Interface reactions between glass melts containing transition metal oxides and ferrites

The interface reactions between SiO₂-PbO-MO melts (M = Fe, Mn, Zn and Ni) and Mn-Zn and Ni-Zn ferrites were studied using electron probe microanalysis and X-ray diffraction. Ni ions in the glass melt containing NiO were localized at the interface between the glass and Mn-Zn ferrite. The Ni-rich layer was also detected at the interface between NiO containing glass melt and Ni-Zn ferrite; the composition of this layer was thought to be close to NiFe₂O₄. Pb₈NiSi₆O₂₁ crystal was deposited as the product of the reaction with the glass melt and Mn-Zn ferrite at 700 °C. As compared with Mn-Zn ferrite, no reaction products were formed in Ni-Zn ferrite at various temperatures. The dissolution length of Mn-Zn ferrite in SPN5 glass melt was found to be smaller than for other melts, and it is concluded that the NiO-rich layer at the surface of the ferrite is chemically very durable to the glass melts.     

反应物量对燃烧合成Ni-Zn铁氧体粉的影响

为探讨燃烧合成法制备Ni0.4Zn0.6Fe2O4粉末工业化放大合成的可行性,研究不同反应物量对燃烧合成制备的Ni0.4Zn0.6Fe2O4粉体及烧结后产物的物相、微观形貌及磁性能的影响,对终产物进行XRD、SEM和EDS分析,对样品经行磁性能测试.结果表明:Fe-Fe2O3-Zn O-Ni O体系燃烧合成过程是以扩散-溶解-析出机制进行的,燃烧反应在非平衡条件下进行,燃烧产物的主要物相为Ni-Zn铁氧体,其中存在Zn O及一些铁的氧化物的杂质,产物经热处理后物相全部转变为尖晶石结构;随着反应物量的增加,产物颗粒尺寸增大,均匀度增加,反应物量的增加对产物的磁性能影响不大;随着反应物量的增加,饱和磁化强度逐渐增加,矫顽力基本不变,反应物量为1 500 g时制备的产品磁性能最佳,具有较高的饱和磁化强度Ms=63.72 emu/g和较低的矫顽力Hc=15.61 Oe.     

镍锌铁氧体纳米材料制备及其光催化性能研究

以金属硝酸盐、硝酸镍、硝酸铁、硝酸锌为原料,柠檬酸和葡萄糖作为分散剂和燃烧剂,通过溶胶-凝胶自蔓燃法在200℃下制备了纳米Ni0.5Zn0.5Fe2O4光催化剂。通过XRD、TEM、VSM分析表明,所制样品为纯相尖晶石型镍锌铁氧体,颗粒大小约为18nm,饱和磁强度Ms为31.14A·m2/kg,剩余磁强度Ms为2.08A·m2/kg,矫顽力Hc为4949A/m,表现为铁磁性。样品的光催化性能实验表明,在Ni-Zn铁氧体+H2O2+可见光系统中,亚甲基蓝的降解率在2h内达到98%。反应后的样品通过磁力回收,用去离子水和无水乙醇清洗,60℃烘干后,进行3次重复实验,样品的降解率没有降低,表明样品性能稳定,是一种可回收的光催化剂。     

喷射-沉淀法合成纳米晶Ni-Zn铁氧体及表征

采用喷射-沉淀法成功地制备了纳米晶Ni-Zn铁氧体粉料。通过XRD、TG．DSC、SEM、TEM和BET等测试手段分析了其微观结构和形貌．结果表明：沉淀剂种类和溶液pH值对喷射．共沉淀法制备Ni-zn铁氧体纳米粉的物相和结构有着显著影响。采用NaOH溶液为沉淀剂，pH值范围为7．0～7．5，可以获得颗粒细小均匀、形状完整的纳米晶Ni-Zn铁氧体粉料。在600℃煅烧1．5h，样品晶粒尺寸为30nm左右，平均颗粒尺寸小于100nm。     

EDTA络合法制备Ni-Zn铁氧体及其磁学性质

以金属硝酸盐为原料,通过乙二胺四乙酸(EDTA)络合法制备了尖晶石型Ni1-xZnxFe2O4(x=0.0-0.7)晶体。通过TG-DTA考察了制备过程,采用XRD、FT-IR、SEM和VSM等对产物进行了表征,研究了热处理温度和Zn取代量对晶型结构和磁学性质的影响。同传统的固相法相比(1300℃/20h),制备单相Ni-Zn铁氧体所需的焙烧温度降至700℃,焙烧时间缩短至2h。随着Zn取代量的增加,晶胞参数递增,而矫顽力(Hc)和居里温度(Tc)逐渐下降。饱和磁化强度(Ms)随Zn取代量呈先递增至x=0.4后再逐渐下降。在1.5MHz的交变磁场中,所制粒子的感应温度接近设计的居里温度,能够适于感应加热的应用。     

Soft magnetic and high-frequency properties of Ni-Zn ferrite film with FeMn underlayer

Ni_0.45Zn_0.55Fe₂O₄ (40 nm) single-layer and Fe₅₀Mn₅₀ (25 nm)/Ni_0.45Zn_0.55Fe₂O₄ (40 nm) bilayer films were prepared on Si(111) substrates by radio frequency magnetron sputtering at room temperature, and the influence of FeMn underlayer on the microstructure and magnetic property of Ni-Zn ferrite film has been investigated. It was found that the introduction of Fe₅₀Mn₅₀ underlayer resulted in a decrease from 7.1 to 3.1 kA/m in coercivity and increase from 0.22 to 0.60 in residual magnetization ratio of the ferrite film. The complex permeability μ = μ′ − iμ″ values of the films were measured at a frequency of up to 5 GHz. An obvious resonance peak at about 1.65 GHz of the bilayer film appeared in the permeability spectrum. The reason has been researched preliminarily and was ascribed to the change of the film's microstructure with FeMn underlayer.     

Upconversion photoluminescence in GeO2-PbO glass codoped with Nd3+ and Yb3+

Frequency upconversion (UC) photoluminescence (PL) in GeO₂-PbO glass codoped with trivalent ions of neodymium (Nd³⁺) and ytterbium (Yb³⁺) is reported. A diode laser operating at 977.7 nm, in resonance with the ytterbium transition ²F_7/2 → ²F_5/2, was the excitation source. Four PL spectral lines, corresponding to the Nd³⁺ transitions ⁴G_9/2 → ⁴I_9/2 (at 500 nm), ⁴G_7/2 → ⁴I_9/2 (at 550 nm), [⁴G_5/2; ²G_7/2] → ⁴I_11/2 (at 595 nm) and ⁴G_7/2 → ⁴I_13/2 (at 660 nm), were observed and characterized. The quadratic dependence of the PL intensities versus the laser power indicates that two laser photons participate in the UC process. The temperature dependence of the PL emissions from 300 to 390 K was also investigated to identify the contribution of phonons for the UC process. The dependence of the UC intensity with the Yb³⁺ concentration and the time behavior of the UC signal indicated the presence of two energy transfer (ET) pathways involving Nd³⁺-Yb³⁺ pairs and Yb³⁺-Nd³⁺-Yb³⁺ triads. Rate-equations for the population densities of the rare-earth energy levels were used to describe the dynamics of the UC emission and to determine the ET rates.     

Preparation of nickel and Ni-Zn ferrite films by thermal decomposition of metal acetylacetonates

Nickel and Ni-Zn ferrite (Ni_1–x Zn _x Fe₂O₄) films were prepared on various substrates (quartz glass, MgO single crystal, etc.) by thermal decomposition of metal acetylacetonates (Ni (acac)₂ · 2H₂O, Zn (acac)₂ · 2H₂O and Fe (acac)₃). Typical decomposition and heat treatment conditions for obtaining a single phase of NiFe₂O₄ film were as follows: evaporation temperature of Ni-Fe complexes: 230°C, the mole concentration of Fe (acac)₃,R (%) = Fe (acac)₃/(Fe (acac)₃ + Ni (acac)₂ · 2H₂O) = 33, substrate temperature: 330 to 550° C, and heat treatment of the as-grown film: 800 to 1000° C, 1 h. Ni_1–x Zn _x Fe₂O₄ films were obtained by controlling the compositionR in Ni-Fe complexes and the evaporation temperature of Zn (acac)₂ · 2H₂O. The Ni-Zn ferrite film at the compositionx = 0.37 (Ni_0.63Zn_0.37Fe₂O₄) gave the maximum saturation magnetization _s = 60 emu g^–1 and the coercive forceHc 25 Oe. These films showed a magnetic anisotropy which makes the magnetization easy parallel to film surface.     

XRD and IR analysis of nanocrystalline Ni-Zn ferrite synthesized by the sol-gel method

Nanocrystalline Ni_1−xZn_xFe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites were synthesized by the sol-gel method. The obtained powder was annealed at temperatures from 500 to 1000 °C. X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to study the structural changes taking place with varying Zn content x. The grain size decreased while the lattice parameter increases with the increase of the Zn content.     

Al2O3型壳与定向凝固合金IC10的界面反应

采用扫描电子显微镜、能谱分析等研究定向凝固合金IC10与Al2O3陶瓷型壳的界面反应.结果表明:Al2O3型壳与IC10合金发生界面反应,合金表面粘砂严重;IC10合金中由于含有1.5％(质量分数,下同)Hf,使其活泼程度明显增加.界面反应层厚度约5～8μm,反应区分成内、外两层,外层为HfO2,内层为富(Al,Ta,Nb)氧化物层,Al含量占80％.Hf和Al是界面反应的主导元素.     

黄钠铁矾渣制备镍锌铁氧体及其表征

利用化学共沉淀法,以黄钠铁矾渣为原料制备镍锌铁氧体。以正丁胺为沉淀剂,在室温条件下,通过共沉淀铁、镍、锌(镍、锌由硫酸锌、硫酸镍按Ni0.5Zn0.5Fe2O4比例补加)制备镍锌铁氧体样品。采用SEM、XRD和FT-IR对该样品进行表征。结果表明,制备所得的样品为镍锌铁氧体。同时,通过磁滞回线显示,镍锌铁氧体比饱和磁化强度为9.04A·m2/kg,比剩余磁化强度为0.65 A·m2/kg,矫顽力为2.47kA/m,具有软磁材料的低比剩余磁化强度和低矫顽力的特性。     

Interface reactions between titanium thin films and (1¯1 2) sapphire substrates

We have studied the reactivity of Ti with the R-plane (1ˉ1 2) of sapphire from room temperature to 1250 °C by X-ray photoemission spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Rutherford backscattering spectroscopy (RBS). The combination of these techniques allowed the interface reactions to be studied from the monolayer regime up to the bulk regime. XPS showed that at room temperature, monolayer coverages of Ti reduced the sapphire surface to form Ti-O and Ti-Al bonds. TEM, XRD, and RBS showed that annealing of room-temperature deposited Ti resulted in an interfacial region consisting of two layers, a Ti₃Al[O] layer adjacent to the sapphire and a Ti_0.67 [O_0.33] layer at the free surface. The growth of the Ti₃Al[O] layer had an activation energy of 103.4±25 kJ deg-mole. The nature of the interfacial reaction between Ti and sapphire was similar for Ti coverages from the monolayer to the bulk regime.     

Magnetic and microwave absorption properties of polymer composites with amorphous Fe-B/Ni-Zn ferrite nanoparticles

In this study, polymer composites containing amorphous Fe-B submicrometer particles and Ni-Zn ferrite nanoparticles were fabricated. A polymer composite of mixed particles showed high permeability of μ^′r=13.7 at 0.5 GHz and μ^″r=8.3 at 1.2 GHz. In addition, this composite exhibited good microwave absorption properties (R.L. < −20 dB) in the frequency range of 0.65-1.12 GHz for absorber thickness of 2.38-4.06 mm. It is concluded that this polymer composite can be used for fabricating microwave absorbers in the UHF range, and would result in thinner microwave absorbers than any other microwave absorbers reported thus far.     

不同形态SiO2改性钙硅硼系微晶玻璃结构与性能

分别研究了高硅氧玻璃(96wt%SiO2,非晶态)与二氧化硅(99wt%,石英相)的添加对CaO-SiO2-B2O3(CSB)微晶玻璃微观结构、烧结性能以及介电性能的影响.结果表明:不同形态SiO2的添加均可以有效地降低介电常数,同时高硅氧玻璃的引入增加了试样的介电损耗.添加15wt%SiO2、850℃低温烧结试样,在10MHz下,介电常数为6.01,介电损耗1.2 × 10-3,且在5～40MHz频率范围内,介电常数随频率的变化不大.烧结试样的主要晶相为Quartz、CaSiO3和CaB2O4.     

Correlation between oxygen-deficient center formation and volume compaction in synthetic SiO2 glass upon ArF or F2 excimer-laser irradiation

Correlations between the refractive-index change and the concentration of an oxygen-deficient center (ODC) induced by thermal treatments and laser irradiation are examined to clarify the origin of laser-induced volume compaction in synthetic SiO2 glasses. A linear correlation between them was clearly observed for thermally induced ODC, whereas no correlation was found for ArF or F2 laser irradiation. The results demonstrate that the dominant origin of laser-induced compaction is not ODC formation. Furthermore, we found that the presence of H2 in SiO2 glass had no influence on volume compaction but enhanced crack formation upon laser irradiation, a phenomenon most likely due to stress corrosion.     

Interface reactions in the system sialon-Cu-Cu2O

The interface reactions between an /gb-sialon ceramic and Cu, Cu₂O or a Cu-Cu₂O mixture have been studied. A fully dense sialon ceramic material prepared by pressureless sintering at 1775 ° C with 6 wt% Y₂O₃ as sintering aid, were coldpressed together with Cu, Cu₂O or Cu-Cu₂O mixtures into cylindrical tablets. These samples were heat treated at 700, 850 and 1000 ° C in evacuated silica tubes. The reaction zones formed between the sialon and the powder compacts were studied in a SEM equipped with an EDS system. No reaction between copper and sialon ceramic could be detected in spite of prolonged heat treatment at 1000 ° C. Cu₂O reacted with the ceramic at 850 and 1000 ° C to form a glass containing copper and all the other sialon components. The interaction between the sialon material and the Cu-Cu₂O powder compacts was characterized by a redox reaction. The sialon was thus oxidized to SiO₂ and N₂ while Cu₂O was reduced to copper. A glass phase containing silicon, aluminium, yttrium and copper was also formed in the reaction.