纳米棒状钡铁氧体的制备与吸波性能

以硝酸铁和硝酸钡为原料,采用溶胶-凝胶与自蔓延燃烧相结合的方法制备出纳米棒状钡铁氧体,采用X射线衍射仪、透射电镜与振动试样磁强计时其组成、形貌与磁性能进行了表征;将纳米棒状钡铁氧体掺入水泥基材料制成水泥基吸波材料,采用弓形反射法测其吸波性能.结果表明:纳米棒状钡铁氧体的平均粒径为40～60 nm,平均长度为100 nm,饱和磁场强度为49.87 A·m~2/kg,矫顽力为63.1 A/m;当纳米棒状钡铁氧体的掺量为1.83%(质量分数)、试样厚度为20 mm时,水泥基吸波材料在2～18 GHz频率范围内的最小反射率为-16.78 dB,反射率小于-10 dB的带宽为6 GHz.     

石膏填充蜂窝结构吸波材料的吸波性能

通过在浸渍乙炔炭黑的蜂窝结构中填充石膏,制备了具有蜂窝结构的石膏基吸波材料,采用弓形反射法研究了该吸波材料在2~18GHz的吸波性能.结果表明:蜂窝结构的孔格边长和高度对材料的吸波性能有一定影响;当石膏填充单层蜂窝结构吸波材料在2~18GHz频宽,蜂窝结构孔格边长为6mm,高度为8mm时,反射率低于-10dB的吸收频宽为10.4GHz;石膏填充双层蜂窝结构吸波材料,由于匹配层和吸收层形成了阻抗梯度结构,在一定程度上改善了其吸波性能,故能够在2~18GHz频宽内获得小于-8dB的吸波效率,反射率曲线存在5个吸收峰,在2.2GHz附近的吸收峰可达-20.3dB.     

铜渣对水泥砂浆性能的影响

本文简要介绍了铜渣的研究现状、主要化学组成和岩相特征,综述了铜渣在水泥领域中的应用对水泥砂浆性能的影响。铜渣中含有大量的2Fe O·Si O2和Fe3O4,可以作为吸波材料进行相关研究。铜渣的回收利用可以降低成本,保护环境,节约资源,具有广阔的应用前景和社会经济效应。     

多层孔洞泡沫水泥板夹电阻膜的吸波体吸波特性研究

针对目前水泥基吸波材料研究存在的问题,结合空间电磁波传播原理,在目前研究添加EPS的水泥基吸波材料基础上提出了一种多层孔洞结构型吸波材料设计思路;选用小颗粒EPS和以石墨及炭黑为主要原料制成的纯电阻膜为组分研究了EPS含量和电阻膜阻值组合对水泥基吸波材料吸波性能的影响;设计不同数量、位置和大小的孔洞,在2~18 GHz频段内制备出20 mm厚、吸波性能好(在4 GHz附近反射率最小达到-18.5 dB)、频带宽(反射率小于-10 dB的频带达15.5 GHz)的多层孔洞结构型吸波材料。     

角锥结构炭黑/水泥基复合材料的吸波性能研究

采用拱型反射率测试系统,研究了具有周期性角锥结构的炭黑/水泥基复合材料在1.7～18.0 GHz频段的电磁波吸收性能,讨论角锥尺度及材料基体对吸波性能的影响,利用HFSS软件对结果进行了仿真。结果表明,角锥结构可提高材料的吸波性能,角锥高度和炭黑掺量越大,吸波性能越好,且增大高度能使有效频带向低频段扩展,角锥高度40 mm,炭黑掺量1.5%时,实现99%吸收(-20 dB)电磁波的频带(3.1～18.0 GHz)扩展到S波段(2～4 GHz)。角锥结构改善吸波性能的机理是角锥结构可形成与自由空间阻抗匹配和椎体间多重反射,从而增大干涉损耗和内部介电损耗,同时引入散射和衍射损耗。     

三维界面特性双层水泥基材料的吸波性能研究

设计并制备了具有三维界面结构的双层水泥基吸波材料,利用弓形反射法研究了其在2～18 GHz频率范围内的电磁波吸收性能,研究了覆盖三维结构界面的透波层性质对吸波性能的影响.结果表明,三维界面结构设计能够显著提高水泥基材料的吸波性能、拓宽有效吸波带宽,具有尖劈界面结构的双层水泥基材料在2～18 GHz频率范围内电磁波反射率...     

蒸汽相水解法制备磁性光催化剂Fe_3O_4/SiO_2/TiO_2及其光催化性能

采用蒸汽相水解法,以Fe3O4纳米磁性颗粒为磁核,在其表面包覆一层SiO2来阻止光腐蚀,然后将锐钛矿相纳米氧化钛沉积在Fe3O4/SiO2颗粒表面,从而制得核壳结构的Fe3O4/SiO2/TiO2磁性复合光催化材料。用X射线粉末衍射仪(XRD)、场发射扫描电镜(FE-SEM)、高分辨率透射电子显微镜(HR-TEM)、探针式震动磁强计等手段对所制备的产物的结构、形貌、磁强度性能进行表征。以300W汞灯为光源,用亚甲基蓝和酸性红模拟污水中的有机染料来评价复合光催化剂的性能。结果表明,磁性纳米微球中TiO2的含量越大,其光催化性能越好,含TiO2质量分数50%的F3O4/SiO2/TiO2磁性纳米微球可在180min内降解亚甲基蓝模拟染料废水,降解率达99%,在80min内降解酸性模拟染料废水,降解率达98%。     

S带电磁污染控制用珍珠岩泡沫水泥吸波板的设计与制备

根据电磁波吸收原理,对建筑隔热材料进行功能化改造,通过λ/4模型设计和理论模拟分析,成功制备出珍珠岩泡沫水泥电磁波吸收板材。实验表明,2~4GHz频段,电阻膜采用380Ω/□,厚度为1.20cm的吸波板材,在3GHz附近有最大吸量-25dB,反射率在-10dB以下带宽达到65%;同样采用380Ω/□电阻膜,厚度为1.50cm的材料,成功实现了2.45GHz吸波材料的制备。新材料可用于无线局域网的电磁干扰防护及建筑室内电磁辐射污染控制。     

氧化沉淀法制备纳米Fe_3O_4及其类Fenton催化活性

通过化学氧化沉淀法制备出球形和八面体形貌的Fe3O4纳米颗粒,对其进行XRD、Raman和SEM等表征。以合成的纳米Fe3O4催化H2O2氧化降解橙黄Ⅱ,考察了不同形貌Fe3O4的类Fenton催化活性。结果表明:使用化学氧化沉淀法制备Fe3O4,在低pH(8⁹)条件下所得到的产物呈类球形,高pH(13)条件得到的产物为八面体形貌,其粒径均在210nm左右,并且结晶良好。Fe3O4/H2O2体系能有效降解橙黄II,并且催化反应主要发生在Fe3O4表面,最佳催化条件为pH 3.0、温度40℃。类球形Fe3O4纳米颗粒的催化活性高于八面体Fe3O4,并且Fe3O4具有良好的化学稳定性,重复使用4次效果稳定。     

频率选择表面对PET水泥基材料吸波性能的影响

为解决电磁环境污染问题,以废弃聚对苯二甲酸乙二酯(PET)塑料瓶碎片、聚丙烯纤维作为水泥基体的透波剂和增韧增强介质,在水泥基材料表面复合封闭式、开放式、组合式3组频率选择表面(FSS),制备了成本低、质量轻、厚度薄、强度高、加工工艺简单的FSS复合水泥基吸波平板试样.结果表明:FSS复合水泥基吸波平板试样在2~18GHz频段的吸波性能有了较大的改善,环数为1环的组合式复合试样在2.5GHz处的最小反射率为-19.9dB,-10dB以下的吸收带宽占了整个频段的47.5%;S频段(2~4GHz)内FSS单元尺寸和个数对复合试样吸波性能的影响规律与4~18GHz频段表现出不同的特性.     

晶硅切磨废弃硅粉为原料的反应烧结Si_3N_4结合SiC复相陶瓷的正交实验研究

以磨切单晶硅废料Si粉和SiC为原料,Y2O3-Al2O3-Fe2O3为复合烧结助剂,反应烧结法制备Si3N4/SiC复相陶瓷材料。运用L9(34)正交设计,研究了原料中Si、助剂Al2O3、Y2O3和Fe2O3的含量对陶瓷材料力学性能的影响和优化。采用X射线衍射(XRD)和扫描电镜(SEM)对复合材料的相组成、断口形貌进行分析。结果表明,反应烧结后试样生成Si3N4结合SiC晶粒为主相,及少量SiALON与未反应的Si相的烧结体。Si含量对力学性能的影响最为显著,对于抗弯强度性能,正交试验获得的工艺优化参数:ω(Si):20%、ω(Al2O3):3.2%、ω(Fe2O3):0.8%和ω(Y2O3):2%。     

瓷釉用棕色尖晶石颜料

ZnO-Fe2O3-Cr2O3系统是合成陶瓷工业用的大部分棕色颜料的基本三元系统。介绍了如下几种类型的棕色颜料的制备:1ZnFeCrO4,2ZnFeCrO4中部分ZnO被FeO或FeO+NiO置换,3ZnFeCrO4中部分Fe2O3、Cr2O3或Fe2O3+Cr2O4被Al2O3置换;借助X-射线衍射法和热分析,阐述了色料的形成和晶体结构;通过色釉试验,并参照色度测定的数据讨论了色料的组成与结构对色釉颜色的影响。     

亚硝酸盐对含氯盐砂浆内钢筋钝化膜组成的影响

采用X射线光电能谱仪(XPS)研究了NaNO_2对含氯盐砂浆内钢筋钝化膜微结构的影响,阐明了亚硝酸盐阻锈作用下砂浆内钢筋钝化膜的微结构变化规律及其特征.研究结果表明:NaNO_2在碱性环境下与Fe元素反应生成中间产物Na_2FeO_2和(NaFeO_2)_2,进一步促进Fe_3O_4的生成,提高了阻锈效果;NaNO_2的掺入促进了反应式向正向移动,提高了钝化膜中Fe_3O_4的含量;当普通碳钢钝化膜内5nm处Fe~(3+)/Fe~(2+)的百分比大于表层的Fe~(3+)/Fe~(2+)百分比时,钝化膜内部的致密性优于表面.NaNO_2不参与钝化膜的组成,但参与生成钝化膜的反应过程,该反应过程为缓慢的动态平衡过程,可通过改变反应物的含量控制钝化膜厚度.     

Fe2O3有机物光催化降解有机染料的研究进展

探讨了Fe2O3/H2O2体系在可见光下降解有机染料的研究进展,采用Fe2O3/H2O2体系,对大红4BS、甲基橙等染料进行了光氧化降解实验,得出Fe2O3/H2O2/太阳光体系和Fe2O3/H2O2/UV体系在不同pH值条件下的光降解效率。     

Profiling iron corrosion coating on iron grains in a zerovalent iron system under the influence of dissolved oxygen

Rapid oxidation of Fe(0) by O(2) occurred when Fe(0) grains were bathed in 0.54 mM FeCl(2) solution saturated with dissolved oxygen (DO), forming a substantial corrosion coating on Fe(0) grains. A sonication method was developed to strip the corrosion coating off the iron grains layer by layer. The transformation of the constituents and the morphology of the corrosion coating along its depth and over reaction time were investigated with composition analysis, X-ray diffraction and scanning electron microscopy. Results indicate that the sonication method could consistently recover >90% iron oxides produced by the Fe(0)-DO redox reaction. Magnetite (Fe(3)O(4)) and lepidocrocite (gamma-FeOOH) were identified as the corrosion products. Initially, lepidocrocite was the preferential product in the presence of DO. As the oxide coating thickened, the inner layer transformed to magnetite, which retained as the only stable corrosion product once DO was depleted. The study confirms the phase transformations between gamma-FeOOH and Fe(3)O(4) within a stratified corrosion coating. The sonication technique exemplifies a new approach for investigating more complicated processes in Fe(0)/oxides/contaminants systems.     

Photodegradation of 2,4-dichlorophenoxyacetic acid in various iron-mediated oxidation systems

The oxidation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) by different iron-mediated processes, with or without the presence of ultraviolet (at 253.7 nm) and oxalate, was investigated and compared. The initial decay rate and the overall removal percentage were used as the performance indexes. To extensively explore the associated processes, the following combinations or blank systems were investigated: UV radiation only, Fe(2+)/H(2)O(2), Fe(2+)/H(2)O(2)/UV, ferrous oxalate/H(2)O(2), ferrous oxalate/H(2)O(2)/UV, Fe(3+)/H(2)O(2), Fe(3+)/H(2)O(2)/UV, ferrioxalate/H(2)O(2), and ferrioxalate/H(2)O(2)/UV. This study showed that the degradation of 2,4-D by sole UV or dark processes (without UV) is generally slow, except by the conventional Fenton's process (Fe(2+)/H(2)O(2)). However, these slow reactions can be accelerated by exposure to UV irradiation, which can increase the initial 2,4-D decay rate from ten to more than one hundred times. Furthermore, if the reaction is initiated by ferrous oxalate or ferrioxalate instead of Fe(2+) or Fe(3+) ions, the rates can be further improved, because of the higher light sensitivity of the organometallic complexes. These reactions were also found sensitive to the initial hydrogen peroxide concentration. The competition of hydroxyl free radicals by the primary intermediate, 2,4-dichlorophenol, was also observed.     

Effect of precursor concentration on the characteristics of nanoscale zerovalent iron and its reactivity of nitrate

Differing precursor concentrations, 1.0, 0.1, and 0.01 M FeCl(3) x 6H(2)O, were performed to produce nanoscale Fe(0) and the results were discussed in terms of the specific surface area, particle size and electrochemical properties. The results indicated that the nanoscale Fe(0) prepared by 0.01 M FeCl(3) had absolutely reduced in size (9-10nm) and possessed the greatest specific surface area (56.67 m(2) g(-1)). These synthesized nanoscale Fe(0) particles were attempted to enhance the removal of 40 mg-NL(-1) unbuffered nitrate solution. The first-order degradation rate constants (k(obs)) increased significantly (5.5-8.6 times) with nanoscale Fe(0) prepared by 0.01 M precursor solution (Fe(0.01 M)(0)). When normalized to iron surface area concentration, the specific rate constant (k(SA)) was increased by a factor of approximately 1.7-2.4 using Fe(0.01 M)(0) (6.84 x 10(-4) L min(-1) m(-2) for Fe(0.01 M)(0), 4.04 x 10(-4) L min(-1) m(-2) for Fe(0.1 M)(0) and 2.80 x 10(-4) L min(-1) m(-2) for Fe(1 M)(0)). The rise of reactivity of the reactive site on the Fe(0.01 M)(0) surface was indicated by the specific rate constant (k(SA)) calculation and the i(0) value of the electrochemical test.     

吸声组分对陶粒多孔混凝土性能的影响

以轻质陶粒、水泥等为主要原料,采用混凝土成型法成型,制备了一种防火型多孔陶粒混凝土吸声材料.掺入了发泡剂、膨胀珍珠岩及聚丙烯纤维3种吸声组分来改善吸声材料的孔隙状况,通过试验分析了这3种吸声组分对材料吸声性能和力学性能的影响.结果表明:添加这3种吸声组分都能较大程度地提高材料的吸声性能,其中聚丙烯纤维能同时提高材料的抗压强度,而膨胀珍珠岩和发泡剂却明显降低了材料的抗压强度;通过扫描电镜SEM进行了微观分析讨论,并建立起了材料孔隙状况和不同频率段吸声性能的联系.     

Reduction of nitrobenzene and formation of corrosion coatings in zerovalent iron systems

Batch tests were conducted to investigate reduction of nitrobenzene in a zerovalent iron system (Fe0) under various conditions. The results indicated that a limited amount of nitrobenzene (ArNO2) could be reduced to aniline by Fe0, but formation of a lepidocrocite (gamma-FeOOH) coating could significantly slow down the reaction. However, augmenting Fe0 with substoichiometric FeCl2 could dramatically accelerate the reaction. Surface-adsorbed Fe(II), not pH nor Cl-, was found to be responsible for rejuvenating the system. O2 and nitrobenzene could be concomitantly reduced by Fe0 in the presence of Fe2+. In the Fe0 system, both nitrobenzene and O2 favored formation of lepidocrocite; in the presence of aq. Fe(II), a stratified corrosion coating could develop, with magnetite (Fe3O4) as the inner layer and lepidocrocite as the outer layer. Fe2+ was not the main reductant for the reactions, but might accelerate the autoreduction of lepidocrocite to magnetite by the underlying Fe0. Our understanding on the role of Fe(II) in conjunction with a stratified, evolving corrosion coating may be useful for establishing an iron aquatic corrosion model.     

B2O3对锂铝硅系光敏微晶玻璃介电性能的影响

通过研究不同B2O3含量的光敏微晶玻璃,获得了介电常数最小值为5.1和介电损耗达到最小值为5.7×10-3(1GHz)的光敏玻璃样品,分别对应B2O3含量为2wt%和0。通过红外光谱分析发现,B2O3以[BO3]式进入玻璃硅氧网络,会一定程度破坏网络结构,链状的[BO3]使玻璃网络变得更加疏松,最终导致玻璃的介电常数和介电损耗上升,介电性能下降。为提高玻璃的介电性能,降低介电损耗,应尽量避免硼元素的引入。