Effect of Dual-Magnetic-Layer on Performance of CoCrPt-SiO2 Perpendicular Media

CoCrPt-SiO₂ perpendicular recording media have been investigated in order to increase media signal-to-noise ratio (SNR) by introducing a dual-magnetic-layer structure into the CoCrPt-SiO₂ recording layer. The dual-magnetic-layer structure consists of low- and high-M_s granular layers. The magnetic properties and recording performances of two kinds of dual-magnetic-layer media, one with a low-M_s bottom layer and another with a low-M_s top layer, were measured. The coercivity of the low-M_s bottom medium is higher than that of the low-M_s top medium, although they have the same thermal stability (K_uV/k_B T). We showed that using the low-M_s bottom layer gives a higher SNR. That is to say, SNR was improved by 3 dB compared with that of the high-M_s single-magnetic-layer medium, and it was even higher than that of the low-M_s single-magnetic-layer medium. It is thus concluded that the dual-magnetic-layer structure with the low-M_s bottom layer is effective in increasing SNR of perpendicular media     

Bit-Percolation Studies on CoPtCr–SiO2 Perpendicular Magnetic-Recording Media

Bit percolation degrades the performance of high-density perpendicular magnetic recording. The magnetic cluster size determines the limit of the recordable bit length. In order to examine the parameter, which influences the high-density recording characteristics, we have investigated the relationship between magnetic cluster size and the recording bit length at which bit percolation begins to occur in a CoPtCr-SiO₂ perpendicular magnetic-recording medium to the range of 1500 kfci. Our experimental data indicate that the onset of bit percolation takes place at a recording bit length close to the magnetic cluster size of the medium     

Low-Noise Crystalline Soft Underlayer for CoCrPt:SiO2 Perpendicular Recording Media

In this paper, a crystalline soft underlayer with chemical formula (Fe₁₅Co₈₅)₉₄Cr₃Ta₃ for CoCrPt:SiO₂-based perpendicular media is studied. Three kinds of approaches are used to successfully reduce the noise from the soft underlayer. X-ray diffraction is used to study the effect of the preparation parameters on the orientations of the soft underlayer and the recording layer. The mechanism for the noise reduction is discussed     

Recording Resolution and Writability for (Co-Pt)-SiO2/Co-SiO 2 Hard/Soft-Stacked Granular Perpendicular Media

The magnetic properties and recording performance of hard/soft stacked media consisting of a magnetically hard 9-nm-thick (Co-Pt)-SiO ₂ layer underneath a thin (2-3 nm) soft granular layer were studied. Experimental results indicated that an increase in the mean value of saturation magnetization of the soft layer langM_s ^softrang was very effective at improving the recording resolution D₅₀ due to an increase in the slope of magnetization curve alpha. The use of a Co-SiO₂ layer, which has the highest langM_s ^softrang in the present study, resulted in the highest D₅₀ value. It is likely that the increase in alpha was mainly caused by the demagnetization field in grains due to the difference between langM _s ^softrang and the mean value of saturation magnetization of the hard layer, langM_s ^hardrang. Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-SiO₂/Co-SiO₂ stacked media changed systematically as theoretically predicted on reducing the interfacial exchange coupling by using NiFeCr-SiO₂ or Pt-SiO₂ interlayers. The reduction of remanence coercivity H_r was achieved by controlling the thickness and film composition of the interlayer, moreover, a high-langM_s ^softrang enhanced the H_r reduction. The H_r reduction improved recording writability without degrading D₅₀, the signal to medium noise ratio SN_mR and thermal stability     

纳米SiO2含量对尼龙6/SiO2纳米复合材料蠕变性能的影响

通过原位聚合法制备了尼龙6/SiO2纳米复合材料。利用扫描电镜观测了复合材料的表面形貌,结果表明,纳米SiO2颗粒均匀地分布在尼龙6基体中。利用电子万能试验机对不同纳米SiO2含量的复合材料进行了短期(24 h)蠕变性能的测试,结果表明,随着纳米SiO2含量的增加,复合材料的抗蠕变性能也随着增大;在30 MPa、40 MPa和50 MPa的应力水平下,纳米SiO2含量为5%的纳米复合材料的蠕变应变分别比纯尼龙6降低了38.4%、61.0%和71.9%。     

掺杂不同量Nd2O3对CeO2-ZrO2-Al2O3材料性能的影响

采用共沉淀法制备了一系列Nd2O3含量为0～13wt%的CeO2-ZrO2-A12O3(CZA)复合氧化物,并通过X射线衍射(XRD)、低温N2吸附–脱附、氧脉冲吸附(OSC)、H2–程序升温还原(H2-TPR)及扫描电子显微镜(SEM)等方法对所制备的材料进行了表征.研究结果表明,Nd2O3在CZA固溶体中的溶解限约为10wt%,过量Nd的添加会出现分相形成Nd0.5Ce0.5O1.75氧化物.掺杂适量Nd能有效抑制氧化物晶粒的长大,提高材料的热稳定性和氧化还原性能.Nd2O3的掺杂量为10wt%时,样品的织构稳定性最好,1000℃老化5 h后,比表面积和孔容分别达97.14 m2/g和0.44 mL/g.Nd2O3的掺杂量为7wt%时,样品有高的储氧量,经600℃和1000℃焙烧后储氧量分别为938.01μmol/g和821.72μmol/g;体相氧的移动能力最强,还原性能最佳,老化后还原峰温由465℃升高到483℃.SEM结果表明,所制备的材料均为球形颗粒,Nd2O3的添加可以有效阻止高温焙烧过程中粒子的团聚.     

Thermal shock resistance of the porous Al2O3/ZrO2 ceramics prepared by gelcasting

Porous Al₂O₃/ZrO₂ ceramics with porosity varying from 6% to 50% were fabricated by gelcasting using polystyrene (PS) as pore-forming agent. The effects of sintering temperature on porosity, strength as well as pore size were investigated. The flexural strength of these porous ceramics at room temperature significantly decreases as the porosity increases. Thermal shock resistance of these ceramics was improved by increasing the porosity. Both the critical difference temperature (ΔT_c) and residual strength of high porosity ceramics were higher than those of low porosity ceramics. These improvements can be attributed to the pores in the specimens which relax the thermal shock stress and arrest the propagation of microcracks effectively, which is confirmed by XRD analysis of specimens which encountered different thermal shock temperature difference.     

过氧化氢对质子交换膜热分解机理的影响

采用非等温热重-微分热重(TG-DTG)技术研究了燃料电池质子交换膜在过氧化氢氧化后的热分解机理,并用Achar和Coats-Redfem方法对非等温动力学数据进行了分析,得到了其热分解的反应机理函数和动力学参数.计算结果显示,第一阶段热分解过程受(D3)三维扩散机理控制,表现活化能为172.6 kJ/mol,指前因子...     

TiO2中间层对基于溶胶–凝胶法制备的VO2薄膜光学特性的影响（英文）

为了提高VO2薄膜的热致相变性能,采用复合结构与掺杂相结合的方法,首先通过溶胶–凝胶法在云母基底上制备锐钛型TiO2薄膜,再在光致亲水性处理的TiO2/云母基底上涂覆V2O5以及掺钨V2O5水溶胶,然后经热处理获得VO2/TiO2及VxW1-xO2/TiO2复合薄膜。采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、傅立叶变换红外光谱仪(FTIR)研究薄膜的物相、表面形貌以及热致相变特性.结果表明,VO2/TiO2复合薄膜晶体生长为(011)面择优取向;VxW1-xO2/TiO2复合薄膜产生多种取向。TiO2中间层有助于使VO2薄膜生长致密,相变温度降低,更使VxW1-xO2/TiO2复合薄膜滞后温宽降至约4℃。     

Thermal treatment stabilization processes in SnO2 thinfilms catalyzed with Au and Pt

We examined the thermal treatment stabilization processes in SnO ₂-based thin films for gas-sensing applications in order to understand their influence on structural properties and possible relations with functional behavior of the sensors. The films of SnO₂ were deposited by magnetron sputtering, following the rules of the rheothaxial growth and thermal oxidation (RGTO) technique and annealed in humid synthetic air at 600°C. Afterward, a thin overlayer of gold or platinum was deposited on the oxidized films. The samples were characterized soon after catalyzer deposition and after one-hour aging process at 400°C, in order to evaluate stabilization process influence as a function of catalyzer. X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM) demonstrated that a short aging affects the microstructure of gold-catalyzed samples, while it does not influence platinum catalyzed ones. The results of the microstructural characterization were confirmed by electrical measurements of gas-sensitivity: the short-aging influences the stability of gas-sensing parameters only in gold-catalyzed samples     

Fabrication of SmCo5 Double-Layered Perpendicular Magnetic Recording Media

We fabricated SmCo₅ double-layered perpendicular magnetic recording media with high perpendicular magnetic anisotropy for realizing ultra high density recording. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. We report here for the first time the read-write characteristics of SmCo₅ double-layered perpendicular magnetic recording media. The medium noise was small in the medium with a Sm-Co layer deposited under high Ar gas pressure owing to small magnetic clusters     

Catalytic reduction of low-concentration CO2 with water by Pt/Co@NC

The reduction of low-concentration carbon dioxide with water to organic fuels is still a huge challenge. In this study, we successfully designed the partially oxidized cobalt nanoparticles coated by the nitrogen-doped carbon layer (Co@NC) of 2–8?nm via a facile method and then interspersed with different amount of Pt nanoparticles. The Co@NC decorated with 1?wt% Pt exhibits the best ability for CO₂ reduction to CH₄ and a CH₄ production rate of 14.4?μmol·g^?1·h^?1 is achieved. It is worth noting that the system is carried out under low-concentration CO₂ (400?ppm) circumstance without any sacrificial agent, which could be meaningful to the design of catalysts for atmospheric CO₂ reduction.     

Thermal evolution of TiO2---ZrO2 composites prepared by chemical coating processing

A xZrO₂ (100−x)TiO₂ composite gel powder (x = 50 mol%) has been prepared by chemical processing of anatase as inner core coated with in situ precipitated amorphous zirconia as outer core, which was obtained from controlled hydrolysis of zirconyl chloride using ammonia at pH=9–10. The thermal evolution of this composite is reported, showing the crystallization of metastable cubic/tetragonal zirconia at 437°C, as detected by DTA at 10°C min⁻¹ and XRD, with activation energy of 407 ± 10 kJ mol⁻¹, and the feasibility of preparing zirconium titanate powders by reaction of TiO₂ and ZrO₂ by heating at higher temperatures is discussed.     

Effect of the SiO2/TiO2 ratio on the solid acidity of SiO2-TiO2/montmorillonite composites

SiO₂-TiO₂/montmorillonite composites with varying SiO₂/TiO₂ molar ratios were synthesized and the effect of the SiO₂/TiO₂ ratio on the solid acidity of the resulting composites was investigated. Four composites with SiO₂/TiO₂ molar ratios of 0, 0.1, 1 and 10 were synthesized by the reaction of colloidal SiO₂-TiO₂ particles prepared from alkoxides with sodium-montmorillonite at room temperature. The composites showed slight expansion and broadening of the XRD basal reflection, corresponding to the intercalation of fine colloidal SiO₂-TiO₂ particles into the montmorillonite sheets and incomplete intercalation to form disordered stacking of exfoliated montmorillonite and colloidal SiO₂-TiO₂ particles. The colloidal particles crystallized to anatase in the low SiO₂/TiO₂ composites but remained amorphous in the high SiO₂/TiO₂ composites. The specific surface areas (S_BET) of the composites measured by N₂ adsorption ranged from 250 to 370 m²/g, considerably greater than in montmorillonite (6 m²/g). The pore size increased with decreasing SiO₂/TiO₂ molar ratio of the composites. The NH₃-TPD spectra of the composites consisted of overlapping peaks, corresponded to temperatures of about 190 and 290 °C. The amounts of solid acid obtained from NH₃-TPD were 186-338 μmol/g in the composites; these values are higher than in the commercial catalyst K10 (85 μmol/g), which is synthesized by acid-treatment of montmorillonite. The present sample with SiO₂/TiO₂ = 0.1 showed the highest amount of acid, about four times higher than K10.     

Highly a-oriented SrBi2Ta2O9 thin film on (111) Pt/TiO2/SiO2/Si substrate by eclipse pulsed laser deposition

A highly a-oriented SrBi₂Ta₂O₉ thin film with a polycrystalline structure was deposited on a preferentially oriented (111) Pt/TiO₂/SiO₂/Si substrate by eclipse pulsed laser deposition (PLD) method. The SrBi₂Ta₂O₉ thin film exhibited flat and smooth surface with the surface roughness of about 0.5 nm resulting from reducing particulates generated by on-axis PLD. The SrBi₂Ta₂O₉ thin film showed a good ferroelectric property with the high remanent polarization of 12 μC/cm² and the low coercive electric field of 140 kV/cm. For the highly a-oriented SBT thin film, domain switching and reading were performed by Kelvin probe force microscope (KFM). The KFM data indicate a good ferroelectric property of the highly a-oriented SrBi₂Ta₂O₉ thin film with high KFM signals that reflect ferroelectric polarizations.     

超声波及分散剂对纳米SiO2/CaCO3/Al2O3颗粒分散特性的影响

在材料科学领域,颗粒的均匀分散是获得具有较好的显微结构和性能材料制品的基础。采用分光光度计法表征分散效果,研究了超声波及不同分散稳定剂复合作用下纳米SiO_2、纳米CaCO_3、纳米Al_2O_3颗粒的分散性能,并结合DLVO理论探讨了分散机理,给出了分散剂优选方案。结果表明,超声波处理纳米颗粒悬浮液可以有效打破纳米颗粒团聚;不同分散剂对不同纳米颗粒的分散效果差异较大,NS颗粒相比NC、NA更难被分散剂分散,分散剂SHMP、SDBS作用效果随用量的增大先增强后减弱,分散剂PCS作用效果随用量的增加而增强;分散剂种类、用量会影响纳米悬浮颗粒的双电层厚度和颗粒周围空间微环境,从而影响分散体系的稳定性。     

Complete oxidation of acetaldehyde on Pt/CeO2-ZrO2-Bi2O3 catalysts

Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts for catalytic combustion of acetaldehyde, which is one of volatile organic compounds (VOCs), were prepared by a wet impregnation method in the presence of polyvinylpyrrolidone K25 (PVP). The addition of PVP in the preparation process was effective to enhance the specific surface area and the Pt²⁺ ratio on the surface. Additionally, the pore volume and size of the catalysts were modified by the PVP addition. The Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts are specific for the total acetaldehyde oxidation and CO and any acetaldehyde-derivative compounds were not observed as by-products. The catalytic activity of the Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts was significantly promoted by the PVP addition and the total oxidation temperature decreased. By the optimization of the amount of platinum, the complete oxidation of acetaldehyde was realized at a temperature as low as 140 °C on a 10 wt%Pt/CeO₂-ZrO₂-Bi₂O₃ catalyst.     

Dependence of La2O3 content on the nonlinear electrical behaviour of ZnO, CoO and Ta2O5 doped SnO2 varistors

The effects of La₂O₃ on the properties of (Zn, Co, Ta) doped SnO₂ varistors were investigated in this study. The samples with different La₂O₃ concentrations were sintered at 1400 °C for 2 h and their properties were characterized by XRD, SEM, I-V and impedance spectroscopy. The grain size was found to decrease from 13 μm to 9 μm with increasing La₂O₃ content. The addition of rare earth element leads to increase the nonlinear coefficient and the breakdown voltage. The enhancement was expected to arise from the possible segregation of lanthanide ion due to its larger ionic radius to the grain boundaries, thereby modifying its electrical characteristics. Furthermore, the dopants such as La may help in the adsorption of O′ to O″ at the grain boundaries characteristics.     

纳米-Al2O3/SiO2加入量对MgO-Al2O3-SiO2复相陶瓷烧结机理的影响

为了探究纳米-Al₂O₃/SiO₂加入量对MgO-Al₂O₃-SiO₂复相陶瓷烧结行为的作用机理。以微米级MgO、纳米级Al₂O₃和SiO₂为主要原料制备陶瓷基复合材料。通过XRD和 SEM等检测手段对烧后试样的物相组成和微观结构进行测试与表征,重点研究Al₂O₃/SiO₂的加入对复相陶瓷物相组成、微观结构及烧结性能的影响。结果表明:随着Al₂O₃/SiO₂加入量的增大,试样烧后相对密度和烧后线变化率呈先增大后减小再增大的趋势,加入15%Al₂O₃/SiO₂(质量分数)的试样经1 500 ℃烧结后,其相对密度可以达到94%。引入的Al₂O₃/SiO₂与基体中的MgO生成镁铝尖晶石与镁橄榄石相,原位反应伴随的体积膨胀,抵消部分烧结过程中的体积收缩。Al₂O₃/SiO₂加入量为75%(质量分数)的试样经1 400 ℃烧结后,基体中有大量堇青石相生成,随着煅烧温度提高到1 500 ℃,堇青石分解所产生的高温液相促进了试样的烧结收缩。     

[Ru(bpy)2L](PF6)2 /Pt/TiO2光催化剂的合成及其可见光驱动分解水产氢性能研究

合成了一个新的光敏配合物[Ru(bpy)2L](PF6)2(RHIPB,L=2-羟-4-(1-氢咪唑并[4,5-f]1,10-邻菲罗啉)基苯甲酸),通过IR、MS、UV-Vis、SEM、XRD、CV等手段对目标化合物的结构和性质进行了表征。以RHIPB为光敏剂,制备了光催化剂6%RHIPB/0.5%Pt/TiO2(质量分数)(Ⅰ),系统考察并优化了目标光化剂的光催化分解水产氢性能。实验结果表明:在100mL含50mg复合光催化剂6%RHIPB/0.5%Pt/TiO2的水中,当牺牲剂TEOA浓度为5%(体积比),pH=5时,在可见光照射下,催化剂可持续产氢3h,平均产氢速率2578μmol·h-1·g-1。机理研究表明激发态的光敏剂分子RHIPB*可以将电子注入TiO2的导带,从而激发催化反应。