Gelatin/BaTiO3核壳复合粒子的制备及电场响应性能研究

以平均粒径为0.7~0.9 mm的明胶(Gelatin)微球为基核, 通过定向沉积自组装法成功制备了以Gelatin为核、BaTiO₃为壳的Gelatin/BaTiO₃核壳复合粒子。利用TEM、XRD、FT-IR、TG和光学接触角测量等技术对复合粒子的形貌、结构、组成及表面亲水性能进行了研究。结果表明, 复合粒子为球形微粒, 具有良好的表面亲水性和分散稳定性, BaTiO₃壳层约占粒子总质量的18.8%, 具有立方相晶相结构。将粒子分散到水凝胶弹性体中, 测量在有/无电场作用下得到的弹性体的储能模量, 借以考察复合粒子在弹性体中的电场响应性能, 发现Gelatin/BaTiO₃复合粒子的电场响应性能明显强于纯BaTiO₃粒子。说明将BaTiO₃包覆在聚合物上能显著提高BaTiO₃粒子的电场响应性能。     

二次化学共沉淀法制备片状钡铁氧体的形成历程及磁性能研究

采用二次化学共沉淀法制备出六角或近六角片状BaFe₁₂O₁₉,其颗粒径向尺寸和径厚比分别为0.4-2μm和4-20。通过XRD、FTIR、TG/DTA及SEM/EDS分析技术研究了片状BaFe₁₂O₁₉的形成历程。结果表明:前驱体为非晶态BaCO₃、低结晶态Fe（OH）₃和晶态α-Fe₂O₃包覆原料BaFe₁₂O₁₉复合物;前驱体在焙烧过程中经过Fe（OH）₃脱水、BaCO₃分解反应、中间相α-Fe₂O₃和BaO反应得到终产物BaFe₁₂O₁₉。基于形成历程,六角片状BaFe₁₂O₁₉较原料BaFe₁₂O₁₉表现出显著提高的颗粒径向尺寸和径厚比、较高的纯度和略低的结晶有序程度,进而表现出明显提高的矫顽力、略低的饱和磁化强度和剩余磁化强度。     

单壁碳纳米管/六角钡铁氧体复合材料的微波吸收性能

用电弧法制备含铁的单壁碳纳米管(SWCNTs), 并将其提纯之后掺杂到用溶胶-凝胶自燃法制备的M型六角钡铁氧体(BaFe₁₂O₁₉)纳米晶粉体中, 得到了具有网状结构的复合材料。利用同轴法测试了样品的电磁参数, 研究了不同混合比SWCNTs/BaFe₁₂O₁₉ 复合材料的吸波性能。结果表明: 复合粉体SWCNTs/BaFe₁₂O₁₉的磁损耗主要是由于自然共振和交换共振引起的; 当掺杂2%(质量分数)SWCNTs时, 微波反射衰减最大值可以达到 24.85 dB, 高于10 dB的频带宽度可以达到6.30 GHz, 具有较宽的吸波频段。      

核壳结构SrFe12O19NiFe2O4复合纳米粉体的吸波性能

以Fe(NO₃)₃、 Ni(NO₃)₂和Sr(NO₃)₂为主要原料, 通过两步柠檬酸盐溶胶-凝胶法, 制备出核-壳结构SrFe₁₂O₁₉-NiFe₂O₄磁性纳米复合粉体。采用XRD、 TEM、 VSM及矢量网络分析仪对合成的粉体的结构、 形貌及吸波性能进行了分析研究。结果表明, 复合粉体的相结构与NiFe₂O₄含量有关, 当SrFe₁₂O₁₉与NiFe₂O₄的质量比为1∶2、 烧结温度为1050℃时, 复合纳米粉体的相与NiFe₂O₄接近, 核-壳结构SrFe₁₂O₁₉-NiFe₂O₄纳米复合粉体的饱和磁化强度(M_s)(51.4 emu/g)比单体SrFe₁₂O₁₉纳米粉体 (42.6 emu/g)的大; 但矫顽力(H_c) (336 Oe)比单体SrFe₁₂O₁₉纳米粉体的小, 在SrFe₁₂O₁₉ 与NiFe₂O₄的矫顽力5395～160 Oe之间。在频率为8～18 GHz范围内, 微波吸收逐渐增强, 当频率为12 GHz时, SrFe₁₂O₁₉-NiFe₂O₄纳米复合粉体的微波吸收达到最大值-9.7 dB, 是一种性能优良的吸波材料。      

CoFe2O4-Co3Fe7纳米粒子及CoFe2O4/多孔碳的制备及其电磁性能研究

在5% H₂+95% N₂气氛下,还原CoFe₂O₄纳米粒子制备了CoFe₂O₄-Co₃Fe₇纳米粒子;以焙烧黄麻纤维得到的多孔碳纤维为碳源用水热法将CoFe₂O₄纳米粒子负载到多孔碳中,制备出CoFe₂O₄/多孔碳。使用X射线衍射仪、扫描电子显微镜、透射电子显微镜、拉曼光谱仪、同步热分析仪等手段对材料进行表征,并使用矢量网络分析仪测量了复合材料的电磁参数和微波吸收性能。结果表明,CoFe₂O₄-Co₃Fe₇纳米粒子和CoFe₂O₄/多孔碳的微波吸收性能明显优于CoFe₂O₄纳米粒子。CoFe₂O₄-Co₃Fe₇纳米粒子的有效频宽(反射损耗<-10 dB的频率宽度)可达4.8 GHz。CoFe₂O₄/多孔碳的有效频宽可达6 GHz,覆盖了整个Ku波段(12~18 GHz)。这些材料优异的微波吸收性能,可归因于合适的介电常数、大的介电损耗、多孔结构以及介电损耗和磁损耗的协同作用。     

BaFe12O19/SiO2-B2O3-K2O 微晶玻璃陶瓷的低温合成及其微波性能

采用柠檬酸sol-gel工艺合成了BaFe₁₂O₁₉/SiO₂-B₂O₃-K₂O微晶玻璃陶瓷, 并对其介电常数及其磁导率在100MHz～ 6 GHz 下的变化规律进行了研究。结果表明: BaFe₁₂O₁₉/SiO₂-B₂O₃-K₂O微晶玻璃陶瓷可以在850℃/5 h的条件下烧结而成, 其合成过程与体系中的Ba/Fe 密切相关; 其介电常数基本不随测试频率的变化而变化; 其磁导率实部随测试频率的增加而下降。      

纳米Fe3O4及Fe3O4-SrFe12O19吸波复合材料的制备及性能

采用共沉淀法成功制备出具有超顺磁性的纳米Fe₃O₄, 并将Fe₃O₄与SrFe₁₂O₁₉复合制成复合吸波材料Fe₃O₄-SrFe₁₂O₁₉, 利用X射线衍射仪(XRD)、透射电镜(TEM)、振动样品磁强计(VSM)和矢量网络分析仪(PNA)对产物的物相、显微结构、磁性能和吸波性能进行了表征与分析。结果表明, 当Fe₃O₄与SrFe₁₂O₁₉质量比为1∶0.3时, Fe₃O₄-SrFe₁₂O₁₉饱和磁化强度为11.1 emu·g^-1, 矫顽力0.86 Oe, 剩余磁化强度0.08 emu·g^-1, 其吸波性能最佳, 最大吸收峰值为-17.7 dB,-5 dB频宽为1.3 GHz, 较Fe₃O₄和 SrFe₁₂O₁₉的最大吸收峰值分别提高247%和185%, 频带分别拓宽1.12 GHz和0.40 GHz。     

自组装法制备磺化聚苯乙烯@Fe3O4磁性复合颗粒及其磁性能

实现结构可控、均匀包覆是制备核-壳复合材料的关键。采用离子交换法完成了磺化聚苯乙烯(PSS)表面Na+与溶液中Fe2+和Fe3+的交换,于碱性条件下制备了PSS表面负载Fe₃O₄(PSS@Fe₃O₄)的磁性复合颗粒。通过称重法计算了Fe₃O₄最大包覆率;通过振动样品磁强计(VSM)测试了不同负载含量下PSS@Fe₃O₄复合颗粒的磁性能;通过XRD、衰减全反射-FTIR (ATR-FTIR)、SEM-EDS分析了PSS@Fe₃O₄磁性复合颗粒的化学组成和微观结构。结果表明,随着Fe2+/Fe3+浓度增加,PSS@Fe₃O₄磁性颗粒的饱和磁化强度也随之增大,最大饱和磁化强度为7.51 emu/g,并具有明显的磁响应性;Fe₃O₄均匀包覆在PSS表面,最大包覆率为8.3 wt%。PSS@Fe₃O₄磁性复合颗粒有望用于磁流变、医学及水处理领域。      

Fe3O4/ 聚吡咯复合材料的制备及表征

以化学沉淀法制备Fe₃O₄ 纳米粒子, 采用乙醇对Fe₃O₄ 纳米粒子表面进行处理, 使其表面有机化, 然后通过乳液原位复合制备Fe₃O₄ / 聚吡咯复合材料。利用TEM, XPS, 四探针测试仪和震荡磁力计对其进行表征和检测。结果表明: 经醇处理的Fe₃O₄ 纳米粒子的分散性得到明显改善, Fe₃O₄ 纳米粒子被包覆在聚吡咯层内, 包覆层厚度为10 nm 左右, 复合材料具有优良的电性能和磁性能, 电导率e= 7. 69 s/ cm～13. 6 s/ cm, 饱和磁强度M_s= 12. 06 emu/ g～24. 38 emu/ g, 矫顽力H_c= 11 Oe～41 Oe。其环境稳定性明显优于纯聚吡咯。      

低损耗ZrTi2O6填充PTFE复合基板性能

采用热压成型工艺,制备了一种低损耗ZrTi₂O₆陶瓷填充聚四氟乙烯（PTFE）的新型微波复合基板材料。采用介质谐振器法研究了ZrTi₂O₆/PTFE复合材料的微波介电性能（8~12 GHz）。结果表明,ZrTi₂O₆/PTFE复合材料的相对介电常数（ε _r）和介电损耗（tanδ）随着ZrTi₂O₆陶瓷体积分数（0~46%）的增加而增大,介电常数实验值与Lichtenecker模型预测值最吻合。ZrTi₂O₆/PTFE复合材料的热膨胀系数和介电常数温度系数随着ZrTi₂O₆陶瓷体积分数的增加而减小。46%的ZrTi₂O₆为较优填料比例,ZrTi₂O₆/PTFE的相对介电常数为7.42,介电损耗为0.0022（10 GHz）。     

Magnetic and Photocatalytic Activity of Pure BaFe12O19 and BaFe12O19-TiO2 Hexagonal Ferrite Nanocomposites

Journal of Superconductivity and Novel Magnetism - Hard hexagonal barium ferrite BaFe12O19 (BaM), as well as core–shell structure BaFe12O19-TiO2 composite nanoparticles, was successfully...     

凝胶法制备Ba铁氧体的微观形态及磁性能

用溶胶-凝胶技术制备六角晶系BaFe12O19铁氧体超微粉末,采用热分析技术和XRD技术分析了其形成规律,运用扫描探针显微镜分析其微观形态,并测定了常温磁性能。结果表明：BaFe2O4和BaFe12O19的转变温度分别为414．55℃、755．78℃;800℃处理后得到的BaFe12O19超微粉末呈三种不同的形态,分别为圆形、带孔洞的圆形和圆环形;平均粒径为450nm左右;其厚度小于其直径;1000℃处理后的样品完全是BaFe12O19结构,其ds小于粗晶BaFe12O19铁氧体,而Hc大于粗晶肪BaFe12O19铁氧体。     

BaFe12O19／Al2O3—SiO2—K2O微晶玻璃陶瓷的柠檬酸Sol—Gel合成及其微波性能的研究

采用柠檬酸sol-gel工艺合成了BaFe12O19/Al2O3-SiO2-K2O微晶玻璃陶瓷，并对其介电常数及其磁导率在1MHz～6GHz下的变化规律进行了研究。结果表明，BaFe12O19/Al2O3-SiO2-K2O微晶玻璃陶瓷的合成与体系中Fe/Ba、烧结温度密切相关；其介电常数、磁导率基本都随测试频率的增加而下降；介电损耗值最大可达到0.30，磁损耗值较小。     

丝网印刷制备钡铁氧体永磁厚膜的研究

采用丝网印刷方法制备钡铁氧体永磁厚膜,研究了热压烧结对钡铁氧体厚膜性能的影响.XRD结果表明,在常压烧结和热压烧结的样品中均有明显的BaFe12O19衍射峰.与常压烧结相比,热压烧结的样品表面孔洞明显减少,致密性得到了很大的提高.并且热压烧结的样品磁性能也有明显的提高,其剩磁比可达0.71,矫顽力达到304.1kA/m,而常压烧结样品剩磁比和矫顽力仅为0.51和278.8kA/m.     

粒度对纳米掺杂BaTiO3陶瓷结构和性能的影响

制备了纳米掺杂BaTiO3陶瓷,研究了纳米掺杂剂和BaTiO3的粒度对BaTiO3陶瓷的微观结构和介电性能的影响．结果表明,小粒度、高分散的纳米掺杂剂更易对BaTiO3颗粒实现均匀包裹,有效地抑制晶粒生长并形成更多的壳-芯晶粒,大比表面积使更多高活性的表面原子与BaTiO3发生原子输运形成传质,导致晶粒壳／芯比增大,从而提高其介电性能．纳米掺杂陶瓷的平均晶粒尺寸和四方率与BaTiO3粒度几乎成正比．随着BaTiO3粒度的减小,立方晶粒壳增大而四方晶粒芯减小,陶瓷由四方晶相向赝立方晶相转变,居里峰被显著压制,从而改善介电温度特性．同时,晶粒的壳与芯之间失配产生的内应力随之增加,使居里点向高温方向移动．     

A facile synthesis of Cu(2)O/SiO(2) and Cu/SiO(2) core-shell octahedral nanocomposites

We report here a simple approach to the synthesis of Cu(2)O/SiO(2) core-shell nanocomposites in water solution. The Cu(2)O cores have a perfect octahedral structure with uniform size of about 200-300?nm. A compact SiO(2) shell 9?nm in thickness is located at the surfaces of Cu(2)O octahedra, and it is composed of fine SiO(2) nanoparticles. During the depositing of the SiO(2) particles, as we presumed, dynamic absorbing and disengaging of Na(+) at the interface of Cu(2)O octahedra and the solution made it possible for the formation of Cu-O-Si bonds between core and shell in the composites. The existence of Cu-O-Si bonds in our core-shell composite can be substantiated by peak changes at?1236 and 1080?cm(-1) in the FT-IR spectra. This is the reason why the SiO(2) shell is so compact and uniform. Moreover, these Cu(2)O/SiO(2) core-shell octahedra were further used as precursors, depending on a simple disproportionation reaction of Cu(2)O in acid, to easily achieve Cu/SiO(2) movable multicore-shell octahedral nanocomposites. In the final Cu/SiO(2) core-shell composite, the thin SiO(2) octahedral shell was held, inside of which formed several free Cu nanoparticles 50-80?nm in size. Studies on the Cu(2)O/SiO(2) core-shell octahedral composites and Cu/SiO(2) movable multicore-shell octahedral nanocomposites would be a good thing not only for fundamental research but also for applications.     

Synthesis and characterization of SiO2/(PMMA/Fe3O4) magnetic nanocomposites

Magnetic silica nanocomposites (magnetic nanoparticles core coated by silica shell) have the wide promising applications in the biomedical field and usually been prepared based on the famous St?ber process. However, the flocculation of Fe3O4 nanoparticles easily occurs during the silica coating, which limits the amount of magnetic silica particles produced in the St?ber process. In this paper, PMMA/Fe3O4 nanoparticles were used in the St?ber process instead of the "nude" Fe3O4 nanoparticles. And coating Fe3O4 with PMMA polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. The results show that the critical concentration of magnetic nanoparticles can increase from 12 mg/L for "nude" Fe3O4 nanoparticles to 3 g/L for PMMA/Fe3O4 nanoparticles during the St?ber process. And before the deposition of silica shell, the surface of PMMA/FeO4 nanoparticles had to be further modified by hydrolyzing them in CH3OH/NH3 x H2O mixture solution, which provides the carboxyl groups on their surface to react further with the silanol groups of silicic acid.     

Fe3O4/TiO2 core/shell nanoparticles as affinity probes for the analysis of phosphopeptides using TiO2 surface-assisted laser desorption/ionization mass spectrometry

Columns packed with microsized titanium dioxide particles have been used effectively as precolumns for enriching phosphopeptides from complex mixtures. Nanosized titanium dioxide particles have a higher specific surface area and, hence, potentially higher trapping capacities toward phosphopeptides than do microsized particles. Thus, in this study, we employed TiO2-coated magnetic (Fe3O4/TiO2 core/shell) nanoparticles to selectively concentrate phosphopeptides from protein digest products. Because of their magnetic properties, the Fe3O4/TiO2 core/shell nanoparticles that are conjugated to the target peptides can be isolated readily from the sample solutions by employing a magnetic field. In this paper, we also demonstrate that the Fe3O4/TiO2 core/shell nanoparticles behave as an effective SALDI matrix: our upper detectable mass limit was approximately 24 000 Da, whereas the detection limit for peptides was in the low-femtomole range. That is to say, the target analytes trapped by the Fe3O4/TiO2 nanoparticles can be identified by introducing the particles directly into the mass spectrometer for TiO2-SALDI-MS analysis without the need for any further treatment. For example, elution steps are not necessary when using this approach. In addition, the trapping selectivity of these Fe3O4/TiO2 nanoparticles toward phosphopeptides was quite good. These properties combine to result in the low detection limits. The lowest detectable concentration of phosphopeptides that we analyzed using this approach was 500 pM for a 100-microL tryptic digest solution of beta-casein; this level is much lower than that which can be obtained using any other currently available method.