硼酸复合盐对人造石墨电极的抗氧化性能影响研究

针对人造石墨电极使用时的氧化损耗问题,配制出以硼酸盐为主要抗氧化成分的复合抗氧化剂,通过对石墨电极材料的常压浸渍和热处理后,浸渍样品在静态空气中不同温度下经过2 h高温灼烧,测定样品的氧化失重率。研究发现,经过浸渍处理的石墨样品在900℃的抗氧化失重率低于1.8%。利用SEM观察浸渍试样和未浸渍试样的表面形貌,对复合硼酸盐的玻璃态涂层的抗氧化机理进行了分析。     

磷酸盐溶液浸渍法涂层对石墨材料抗氧化性能的影响

在提高石墨材料高温抗氧化性能的各种方法中,溶液浸渍法的工艺操作简单,成本相对低廉,保护效果较好,因此选择了磷酸盐溶液作为浸渍液,并按照试样清洗、干燥、加热浸渍、热处理等流程,让石墨材料表面形成抗氧化涂层,同时进行了高温抗氧化实验。实验中探究了浸渍时间、表面活性剂添加量、热处理、热处理终温4个变量对抗氧化性能的影响。结果表明,除了热处理终温这一因素外,其他3个因素对石墨材料的抗氧化性能均有明显影响。其中,浸渍时间为30 min、表面活性剂添加量为8 m L、有热处理的情况下,石墨材料形成的涂层最佳,抗氧化性能最好。     

溶液浸渍法提高石墨材料抗氧化性能研究

以硼酸盐、磷酸盐和复合盐三种浸渍剂对石墨材料进行了溶液浸渍法研究，研究结果表明：经溶液浸渍法处理的石墨材料氧化失重率降低，石墨抗氧化性能明显提高。溶液浸渍法是改善石墨材料抗氧化性能的有效途径。     

浸磷酸盐对碳石墨材料抗氧化性能的改善作用

对三种不同没渍、热处理方案的磷酸盐石墨材料，分别在不同温度下测定其氧化失重，证明石墨材料没渍磷酸盐后抗氧化性能可得到明显改善，其氧化失重仅为基体材料的１／４～１／６，用磷酸盐浸渍是提高石墨抗氧化性能的一种有效途径。     

添加剂—磷酸及其盐类对柔性石墨材料的影响

采用添加剂[H_3PO_4、NH_4H_2PO_4、(NH_4)_2HPO_4]浸渍处理酸化石墨,然后将其烘干,高温膨胀,最后模压成柔性石墨试片(纸)。初步探讨了浸渍液浓度、浸渍时间对柔性石墨试片高温抗氧化能力的影响,同时考察了添加剂的加入对柔性石墨试片抗拉强度、回弹性的影响。实验结果表明,与未经添加剂浸渍处理的对比样相比,经添加剂浸渍处理可明显提高柔性石墨高温抗氧化能力,同时其抗拉强度,回弹性也均有所提高。所用添加剂溶液最佳浓度为0.5～1.0mol/1,最佳浸渍时间为2～8h。     

浸渍法提高石墨材料抗氧化性能的研究

用磷酸复合盐浸渍法对石墨材料进行浸渍,研究其抗氧化性.讨论了当浸渍剂中添加不同比例的硼酸盐、碳化硅、二氧化钛等成分后,对提高浸渍效果和增强抗氧化性的影响.结果显示,在磷酸和氢氧化铝的摩尔比为25:1,硼酸盐含量为4%,碳化硅(或二氧化钛)含量为2%的条件下,在石墨表面形成白色的偏铝酸盐硬壳具有良好的抗氧化作用.而不加入硼酸盐的浸渍剂,抗氧化效果明显降低.结果表明,石墨材料经过复合磷酸盐溶液的浸渍和热处理,可在表面形成抗氧化层,增强石墨材料的抗氧化性,延长使用寿命.     

SiC改性涂层石墨基体表面抗氧化性能研究

以Si粉和碳粉为包埋粉,通过包埋法在石墨基体材料表面制备了SiC抗氧化涂层,但发现涂层疏松多孔、不连续,导致其氧化防护能力弱,为了提高石墨基体材料的高温抗氧化性,分别在包埋粉中掺杂Cr粉和W粉,对涂层进行改性。结果表明,经Cr粉改性后的涂层致密连续,表面平整,制备涂层后的试样在1650℃下进行2h氧化实验,未掺杂金属粉的试样氧化失重率为0.46%;经Cr粉改性后,试样的氧化失重率为0.08%,涂层抗氧化性得到显著提高。但经W粉改性后的试样,由于W粉的热膨胀系数较大,且改性过程是物理改性导致其氧化失重率达到1.34%。     

石墨材料的抗氧化

文章介绍了石墨材料的高温使用性能,重点论述了石墨电极材料的高温氧化特点、石墨电极在电炉炼钢中的各类消耗以及石墨材料抗氧化处理方法,并综述了国办外采用浸渍法提高石墨材料抗氧化性能的研究和应用现状。     

浸渍复合磷酸盐法石墨模具的抗氧化处理

针对热压烧结金刚石工具用石墨模具,采用浸渍复合磷酸盐法进行抗氧化处理,通过氧化腐蚀性能的研究,分析讨论了石墨模具抗氧化处理前后的抗氧化性能等。结果表明：抗氧化处理后的石墨模具,基本保持石墨的电学特性,其抗氧化性和抗压强度有明显提高,700℃下空气中氧化失重率为6％左右的氧化时间从5h提高到80h以上。     

抗氧化炭石墨材料的研究及高温氧化行为

采用了改善炭石墨材料基体抗氧化性能和用磷酸无机高分子复合盐处理后的内外结合的方法制备了一种抗氧化炭石墨材料。这种材料的特点是保持着炭石墨材料基体的特性如自润滑性，耐磨性、硬度、强度等，适用于高温富氧条件下长时间工作的动密封材料。参照ASTM─1179—91测试了650℃下空气中100小时的氧化失重。其氧化行为的分析结果表明，这种抗氧化石墨材料在650℃下空气中氧化失重达5％的时间为65小时，此时的氧化速率为4．4mg／g·hr。氧化60小时以后，氧化失重速率随时间的延长而迅速增加，出现了一个转折点。     

高耐蚀常温磷化液的研制

以普通的常温磷化液为基础，利用水溶性高分子覆膜，研制出一种高耐蚀常温磷化液。介绍了该常温磷化液的配方、操作条件、磷化液中各成分的作用及操作条件的控制。以丙烯酸为单体合成该水溶性高分子物质。检测了该磷化膜的耐蚀性能，结果显示，试片经该磷化液浸渍10s后，硫酸铜点滴试验时间大于60s，而浸渍15min后，硫酸铜点滴试验时间大于80s，氯化钠浸渍试验时间可达8h，表明其耐蚀性大大强于普通的常温磷化膜，可满足批量生产的需要。     

熔融渗硅对石墨氧化行为的影响

分别在500 ℃、700 ℃、900 ℃及1 100 ℃空气条件下,对石墨及渗硅石墨进行氧化实验,以分析熔融渗硅对等静压石墨氧化行为的影响。采用扫描电镜(SEM)分析了样品表面及内部形貌,通过压汞法表征了样品的孔隙结构,并对材料的力学性能进行了测试分析。结果表明:500 ℃条件下,石墨和渗硅石墨均未发生明显的氧化失重现象;温度为700 ℃时,石墨的氧化失重率随时间延长明显增加,而该温度下渗硅石墨的氧化失重率变化较小。而且,渗硅石墨在700 ℃时仍能保持较好的强度,而此温度下,石墨随氧化时间的延长,强度明显降低,甚至被氧化成粉末状。因此,熔融渗硅在提高材料抗氧化性能的同时能够显著提升材料的强度。     

Oxidation protective MoSi2-SiC-Si coating for graphite materials prepared by slurry dipping and vapor silicon infiltration

A novel kind of dense MoSi₂-SiC-Si coating was prepared on the surface of graphite substrate by slurry dipping and vapor silicon infiltration process. Mo-SiC-C precoating was fabricated via slurry dipping method, and then MoSi₂-SiC-Si coating with dense structure consisting of Si, MoSi₂ and SiC was obtained by vapor silicon infiltration process. The isothermal oxidation tests at temperatures from 800 to 1600 °C and TGA test from room temperature to 1500 °C were used to evaluate the oxidation resistance ability of the MoSi₂-SiC-Si coating. The experimental results indicate that the prepared coating has good oxidation protection ability at a wide temperature range from room temperature to 1600 °C. Meanwhile, the oxidation of the coated samples is a weight gain process at temperatures from 800 to 1500 °C due to the formed SiO₂ layer on the surface of coating. After oxidation for 220 h at 1600 °C, the weight loss of the coated sample was only 0.96%, which is considered to be the excessive consumption of the outer coating and the appearance of defects in the coating. Two layers can be observed in the coating after oxidation, namely, SiO₂ layer and MoSi₂-SiC-Si layer.     

无机复合涂层对碳纤维性能的影响

采用溶胶-浸渍法在碳纤维表面制备了二氧化钛-二氧化硅复合涂层。考察了钛溶胶与硅溶胶体积比、浸渍方式、浸渍次数对涂层的影响。利用X射线衍射（XRD）、扫描电镜（SEM）和透射电镜（TEM）分析了涂层的相组成及形貌。通过静态等温氧化实验考察了复合涂层碳纤维的抗氧化性能。结果表明：钛溶胶与硅溶胶体积比为15∶1条件下采用真空超声浸渍3次,制备的复合涂层均匀、完整、致密,与碳纤维表面结合良好,涂层抗氧化性能好,涂层二氧化钛为锐钛矿型、二氧化硅为无定型。将复合涂层碳纤维在400 ℃连续氧化15 h,其质量损失率仅为5.91%。     

鳞片石墨对环氧涂层强度和吸水性能的影响

分别研究了含不同质量分数鳞片石墨的环氧涂层的剪切强度以及经冷热水循环浸泡后涂层的重量吸水率与浸泡时间、浸泡72h后涂层的体积变化率、密度和鳞片石墨质量分数的关系。结果表明,随着石墨含量的增加,涂层剪切强度急剧降低,在w(石墨)=10%处达最低值,之后逐渐升高。当w(石墨)=20%时,涂层剪切强度较大。涂层重量吸水率随浸泡时间的增加而增大,并呈现周期性变化(以每24h为周期)。同时,随着石墨含量的增大,涂层吸水率降低。不同石墨含量的涂层浸泡72h后其体积变化率随石墨含量的增加呈现双峰特征,当w(石墨)=20%时,其体积变化率较低,为2.8%。浸泡前和浸泡72h后,涂层密度随石墨含量的增加均呈现先下降后增大的趋势,而且,两者在石墨含量为5%处的密度几乎相等。解释了涂层中不同石墨含量对其强度和耐水性的影响。涂层中适宜的石墨含量为20%。     

Oxidation protection of graphite materials by single-phase ultra-high temperature boride modified monolayer Si-SiC coating

To improve the oxidation resistance of Si-SiC coating, single-phase ultra-high temperature boride (ZrB₂ or TaB₂) modified Si-SiC coating was designed and established on graphite substrates by combination of dipping and reactive infiltration process. ZrB₂ or TaB₂ phase was introduced in Si-SiC coating by directly mixing raw materials and phenol formaldehyde resin in the slurry, and then the ZrB₂-SiC-Si and TaB₂-SiC-Si coatings were fabricated on the graphite samples by dipping-curing, pyrolysis, and siliconizing. The crystalline phases and microstructure of the as-obtained multiphase coatings were investigated by X-ray diffraction analysis and scanning electron microscopy. The interrupted oxidation tests from room-temperature to 1500?°C were conducted to assess the anti-oxidation property of the prepared coatings. After 1200?h of oxidation at 1500?°C in air (30 times thermal cycles), the mass losses of the graphite substrates coated with ZrB₂-SiC-Si and TaB₂-SiC-Si coatings were 0.086% and 0.537%, respectively, and the high-temperature stability of the modified coatings was greatly improved compared to the Si-SiC coating. The excellent anti-oxidation performances of the compound coatings were attributed to the compact structure of the coatings and the formation of compound oxide layers covering on the surfaces. The compound Zr-Si-O and Ta-Si-O films possessed low oxygen diffusion rate and appropriate viscosity, which can provide appreciable oxidation protection for the internal coatings, thus obtaining the excellent oxidation and spallation resistance property.     

热漫镀铝工艺及水溶液助镀剂的研究

概述了热浸铝工艺的发展状况及研究进展,讨论了熔剂法热浸镀铝的助镀工艺及助镀剂的选择,确定水溶液助镀法工艺,讨论了水溶液助镀剂的作用机理,并对浸铝钢的耐蚀性耐热性及抗氧化性进行了论述。     

Multiphase composite Hf0.8Ti0·2B2–SiC–Si coating providing oxidation and ablation protection for graphite under different high temperature oxygen-containing environments

A novel multiphase composite coating composed of Hf_0.8Ti_0·2B₂ solid solution, SiC and Si was prepared by a joint procedure of slurry method and silicon reactive infiltration (SRI). The oxidation and ablation experiments were conducted to investigate oxidation and ablation resistance of the Hf_0.8Ti_0·2B₂–SiC–Si coated graphite samples, respectively. The results revealed that the coated sample was oxidized at 1823 K for 108 h with a mass gain of 1.49%, which was ascribed to the high viscosity oxide layer improved by HfSiO₄ and TiO₂ in conjunction with dense structure of the coating, thereby presenting excellent high temperature stability. Furthermore, after 90 s ablation at 3273 K under a heat flux of 5.62 MW/m², the composite coating was not peeled off, which had mass ablation rate (MAR) and linear ablation rate (LAR) of 3.1 mg/s and 1.5 μm/s, respectively. The refractory oxide layer comprising oxides of Hf and Ti on the surface acted as an oxygen barrier, which can weaken the mechanical erosion force of oxyacetylene flame, finally protecting the inner coating and graphite matrix from further consumption.     

Resistance to oxidation of graphite silicided by reactive infiltration

In order to improve the oxidation resistance of graphite at high temperatures, graphite surfaces are modified by two silicidation processes involving reactive infiltration of molten silicon or, alternatively, of gaseous silicon monoxide.The resistance to oxidation of silicided graphite is studied by cyclic oxidation tests performed under a dry air flux at temperatures in the range 1550-1600 °C.During oxidation three successive regimes are evidenced: (i) initial growth of a passive silica layer on the continuous SiC superficial layer responsible for the remarkable oxidation resistance at 1550 °C; (ii) then, slow mass consumption in the intermediate composite SiC-C region; (iii) and finally, rapid local consumption of the underlying non-infiltrated porous graphite.The temporal stability of the silicided layer in air is analyzed and the reactions affecting this stability are identified. The analysis interprets the experimental findings in a satisfactory manner, especially the dramatical variation with temperature of silicided graphite lifetime observed in this temperature range.     

High performance coating films cured by novel penetrating method: Anionic resin paints

This study deals with a method of curing paint film at ambient temperature with a film-penetrative crosslinker. The method is based on the phenomenon that, after a wet coating film becomes thermoplastic, it is dipped in an aqueous solution of crosslinker. The crosslinker then penetrates into the film, and the film can be cured with the passage of dipping time. Herein an anionic copolymer containing diacetone acrylamide was employed as the main resin and carbohydrazide as the film-penetrative crosslinker. Cured films can be prepared with a short dipping time using this method. Excellent films were obtained when they were dipped in a suitable crosslinker solution containing the proper organic solvents (accelerator of penetration rate) and an appropriate acid (promoter of the reaction). In particular, the adhesion after the water resistance test was excellent compared with that of the coating film obtained by the two-component coating method.