Fe3O4/SiO2/Bi2WO6磁性复合光催化剂的制备及其光催化性能

钨酸铋(Bi₂WO₆),结构最简单的Aurivillius相化合物,是近期受到研究者关注的新型光催化材料。然而,光催化剂粉末在反应介质中难被回收,工业化应用成本较高。本文用三步方法合成了可回收的Fe₃O₄/SiO₂/Bi₂WO₆磁性复合光催化剂,通过溶剂热法合成具有磁性的Fe₃O₄,用溶胶凝胶法在Fe₃O₄表面覆盖SiO₂层,后将磁性颗粒与Bi₂WO₆纳米片相结合。光催化剂的形貌结构及性能通过XRD、SEM、PL、UV-vis进行表征测试。结果表明,直径约500 nm的Fe₃O₄微球附着在边长约500 nm的Bi₂WO₆纳米片的表面,SiO₂在两者之间起到了粘连作用。光催化剂Fe₃O₄/SiO₂/Bi₂WO₆对于罗丹明B的光降解活性较好,且有一定磁性,可以通过外加磁场将其从溶液中分离,有较大的应用潜力。     

Fe2O3-CaO-TiO2 体系下铁酸钙的合成过程及TiO2 和CaTiO3 的影响

为了确定高钛型钒钛磁铁矿烧结过程中铁酸钙的生成是受TiO₂还是TiO₂和CaO形成的CaTiO₃影响,首先利用Fe₂O₃和CaO的纯试剂合成了铁酸钙,并研究了TiO₂和CaTiO₃对钛铁酸钙 （FCT） 形成的影响。在Factsage 7.0软件进行热力学计算的基础上,通过在空气气氛下进行烧结,获得了在1023~1423 K温度范围内、不同烧结时间的不同样品。通过X射线衍射和扫描电镜-能谱分析等表征手段,对烧结样品的物相转变和微观结构变化进行了表征。发现FCT的形成过程主要分为2个阶段：前一阶段为1023~1223 K温度范围内Fe₂O₃与CaO之间的反应,合成产物为Ca₂Fe₂O₅,反应方程式为“Fe₂O₃(s)+ 2CaO(s)= Ca₂Fe₂O₅(s)”;后一阶段为1223~1423 K温度范围内Ca₂Fe₂O₅和Fe₂O₃的反应,主要产物为CaFe₂O₄,反应为“Ca₂Fe₂O₅(s)+ Fe₂O₃(s)= 2CaFe₂O₄(s)”,该阶段尤其是温度为1423 K时,反应速率显著加快,随温度的升高CaTiO₃显著增加。然而,Ti元素在铁酸钙中的固溶很难实现,TiO₂与铁酸钙之间的反应不是形成FCT的有效途径。随着保温时间的延长,CaTiO₃和FCT相界中Fe元素含量增加。FCT主要是通过Fe组分在CaTiO₃中固溶形成的,主要反应是“Fe₂O₃+CaTiO₃(s)=FCT(s)”。     

La2O3掺杂氧化铝气凝胶的制备与耐温性能研究

以仲丁醇铝为前驱体,采用溶胶-凝胶法结合丙酮-苯胺原位生成水技术,通过乙醇超临界干燥,制备出不同含量(1.5 mol%~12 mol%)La₂O₃掺杂的氧化铝气凝胶。采用电子扫描电镜(SEM)、透射电子显微镜(TEM)、X线衍射仪(XRD)、N₂吸附分析仪等仪器表征了La₂O₃掺杂对氧化铝气凝胶的微结构和耐温性能的影响。结果表明：La₂O₃的引入使氧化铝气凝胶的形貌由球状颗粒向大的片状结构转变。适量的La₂O₃掺杂能提高氧化铝气凝胶的比表面积,9 mol% La₂O₃掺杂的氧化铝气凝胶比表面积最大。通过La₂O₃掺杂,能够抑制氧化铝晶粒在高温下的生长和α-Al₂O₃的相变,提高氧化铝气凝胶的耐温性能。1200℃热处理后,La₂O₃掺杂的氧化铝气凝胶仍维持在θ-Al₂O₃,比表面积为86.5 m₂/g,高于未掺杂的氧化铝气凝胶(46 m₂/g)。     

溶胶-凝胶法制备YAG颗粒及在电接触材料中的应用

以硝酸钇(Y(NO₃)₃6H₂O)、硝酸铝(Al(NO₃)₃9H₂O)为主要原料,六次甲基四胺作为催化剂,采用溶胶-凝胶法合成Y₃Al₅O₁₂(YAG)纳米颗粒,并以YAG颗粒为第二相增强材料,通过粉末冶金工艺制备Ag/YAG电接触复合材料;采用X-射线衍射仪(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),傅里叶红外光谱(FT-IR)、硬度计、电导率仪等方法对其进行表征。结果表明：在水浴温度为50℃的条件下成功采用sol-gel法合成YAG纳米颗粒,物相纯度高;随着催化剂六次甲基四胺加入量的增加,YAG粉末颗粒粘连在一起,并出现大孔;以YAG为第二相增强材料制备的Ag/YAG电接触复合片材电阻率较低,维氏硬度大于80。     

环境障涂层用纳米结构Yb2SiO5粉体喂料的制备与表征

纳米结构稀土硅酸盐涂层被认为是未来新型环境障涂层的发展方向,其中 Yb₂ SiO₅ 由于与中间层莫来石的热物性能匹配良好、优异的抗水氧腐蚀能力成为非常有发展前景的环境障涂层面层候选材料。 从材料制备的角度出发, 探索纳米结构 Yb₂ SiO₅ 喂料制备工艺并对喂料进行物相、组织结构和性能表征。 采用喷雾造粒加固相烧结的方法制备了纳米结构 Yb₂ SiO₅ 喷涂粉体喂料,探索了制备高纯度 Yb₂ SiO₅ 的固相烧结工艺,后续通过等离子处理改善粉体喂料的喷涂性能。 借助 X 射线衍射仪研究了粉体喂料的物相,采用扫描电镜、透射电镜研究了粉体喂料的形貌与微观结构。 结果显示,固相烧结工艺采用在 1500 ℃下保温 4 h,再将得到的粉体喂料等离子处理可得到高纯度的 Yb₂ SiO₅ 喷涂粉体喂料,等离子处理之后的喂料为纳米结构,喂料粒度分布均符合等离子喷涂要求,喂料具有良好的流动性和致密性。     

基于磁过滤技术的热障涂层表面Al2O3 覆盖层抗CMAS腐蚀性能

为了提高热障涂层（TBC）的抗沉积物（主要成分为CaO、MgO、Al₂O₃和SiO₂,简称CMAS）腐蚀性能,采用磁过滤阴极真空电弧（FCVA）技术在TBC表面上制备了致密的Al₂O₃覆盖层,比较和分析了Al₂O₃改性TBC和沉积态TBC的润湿行为和抗CMAS腐蚀性能。结果表明：使用FCVA技术制备Al₂O₃覆盖层的过程对7%（质量分数）氧化钇稳定的氧化锆（7YSZ）相的结构无明显影响,且经Al₂O₃改性的TBC综合性能均优于沉积态TBC。在1250 ℃、CMAS腐蚀条件下,Al₂O₃覆盖层有效地限制了熔融CMAS在TBC表面上的扩散行为。同时,Al₂O₃填充了7YSZ柱状晶之间的间隔并且阻碍了熔融CMAS的渗透,证明了FCVA可作为一种制备Al₂O₃涂层的新方法以提高TBC的抗CMAS腐蚀性能,且Al₂O₃涂层及其制备过程对TBC的热震性能均无消极影响。     

溶胶凝胶法制备LaMn1-XVXO3及光催化氧化性能

以La(NO₃)₂、MnC₄H₆O₂、柠檬酸和乙二醇(EG)为主要原料,NH₄VO₃为掺杂试剂,采用溶胶凝胶法制备LaMnO₃和LaMn_1-XV_XO₃粉体。采用XRD进行晶体结构表征;采用甲基橙(MO)模拟污水,进行光催化降解实验。研究了煅烧温度、催化剂用量和掺杂量对光催化氧化降解率的影响,讨论MO降解的动力学规律。结果表明700-900 ℃煅烧温度不影响LaMnO₃晶体结构和光催化氧化降解率;掺杂量影响LaMn_1-XV_XO₃晶体结构,光催化氧化降解率随着掺杂量增加而呈下降趋势;光催化氧化实验中,LaMn_1-XV_XO₃粉体效果高于LaMnO₃,两者均符合一级动力学方程。     

ZrO2纳米颗粒对Al-12.5%Si合金PEO陶瓷层性能的影响

采用外加ZrO₂纳米颗粒的电解液体系在Al-12.5%Si合金表面制备ZrO₂- Al₂O₃- SiO₂三相PEO陶瓷层。利用SEM和XRD对陶瓷层微观结构和物相进行分析,并对其隔热及热冲击性能进行测试。结果表明：ZrO₂纳米颗粒显著提高了膜层的致密度和结合性,并有效减弱了Si元素对PEO成膜的抑制作用,提高了成膜速率;三相PEO陶瓷层的主要物相为SiO₂及高温稳定相α-Al₂O₃和c-ZrO₂,其独特的微结构和成分致使ZrO₂纳米颗粒改性的陶瓷层具有良好的热防护性能和热冲击性能。     

高容量锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2的制备与工艺优化

采用氢氧化物共沉淀法合成前驱体Ni_0.5Cc_0.2Mn_0.3H(OH)₂,进一步用高温固相法与锂源共混煅烧得到LiNi_0.5Co_0.2Mn_0.3O₂。初步探讨了前驱体与锂源在高温煅烧过程中的质量变化及煅烧工艺对材料结构和性能的影响。热重分析(TGA)表明在煅烧过程中750℃后材料质量几乎没有变化。X射线衍射(XRD)对750℃-900℃的材料进行结构分析,结果表明所有材料具有良好的α-NaFeO₂层状结构和较小的阳离子混排度。扫描电镜(SEM)分析表明材料具有表面光滑,分布均匀的球形结构。横流充放电测试结果表明在850℃煅烧的材料具有最好的电学性能,在0.2C,2.5-4.6V测试条件下,其具有193.7mAh/g的首次放电容量,循环30次后的容量保持率为94.2%,并且具有最好的倍率性能。     

Ba(Mg1/3Ta2/3)O3热障涂层的制备及抗热震性能研究

本文以BaCO₃、MgO、Ta₂O₅为原料,采用固相反应法合成了Ba(Mg_1/3Ta_2/3)O₃(简称BMT)陶瓷粉末,利用大气等离子喷涂技术制备了BMT/YSZ双层陶瓷涂层。利用XRD、SEM和金相显微镜检测了BMT粉体及涂层的物相组成和显微结构。采用水淬法考核了涂层的抗热震性能。结果表明：1450℃下煅烧4h可合成出具有复合钙钛矿结构的BMT粉末,粉末具有良好的高温相结构稳定性。等离子喷涂制备的BMT/YSZ涂层组织致密,涂层系统中各界面结合紧密。涂层在室温至1150℃间热震9次后发生片状剥落,剥落位置位于BMT层间,BMT材料低的断裂韧性和第二相Ba₃Ta₅O₁₅的存在是导致涂层失效的主要原因。     

Characterisation of the coke formed during metal dusting of iron in CO-H2-H2O gas mixtures

Carbon deposits formed on the surface of iron samples during carburisation at 700 °C in a gas mixture of 75%CO-24.81%H₂-0.19%H₂O were characterised by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). Cross-section observation of the iron sample by light optical microscopy revealed the formation of cementite after only 10 min reaction, together with a thin layer of graphite. After 4 h reaction, a thick coke layer was formed on top of the cementite surface. SEM surface observation indicated the formation of filamentous carbon in the coke layer. Further analysis of the coke by XRD and Mössbauer showed the presence of mainly Fe₃C and small amount of Fe₂C but no metallic iron in the carbon deposit. TEM analysis of the coke detected very convoluted filaments with iron-containing particles at the tip or along their length. These particles were identified to be cementite by selected area diffraction. Carbon deposits produced at the same temperature but with other gas compositions were also analysed by using XRD. It was found that with a low content of CO, e.g. 5%, both α-Fe and Fe₃C were detected in the coke. Increasing CO content to more than 30%, iron carbide was the only iron-containing phase.     

Synthesis of lanthanum carbonate nanoparticles via sonochemical method for preparation of lanthanum hydroxide and lanthanum oxide nanoparticles

Lanthanum carbonate nanoparticles were synthesized from the reaction of lanthanum acetate and Na₂CO₃ under sonication via sonochemical method. Lanthanum hydroxide nanoparticles were prepared by facial hydrothermal processing from the resulted product at 110 °C for 24 h. The role of surfactant, calcination temperature and sonication time were investigated on the morphology and particle size of the products. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and Fourier transform infrared (FT-IR) spectra. La₂O₃ nanoparticles were obtained by calcinations of the nanoparticles of lanthanum carbonate at 600 °C.     

A literature review and test: Structure and physicochemical properties of spinel LiMn2O4 synthesized by different temperatures for lithium ion battery

A series of LiMn₂O₄ spinel was prepared by adipic acid-assisted sol–gel method at different temperatures. The structure and physicochemical properties of spinel LiMn₂O₄ synthesized by different temperatures were investigated by differential thermal analysis (DTA) and thermogravimetery (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron micrographs (SEM), inductively coupled plasma-mass spectroscopy (ICP-MS), galvanostatic charge–discharge test, and cyclic voltammetry (CV), respectively. TG–DTA shows that the weight loss occurs in four temperature regions during the synthesis of LiMn₂O₄. XRD indicates that the sintering temperature affects the formation of spinel phase, and prominent LiMn₂O₄ spinel powder with smaller atom location confusion forms about 800 °C. XPS reveals that the manganese oxidation state in spinel lithium manganese oxide synthesized at different temperatures is between +3 and +4. SEM shows that LiMn₂O₄ spinel synthesized at 800 °C has the uniform, nearly cubic structure morphology with narrow size distribution. ICP-MS indicates that the average chemical valence of Mn element of LiMn₂O₄ synthesized at 800 °C is the most close to 3.5 among the samples synthesized at different temperatures. CV illustrates that the LiMn₂O₄ synthesized at 800 °C has the best electrochemical activity. Charge–discharge test explains that the capacity retention sintered at 350, 700 and 800 °C over the first 50 cycles is 93.6%, 86.1% and 85.2%, respectively, but the discharge capacity at the 50th cycle is 82.2, 104.8 and 110.8 mAh g⁻¹, respectively.     

Carburization of iron using CO−H<Subscript>2</Subscript> gas mixture

Iron carbides formed on the surface of iron and iron oxide samples at 640 °C in a gas mixture of CO?H₂ were characterized by scanning electron microscopy (SEM), Mössbauer spectroscopy, X-ray diffraction patterns (XRD), and by measuring mass change. The Fe₃C amount of the samples has been quantitatively evaluated by the weight change during carburization. While Fe₂O₃ powder was mostly completed to Fe₃C in the early stage, within 5 min after reduction reactions, the conversion of Fe powder sample to Fe₃C (iron carbide) was almost finished after 10 min. The carburization rate of a Fe sheet was very slow and intermediate products (Fe₂C, Fe₅C₂) were observed. This phenomenon is largely due to the difficulty of carbon diffusion into its dense surface. It was found that the carburization rate was affected by change of surface conditions and surface area by reduction, degradation, and cracks at high temperature. This study should help provide a fundamental understanding of carburization in the field of iron-making and suggest a direction for its further development.     

载体中ZrO2/Al2O3比对Pt/ZrO2-Al2O3催化剂性能的影响

相比汽油车而言,柴油车具有高效、低油耗的优势已得到广泛应用。本实验以ZrO₂作为改性剂,探究了ZrO₂与Al₂O₃的质量比对催化剂的影响。研究结果表明：随着ZrO₂的加入,Pt粒子先减小后增大;Pt粒子与载体的交互作用先增大后减小。活性实验数据分析表明,ZrO₂的最佳添加量为40 wt%,CO和C₃H₆完全氧化温度分别降低20 _oC 、25 _oC。贵金属在催化剂的分散度以及贵金属与载体的相互作用随着ZrO₂与Al₂O₃质量比的变化而变化。Pt粒子越小,其与载体的交互作用越强,这表明催化剂性能越强。     

Preparation and characterization of nanostructured Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> and Sn<Subscript>0.5</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript>

Nanostructured Bi₂Se₃ and Sn_0.5-Bi₂Se₃ were successfully synthesized by hydrothermal coreduction from SnCl₂·H₂O and the oxides of Bi and Se. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM). Bi₂Se₃ powders obtained at 180°C and 150°C consist of hexagonal flakes of 50–150 nm in side length and nanorods of 30–100 nm in diameter and more than 1 μm in length. The product obtained at 120°C is composed of thin irregular nanosheets with a size of 100–200 nm and several nanometers in thickness. The major phase of Sn_0.5-Bi₂Se₃ synthesized at 180°C is similar to that of Bi₂Se₃. Sn_0.5-Bi₂Se₃ powders are primarily nanorod structures, but small amount of powders demonstrate irregular morphologies.     

Effects of sulfur pressure on the sulfidation behavior of 310 stainless steel

High-temperature sulfidation behavior of 310 stainless steel was studied over the temperature range of 700–900°C above a pure sulfur pool with the sulfurvapor range of 10^–4–10^–1 atm. The corrosion kinetics followed the parabolic rate law in all cases. The corrosion rates increased with increasing temperature and sulfur pressure. The scales formed on 310 stainless steel were complex and multilayered. The outer scale consisted of iron sulfide (with dissolved Cr), (Fe, Ni)₉S₈ and chromium sulfides (Cr₂S₃ and Cr₃S₄ with dissolved Fe), while the inner layer was a heterophasic mixture of Cr₂S₃, Cr₃S₄, NiCr₂S₄, and Fe₁–_xS. Platinum markers were found to be located at the interface between the inner and outer scales, suggesting that the outer scale grew by the outward transport of cations (Fe, Ni, and Cr), and the inner scale grew by the inward transport of sulfur. The formation of Cr₂S₃, Cr₃S₄, and NiCr₂S₄ partly blocked the transport of iron through the inner scale, resulting in a reduction of the corrosion rates as compared with the results in the literature.     

Synthesis of lanthanum hydroxide and lanthanum oxide nanoparticles by sonochemical method

In this work lanthanum hydroxide nanoparticles were synthesized by sonochemical method. La₂O₃ nanoparticles were obtained after calcination of the La(OH)₃ nanoparticles precursor in air at 600 °C for 2 h. The effect of some parameters such as concentration of precursors, pulse time of sonication, time of sonication, and addition of PEG as surfactant on the morphology and the particle size were studied. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS) and Fourier transform infrared (FT-IR) spectra.     

Preparation and characterization of nano TiO2/micron Cr2O3 composite particles

Nano-TiO₂/micro-size Cr₂O₃ composite particles were first prepared by hydrolysis of Ti(OBu)₄ in an abundant acidic aqueous solution without calcinations at room temperature. XPS analysis shows that the element C, O, Ti and Sn existed on the surfaces of the composite particles. Observation by field emission scanning electronic microscope shows TiO₂ particles of 10-15 nm covers on Cr₂O₃ powder surfaces to form nanometer/micron composite particles. UV-vis spectra show a red shift of the absorption edge and a significant increase of absorption intensity in the visible region. These results confirm that TiO₂ of anatase type can be synthesized on the surface of Cr₂O₃.     

Preparation of ultra-fine FeNiMnO<Subscript>4</Subscript> powders and ceramics by a solid-state coordination reaction

A mixed oxalate FeNiMn(C₂O₄)₃·nH₂O, a coordination compound, was synthesized by milling a mixture of ferrous iron chloride, nickel acetate, manganese acetate, and oxalic acid at room temperature. A spinel-structured FeNiMnO₄ powder with high sintering activity and chemical homogeneity was obtained by calcining the mixed oxalate in air at 800°C for 2 h. Dense FeNiMnO₄ ceramics with a relative density of ∼98% were achieved by sintering powder compacts at a lower temperature of 1100°C for 5 h. The specific resistivityρ _25°C and the thermal constant B_25/85°C were 4382 Ω·cm and 3373 K, respectively. The aging coefficient ΔR/R(%) of the ceramics after annealing at 150°C for 500 h was 0.6%.