Selective enrichment of TiO2 and precipitation behavior of perovskite phase in titania bearing slag

1 Introduction China is rich in mineral resources of titanium, 92.4% of which is vanadium-titanium bearing magnetite, deposited mostly around the southwestern part. About 53% titanium is in the iron concentrate after mineral processing, after smelting pro…     

Oxidization mechanism in CaO-FeOx-SiO2 slag with high iron content

Oxidization mechanism in CaO-FeOx-SiO2 slag with high iron content was investigated by blowing oxygen into molten slag so as to oxidize Fe（ Ⅱ）. The relationship between Fe（ Ⅱ ） content and oxidizing time at different temperatures was obtained by chemical analysis. Microstructure of slag was observed by metallographic microscope and SEM. Phases compositions were ascertained by EDXS and XRD. Grain size and crystallizing quantity of magnetite（Fe3O4 ） were determined by image analyzer. The oxidizing kinetic equations were deduced. Confirmed by graphical construction method, Fe（ Ⅱ ） oxidizing reaction in CaO-FeOx-SiO2 slag system is of first order, and the reaction apparent energy Eo is 296. 67 kJ/mol in the pure oxygen and 340. 30 kJ/mol in air. The enrichment and crystal growth mechanism of magnetite（Fe3O4 ） phases were investigated. In oxidizing process, content of fayalite declines, while that of magnetite（Fe3O4 ） increases, and iron resources enrich into magnetite（Fe3O4 ） phase. All these provide a theoretical base for compressive utilizing of those slags.     

Preparation, characterization and photocatalytic activity of sulfuric acid-modified titanium-bearing blast furnace slag

The feasibility of reducing Cr(VI)from the aqueous solution by sulfuric acid-modified titanium-bearing blast furnace slag(SATBBFS)as a photocatalyst was investigated.The photocatalysts were examined by X-ray diffraction(XRD),UV-vis diffuse reflectance spectra,thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FTIR).The photocatalytic activities of the different catalysts were evaluated by the photocatalytic reduction of Cr(VI)under UV-vis light irradiation.The results show that the photocatalytic activities of SATBBFS catalysts are strongly dependent on CaTiO3-to-TiO2 mass ratio,adsorption capacity and surface acidity,and SATBBFS calcined at 400°C shows a higher photocatalytic activity compared with other catalysts.     

含钛高炉渣中钛组分选择性富集及钙钛矿结晶行为

攀钢含钛高炉渣工艺矿物学分析结果表明 ,钙钛矿是主要的富钛相。采用CaO和Fe2 O3对原高炉渣进行改性处理 ,不仅提高了钙钛矿的析出温度 ,而且使另外两种主要含钛矿物攀钛透辉石和富钛透辉石析出的温度显著降低。在适当热处理条件下 ,近 80 %的钛组分进入钙钛矿相中 ,而且钙钛矿的平均晶体尺寸达 90 μm ,实现了熔渣中钛组分的选择性富集并为选矿分离创造了条件。     

Isothermal precipitation and growth process of perovskite phase in oxidized titanium bearing slag

The isothermal precipitating behavior of perovskite phase in oxidized titanium bearing slag was studied by quenching method. The kinetics of precipitating process and crystal growth of perovskite phase was analyzed. The results show that the precipitating and growth of perovskite are non-equilibrium process at the beginning of isothermal treatment. There are two factors influencing the growth rate of perovskite phase on non-equilibrium condition, one is the supersaturation concentration of perovskite and the other is the coarsening arising from the growth of larger perovskite at the expense of smaller ones. The precipitation kinetics of perovskite phase can be nearly described by the JMAK equation.     

低Ni/Cu比钢中铜的富集行为

采用热重分析仪和扫描电镜研究了不同加热温度和升温速率下Ni/Cu比为0.39的低Ni/Cu比含铜钢铜富集行为。研究结果表明:在1050～1300℃加热温度范围内,富集相以富Cu-Ni相和富Ni相为主,且以颗粒形式弥散分布于氧化皮内部或氧化皮与钢基体界面;除1250℃外,随加热温度升高,富集相中Ni/Cu比值逐渐增加,在1200℃和1300℃时,富集相仅为富Ni相。加热温度为1250℃时,升温速率不同,富集相的Ni/Cu比值和氧化皮与钢基体界面形态不同:采用5℃/min低速升温和15℃/min高速升温均有利于增加Ni/Cu比值,而采用10℃/min中速升温导致Ni/Cu比值偏低;增加升温速率,缩短加热时间,使氧化皮与钢基体界面更加平滑,有利于除鳞以改善钢材表面质量。对生产高表面质量低Ni/Cu比含铜钢而言,可采取低温加热或高温加热,将加热温度分别控制在1180～1220℃或者1280～1320℃;也可采用1220～1280℃中温加热,将弱氧化性气氛下分阶段步进梁加热炉的第三阶段升温速率控制在15℃/min左右。     

铜在富FeO熔渣中的氧化溶解行为

在1873 K条件下对铜在富FeO熔渣中的氧化溶解行为进行了研究.结果表明:铜氧化物在富FeO熔渣中以Cu2O的形式存在;熔渣中CaO的含量将对铜的氧化溶解产生影响,随着渣中CaO含量的增加,熔渣中的铜含量逐渐下降,但在不同温度下,这种影响的作用各不相同;当温度较高时,渣中CaO含量对铜的氧化溶解影响较大,且随着温度的降低,其影响作用明显变缓;反应体系的氧分压对铜的氧化溶解影响较大,在熔渣中γ(CuO0.5)不变的情况下,铜氧化物的溶解与体系氧分压的四分之一次方之间呈正线性关系.     

钢包顶渣改质对抑制旋涡卷渣的影响

钢包加盖能够显著提升钢包的保温效果,助力钢铁企业节能降耗。但钢包加盖条件下顶渣温度较高、流动性好,更易引起浇注末期旋涡卷渣,铸坯夹渣缺陷率升高。开展了顶渣改质抑制旋涡卷渣的工艺研究,以高碱度渣为研究对象,通过相图分析确定了炉渣改质增黏的基本思路,利用FactSage软件对多组改质渣系进行黏度计算。结果表明,添加石灰或轻烧白云石都有助于增大炉渣黏度,两者增黏效果相近,炉渣黏度测量试验也验证了上述结论。利用BaCO₃示踪法开展了顶渣改质的工业试验,结果表明,炉渣改质后钢中大尺寸夹杂物数量大大减少。顶渣改质新工艺在现场应用后,铸坯平均夹渣缺陷率由0.57%降低至0.42%。     

合成高炉渣中TiO_2还原的发泡特性参数

测定了在不同条件下 ,合成高炉渣中TiO2 被碳还原时泡沫渣高度与时间的关系。由实验数据和改进的计算程序确定了该发泡过程的发泡特性参数 ,实现了对发泡过程进行定量描述。着重分析了初渣中TiC的含量和还原过程产生TiC对发泡过程的影响 ,确定了引起含高TiO2 渣在发泡时产生多次发泡的原因。     

焊接电流和药皮厚度对水下湿法焊接熔渣物相及微观组织的影响

文中采用自制的金红石型药皮焊条进行水下湿法焊接,重点分析了焊接电流和药皮厚度对熔渣物相及微观组织的影响.对熔渣的宏观形貌分析发现,当药皮厚度较薄时,焊后熔渣稀薄,覆盖不均匀,此外,焊接电流对焊接飞溅有重要影响,当焊接电流较大时,焊接过程中有大量飞溅产生.通过对熔渣的碱度系数及物相分析得出,熔渣的主要组成相为FeTiO₃和CaTiO₃,还有少量的MnTiO₃,FeF₃和Ca-Si-O相,药皮厚度和焊接电流对熔渣的碱度系数和组成相影响均较小.熔渣的微观组织分析发现,减小药皮厚度和增大焊接电流,熔渣中生成大量的树枝状组织,熔渣微观组织的方向性增强,有利于脱渣.     

钛渣中钙钛矿的浮选分离及其机理

研究了捕收剂油酸、羟肟酸、十二烷胺双甲基膦酸 ,抑制剂氟硅酸钠、水玻璃对改性渣中钙钛矿浮选的影响。通过浮选溶液化学计算、矿物动电电位、红外光谱等研究 ,探讨了羟肟酸在钙钛矿表面的作用和水玻璃抑制钛辉石的作用机理。结果表明 :以羟肟酸为捕收剂 ,水玻璃为抑制剂可实现钙钛矿与钛辉石等的浮选分离。钙钛矿和钛辉石晶体表面的Ca,Ti质点密度不同 ,所处的位置及活性不同 ,造成二者浮游性有一定的差异 ;钙钛矿在整个研究范围内 ζ电位始终为负值 ,但在阴离子捕收剂C5-9羟肟酸中可浮性良好 ,表明C5-9羟肟酸在钙钛矿表面发生了化学吸附。红外光谱研究证实 ,C5-9羟肟酸的CN ,N—O官能团与钙钛矿表面的钛质点发生了化学键合。     

TiO_2含量对等离子喷涂Al_2O_3热障涂层性能的影响(英文)

采用等离子喷涂技术在6061铝合金表面制备了不同含量TiO2的氧化铝陶瓷涂层,研究了涂层的相组成、隔热性能及耐腐蚀性。实验结果表明:在喷涂过程中陶瓷层中均有物相的转变。随着粉末中TiO2含量的增加,涂层的耐腐蚀性增强但是隔热性下降。这可能是由于TiO2的导热系数比Al2O3的导热系数高,但其熔点比Al2O3的熔点低,同时脆性较小,在喷涂过程中,TiO2弥散分布在脆性的氧化铝基体中起到了封孔及释放应力、减少裂纹的作用。     

熔渣成分和微观结构对自保护药芯焊丝脱渣性的影响

研究了TiO₂和Al₂O₃对CaO-SiO₂-CaF₂基础焊接渣系黏度、熔化温度、表面张力等熔化特性的影响,并利用XRD和拉曼光谱分析四元焊渣的物相和结构特征. 结果表明,TiO₂含量增加会显著降低焊接熔渣黏度、熔化温度及表面张力,提升熔渣流动性;Al₂O₃含量增加会使焊接熔渣黏度、熔化温度及表面张力先略有升高后明显降低. CaO-SiO₂-CaF₂-TiO₂和CaO-SiO₂-CaF₂-Al₂O₃四元焊渣完全熔化后,其黏度均在0.2 Pa·s以下,继续升温对黏度无显著影响,低于熔化温度后,焊渣随温度降低迅速凝固,呈明显的短渣特性. 经XRD和拉曼光谱分析可知,四元焊接熔渣中主要含具有硅酸盐网络结构的Ca₄Si₂O₇F₂高熔点相. TiO₂ 和Al₂O₃的加入均能使硅酸盐网络结构转变成简单四面体结构的[SiO₄]⁴⁻,且含TiO₂渣中生成了CaTiO₃新相,含Al₂O₃渣中产生CaF₂相和少量Ca₂Al(Al SiO₇)新相. 发现了对渣系熔化特性影响较大的TiO₂和Al₂O₃含量敏感区间,对高强钢焊材配方设计具有一定参考意义.     

Na2O对含MgO铝酸钙炉渣相变规律和氧化铝浸出性能的影响（英文）

采用向铝酸钙炉渣体系中添加Na2O的方法,降低或消除铝酸钙炉渣中MgO的负作用,并分析其影响机理。结果表明:当MgO含量为3%时,Na2O的添加量由0增加至4%后,炉渣的氧化铝浸出率由68.73%提高到80.86%。对含4%Na2O的样品进行XRD分析,发现四元化合物C20A13M3S3已消失。添加Na2O不能完全消除MgO对炉渣浸出性能的负作用。XRD和EDS分析结果表明,Na2O会进入12CaO·7Al2O3的晶格并促进其形成。     

球磨纳米TiO2的结构转变

采用X射线衍射研究锐钛矿型纳米TiO2在高能球磨过程中及球磨后的纳米TiO2在退火过程中的结构变化。结果表现在室温常压下高能球磨诱发锐钛矿相转变为金红石相和S相。随着退火温度升高，球磨纳米TiO2粉末的晶粒逐渐长大，锐钛矿相逐渐转变为金红石相，而S相并不直接转变为金红石相而是先转变为锐钛矿相，然后由锐钛矿相转变为金红石相。与未球磨的纳米TiO2相比，高能球磨导致的晶粒细化，显微畸变以及晶格缺陷密度的增加而引起的额外储能使球磨后纳米TiO2的锐钛矿相-金红石相转变温度明显降低。     

添加剂氧化钙对镍渣强化还原的影响

针对铁以铁橄榄石形式存在而难以直接还原磁选回收的问题,采用在镍渣中配加CaO提升镍渣碳热还原速率及铁金属化率的技术思路。将添加剂与镍渣按比例混合并配加适量还原剂后,在高温炉中进行还原,结合热力学计算及产物特征分析结果,研究添加剂强化还原的机理及还原效果。结果表明:CaO的加入有效促进了硅酸铁的解离,强化了还原过程,还原速率加快,金属相在渣相中的形态结构发生改变,金属铁的聚集长大明显,有利于后续分离回收。随着CaO添加量由0增加到10%(质量分数),还原产物的金属化率和Fe颗粒平均粒径呈先增大后减小的趋势,FeO含量和残碳量变化规律相反。在CaO添加量为8%时,还原产物中铁的金属化率和粒径达到峰值,分别为87.25%和41.3μm。     

345MPa级耐候钢中Ni对Cu富集行为的影响

用扫描电镜和电子探针研究了含Ni和不含Ni两种成分的345 MPa级耐候钢的Cu富集行为。经1200℃保温2 h后,含Ni钢的氧化层较薄,厚度为132μm,大量白色富铜相在外氧化层中形成。在热轧除鳞时,含富Cu相的外氧化层脱落,热轧板表面形成较平整的二次氧化铁皮,钢板表面光滑。不含Ni耐候钢的氧化层较厚,为177μm,富Cu相主要在内氧化层中形成,并沿奥氏体晶界渗入基体。富Cu的内氧化层粘附于基体表面,不易随鳞脱落,在热轧时轧入基体,使得热轧板表面粗糙。本文通过试验分析提出了在钢中添加Ni避免热脆的机理。     

电工钢钢包渣结壳问题分析

针对电工钢生产过程中钢包渣结壳的现象,与不结壳渣进行对比,从物质的组成,物相和黏度等3个方面进行了分析。结果表明,随着温度的降低,炉渣中析出大量的高熔点物相如MgO、尖晶石(MgO·Al₂O₃)、2CaO·SiO₂等,在炉渣中起到“钉扎”强化作用的同时又能导致炉渣的黏度增加,失去流动能力,从而容易黏附在一起结块成壳。此外,提出了预防钢包渣结壳的有关措施。     

Dissociation of Ti2O3 from titania slag under mechanical activation

In this present study, the effects of mechanical activation on the characterization of titania slag were systematically investigated. The crystal structures, surface chemical functional groups, and microstructure of the samples were characterized before and after mechanical activation using XRD, FT-IR, and Raman spectroscopy techniques, respectively. It was found that untreated titania slag under mechanical activation was mainly composed of Fe₃Ti₃O₁₀ and rutile TiO₂, but that of being treated by mechanical activation was mainly composed of Fe₃Ti₃O₁₀, Ti₂O₃ and rutile TiO₂. Ti₂O₃ is transformed partially from Fe₃Ti₃O₁₀ under moderate mechanical activation conditions for 12 h. The demonstration of mechanical activation techniques can be applied effectively and efficiently to the treatment processing of titania slag.     

Wetting characteristics of CaO−SiO2−Al2O3 ternary slag on refractory oxides, Al2O3, SiO2 and TiO2

The wettabilities of the metallurgical slag, CaO−55.2 wt.%SiO₂−15 wt.%Al₂O₃ on refractory oxides, Al₂O₃, SiO₂ and TiO₂ were investigated at temperatures of 1350, 1400 and 1470°C. Contact angle measurements were performed using a combination of the sessile drop method and the X-ray fluoroscopic technique. The contact angle was obtained from the numerical solution of the Young-Laplace equation. The steady contact angles obtained were 31°, 24°, and 15° for SiO₂, Al₂O₃ and TiO₂ at 1470°C, respectively. The spreading rate of the liquid slag was characterized by the formation of cognate interface between the liquid slag and solid oxide, and further enhanced by the formation of a diffuse layer around the slag drop at higher temperatures.