發(fā)布時間：2018-06-25 16:45

  本文選題：顆粒 + 包覆改性�。� 參考：《南京航空航天大學》2015年博士論文

【摘要】：添加潤滑顆粒(如Mo S2)或硬質(zhì)顆粒(如金剛石)的化學復合鍍層具有優(yōu)異的摩擦磨損性能,工業(yè)應用前景廣闊。目前制備復合鍍層過程中普遍使用表面活性劑改善微細顆粒在化學鍍液中潤濕性及分散特性,然而使用表面活性劑也存在負面作用,影響復合鍍層性能進一步提升。針對這一問題,本課題提出用顆粒表面包覆改性的方法解決顆粒潤濕性及分散問題,主要研究工作及成果:1、采用非均勻形核法對金剛石和Mo S2顆粒進行表面包覆改性;利用掃描電鏡(SEM)、熱重/差熱同步熱分析儀(TG/DSC)、x射線衍射儀(XRD)等手段對改性顆粒進行表征;測試了顆粒改性前后在化學鍍液中zeta電位及懸浮穩(wěn)定性。結(jié)果表明:金剛石和Mo S2顆粒表面均成功包覆了Al(OH)3層,包覆顆粒表面形貌明顯變化;包覆層及350℃煅燒產(chǎn)物均為非晶態(tài)結(jié)構(gòu),產(chǎn)物為亞穩(wěn)態(tài)氧化鋁;改性金剛石和改性Mo S2顆粒等電位點均遠離了化學鍍液p H值(酸性鍍液p H約5.0),在該p H值范圍內(nèi)改性顆粒zeta電位大于未改性顆粒的,提高了改性顆粒在化學鍍液中的懸浮液穩(wěn)定性。2、基于Washburn方程采用薄板毛細滲透法測量了金剛石和Mo S2顆粒改性前后對各種探針液體的接觸角,并利用YGGF方程計算顆粒改性前后的表面自由能及其分量;提出了一個判斷顆粒改性前后親水/疏水性變化的判據(jù)。結(jié)果表明:改性Mo S2顆粒對水的接觸角由70.8?減小為55.2?,潤濕性提高;改性金剛石接觸角由44?增大到48.5?,潤濕性略下降;未改性Mo S2表面能及其分量與有類似表面及結(jié)構(gòu)的Talc表面能接近;而改性Mo S2和改性金剛石表面能則與氧化鋁表面能一致;酸性分量與堿性分量之比(?+/?-)作為一個新的判據(jù)均適用于兩種顆粒改性前后親水性變化的表征。3、利用DLVO理論(和XDLVO理論)建立了化學鍍液中顆粒間相互作用模型;預測了金剛石和Mo S2兩種顆粒改性前后在化學鍍液中的分散穩(wěn)定性;計算了顆粒改性前后相互作用力變化;以顆粒沉降實驗及粒度分布演變驗證了模型。結(jié)果表明:化學鍍液中顆粒間相互作用位能曲線特征可以很好地預測化學鍍液分散體系的穩(wěn)定性�；瘜W鍍液及低稀釋比例鍍液中,顆粒作用位能曲線不存在勢壘,顆粒在任何間距均為引力作用,因此易團聚而快速沉降;隨化學鍍液稀釋比例增大,位能曲線出現(xiàn)較大正勢壘,此時顆粒能保持單分散狀態(tài),沉降速率慢而穩(wěn)定分散效果明顯,其中未改性金剛石穩(wěn)定懸浮至少稀釋100倍,未改性Mo S2至少200倍。改性顆粒在化學鍍液及稀釋鍍液中都沒有大的正勢壘,不能穩(wěn)定懸浮;但在化學鍍液中,改性顆粒間總作用引力明顯小于未改性顆粒的,更易于實現(xiàn)顆粒的動態(tài)穩(wěn)定分散。4、利用湍流理論和團聚體強度理論建立了化學鍍槽中流體與顆粒間作用模型;分別采用團聚體靜態(tài)結(jié)合強度和動態(tài)結(jié)合強度與不同湍流尺度區(qū)域流體應力進行比較,判斷團聚體被流體破碎分散的可能性;并通過測量流場中顆粒粒度分布進行模型驗證。結(jié)果表明:團聚體動態(tài)結(jié)合強度模型可以很好地預測流場中顆粒團聚體的分散狀態(tài),與實際粒度分布特征相一致;化學鍍槽中流場中團聚體穩(wěn)定性與原始顆粒粒徑,團聚體直徑及攪拌強度都有關(guān);相同條件下,改性顆粒團聚體比未改性顆粒團聚體更易于破碎分散。5、未使用表面活性劑制備了含改性顆粒Ni-P-Mo S2/Al2O3化學復合鍍層,對鍍層組織形貌特征及摩擦磨損性能進行了評價,并與Ni-P-Mo S2化學復合鍍層進行了對比。結(jié)果表明:含改性Mo S2顆粒的復合鍍層的顯微硬度、摩擦系數(shù)及磨損量均與其表面形貌特征相關(guān),而表面形貌特征取決于制備時的攪拌強度和顆粒包覆率,其中攪拌速率為700rpm,顆粒包覆率為7%時制備的鍍層表面組織致密,400℃熱處理后硬度最高可達958Hv,且摩擦系數(shù)和磨損量都較小;顆粒改性前后在鍍層中沉積部位不同,改性顆粒主要分布在鍍層表面胞狀體內(nèi)部和表面,而未改性顆粒主要在胞狀體根部,也影響復合鍍層形貌及性能;含改性Mo S2復合鍍層比含未改性顆粒鍍層具有相對低的摩擦系數(shù)和磨損量,進一步提升了性能。
[Abstract]:The chemical composite coatings (such as Mo S2) or hard particles (such as diamond) have excellent friction and wear properties and have a bright future in industrial applications. At present, surface active agents are widely used in the process of preparation of composite coatings to improve the wettability and dispersion of fine particles in the electroless plating solution. However, the use of surfactants also has negative effects. Surface action affects the performance of composite coating further. Aiming at this problem, this topic proposes to solve the problem of particle wetting and dispersing with the modified method of particle surface coating. The main research work and results are as follows: 1, the surface coating of diamond and Mo S2 particles is modified by non-uniform nucleation method; the thermal weight / differential heat is used by scanning electron microscope (SEM). The modified particles were characterized by synchronous heat analyzer (TG/DSC) and X ray diffractometer (XRD). The zeta potential and suspension stability in the electroless plating solution were tested before and after the modification. The results showed that the surface of the diamond and Mo S2 particles were successfully coated with 3 layers of Al (OH), the surface morphology of cladding particles was obviously changed, and the calcined products of the coating and 350 C were calcined. The amorphous structure is amorphous, the product is metastable alumina, and the potential points of modified diamond and modified Mo S2 particles are all far away from the P H value of the electroless plating solution (acidic solution P H about 5). The zeta potential of the modified particles in the P H value is larger than that of the unmodified particles, and the stability of the suspended particles in the electroless plating solution is enhanced by.2, based on Washburn square. The contact angle between the diamond and Mo S2 particles was measured before and after the modification of the diamond and Mo particles, and the surface free energy and its components before and after the modification of the particles were calculated by using the YGGF equation, and a criterion to judge the hydrophilic / hydrophobicity of the particles before and after the modification was proposed. The results showed that the modified Mo S2 particles were in contact with water. The angle is reduced from 70.8 to 55.2, the wettability is increased, the contact angle of modified diamond is increased from 44 to 48.5, and the wettability is slightly decreased; the surface energy and its component of the unmodified Mo S2 are close to the Talc surface with similar surface and structure, while the surface of the modified Mo S2 and the modified diamond surface can be consistent with the alumina surface; the ratio of acid and alkaline components (? +) As a new criterion, it is applicable to the characterization of the hydrophilic change of two kinds of particles before and after the modification of.3. Using the DLVO theory (and XDLVO theory), the interparticle interaction model in the electroless plating solution is established, and the dispersion stability of the two particles in the electroless plating solution before and after the modification of the diamond and Mo S2 particles is predicted, and the interaction between the particles before and after the modification of the particles is calculated. The results show that the characteristics of the interparticle interaction potential curve in the electroless plating solution can predict the stability of the electroless plating solution well. The potential energy curve of the particles in the electroless plating solution and the low dilution ratio plating bath has no potential barrier and particles at any distance. All of them are gravitational, so it is easy to gather and settle quickly. With the increase of the dilution ratio of the electroless plating solution, the potential energy curve has a larger positive barrier. At this time, the particle can maintain a single dispersion state, the settling rate is slow and the stable dispersion effect is obvious, in which the unmodified diamond is stabilized at least 100 times, and the unmodified Mo S2 is at least 200 times. There is no large positive barrier in both the plating bath and the diluted solution, and the suspension is not stable. However, in the electroless plating solution, the total effect of the modified particles is less than that of the unmodified particles, and it is easier to realize the dynamic and stable dispersion of.4. The possibility of breaking and dispersing the fluid in the aggregate is judged by the comparison of the static bond strength and dynamic bond strength with the fluid stress in different turbulent scale regions, and the particle size distribution in the flow field is measured by the model. The results show that the dynamic combined strength model of the aggregate can be used to predict the flow in the flow field well. The dispersion state of the particle aggregates is in accordance with the actual particle size distribution characteristics. The stability of the aggregate in the flow field in the electroless plating bath is related to the original particle size, aggregate diameter and agitation strength. Under the same condition, the modified particle aggregate is more easily broken and dispersed.5 than the unmodified particle aggregate, and the modifier is prepared without using surface active agent. The microstructure and friction and wear properties of the coated Ni-P-Mo S2/Al2O3 composite coating were evaluated and compared with the Ni-P-Mo S2 chemical composite coating. The results showed that the microhardness, friction coefficient and wear amount of the composite coating containing modified Mo S2 particles were related to the surface morphology and surface morphology characteristics. It is determined by the stirring strength and the coating rate of the particles, in which the stirring rate is 700rpm, the coating surface is dense when the coating rate is 7%, the hardness of the coating is up to 958Hv after heat treatment at 400 C, and the friction coefficient and the wear amount are smaller, and the deposited parts in the coating are different before and after the particle modification, and the modified particles are mainly distributed in the coating. The inner and surface of the surface of the surface, while the unmodified particles are mainly in the root of the cell, also influence the morphology and properties of the composite coating, and the modified Mo S2 composite coating has a lower friction coefficient and wear amount than the unmodified particle coating, and further improves the performance.
【學位授予單位】：南京航空航天大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB306

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