热轧低碳钢卷取后冷却过程中三次氧化铁皮结构转变行为

采用SEM和热模拟试验机研究在卷取后连续冷却条件下、不同的卷取温度和不同冷却速度条件下低碳钢三次氧化铁皮结构转变行为。研究结果表明:在连续冷却转变过程中,FeO层的转变均遵循"C"曲线规律,400~500℃为FeO共析反应的"鼻温"范围,在这个温度区间内,以较小的冷速冷却到室温可以得到以共析组织Fe3O4和单质Fe为主的氧化铁皮结构,较快冷速则会抑制共析反应的发生;当冷速达到25℃/min时,FeO共析转变进程被抑制,氧化铁皮结构以先共析Fe3O4为主。结合连续冷却结构转变曲线,通过控制卷取温度和冷却速率,可以控制FeO的共析反应进程,从而达到精确控制氧化铁皮结构目的。     

X80管线钢的高温氧化行为

利用热重法对X80管线钢高温氧化行为进行系统研究,分析不同温度下氧化增重和氧化铁皮形貌演变规律及合金元素在氧化层与钢基体界面处的分布规律.实验结果表明:700~1200℃范围内,X80钢氧化增重曲线呈现抛物线规律.此外,氧化铁皮厚度随温度升高而增加,特别是当温度高于800℃时,由于金属基体存在相变,氧化铁皮厚度急剧增加.高温条件下X80钢氧化铁皮为典型三层结构,外层为极薄的Fe₂O₃,中间层为Fe₃O₄,内层为粗大柱状晶FeO,并在靠近钢基体处形成一层晶粒细小的内氧化层,内氧化层阻碍了铁氧离子的相互扩散,提高了X80管线钢的高温耐蚀性.     

改质钢渣中铁/磷富集相形核与长大行为研究

回收钢渣中的铁（Fe）和磷（P）,不仅可以减轻钢渣堆积带来的环境负担,而且是钢铁工业发展循环经济、实现可持续发展的必由之路。本文旨在通过研究B₂O₃改质钢渣中富铁相（Fe₃O₄）和富磷相（Ca₁₀P₆O₂₅）的结晶动力学规律确定Fe₃O₄与Ca₁₀P₆O₂₅晶体可控生长的温度制度。本研究采用高温激光共聚焦扫描显微镜（CLSM）在线观测CaO–SiO₂–FeO–P₂O₅–B₂O₃熔体的结晶行为,使用经典的结晶动力学理论计算Fe₃O₄与Ca₁₀P₆O₂₅晶体的形核和长大速率。研究结果表明,CaO–SiO₂–FeO–P₂O₅–B₂O₃熔体在冷却过程中初晶相Fe₃O₄析出温度范围为1300–1150°C,棒状的第二相Ca₁₀P₆O₂₅在1150–1000°C温度区间内析出,且Fe₃O₄相的结晶能力大于Ca₁₀P₆O₂₅相。综合考虑Fe₃O₄相与Ca₁₀P₆O₂₅相的形核与长大速率,最终确定两相选择性结晶长大的最佳温度区间为(1055 ± 25)°C,即在1080–1030°C温度范围内对CaO–SiO₂–FeO–P₂O₅–B₂O₃熔体进行缓慢冷却有利于Fe₃O₄与Ca₁₀P₆O₂₅晶体的结晶长大,从而为后续从渣中选择性分离Fe₃O₄相与Ca₁₀P₆O₂₅相创造了必要条件。     

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe₂O₃→Fe₃O₄, Fe₃O₄→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO₂ content in the Fe₂O₃→Fe₃O₄ stage but is substantially greater than the CO₂ contents in the Fe₃O₄→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and Fe_xO_y reduction by CO, which are the restrictive step in the last two stages, require further study.     

碳元素及加热温度对SCM435钢氧化行为的影响

随着汽车工业的高速发展,高强度螺栓钢作为汽车连接件的母材,需求量与日俱增。热轧过程中产生的氧化铁皮是影响高强度螺栓钢产品质量的重要因素。本文以SCM435钢为研究对象,利用扫描电镜、XRD和拉伸实验等检测手段,重点研究碳含量和开轧温度对SCM435钢表面氧化行为的影响规律。研究结果表明,含碳量较低时氧化铁皮分布均匀,主要由Fe₂O₃组成;含碳量较高时氧化铁皮主要由Fe₃O₄组成,分布不均匀,甚至会出现断带和裂纹。含碳量较高的螺栓钢更易产生较薄的氧化铁皮,加热过程中,氧化铁皮厚度随着加热温度的升高而降低;对于含碳质量分数0.1%的螺栓钢,存在临界温度,使氧化铁皮的厚度随着温度的升高先增加后减小。     

Ni系低温钢的高温氧化行为研究

为研究Ni系低温钢的高温氧化行为,利用Setsys Evolution型高温同步热分析仪对Fe-3.5Ni和Fe-9Ni钢在700~1200℃的氧化行为进行了研究,采用电子探针(EPMA)、场发射扫描电镜(SEM)和X射线衍射(XRD)等手段表征了氧化物微观形貌和物相组成.结果表明:700~1200℃条件下氧化2h后,Fe-3.5Ni钢和Fe-9Ni钢的氧化增重曲线规律相似,相同氧化温度条件下,单位面积Fe-9Ni钢的增重量低于Fe-3.5Ni钢.随氧化温度的升高,试样表面依次出现团絮状、晶须状和不规则多边形状Fe₂O₃.氧化分为内氧化和外氧化,内、外氧化层厚度随氧化温度的提高逐渐增加,且900℃是两种钢外氧化层厚度发生突变的临界温度.内氧化层由FeNi₃和混合物(FeO+Fe₃O₄)组成,外氧化层由Fe₂O₃,Fe₃O₄和FeO组成,且外氧化层内包裹着尖晶石相NiFe₂O₄;随着Ni含量增加,NiFe₂O₄增多并形成连续的薄带.     

阶梯热还原法制备Fe3O4/rGO复合膜

先用溶液共混法获得Fe₃O₄纳米颗粒与氧化石墨烯（GO）混合溶液, 再通过阶梯热还原过程（从室温逐渐升至160 ℃）制备Fe₃O₄和还原氧化石墨烯（rGO）复合膜， 并用X射线衍射仪、 Fourier变换红外光谱和扫描电子显微镜表征不同Fe₃O₄质量分数的Fe₃O₄/rGO复合膜的结构和形貌, 用矢量网络分析仪测试复合膜的电磁参数. 实验结果表明, 当Fe₃O₄质量分数为40％时, 复合膜的吸波效能为17.30 dB, 频率为10.72 GHz, 厚度为2 mm, 低于-10 dB[KG*8]的有效吸收带宽为3.28 GHz.     

阶梯热还原法制备Fe3O4/rGO复合膜

先用溶液共混法获得Fe₃O₄纳米颗粒与氧化石墨烯（GO）混合溶液, 再通过阶梯热还原过程（从室温逐渐升至160 ℃）制备Fe₃O₄和还原氧化石墨烯（rGO）复合膜, 并用X射线衍射仪、 Fourier变换红外光谱和扫描电子显微镜表征不同Fe₃O₄质量分数的Fe₃O₄/rGO复合膜的结构和形貌, 用矢量网络分析仪测试复合膜的电磁参数. 实验结果表明, 当Fe₃O₄质量分数为40％时, 复合膜的吸波效能为17.30 dB, 频率为10.72 GHz, 厚度为2 mm, 低于-10 dB[KG*8]的有效吸收带宽为3.28 GHz.     

连续还原法制备Au/Fe3O4纳米复合粒子

采用共沉淀法制备20～40nm的Fe₃O₄颗粒。在Fe₃O₄悬浮液中分别利用柠檬酸钠单独作为还原剂、四羟甲基氯化磷（THPC）和抗坏血酸共同作为还原剂还原HAuCl₄,生成10～90nm的Au纳米颗粒,形成Au/Fe₃O₄复合颗粒。通过透射电子显微镜和紫外分光光度计对Au/Fe₃O₄进行表征,研究还原剂种类对Au/Fe₃O₄粒径、形貌和分散性的影响,结果表明：柠檬酸钠为还原剂时,生成Au纳米颗粒的反应主要在Fe₃O₄纳米颗粒表面进行,Au纳米颗粒的负载量随柠檬酸钠用量增加而减少,粒径在28.08～77.71nm之间;THPC和抗坏血酸共同作为还原剂时,先在Fe₃O₄ 纳米颗粒表面生成THPC-Au,加入抗坏血酸后生成Au纳米颗粒,粒径在71.44～153.2nm之间。     

Isothermal reduction kinetics and mineral phase of chromium-bearing vanadium-titanium sinter reduced with CO gas at 873-1273 K

Reduction of chromium-bearing vanadium-titanium sinter (CVTS) was studied under simulated conditions of a blast furnace, and thermodynamics and kinetics were theoretically analyzed. Reduction kinetics of CVTS at different temperatures was evaluated using a shrinking unreacted core model. The microstructure, mineral phase, and variation of the sinter during reduction were observed by X-ray diffraction, scanning electron microscopy, and metallographic microscopy. Results indicate that porosity of CVTS increased with temperature. Meanwhile, the reduction degree of the sinter improved with the reduction rate. Reduction of the sinter was controlled by a chemical reaction at the initial stage and inner diffusion at the final stage. Activation energies measured 29.22-99.69 kJ/mol. Phase transformations in CVTS reduction are as follows:Fe₂O₃→Fe₃O₄→FeO→Fe; Fe₂TiO₅→Fe₂TiO₄→FeTiO₃; FeO·V₂O₃→V₂O₃; FeO·Cr₂O₃→Cr₂O₃.     

Fe3O4纳米粒子添加剂对成形润滑油摩擦性能的影响

利用纳米级Fe₃O₄作为成形润滑油的添加剂,采用表面活性剂对纳米粒子进行表面改性,利用超声分散器使Fe₃O₄纳米粒子均匀稳定地分散在润滑油溶液中。利用四球摩擦磨损试验机对配制出的纳米润滑液进行摩擦性能测试。研究结果表明,不同粒径的纳米粒子对润滑剂的油膜强度影响较大,采用20 nm Fe₃O₄粒子配制润滑剂时,可有效提高润滑剂的油膜强度;当纳米粒子质量分数达到8%时,摩擦系数有较大程度的降低,磨斑直径减小。这表明一定质量分数与尺寸的Fe₃O₄纳米粒子可有效提高润滑油的摩擦性能。     

Synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> magnetic composite nanoparticles by a one-pot process

Fe₃O₄@SiO₂ core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe₃O₄@SiO₂ core–shell structures from prepared Fe₃O₄ nanoparticles. The properties of the Fe₃O₄ and Fe₃O₄@SiO₂ composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe₃O₄ particles were approximately 12 nm in size, and the thickness of the SiO₂ coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe₃O₄@SiO₂ powder (34.85 A·m2·kg–1) was markedly lower than that of the Fe₃O₄ powder (79.55 A·m2·kg–1), which demonstrates that Fe₃O₄ was successfully wrapped by SiO₂. The Fe₃O₄@SiO₂ composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.     

Fe3O4/Ag复合纳米颗粒的制备及其抑菌性能研究

首先用水热法制备了Fe₃O₄纳米球,然后以制备的磁性Fe₃O₄纳米粒子为磁核,在高温高压反应釜中与葡萄糖反应,使其表面包覆一层聚糖,利用聚糖的还原性,让包覆后的粒子与AgNO₃反应,制备出Fe₃O₄/Ag纳米复合粒子。用透射电镜（TEM）、X射线衍射仪（XRD）对所制备的材料的形貌和结构进行了表征。通过抑菌实验的测定,结果表明Fe₃O₄/Ag复合材料具有良好的抑菌活性。     

Fe3O4@CTAC粒子的制备及抗菌性能研究

采用溶剂热法合成了分散性良好的Fe₃O₄粒子,然后将油酸修饰到Fe₃O₄粒子表面,再通过疏水作用进行十六烷基三甲基氯化铵(CTAC)包覆,得到Fe₃O₄@CTAC粒子。采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)、Zeta电位和振动样品磁强计(VSM)对Fe₃O₄@CTAC粒子进行了表征,结果表明：Fe₃O₄粒子表面包覆CTAC后粒径无明显变化,并且仍保持良好的单分散性;Fe₃O₄@CTAC粒子具有超顺磁性和良好的磁响应性能;Fe₃O₄@CTAC粒子的Zeta电位较高,分散体系具有较好的稳定性。对Fe₃O₄@CTAC粒子进行了抗菌性能及磁分离去除菌体测试,结果显示：当Fe₃O_...     

Kinetic analysis of iron ore powder reaction with hydrogen–carbon monoxide

Iron ore powder was isothermally reduced at 1023–1373 Kwith hydrogen/carbon monoxide gas mixture (from 0vol%H₂/100vol% CO to 100vol%H₂/0vol%CO). Results indicated that the whole reduction process could be divided into two parts that proceed in series. The first part represents a double-step reduction (Fe₂O₃→Fe₃O₄→FeO), in which the kinetic condition is more feasible compared with that in the second part representing a single-step ...     

纳米Fe3O4覆盖对沉积物-水界面钴和镍的吸附试验研究

为揭示纳米材料原位覆盖对表层沉积物重金属的影响规律,开展室内培养原位沉积物柱试验,利用微界面分析技术、高分辨率平衡式间隙水采集技术（HR-Peeper）和薄膜扩散梯度技术（DGT）,探究纳米Fe₃O₄原位覆盖对表层沉积物中Co、Ni释放的影响机制。试验结果表明:在纳米Fe₃O₄覆盖下沉积物pH值较对照组逐渐增大,Eh值先减小后增大;纳米Fe₃O₄覆盖可有效吸附间隙水中的溶解态Co和Ni,间隙水中的溶解态Co和Ni最大有效吸附率分别为27.07%及26.42%,有效影响深度分别为30 mm和10 mm;纳米Fe₃O₄覆盖有效抑制了沉积物中有效态Co和Ni向间隙水和上覆水扩散,沉积物中有效态Co和Ni含量分别降低了50.26%和15.31%。     

Control the growth of Fe3O4 on the surface of saponite and its redox effect on Cr(VI)

In this paper, Magnetite/Saponite(Fe₃O₄/Sap) composites were prepared by hydrothermal synthesis and coprecipitation. The prepared Fe3O4/sap composites had high purity and good crystallinity, and nano-Fe₃O₄was uniformly dispersed on the surface of saponite. Moreover, the removal efficiency of Fe₃O₄/Sap composites for Cr(VI) in water was evaluated. This study revealed the existence of abundant oxygen vacancies and hydroxyl groups on...     

Fe3O4负载纳米零价铁类Fenton法去除水中2,4-二氯苯酚

2,4-二氯苯酚(2,4-DCP)广泛用于工农业和医药等生产过程中,其泄漏和排放对水体、土壤及人类环境造成严重危害.文中首先用共沉淀法和液相还原法制成Fe₃O₄负载纳米零价铁(nZVI)复合材料(Fe₃O₄@n ZVI),然后将其用作类Fenton技术的催化剂,用于水中2,4-DCP的去除.考察了Fe₃O₄负载量、溶液pH值、H₂O₂浓度、Fe₃O₄@nZVI投加量、污染物浓度、温度等因素对2,4-DCP去除率的影响,并进行了动力学拟合分析;另外,还研究了Fe₃O₄@n ZVI的可回收利用性能.结果表明,在Fe₃O₄与n ZVI摩尔比为1∶1时,降低反应体系p H值、提高H₂O₂浓度、增加Fe₃O₄     

超顺磁性Fe3O4微粒的尺寸调控与磁性回收

以乙二醇为溶剂,通过温和的溶剂热法制备了具有不同颗粒尺寸大小的Fe₃O₄微米粒子.研究发现,通过调节反应体系中水、聚乙二醇-20000和铁离子的浓度,能有效控制Fe₃O₄的成核与生长,从而能实现对Fe₃O₄在较大颗粒尺寸范围内的有效调控.另外,相比小尺寸的Fe₃O₄,较大颗粒尺寸的超顺磁性粒子表现出更优良的磁性回收性能.由此可见,Fe₃O₄颗粒尺寸的有效调控对拓展其在纳米材料磁性回收中的应用具有非常重要的意义     

Fe2O3修饰CaSO4/Ben载氧体化学链燃烧反应特性

分别采用间歇式流化床反应器和热重分析仪进行多次循环实验及反应性能测试,研究了Fe2O3在化学链燃烧过程中对CaSO₄/Ben(膨润土)载氧体的催化作用,并对比Fe₂O₃不同添加量(质量分数)时CaSO₄/Ben载氧体与CO的反应活化能。结果表明,添加Fe₂O₃后CaSO₄/Ben载氧体的比表面积和孔容增加,还原反应速率提高,并使系统内维持较高浓度的CO₂;添加Fe₂O₃可抑制CaSO₄生成CaO和含硫气体的反应,提高CaSO₄/Ben载氧体循环反应的稳定性;Fe₂O₃的最佳添加量为w=15.0%,该添加量下CaSO₄/Ben载氧体与CO反应的活化能由88.72 kJ/mol降低至43.08 kJ/mol,反应活性显著提高。