L10 FePt Nanoparticles Processing with Applied Magnetic Field

Due to the strong magnetic anisotropy energy, the L1₀ FePt nanocrystals are considered as one of promising candidates for magnetic recording media with ultrahigh densities. The surfaces of Si and SiO₂ wafers have been covered by FePt nanoparticles (NPs) and heated at 600 °C for 1 h to form the L1₀ phase. Bonding of NPs with the SiO₂ surface in the presence of magnetic field during annealing process controls the L1₀ FePt NPs size and their uniform surface distribution. In the presence of perpendicular magnetic field to the surface, the size of NPs obtains up to 30 nm with coercivity of 5.8 kOe and in parallel magnetic field, the NPs size reaches to 45 nm with coercivity of 2.9 kOe. These results and the easy axis ordering of samples have been determined by energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer analyses.     

Monodisperse magnetic nanoparticles for theranostic applications

Effective medical care requires the concurrent monitoring of medical treatment. The combination of imaging and therapeutics allows a large degree of control over the treatment efficacy and is now commonly referred to as "theranostics". Magnetic nanoparticles (NPs) provide a unique nanoplatform for theranostic applications because of their biocompatibility, their responses to the external magnetic field, and their sizes which are comparable to that of functional biomolecules. Recent studies of magnetic NPs for both imaging and therapeutic applications have led to greater control over size, surface functionalization, magnetic properties, and specific binding capabilities of the NPs. The combination of the deep tissue penetration of the magnetic field and the ability of magnetic NPs to enhance magnetic resonance imaging sensitivity and magnetic heating efficiency makes magnetic NPs promising candidates for successful future theranostics. In this Account, we review recent advances in the synthesis of magnetic NPs for biomedical applications such as magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH). Our focus is on iron oxide (Fe(3)O(4)) NPs, gold-iron oxide (Au-Fe(3)O(4)) NPs, metallic iron (Fe) NPs, and Fe-based alloy NPs, such as iron-cobalt (FeCo) and iron-platinum (FePt) NPs. Because of the ease of fabrication and their approved clinical usage, Fe(3)O(4) NPs with controlled sizes and surface chemistry have been studied extensively for MRI and MFH applications. Porous hollow Fe(3)O(4) NPs are expected to have similar magnetic, chemical, and biological properties as the solid Fe(3)O(4) NPs, and their structures offer the additional opportunity to store and release drugs at a target. The Au-Fe(3)O(4) NPs combine both magnetically active Fe(3)O(4) and optically active Au within one nanostructure and are a promising NP platform for multimodal imaging and therapeutics. Metallic Fe and FeCo NPs offer the opportunity for probes with even higher magnetizations. However, metallic NPs are normally very reactive and are subject to fast oxidation in biological solutions. Once they are coated with a layer of polycrystalline Fe(3)O(4) or a graphitic shell, these metallic NPs are more stable and provide better contrast for MRI and more effective heating for MFH. FePt NPs are chemically more stable than Fe and FeCo NPs and have shown great potential as contrast agents for both MRI and X-ray computed tomography (CT) and as robust probes for controlled heating in MFH.     

Formation of FePt intermetallic compound nanoparticles by plasma-induced cathodic discharge electrolysis

Magnetic nanoparticles of FePt intermetallic compound were formed in molten LiCl-KCl-CsCl electrolyte under 1 atm of Ar atmosphere by plasma-induced cathodic discharge electrolysis. By utilizing the displacement reaction between the Fe(0) and Pt(II), FePt intermetallic compound nanoparticles were obtained from the melt. The displacement reaction produced small primary particles that considerably aggregated to form larger secondary particles. The coercivity of the obtained FePt intermetallic compound nanoparticle increased with a longer residence time in the melt. The coercivity of the FePt intermetallic compound nanoparticle obtained after a residence time of 3 h was measured to be 199 mA m⁻¹. FePt intermetallic compound nanoparticles could also be obtained by the co-depositing Fe and Pt from Fe(II) and Pt(II) in the melt. In this case, the primary particle size distribution became broader, but the aggregation of primary particles was suppressed. The coercivity of the obtained FePt intermetallic compound nanoparticles showed a quite high value of 245 mA m⁻¹ that did not depend on the residence time.     

低合金高强钢热浸镀55%Al-Zn-1.6%Si(≤0.1%Ti)合金层的组织及生长动力学

比较研究了H420低合金高强钢板热浸镀55%Al-Zn-1.6%Si (≤0.1%Ti)和55%Al-Zn-1.6%Si金属间反应层组织及生长动力学. 利用光学显微镜、SEM、EDS和XRD对反应层微观组织、厚度、元素分布及相组成进行了分析. 结果表明,金属间反应层都主要由Fe2Al5, Fe4Al13和Fe-Al-Si金属间化合物三相构成. Fe2Al5相与Fe4Al13相交界区域存在少量的Fe-Al-Si-Mn固溶体析出物,可能主要因基板中的Mn元素扩散进入合金层. 金属间反应层的生长速率遵循抛物线规律. 相比较,H420+GL+Ti金属间反应层总厚度平均降低了3.25 mm,Fe2Al5相厚度平均降低了1.83 mm. 主要原因是,Ti-Al键能明显要大于Fe-Al键能,添加Ti影响了Fe-Al的相互作用,从而抑制Fe-Al金属间化合物的形成和生长,最终降低了反应层厚度.     

B掺杂FePt基纳米复合膜的制备与磁学性能研究

利用磁控溅射法将厚度可控的B掺杂到FePt多层膜中,构成FePtB多层膜体系。多层膜结构采用中间层掺杂和底层掺杂等方式组合,由此研究热处理温度与B掺杂对FePtB多层膜体系磁学性能的影响,分析成相过程。另一方面,B层作为中间层掺杂到FePt多层膜样品中构成不同B掺杂浓度的多层膜体系,通过X射线衍射等表征手段研究不同的掺杂浓度对FePt多层膜样品成相及退火温度的影响。实验结果表明,B掺杂的FePt多层膜样品的矫顽力大幅度提高,出现垂直择优取向;随着B层厚度的增加,FePtB多层膜体系的磁有序相比例增加,当B层为14nm时,FePtB多层膜体系展现良好的垂直取向特性。此外,B掺杂降低了FePt多层膜样品的退火温度。     

Synthesis and Characterization of FePt/NiO Core–Shell Nanoparticles

Monodisperse FePt nanoparticles were successfully synthesized using the chemical polyol process. Annealing at the high temperatures is required to achieve the hard ferromagnetic behavior with L1₀ phase. Annealing causes the surfactant surrounding particles to be decomposed. Under such circumstances, FePt particles are agglomerated, and their size increases. In this research, NiO oxide particle with a high melting point was used for the first time as the shell around FePt core particles to prevent agglomeration. As a result, coercivity, H_c, of FePt and FePt/NiO nanoparticles after annealing at 750?°C are equal to 10 and 7?kOe, respectively.     

Corrosion Resistance of Fused Cr_2O_3-Al_2O_3 Grains with Different Compositions

Six kinds of Cr2O3 Al2O3 fused grains ( the mass percent of Cr2O3 was 15% ,40% ,50% ,60% ,85% and 99% ,respectively) were prepared using chrome green and Al2O3 powder as starting materials by electrofusion,named as CR15,CR40,CR50,CR60,CR85, and CR99,respectively. The corrosion resistance of the six kinds of Cr2O3 Al2O3 fused grains ( 4 1 mm) was studied using rotary slag corrosion method. The results show that: ( 1) the corrosion resistance of the fused grains increases with the Cr2O3 content and the grain size increasing; ( 2) the grains of CR99 and CR85 with higher Cr2O3 content are corroded at the slag surface layer,because FeO and Al2O3 in the slag corrode the grains; FeO reacts with Cr2O3 in the aggregates forming ( Fe,Cr) 3O4 spinel firstly,and the spinel reacts with other phases forming composite spinel; when FeO is fully consumed,Al2O3 penetrated into the grains reacts with Cr2O3 forming Al2O3 Cr2O3 solid solution on the grains surface; ( 3) for CR60,the corrosion exists both in the slag surface layer and in the penetration layer; in the penetration layer,CaO and SiO2 react with Al2O3 in Al2O3 Cr2O3 solid solution forming anorthite, gehlenite, and glass phase; the grains of CR50,CR40 and CR15 have the same corrosion mechanism with CR60 in the penetration layer.     

无水硫铝酸钙矿物的合成及形成机制

用化学试剂CaCO3,Al2O3,CaSO4·2H2O制备无水硫铝酸钙(C4A3 (S-))单矿物,借助化学分析法、X射线衍射、差热-热重分析及扫描电镜-能谱仪等研究了C4A3 (S-)矿物的形成机理.研究表明:C4A3 (S-)矿物分别是通过3种不同途径形成的;在煅烧温度低于1 100 ℃时,C4A3 (S-)矿物主要是由CaO,Al2O3,CaSO4直接通过固相反应形成;在煅烧温度高于1100 ℃时,C4A3 (S-)矿物是通过中间矿相七铝酸十二钙(C12A7)或铝酸一钙(CA)的形成而形成的.     

铝合金表面脱氧化物/出光处理技术研究

以含有较多较难去除的含铜金属间化合物黑色颗粒的铝合金2024-T3为研究对象,通过金相观察,开发了一种用于碱蚀后铝合金表面脱氧化物/出光的浓–稀两阶段处理技术。室温下先用含有5.0g/LNaHF2和100g/LFe2(SO4)3的30%(质量分数)硝酸溶液处理7min,然后用含有0.5g/LNaHF2的1%(质量分数)硝酸溶液处理4min,可有效去除碱洗后铝合金表面的黑色氧化物,形成无污染的氧化铝薄层。该工艺简单、快速、成本低,为后续转化反应的顺利进行奠定了基础。     

Green Chemical Synthesis of Silver Nanoparticles and its Catalytic Activity

Silver nanoparticles (Ag(0) NPs) were synthesized by the chemical reduction method, in which ceftriaxone (antibiotic) used as reducing (to convert Ag⁺ to Ag(0)) and capping agent. UV–Visible spectroscopy revealed the first indication of formation of Ag(0) NPs. FT-IR spectroscopy showed the interaction of formation of bonding between antibiotic standard and silver. X-ray powder diffraction powder pattern confirmed the crystalline nature of prepared Ag(0) NPs. These Ag(0) NPs were used as catalyst for three organic hazardous chemicals i.e., 4-nitro-1,3-Phenylene diamine, 6-methyl-2-nitroanilline, 4-methyle-2-nitroanilline. The prepared Ag(0) NPs showed good catalytic activity against these compounds.     

Structural and compositional evolution of FePt nanocubes in oganometallic synthesis

In this study, the mechanisms for the formation of FePt nanocubes via pyrolysis of iron pentacarbonate [Fe(CO)₅] and platinum(II) acetylacetonate [Pt(acac)₂] were investigated. The time evolution of the structure, morphology, and composition of the FePt nanocubes was probed by transmission electron microscopy (TEM) at different reaction stages. On the basis of the detailed characterization, we determined the following aspects of the reaction mechanism: (1) The FePt nanocubes are rapidly formed at 160°C to 180°C by the decomposition of the precursors, and the formation of the FePt nanocubes is dominated by the nucleation of Pt-rich species followed by a slow deposition process of Fe atoms. (2) A thin Fe atomic layer is present on the FePt nanocubes, which does not influence their phase transition into a fct structure. (3) The use of Fe(CO)₅ is the key factor leading to the anisotropic growth of the FePt nanocubes, and the Fe(CO)₅/Pt(acac)₂ molar ratio not only determines the composition of the resulting FePt nanocubes but also affects their morphology and structures.     

Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900–1,000 emu/cm³) characteristic of L1₀ phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.     

渗铝Q235钢的渗层组织和抗高温氧化性能

分析了Q2 3 5钢热浸渗铝和铝硅合金层的显微组织 ,并对其抗高温氧化性能进行了研究。热浸渗层由镀层 (表层 )和化合物层 (内层 )两层组成 ,金相和X射线能谱分析 (EDS)结果表明纯铝渗层的化合物层呈厚齿状 ,由η相 (Fe2 Al5)组成 ;铝硅合金渗层的化合物层呈薄带状 ,由Si合金化的η相即Fe2 (Al Si) 5组成。热浸渗层经扩散退火后 ,表面镀层消失 ,渗层由表及里依次出现 η相、ζ相、β2 相、β1相和固溶体α相等过渡组织。 80 0℃高温氧化试验结果表明 ,渗纯铝Q2 3 5钢的抗高温氧化性能优于 1Cr1 8Ni9Ti不锈钢 ,硅的加入可以改善热浸工艺性能 ,但降低了渗层的抗高温氧化性能。     

Thermodynamic analysis and experimental verification of interface reactions of iron aluminide/tetragonal zirconia composite

Abstract

This paper described the thermodynamic analysis and experimental verification of interface reactions between iron aluminide intermetallic and tetragonal zirconia. Thermodynamic analysis confirmed that chemical reactions between Fe–Al intermetallic and ZrO₂ (3 mol.–%Y₂O₃ stabilised zirconia) mainly depended on the Al content in Fe–Al intermetallic. For ZrO₂(3Y)/Fe₃Al composite, the interface reactions to form Al₂O₃ and ZrAl₂ would take place when Al content was >40 at-% in Fe–Al intermetallic, while no interface reaction occurred when using Fe₃Al as toughening phase. ZrO₂(3Y)/Fe₃Al composite was synthesised by hot press sintering to further verify the thermodynamic analysis of interface reactions between iron aluminide intermetallic and tetragonal zirconia. The phase composition, morphology and interface structure of ZrO₂(3Y)/Fe₃Al were investigated by X-ray diffraction, SEM and TEM. The results show that Fe₃Al was thermodynamic stable in ZrO₂(3Y) matrix, which was in good agreement with thermodynamically analysis.     

Facile synthesis of metal oxide/reduced graphene oxide hybrids with high lithium storage capacity and stable cyclability

We report an environment-friendly approach to synthesize transition metal oxide nanoparticles (NPs)/reduced graphene oxide (rGO) sheets hybrids by combining the reduction of graphene oxide (GO) with the growth of metal oxide NPs in one step. Either Fe2O3 or CoO NPs were grown onto rGO sheets in ethanol solution through a solvothermal process, during which GOs were reduced to rGO without the addition of any strong reducing agent, e.g. hydrazine, or requiring any post-high-temperature annealing process. The GO or rGO during the precipitation of metal oxide NPs may act as heterogeneous nucleation seeds to facilitate the formation of small crystal grains. This may allow more efficient diffusion of Li ions and lead to high specific capacities. These metal oxide NPs-rGO hybrids were used as anodes for Li-ion batteries, which showed high capacities and excellent charge-discharge cycling stability in the voltage window between 0.01 and 3.0 V. For example, Fe2O3 NPs/rGO hybrids showed specific capacity of 881 mA h g(-1) in the 90th cycle at a discharge current density of 302 mA g(-1) (0.3 C), while CoO NPs/rGO hybrids showed a lower capacity of 600 mA h g(-1) in the 90th cycle at a discharge current density of 215 mA g(-1) (0.3 C). These nanohybrids also show excellent capacities at high C rate currents, e.g. 611 mA h g(-1) for Fe2O3/rGO sample in the 300th cycle at 2014 mA g(-1) (2 C). Such synthesis technique can be a promising route to produce advanced electrode materials for Li-ion batteries.     

Y2O3添加量对Al2O3/ZrO2复合材料烧结行为和热机械性能的影响

研究了Y2O3添加量对Al2O3/ZrO2复合材料烧结行为和热机械性能(高温抗折强度和抗热震性)的影响,并研究了这些性能与物相组成和显微结构间的关系.结果表明:Y2O3在Al2O3/ZrO2复合材料中起稳定ZrO2晶型、改善烧结致密化、提高高温抗折强度和抗热震性的作用.当Y2O3添加量为1%时,试样的烧结性能和高温抗折强度较佳,体积密度、显气孔率和线收缩率分别为3.27 g/cm3、21.95%和7.43%,高温抗折强度达29 MPa;抗热震性则在Y2O3添加量为0.5%时较佳,其残余强度保持率为71%.Y2O3对Al2O3/ZrO2复合材料烧结性能和热机械性能的影响与Y2O3/ZrO2固溶体的形成、Al2O3和ZrO2晶体间的结合程度及试样中微裂纹含量密切相关.     

Origin of light scattering in ytterbium doped calcium fluoride transparent ceramic for high power lasers

The origin of light scattering defects was studied in transparent 6 at% Yb:CaF₂ ceramics. Samples were synthesized by a soft chemistry route followed by sintering and hot pressing which leads to highly transparent ceramics with low scattering losses (0.016 cm⁻¹ at 1200 nm). Light scattering defects were studied using scanning transmission electron microscopy (STEM) and high angle annular dark field-STEM (HAADF-STEM) techniques. Energy dispersive X-ray spectroscopy showed a 50% increase in Yb³⁺ concentration at grain boundaries. A 3-5 nm thick oxygen rich phase was detected at some grain boundaries by both HAADF-STEM and EDS. The origin of the oxygenized grain boundaries was traced to a 2-15 nm thick oxygenized shell present on the starting powders. Analysis of high resolution HAADF-STEM images revealed that Yb³⁺ substitutes into the fluorite lattice as clusters rather than individual ions, but the types of clusters could not be identified by this imaging technique.     

添加剂对Al2O3(f)/Ti-Al原位复合材料纤维生成形式的影响

以金属钛粉、铝粉及添加剂为原料压制成预制体,通过石墨与氧化铝混合粉对预制体的覆埋实现气氛保护并进行热处理,使其原位合成氧化铝纤维增强钛铝金属间化合物复合材料。通过XRD和SEM测试,分析了材料最终晶相组成及内部显微结构,并结合DTA进行了反应的热力学研究。SEM分析显示Ti-A l-Nb2O5、Ti-A l-La2O3、Ti-A l-Kaolin三种体系配料均可合成出A l2O3(f)/Ti-A l原位复合材料,但A l2O3纤维的生成方式不同:Ti-A l-Nb2O5体系以A l、Nb2O5的铝热反应为主生成;其余两种体系主要是A l纤维被氧化形成A l2O3纤维。铝热反应迅速且放热量高,使纤维纤细,团聚性较强;缓慢氧化得到的纤维直径较粗,分散性较好。     

自蔓延高温合成TiB2+Al2O3/NiAl复合材料

Al2O3 TiB2复相陶瓷材料具有金属材料无法比拟的高硬度、高熔点、高导热、低膨胀系数、高耐磨性、高温化学稳定性等优良的性能,但由于两种材料都属于硬而脆的材料,复合后仍然存在脆性大、裂纹敏感性强、抗机械冲击性和温度急变形差等缺点。为了克服这些缺点,本文探索了在陶瓷相中添加金属间化合物(NiAl或FeAl)。X射线衍射结果表明合成产物的主要组成相分别为Al2O3 TiB2、Al2O3 TiB2 NiAl及Al2O3 TiB2 FeAl,反应按预期进行,且燃烧合成反应进行的较为彻底。通过对不同成分反应产物的致密度、强度、断裂韧性对比,可知产物的致密度在FeAl含量为15%时达到最高99.5%,Al2O3 TiB2 NiAl体系中NiAl含量为20%达到最高98.5%。随金属间化合物含量的增加,合成复合材料的硬度下降,而断裂韧性提高。     

Cu—Mn系中温结晶釉的研制

采用高岭土、石英、钾长石等为基本原料．引入氧化铜、氧化锰为析晶剂．制备了Cu—Mn系中温结晶釉。探讨了配方中SiO2、Al2O3的含量和釉层厚度对釉面性能的影响．并对釉面光泽度和显微硬度进行了测试。实验结果表明：当配方中Al2O3含量为0．125%、SiO2含量为0．758%时,且釉层厚度为1mm左右时。在合适的烧成制度下。釉面晶花均匀、光泽度良好．并具有良好的釉面显微硬度。