Dissertations / Theses on the topic 'Aluminum Coloring'

碩士
大葉大學
機械與自動化工程學系
98
Aluminum alloys are widely used in vehicle castings, but the alloys are easily oxidized in the air and lose their performance. Anodizing treatment is utilized to solve this problem in industry. Aluminum alloy with high Si content usually hasn’t luxurious colors for conventional anodizing treated oxide film. Therefore, it is worthy to study the method of producing special luxurious colors of appearance on the aluminum alloy with high Si content by electrolytic coloring anodizing treatment. The anodized oxide film will retain high hardness and increase added value through the optimal electrolytic coloring anodizing treatment found in this study. A390 aluminum alloy which has high Si content was used to cast the stepped type casting and vehicle piston casting in this study. The electrolytic coloring anodizing treatment used H2SO4, CuSO4 and Fe2(SO4) as the solution to anodize the castings. The parameters studied in this experiment include casting thickness, current density and electrolytic coloring anodizing time. The effect of these parameters on the oxide film will be evaluated to establish the optimal conditions of electrolytic coloring anodizing treatment for A390 aluminum alloy castings. The results of this study show that the thick section of A390 aluminum stepped type casting had the largest thickness of electrolytic coloring oxide film compared to those films formed on the thin and medium sections in stepped type casting. The reasons are related to the grain size of primary aluminum. In addition, the growth rate of oxide film formed on A390 aluminum casting by electrolytic coloring anodizing film will be inhibited when the film grew to contact with primary Si particles beneath the substrate. Finally, the scalloped substrate will be formed due to the envelopment of primary Si particles in the oxide film. The thickness of electrolytic coloring anodizing film of A390 aluminum stepped type casting increases with the increase of electrolytic coloring time, but it’s hardness decreases with the time. The reason may be related to the gel layer deposited at the bottom of porous layer of oxide film. The condition to achieve maximum thickness of the oxide film is 3.9 A/dm2 current density and 65 minutes electrolytic coloring time, while the condition to achieve maximum hardness of oxide film is 1.3 A/dm2 current density and 15 minutes electrolytic coloring time. The optimal condition for the thick section of A390 aluminum stepped type casting to produce bright yellowish color of electrolytic coloring anodizing film by using H2SO4, CuSO4 and Fe2(SO4) mixed-acid solution is 2.6 A/dm2 current density and 27.5 minutes electrolytic coloring time, but for the thin and medium sections, the optimal condition to obtain the same color is 2.6 A/dm2 current density and 15 minutes electrolytic coloring time. Using the optimal conditions mentioned above to electrolytic coloring the A390 aluminum alloy pistons, it is found that the color of oxide film of small piston is dark reddish yellow, while the color of oxide film of large piston is dark blue-gray. It’s worthy to say that the colors of oxide films of pistons are different from those colors of oxide films on the stepped type castings. The causes of this difference are related to the grains at the chill zone of superficial layer on the pistons and whether the surface of pistons are machined.

碩士
大同大學
化學工程學系(所)
97
The effect of the step of electropolishing before anodic oxidation on the properties of aluminum oxide film were investigated in this study. It is expected that the addition of “electropolishing” before anodizing step can obtain a better anodic film and colored film. The experimental results show that the electropolished aluminum sheet increase the number of pores of the anodic film. And make the pores more uniform and more orderly. If electropolishing is used, the △E* value and reflectivity of the colored film are lower than without electropolishing. From corrosion test, the corrosion resistance is in the following order : (Aluminum sheet after EP) < (aluminum sheet with no EP) < (anodic film with EP) < (anodic film with no EP) < (colored film with no EP) < (colored film with EP). The optimal operating conditions for obtaining the blackest colored film are: electropolishing voltage 10Vdc, electropolishing time 30 min, anodizing current density 2A/dm2, electrolytic coloring voltage 20Vac and electrolytic coloring time 30 minutes, the lower △E value, corrosion rate and

碩士
大同大學
化學工程學系(所)
96
In this research, the effects of pore- widening time on the physical properties anodic films and colored films are investigated. It is expected that suitable pore sizes can be obtained on the alumina film by the step of pore-widening in phosphoric acid. And the best operating conditions for depositing silver ions in the pores of the anodic films are found out. It is found that, when the pore-widening time increase, anodic film thickness become thinner but pore diameter become larger, as well as hardness and gloss decrease. After electrolytic coloring, the pore-widened alumina films have low L value, gloss and reflectivity, which is lower than the films before pore-widening. The increasing of pore-widening time, electrolytic coloring time and voltage will decrease the film hardness. The corrosion test can prove that the corrosion resistance of the anodic films would be improved by electrolytic coloring. From EDS, it can find that more Ag ions can be deposited in the pores of the pore-widened anodic films. The operating conditions to obtain the blackest anodic film in this experiment are: pore-widening time 2 minutes, electrolytic coloring voltage 20VAC and coloring time 20 minutes. The colored film has the following physical properties: the lowest ΔE value of 10.30, the hardness of 523Hv, the gloss of 16.1, the thickness of 12.6μm and the reflectivity of 6.16% at the visible light wavelength.

碩士
大同大學
化學工程學系(所)
94
This study was carried out by means of the method of twice anodic treatment in the sulfuric acid and then electrolytic coloring in cupric sulfate solution. The effects of the first and second anodic treatment on the properties of the anodic films and colored films would be discussed. For the second anodic treatment, the film thickness of the anodic film is thicker than that from the first anodic treatment. But the hardness is lower than that from the first anodic treatment. Whether the first or second anodic treatment is done or not, the film thickness of the anodic films is almost not changed after the electrolytic coloring, however, the hardness decreases with the coloring times. As for the color difference of colored film, the L value from the second anodic treatment is lower than the first anodic treatment. Under the coloring voltage of 20 V, the L value of colored film from the second anodic treatment is approximately 10 and the a and b values approach to zero and hence the darkest shade of black color can be reached. From the film dissolution test and SEM, the anodic film from the second anodic treatment has the more porous and looser structure, it is suitable for coloring. From the observation of AFM, the anodic film surface from the second anodic treatment is even and the pores are enlarged. At the range of the visible light wavelength, the reflectivities of colored film from the second anodic treatment are all lower than those from the first treatment.

碩士
大同大學
化學工程學系(所)
94
This research is to investigate the effect of the annealing conditions on the physical properties of the anodic oxide film and colored film. It is expected that by taking the advantages of annealing, a better aluminum oxide layer can be obtained to proceed the electrolytic coloring for getting a black film. By the way, to find the optimum operation conditions to obtain the darkest shade of black anodic film on aluminum. Specimen of the annealed aluminum was investigated after anodizing in sulfuric acid solution and then electrolytic coloring in silver nitrate solution. The microstructure, microhardness, thickness, chromatism and chemistry elements of anodic oxide film were studied by using scanning electron microscopy (SEM), microhardness tester, electronic thickness tester, spectrophotometer and energy dispersive spectroscopy (EDS). It is found that after the annealing treatment at given temperature and time, because of the rearrangement of the surface crystalline structure, the growth condition of the anodic film can be improved. From the analysis of X-ray diffraction and the observation of SEM, it is known that the crystalline produced after the annealing is γ-Al2O3, and the structures of the pores are larger. Therefore, the anodic oxide film from annealing would be helpful for the electrolytic coloring in the silver nitrate solution, hence the lowest L-value of 10.32 and the minimum reflectivity of 5.54 % were obtained. To obtain the better black film on aluminum, the best operating conditions are as follows: annealing temperature of 500 ℃ for 2hr, anodic current density of 2 A/dm2 at bath temperature of 20 ℃.

博士
逢甲大學
材料科學與工程學系
107
As compared to conventional anodizing processes, micro-arc oxidation (MAO) can be used to prepare ceramic oxide films with higher hardness, excellent corrosion resistance, and favorable ceramic texture. However, limited color for the as-prepared MAO layer have restricted its application in many cases, especially consumer electronic products. A coloration method applied to MAO layer while retaining its ceramic surface texture shall significantly add the value of the existing MAO technique. An innovative post-dyeing treatment for MAO treated aluminum alloy was developed in this study. This begins with a cathodic treatment of MAO treated aluminum alloy in a NaCl solution at 20-30 V, followed by anodic dyeing with a constant current of 1 A in an anionic dyeing solution. Based on microscopic analysis and observations, the chiseled micropores created during the cathodic treatment allowed the anionic dyes to adsorb onto the MAO layer during anodic dyeing, thus making the MAO layer dyeable. High color saturation can be achieved after the colored MAO sample. The chromaticity value obtained using a commercial blue dye is (L * a * b *) = (53.55, 1.17, -29.16), while it is (75.93, -2.59, 35.63) and (65.54, 24.05, 11.32), respectively when using commercial green and red dyes.

碩士
大同大學
化學工程學系(所)
97
In this research, using twice anodization on aluminum and adding citric acid in an anodizing electrolyte simultaneously is the purpose to obtain a better pore structure than the process of once anodization. And the best operating conditions to obtain a blacker anodic film using electrolytic coloring solution of CuSO4 or AgNO3 had been found out. The experimental results show that, the larger and more orderly pores structure after the second anodization are obtained. Using the second anodization brfore the process of electrolytic coloring has many benefits to the properties of the colored film than using the first anodization, like film thickness, chromatism, reflectivity and anticorrosion. Electrolytic coloring in AgNO3 solution has the advantage of short reaction time and lower operating voltage to obtain blacker film than coloring in CuSO4 solution. The best operating conditions to obtain the blackest film are：the second anodizing current density of 2A/dm2 , the electrolytic coloring voltage of 25V in CuSO4 and coloring time of 30 min, it has a △E* value of 8.39; For the electrolytic coloring solution in AgNO3, the coloring voltage of 25V and coloring time of 20 min are the best operating conditions to obtain the blackest film with △E* value of 7.76.

碩士
大同大學
化學工程研究所
90
The aluminum sheets were through the anodic oxidation and electrolytic coloring in cupric sulfate solution and then sealed five methods of hot water sealing, nickel acetate sealing, sodium silicate sealing, chromate sealing and nickel fluoride sealing with modification of ammonium molybdate. The effects of various sealing process on the anodic film are studied. As a result, it can decrease the color differences after all sealing processes with adding a few amount of ammonium molybdate. And the film-weight difference changes little after all sealing process. Hot water sealing, nickel acetate sealing and sodium silicate sealing can improve the film microhardness with modification of ammonium molybdate. The sodium silicate sealing is specially good in resistance corrosion. Additionally, the pH value of sealing solution is an important factor for the sealing condition. Different pH value of sealing solution is suitable for different sealing process.

碩士
大同大學
化學工程研究所
91
In the study, the anodic oxidation process was achieved in 200 g/L sulfuric acid solution by a pulsed densities of 5 A/dm2 with a constant frequency of 1000 Hz, a duty cycle of 80%, and the duration time was 15 minutes at 20 ℃. After oxidation, the anodic film thickness of 20 ± 2 μm was obtained. Then, the anodic oxide aluminum was electrolyzed in a solution containing copper salts. And the factors, such as concentration and temperature of electrolyte, coloring alternating current voltage and electrolytic duration time, and so forth, that influence on the black electrolytic coloring are studied to produce a very black coatings on aluminum. The results show that the optimal concentration of electrolytic coloring solution is composed of 35 g/L cupric sulfate, 10 g/L sulfuric acid and 2 g/L sodium sulfate. The blackest colored film was carried out under the following operating conditions: bath temperature of 40 ℃; alternating current voltage of 30 V; and time of electrolytic coloring of 50 minutes. Besides, by the test within the extent of wavelengths of visible lights, black anodic oxide films of minimum reflectivity of about 3% of visible lights could be obtained. In addition, the operating condition of coloring bath temperature is the most important factor to influence the L-value, reflectivity and film microhardness. From corrosion test and SEM, the structure of the colored film from higher coloring bath temperature is looser and softer; and has the worse corrosion resistance than that from lower coloring bath temperature.

碩士
大同大學
化學工程學系(所)
95
The aluminum materiel can produce plane film with larger pores after the secondary anodic treatment. The application of silver nitrate as the electrolytic solution of the electrolytic coloring has the advantage of obtaining pure black anodic film by applying low coloring voltage, short time and dilute concentration. In this research, effects of using respectively silver nitrate and copper sulfate in the electrolytic solution for the electrolytic coloring after the secondary anodic treatment are investigated and the comparison of the properties of the film after coloring are studied. The results show that by applying silver nitrate as the electrolytic solution at an electrolytic voltage of 15Vac, the lowest L-value can be obtained; besides, a-value and b-value approach to zero, the aluminum oxide film has the effect of being in near to purely black. Both the coloring time and the voltage do not have any effect on the film thickness, whereas, it’s the current density of the anodic treatment that has the effect on the thickness of the film. As for the hardness, the larger the electrolytic coloring time or the larger the electric voltage, the hardness of the aluminum oxide film would be worse. With SEM it is known that larger and more pores are produced from secondary anodic treatment than those from primary anodic treatment, and that large quantity of metal ions precipitates into pores on the surface of the coloring film. As for the reflectivity, it is measured that with the silver nitrate solution for the electrolytic coloring, the reflectivity within the range of 600~700 nm is lower than that with the copper sulfate solution. From the dissolution film test, it is known that stronger structure can be obtained by using silver nitrate in the electrolytic solution. Furthermore, according to the corrosion test, better anticorrosion effect can be obtained by using silver nitrate solution for the electrolytic coloring and that the best anticorrosion effect occurs at the anodic current density of 2A/dm2. Through the secondary anodic treatment at the anodic current density of 2A/dm2, by applying silver nitrate as the electrolytic solution, under the coloring voltage of 15Vac and coloring time of 15 min, these are the best operating conditions to obtain a black film with △E value of 9.60, L-value of 9.56, a-value of 0.83, b-value of -0.09, and the lowest reflection of 5.55% within the visible light of 580 nm. Therefore, the best absorption effect is obtained.

碩士
大同大學
化學工程學系(所)
96
The effects of the addition of organic acid in an anodizing electrolyte on the properties of aluminum oxide film were investigated in this study. It is expected that the additions of organic acid in electrolytic can obtain better anodic film and colored film. The experimental results show that the additions of citric acid and malonic acid would increase the thickness of anodic film. This can be attributed to the fact that citric acid and malonic acid could reduce the dissolution of anodic film. Additions of organic acid could also increase the hardness. From SEM images, additions of organic acid could lead to more and smaller pores on anodic coatings. The anodic film become dense, therefore, after electrolytic coloring, the △E value and gloss become lower. From corrosion test, addition of organic acid could increase the corrosion resistance and improve the properties of anodic film after electrolytic coloring. The optimal operating conditions for obtaining a black colored film are: anodizing current density 2A/dm2, 60g/L of citric acid, anodizing time 30 minutes, alternating current voltage of electrolytic coloring 25V and electrolytic coloring time 30 minutes, the lower △E value, reflectivity, gloss and corrosion rate would be obtained. Those values are respectively 8.5, 6.13%, 6.25 and 2.9053E-11 Amp/cm2. The addition of organic acid into electrolytic anodizing solution is surely beneficial to the subsequent black colored treatment.

碩士
大同大學
化學工程學系(所)
96
This study was carried out by means of the method of two-step anodic treatment in the sulfuric acid solution with the addition of 5-sulfosalicylic acid and then electrolytic coloring in cupric sulfate solution，it is expected that by adding 5-sulfosalicylic acid and technique of two-step anodic treatment, a dense and regular oxidizing film on aluminum can be obtained and that the optimum operating conditions for obtaining a blackest film are found out. It is found that at the coloring after the anodic treatment by adding 5-ssa, the thickness of the anodized colored film would become thinner than that without the addition，but it would become thicker after two-step anodic treatment by adding 5-ssa. And，the hardness of anodic film from the addition of 5-ssa is larger than that without the addition, but it would become lower after two-step anodic treatment by adding 5-ssa. From SEM、 AFM and corrosion test of the anodic film after two-step anodic treatment by adding 5-ssa,it found out that the anodic film is more regular, smoother and denser, so it has the lowest △E after the coloring. It proves that more cupric ions deposit in the anodic film after two-step anodic treatment by adding 5-ssa. At the anodic current density of 2 A/dm2 and the duration time of 20 minutes after two-step anodic treatment by adding 5-ssa, the best operating conditions of electrolytic coloring are：alternating current voltage：30V, and electrolytic coloring time：40 minutes, hence, the lowest △E value is 7.41. The average reflectivity, gloss, film thickness, hardness and corrosion rate are respectively 4.50%、8.6、10.2μm、591Hv and 3.1875E-9 Amp/cm2.

碩士
大同大學
化學工程學系(所)
95
In the research, the effects of the addition of 5-sulfosalicylic acid in the sulfuric acid solution on the physical properties of the anodic film and the colored film are investigated, with the hope that by adding 5-sulfosalicylic acid, better oxidizing film on aluminum can be obtained and that it is favorable to carry out the best operating conditions for the black electrolytic coloring are searched. From the experimental results, it is found that at the coloring after the anodic treatment by adding 5-sulfosalicylic acid, the thickness of the anodic film would become thinner than the thickness without the addition and that the hardness would become larger than the hardness without the addition. It is also known from the cross-sectional and SEM of the anodic film obtained by adding 5-sulfosalicylic acid that the barrier layer is more regular and denser and that the pores of the porous layer are smaller, showing that the whole anodic film is denser. Besides, the corrosion test and the film dissolution test prove that the addition of 5-sulfosalicylic acid can effectively enhances the anticorrosive property of the anodic film and thus improves the characteristics of the black film after coloring. At the current density of the anodic treatment of 1 A/dm2, and 20 minutes after the anodic treatment by adding 5-sulfosalicylic acid, the best operating conditions of electrolytic coloring are：alternating current voltage：30V, and electrolytic coloring time：40 minutes, hence, the lowest △E value, reflectivity, gloss, corrosion rate and the better hardness can be obtained. Those values are respectively 9.18, 5.08%, 6.4, 4.9576E-10 g/m2-h and 639Hv, accordingly, the characteristics of the black colored film are greatly improved.

碩士
大同大學
化學工程學系(所)
98
Anodized aluminum after film were dissolved, then, again dealing with anodization, such anodization gradually been studied in recent years. In this studies, using mixed acid (5-sulfosalicylic acid and sulfuric acid) as the anodizing electrolyte solution, and the second、the third anodization of dealing with anodizing. The electrolytic coloring using copper sulfate solution as electrolyte. The study of effect of re-anodized colored film properties, is purposes to obtain good properties of the oxide film in order to help carry out the electrolytic coloring, and find the best operating conditions of blacker film. It was found that anodized aluminum by the third anodization obtain more regular arrangement of pores in oxide film. The properties of film, better than the previous anodization of film in many ways. (such as: thickness, color, hardness, anticorrosion etc. ). In the anodizing current density of 2A/dm2 , the oxide film will form a large number of pores, and has a good coloring effects, especially with the third anodic current density 2A/dm2 has a minimum of L * and △ E , 8.85 and 10.34 respectively. While the colored film dealt with the current density 3A/dm2 and the third anodizing, has the highest hardness,465.93Hv, and also has a better corrosion resistance.

OBJECTIVES: To investigate the effect of different alumina fabrication techniques and sintering temperatures on the biaxial flexural strength. Also, to assess the resulting color of multiple metal salt solutions at different concentrations in monolithic alumina and its effect on the optical properties of the restoration. MATERIAL & METHOD: Forty disk-shape alumina specimens were divided into 4 groups (n=10) based on the fabrication process (slip cast or die press) and sintering temperature (1530°C or 1600°C). Biaxial flexural strength was calculated using universal testing machine at a crosshead speed rate of 0.5 mm/min until failure occurred. For the coloring part of the study, nine elements (Ba, Ce, Cr, Fe, Mn, Nd, Pr, Sm, Zn) were used to form metal-salt coloring solutions at a concentration of 0.1%, 1% and 5% wt. The solutions were then used to infuse 162 pre-sintered porous alumina disks that are either slip-casted (A1000) or die-pressed (CT3000). Color coordinates were recorded in CIE L*a*b* system using spectrophotometer. Color differences relative to the control (ΔE), translucency parameter (TP), contrast ratio (CR) and total transmission were calculated and analyzed using two-way analysis of variance (ANOVA) with Tukey post hoc test at α = 0.05. RESULTS: Slip cast group sintered at 1530°C had the highest flexural strength (479.14 MPa), but there was no significant difference between the four groups neither by fabrication process (p = 0.127) nor by sintering temperature (p = 0.276). Die press specimens colored with Ba at 0.1% and 1% showed significantly higher TP (2.65 and 2.49) and lowest CR (96.15 and 96.30) among the groups. There was a statistically significant effect on TP and CR when changing alumina powder on specimens colored by Ba, Ce, and Zn (p < 0.05). Changing the concentration of the coloring solution caused a significant effect on the optical properties of specimens colored by Ba, Nd, Cr, Mn. ΔE was significantly changed when changing alumina powder and coloring concentration for all elements except Ce, Pr, and Sm. CONCLUSION: Changing fabrication method and sintering temperature did not affect the biaxial flexural strength. However, the fabrication method and metal-salt colorant concentration affected the optical properties of the specimens.
https://hdl.handle.net/2144/35681