Dissolution of Al2TiO5 inclusions in CaO-SiO2-Al2O3 slags at 1823 K

Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel.A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K.The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur.SiO2 diffuses or penetrates the inclusion more quickly than CaO,as indicated by the w(CaO)/w(SiO2) value in the reaction region.A liquid product (containing 0.7-1.2w(CaO)/w(SiO2),15wt％-20wt％ Al2O3,and 5wt％ -15wt％ TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag.Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag.With increasing reaction time,the boundary reaches its largest distance,the Al2TiO5 dissolution rate equals the liquid product diffusion rate,and the dissolution process remains stable until the inclusion is completely dissolved.     

Al 脱氧弹簧钢钙处理过程中铝酸钙硫化物析出热力学分析

通过钢液与夹杂物间的热力学平衡计算,对Al脱氧弹簧钢钙处理过程中铝酸钙硫化物的析出行为进行热力学分析,探讨[Al]、[Ca]、[S]浓度和钢液温度对Al2O3夹杂物变性行为的影响。结果表明,1600℃钢液温度下,w[Al]＝0．03％时,Al2O3生成为低熔点12CaO ·7Al2O3时的 w[Ca]＞0．0034％,其值随钢液温度降低而减小,随铝含量增大而增大。CaS析出时的临界钙含量随钢液温度降低而显著减小,当w [S ]＜0．005％时,w[Ca]随w[S]变化而显著变化。要使钢中夹杂物控制在低熔点12CaO ·7Al2O3区域,需控制w [S]＜0．0037％,该值随钢液温度的降低或铝含量的增大而减小。     

Ti-C-Al-Fe2O3体系原位合成钢基复合材料组织与形貌研究

采用Ti-C-Al-Fe2O3反应体系,结合铸造和自蔓延高温合成（SHS）两种工艺,在湿砂型中浇注高温熔融的钢水,引燃SHS压块,从而发生自蔓延高温合成反应,生成了高硬度的陶瓷相TiC、Al2O3.通过改变Ti-C-Al-Fe2O3体系组分配比,探讨了体系在金属液内SHS反应对原位内生TiC、Al2O3尺寸与分布的影响.结果表明,随着过量Al元素的增加,陶瓷增强颗粒尺寸逐渐减小且分布更均匀;稀土CeO2加入量的增加,增强区更加致密,稀土CeO2添加剂含量为0.8%时制备的复合材料中原位形成的Al2O3、TiC颗粒尺寸较小,分布均匀.     

Inclusion variations and calcium treatment optimization in pipeline steel production

SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment,and samples were taken from the ladles,mould,and slabs.Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions,morphology,and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al2O3 inclusions,but they turn to fine irregular CaS-CaO-Al2O3 compound inclusions after the treatment,then become fine globular CaO-Al2O3 inclusions in the mould,and finally change to a few larger irregular CaS-CaO-Al2O3 complex inclusions in the slabs.Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca,Al2O3,and S and the precipitation of S in CaO-Al2O3 inclusions with high sulfur capacity.New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling,and the calcium process was studied and optimized.     

钢包渣中的氧化物与氮反应的热力学研究(一)

通过对钢包渣中Al2O3,B2O3,TiO2等氧化物与氮反应的理论计算可知:还原性钢包渣的氧化物在低压的情况下可与氮反应,对钢液脱氮有利;钢液在深脱氧的情况下,熔渣中氧化物能较好脱出钢液中的氮;其中B2O3,TiO2两种氧化物对钢液脱氮的促进作用比Al2O3强.     

铸造/SHS法制备TiC-Al2O3钢基表面复合层的研究

采用Ti-C-Al-Fe2O3反应体系,结合自蔓延高温合成（SHS）和铸造两种工艺,制备TiC-Al2O3钢基复合材料.对Ti-C-Al-Fe2O3体系进行了热力学计算,并结合XRD及DSC分析,为本体系合成TiC,Al2O3提供理论依据.热力学计算表明：在1600℃的钢液引燃的SHS反应过程中,只能生成Al2O3,TiC两种产物.通过XRD分析也证明了在反应产物中只有Al2O3,TiC两种物质形成.并对本体系的动力学进行分析,结果表明,紧实率为55%～65%的预制块,反应进行的最充分,钢液的浸渗能力最强;陶瓷增强颗粒尺寸随着过量Al元素的增加而逐渐减小并且分布更均匀.     

CaO-Al_2O_3-SiO_2系统微晶玻璃的振动光谱研究

通过红外光谱及拉曼光谱,研究了CaO－Al2O3－SiO2系统微晶玻璃的微观结构．系统分析TCaO、Al2O3、B2O3取代SiO2后成分变化对微晶玻璃结构的影响．从振动光谱研究及理论分析两个角度讨论了Al3 、B3 的配位状态变化,并得到一致结论。     

Study on the isothermal oxidation behavior in air of Ti_3AlC_2 sintered by hot pressing

The isothermal oxidation behavior at 900―1300℃ for 20 h in air of bulk Ti3AlC2 with 2.8 wt% TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally followed a parabolic rate law. The parabolic rate constants increased from 1.39×10-10 kg2·m-4·s-1 at 900℃ to 5.56×10-9 kg2·m-4·s-1 at 1300℃. The calculated activation energy was 136.45 kJ/mol. It was demonstrated that Ti3AlC2 had excellent oxidation resistance due to the continuous, dense and adhesive protect scales consisted of a mass of α-Al2O3 and a little of TiO2 and/or Al2TiO5. In principle, the oxide scale was grown by the inward diffusion of O2- and the outward diffusion of Ti4 and Al3 . The rapid outward diffusion of cations usually resulted in the formation of cracks, gaps, and holes.     

Al2O3对3Ti/Si/2C体系自蔓延高温合成Ti3SiC2的影响

以3Ti/Si/2C粉体为原料,通过自蔓延高温合成技术合成了Ti3SiC2材料。研究了Al2O3助剂对自蔓延高温合成Ti3SiC2的影响。研究结果表明,3Ti/Si/2C粉体会发生自蔓延反应,产物的组成相为TiC、Ti3SiC2和Ti5Si3,产物中Ti3SiC2含量约为23%。添加适量的细粒度Al2O3可显著促进反应合成Ti3SiC2,3Ti/Si/2C/0.1Al2O3原料反应后得到的产物中Ti3SiC2含量达64%。     

MoP/TiO_2-SiO_2-Al_2O_3的制备及加氢脱芳性能研究

采用溶胶—凝胶法及共浸渍法制备了TiO2-SiO2-Al2O3复合载体,并用共浸渍法制备负载型MoP/TiO2-SiO2-Al2O3催化剂。XRD结果表明,TiO2的晶相衍射峰呈锐钛矿,SiO2则大多以无定型态分散于γ-Al2O3晶体表面。通过原位还原技术对催化剂进行还原处理,在连续固定床反应器上进行活性评价,结果表明,钛硅铝物质的量比对催化剂的活性有很大的影响,在温度为360℃,压力为3MPa,液时空速为1h-1,氢油体积比为500∶1的反应条件下,n（Ti）∶n（Si）∶n（Al）为1∶1∶4,Mo负载量为20%时,MoP/TiO2-SiO2-Al2O3催化剂的加氢脱芳活性最高,达到65.6%。并且TiO2-SiO2-Al2O3三元复合载体比传统的γ-Al2O3和SiO2-Al2O3二元复合载体的活性分别提高了19.6%和13.6%。     

Influence of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass-ceramics

ZrO2 was added into CaO-Al2O3-SiO2 glass-ceramics and the effect of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass ceramics was investigated. The results show that the sintering shrinkage ratio of glass particles decreases with the increase of the content of ZrO2. ZrO2 has an unfavourable effect on sintering shrinkage ratio of glass particles. The sintering shrinkage ratio of glass particles increases with the increase of sintering temperature. The increase of sintering temperature favors the decrease of the liquid phase viscosity of glass particles. ZrO2 has little effect on crystallization of main crystalline phase （β-wollastonite）. However, it promotes the crystallization at relatively low temperature.     

Oxidation behavior of in-situ Al2O3/TiAl composites at 900℃ in static air

In-situ Al2O3/TiAl composites were successfully synthesized from the starting powders of Ti, Al, TiO2 and Nb2O5. The oxidation behavior of the composites at 900℃ in static air was investigated. The results indicate that the composite samples present a much lower oxidation mass gain. Under long-time intensive oxidation exposure, the formed oxide scale is multi-layer. The formation of the outer TiO2 layer is fine and dense, the internal Al2O3 scale has good adhesiveness with the outer TiO2 scale, and the TiO2+Al2O3 mixed layer forming the protective oxide scale is favorable for the improvement of oxidation resistance. It is believed that the incorporation of Al2O3 particulates into the metal matrix decreases the coefficient of thermal expansion of the substrate, and forms a local three-dimensional network structure that can hold the oxide scale. The formation of the oxide scale with fmer particle size, stronger adherence, less micro-defects and slower growth rate can contribute to the improvement of oxidation resistance. Nb element plays an important role in reducing the internal oxidation action of the materials, restraining the growth of TiO2 crystals andpromoting thc stable formation of the Al 2O3-riched layer,which is benfeicial to improve the oxidation properties.     

含BaO,Na2O渣系渣钢间硫平衡研究

在钼丝炉上进行了含BaO,Na2O精炼渣系渣钢间流平衡实验。研究 结果表明,在传统精炼渣系中加入BaO,能够提高渣系的硫容量,Na2O对渣系的硫容量也有很大的影响,但稳定性不好。     

P2O5对转炉钢渣矿物结构的影响

依据实际转炉钢渣理化特性,以CaO-MgO-SiO2-Fe2O3四元渣系作为基础渣系,向该渣系中加入渣量1%～7%（质量分数）的P元素,使用SEM和EDS对合成渣系矿物结构进行表征与分析。结果表明：合成渣系主要由硅酸二钙、铁酸二钙及方镁石组成,其中磷元素主要以磷酸三钙的形式固溶于硅酸二钙中,在其他相中并未发现磷元素的存在;随着磷含量的增加,磷元素在硅酸二钙矿物中的含量随之增加,并可能出现独立的磷灰石相,这可为转炉钢渣在磷肥工业的应用研究提供参考。同时,由于磷加入量增多,CaO优先与[PO4]4-反应,早先存在的方镁石逐渐消失而溶入基质相。基质相2CaO·Fe2O3向CaO·MgO·Fe2O3发生转变,最后形成2MgO·Fe2O3,表明高磷含量有利于改善转炉钢渣的安定性能。     

Eu掺杂TiO_2纳米晶光致发光影响因素

为了寻找Ti O2∶Eu3+纳米晶的最佳制备工艺条件,采用溶胶-凝胶法制备了Ti O2∶Eu3+纳米晶,研究了Eu3+掺杂浓度、退火温度、Al3+的掺入等工艺参数对Ti O2∶Eu3+纳米晶发射光谱的影响.利用PL、PLE对样品进行了表征.结果表明用468 nm激发光源激发Ti O2∶Eu3+纳米晶时,样品显示出强红光发射,对应于Eu3+粒子的5D0→7F2超灵敏跃迁;且荧光强度随着Eu3+掺杂浓度和退火温度的升高先增强后减弱;700℃退火的样品红光发射强度达到最强,Eu3+的最佳掺杂浓度为0.8%mol;Al3+的掺入可以提高Eu3+的红光发射强度,采用钛酸正四丁脂∶异丙醇∶冰乙酸∶水=1∶4∶4∶2制备出的Ti O2:Eu3+纳米晶的红光发射光谱最强.     

TiO_2和Cr_2O_3复合晶核剂对微晶玻璃晶化行为的影响

通过差热分析、X射线衍射分析、偏光显微镜和扫描电镜观察等测试方法 ,研究了TiO2 和Cr2 O3作晶核剂对金属尾矿微晶玻璃晶化行为的影响 .研究表明 :Cr2 O3 和TiO2 复合晶核剂能有效地促进CaO -MgO -Al2 O3-SiO2 系统玻璃在较低温度下即开始晶化 ,且形成以透辉石为主晶相的微晶玻璃 ,晶核剂质量浓度不同对玻璃析晶的影响不同 .     

外加Al2O3颗粒对Ti-Al-TiO2系合成产物微观结构的影响

Ti-Al-TiO2体系外加不同含量的Al2O3颗粒获得了Al2O3／TiAl基复合材料,研究了产物的相组成及微观组织。结果表明：Al2O3颗粒多分布在基体晶界处。随外加Al2O3含量的增大,晶粒变小,但增强相颗粒团聚严重。外加Al2O3量存在一个临界值。含量过高,易造成结构疏松,不致密,形成大的气孔,且由于TiO2的活化作用,会造成外加的Al2O3颗粒烧结呈板状联结分布;含量较低,颗粒与界面的结合不够紧凑,但颗粒的结晶度较好。     

CaO-Al_2O_3-SiO_2系统微晶玻璃晶化行为的研究

以CaO Al2 O3 SiO2 系统为基础玻璃 ,以粉煤灰为主要原料制得以透辉石 (CaO·MgO·2SiO2 )和钙黄长石 (2CaO·Al2 O3 ·SiO2 )、霞石 (NaAlSiO4 )为主晶相的微晶玻璃。用DTA、XRD和SEM等现代测试方法 ,研究了Fe2 O3 ,TiO2 ,Cr2 O3 对粉煤灰玻璃的晶化行为的影响。结果表明 :Fe2 O3 有利于形成尖晶石型MgFe2 O4 晶核剂 ,从而促进玻璃的微晶化。Cr2 O3 、TiO2 均是有效的晶核剂     

K2Ti2O5对汽车尾气中碳烟的催化氧化性能研究

通过溶胶凝胶法制备了K2Ti2O5催化剂,并利用XRD,SEM,BET等方法进行了表征。利用程序升温反应对K2Ti2O5的碳烟催化氧化性能进行了研究。结果表明,K2Ti2O5具有一定的碳烟催化氧化活性。同时,一定量的NOx有助于K2Ti2O5的催化氧化活性,说明K2Ti2O5是一种潜在的可同时去除NOx和碳烟的新型催化剂。由于K2Ti2O5对碳烟具有较高的催化氧化活性、较好的抗水性和低廉的价格,因此是一种具有较好发展前景的汽车尾气净化催化剂。     

Al2O3/(W, Ti)C纳米复合陶瓷材料的力学性能与强韧化机理

采用纳米和亚微米级的α-Al₂O₃,以及微米级的(W,Ti)C粉体为原料,制备了Al₂O₃/(W,Ti)C纳米复合陶瓷材料.在基体Al₂O₃含有体积分数为11%的纳米Al₂O₃时复合材料的抗弯强度和断裂韧性达到最优,其抗弯强度、断裂韧性和硬度分别为840MPa,6.55MPa·m^1/2和20.1GPa.TEM实验表明,纳米颗粒的加入明显抑止了基体晶粒的长大,形成了典型的骨架结构,材料的断裂方式为沿晶断裂和穿晶断裂的混合.内晶型和晶间型第二相颗粒产生的残余应力场、断裂模式的改变和晶粒细化强化促进了复合材料抗弯强度和断裂韧性的提高.