ZnO纳米粉体的液相掺杂制备策略与应用

【目的】探讨制备结构形貌可控、导电性良好的ZnO纳米粉体策略。【研究现状】掺杂ZnO纳米粉体的液相制备策略,包括两步合成法前驱体转化和一步合成法原位掺杂,两步合成法包括沉淀法、溶胶‒凝胶法、恒流电解法等,一步合成法包括高压加热法、常压加热法等;总结ZnO纳米粉体掺杂导电机制,以及ZnO纳米粉体在透明导电氧化物膜、抗静电复合材料、防静电热控涂层方面的应用。【结论与展望】认为离子掺杂已成为调控晶体材料性能的有效手段,通过有效的掺杂可以对材料的性能进行连续地调控,从而获得适应具体应用场景的高性能材料;提出导电掺杂能拓宽ZnO应用,应探索制备大批量ZnO纳米粉体材料的液相掺杂策略,形成液相路线对于ZnO纳米颗粒的形貌和导电性的可调,提高液相法杂质离子的掺杂效率、掺杂均匀性及批次稳定性,形成分子乃至原子层面对于液相合成过程和掺杂元素分布的有效分析手段,深入探讨合成和掺杂机制。

Measurement of Atrazine Adsorption onto Surficial Sediments(Natural Surface Coatings)——New Evidence for the Importance of Fe Oxides

To reveal the relative contribution of the components, Fe, Mn oxides or organic materials（OMs） in the surficial sediments（SSs）, and the natural surface coating samples（NSCSs） to adsorbing atrazine（AT）, a selective chemical extraction technique was employed, to remove the different components, and the adsorption characteristics of AT on the SSs and the NSCSs were investigated. The observed adsorptions of AT on the original and extracted SSs and NSCSs were analyzed by nonlinear least squares fitting（NLSF） to estimate the relative contribution of the components. The results showed that the maximum adsorption of AT on the NSCSs was greater than that in the SSs, before and after extraction treatments, implying that the NSCSs were more dominant than the SSs for organic pollutant adsorption. It was also found that the Fe oxides, OMs, and residues in SSs（NSCSs） facilitated the adsorption of AT, but Mn oxides directly or indirectly restrained the interaction of AT with SSs（NSCSs） particles. The contribution of the Fe oxides to AT adsorption was more than that of OMs; the greatest contribution to AT adsorption on a molar basis was from the Fe oxides in the nonresidual fractions, indicating that the Fe oxides played an important role in controlling the environmental behavior of AT in an aquatic environment.

Microstructure,tribological behavior and magnetic properties of Fe−Ni−TiO_(2) composite coatings synthesized via pulse frequency variation

The Fe−Ni−TiO_(2) nanocomposite coatings were electrodeposited by pulse frequency variation.The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies.By increasing the pulse frequency from 10 to 500 Hz,the iron and TiO_(2) nanoparticles contents were increased in expense of nickel content.XRD patterns showed that by increasing the frequency to 500 Hz,an enhancement of BCC phase was observed and the grain size of deposits was reduced to 35 nm.The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO_(2) nanoparticles into the Fe−Ni matrix(5.13 wt.%).Moreover,the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.

热处理对Fe-Al渗层组织结构及其熔融氯化盐腐蚀性能的影响

目的探索热扩散处理温度对Fe-Al渗层组织结构的影响,研究其在熔融氯化盐中的腐蚀性,为310S不锈钢在光热发电氯化盐储热领域的应用提供技术方案。方法使用77%Al_(2)O_(3)+20%Al+3%AlCl_(3)(质量分数)渗铝剂在310S钢表面制备Fe-Al涂层,并通过750~950℃热扩散处理30 h,改善渗层的结构及物相组成;在800℃三元共晶熔融氯化盐浸泡30 h,评价不同热扩散处理温度对渗铝层耐腐蚀性的影响。采用XRD、SEM、EDS等分析腐蚀前后渗层微观结构、物相组成,以及截面形貌和元素分布。结果800℃保温15h在310S钢表面制备了140μm厚的渗铝层,通过热扩散处理发现,温度对渗层结构及物相组成具有较大的影响。800℃以下热扩散处理渗层结构及组成基本没有变化,外层主要以Fe2Al5相为主,过渡层为FeAl相,腐蚀后表面未形成连续的氧化层。850℃处理渗层截面中间层出现了大量不规则孔洞,腐蚀后表面形成厚度约为15μm的Al_(2)O_(3)层,对渗层起到了一定的保护作用,但氧化层与渗层界面结合不紧密,容易脱落。900℃热处理渗层物相均转化为FeAl相,与基体结合界面形成厚度约为30.4μm的互扩散区;腐蚀后渗层表面形成厚度约为32μm的Al_(2)O_(3)层,且无裂纹、孔洞,与渗层结合良好,耐腐蚀性能最佳。950℃处理渗层腐蚀后表面未形成氧化层,出现了54μm的沿晶腐蚀深度。结论310S钢表面渗铝层经900℃热扩散处理后,在熔融氯化盐腐蚀环境中形成了连续、致密的Al_(2)O_(3)层,展现出了良好的耐腐蚀性能。

Formation and corrosion behavior of Fe-based amorphous metallic coatings prepared by detonation gun spraying

Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of thermally sprayed deposits with the porosity below 2%. Both crystallization and oxidation occurred obviously during spraying process, so that the amorphous fraction of the coatings decreased to 54% compared with fully amorphous alloy ribbons of the same component. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings exhibit extremely wide passive region and low passive current density in 3.5% NaCl (mass fraction) and 1 mol/L HCl solutions, which illustrates excellent ability to resist localized corrosion.

Synthesis and Deposition of TiC-Fe Coatings by Oxygen-acetylene Flame Spraying

A simpler and more convenient method for producing wear-resistant, TiC-reinforced coatings were investigated in this study. It consists of the simultaneous synthesis and deposition of TiC-Fe materials by oxyacetylene flame spraying. Solid reagents bound together to form a single particle are injected into the flame stream where an in-situ reaction occurs. The reaction products are propelled onto a substrate to form a coating. Microstructural analyses reveal that TiC and Fe are the dominant phases in the coatings. The reaction between Ti and C happens step by step along with the reactive spray powder flight, and TiC-Fe materials were mainly synthesized where the spray distance is 125-170 mm. The TiC-Fe coatings are composed of alternate TiC-rich and TiC-poor lamellae with different microhardness of 11.9-13.7 and 3.0-6.0 GPa, respectively. Submicron and round TiC particles are dispersed within a ductile metal matrix. The peculiar microstructure is thought to be responsible for its good wear resistance, which is better nearly five times than WC-reinforced cermet coatings obtained by traditional oxyacetylene flame spray.

Wear and corrosion resistance of laser-cladded Fe-based composite coatings on AISI 4130 steel

The wear and corrosion resistance of Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） and Fe_（77.3）Cr_（15.8）Ni_（3.9）Mo_（1.1）Mn_（0.5）C_（0.2）Si_（1.2） coatings laser-cladded on AISI 4130 steel were studied.The coatings possess excellent wear and corrosion resistance despite the absence of expensive yttrium,tungsten,and cobalt and very little molybdenum.The microstructure mainly consists of dendrites and eutectic phases,such as duplex（γ＋α）-Fe and the Fe–Cr（Ni）solid solution,confirmed via energy dispersive spectrometry and X-ray diffraction.The cladded Fe-based coatings have lower coefficients of friction,and narrower and shallower wear tracks than the substrate without the cladding,and the main wear mechanism is mild abrasive wear.Electrochemical test results suggest that the soft Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） coating with high Cr and Ni concentrations has high passivation resistance,low corrosion current,and positive corrosion potential,providing a better protective barrier layer to the AISI 4130 steel against corrosion.

Fe复合ZnO催化剂制备及其光催化固氮性能研究

本文以ZnSO4·7H2O与FeSO4·7H2O为原料采用沉淀还原法制备了不同含量Fe复合ZnO催化剂。通过X射线衍射仪(XRD)、紫外–可见漫反射(UV-Vis)和电化学组抗图、肖特基等表征手段对催化剂的物相、吸光特性、光生电子电阻和移动性能等进行了研究。研究结果发现随Fe含量的增加,复合ZnO催化剂光吸收强度逐渐增加,能带间隙逐渐减小,光生电子转移阻力减小,移动速度增加,光生电子空穴发生复合率降低,越容易活化氮分子与氢离子生成铵离子,复合ZnO催化剂光催化固氮性能逐渐升高。当Zn与Fe物质的量比为4:6,干燥温度为90℃时,制备的Fe复合ZnO催化剂固氮性能最好,NH4 浓度达到了12.8175 μg·gcat−1。

Effect of Fe content on microstructure and mechanical properties of Cu-Fe-based composite coatings by laser induction hybrid rapid cladding

To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.

MICROSTRUCTURAL STUDY OF Fe-Cr-Al/Al COMPOSITE COATINGS DURING OXIDATION AND SULFIDATION AT 900℃

The microstructure of a composite coating system, which was composed of an inner layer of Fe-Cr-Al and an outer layer of aluminum, was studied after it was respectively oxidized and sulfurdized at elevated temperatures. Apart from the Al2O3 scale formed on the surface, the microstructure of the composite coatings exposed at 900℃ in air for 4h was a three-layer structure. The first layer consisted of a solid solution of Cr and Fe in α aluminum and an intermetallic compound FeAl3 while the second layer was a single phase of the aluminide and the third layer still remained the same appearance as the original Fe-Cr-Al coating. The microstructural observation of the specimen tested at 850-900℃ at low oxygen pressure and high sulfur pressure for 576h revealed that the surface coatings of the specimen had transformed into a duplex structure containing an outer layer and a thicker aluminide layer beneath. X-ray diffraction results showed that the out layer was composed of Al2S3 and Al2O3 and that AlCrFee was the main phase composition of the aluminide layer, with a few of Al2S3 and Al2O3 accompanied.

Oxidation Performance of Fe-Al/WC Composite Coatings Produced by High Velocity Arc Sprayed at 650 ℃

The Fe-Al/WC intermetallic composite coatings have been prepared by high velocity arc spraying(HVAS) technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings has been studied by means of thermogrativmetic analyzer. The results demonstrate that the kinetics curve of oxidation approximately follows the logarithmic law. The composition of the oxidized coating surface mainly is composed of A12O3, Fe2O3, Fe3O4 and FeO which distribute unevenly. The protective A12O3 film firstly forms and preserves the coatings from further oxidation.

High temperature behaviors of high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

Fe-Al/Cr3C2 composite coatings were manufactured using high velocity arc spraying （HVAS） technology. The high temperature erosion, wear and corrosion resistance of the coatings were investigated. The coating properties such as bonding strength, porosity, hardness as well as microstructures were characterized. The results show that the coatings have relatively high heat tremble bond strength, hardness, and typical layer-shaped coatings＇ microstructures. With the rise of temperature, the coating erosion resistance increases too; the impingement angel does effects on erosion properties, and the erosion mechanism changes from ductile to brittle behaviors at 450℃. The coatings have good room temperature wear resistance and relatively good high temperature resistance. The wear mechanism of the coatings is peeling wear behavior. The coatings have excellent high temperature corrosion resistance because of the produce of oxides during corrosion.

Fe-Cr-Y_2O_3 MICRO-CRYSTALLINE COATINGS DEPOSITED BY SERIES ELECTRO-PULSE DISCHARGE

A new technique-series electro-pulse discharge (SEPD)-was developed as a sur-face coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate alloy as an induction electrode. Fe-Cr and Fe-Cr-Y2O3 micro-crystalline coatings were deposited on stain-less steel (Fe-18Cr-8Ni) surfaces. Oxidation at 950℃ in ambient air showed that the coatings greatly improved the oxidation resistance of the steel. The addition of dis-persed Y2O3 nano-particles into the alloy coatings was found to further reduce the scaling rate and enhance the adhesion of oxide scales.

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.

Effect of heating temperature on surface oxides of a Zn-1.2Al-1.2Mg coated press-hardened steel

The experiment utilized commercial hot-dip Zn-1.2Al-1.2Mg(designated ZM)coated steel sheets,which were heated in a resistance furnace and held for 5 min at temperatures ranging from 600℃to 900℃.The main goal was to investigate the effect of heating temperature on the surface oxidation behavior of the ZM coating.The results show that at lower heating temperatures,the surface oxides are mainly composed of an original thin Al_(2)O_(3) layer,which acted as a barrier preventing further oxidation of the coating.By contrast,at higher heating temperatures,intermetallic phase formation caused Al_(2)O_(3) layer fragmentation.As a result,the oxide layer of the coating surface became more complex,featuring thicker Al_(2)O_(3),MgO,and ZnO.

Structural, Optical and Luminescence Properties of ZnO Thin Films Prepared by Sol-Gel Spin-Coating Method： Effect of Precursor Concentration

Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2·2H_2O] as precursor and isopropanol and monoethanolamine（MEA） as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.

A study on reactive braze coating of (TiC+Cr_3C_2)/Fe composite coatings

A new hardfacing process, reactive braze coating process (RBCC) was studied, and (TiC+Cr_3C_2)/Fe composite coatings were prepared by RBCC using carbon, Cr_3C_2, iron, ferrochromium and titanium powder as the raw materials in vacuum braze furnace. The results show that TiC is in-situ synthesized in the coatings. The methods of introducing Cr_3C_2 have great effects on the distribution of TiC. Adding Cr_3C_2 directly to the raw materials for coatings, fine TiC particles aggregate into discoids parallel to the coating surface, whereas, in-situ synthesizing Cr_3C_2 in coatings, the aggregations of TiC are lumpish. During braze coating, Cr_3C_2 particles directly added dissolve and precipitate to become needle-shaped. The coatings have an even and smooth surface and are combined with their mild steel substrates by a metallurgical bonding.

Electrodeposition of Ni-Co-Fe_2O_3 composite coatings

Ni-Co-Fe2O3 composite coatings were electrodeposited using cetyltrimethylammonium bromide(CTAB)-modified Watt's nickel bath with Fe2O3 particles dispersed in it.The effects of the plating parameters on the chemical composition,structural and morphological characteristics of the electrodeposited Ni-Co-Fe2O3 composite coatings were investigated by energy dispersive X-ray(EDS) spectroscopy,X-ray diffractometry(XRD) and scanning electron microscopy(SEM).The results reveal that Fe2O3 particles can be codeposited in the Ni-Co matrix.The codeposition of Fe2O3 particles with Ni-Co is favoured at high Fe2O3 particle concentration and medium stirring,and the deposition of Co is favoured at high concentration of CTAB.Moreover,the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed <220> preferred orientation.Composites with high concentration of embedded particles exhibit a preferred crystal orientation of <111>.The more the embedded Fe2O3 particles in the metallic matrix,the smaller the sizes of the crystallite for the composite deposits.

Fracture Behaviour of Laser Clad Fe-and Ni-base Alloy Coatings on a Cast Iron under SEMI Loading

Laser cladding technique has been applied to renovate some partially-damaged (or worn) components with Fe, Ni, Co-base alloys, hence to improve their hardness values and wear resistance successfully in previous reports. But for some punching or shearing cast iron dies damaged or worn in automobile manufacture, the renovated surfaces also bear some impact loading. Therefore, a small-energy and multi-impact (SEMI) test was designed to investigate the fracture behaviour of renovated cast iron dies achieved by laser cladding of Fe and Ni-base alloys under SEMI loading to meet above requirement. observations show that the fracture took place in the substrate near to the substrate/coating interface rather than at the interface. The tempering temperature has a great influence on the cycles to fracture of laser-clad samples under SEMl loading, i.e. the low tempering temperature of 300℃ gives a maximum cycle to fracture, while a higher tempering temperature of 400℃ has a minimum. Furthermore, the fracture mechanism has also been discussed in present study

Increasing Dye-Sensitized Solar Cell Efficiency by ZnO Spin-Coating of the TiO₂Electrode: Effect of ZnO Amount

This paper is concerned with the improvement of dye-sensitized solar cell (DSSC) efficiency upon ZnO-coating of the TiO2 electrode. Sol-gel ZnO of controlled amount by varying the number of sol drops during spin-coating is shown to increase the DSSC efficiency. The highest efficiency is obtained at a single sol drop with enhancement of 40%, while beyond this amount the efficiency falls down sharply to zero. Based on measured optical absorption spectra of the different dye-loaded electrodes, it is concluded that this amount of ZnO sol corresponds to the thinnest layer that can create the energy barrier to minimize the electron recombination rate without seriously affecting the dye adsorption efficiency of the TiO2 film.