第一篇:纳米材料的湿法合成(DOC)
论文中英文摘要
作者姓名:孙旭平
论文题目:纳米材料的湿化学合成及新颖结构的自组装构建
作者简介:孙旭平,男,1972年08月出生,202_年09月师从于中国科学院长春应用化学研究所汪尔康研究员,于202_年03月获博士学位。
中
文
摘要
围绕论文题目“纳米材料的湿化学合成及新颖结构的自组装构建”,我们开展了一系列研究工作。通过湿化学途径,在贵金属纳米粒子及其二维纳米结构和导电聚合物纳米带的合成方面进行了深入研究。同时,利用界面自组装及溶液自组装技术,构建了一些新颖结构。本论文研究工作的主要内容和创新点表现在以下几个方面:
(1)首次提出了一步加热法制备多胺化合物保护的贵金属纳米粒子。我们利用多胺化合物(包括聚电解质和树枝状化合物)作为还原剂和保护剂,直接加热贵金属盐和多胺化合物的混合水溶液,在不加入其它保护剂和还原剂的情况下,一步制备得到了稳定的贵金属金和银的纳米粒子。我们在实验中发现,树枝状化合物聚丙烯亚胺能对反应生成的金纳米粒子的大小及成核和生长动力学进行有效控制。我们还发现,室温下直接混合浓的阳离子聚电解质分支型聚乙烯亚胺和浓的HAuCl4水溶液可得到高浓度的、稳定的胶体金。这种一步合成法操作简单且方便易行,是一种制备多胺化合物保护的贵金属纳米粒子的通用方法;同时,本方法合成的纳米粒子表面带正电荷,可用作加工纳米粒子功能化薄膜的构建单元。(2)首次提出了一种无表面活性剂的、无模板的、大规模制备导电聚合物聚邻苯二胺纳米带的新方法。我们通过在室温下直接混合邻苯二胺和HAuCl4水溶液,在没有表面活性剂或“硬模板”存在的条件下,获得了长度为数百微米、宽度为数百纳米、厚度为数十纳米的聚邻苯二胺。纳米带的自发形成可归因于反应中生成的金纳米粒子催化的邻苯二胺的一维定向聚合。本方法方便快速,无需加入表面活性剂或使用“硬模板”,且可用于大规模制备。此外,我们通过在室温下直接混合AgNO3和邻苯二胺水溶液,也获得了大量的一维纳米结构,并发现其形貌可通过调节实验参数而改变。我们还发现,当溶液pH降低时,这些一维结构将分解成水溶性的低聚体,而如果再次升高pH,这些低聚体又将自组装形成一维纳米结构。各种数据表明,这种一维纳米结构是由邻苯二胺被AgNO3氧化后所生成的低聚体在溶液中自组装而形成的。
(3)发展了一系列可大量制备沿(111)晶面优先生长的单晶金二维结构(包括纳米片及微米盘)的湿化学合成方法。在室温下直接混合HAuCl4和邻苯二胺水溶液,我们得到了大量的、呈六角形的、纳米厚度的单晶金片,其尺寸达1.5μm,邻苯二胺和HAuCl4间的摩尔比是纳米片形成的关键,这种纳米片不仅能应用于光学领域,还可用于加工具有独特机械性能的新型结构材料。我们通过直接加热浓的HAuCl4和线型聚乙烯亚胺混合水溶液,也获得了大量的金纳米单晶片,其尺寸可达40μm,反应物浓度是获得纳米片的关键因素,这种具有大的(111)晶面的单晶金片有望用做扫描隧道显微镜(STM)的基底。此外,通过加热草酸-HAuCl4混合水溶液,我们还得到了大量的、尺寸达4μm的、呈六角形的金二维结构,但其厚度大于100 nm,为微米盘,其大小和厚度可通过草酸的用量得到控制。
(4)发展了一种基于溶液中的配位组装的、室温下方便合成有机-无机配位聚合物杂化材料的单分散亚微米胶体球的新方法。在室温下直接混合H2PtCl6和对苯二胺水溶液,通过对苯二胺和PtCl62-在溶液中的配位自组装,我们得到了亚微米尺寸的、单分散的、配位聚合物球形胶体球。实验表明,粒子大小和多分散度可由反应物间的摩尔比和浓度进行控制,获得单分散胶体球的最佳实验条件是1:1摩尔比和适中的浓度。本研究结果具有比较重要的意义:(1)它提供了一个温和的、室温条件下获得单分散胶体粒子的合成方法,从而避免了获得单分散的无机材料胶体粒子所必须的高温反应条件;(2)这种胶体粒子是一种新的杂化材料,它结合了两种组分的优点而具有多种属性,因而可用在许多领域;(3)这种胶体粒子在强还原剂如NaBH4 存在的情况下,由于其中的 Pt阳离子组分被还原而发生分解,因此可用做易分解的胶体粒子模板加工中空球。此外,我们通过室温下直接混合邻苯二胺的N-甲基吡咯烷酮溶液和AgNO3水溶液,得到了亚微米的球形银胶体粒子(平均粒径达850 nm)。实验结果还表明,升高温度有利于更大尺寸的银粒子的生成,溶剂对纯的银粒子沉淀物的获得起着比较关键的作用。这些亚微米粒子的形成经历了两个阶段:(1)超饱和溶液中纳米主粒子的成核;(2)形成的主粒子聚集成更大的均匀的粒子。
(5)我们发展了一种在表面巯基功能化的电极表面有效固定Ru(bpy)32+的新方法。本方法同时运用了溶液自组装和固体表面自组装两种技术,即:先将Ru(bpy)32+和柠檬酸根阴离子保护的金纳米粒子的水溶液按照一定比例混合,得到了Ru(bpy)32+-金纳米粒子聚集体,然后把少量聚集体的悬浮液直接滴在表面巯基功能化的电极表面,从而实现Ru(bpy)32+在电极表面的有效固定。该方法简单易行,制备的电极具有很好的稳定性和电化学发光性能,因而在固态电化学发光检测方面具有很好的应用前景;此外,该方法还可用于在固体表面构建Au纳米粒子多层膜。
(6)发展了一种通过加热3-噻吩丙二酸(3-thiophenemalonic acid, TA)和H2PtCl6混合水溶液直接制备小的Pt纳米粒子的新方法,并通过对该胶体溶液用Ru(bpy)32+处理,得到了Ru(bpy)32+-Pt纳米粒子聚集体。通过对在裸电极表面的聚集体进行循环电势扫描,使得聚集体中的TA分子发生电化学聚合而在电极表面形成了稳定的聚合物膜;由于该膜有效地避免了聚集体从电极表面脱落,从而我们得到了非常稳定的、具有极好电化学发光性能的膜。本工作不但提供一种方便制备Pt纳米粒子的新途径,而且还发展了一种在任何表面直接加工电化学发光检测器的新方法,在固态电化学发光检测方面具有重要应用价值。(7)通过在室温下直接混合H2PtCl6和Ru(bpy)3Cl2水溶液,我们获得了具有新颖形貌的、含有Ru(bpy)32+的微结构。实验结果表明,金属价态、金属种类及反应物摩尔比和浓度对微结构的形貌有重要影响,形成的微结构都具有很好的电化学发光性能。这些微结构给我们提供了一种新的功能材料,将在毛细管电泳或毛细管电泳微芯片的固态电化学发光检测方面有着很好的应用前景。
关键词: 纳米材料,湿化学,自组装,电化学发光
Wet-Chemical Routes to the Preparation of Namomaterials and Self-Assembly-Based Fabrication of Novel Structures
Sun Xuping ABSTRACT
Both the wet-chemical preparation of nanomaterials and self-assembly-based fabrication of novel structures have been paid considerable attention.We carried out several studies on the preparation of noble metal nanoparticles and its two-dimensional nanostructures and conducting polymers nanobelts via wet-chemical routes.On the other hand, we fabricated some novel structures through self-assembly on planar solid substrates or in solutions.Especially, the application of some structures in the field of solid-state electrochemiluminescence detection is also explored.We have developed a heat-treatment-based strategy for the one-step preparation of polyamine-protected noble
metal
nanoparticle.With
the
use
of
third-generation poly(propyleneimine)(PPI G3)dendrimer to simultaneously act both as the reducing agent and protective agent, stable noble metal gold nanoparticles have spontaneously formed by heating a solution containing HAuCl4 and PPI G3.As a result, an additional step of introducing a reducing agent as well as a protective agent is no longer needed.It is found that the size, the nucleation and growth kinetics of the gold nanoparticles thus formed can be tuned by changing the initial molar ratio of PPI G3 to gold.Similarly, highly stable Ag nanoclusters with narrow size distribution have been prepared by heating a AgNO3/PPI G3 aqueous solution without the additional step of introducing other reducing agents and protect agents.It is found that as-obtained particle is in coexistence of Ag and Ag2O and increasing temperature results in both the decrease in number of small particles and the increase in size of large particles.In addition, such thermal process has been successfully used to prepare amine-functionalized polyelectrolyte-protected gold nanoparticles by directly heating an aqueous solution containing HAuCl4 and polyelectrolytes.Four polyelectrolytes including N-[3-(trimethoxysilyl)propyl]polyethylenimine(Si-PEI), branched polyethylenmine(BPEI), linear polyethylenimine(LPEI)and poly(allylamine hydrochloride)(PAH)were used in our study and well-stabilized gold nanoparticles with relatively narrow size distribution were obtained.Because gold nanoparticles thus formed can be combined with the properties of the polyelectrolytes used, they hold promise for use in the biomedical and bioanalytical field and on the other hand, as building blocks for the creation of nanoparticles-containing thin films.This strategy will be general to other polyelectrolytes with the same chemical structure as these four polyelectrolytes used and to the preparation of other nanoparticles such as Ag nanoparticles.Furthermore, we have found that highly concentrated, well-stable gold colloids can be prepared by direct mix of concentrated HAuCl4 and BPEI aqueous solutions at room temperature.We have developed for the first time a novel but simple surfactantless, templateless method for preparing conducting polymer poly(o-phenylenediamine)nanobelts on a large scale.The mix of HAuCl4 and o-phenylenediamine aqueous solutions at room temperature results in the formation of a large quantity of precipitate.Lower magnification scanning electron microscopy(SEM)image indicates that the precipitate consists of a large quantity of uniform one-dimensional structures.Higher magnification SEM image further reveals these structures are transparent nanobelts with several hundred micrometers in length, several hundred nanometers in width, and several ten nanometers in height.Also observed in these SEM images are a number of nanoparticles.The X-ray diffraction(XRD)analysis of the resulting precipitate reveals the formation of amorphous poly(o-phenylenediamine)polymers with larger crystalline size as well as crystalline gold.Elemental analysis of the resulting precipitate using secondary electrons by SEM indicates the belts are poly(o-phenylenediamine)polymers but the particles are gold particles.The possible formation of the nanobelts can be explained as follows: The reduction of HAuCl4 by o-phenylenediamine leads to the formation of gold nanoparticles with the occurrence of o-phenylenediamine oligomers first, then gold nanoparticles produced serve as active catalysts to catalyze the oriented oxidative polymerization of other o-phenylenediamine monomers by HAuCl4 along the oligomers produced, resulting in the formation of poly(o-phenylenediamine)nanobelts.Furthermore, we have found that mixing of AgNO3 and o-phenylenediamine in aqueous medium results in the formation of uniform one-dimensional structures.However, the formation of such 1D structure involves the following two stages:(1)The oxidation of o-phenylenediamine by AgNO3 leads to the formation of inpidual o-phenylenediamine oligomers.(2)The resulting inpidual oligomers self-assembly to form uniform larger 1D structures.Interestingly, decreasing medium pH can break these 1D structures apart to form inpidual oligomers, or vice versa.It is also found that both the concentration and molar ratio of reactants have considerable influences on the morphologies of the structures thus formed.We have developed several wet-chemical approaches for the large-scale preparation of two-dimensional, single-crystalline gold structures including nanoplates and microdisks.The mix of an appropriate volume of an aqueous solution of freshly prepared o-phenylenediamine and HAuCl4 at room temperature with 1:1 molar ratio of o-phenylenediamine to gold gradually leads to a large quantity of precipitate, which is collected by centrifugation, washed several times with THF and water, and then suspended in water.The lower magnification SEM image indicates that the precipitate consists of a large amount of particles, while the higher magnification SEM image clearly reveals that the particles are micrometer-scale plates(about 1.5 µm in size), mainly hexagonal in shape.The distance between two planes of one plate standing against the glass substrate indicates that these plates are nanoplates.The corresponding energy-dispersive X-ray spectrum(EDS)shows these nanoplates are pure metallic gold.Two surface plasmon absorption bands at about 680 and 925 nm which arise from the longitudinal plasmon resonance of gold particles are observed for these gold nanoplates, providing another piece of evidence for the formation of anisotropic gold particles.It suggests that the quantity of o-phenylenediamine in the solution is crucial to yielding gold nanoplates and we may suggest that o-phenylenediamine molecules serve as a soft template and kinetically control the growth rates of various faces of gold particles by selectively adsorbing on to the crystallographic planes, thus resulting in the formation of large single-crystalline gold nanoplates.The importance of the platelet-like gold particles is not restricted to optics;exceptionally interesting materials with unique mechanical properties can be obtained with such colloids.A polyamine process has also been successfully used for the high-yield preparation of single-crystalline gold nanoplates with several 10µm in size, mainly hexagonal in shape, carried out by heating a concentrated aqueous solution of LPEI and HAuCl4 at 100℃.The following experimental facts(1)there are no gold byproducts with other shapes except the nanoplates existing in the resulting products and(2)adding NaBH4 to the colorless supernatant after the termination of reaction gives no gold particles due to the depletion of HAuCl4 in the mixture by LPEI indicate that this heat-treatment-based polyamine process is a high-yield approach for the preparation of large gold nanoplates.It is found that the concentration of reactants is crucial to the formation of nanoplates.As-prepared gold nanoplates with a large Au(111)face may hold promise for scanning tunneling microscopy(STM)substrates.Furthermore, heating an aqueous oxalic acid/HAuCl4 solution has been proven to be an effective and facile approach for the large-scale production of microsized, single-crystalline, hexagonal gold microplates with a thickness above 100 nm.Both the size and the thickness of these plates can be controlled by the molar ratio of oxalic acid to gold.It is also found that the concentration of reactants strongly influences the formation of the gold plates.We have demonstrated a novel coordination-based strategy to the fabrication of submicrometer-scale, monodisperse, spherical colloids of organic-inorganic hybrid materials.The mix of p-phenylenediamine and H2PtCl6 aqueous solutions at room temperature results in the formation of a large amount of precipitate.Low magnification SEM image of as-prepared precipitate indicates that the precipitate consists of a large quantity of monodisperse, submicrometer-scale particles about 420 nm in diameter.Higher magnification SEM image reveals that these particles are spherical in shape and well-separated from each other, and a local magnification of a single colloidal sphere by transmission electron microscopy(TEM)indicates that the resulting particles have electron-microscopically perfectly smooth surface.The chemical composition of the resulting colloids was determined by energy-dispersed spectrum(EDS)and the occurrence of the peaks of Pt, Cl, C, and N indicates that the colloids are products of p-phenylenediamine and H2PtCl6.A possible formation process is briefly presented as following: When p-phenylenediamine and PtCl62-are mixed together, the two nitrogen atoms on the para positions of one p-phenylenediamine aromatic ring can coordinate to two different Pt(IV)cations, resulting in p-phenylenediamine-bridged structure, and the Pt species contained in as-formed structure can further capture other p-phenylenediamine molecules by coordination interactions along different directions.This coordination-induced assembly process can proceed repeatedly until the depletion of reactants in the solution, resulting in the formation of large coordination polymers, finally.It is found that the particle size and polydispersity can be controlled by the molar ratio and concentration of reactants, however, the optimum experimental parameters for the production of monodisperse colloids are 1:1 molar ratio and moderate concentration of the two reactants.Our observations are significant for the following reasons.(1)It provides a mild, room temperature route to fine colloids, avoiding the use of high temperature, which is crucial to the formation of fine colloids of inorganic materials.(2)Such colloids are new hybrid materials with versatile properties provoked by combining the merits of two sources and may find applications in many fields.(3)Such colloids are easily broken up by a strong reducing reagent, such as NaBH4, because of the reduction of the Pt cations contained therein, and therefore, they hold promise as easily decomposable colloidal templates for the fabrication of hollow spheres for a variety of applications.We have also demonstrated the rapid preparation of uniform, large, spherical Ag spheres with relatively low polydispersity through a simple wet-chemical route.The formation of Ag particles with about 750 nm in diameter occurs in a single process, carried out by direct mix of AgNO3 aqueous solution and o-phenylenediamine N-methyl-2-pyrrolidone(NMPD)solution at room temperature.The formation of monodisperse Ag colloids in our previous study can be explained as follows: AgNO3 is reduced by o-phenylenediamine to form metallic Ag atoms.With elapsed time, new Ag atoms are generated in this system and nucleation occurs as the concentration of Ag atoms reaches critical supersaturation, resulting in the formation of nuclei.The nuclei grow to nanoscale primary particles by further addition of Ag atoms, and then the primary particles aggregate to form large Ag spheres with relatively narrow size distribution.It is found that that increasing temperature results in increasing particle size.We have found that the mix of AgNO3 and o-phenylenediamine aqueous solutions, under otherwise identical conditions, yields precipitate consisting of a large quantity of large spherical Ag particles and belt-shaped structures corresponding to the oxidative products of o-phenylenediamine by AgNO3.NMPD is a powerful solvent with low toxicity and broad solubility, completely soluble in water at all temperatures and soluble in most organic solvents.We therefore choose NMPD in our present study as an effective cosolvent to dissolve the oxidative products of o-phenylenediamine in a timely manner, preventing them from precipitating with Ag particles and leading to the formation of pure Ag spheres.We have developed a novel method based on both solution-and planar solid substrate-based assembly techniques for effective immobilization of Ru(bpy)32+ on sulfhydryl-derivated electrode surfaces for solid-state electrochemiluminescene detection application.The whole immobilization process involves the following two steps:(1)The addition of Ru(bpy)32+ cations into citrate-capped gold nanoparticles(AuNPs)solution results in the formation of a Ru-AuNPs precipitate due to electrostatic interactions-driven assembly of the positively charged Ru(bpy)32+ cations and the negatively charged citrate ions coating on the AuNPs;(2)The suspension of Ru-AuNPs was placed on the sulfhydryl-derivated ITO electrode surface.The energy-dispersed spectrum(EDS)of the resulting precipitate indicates the precipitate consists of Ru(bpy)32+ and AuNPs.The absence of the peak of S element in the EDS may be attributed to the following two reasons:(1)The content of S element itself is too low to be detected.(2)The sulfhydryl groups are located below the Ru-AuNPs film, and the substrate is nearly completely covered by the Ru-AuNPs film.It is found that the modification of substrate with sulfhydryl group and the resultant strong Au-S interactions between sulfhydryl group and AuNPs are crucial to the effective immobilization of such Ru-AuNPs on the surface and there is no stable film formed on bare ITO surface.The Ru-AuNPs-modified ITO electrode is quite stable, exhibits excellent electrochemiluminescene behavior, and hence holds great promise for solid-state electrochemiluminescene detection in capillary electrophoresis(CE)or a CE microchip.It provides a new methodology for fabrication of stable Ru(bpy)32+-containing structures on a solid electrode surface for solid-state electrochemiluminescene detection and, on the other hand, also provides an interesting method of immobilization of nanoparticles on the surfaces for applications.We have developed a simple thermal process for the preparation of small Pt nanoparticles, carried out by heating a H2PtCl6/3-thiophenemalonic acid(TA)aqueous solution without the addition of other reducing agents and protective agents.The formation of such Pt nanoparticles can be attributed to the direct redox between TA and PtCl62-.It is found that such Pt nanoparticles were quite stable for several months without any observable aggregation, indicating that TA serves as a very effective protective agent for the formation of Pt nanoparticles, which can be attributed to the fact that the sulfur atom in TA has a very strong nucleophilicity with lone-pair electrons and such a lone-pair electron can form a type of donor-acceptor complex with the Pt atom on the particle surface, yielding TA-protected Pt nanoparticles.The following treatment of such colloidal Pt solution with Ru(bpy)32+ causes the assembly of Pt nanoparticles into aggregates.Given the acidic reaction condition, the Pt particle surface is mainly covered by protonated carboxylic acid groups and thus the electrostatic interactions between positively charged Ru(bpy)32+ and Pt nanoparticles are only partially responsible for the formation of the aggregates.On the other hand, both TA and Ru(bpy)32+ are rich in π-type bonds and the strong intermolecular π-π interactions between them also contribute to the formation of the aggregates via self-assembly.The most attractive point is that directly placing such aggregates on any bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.The formation of the stable film of the aggregates on a bare electrode surface can be attributed to the fact that the TA in the aggregates is electrochemically polymerized during the cycling scans to form stable polymer film on electrode surface and the polymer film can effectively protect the aggregates from falling from the electrode surface.Our finding is significant for the following two reasons:(1)It provides a general methodology for the preparation of noble metal nanoparticles for applications;(2)Such assemblies will provide us new kind of materials for solid-state electrochemiluminescence detection in capillary electrophoresis(CE)or a CE microchip.We have reported on the first preparation of novel, robust Ru(bpy)32+-containing supramolecular microstructures via a solution-based self-assembly strategy, carried out by directly mixing H2PtCl6 and Ru(bpy)3Cl2 aqueous solutions at room temperature.It is found that the microstructures thus formed are robust enough to stand a violent sonication process and their formation is very fast.Given the positive charge of Ru(bpy)32+ and the negative charge of PtCl62-, we may suggest that electrostatic attractions between these two complexes drive the formation of micrometer-scale supramolecular microstructures.The observation that the UV-vis absorption spectra of Ru(bpy)32+ aqueous solution is similar to that of the microstructures suspension in water further indicates that only pure electrostatic interactions are responsible for the formation of the microstructures.The electrochemical behavior of the Ru(bpy)32+ components contained in the solid film of the microstructures formed on the electrode surface is also studied and found to exhibit a diffusion-controlled voltammetric feature.We have found that both the molar ratio and concentration of reactants have a heavy influence on the morphologies of such microstructures.Most importantly, such microstructures exhibit excellent electrochemiluminescence behaviors and therefore hold great promise as new luminescent materials for solid-state electrochemiluminescence detection in capillary electrophoresis(CE)or CE microchip.Keywords: nanomaterials, wet-chemical, self-assembly, electrochemiluminescence
第二篇:材料合成与制备论文(纳米材料)
硕研10级20班
材料工程
2010012014
夏春亮
纳米材料的制备方法
纳米制备技术是80年代末刚刚诞生并正在崛起的新技术,其基本涵义是:纳米尺寸范围(10-9~10-7m)内认识和改造自然,通过直接操作和安排原子、分子创造新物质。由于纳米材料具有奇特的力学、电学、磁学、热学、化学性能等,目前正受到世界各国科学家的高度重视。
一、气相法制备纳米微粒
1.溅射法
此方法的原理为:用两块金属板分别作为阴极和阳极,阴极为蒸发用材料,在两电极间充入Ar(40~250Pa),两极间施加的电压范围为0.3~1.5kV。由于两极间的辉光放电使Ar粒子形成,在电场作用下Ar离子冲击阳极靶材表面,使靶材原子从其表面蒸发出来形成超微粒子,并在附着面上沉积下来。离子的大小及尺寸分布主要取决于两极间的电压、电流、气体压力。靶材的表面积愈大,原子的蒸发速度愈高,超微粒的获得量愈大。
溅射法制备纳米微粒材料的优点是:1)可以制备多种纳米金属,包括高熔点和低熔点金属。常规的热蒸发法只能适用于低熔点金属;2)能制备出多组元的化合物纳米微粒,如A lS2,Tl48,Cu91,Mn9,ZrO2等;通过加大被溅射阴极表面可加大纳米微粒的获得量。采用磁控溅射与液氮冷凝方法可在表面沉积有方案膜的电镜载网上支撑制备纳米铜颗粒。
2.混合等离子法 硕研10级20班
材料工程
2010012014
夏春亮
此方法是采用RF(射频)等离子与DC直流等离子组合的混合方式来获得超微粒子。该制备方法有以下几个特点:
1)产生RF等离子时没有采用电极,不会有电极物质(熔化或蒸发)混入等离子体而导致等离子体中含有杂质,故超微粒的纯度较高;
2)等离子体所处的空间大,气体流速比DC直流等离子体慢,致使反应物质在等离子空间停留时间长,物质可以充分加热和反应;
3)可使用非惰性气体制备化合物超微粒子,使产品多样化。混合等离子蒸发法制取超微粒子有3种方法: 1)等离子蒸发法
使大颗粒金属和气体流入等离子室,生成超微粒子; 2)反应性等离子气体蒸发法
使大颗粒金属和气体流入等离子室,同时通入反应气体,生成化合物超微粒子;
3)等离子VCD法
使化合物随载气流入等离子室,同时通入反应气体,生成化合物超微粒子。
例如,将原料Si3N4以4g/min的速度流入等离子室,通入H2进行热分解,再通入反应性气体NH3,经反应生成Si 3N4超微粒子。
3.激光诱导化学气相沉积法(LVCD)LVCD法具有清洁表面,离子大小可精确控制、无粘结、粒度分布均匀等优点,并容易制备出几纳米至几十纳米的非晶及晶态纳米微粒。硕研10级20班
材料工程
2010012014
夏春亮
目前LVCD法已制备出多种单质、化合物和复合材料超细粉末,并且已进入规模生产阶段,美国的MIT于1986年已建成年产几十吨的装置。激光制备超细微粒的工作原理是利用反应气体分子对特定波长激光束的吸收,引起反应气体分子激光光解、激光热解、激光光敏化和激光诱导化学合成反应,在一定工艺条件下,获得超细粒子空间成核和长大。例如,用连续输出CO2激光(10.6um)辐照硅烷气体分子(SiH4)时,硅烷分子很容易发生热解反应:SiH4→Si(g)+ 2H2↑,热解生成的气相Si(g)在一定工艺条件下开始成核长大,形成纳米微粒。
激光制备纳米粒子的装置一般有2种类型:正交装置和平行装置。其中正交装置使用方便,易于控制,工程实用价值大,激光束与反应气体流向正交。激光束照在反应气体上形成反应焰,经反应在火焰中形成微粒,由氩气携带进入上方微粒捕捉装置。
4.化学蒸发凝聚法(CVC)这种方法主要是利用高纯惰性气体作为载气,携带有机高分子原料,通过有机高分子热解获得纳米陶瓷粉体。例如,六甲基二硅烷进入钼丝炉(温度为1100~1400℃,压力为100~ 1000Pa)热解形成团簇,并进一步凝聚成纳米级微粒,最后附着在充满液氮的转动的衬底上,经刮刀下进行纳米粉收集。此法具有产量大、颗粒尺寸细小、分布窄等优点。
5.爆炸丝法
基本原理是:先将金属丝固定在一个充满惰性气体(5MPa)的反应室中,丝的两端卡头为2个电极,它们与一个大电容相联结形成回路,硕研10级20班
材料工程
2010012014
夏春亮
加15kV的高压,金属丝在500~800kA下进行加热,熔断后在电流停止的一瞬间,卡头上的高压在熔断处放电,使熔断的金属在放电的过程中进一步加热变成蒸气,在惰性气体碰撞下形成纳米粒子沉降在容器的底部,金属丝可以通过一个供丝系统自动进入两卡头之间,从而使上述过程重复进行。这种方法适用于制备纳米金属和合金粉体。
6.其他方法
近年来,由于纳米材料规模化生产以及防止纳米粉团聚的要求越来越迫切,相继出现了一些新的制备技术。例如,气相燃烧合成技术就是其中的一种,其基本原理是:将金属氯化物(MCl)盐溶液喷入Na蒸气室燃烧,在火焰中生成NaCl包敷的纳米金属微粒,由于NaCl的包敷使得金属纳离子不团聚。另一种技术是超声等离子体沉积法,其基本原理是:将气体反应剂喷入高温等离子体,该等离子体通过喷嘴后膨胀,生成纳米粒子,这种方法适合于大规模连续生产纳米粉。
二、液相法制备纳米微粒
1.沉淀法
包含一种或多种离子的可溶性盐溶液,当加入沉淀剂(如OH-,CrO2-,CO32-等)后,或于一定温度下使溶液发生水解,形成的不溶性氢氧化物和盐类从溶液中析出,将溶液中原有的阴离子洗去,经分解即得所需的氧化物粉料。
2.喷雾法
喷雾法是将溶液通过各种物理手段进行雾化获得超微粒子的化学和物理相结合的一种方法。其基本过程包括溶液的制备、喷雾、干硕研10级20班
材料工程
2010012014
夏春亮
燥、收集和热处理,其特点是颗粒分布比较均匀,但颗粒尺寸为亚微米级到微米级,尺寸范围取决于制备的工艺和喷雾方法。根据雾化和凝聚过程,喷雾法可分为3种:
1)喷雾干燥法 将金属盐溶液或氢氧化物溶胶送入雾化器,由喷嘴高速喷入干燥室获得金属盐或氧化物的微粒,收集,烧成所需成分的超微粒子;
2)雾化水解法 将一种盐的超微粒子,由惰性气体载入含有金属醇盐的蒸气室,金属醇盐的蒸气附着在超微粒的表面,与水蒸气反应分解后形成氢氧化物微粒,经焙烧可获得氧化物超细微粒。这种方法获得的微粒纯度高,分布窄,尺寸可控,具体尺寸大小主要取决于盐的微粒大小;
3)雾化焙烧法 将金属盐溶液由压缩空气经窄小的喷嘴喷出雾化成小液滴,雾化温度较高,使金属盐小液滴热解形成超微粒子。
3.凝胶-溶胶法
此法的基本原理是将金属醇盐或无机盐水解,溶质聚合凝胶后,再将凝胶干燥,煅烧,最后得到无机材料。本法包括以下几个过程:
1)溶胶的制备 有两种制备方法: 一是先将部分或全部组分用适当沉淀剂先沉淀出来,经凝聚,使原来团聚的沉淀颗粒分散成原始颗粒。这种原始颗粒的大小一般在溶胶体系中胶核的大小范围内,因而可值得溶胶;二是由同样的盐溶液,通过对沉淀过程的仔细控制,使首先形成的颗粒不致团聚为大颗粒沉淀,从而直接得到溶胶。
2)溶胶凝胶转化 溶胶中含有大量的水,凝胶过程中,使体系失硕研10级20班
材料工程
2010012014
夏春亮
去流动性,形成一种开放的骨架结构。实现凝胶作用的途径一是化学法,即通过控制溶胶中的电解质浓度来实现凝胶化;二是物理法,即迫使胶粒间相互靠近,克服斥力,实现凝胶化。
3)凝胶干燥 在一定条件下,使溶剂蒸发,得到粉料,干燥过程中凝胶结构变化很大。该方法化学均匀性好,纯度高,颗粒细,可容纳不溶性组分或不沉淀组分,烘干后容易形成硬团聚现象,在氧化物中多数是桥氧键的形成,球形凝胶颗粒自身的烧结温度低,但凝胶颗粒之间的烧结性差,块状材料烧结性能不好,干燥时收缩大。
4.湿化学法
湿化学法制备纳米粉末是目前公认的具有发展前途的制粉方法,也是实验室常用的手段。湿化学法的实验流程如下:
确定纳米粉材料→制成含该材料粒子的溶液→用该材料的E-pH图确定沉淀的pH范围→将分散剂NH4Cl溶入去离子水中,并用氨水、盐酸调节水溶液至沉淀的pH 值→含该材料离子的水溶液在具有恒定的pH 的沉淀液中雾化→凝胶→水洗,过滤,乙醇脱水→煅烧、研磨→纳米粉。
第三篇:湿法脱硫
目前燃煤烟气脱硫工艺90%以上是采用湿法脱硫,即通过喷射石灰石浆液与烟气中的二氧化硫分子接触反应,最终生成石膏。绝大部分石膏通过脱水而收集,但浆液中的微小粒子和水溶性盐,随烟气逸出脱硫塔,通过烟囱排入大气。过去,一部分相对较大的颗粒,在烟囱附近因为重力降落,俗称“石膏雨”,现在加装湿电除尘或高效除雾器后,这部分基本看不到了;而PM1.0以下的亚微米粒子及水溶性盐,则随烟气根据NASA灯光数据提取的PM2.5数据、二十世纪六十年代初至202_年山东省霾和雾的天气数据、不同部门实验数据,能够确切地断定202_年雾霾大暴发是一个突发事件。据环保部大气质量实时监测数据(202_年5月13日开始公开)计算的不同时间、不同区域采暖季启动日前后三周内PM2.5的变化,采用新的检测工具对行业性湿法脱硫排出水汽的检测数据;李壮等在202_年《节能技术》上公开发表的实验结果;某著名大学雾霾成因研究团队的部分研究结论,以及采用室内加湿器分别加入纯净水、矿泉水和自来水所导致的室内PM2.5浓度巨大差异的简单实验等。若干条独立证据链证明湿法脱硫是202_年雾霾暴发的主因,并且在之后一直起着主导作用。
1.还原202_年雾霾大暴发形成过程 政府一系列针对湿法脱硫设备规范运行的政策和技术措施,以及企业的应对措施,在规定的202_年底前完成。新的湿法脱硫设备运转模式与原来的模式相比,发生了质的变化。进入202_年1月后,连续出现静稳或逆温天气。大量新增的湿法脱硫排放的含有溶解盐类和非溶解物的水汽,脱水后产生大量超细颗粒物,无法扩散,逐渐累积,为雾和霾的形成提供了充足的凝结核和湿度条件,进而引起雾霾的突然大暴发。
始于本世纪初的湿法脱硫在电厂的普及率,202_年达到35%左右,202_年基本普及。到202_年底,以湿法脱硫为主,大量合法化取消烟气再热除湿和允许排放低温湿烟汽的部门,包括:火力发电、燃煤热电、天然气锅炉、钢铁、焦化、电解铝、水泥、平板玻璃、汽车尾气、餐饮等。虽然本文主因是指湿法脱硫,但其他类似的排放低温湿烟汽的设备所起的作用,与湿法脱硫类似。1.2 湿法脱硫导致雾霾大暴发的作用机理湿法脱硫导致雾霾大暴发的作用机理是,已经对酸雨治理发挥重要作用的湿法脱硫,导致次生PM2.5,使得202_年雾霾大暴发,以及后来的雾霾高发、频发并出现反复。具体而言,202_年1月,突然全部正常运行的或新上的湿法脱硫设备排出大量水汽;企业拆除GGH,拆除GGH后常规污染物排放量标准可以提高一倍以上[1],在湿法脱硫排出的水汽中有大量硫酸盐、脱水后形成大量超细颗粒物、占总的PM2.5比重很高的情况下,如果排出的超细颗粒物翻倍,在202_年底前许多企业一致行动,仅此一项,足以引起雾霾暴发;锅炉烟气标准由130 ℃变成40-60 ℃,干烟气变成低温湿烟(水)汽,在静稳或逆温天气下类似房间中安装了大量加湿器,从根本上改变原有烟气特性,也能够引起雾霾暴发。湿法脱硫排出的大量水汽中,有多种溶解盐和其他非溶解物,在大气中脱水后产生大量超细颗粒物,成为看不见的粒子。这些超细颗粒物隐藏在空气中,在空中停留时间长,不沉降,具有极强的迁移能力,控制和治理难度很大。遇到静稳天气或逆温天气,又吸水、膨胀、粘附、变大,成为雾霾;气象条件转好后,又可能脱水消失,也可能随着雨水落下。加上遍布京津冀及周边的各种电厂和其他有脱硫设备的燃煤设施,24小时不停运转,不断迅速补足大气中的超细颗粒物,静等静稳或逆温天气。其自身也不断向大气中输送脱水后变成大量超细颗粒物的水汽,进一步增加了空气的湿度。
可见,是企业整齐划一的湿法脱硫行为的改变,导致大气中湿法脱硫产生的超细颗粒物(形成霾的凝结核)突然增加,排出的水汽也导致空气湿度增加,从而导致202_年初静稳天气下雾霾的突然暴发和后来的频发。而在同期,国家为了治理酸雨,逐渐加大脱硫力度。虽然一些上了脱硫设备的企业并不按照要求一直开动设备,也有的通过烟气旁路系统偷排以减少成本,而烟气旁路系统是为了避免脱硫设施维护期间停产检修留的备用系统。在烟气排放到大气中之前,也有个对烟气的再加热系统(GGH)。
3.1 采用环保部监测数据验证湿法脱硫是导致集中供暖季开始时雾霾显著上升的主因
采用环保部1800多个站点300多个城市多种污染物按照小时监测数据,选取京津冀及周边部分通道城市202_、202_、202_年三个集中供暖季(11月15日开始)启动前后和黑龙江省主要城市202_年集中供暖季(10月20日开始)后前后三周的变化,来验证湿法脱硫对雾霾的程度变化是否显著。由于采暖锅炉大都达到较高的排放标准,像电厂燃煤机组PM2.5去除率已经达到98.98%,国家规定采暖锅炉或其它行业也要达标排放或超低排放。所以,燃煤锅炉启动后多燃烧的煤炭,在经过达到国际水平的除尘设施后,相对其它所有排放源的排放的贡献,可以忽略不计。说明少数几个超低排放的燃煤锅炉的启动,激发了某种雾霾产生机制——湿法脱硫排出的大量水汽中含有大量超细颗粒物。而其他常规因素,如散煤采暖等,不可能在短期内,在不同地区、不同时间引起同样类型的剧烈变化。经过脱硫工艺后,PM2.5的粒子数在0.07微米出现峰值。这是由于脱硫浆液形成细微颗粒物所致,主要是脱硫工艺中带来的硫酸根、氯离子等形成的矿物质盐。此外,还可能有通过除雾器逃逸的石膏晶粒经过脱水干燥后形成的微粒。目前的相关除尘设施对0.38微米(PM0.38)以下的超细颗粒物没有作用。
这些随着水汽排放到大气中的超细颗粒物形成霾的两个关键因素:湿度条件和凝结核,之后静等静稳或逆温天气的到来,就形成雾霾。而过去,即使是静稳或逆温天气,如果缺少另外这两个因素,也形不成霾。这两个技术层面的证据,进一步使湿法脱硫导致202_年雾霾大暴发等结论无可辩驳。4.对策措施多种湿法脱硫政策和技术措施作用的叠加,是202_年初雾霾暴发的主因,并不是说PM2.5源解析中的其他因素不重要。现在已经对其他来源的PM2.5采取了铁腕治霾行动。这些工作难度非常大,远比针对湿法脱硫的技术措施复杂,还需要继续加强。
针对现有湿法脱硫装置的大中型燃煤设施,或具有低温湿烟汽排放的燃气设施等,可采取以下措施:
1.采用冷凝装置等减少水汽(低温湿烟汽)排放污染。
2.降低水汽中的各类溶解盐和非溶解物。
3.制定标准限制烟气排放湿度和次生颗粒物。
4.加快相关技术研发,尽快进行国内湿法脱硫技术局部改造,或研发并国产化干法脱硫技术,实现合理替代。
第四篇:干法选煤和湿法选煤
干法选煤和湿法选煤。选煤过程在空气中进行的,叫做干法选煤。选煤过程在水、重液或悬浮液中进行的,叫做湿法选煤。选煤方法还可以分为重力选煤、浮游选煤和特殊选煤等。重力选煤主要是依据煤和矸石的密度差别而实现煤与矸石分选的方法。煤的密度通常在1.2-1.8g/cm3 之间,而矸石的密度在1.8 g/cm3以上,在选煤机内借助重力把不同密度的煤和矸石分开。
重力选煤又可分为跳汰选、重介质选、溜槽选、斜槽选和摇床选等。
浮游选煤简称浮选,主要是依据煤和矸石表面润湿性的差别,分选细粒(小于 0.5mm)煤的选煤方法。
特殊选煤主要是利用煤与矸石的导电率、导磁率、摩擦系数、射线穿透能力等的不同,把煤和矸石分开。它包括静电选、磁选、摩擦选、放射性同位选和 1 射线选等。此外,还有手选,即人工拣矸。它是根据块煤与矸石在颜色、光泽及外形上的差别由人工拣除。对煤与矸石硬度差别较大的块煤,可以采用滚筒碎选机进行选择性破碎,实现煤与矸石的分离。我国选煤厂中采用最广泛的选煤方法是跳汰选,其次是重介质选和浮选,其他方法均用得较少。选煤的主要产品是精煤,副产品有中煤、混煤、煤泥等。选后的矸石和尾煤为废弃物,由于它含有一些夹矸煤等可燃物,也可作制砖、烧水泥的原料,进行综合利用。
选煤厂是对煤进行分选,生产不同质量、规格产品的加工厂。按精煤使用的目的不同,选煤厂可分为炼焦煤选煤厂和动力煤选煤厂。炼焦煤选煤厂的工艺过程比较复杂,生产的精煤灰分低、质量高,主要供给焦化厂生产焦炭。动力煤选煤厂的工艺过程一般比较简单,生产的精煤主要作为动力燃料,大部分动力煤选煤厂只选块煤,末煤和粉煤不入选。按照选煤厂的位置及其与煤矿的关系,选煤厂可分为5种类型:
(1)矿井选煤厂。厂址位于煤矿工业场地内,只选该矿所产毛煤或原煤的选煤厂。这里所说的毛煤是指煤矿生产出来未经任何加工处理(一般指手选)的煤;原煤则是从毛煤中选出规定粒度的矸石,包括黄铁矿等杂物以后的煤。
(2)群矿选煤厂。厂址位于某一煤矿的工业场地内,可同时选该矿及附近煤矿所产毛(原)煤的选煤厂。
(3)矿区选煤厂。在煤矿矿区范围内,厂址设在单独的工业场地上,入选外来煤的选煤厂。(4)中心选煤厂。厂址设在矿区范围外独立的工业场地上,人选外来煤的选煤厂。(5)用户选煤厂。厂址设在用户(如焦化厂等)工业场地上的选煤厂。
设计的源头———原煤的煤质特性。煤质分析是否透彻,原煤特性把握是否准确,直接关系到设计的处方———选煤工艺能否“对症”,能否切合入选原煤的实际特性。这是衡量一部设计好与坏,合理与否的重要标准。
设计的终端———选后产品结构的定位。产品结构定位的目的是使选后产品能适销对路,能够适应市场的多元化需求。在市场经济日趋发达的今天,这项工作的重要性就更加突出了。从道理上讲,产品结构本应是原煤经洗选加工之后产生的结果,而现在反而要提到选煤工艺设计之前来预先敲定,似乎有点矛盾,不合逻辑。其实不难理解。用辩证的观点看,产品既是分选的结果,也是选前应该预定的加工目标。所以在工艺设计之前,先通过对产品结构进行多方案比选、论证,找到洗选加工可能达到的最佳结果,预先锁定选后产品结构,以便使工艺设计做到有的放矢,目标明确。
现代化的选煤厂应该具有兼收并蓄,多样化的工艺特点。对不同的选煤方法不能简单地用“先进”或“落后”去划分,这样不科学,它们各有所长,只是适用条件和范围不同而已。现代化选煤厂最主要的特点是效率高,这首先应该体现在选煤工艺是否合理上,也就是说要体现在选煤工艺是否适合入选原煤的煤质特性,是否能实现用户所要求的产品结构上。
与选煤方法相关的因素是多方面的,它们包括:原煤粒度组成特性(含粒度组成)、密度特性(含可选性);硫分构成及其赋存嵌布特性;产品结构(含市场需求);分选效率;洗选加工费;相关的基建投资费用;综合经济效益等因素。所以选煤方法的确定必须作全面的技术经济多方案比选,择优选用,才是科学合理的思路。以前按照《设计规范》规定,基本上只根据可选性难易一个条件简单地划分选煤方法适用范围的做法不全面,目前我国新的规范202_年已颁布。应按新规范执行。
近十年来,随着我国自行研发的各种类型重介旋流器工艺技术的日趋成熟,以及澳大利亚先进的模块式重介选煤厂的引进,使重介旋流器分选工艺不论在简化工艺环节、降低工程造价,提高介质系统调控水平、易于操作管理方面,还是在减少介耗、电耗,降低生产成本方面都取得了长足的进步,技术日臻完善,备受业主青睐,在我国已被广泛采用。但是,目前在重介选煤工艺设计中常常围绕几个原则问题进行争论,成为当前选煤界和设计单位关注的热点。几个主要的热点问题如下:
(1)关于重介旋流器有压入料和无压入料方式的选择。有压入料适用于煤泥含量少,原煤不易泥化,建设场地较小的选煤厂;无压入料适用于原煤易泥化的选煤厂。
(2)关于两产品重介旋流器和三产品重介旋流器的选择。两产品重介旋流器适用于有预先排矸系统或中煤含量少且产品单一的选煤厂,现一般选用三产品重介旋流器建厂。(3)关于大直径重介旋流器或小直径旋流器组的选择。为了适应国家节能减排的要求,选煤厂单系统处理能力不断提高,300-350t/h的1400/1000三产品重介旋流器已经投入使用,与选用双系统900/650 三产品重介旋流器相比节电10%以上,节省建设投资20%以上。原则上选大直径旋流器建厂。
(4)关于选前脱泥与不脱泥的选择。原煤中-0.5mm含量大于35%的情况下,建议选择选前脱泥工艺。
近几年我国设计建成的新型主厂房,已经突破了传统厂房多层框架结构的格局,使工艺布置模式也发生了很大变化。厂房布置的发展趋势如下:
(1)厂房从高层向低层发展,从多层框架向单层大厅式发展。在单层厂房大厅内,设备可以采用独立钢架支撑,也可以采用模块式结构支撑。
从厂房的土建结构看,全钢结构厂房肯定是今后的发展方向。钢结构厂房有很多优点,它不仅制作施工方便,施工工期短,抗震性能好,而且只要设计合理,造价可与钢筋混凝土结构相近。惟有维护费用偏高,是其不足之处。我们认为,若因工艺布置需要,也不必拘泥于一种全钢结构形式,完全可以采用局部钢筋混凝土框架与钢排架单层厂房相结合的混合结构。总之结构应该服从工艺需要。
(2)设备大型化,作业环节单机化,全厂单系统化,至少要尽量减少工艺系统的数量,这是选煤厂工艺布置的发展方向。这种布置模式有很多优点:可减少中间分配转运环节,为降低厂房高度提供了有利条件,使单层厂房布置模式成为可能,从而也减少了厂房体积,降低了造价。厂房高度低,泵类和运输设备运转能耗就低,有利于降低生产成本。单系统和单机化为实现高度集中控制和高度自动化提供了便利条件,为减人提效奠定了基础。单系统和单机化使设备台数大大减少,为方便维修提供了有利条件。
第五篇:干法、湿法镀锌
什么叫”湿法”和”干法”热镀锌? “湿法”热镀锌也叫“熔融溶剂法”热镀锌。钢铁工件经过脱脂、酸洗及清洗后,必须通过设置在熔锌表面上方的一个专用箱中的“熔融溶剂”(也叫助溶剂),然后再进入锌液中去镀锌。熔融溶剂一般是氯化铵与氯化锌的混合物,也有再放人其他氯盐的。
“干法”热镀锌也叫“烘干溶剂法”热镀锌。钢铁工件经过脱脂、酸洗、清洗、浸涂助溶剂并经烘干后,再浸入熔融的锌液中去镀锌。助溶剂一般是盐酸、氯化铵或氯化铵与氯化锌的混合水溶液。
向热镀锌液中加铝如何计算投入量? 试验表明,浸锌液中含0.02%的铝已经足够,可是在实际生产中,如按此比例把铝加入到锌液中去,却得不到应有的效果。结果发现有以下原因导致了铝的损耗:一是加入锌液中的铝有一部分与锌液面上空气中的氧生成了三氧化铝(A12O3);二是有一部分铝与溶剂氯化铵、氯化锌接触,生成了氯化铝(AlCl。)于178℃开始升华了。这两个原因消耗了大部分铝,要想锌液中达到0.02%.的铝,必须加入9~10倍的铝,即按0.2%的铝计量才能达到目的。
热镀锌为什么要用到助溶剂? 要想使钢铁制件与熔锌层有良好的结合力,进入锌槽中的钢铁制件要如同电镀件一样经过去油和去锈的前处理,并保证在入槽前不生成新的氧化膜。如果不浸助溶剂,即使经过前处理的制件,来到热浸锅上方,还未能下槽浸镀前,就会在高温氧化气体氛围下生成氧化膜,给镀层结合带来隐患。同时,助溶剂可以降低熔融锌与制件接触时的表面张力,使锌液能迅速与制件浸润,防止镀覆不全或结合力不牢。
热镀锌技术的发展趋势如何
随着工业加工技术的进步,热镀锌技术也有所发展,从现在的趋势看j主要有以下几点。
热镀锌法与其他镀锌法相比有什么特点? 热镀锌与电镀锌相比有以下优点:(1)可以生成较厚的镀层,并且既有纯锌层又有铁一锌合金层,所以耐蚀性能较好;(2)热镀锌生产效率特别高;制件在热镀锌槽中停留的时间一般不超过lmin;(3)相对电镀锌,热镀锌生产成本较低且对环境的影响比电镀小;(4)对板、带、丝、管等型材镀制时,自动化程度较高。
(1)采用向锌液中加人多种合金元素的方法以改善工艺性能,提高产品质量。例如锌液中镍含量控制在0.06%~0.12%之间,对活性钢(即高硅、高锰钢)镀锌质量大为改善,在一定条件下能很好处理活性钢热镀锌质量问题。
(2)选取热稳定性好的溶剂,提高工件预热温度,以减少浸锌时的热耗。
(3)采用非钢质锌锅,比如陶瓷锅,以延长锌锅使用寿命,减少锌渣,减少锌耗,提高生产效率,降低成本。
(4)在热镀锌层表面涂上有机涂层或进行无公害钝化处理。(5)采用先进的自动化生产方法和检测方法。