Anodic Aluminum Oxide Layer Research Articles

Influence of Alloying Elements on the Mechanical Properties of Anodized Aluminum and on the Adhesion of Copper Metallization.

The active development of the power electronics market and a constant increase in the prices of components require new materials and approaches, including a power module packaging technology. The use of aluminum instead of copper in the power module baseplate is an interesting and promising solution. The insulated metal baseplate is one of the most extensively developed technologies nowadays. The object of this study is an insulated metal substrate based on anodized aluminum. The main goal of the article is the comparison of copper topology adhesion to an anodized aluminum oxide layer formed on different aluminum alloys with aluminum content of at least 99.3 wt %. Peel test and pull-off adhesions showed a twofold difference for both aluminum alloys. The high ordered defect-free anodized alumina formed on alloys with copper content of 0.06 wt % had a mean pull-off adhesion of 27 N/mm2 and hardness of 489 HV. In the case of the alloy with copper content of around 0.15 wt %, it had hardness of 295 HV and a mean pull-off adhesion of 12 N/mm2. The results of our microstructure investigation showed that anodized alumina based on alloys with copper content of around 0.15 wt % is fragile due to spherical holes. Summing up the results, it can be concluded that not all initial impurities are critical for anodized alumina, but some, specifically copper, dramatically decreased the mechanical properties of anodized alumina.

Study of electric parameters of thin porous anodic alumina layers

Currently, the study of the electric parameters of porous anodic alumina (PAA) layers is of interest for sensor applications (humidity, DNA, etc.). PAA layers are synthesized using electrochemical anodizing of aluminum foil in potentiostatic mode with an aqueous solution of sulfuric acid and glycerin as an electrolyte. The surface morphology of the layers was studied by atomic force microscopy. The electric characteristics were studied using impedance spectroscopy at room temperature and under heating. An increase in the impedance of the heat-treated PAA sample was found, as well as an increase in the impedance with an increase in the measurement temperature. The results are explained by the influence of adsorbed water molecules on the electric characteristics of porous layers.

A Strategy towards Light-Absorbing Coatings Based on Optically Black Nanoporous Alumina with Tailored Disorder.

This work provides a conceptually new way of thinking about the light-absorbing mechanism in additive-free black porous anodic alumina (black PAA, or b-PAA) layers obtained via “burning” anodizing regime. The new insight into the controllable photonic effects in PAA allows the implementation of the optical blackening method based on the deliberate randomization of the initially well-ordered nanopore arrangement. The proposed black coloration mechanism rests solely on the destructive interference of light after its multiple scattering. Similar effects have been earlier considered for some natural or artificially created biomimetic structures (e.g., the so-called “moth eye effect”, or the coloration mechanism in the Neurothemis tullia dragonfly wings). Comprehensive analysis confirmed that the chemical composition of b-PAA has only a minor influence on the color changes and the optical density increase, and that the light-absorbing properties most likely result from the structural effects. The new functional 2D materials exhibit strong adhesion to aluminum surface, are cost-effective and suitable for application under harsh thermal or UV-light conditions. They are potentially useful for manufacturing of optical devices or heat-resistant coatings in aerospace technologies, as well as solid supports for biological filtration and fluorescence imaging.

Slippery Liquid-Infused Porous Surfaces on Aluminum for Corrosion Protection with Improved Self-Healing Ability.

Slippery liquid-infused porous surfaces (SLIPSs) can be formed by impregnating lubricants in porous surfaces with low surface energy. In this study, SLIPSs have been obtained on practically important aluminum with a porous anodic alumina layer by impregnating lubricants containing organic additives. The additive-containing lubricants change the surface slippery even without prior organic coating of the porous alumina surface. The additive-containing SLIPSs reveal a low water sliding angle of <5° and markedly improved corrosion resistance in an acetic acid solution containing chloride. The SLIPSs are formed by the in situ adsorption of the organic additives on the porous alumina surface. The scratched defects induce corrosion of the organic coating-type SLIPSs, whereas the additive-containing SLIPSs sustain high corrosion resistance even after introducing scratch defects. The adsorption of the organic additive in lubricants and refilling of the lubricant are responsible for the self-healing of the corrosion resistance. Thus, the additive-containing SLIPSs are promising self-healing corrosion-resistant surfaces.

Probing Barrier Oxide Layer of Porous Anodic Alumina by In Situ Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy (EIS) is a unique tool for both ex situ and in situ studies of the barrier layer thickness of anodic aluminium oxide (AAO). Here EIS is applied to study porous AAO formed by anodizing of high-purity Al foils in 0.3 M sulphuric acid and 0.3 M oxalic acid electrolytes. It is shown that in the high-frequency range, in situ EIS spectra coincide with the ex situ ones. Thus, the thickness of the barrier layer at the pore bases does not change after the end of the anodic polarization. The barrier layer thickness (h) is governed by the anodizing potential (U) according to the equation h = 1.03(2) nm·V−1·U + 2.2(3) nm. Features of the current transients observed during potentiostatic anodizing are discussed. It has been proved that a local maximum of current at the initial stage of anodizing corresponds to the maximum of the aluminium electroactive surface area arising due to the rearrangement of pores.

A new and facile route to prepare gold nanoparticle clusters on anodic aluminium oxide as a SERS substrate

In the present study, a new SERS-active gold nanoparticle clusters having a flower-shape have been prepared easily on nano porous anodic aluminium oxide (AAO) by immersing it in auric chloride solution without any need for complex production steps. In this process, presented for the first time, the metallic aluminum which were released under the influence of chloride ions due to pitting corrosion act as a reducing agent, while gold ions were reduced onto the AAO layer based on the difference in standard reduction potentials between aluminum and gold. Gold nanoparticle clusters on AAO layer formed “hot spots” providing enhanced Raman signal. Optical microscope, SEM, EDX, AFM, and UV–vis spectrophotometer have been used to characterize the substrate. In order to demonstrate applicability of the method, label free SERS measurements of nitrate ion was performed on the proposed sensing platform. A high sensitivity with 1.03 ppm of limit of detection level and the enhancement factor of 2.9 × 105 were obtained for nitrate ion. In addition, remarkable recoveries ranging from 98.4% to 106.8% were obtained for nitrate spiked into drinking water samples. The inter-day and intra-day precisions of the method as relative standard deviation (RSD) were determined as 3.3% and 5.2%, respectively. The sensor platform, developed using a facile method and a low-cost base material (aluminum), can be a good alternative for SERS based sensing applications.

Large-pores anodizing of 5657 aluminum alloy in phosphoric acid: an in-situ electrochemical study

In order to fine tune the morphology of an anodic network, the understanding of the basic electrochemical mechanisms involved is required. The purpose of the present paper is to study the formation of the anodic aluminum oxide (AAO) on 5657 aluminum alloy in H3PO4 when varying the electrolyte concentration (0.1 M – 2 M) and the applied voltage (0–300 V) using a combination of in situ electrochemical investigations and SEM morphological observations.Even if the anodizing voltage and the electrolyte concentration enhance the anodizing rate, the thickness of the anodic film remains limited to 13 µm whatever the electrochemical conditions. The presence of alloying elements induces morphological specificities: the cyclic accumulation/dissolution of the noble elements leads to the formation of regularly spaced transversal pores in the alumina wall. Finally, by selecting appropriate chemical and electrochemical conditions, the fabrication of AAO layer with large and regular pores (until 150 nm of diameter) is possible with a suitable growth rate (0.2 µm min−1 at 90 V in 1 M H3PO4) on the considered commercial complex aluminum alloys.

Silicon carbonitride ceramic surface-modified nanoporous aluminum alloy by preceramic polysilazane precursor for surface strengthening

Preceramic polysilazane precursor is simply coated on the anodized 7003 alloy and pyrolyzed at 400, 500 and 600 °C, respectively to form a silicon carbonitride ceramic film. The scanning and transmission electron microscopic images show that silicon carbonitride film can be detected on the surface of the anodic aluminum oxide compactly, representing a multilayer structure with the films of SiCN, SiCN with anodic aluminum oxide (AAO) layer and 7003 alloy substrate. The wear test is built-up by a stainless steel velvet head with reciprocating movement. After wearing in 2.176 km, the wear rate of the SiCN coated 7003 alloy pyrolyzed at 600 °C is about 0.003%, extremely lower than that of the anodized 7003 alloy, 0.023%. The average surface hardness and indentation modulus of elasticity can achieve higher than 6 GPa and 85–90 GPa that are twice higher than those of the anodized 7003 alloy.

Localized surface plasmon resonance and structural characteristics of Ti nanodot arrays covered with an amorphous TiO2 native oxide layer

Localized surface plasmon resonance (LSPR) of Ti nanodot arrays (NDA) has not been studied much due to the surface oxide layer. In this study, we report the LSPR of titania on titanium (TOT) NDA fabricated on an indium tin oxide (ITO) glass using an anodic aluminum oxide layer with through-holes as a shadow mask. After depositing a 50 nm thick Ti layer, the TOT NDA was revealed on the ITO glass by dissolving the mask. The surface of TOT NDA was identified as TiO2 due to surface oxidation. Using XPS depth profiling, a chemical shift from the surface to interior showed a change of 4.6 eV, which corresponded to the difference in the binding energy between the TiO2 and Ti metal at the Ti 2p core level. Thus, the TOT NDA indicated that the Ti metal core was covered with a TiO2 layer. The LSPR of the TOT NDA with an 80 nm diameter was clearly observed at ~420 nm in the visible range, demonstrating the potential application of TOT NDA as a visible light-responsive photocatalyst.

(Invited) Growth of Self-Ordered Porous Anodic Oxide Nanomaterials By Coupled Ion Migration and Viscous Flow

Porous anodic oxide (PAO) films are self-organized porous oxide nanomaterials formed by electrochemical oxidation. PAO includes porous anodic alumina and TiO2 nanotube layers. These films eventually evolve into a hexagonally-ordered array of parallel cylindrical pores or nanotubes of order 100 nm diameter, with a characteristic interpore spacing that scales directly with the cell voltage.We explore the roles of mechanical stress and oxide flow in self-ordering, through a modeling analysis of stress-driven viscous flow of oxide (1). The model is based on coupled viscous flow of oxide and stress- and electric field-driven migration of metal and oxygen ions (2). Stress at the film interfaces is generated by ion-transfer processes and relaxed by viscous flow, resulting in layers with elevated compressive or tensile stress within a few nm of the interfaces (3,4). Experimental evidence for these layers has been found from in situ stress measurements (5,6). We present linear stability analysis incorporating the surface stress boundary conditions in the coupled oxide flow-electrical migration model of Houser and Hebert (2).For porous alumina, the calculations reveal self-organized pattern formation with steady-state pore spacing-voltage scaling ratios that compare favorably to those found experimentally (1). The scaling ratios are independent of oxide viscosity or uncertainties in the values of any other model parameters. The stress driving oxide flow arises at the oxide-solution interface due to strong electrolyte anion adsorption, which blocks direct oxide deposition on the surface itself. New results for TiO2 nanotube layers are presented. Near-surface stress is not present in TiO2 nanotube layers (6); instead, compressive stress driving flow arises at the metal-oxide interface from the volume change upon conversion of metal to oxide.REFERENCES P. Mishra and K. R. Hebert, Electrochim. Acta, 340, 135879 (2020).J. E. Houser and K. R. Hebert, Nature Mater., 8, 415 (2009).K. R. Hebert, P. Mishra, J. Electrochem. Soc., 165, E737 (2018).K. R. Hebert, P. Mishra, J. Electrochem. Soc., 165, E744 (2018).Ö. Ö. Çapraz, P. Shrotriya, P. Skeldon, G. E. Thompson, K. R. Hebert, Electrochim. Acta, 167, 404 (2015).Q. Dou, P. Shrotriya, W. F. Li, K. R. Hebert, Electrochim. Acta, 292, 676 (2018).Q. Dou, P. Shrotriya, W. F. Li, K. R. Hebert, Electrochim. Acta, 295, 418 (2019).

The Role of Hydrated Alumina Layer on the Incorporation of Electrolyte Species in Anodizing of Aluminum

Hydration treatment of aluminum is often used for corrosion protection of aluminum alloys and for the formation of dielectric alumina layer in aluminum electrolytic capacitors. Hydrated alumina layer is usually formed by immersing aluminum with and without a porous anodic alumina layer in hot water. The hydrated alumina layer plays an important role in enhancing the corrosion resistance and forming crystalline γ’-alumina in subsequent barrier-type anodic film growth by anodizing. However, the properties of the hydrated layer are not yet well understood. In this study, we examined the influence of anion incorporation properties into the barrier-type anodic alumina films through the hydrated alumina layer, which was formed in hot water.High purity (99.99%) aluminum plate was used in this study. After electropolishing in a HClO4–ethanol mixed solution below 283 K, a hydrated alumina layer was formed by immersing the electropolished aluminum in hot water (95ºC) for 10 min. The resultant hydrated layer consists of two layers, comprising a flake-like outer porous layer and a relatively dense inner layer. The thickness of the hydrated layer was ~430 nm. Then the aluminum with the hydrated layer was anodized in boric acid and tungstate electrolytes to grow the barrier-type anodic films. When the boric acid electrolyte was used, boron species were incorporated into the outer part of the barrier-type anodic films through the hydrated alumina layer. In contrast, no incorporation of tungsten species into the barrier-type anodic film through the hydrated layer occurred in the tungstate electrolyte. Phosphate anions are known to be incorporated into the 70% of the film thickness in the anodic amorphous alumina film, but in the present study, phosphate anions were not incorporated into the barrier-type anodic films through the hydrated layer. It is likely from the GDOES elemental depth profile analysis suggests that the inner hydrated layer becomes a barrier for the incorporation of tungsten and phosphorus species. Thus, apparently, the inner hydrated alumina layer has cation-selective permeation properties so that anion incorporation is limited. In boric acid electrolyte, the acid dissociation is limited, and non-charged boric acid species can be penetrated through the hydrated layer.

Long-Range Hexagonal Pore Ordering as the Key to Controlling SERS Efficiency in Substrates Based on Porous Alumina

Self-organized porous anodic alumina (PAA) layers have been previously suggested as effective surface-enhanced Raman scattering (SERS) substrates, which exhibit high enhancement factors when coated...

Porous Aluminium Oxide Coating for the Development of Spectroscopic Ellipsometry Based Biosensor: Evaluation of Human Serum Albumin Adsorption

An electrochemically synthesised porous anodic aluminium oxide (pAAO) layer has been analysed by means of spectroscopic ellipsometry. The determined thickness of the formed pAAO layer obtained from spectroscopic ellipsometry measurements and modelling was 322.75 ± 0.12 nm. The radius of the nanopores estimated from SEM images was 39 ± 5 nm and the distance between nanopores was 107 ± 6 nm. The investigation of human serum albumin (HSA) adsorption on the pAAO coating showed that: (i) the protein concentration inside nanopores, depending on exposure time, approximately was from 200 up to 600 times higher than that determined in buffer solution; (ii) the initial phase of the adsorption process is slow (3.23 mg·cm−3·min−1) in comparison with the protein desorption rate (21.2 mg·cm−3·min−1) by means of pAAO layer washing; (iii) conventional washing with PBS solution and deionised water does not completely remove HSA molecules from pAAO pores and, therefore, the HSA concentration inside nanopores after 16 h of washing still remains almost 100 times higher than that present in PBS solution. Thus, due to such binding ability, HSA can be successfully used for the blocking of the remaining free surface, which is applied for the reduction in non-specific binding after the immobilisation of biorecognition molecules on the pAAO surface. It was determined that some desorption of HSA molecules from the pAAO layer occurred during the sensor’s surface washing step; however, HSA concentration inside the nanopores still remained rather high. These results recommend the continued application of pAAO in the development of biosensors.

Relaxation Kinetics of Plasma Electrolytic Oxidation Coated Al Electrode: Insight into the Role of Negative Current

Plasma electrolytic oxidation (PEO) is an advanced coating process based on high-voltage anodizing. Notwithstanding the anodic nature of the PEO process, it is known that negative polarization leads to synergetic effects in oxide formation efficiency and characteristics of resulting coatings. In this work, we used dynamic anodic voltammograms derived from polarization signal, combining working and diagnostic segments to evaluate in real time the effects of negative polarization on the formation of PEO on the coating on Al in the bipolar regime with a frequency of 50 Hz and a negative-to-positive charge ratio of 1.3. It was found that the hysteresis between ascending and descending branches of the voltammogram can be both caused by prior cathodic polarization and spontaneously generated under unpolarized conditions. This indicated the existence of a quasi-equilibrium in the chemical state of the coating material, which could be perturbed by the external bipolar polarization. The characteristic relaxation time for this system was found to be 40–370 ms. The quasi-equilibrium was attributed to a reversible hydration/dehydration reaction taking place in the active zone of anodic alumina layer (degree of hydration: 10–40%). Coating response analysis via kinetic hydration model allowed both explanations to be provided to a number of previous experimental observations and practical recommendations to be made for the design of efficient electrical regimes for intelligent PEO processes. The latter includes recommendations on avoiding long pauses during negative to positive switching.

Effect of anodizing temperature and organic acid addition on the structure and corrosion resistance of anodic aluminum oxide films

Anodic aluminum oxide films, industrially produced by anodizing aluminum alloys under the galvanostatic mode at a relatively low temperature of 20°C (electrolyte bath temperature), present the reliable anticorrosive effect for numerous applications. For fabricating anodic aluminum oxide films with the promising corrosion resistance as well as high growth rate in a wide temperature range, the effect of anodizing temperatures on the structure and growth mechanism of anodic aluminum oxide films was investigated. As the temperature increases up to 30°C, the stress-driven breakdown of porous-type anodic aluminum oxide layers induced by their thinner pore walls was estimated. This phenomenon is interpreted by an increase of electronic current and thus a strong scour effect of O2 bubbles on the porous-type anodic aluminum oxide layers. Moreover, with the addition of composite organic acid into the sulfuric acid-based electrolyte solution, the anions (C6H5O73−,C4H4O62−) that incorporated into the anodic oxide contribute to lowering the electronic current and thus suppressing the formation of oxygen bubbles, resulting in a thicker barrier-type anodic aluminum oxide layer. This is assumed to be responsible for the enhanced corrosion resistance of anodic aluminum oxide films prepared at 30°C with 50 g/L organic acid addition.

Evaluation of the electrochemical corrosion behavior of anodic aluminum oxide produced by the two-step anodization process

Purpose This study aims to investigate the effect of different pore diameter and pore length on corrosion properties of anodic aluminum oxide (AAO) film. Design/methodology/approach AAO layer was produced by two-step anodization aluminum in oxalic acid. The surface morphology was investigated using field emission scanning electron microscopy. The pore diameters were ranging from 25 ± 5 to 65 ± 5 nm and the pore length ranging from 5 to 17 µm. The corrosion properties of the AAO films was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy tests. Corrosion properties and morphology of the anodic films depending on anodization times and pore expansion times were evaluated. Findings All highlights of this work can be summarized with the following specified below: more treatment with the protective barrier layer of the solution as the pore diameter increases depends on the morphology of the nanotube structured AAO layer. The excellent corrosion resistance renders AAO films without pore expansion very promising. The oxide layer thickness does not affect the corrosion resistance. The better corrosion resistance of AAO films at low pore length can be ascribed to the barrier layer thickness and the more homogeneous structure. The presence of defects for the higher pore length decreases its corrosion resistance. Originality/value The AAO films were fabricated by a two-step anodization method in oxalic acid. The anodization times and pore expansion times affect the corrosion performance. The AAO film without pore expansion has good corrosion resistance. The corrosion resistance decreases as the pore length increases.

Hot-injection for synthesizing ammonium thiosulfate precursor of molybdenum disulfide thin film coated on nano-porous aluminum oxide for surface strengthening

A cheap and massive producible ammonium thiosulfate precursor has been synthesized by hot-injection method for coating MoS2 layer onto the nano-porous anodic aluminum oxide (AAO) layer on the surface of 7003 alloy. The ammonium thiosulfate precursor is pyrolyzed at 280, 375, 400 and 550 °C to form the MoS2 layer, respectively. After 1440 m wear test, the wear rates (weight loss/original weight) of pure 7003 alloy, anodized 7003 alloy and MoS2 coated 7003 alloy pyrolyzed at 400 °C are 0.339%, 0.017%, and 0.0109%, respectively. The thickness of the molybdenum disulfide film observed by transmission electron microscope is about 43.3 nm. The surface hardness of MoS2 coated 7003 alloy is about 5–6 GPa higher than that of AAO, 3–4 GPa measured by nanoindentation. The maximum reduced modulus of elasticity is about 90 GPa as the pyrolytic temperature reaches 400 °C. The ratio of the average surface hardness (H∗) and reduced modulus of elasticity (E∗) is linearly proportional to the elastic recovery rates (We), calculated from the maximum indentation depths with different pyrolytic temperatures. The elastic recovery rate would remain in a range of the pyrolytic temperatures between the occurrence of solid solutionization and completion of the solid solution homogenization for Al–Mo alloy formation.

Evaluation of the electrochemical performance of Ag containing AAO layers after extended exposure to a model corrosive medium

The coating procedure appears to be an indispensable finishing stage in the production of Al based industrial products, engineering facilities and equipment. For this reason, there is an ever-increasing interest towards the elaboration of reliable corrosion protective layers with apparent coverage, adhesion, and barrier properties. In this sense, both the for­ma­ti­on of anodized aluminum oxide (AAO) layer and its further modification with silver enable the elaboration of advanced (Al-O-Ag) films with extended beneficial charac­te­ris­tics. The present research activities are aimed at the determination of the corrosion pro­tective properties of electrochemically synthesized Al-O-Ag layers on the technically pure AA1050 alloy. The structures and compositions of the obtained Al-O-Ag layers were characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The research activities were accomplished by means of two independent electrochemical characteri­za­tion methods: electrochemical impedance spectroscopy (EIS) and potentio­dynamic scan­ning (PDS). The electrochemical measurements were performed after 24, 168 and 672 hours of exposure to 3.5 % NaCl solution used as a model corrosive medium (MCM), in order to determine the barrier properties and durability of the elaborated Al-O-Ag layers. The analysis of the obtained results has undoubtedly shown that the proposed electro­chemical Al-O-Ag layer formation can successfully be used for the creation of self-standing layers with apparent corrosion protective properties. Besides, Al-O-Ag system can be used as a basis for development of efficient protective layers suitable for application in biologically contami­nated media.

Synthesis and photoluminescence properties of nanoporous anodic aluminum oxide (NAAO): Sm3+ nanocomposite layer: Effect of anodizing parameters (time and voltage), Sm3+ concentrations, and annealing temperatures

In the present work, nanoporous anodic aluminum oxide (NAAO) layers were synthesized by mild and mild-hard anodization methods in a solution of oxalic acid and photoluminescence properties of these oxide layers were compared. Then, the nanoporous anodic aluminum oxide: Sm3+ (NAAO: Sm3+) nanocomposite layer is produced by boiling the NAAO layers in a solution of samarium nitrate and annealing at different temperatures under argon atmosphere. Moreover, effect of anodizing parameters (time and voltage), Sm3+ concentrations, and annealing temperatures on photoluminescence properties of the NAAO: Sm3+ nanocomposite layers were investigated and results indicate composition of SmAlO3. Finally, morphology, phase structure, energy levels, and emission wavelengths of the oxide layers were investigated by field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), and photoluminescence (PL) spectroscopy. Results indicate that the PL intensity of the NAAO layers produced by mild-hard anodization is more than the mild anodization. Moreover, the layers produced at 120 V for 2 h have the most PL intensity. At 1200 °C temperature, 0.7 M concentration of samarium ions the most PL intensity is created. Moreover, with the excitation of the NAAO: Sm3+ nanocomposite layer created at 400 nm wavelength, three main emission bands from the 4f-4f intra-configuration transitions from Sm3+ ions are clearly observed. These transitions include 4G5/2 → 6H5/2, 4G5 2 → 6H7/2, and 4G5/2 → 6H9/2.

The Role of Anodization in Naturally Cooled Heat Sinks for Power Electronic Devices

Abstract Effect of anodization on the thermal performance of naturally cooled heat sinks in power electronic devices made of die-cast aluminum alloy A380 and machined aluminum alloy 6061 was investigated experimentally and numerically. Various types of anodization were examined with different thickness of anodic aluminum oxide layer (AAO), pore size distributions, and surface coloring conditions. A customized natural convection and thermal radiation experimental chamber was built to measure the cooling capacity and heat sink temperatures. A 3D numerical model was also developed and validated against the collected data to provide more details into the contribution of the radiation heat transfer. The total emittance of the anodized samples was determined by a Fourier transform infrared reflectometer (FTIR) spectroscopy method. The results show a significant improvement in total hemispherical emissivity from 0.14 to 0.92 in anodized die-cast aluminum samples. This increase resulted in a considerable reduction in overall thermal resistance, up to 15%; where up to 41% of the total heat dissipation was contributed by thermal radiation. In spite of the rather distinguishable surface morphologies, the measurements suggested that thermal emissivity of the anodized die-cast Al A380 and Al alloy 6061 samples were in the same range.