TiO2对连铸保护渣结晶性能的影响

采用热丝法结晶性能测定仪及XRD,研究了不同冷却速率条件下TiO2对连铸保护渣结晶性能的影响。结果表明：在相同冷却速率条件下,随着TiO2加入量的增加,连铸保护渣的结晶温度和结晶化率随之增大。TiO2加入量（质量分数）为15％和20％条件下,连铸保护渣的结晶化率在不同冷却速率下都接近100％。添加少量的TiO2可以降低连铸保护渣的结晶温度和结晶化率。确定了TiO2加入量（质量分数）为20％时连铸保护渣析出晶体的种类。     

TiN对连铸保护渣黏度的影响

采用旋转黏度计并结合XRD分析系统研究了不同碱度条件下,TiN对连铸保护渣黏度的影响。结果表明TiN可以增加连铸保护渣的黏度。TiN加入量〈5％时,对连铸保护渣的黏度影响较小。随着CaO／SiO2的增大,添加10％TIN连铸保护渣的黏度先迅速减小而后有所增大。添加10％TIN,CaO／SiO2为0．3的连铸保护渣中仅存在TiN晶体。CaO／SiO2为1．5的连铸保护渣中出现钙钛矿（CaTiO3）、硅酸二钙（Ca2SiO4）、枪晶石（Ca4Si2O7F2）、霞石（NaAlSiO4）及TiN。     

不同温度条件下连铸保护渣结晶性能的研究

实验采用热丝法熔化结晶性能测定仪对连铸保护渣的结晶性能进行了研究。结果表明:不同的实验温度条件下,连铸保护渣的结晶化率和结晶时间相差很大。在实验条件下,实验温度为1 000,1 200℃时,连铸保护渣的结晶化率均达到100%,但结晶时间随着实验温度的上升而减少,分别为262,99 s。实验温度为1 300℃时,连铸保护渣没有发现晶体析出。     

添加剂对连铸保护渣粘度及流动性的影响

研究了不同添加剂Li2CO3,NaF,Na2CO3,冰晶石及硼砂对连铸保护渣粘度及流动性的影响。实验表明,Li2CO3,NaF,Na2CO3,冰晶石及硼砂均可以降低连铸保护渣粘度,增加流动长度,其中Li2CO3和NaF的作用效果更加明显。     

连铸保护渣配碳模式的研究

采用熔点熔速测定仪研究了连铸保护渣的熔化特性,最终得到连铸保护渣的配碳模式.结果表明:连铸保护渣的熔化过程由碳质材料控制熔化阶段和渣系成分控制熔化阶段两部分组成.保证连铸保护渣符合熔化性能的要求,确定最终的配碳模式需同时考察连铸保护渣的熔化曲线斜率和熔化时间.     

铌在高碳钢凝固过程中行为特性的模型分析

以高碳钢为研究对象,建立钢液凝固过程中溶质偏析与夹杂物析出的耦合热力学模型,并通过扫描电镜及能谱分析验证了模型的精确度。利用该热力学模型,研究分析了铌的质量分数对高碳钢凝固过程中铌的赋存状态及铌化物的影响作用规律。结果表明:(1)碳化铌和固溶铌在高碳钢凝固过程中开始析出,随着碳质量分数的增大,固溶铌的浓度分布呈现先减小而后增大的趋势;(2)随着铌质量分数的增大,高碳钢中碳化铌的析出温度及析出量均有所增大,固溶铌的平均析出量逐渐增大,其中碳化铌析出量的增加十分显著。     

合金元素对20CrMnTi凝固组织影响的数值模拟

利用CA（元胞自动机）和FE（有限元）耦合模型，模拟齿轮钢中Si、 Mn、 Cr、 Ti 4种元素对连铸坯凝固组织的影响。模拟所得温度场和凝固组织跟实际数据基本吻合。在国标规定的成分范围内， Si含量增加可降低钢种液相线温度，增加形核动力，从而增加晶粒数目，细化晶粒； Ti含量可增加钢中异相形核数，从而增加晶粒数目，细化晶粒； Si， Ti含量增加还可降低枝晶尖端生长速度，从而减小柱状晶区域，扩大等轴晶区域； Mn， Cr含量变化对于钢种的液相线温度以及枝晶尖端生长速度影响不大，因此对于晶粒数目，等轴晶面积影响较小。     

重型燃气轮机用Ni-Cr-Co基高温合金组织稳定性研究

采用Thermal-Calc(TCW2)软件结合Ni基数据库(2003P)对Haynes 282合金的平衡凝固组织进行计算,并提供了Haynes 282合金等温时效组织转变曲线(TTT曲线),采用扫描电镜(SEM)、透射电镜(TEM)、电子衍射和综合相分析方法研究了Haynes 282合金经过高温长期时效处理和在持久试验断裂后的微观组织。结果表明：Haynes 282合金在800℃下经过长期时效处理后会析出TCP相;Haynes 282合金中析出的针状相均为富含Mo元素的μ相;温度为700～800℃时,Haynes 282合金中μ相析出的尺寸和含量均会随时效时间的延长和温度的升高而增大,表明Haynes 282合金在高温长时应力作用下的组织不稳定性。     

连铸保护渣数据库查询系统的设计开发

以Microsoft Visual Basic6.0为编译工具,查阅并检索了国内外钢铁企业现场使用的连铸保护渣相关资料,建立了连铸保护渣数据库查询系统.该查询系统可以将连铸保护渣相关数据归类存储,并通过单项和多项组合检索对其相关内容进行查询,为连铸保护渣的选择应用和设计开发提供充分的理论依据.依据此检索结果,设计开发了...     

TiO2-xNx光催化剂的制备及其活性研究

在sol-gel法制备TiO2的过程中引入氨水进行水解,制备了具有可见光活性的TiO2-xNx催化剂,采用UV-Vis、BET、XPS等手段进行表征,以苯甲酸为模型污染物,氙灯为模拟太阳光源,评估了催化可见光催化活性.结果表明,随着焙烧温度的升高,TiO2-xNx的吸光特性增加,当温度超过350%后TiO2-xNx中的氮会在高温下被氧化掉,其吸光特性又降低;此时TiO2-xNx的吸收阈值为422nm,对应的禁带宽度为2.9eV;孔径分布在2.5～8.2nm之间,BET比表面积为139.3m2/g;经计算其x=0.0282,即TiO2-xNx可表示为Ti1.9718N0.0282;在入射波长分别为500nm和600nm时,TiO2-xNx对苯甲酸的去除率分别为6.5%和4.6%,相应的矿化率为3.2%和2.5%.     

Copper metallization for crystalline Si solar cells

Cu metallization for crystalline Si solar cells was investigated using either Ti or Ti/TiN diffusion barriers. The resistivity and the specific contact resistance change were measured for both Ti(30 nm)/Cu(100 nm) and Ti(30 nm)/TiN(30 nm)/Cu(100 nm) contact structures under various annealing conditions. As the annealing temperature increased, the efficiency of the cells increased mainly due to the increase in fill-factor and I_SC, which was correlated with the series resistance (R_S) of the metal layer. The solar cells with Ti/TiN/Cu contacts generally showed the higher efficiencies than those with Ti/Cu, because in Ti/Cu contacts Cu diffused through Ti and increased R_S.     

Novel hybrid coating of TiN and carbon with improved corrosion resistance for bipolar plates of PEM water electrolysis

Surface modification of Ti based bipolar plates (BPs) could be an effective solution to prevent the formation of low-conductive oxide film, promote the corrosion resistance and electronic conductivity as well. In this work, a novel hybrid coating composed of nano-sized TiN and carbonaceous phases (TiN–C) was successfully established on a Ti substrate via a combined electrophoretic deposition and thermal treatment process. Various physiochemical characterizations revealed that the coating was uniform, and the formation of the nano-sized TiN and carbonaceous composites reduced the interfacial contact resistance significantly. The potentiodynamic and potentiostatic polarization tests indicated that the hybrid coating TiN–C prepared at 400 °C had a corrosion current density of only 1.41 μA cm⁻², which was an order of magnitude lower than that (36.02 μA cm⁻²) of the bare Ti. Furthermore, the as-prepared coating showed excellent durability in both the simulated PEMWE environment and the PEMWE cell under polarization at 1.7 V for more than 300 h.     

Effect of nitride additives on Li-N-H hydrogen storage system

Solid state reaction between LiNH₂ and LiH potentially offers a practical pathway for hydrogen supply to fuel cell powered vehicles, particularly if the reaction kinetics can be further improved. Here we performed a comparative study of the effects of selected micron and nano-sized nitrides using temperature programmed desorption, mass spectrometry, X-ray diffraction and infrared spectroscopy. It was found that both micron and nano-sized BN and TiN act as effective catalysts within the system. While an increase in the concentration of TiN reduces dehydrogenation temperature, the opposite was observed for BN catalyst. Employment of both nano and micron-sized BN catalysts resulted in an almost similar dehydrogenation temperature; but dehydrogenation temperature was decreased about 20 °C by switching from micron to nano-sized TiN. The catalytic effects of the additives were proposed to be an improvement of surface reactivity and diffusion enhancement across the interface of the reactants. However, the role of BN and TiN are different in the way that TiN is likely to improve the surface reactivity of LiNH_2, while BN mainly enhances diffusion across the interface of the reactants. Our findings also indicate that TiCl₃ behaves like TiN, as a catalyst in Li-N-H system.     

Numerical simulation of filling and solidification of permanent mold castings

Filling of a mold is an essential part of the permanent mold casting process and affects significantly the heat transfer and solidification of the melt. For this reason, accurate prediction of the temperature field in permanent mold castings can be achieved only by including simulation of filling in the analysis. In this work we model filling and solidification of a casting of an automotive piston produced from an aluminum alloy. Filling of the three-dimensional mold is modeled by using the volume-of-fluid method. Fluid mechanics and heat transfer equations are solved by a finite element method. Comparisons of numerical results to available experimental data show that the formulated model provides a solution of acceptable accuracy despite some uncertainty in material properties and boundary and initial conditions. This implies that the model can be a viable tool to design permanent molds.     

Coated stainless steels evaluation for bipolar plates in PEM water electrolysis conditions

Proton exchange membrane water electrolysis (PEMWE) is a promising technology to be incorporated in the production of green hydrogen, but one of its limitation to market penetration is the cost of bipolar plates (BPP).Aiming to reduce the cost of PEMWE stack, different surface engineered coating systems based on CrN/TiN, Ti/TiN, Ti and TiN deposited by physical vapor deposition on SS 316L, SS 904L and SS 321 were tested, as potential cost effective solutions to be implemented on bipolar plates. A corrosion evaluation has been carried out in anodic PEMWE conditions in order to determine the best substrate/coating combination for bipolar plates. Ti/TiN multi-layered coating on SS 321 shown the best performance with ?0.02% weight loss, current at 2 V_SHE to 436 μA cm^?2 and ICR after corrosion test to 9.9 mΩ cm².     

Effects of transition metal Ti and its compounds on hydrogen adsorption performance of Mg17Al12

Catalytic effects of Ti, Ti_n (n = 2–4), TiC, and TiO₂ clusters on hydrogenation of the Mg17Al12(110) surface were investigated by using density functional theory. The geometry structure, adsorption energy, dissociation barrier, density of state, electron density, and electron density difference were calculated. As a result, the adsorption energy and dissociation barrier of hydrogen on the Ti-containing Mg17Al12(110) surfaces were effectively improved as compared with the clean Mg17Al12(110) surface. Such as the adsorption energy of H(H2) on the Mg17Al12(110) surface was ?0.18 (?0.13) eV, while the related energy of H(H2) on the Mg17Al12(110)/TiO2 system was ?1.50 (?1.22) eV. In addition, H2 molecules could be spontaneously dissociated to H atoms on the Mg15Ti2Al12(110), Mg17Al12(110)/Ti3, and Mg17Al12(110)/TiO2 surfaces. The results of electronic structures indicated that the H s states principally hybridized with the Ti s and d states. The mechanism of Ti, Ti_n (n = 2–4), TiC, and TiO2 clusters on the promoted hydrogenation of Mg17Al12 was explained.