不锈钢酸洗混合废酸(HNO_3-HF)的回收以及离子交换法在其纯化中的应用

采用离子交换法对不锈钢酸洗工艺产生的混合废酸(HNO3-HF)进行纯化,以去除废酸中的金属杂质和盐份,使其达到回用之目的。实践证明,对于HNO3含量在3.5%~6.5%,HF含量在0.27%~0.5%,Fe含量在55.54~84.33g/l的混合废酸,该方法可回收90%以上的HNO3和86%以上的HF,Fe去除率大于81.54%,同时酸回收可降低63.3%的处理成本,纯化后酸可回用于生产,是一种高效低耗的新工艺。     

关于不锈钢设备与零部件酸洗配方讨论

介绍了不锈钢设备与零部件各种酸洗配方,特别对HNO3＋HF、HNO3＋HCl等混酸及酸洗膏的配方作了分析讨论。     

太阳能硅制备过程湿法提纯SiO2的工艺优化

考察了HF质量分数、H2C2O4质量分数、HNO3质量分数、酸浸时间、粒径、液体质量与固体质量的比值(简称液固比,下同)等因素对混酸法提纯SiO2工艺过程的影响,利用电感耦合等离子体发射光谱仪(ICP-OES)、场发射扫描电子显微镜(SEM)进行表征。结果表明,最佳工艺条件为:w(HF)=2%、w(H2C2O4)=3%、w(HNO3)=30%、酸浸时间4 h、粒径100～120目、液固比4∶1、酸浸温度30℃。Fe、Al、Ca、P杂质的去除率分别达到99.99%、14.02%、73.27%、60.00%,经混酸法处理后SiO2中杂质总量的质量分数降至1.465×10-4。     

β-SiC粉体中常见金属杂质的亚临界水热去除工艺

高纯β-SiC粉体作为原料,广泛应用于半导体晶圆、半导体窑具、半导体芯片设备用陶瓷器件等产品。高温高压可以促进水热反应,采用亚临界水热法可去除工业合成β-SiC粉体中的金属杂质。研究不同酸体系下β-SiC粉体中常见金属杂质的去除效果。利用电感耦合等离子原子发射光谱仪(ICP-OES)检测微量元素的含量,通过X射线衍射仪(XRD)和扫描电镜(SEM)对β-SiC粉体的物相组成和微观结构进行表征。结果表明,对于Cr和Zr去除效果较好的是HCl体系,对于Ca、Fe、Mg和Ti去除效果较好的是HCl+HF+HNO₃体系,对于Al和K去除效果较好的是H₂SO₄+(NH₄)₂SO₄体系。采用HCl体系处理的最佳反应温度为200 ℃,采用HCl+HF+HNO₃体系处理的最佳反应温度是220 ℃,采用H₂SO₄+(NH₄)₂SO₄体系处理的最佳反应温度是200 ℃。其中,H₂SO₄+(NH₄)₂SO₄体系可将β-SiC粉体中常见金属杂质含量降低至最少(杂质总含量为920.31 mg/L),因此该体系为β-SiC粉体除杂的最优方案。     

表面预处理对燃烧合成β-SiC粉体水基浆料流动性的影响

以燃烧合成工艺制备的β-SiC粉体为原料,系统研究了煅烧、酸洗、碱洗3种预处理工艺对燃烧合成SiC粉体表面特性和水基浆料流动性的影响。SiC粉体中的杂质,即可溶性金属离子和粉体表面的SiO2的含量是影响粉体zeta电位和浆料流动性的关键因素。这3种预处理工艺均能有效降低SiC粉体中的杂质含量,从而改善浆料的流动性,其中碱洗处理的效果最为显著。     

超声波酸浸除铁提纯硅微粉实验研究

研究了超声波外场下酸浸去除硅徽粉中铁杂质的效果,实验考察了超声波频率、时间对硅徽粉中铁杂质质量分数的影响.结果表明:超声波的机械作用能促成酸液的乳化和徽粉的分散,空化作用产生的局部高温高压,不仅可撕裂硅微粉中含铁杂质带,使酸液进入而溶出铁杂质,并且反应徽区的高能高温加速了反应进程,强化了酸浸除铁的效果.此外,提高超声波频率和增加处理时间均能提高铁杂质的去除率.经超声波处理后,样品铁杂质质量分数最低可以降到8 μg/g,相当于不加超声波外场情况的1/3.该结果为超声波用于硅徽粉提纯提供了相关研究基础.     

混合酸纯化对隐晶质石墨固定碳含量的影响

为了提高天然隐晶质石墨的固定碳含量,采用HF-HCl混合酸一步法对隐晶质石墨进行提纯,研究了混合酸与石墨比例、氢氟酸含量、酸洗温度、酸洗次数对石墨固定碳含量的影响,确定了混合酸提纯隐晶质石墨的最佳工艺参数。当混合酸与石墨比例为2、HCl与HF体积比为1.5、恒温60℃下反应3 h、酸洗4次时,隐晶质石墨的固定碳含量从83.08%提高到99.41%。研究结果表明,混合酸一步法能显著提高隐晶质石墨的固定碳含量。     

含氟混酸检测新方法

在H2SO4与HF、HNO3与HF等含氟混酸中,加入镁离子和乙醇沉淀氟离子,从而使HF与其他酸分离,达到分别检测混酸中各酸浓度的目的。经实验证明HF酸含量检测的绝对误差在0.2%以内。     

镁合金基体上镍磷镀层的退除

提出了一种采用HF与HNO3退除镁合金上化学镀镍磷镀层的方法。测试了不同HF与HNO3组合的退镀液的性能,并分别测定了不同HF与HNO3含量对退镀效果的影响。结果表明,退镀液中含有一定含量的F^-,可保护基体不受腐蚀,其生成的保护膜主要为MgF2。当退镀液中ω(HF)：ω(HNO3)：ω(H2O)为4：3：3时,效果最好。由于HF有剧毒,因此操作过程应采取相应的防护措施。     

硅石焙烧-酸浸提纯及杂质相结构的演变

在硅石提纯过程中,采用XRD和EDS分析硅石中杂质元素赋存特征,采用高温焙烧活化与酸浸复合提纯方法研究了酸浸过程杂质相结构演变及提纯效果. 结果表明,硅石中不同类型铝硅酸盐的K, Na, Ca, Al, Si含量不同,主要分为长石类、伊利石和高岭石;酸浸提纯过程中硅石的杂质相不仅会溶解在酸中,且长石类杂质相会演变成伊利石和高岭石. 与未预酸浸的硅石提纯相比,预酸浸的硅石经高温焙烧活化提纯后纯度达99.995%,达到高纯石英砂的纯度,杂质Al和K含量分别降低了76.6%和66.5%;在700℃下焙烧,预酸浸硅石的Al和K去除效果最好,去除率分别为85%和41%.     

冶金法制备太阳能硅过程的湿法除硼研究

湿法提纯作为冶金法路线制备太阳能级硅前处理工序,可去除大部分铁铝等碱金属及硼杂质,提高最终产品收率。实验考察了湿法除硼过程主要工艺因素:浸出剂浓度、温度、时间、搅拌等对产品纯度的影响,采用SEM对产品进行表征。当工艺条件为c(HNO3)=6.5 mol/L,c(H2SO4)=6 mol/L,温度120℃、时间4 h,处理后产品中杂质质量分数为3.574×10-6,湿法过程单元的去除率为44.58%。实验结果为高等级太阳能级硅制备工业化开发大幅度降低成本提供了技术基础。     

Effect of acetic acid on the leaching behavior of impurities in metallurgical grade silicon

To explore the potential of acid leaching in purification metallurgical grade silicon (MG-Si) for solar cells, the effect of acetic acid on the leaching behavior was investigated in the present work by focusing on the behavior of impurities affected by the addition of acetic acid to a conventional acid mixture composed of hydrochloric acid and hydrofluoric acid. The etching results reveal that the HCl–HF–CH₃COOH mixture is a better lixiviant for dissolving impurity inclusions in MG-Si. The extraction yield of impurities in HCl–HF–CH₃COOH leaching was found to increase by 7% compared to conventional HCl–HF leaching.     

高频热等离子体制备特种粉体研究进展

高频感应热等离子体具有能量密度大、温度高和冷却速率快等特点,是制备特种粉体的重要手段之一. 本工作介绍了过程所在高频热等离子体制备特种粉体方面的研究进展. 利用热等离子体的高温和快速冷却过程,粗颗粒经等离子体弧高温气化,通过控制冷却速率能得到纳米粉体,利用该方法制备了纳米球形硅、铁、钴和镍等粉体,纳米硅粉可用于锂离子电池负极材料. 具有固定熔点的不规则颗粒在等离子体弧中经熔融形成球形液滴,快速冷却能获得规则致密的球形颗粒,通过等离子体球化制备了高熔点的钨、钼、铌、铬等规则致密的球形粉体. 利用活性氢的瞬时强化还原反应,采用化学气相沉积能制备超细钨、钼、镍和铜等球形金属超细粉体. 活性氧有助于调控颗粒的氧化生长过程,采用金属等的氧化反应可获得多种特殊形貌的氧化物.     

Electric current assisted sintering of AlN ceramics: thermal conductivity and transparency

Abstract

Densification, thermal conductivity and transparency of aluminium nitride ceramics densified by electric current assisted sintering are reviewed. Aluminium nitride powders could be densified without any sintering additives by electric current assisted sintering. Sintering additives, Y₂O₃ or CaF₂, and others are effective for densification, increase in thermal conductivity and transparency. As a result of the reaction with the sintering additives and oxide on the surface of the AlN powder, a secondary phase forms between AlN grains, oxygen impurity between aluminium nitride grains decreases and thermal conductivity increases. These mechanisms are effective in the sintering of aluminium nitride ceramics densified by electric current assisted sintering, though sintering time is short, within 5 min. The secondary phase formation does not always give good effect for transparency.     

Removal of Arsenic(III), Chromium(III) and Iron(III) Traces from Hydrofluoric Acid Solutions by Specialty Anion Exchangers

The removal of As(III), Fe(III), and Cr(III) at trace levels from HF solutions by means of specialty ion exchange resins has been investigated. These impurities are usually found in technical‐grade HF, and they need to be removed to prepare metal‐free HF for the semiconductor industry. It was assumed that Fe(III) and As(III) species in dilute HF were present in anionic form, while Cr(III) was probably in neutral form, CrF₃. First, a selection of specialty ion exchangers was performed. Then, fixed‐bed experiments were carried out to check the ability of selected resins to reach the impurity levels required in SEMI C29 for 5 wt.% HF (5 ppb of As, and 10 ppb of Cr and Fe). The effect of the flow rate and the HF concentration on the metal removal was studied with Purolite D‐3777 and Fuji PEI‐CS‐07 resins respectively. Fuji PEI‐CS‐07 showed the best performance for Fe(III) removal, even at high HF concentration (25 wt.%). A strong decrease in the Cr(III) and As(III) removal capacity with increasing concentration of HF was observed.     

二氧化硅溶胶的制备及性能影响研究

以正硅酸乙酯、水、乙醇和酸性催化剂为原料，制备了SiO2溶胶。研究了催化剂的种类、反应温度、反应时间、添加剂等因素对SiO2溶胶性能的影响。实验结果表明：在[H^＋]相同的条件下，酸催化剂对溶胶粘度的影响为：HF〉HCI〉HN03〉H2S04〉HAC，对凝胶时间的影响为：HAC〉H2S04〉HC1〉HN03〉HF，几种溶胶固含量的大小为：H2S04〉HN03〉HCl〉HAC，制备二氧化硅膜用硅溶胶较适合采用盐酸或硝酸作为催化剂；随着反应温度的升高，溶胶的粘度、固含量和粒径均逐步增大，凝胶时间则缩短；随着反应时间的延长，溶胶的粘度、固含量以及粒径逐步增大，凝胶时间则变短；向在溶胶中加入DMF后，溶胶粘度、固含量变小，凝胶时间延长，SiO2粒子的粒径增大。     

Low temperature synthesis of AlN by addition of various Li-salts

The effect of various Li-salts on the low temperature synthesis of AlN by direct nitridation of Al metal was investigated using four Al powders with average particle sizes of 3, 20, 100 and 150 μm. These were mixed with various Li-salts (LiNO₃, LiOH·H₂O and Li₂CO₃) in different concentrations and fired at various temperatures under flowing N₂. The as-received Al powders without Li addition showed AlN formation at about 600 °C in the 3 and 20 μm samples but no AlN formation up to 850 °C in the 100 and 150 μm samples. The crystallinity of the AlN products, where formed, was however low. By contrast, all the Al powders with added Li-salts showed AlN formation up to 800 °C, with LiOH·H₂O being especially effective. Thus, the AlN formation temperature can be significantly lowered in the coarser powders by the addition of Li-salts but the effect is less in the finer powders which undergo low temperature nitridation below the melting point of Al metal even without Li. The crystallinity of the AlN products was higher in the samples containing Li-salts than without Li-salts.     

超细硼化锆粉体纯化工艺探究

探究了超细ZrB2粉体化学提纯、热处理等纯化工艺过程中的影响因素.并采用热重-差热分析仪、X射线衍射仪、扫描电镜、透射电镜和X射线荧光光谱分析仪对ZrB2粉体及热处理后的水洗产物进行表征和分析.结果表明:B2O3易溶于热水生成硼酸溶液,为了有效地除去B2O3,需经过热水反复洗涤、过滤;随着热处理温度增加,粉体中的C杂质逐渐氧化挥发,但当热处理温度升至700℃时,产物中的ZrB2被氧化生成ZrO2,致使产物迅速增重;热处理温度650℃和热处理时间80min为最佳热处理除杂工艺,此时产物中残留的碳基本全部被除去,但是产物中氧含量较高,后期研究建议选择在惰性气氛中进行.