Study On Preparation And Properties Of Electroless Ni-Cu-P-PTFE Anti-fouling Deposits

Fouling deposition was widely appeared on heat transfer surfaces in the operationprocess of heat exchanger. The accumulations of detrimental fouling on the surfaces ofheat transfer equipment can lead to a drastic increase of the thermal resistance andtherefore to a decreased efficiency of the heat exchanger, resulting in extreme energy andeconomic losses. Therefore, mitigating the formation of fouling has become especiallyimportant. In recent years, plenty of methods have been devoted to employing innovativesurface treatments with better anti-fouling properties to solve the fouling problems. In thisthesis, we mainly study on the anti-fouling properties of the Ni-Cu-P-PTFE deposits,which are based on the studied electroless ternary Ni-Cu-P deposits. The main contents ofthis studying are summarized as follows:(1) The electroless Ni-Cu-P-PTFE deposits with various PTFE content were preparedon mild steel (1015) substrate surface by adjusting different process parameters. Surfacemorphology, composition and deposition rate were investigated, respectively. The resultsshow that the mount of PTFE particles which been co-deposited in the deposits wouldreach maximum when the concentration of PTFE was12ml/L and continuously increasingthe PTFE concentration would result in the PTFE particles decreasing in the deposits.(2) The microstructure and the thermal stability of the deposits were analyzed basedon X-ray Diffraction (XRD) and differential Scanning Calorimeter(DSC), respectively. Theresults show that a rather broad peak at45°was observed which indicated that all theNi-Cu-P-PTFE deposits were in an amorphous structure state. The addition of PTFEparticles into the Ni-Cu-P matrix can hardly affected the microstructure of the depositsthough the grain was refined. Additionally, the activation energy of the Ni-Cu-P-PTFEdeposits drops slightly in correlation with the increase of the PTFE proportion in thedeposits.(3) The effect of PTFE content on the mechanical properties of the deposits wasassessed using MFT-4000surface property tester and MH-6Vickers hardness tester,respectively. The results show that the elastic modulus, microstructure, friction coefficientand surface smoothness of the deposits were proportional to the content of PTFE particlesin the deposits. The adhesion strengths had a declining trend with increasing the amount ofPTFE, which depends on the concentration of PTFE particles and the surfactant. Thefurther corrosion test illustrated that the anti-corrosion properties of the deposits wasinversely proportion to the content of PTFE particles in the deposits. (4) The relationship among the surface free energy, the surface roughness and theanti-fouling property was studied base on the rapid fouling adhesion experiment. Moreover,the Gray-Markov chain model was present to predict the fouling deposition, which couldprovide a reference to the cleaning of heat exchangers. The results show that theNi-Cu-P-PTFE deposits have better anti-fouling property than the un-coated mild steelsurface. The anti-fouling property of the deposit was found to correlate with the surfacefree energy values, but not the surface roughness.