本文選題：鈷包碳化鎢粉體 + 間歇電沉積��； 參考：《湖南大學(xué)》2016年碩士論文

【摘要】：間歇電沉積是一種新興的合成金屬-粉體復(fù)合材料的技術(shù)。在電沉積溶液中加入不溶性固體顆粒,通電時由于粉體顆粒覆蓋在陰極表面,金屬離子在向陰極移動的同時在粉體表面得到電子而還原成金屬,形成具有優(yōu)異性能的核-殼結(jié)構(gòu)的金屬包覆粉體復(fù)合材料。本文在間歇電沉積方式下,選取WC顆粒為內(nèi)核,鈷為金屬外殼,在鈮板基體上制備Co包WC復(fù)合粉體。主要研究了電流密度、表面活性劑、pH值等參數(shù)與粉體性能之間的關(guān)系,確定了電沉積Co包覆WC復(fù)合鍍層的最佳工藝參數(shù)；利用光學(xué)顯微鏡、掃描電鏡(Scanning Electron Microscopy)、能譜儀(Energy Dispersive Spectroscopy)和X射線衍射儀(X-ray diffraction)等手段對復(fù)合鍍層的表面形貌、化學(xué)成分和相結(jié)構(gòu)進(jìn)行了觀察和分析。結(jié)果表明,Co能夠均勻地包覆在WC顆粒表面上,且結(jié)合緊密；復(fù)合鍍層均為晶態(tài)結(jié)構(gòu)。當(dāng)鍍液中沉積電流密度為16A·dm-2時,電沉積復(fù)合粉體的電流效率和鈷含量均達(dá)到最大,分別為47.50%和89.81%,得到了包覆均勻的鈷包碳化鎢復(fù)合粉體。主要結(jié)果如下：(1)通過簡單的混酸處理方法對WC粉體進(jìn)行前處理,利用SEM觀察前處理前后的WC粉體表面形貌,以EDS和XRD圖對簡單前處理過后電沉積的WC/Co復(fù)合粉體表征和分析,結(jié)果表明混酸是通過在WC表面形成階梯狀的缺陷來活化WC粉體的表面的。(2)利用電流效率、表面形貌復(fù)合粉體的鈷含量、電沉積速率等結(jié)果來優(yōu)化電沉積鈷包碳化鎢粉體的最佳電流密度、單次電沉積時間、pH值等工藝條件。pH值對WC粉體的鈷的晶體結(jié)構(gòu)有著極大的影響,保持鍍液pH值為4-5時,能夠得到沉積速率快,電流效率高,均勻分散的鈷包碳化鎢復(fù)合粉體。(3)利用恒電位暫態(tài)階躍法研究在大電流密度下,鈷在碳化鎢上沉積的三維成核機理。(4)加入適當(dāng)表面活性劑,吸附在陰極表面,能夠改變鈷的沉積電勢,增大陰極表面極化。根據(jù)紅外圖譜,PEG-2000極易吸附于WC粉體表面,通過本身長鏈的空間位阻效應(yīng)來得到均勻分散的鈷包碳化鎢復(fù)合粉體。
[Abstract]:Intermittent electrodeposition is a new technology for synthesizing metal-powder composites. An insoluble solid particle is added to the electrodeposition solution. When the powder particles are covered in the cathode surface, the metal ions are reduced to metal while moving toward the cathode and obtaining electrons on the powder surface. Metal coated powder composites with core-shell structure with excellent properties were formed. In this paper, Co-coated WC composite powder was prepared on niobium substrate with WC particles as core and cobalt as metal shell under intermittent electrodeposition. The relationship between the parameters such as current density, surfactant pH value and powder properties was studied. The optimum technological parameters of Co coated WC composite coating were determined. The surface morphology, chemical composition and phase structure of the composite coating were observed and analyzed by scanning electron microscope (SEM), scanning electron microscope (SEM) and scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Co can be uniformly coated on the surface of WC particles and bonded tightly, and the composite coatings are of crystalline structure. When the deposition current density is 16A dm-2, the current efficiency and cobalt content of electrodeposited composite powders reach the maximum, which are 47.50% and 89.81%, respectively. The Co coated tungsten carbide composite powder with uniform coating is obtained. The main results are as follows: (1) WC powder was pretreated by simple mixed acid treatment. The surface morphology of WC powder before and after pretreatment was observed by SEM, and the electrodeposition of WC/Co composite powder after simple pretreatment was characterized and analyzed by EDS and XRD diagrams. The results show that the mixed acid activates the surface of WC powder by forming a step defect on the surface of WC. The optimum current density of cobalt coated tungsten carbide powder was optimized by the results of electrodeposition rate. The technological conditions such as single electrodeposition time and pH value had great influence on the crystal structure of cobalt in WC powder. When the pH value of plating solution was 4-5, The cobalt coated tungsten carbide composite powder with fast deposition rate, high current efficiency and uniform dispersion can be obtained. The three-dimension nucleation mechanism of cobalt deposited on tungsten carbide at high current density is studied by potentiostatic transient step method. Adsorption on the cathode surface can change the deposition potential of cobalt and increase the polarization of the cathode surface. According to the infrared spectra, PEG-2000 is easily adsorbed on the surface of WC powder. Through the steric resistance effect of its own long chain, the uniformly dispersed cobalt coated tungsten carbide composite powder can be obtained.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TB383.3

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