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A molecular cooling fan (MF) is a nanocomposite coating technology, where the quantized lattice motions in nanomaterials are assembled to absorb heat from the heat source, promote to higher vibration states, and emit excess energy by radiation. Using a factorial design technique, seven factors were investigated to optimize MF cooling performance and efficiency. The results show that a MF coating prepared with 8 nm sized multiwalled carbon nanotubes can cool down 4 °C lower than that assembled with 50–80 nm due to higher activity of lattice motions. The MF makes equilibrium temperature cool down by 10 and 20 °C at input operation voltages of 35 and 55 V on the same heat dissipation unit (HDU). Using the optimal factors, a MF coating was applied on commercial HDUs. The results demonstrated that molecular fan action can reduce the size and mass of the heat-sink module, offering a low cost LED light unit.

Nanodiamond powder (NDP), multiwall carbon nanotube (MWCNT), and carbon black (CB) were dispersed in an acrylate (AC) emulsion to form composite materials. These materials were coated on aluminum panels (alloy 3003) to give thin coatings. The active phonons of the nanomaterials were designed to act as a cooling fan, termed "molecular fan (MF)". The order of lattice quantization, as investigated by Raman spectroscopy, is MWCNT > CB >> NDP. The enhanced surface emissivity of the MF coating (as observed by IR imaging) is well-correlated to lattice quantization, resulting in a better cooling performance by the MWCNT-AC composite. MF coatings with different concentrations (0%, 0.4%, 0.7%, and 1%) of MWCNT were prepared. The equilibrium temperature lowering of the coated panel was observed with an increase in the loading of CNTs and was measured as 17 degrees C for 1% loading of MWCNT. This was attributed to an increased density of active phonons in the MF coating.

Two algorithms—peak picking and peaks correlation—have been compiled in a portable laser-induced breakdown spectroscopy (LIBS) system and used specifically for spectral fingerprinting of paints and coatings, which contain multiple ingredients and require several application steps. The LIBS technique starts with a laser shot on the specimen surface, detection of the emission of the elements present, and analysis of the sample compositions. The LIBS system has been successfully illustrated for the identification and analysis of coating substrates, surface pretreatments, and primer and topcoat paints obtained in the lab and at field sites. The results indicate that, despite the compositional complexity in organic metal finishing, the spectral fingerprint of paints and coatings can be effectively determined by the LIBS technique. The advantages of LIBS technique over other conventional methods, such as EDX, are that it is quasi-nondestructive (

Six different phosphorus-containing reagents were used as self-phosphating agents and acid catalysts in the formulation of a polyester−melamine coating. The phosphorus compounds chosen for the study were Cycat 4040 (4040), Cycat 296-9 (296), Albright & Wilson PA-75 (PA-75), phosphonosuccinic acid (PPSA), and two in situ phosphatizing reagents (ISPR-1 and ISPR-2, phenylphosphonic acid and fosfosal, respectively). Each individual phosphorus-containing compound was evaluated separately using a varying percentage of agent in the paint formulation. The different paints made using the different modifiers were applied to bare 3003 or 3105 aluminum panels. After the individual phosphorus-containing reagents were optimized, the optimized additives were compared to each other utilizing electrochemical impedance spectroscopy (EIS), differential scanning calorimetry (DSC), saltwater immersion, and pencil hardness tests. The most commonly used acid catalyst (4040) did not perform as well as the other acid catalysts. U...

A pigmentless polyester−melamine coating catalyzed with p-toluenesulfonic acid (p-TSA) shows high impedance (∼1010 Ω·cm2) at low frequency (0.1 Hz). After the addition of pigment and additives, the impedance drops to ∼105 Ω·cm2. However, using an in situ phosphatizing reagent (ISPR) for the dual purpose of catalyzing the polyester−melamine cross-linking reaction and phosphatizing the metal surface does not show this detrimental lowering of the impedance at low frequency. Results of electrochemical impedance spectroscopy measurements and the corresponding electrical equivalent circuits show that the in situ phosphatizing coating (ISPC) applied to both bare and pretreated steel panels provides superior corrosion protection. At low frequency, the panels coated with the ISPC show 1000 times the resistance of the bare and pretreated steel panels coated with the p-TSA-catalyzed polyester−melamine paint. The simultaneous chemical process of the ISPR catalyzing desirable cross-linking reactions and forming the su...

Surface pretreatment, such as chromate conversion, is generally required for the organic coating on Ti-6Al-4V titanium alloys. The surface modification process facilitates bond formation between the titanium surface and adhesives or paints. However, the hexavalent chromate used in the conversion coating is carcinogenic and must be eliminated. Recently, the “green chemistry” technique of in-situ phosphatizing coatings (ISPC) has been developed at Northern Illinois University. In this study, a polyester-melamine coating system catalyzed by p-toluene sulfonic acid is used as a control paint and applied to bare (paint 1) and chromated (paint 3) Ti alloy panels. The arylphosphonic acid employed as an in-situ phosphatizing reagent (ISPR) is used to formulate ISPC polyester-melamine paint and to react in-situ with the metal surface when ISPC paint is applied on bare Ti panels (paint 2) and chromated Ti panels (paint 4). After soaking in 3% NaCl solution for 1500 hr, the electrochemical impedance, |Z|, was measured as 109, 1010, 1010, and 1010 ohm-cm2 for paints, 1, 2, 3, and 4, respectively. After 1000 hr salt spray (fog) testing, a disbondment from the “X” scribe is observed as 13 and

The current organic coating on metals for aerospace applications involves a multi-step process and considerable energy, labor and control, and it generates toxic wastes such as chlorinated solvents, cyanide, cadmium, lead and carcinogenic chromates. The green chemistry technology of in situ phosphatizing coatings (ISPCs) developed in our laboratory is a one-step self-phosphating process, in which the deposition of metal phosphate layer on the substrate surface and the curing of polymer paint film take place independently, but simultaneously. The formation of a metal phosphate layer in situ will essentially eliminate the metal surface pre-treatment step of employing a phosphating line/bath. The use of chemical bonds linked to the paint polymers to seal the pores of metal phosphate in situ should enhance coating adhesion and suppress metal corrosion without a post-treatment of final rinses containing chromium (Cr 6+ ). The successful applications of ISPCs in three types of commercial paints (solvent-borne high-solids, water-reducible and VOC-free latex) on bare and pre-treated cold-rolled steel and 2024 aluminum coupons is presented. The protective performance (coating adhesion and corrosion inhibition) of ISPCs is shown to be superior over that of the current multi-step coating practice.

Toxic chemicals, such as chrome, are commonly used in the application of conversion coatings to various metal surfaces. In situ phosphatizing coatings (ISPCs) are an innovative approach for eliminating the requirement of a conversion coating which ends the need of toxic materials used in a multi-step coating practice. An ISPC is formulated by predispersing an in situ phosphatizing reagent (ISPR) into a paint system. In this study, an ISPR, an arylphosphonic acid, is used in a polyester–melamine paint to react in situ with the metal surface and to provide the acidic catalyst needed, while thermally curing the paint. A second polyester–melamine paint system is used as the control that uses the standard catalyst para-toluenesulfonic acid (p-TSA) to catalyze the cross-linking reaction in the paint. These two paint systems are applied to bare 2024 T3 Al panels and to chromated 2024 T3 Al panels. The coated panels are treated in a corroding media for 2,400 h and monitored periodically using electrochemical impedance spectroscopy (EIS). Results of EIS data and the corresponding electrical equivalent circuit (EEC) show that the ISPC applied to both the chromated and untreated Al panels provide superior corrosion protection. At low frequency (0.01 Hz), the panels coated with the ISPC show 10 000 times more resistance than both the chromated and bare Al panels coated with the control polyester–melamine paint. The corresponding EEC shows that the panels with the control paint applied have double the amount of electrical components (resistors and constant phase elements). A physical interpretation is suggested for the EEC. The paint adhesion to the Al surface and the corrosion behavior are tested by salt-water immersion and salt fog. After the panels are exposed to the salt solution, a pressure tape is applied to test the adhesion. The results show that the ISPC applied on the chromated Al adheres the best. The simultaneous reaction of the ISPR catalyzing the curing of the paint and forming the metal–phosphate layer is the reason for the superior paint performance.

The coating behavior of a polyester−melamine paint catalyzed by an in situ phosphatizing reagent (ISPR) was investigated, and the results were compared to p-toluenesulfonic acid- (p-TSA-) catalyzed paints. Fourier transform infrared spectroscopy was used to ascertain that the reaction between the ISPR and the Al surface takes place. Differential scanning calorimetry was used to measure the glass-transition temperature (Tg) and the Tg thus providing an indication that the ISPR catalyzed the paint film formation. The deterioration of the coatings by overbaking was studied using thermogravimetric analysis. The corrosion resistance of the coatings on aluminum coupons was examined using electrochemical impedance spectroscopy. Equivalent electrical circuits were utilized to give numerical values to the resistors and capacitors in the coated panel. The paint film adhesion was tested by saltwater immersion. The high-quality performance of the ISPR-catalyzed paint can be attributed to the simultaneous reactions of...

We report the successful formulation of stable and compatible in-situ phosphatizing coatings (ISPCs) for a waterborne alkyd-amino baking enamel applied on bare cold-rolled steel (CRS), iron phosphated Bonderite 1000 (BD), and iron phosphated plus Parcolene 60 chromated (BD+P60) coupons. The enhanced coating adhesion of water-based ISPCs is confirmed by the cathodic delamination measurements. After 100 hr of salt spray (fog) test, the corrosion resistance performance (measured by the corrosion disbondment across the “X” scribe, d in mm) of the water-based ISPC on CRS panel (d=4.0−7.0 mm) outperformed that of the control alkyd paint on B-1000 (d=26 mm) and also on BD+P60 (d=14 mm) coupons. The superior coating performance of water-based ISPCs is believed to result from the in-situ metal surface phosphatization as detected by the reflectance FTIR technique.

A single step in-situ phosphatizing coating (ISPC) can be formulated by pre-dispersing an optimal amount of in-situ phosphatizing reagents (ISPRs) into the paint system. The technique of ISPC is applied to a high-solids polyester-malemine baking enamel using a designed “ISPR-2.” The in-can stability of ISPC is verified using rheological measurements. The coating properties and protective performance of the ISPC are compared to those of the multi-step coating of control sample (MCCS). The immersion tests in a 3% NaCl solution and salt spray testings show a significant improvement in paint disbondment from the “X” scribe for ISPC. The observed coating performance enhancement of ISPC over MCCS is confirmed from the multi-functionality of ISPRs. Phosphate chemistry proceeds via an acid-base type of interaction, P-O−- Mn+, and polymer chemistry generates a covalent P-O-C linkage with the polymer network.

A novel in-situ phosphating coating system is developed by predispersing an optimum amount of phosphatizing reagents into the paint formulation. Five possible in-situ phosphatizing reagents are used in the formulation of a model solvent-borne polyester-melamine enamel paint system. The new formulation is then coated and cured on a cold-rolled steel surface. The chemical reactivity of phosphatizing reagents are studied via different analytical techniques. The results can be summarized as follows: (i) the phosphatizing reagents, being dispersed into the solvent-borne paints to form a stable self-phosphating organic coating, perform a successful in-situ phosphatization of the metal substrate; (ii) there is an observable lowering of Tg for the paint films, due to the acceleration of melamine self-condensation by the acidic nature of phosphatizing reagents, which can be corrected by optimizing the coating formulation; (iii) the organic phosphatizing reagents, which are more dispersable in a solvent-borne coating system, are very effective yet have less influence on the cross-linking density of the final film, thus giving a coating with higher AC impedance and providing a better corrosion protective performance.

Molecular fan, a radiative cooling by thin film, has been developed and its application for compact electronic devices has been evaluated. The enhanced surface emissivity and heat dissipation efficiency of the molecular fan coating are shown to correlate with the quantization of lattice modes in active nanomaterials. The highly quantized G and 2D bands in graphene are achieved by our dispersion technique, and then incorporated in an organic-inorganic acrylate emulsion to form a coating assembly on heat sinks (for LED and CPU). This water-based dielectric layer coating has been formulated and applied on metal core printed circuit boards. The heat dissipation efficiency and breakdown voltage are evaluated by a temperature-monitoring system and a high-voltage breakdown tester. The molecular fan coating on heat dissipation units is able to decrease the equilibrium junction temperature by 29.1 ° C, while functioning as a dielectric layer with a high breakdown voltage (>5 kV). The heat dissipation performance of the molecular fan coating applied on LED devices shows that the coated 50 W LED gives an enhanced cooling of 20% at constant light brightness. The schematics of monolayer graphene dispersion, undispersed graphene platelet, and continuous graphene sheet are illustrated and discussed to explain the mechanisms of radiative cooling, radiative/non-radiative, and non-radiative heat re-accumulation.

A one-pack paint composition comprising polyester-melamine enamels and a predispersed amount of either phosphoric acid (H 3 PO 4 , in situ phosphatizing reagent), p-toluenesulfonic acid (p-TSA, polymer catalyst), or hydrofluoric acid (HF, surface etching agent) was formulated, coated, and thermally cured on a cold-rolled steel panel. The chemical natures of coating surface/interface were investigated by SEM-EDS and FTIR techniques, and the coating performance was verified by EIS measurements. The formation of metal phosphate layer and covalent bonding of P-O-C linkage at the coating/substrate interface was evident only for the unicoat system formulated with H 3 PO 4

The nature of chemical mechanisms, bondings, and structures in a single-step polyestermelamine enamel/H 3 PO 4 systems, in particular, at the interface of polymer/phosphate/steel, was investigated by using ac impedance analysis and 80 o grazing angle reflectance Fourier transform infrared spectroscopy. An in-situ phosphatizing coating on «Q» panel was illustrated and show to behave like a pure capacitance. The «simultaneous» chemical reaction of H 3 PO 4 wth «Q» panel surface and polymer resin was evidenced to produce a corrosion protective barrier by the foration of interfacial layer of crystalline ion phosphate and to enhance coating adhesion by the covalent bondings of P-O-C linkage.