2/3)=1.28×10~(15)×(c_(NaOH))~(1.70)×d~(-0.36)×r~(0.74)×e~(-117402/RT)×t。该方程与内扩散控制的动力学模型吻合较好,反应速率受包覆在晶体表面的针铁矿和赤铁矿固体膜层所控制。     

某高硫铝土矿选择性溶出氧化铝试验研究

研究从贵州某高硫铝土矿中溶出氧化铝,通过正交试验确定了氧化铝溶出的影响因素及优化条件。结果表明:各因素对Al_2O_3和S溶出率的影响顺序为溶出温度苛性碱质量浓度石灰添加量溶出时间;在溶出温度250℃、苛性碱质量浓度254.9g/L、石灰添加量8%、溶出时间60min优化条件下,氧化铝溶出率在95%以上,硫溶出率在24%以下,氧化铝的选择性溶出效果较好。     

FTSR薄板坯内部横裂纹形成机理的分析和预防措施

采用Gleeble-3500热模拟机模拟FTSR薄板坯生产工艺,试验了SS330钢板坯(0.06％C)和SS400钢板坯(0.20％C)在600～1 350℃的高温塑性。结果表明,SS400钢在700～900℃的高温塑性高于SS330钢,SS400钢板坯内部产生的横向裂纹是由于柱状晶晶界处硫、氧化物的偏聚,使钢晶界的高温塑性下降所致。通过钢中硫含量由0.015％降低至0.010％,全氧含量由45×10^-6降至30×10^-6,钢中Nn／S≥60,钢水过热度由30～50℃降至20～35℃,铸坯拉速由2.5～6.0 m／min改为3.0～4.5 m／min,控制二冷水量,有效地避免了薄板坯内部横裂纹的产生。     

Energy transfer and luminescent properties of Tb3+ and Tb3+, Yb3+ doped CNGG phosphors

In this work,calcium niobium gallium garnet(Ca₃ Nb_1.6875Ga_3.1875O₁₂-CNGG) ceramic samples singledoped with Tb³⁺ and co-doped with Tb³⁺ and Yb³⁺ ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb³⁺ ions corresponding to the maximum luminescence in the green spectral range in CNGG:...     

云南大坪金矿床围岩蚀变和同位素地球化学特征

云南大坪金矿床主要赋存于闪长岩体中。由围岩至矿脉,形成自变质闪长岩带、绿泥石化带和碳酸盐化带的蚀变围岩分带,后二带与金矿化关系密切,宽度不一,渐渐过渡。在绿泥石化带中,带出的成分有SiO₂、Al₂O₃、Na₂O、FeO、Fe₂O₃、MnO、CaO、MgO、H₂O⁺、Li、W、Ta、Zr、V、Sc、Sn、Mo、Cr、Co、Ni、Cu、Pb、Au 和LREE,带入的成分有K₂O、P₂O₅、Ba、HREE(包括Y)、Ag、Zn。碳酸盐化带过程中, 带出的成分有SiO₂、Al₂O₃、Na₂O、K₂O、Ba、HREE(包括Y)、Mo、Sn、Pb、Zn、Ag,带入的成分有FeO、Fe₂O₃、M nO、CaO、MgO、H₂O+、P₂O₅、Li、Ta、Zr、V、Sc、Cr、Co、Ni、Au 和LREE,基本不变的成分有W、Cu。矿脉中铁白云石的δ¹⁴C值为-4.81‰,接近于深成碳;(⁸⁷Sr/⁸⁶Sr)为0.709019±72,∈Nd (0)为-17.34, fSm/Nd为-0.34,起源于地壳;蚀变强烈的围岩的δ¹⁸O值高,表明蚀变热液为非大气降水;金属硫化物(黄铁矿、方铅矿、黄铜矿和闪锌矿)的δ³⁴S为-4.0‰～11.1‰,成矿热液的Σ³⁴S从早阶段到晚阶段增高。     

A comparative study of NdY-Fe-B magnet and NdCe-Fe-B magnet

Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnets. However, the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still unclear. In this work, we systematically investigated the magnetic properties, thermal stabilities and service performances of (Nd_0.8Y_0.2)_13.80Fe_balAl_0.24Cu_0.1B_6.04 (atomic fraction, denoted as 20Y) and (Nd_0.8Ce_0.2)_13.80Fe_balAl_0.24Cu_0.1B_6.04 (atomic fraction, denoted as 20Ce) magnets. The results demonstrate that the μ₀M_r, μ₀H_c and (BH)_max of 20Y magnet are respectively 1.325 T, 1.173 T and 343.467 kJ/m³, which are comprehensively higher than those of 20Ce magnet (μ₀M_r = 1.310 T, μ₀H_c = 0.948 T, (BH)_max = 321.105 kJ/m³). Moreover, the 20Y magnet has higher thermal stability compared with 20Ce magnet which is favorable for the magnetic performances at elevated temperatures. The investigation of microstructure and elemental distribution indicates that the excellent magnetic performances of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties 4πM_s, H_a and T_c of Y₂Fe₁₄B, but also to the in-situ core–shell structure of the 2:14:1 matrix phase grain with Y-rich core and Nd-rich shell, along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B magnet. Furthermore, the 20Y magnet exhibits better mechanical property and higher corrosion resistance than 20Ce magnet, which are helpful for prolonging the service life of the magnet in practical application.     

钛含量对Nb-Ti微合金化Q345A钢热轧板力学性能的影响

试验研究了钛含量对Q345A钢(%:0.08～0.10C、1.19～1.46Mn、0.017～0.029Nb、0.02～0.08Ti) 14～20mm热轧板力学性能的影响。结果表明,Ti=0.02%时,钢板的强度无显著变化,Ti为0.02%～0.04%时,钢板强度随Ti含量增加而增加;Ti≥0.04%时,钢板强度随Ti含量增加而下降。控制Nb-Ti微合金化重型汽车板用钢Q345A的Ti含量为0.02%～0.04%,可获得最佳强塑性配合。     

Effect of CaF2 and SiO2 modification on phosphorus utilisation in P-bearing slag

Abstract

In order to recycle phosphorus in P-bearing converter slag for slag phosphate fertiliser, the effect of CaF₂ and SiO₂ modification on P-bearing steelmaking slag on phosphorus-bearing phases, P₂O₅ solubility and magnetic separation behaviour has been researched. The results show that the phosphorus-rich phase is mainly n2CaO·SiO₂–3CaO·P₂O₅ (nC₂S–C₃P for short) and exists along with fluorapatite phase [Ca₅(PO₄)₃F] after the addition of CaF₂. The fluorapatite cannot be dissolved in 2% citric acid solution, which decreases the P₂O₅ solubility in slag. Although adding CaF₂ can increase the P₂O₅ content of phosphorus-rich phase, it can improve its metallisation and magnetisation of RO phase, increase the amount of recovered magnetic substances, and separate incompletely phosphorus and iron, therefore it is adverse to the phosphorus recovery from P-bearing slag by magnetic separation. P₂O₅ content of phosphorus-rich phase is more than 31% and P₂O₅ solubility of slag is increased to 96% in fluorine-free modified slag, which can meet the requirement of P₂O₅ content and P₂O₅ solubility of the phosphate fertiliser. Meanwhile, 87.1% of the phosphorus in the fluorine-free modified slag is contained in non-magnetic substance, and most of the phosphorus was recycled.     

Synthesis and optical properties of novel apatite-type NaCa3Bi(PO4)3F:Dy3+ yellow-emitting fluorophosphate phosphors for white LEDs

In this study, novel yellow-emitting fluorophosphate NaCa₃Bi(PO₄)₃F phosphors doped with different concentrations of Dy³⁺ ions were first obtained via high-temperature solid-state reaction. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties, thermal stability, and luminescence decay curves of the resulting phosphors were then characterized in detail. Under the excitation of 349 nm, the three dominant peaks of the NaCa₃Bi(PO₄)₃F:Dy³⁺ are centered at 480 nm (⁴F_9/2-⁶H_15/2), 577 nm (⁴F_9/2-⁶H_13/2), and 662 nm (⁴F_9/2-⁶H_11/2). The optimal doping concentration of Dy³⁺ ions in the NaCa₃Bi(PO₄)₃F:xDy³⁺ phosphors is x = 5 mol%. The phosphors show excellent thermal stability with high activation energy (E_a = 0.32 eV). Eventually, the synthesized white light-emitting diode (w-LED) demonstrates the Commission International de L'Eclairage (CIE) chromaticity coordinates of (0.341, 0.334), a good correlated color temperature (CCT) of 5083 K, and a high color rendering index (R_a) of 92. Revealing its potential as yellow-emitting phosphors, the feasibility of the fabricated apatite-type NaCa₃Bi(PO₄)₃F:Dy³⁺ fluorophosphate phosphors was confirmed for w-LEDs.     

Relaxor behavior and superior ferroelectricity of Y2O3-doped (Ba0.98Ca0.02) (Ti0.94Sn0.04Zr0.02)O3 lead-free ceramics

To upgrade the electric properties of lead-free piezoceramics, (1–x)(Ba_0.98Ca_0.02Ti_0.94Sn_0.04Zr_0.02)O₃-xY₂O₃ (abbreviated as (1–x)BCTSZ-xY, x = 0 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol% and 0.1 mol%) ceramics were successfully synthesized by traditional solid-state sintering method. The phase structure and microstructure of ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and piezoresponse force microscopyeramics (PFM). The electric properties of ceramics were researched through piezoelectric, dielectric and ferroelectric test instruments. The results show that all samples have pure perovskite structure and favorable electric properties. The optimal electric properties which especially include superior ferroelectric properties are gained when Y₂O₃ content is 0.06 mol% (d₃₃ = 419 pC/N, k_p = 52%, T_c = 89.5 °C, ε_r = 26900, tanδ = 2.86%, P_r = 14.41 μC/cm², E_c = 1.8 kV/cm). Moreover, the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies. The Curie–Weiss law further proves that all samples are typical relaxor ferroelectrics, and the relaxor degree of samples decreases with increase of Y₂O₃ content. In conclusion, Y₂O₃ plays a significant role in enhancing electric properties of BCTSZ ceramics.     

Significantly improved high k dielectric performance: Rare earth oxide as a passivation layer laminated with TiO2 film

In order to achieve a super gate dielectric performance,rare earth oxides featuring for large band gap,good thermodynamic stability and relatively high k value were selected to be laminated with TiO₂ film to prepare bilayer dielectric films.As an example,the microstructure,morphology,band gap structure and electrical performance of TiO₂-Y₂O₃ bilayer films were systematically investigated.Results show that stacking sequence of TiO₂ and Y_...     

New environmental-friendly yellow pigments Y_(4-x)A_xMoO_(9+δ)(A =Ta,Tb)

A series of inorganic yellow pigments with general formula Y_(4-x)A_xMoO_(9+δ)(A = Ta, Tb), where x = 0,0.05,0.1,0.2, 0.4 for Ta and χ = 0, 0.005, 0.01.0.03, 0.05 for Tb,were synthesized by a conventional ceramic method at 1400 ℃ for 6 h in air. The samples were characterized by XRD,EDS,XPS,SEM,TG-DSC,UV-vis-NIR reflectance spectroscopy and CIE L*a*b* color scales. It is found that the substitution of A(A = Ta, Tb) for Y~(3+) in Y_4 MoO_9 decreases the NIR reflectance of the pigment samples, but the developed pigments Y_(4-x)A_xMoO_(9+δ)(A = Ta, Tb) still exhibit impressive NIR solar reflectance. The brighter yellow color of inorganic pigments Y_(4-x)A_xMoO_(9+δ)(A = Ta, Tb) is available when x is about 0.1 for Ta and 0.01 for Tb. The results make them a series of potential candidates as ecological yellow pigments because of their high reflectance, lightness, intense coloration and excellent thermal and chemical stability.