Polished Aluminum Research Articles

Effects of Substrates on Properties of Tin Oxide Gas Sensors

SnO2 thin films on three different kinds of substrates (sapphire, alumina, and Si with 1000 Å-thin oxide layer) were grown by a reactive r.f. magnetron sputter method. Epitaxial SnO2 thin film without an apparent grain structure but with high dislocation density along lateral direction to substrate was grown on a sapphire substrate. The microstructure of the thin film was investigated, using the 3C2 beam line from a Pohang Light Source (PLS) consisting of a 2-GeV electron accelerator, 4 circle X-ray diffractometer, and AFM. It was confirmed that the thin film grew epitaxially on the sapphire substrate with variants structure. A large defect density was exhibited on the surface of the epitaxial thin film, which is related to sorption sites reacted with the gas. SnO2 films on the polished alumina and Si substrate showed poly-crystalline structure of tetragonal structure, low resistance of about 10 Ω, and good optical transmittance. An epitaxial SnO2 thin film exhibited the highest sensitivity to combustible gases and a particular sensitivity of 95% to alcohol at 2000 ppm and 350°C. The sensor also showed a good stability with small baseline drift and short reaction times of about 5 seconds, respectively. This experiment confirms substrate effects on characteristics of an SnO2 thin film plus the potential for the application of epitaxial SnO2 film in the production of stable gas sensors.

Surface mechanical analyses by Hertzian indentation

Hertzian indentation technique was used to measure surface flaw sizes on polished dense polycrystalline alumina specimens with grain sizes G = 1.2, 3.8 and 14.1 µm. Two surfaces finishes were studied: well-polished (Syton) and coarse-polished (45 µm diamond paste). Flaw sizes depended on the surface finish and increased with increasing grain size. Fracture toughness (K Ic) for each material (relating to the propagation of flaws of a few µm depth) was determined from the minimum fracture load in a series of Hertzian tests. K Ic values were 3.58, 3.45 and 2.96 MPam½ for G=1.2, 3.8 and 14.1 µm, respectively. Fracture toughness values were also determined by Vickers indentation over a range of loads; the K Ic values determined from the Hertzian tests were consistent with the trends in K Ic with crack size from the Vickers indentation tests.

Fatigue of deep rolled AlMg4.5Mn (AA5083) in the temperature range 20–300°C

Abstract The cyclic deformation behavior of deep rolled and polished aluminium wrought alloy AlMg4.5Mn has been investigated in the temperature range from 20 to 300 °C. Results of quasistatic tension and compression tests of untreated specimens are presented. To characterize the fatigue behavior for stress-controlled tests as a function of test temperature, stress-life-curves, cyclic deformations curves and mean strains as a function of number of cycles are given. Residual stresses and work hardening effects near the surface of the deep rolled condition before and after fatigue tests were investigated by X-ray diffraction methods.

Covalent Bonding of Organic Molecules to Cu and Al Alloy 2024 T3 Surfaces via Diazonium Ion Reduction

Cu surfaces and polished aluminum alloy 2024 T3 substrates were derivatized at open-circuit potential with aryl diazonium salts in both aprotic and aqueous media. Raman spectroscopy confirmed the presence of a derivatized film on the substrates before and after exposure to boiling water and sonication in acetone. Two different Cu substrate surfaces were prepared and used for X-ray photoelectron spectroscopy (XPS) analysis of the derivatization results. One surface was native oxide Cu, predominantly in the form of and one surface was predominantly Results of the XPS analysis indicate the presence of both a Cu-O-C linkage and a Cu-C covalent bond between the aryl ring and the Cu substrate, and a high coverage of the organic layer. XPS results also indicate the formation multilayers on both types of Cu surfaces with different percentages of azo coupling within the multilayers on the two surfaces. Applications of a covalently bonded organic film on copper and alloy surfaces include adhesion promotion, corrosion protection, and possibly inhibition of oxygen reduction. © 2004 The Electrochemical Society. All rights reserved.

Ab-initio Structural Properties and Stress-Deformation Analysis by Rheological Modeling of Diamonds-containing Nanocarbon nanotubes

AbstractIn our laboratory, we developed a simple method for measuring the mechanical properties of single nanotubes and modeling its mechanical properties by rheological analysis. The technique involves depositing nanotubes from a suspension in a suitable liquid onto well- polished alumina ultrafiltration membranes with a pore size of about 200 nm. Rheological models of the composite systems have been proposed and confirmed by in-situ experiments at AFM indentation.

The influence of particle charge and roughness on particle–substrate adhesion

In the electrophotographic process, charged toner particles are transferred from the bulk to the photoreceptor drum and from there to the paper. In high performance printing systems, more than 1000 pages/min are printed, equivalent to the transfer of more than 10 10 particles/min. The key to understand and to improve the printing system is particle–particle and particle–substrate interactions, respectively. We study the adhesion forces by means of atomic force microscopy (AFM) measurements complemented by centrifugal detachment measurements in an ultracentrifuge. The interpretation of AFM measurements requires careful calibration of the used cantilevers together with a sound statistical analysis. Particle charges have been determined from force–displacement curves. Silicon wafers, polished and PVD-coated aluminum substrates with tailored roughness are chosen as model materials. Spherical, smooth polystyrene and specially prepared alumina particles as well as rugged toner particles of irregular shape are investigated. We proceed from well-defined model systems (flat smooth substrate interacting with spherical particles) to technical systems where rugged particles adhere to rough substrates. The adhesion forces consist of electrostatic and of non-electrostatic (e.g. van der Waals forces) components. We show how the influence of electrostatic forces relative to the van der Waals forces can be controlled.

Effects of Substrate on the Characteristics of SnO2 Thin Film Gas Sensors

Effects of substrate materials on the microstructure and the sensitivity of <TEX>$SnO_2$</TEX>thin film gas sensors have been studied. Various substrates were studied, such as oxidized silicon, sapphire, polished alumina, and unpolished alumina. It was observed that strong correlation exists between the electrical resistance and the CO gas sensitivity of the manufactured sensors and the surface roughness of <TEX>$SnO_2$</TEX>thin films, which in turn was related to the surface roughness of the original substrates. X<TEX>$SnO_2$</TEX>thin film gas sensor on unpolished alumina with the highest surface roughness showed the highest initial resistance and CO gas sensitivity. The transmission electron microscopy observation indicated that shape and size of the columnar microstructure of the thin films were not critically affected by the type of substrates.

Study on the optoelectronic properties of amorphous selenium-based xerographic photoreceptors for electrophotography

Amorphous selenium-based material could be used as the photoreceptor of a photocopy machine. For much more understanding of amorphous selenium (a-Se) photoreceptor, the aluminum oxide (Al 2O 3) and amorphous tungsten trioxide (a-WO 3) were deposited onto polished aluminum substrates as the blocking layers using the thermal oxidation and vacuum sputtering systems, respectively. Next, we used a vacuum evaporation method for preparing the amorphous selenium film in order to complete the Al/Al 2O 3/a-Se and Al/a-WO 3/a-Se photoreceptors. The optoelectronic properties of the samples were measured and compared. We produced photoinduced discharge curves (PIDC) using electrostatic paper analyzer, and the initial surface potential ( V so), dark decay time ( t d), photosensitivity ( E 1/2) and residual potential ( V r) could be obtained. We can find that Al/a-WO 3/a-Se photoreceptor has excellent optoelectronic properties. Furthermore, we also compared different blocking layers and isothermal annealing effects for the photoreceptors.

Ablative generation of surface acoustic waves in aluminum using ultraviolet laser pulses

Surface acoustic wave generation using ablative excitation with ultraviolet laser pulses is studied experimentally in order to quantify the magnitude of response. The acoustic waves are interferometrically measured on the surface of polished aluminum samples at distances of 5–40 mm from the excitation spot. Amplitudes of the surface acoustic waves are measured as a function of laser energy (1–60 mJ) and distance from the excitation spot yielding peak-to-peak displacements of 1–40 nm. The results are compared to theoretical calculations using the Green’s function for a step impulse response. The impulse required to match the measured results is compared to the expected impulse based on plasma pressure scaling in the ablative regime and the experimentally measured response is found to agree within a factor of 2 with the theoretical predicted impulse.

Friction velocity and power law velocity profile in smooth and rough shallow open channel flows

This paper examines the mean velocity profiles in shallow, turbulent open channel flows. Velocity measurements were carried out in flows over smooth and rough beds using a laser-Doppler anemometer. One set of profiles, composed of 29 velocity distributions, was obtained in flows over a polished smooth aluminum plate. Three sets of profiles were obtained in flows over rough surfaces. The rough surfaces were formed by two sizes of sand grains and a wire mesh. The flow conditions over the rough surface are in the transitional roughness state. The measurements were obtained along the centerline of the flume at three different Froude numbers (Fr ~ 0.3, 0.8, 1.0). The lowest Froude number was selected to obtain data in the range of most other open channel testing programs and to represent a low subcritical Froude number. For each surface, the Reynolds number based on the boundary layer momentum thickness was varied from about 600 to 3000. In view of the recent questions concerning the applicability of the log-law and the debate regarding log-law versus power law, the turbulent inner region of the boundary layer is inspected. The fit of one type of power law for shallow flows over a smooth surface is considered. The appropriateness of extending this law to flows over rough surfaces is also examined. Alternate methods for determining the friction velocity of flows over smooth and rough surfaces are considered and compared with standard methods currently in use.Key words: power law, open channel flow, velocity profile, surface roughness.

Thermal shock of ground and polished alumina and Al2O3/SiC nanocomposites

Abstract The thermal shock behaviour of sintered alumina and alumina/SiC nanocomposites with 1, 2.5 and 5 vol.% SiC was studied. The thermal shock testing was carried out by means of quenching into water from high temperatures (ΔT in the range 0–750 °C). Both single shocks and repeated shocks were used. The damage introduced by thermal shock was characterised by degradation of strength in four-point bending and by changes in Young's modulus. The effects of the surface finish of the test specimens (either ground or highly polished surfaces) on the thermal shock resistance were also studied. In both alumina and nanocomposite materials, specimens with ground surfaces showed a better resistance to thermal shocks than specimens with polished surfaces. However, the resistance of the nanocomposite material to single and repeated thermal shocks was no better than that of the pure alumina.

Temperature limit values for gripping cold surfaces.

At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. Four hundred and fourteen experiments were run where male and female subjects were invited to grip for up to 20 min cold bars of different contact coefficients, i.e. polished wood, nylon, stone, steel and aluminium. The air temperature and the bars' initial surface temperatures ranged between 0 and -30 degrees C for the various experiments. While gripping the bars, either only the hand or the whole body was exposed to cold. The data were used to develop a prediction formula and a graph of the surface temperature limit values in order for the skin contact temperature not to reach <15 degrees C. This duration is shown to offer a significant degree of safety with respect to the minimal surface temperature spontaneously tolerated by the subjects. Experiments and modelling must be pursued to extend these data to other conditions of exposure.

The Removal Selectivity of Titanium and Aluminum in Chemical Mechanical Planarization

The removal selectivity control of aluminum and titanium metal barrier during aluminum chemical mechanical polishing in the Damascene process is known to be critical for surface planarity without metal dishing and dielectric erosion. Unfortunately, the electrochemical behaviors of aluminum and titanium are dissimilar, as one may expect. In this study, in situ electrochemical impedance spectroscopy was carried out to investigate the influences of concentration, slurry pH, and metal oxide formation through the passivation on aluminum and titanium. As concentration increases, the measured impedance of aluminum and titanium decreases, or the oxidation rates of these two metals are enhanced upon increasing the oxidizer concentration. As the slurry pH increases, the removal rate of polished titanium increases, but it decreases for polished aluminum. The removal rate of titanium was limited to its oxidation rate and aluminum was limited to its oxide dissolution rate. © 2002 The Electrochemical Society. All rights reserved.

2819 ELID 研削による加工面改質の検討(第一報)

A new electrical grinding method (Electrolytic In-Process Dressing Grinding) for the fabrication of machined surfaces with desirable characteristics for biomaterials and other engineering applications is presented. Conventional biomaterials, such as stainless steel and titanium alloy, require enhanced chemical stability and wear resistance, which are dependent on the quality of the surface oxide layer. However, it is difficult to produce sufficiently homogenous oxide layers by alumina polish finishing alone. The electrical grinding method proposed in this study, in which electric current is applied to the grinding fluid in the machining process, improves oxide formation on the finished surfaces, thereby realizing finished surfaces with extremely thick and stable oxide layers. Compared with alumina polishing, electrical grinding yields machined surfaces having excellent corrosion resistance.

Improvement of Corrosion Resistance in Metallic Biomaterials using a New Electrical Grinding Technique

A new electrical grinding method for the fabrication of machined surfaces with desirable characteristics for biomaterials and other engineering applications is presented. Conventional biomaterials, such as stainless steel and titanium alloy, require enhanced chemical stability and wear resistance, which are dependent on the quality of the surface oxide layer. However, it is difficult to produce sufficiently homogenous oxide layers by alumina polish finishing alone. The electrical grinding method proposed in this study, in which electric current is applied to the grinding fluid in the machining process, improves oxide formation on the finished surfaces, thereby realizing finished surfaces with extremely thick and stable oxide layers. Compared with alumina polishing, electrical grinding yields machined surfaces having excellent corrosion resistance.

Direct observation and characterisation of the oxide nanostructured interface resulting from organosilane pre-treatment of aluminium

ABSTRACTThe pre-treatment of aluminium surfaces prior to adhesive bonding and coating processes is of major technological significance. However, the two major commercial pre-treatments, chromic acid and phosphoric acid anodising, both make use of Cr(VI) containing solutions with the attendant problems of waste disposal. The disposal of this harmful solution poses severe environmental problems. Therefore, other environmentally friendly alternatives are being investigated, one of the most popular candidates is the use of one-step pretreatment processes based on organosilane adhesion promoters.This study examines a model system made from polished aluminium sheet treated with an organosilane; γ-glcidoxypropyltrimethoxysilane (GPS). The interface was characterised by TEM carried out on microtomed sections. The information gained from imaging and Electron Energy Loss Spectroscopy (EELS) analysis revealed a layer of oxide, approximately 70 nm thick. Silicon was found to have been incorporated within this oxide layer. Thus it is suggested that during the curing of the GPS, at elevated temperature, growth of aluminium oxide takes place which gives rise to an Al/O/Si phase.

Monitoring Faceting on Ceramic Surfaces

ABSTRACTFaceting is the transformation of a planar surface into two or more surfaces of lower energy. Metal, semiconductor and ceramic surfaces can all undergo faceting. The evolution of facets formed on the m-plane (1010) of alumina has been monitored using atomic-force microscopy (AFM). When heat-treated, the (1010) surface reconstructs into a hill-and-valley morphology. The present study investigates the manner in which facets originally form and grow to cover a surface. A gravity-loaded indenter (load of 25 grams) was used to mark a 25 μm × 25 μm square area on as-received, polished alumina specimens. An initial heat-treatment of 1400°C for 10 minutes is carried out to initiate faceting. With the indents as guides the same area can be identified and imaged after each subsequent heat-treatment. The morphology of the facets can be described as being comprised of a “simple” and “complex” surface. The simple surface corresponds to the (1102) plane which is stable over the course of heat treatments, whereas the complex surface gradually transforms to a lower energy surface after several heat treatments and acts as a nucleation site for new facet growth.

INFLUENCE OF OXYGEN IMPURITIES ON ION BEAM INDUCED INTERDIFFUSION IN THIN Au-Al MULTILAYERS DEPOSITED ON DIFFERENT SUBSTRATES

Au-Al interdiffusion processes in thin layers deposited on various substrates were investigated with RBS during high current ion irradiation. The atomic movements were identified simultaneously (in-situ RBS) with a depth resolution of a few nanometers. It was observed that heating of the specimens due to ion irradiation was the most evident mechanism inducing atom transport. After only 8 min of irradiation with 300 nA 2.0 MeV 4 He + ions (beam spot diameter 0.5 mm), two Au-Al layers (total thickness 600 nm) deposited on glassy carbon or gold were found to be fully interdiffused. In contrast to that, no significant interdiffusion was measured for the same systems deposited on wafer silicon and polished aluminium substrates. To understand this behaviour, depth distributions of oxygen impurities were measured using enhanced elastic backscattering spectroscopy (σ ≈ 102 σ R with 7.6 MeV 4 He ions.

Chemical aspects of wear of alumina ceramics

In our investigation, the effects of the tribochemically-induced dissolution of alumina ceramics and modulation of near-surface forces (surface charge) within the tribocontact were studied. The wear and friction behaviors of alumina were investigated using a reciprocating sliding test in different chemical environments. The samples for the tests were hemispherical pins and plates of polished alumina, both prepared by a near-net-shaping method.The sliding tests were conducted in water-based liquids with different pH values or with the addition of a polyelectrolyte to control the surface charge at solid surfaces. The coefficient of friction was continuously recorded during the tests and the wear-loss was subsequently determined for all samples. The results show a significant effect of the chemical agents on the coefficient of friction as well as on the material-removal rate in different aqueous media. The results are discussed in terms of the chemical and electrochemical properties of the materials in the tribocontact.

A new detection technique for laser-generated Rayleigh wave pulses

A new detection technique is presented to observe Rayleigh wave pulses. The detection principle is discussed in detail. Rayleigh wave pulses were excited on the surface of polished aluminum. Well-defined waveforms were acquired. Furthermore, we observed Lamb wave on the surface of silicon chip. The experiment results show that this kind of detection technique is suitable to observe Rayleigh wave as well as Lamb wave and has a great potential in the field of laser ultrasonic.