Non-metallic Surfaces Research Articles

Development of latent fingermarks by aqueous electrolytes

In this work we present our observations on the interaction between metallic (copper, aluminum, iron, brass, zinc) and non-metallic (glass and plastic) surfaces bearing latent fingermarks and several aqueous electrolytic solutions. Good quality fingermarks could be observed on some of the metallic and even on non-metallic surfaces after such treatment. The influence of factors such as time interval from deposition, pH of the electrolytes, wiping the latent marks prior to processing and the presence of a second metal on the quality and permanence of the developed impressions have been studied. As a rule, sebaceous marks provided much better quality impressions on all the surfaces. Initial explanations based on electrochemical processes are suggested.

Deposition of metallic coatings on polymer surfaces using cold spray

Current coating technologies such as plasma spray, High Velocity Oxygen Fuel (HVOF) or laser cladding involve the delivery of molten materials during the deposition process. However, such techniques are not well suited to the deposition of metallic coatings on polymers and composites. Cold spray (CS) has attracted much industrial interest over the past two decades. In this method, a material in powder form is accelerated on passage through a converging–diverging nozzle to high speeds via a high pressure coaxial carrier gas jet. The high impact kinetic energy deforms the particles, which creates effective bonding to the substrate.This paper presents the results of an initial study on the potential of the CS process to produce metallic coatings on non-metallic surfaces such as polymers and composites for engineering applications. Experimental and Computational Fluid Dynamics (CFD) results when spraying copper, aluminium and tin powder on a range of substrates such as PC/ABS, polyamide-6, polypropylene, polystyrene and a glass-fibre composite material are presented and analyzed.

An integrated information technology assisted driving system to improve mine trucks-related safety

This paper presents the conceptual model and framework of a novel information technology assisted driving system (ADS) to help improve mine trucks-related safety. The main components of the system include a real-time Google Earth (GE) graphics, GPS, a wireless communication network, a truck driver’s fatigue detection system, and an enhanced visibility display to restore degraded images when operating under severe visibility conditions. Mine trucks are traced and proximity warning is provided using GPS, IP addressable radios for wireless data transmission, and the GE graphic interface. Driver’s fatigue levels are detected and assessed using face tracing, extraction of eye features, and fatigue recognition algorithms. Development of such integrated information technology assisted driving system has a potential to be applied in coal, metal and non-metal surface mining operations.

The kaolinite (0 0 1) polar basal plane

Kaolinite is thought to be an efficient ice nucleating agent because kaolinite crystals expose perfect unreconstructed (0 0 1) basal surfaces which provide a suitable template for ice growth. However, we show here with the aid of density functional theory calculations that the unreconstructed basal surface is polar. Various mechanisms to eliminate the macroscopic dipole and in so-doing stabilize the basal surface are considered. The most promising option identified so far involves the adsorption of foreign atoms (for example, Na and Cl atoms) on the perfect basal surface, since this yields a non-metallic surface with a cleavage energy lower than the unreconstructed polar basal surface. A quantitative experimental structure determination of the kaolinite basal surface is called for.

Membrane photocatalytic destruction of benzothiazoles in an aqueous medium

The paper has described an improved type of a hybrid photocatalytic reactor based on ceramic membrane elements of cardierite and creation on its surface of catalytically active metal-oxide coatings of Ni, Ni-W and Ni-Mo deposited by the method of chemical catalytic metallization of a non-metal surface. For their deposition compositions based on dimethylaminoborane and sodium boronhydride as reducers with preliminary activation in the solutions of salts Sn(II) and Pb(II) were used. Oxidation of the surface was carried out with the simultaneous anodic or chemical leaching of coprecipitated boron. The article has also investigated the impact of membrane separation of components, concentration of an oxidant, disperse catalyst TiO3 in its magnetic liquefaction, time of UV irradiation on the degree of wastewater treatment of one hardly destructible compounds of the benzothiazole class.

Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

AbstractThe interaction of nitrogen, oxygen, and hydrogen plasmas with spin‐coated arrays of colloidal cobalt–platinum particles was investigated with a large variety of microscopic and spectroscopic techniques. It could be demonstrated that the organic ligands of the nanoparticles can be completely removed. Yet, due to the short (∼1.6 nm) interparticle distances within the layers, strong degradation and sintering effects are observed after hydrogen and nitrogen plasma treatments. In the case of oxygen plasma, the shape and size of the individual particles are unaffected and can be preserved, even if a short hydrogen plasma is subsequently applied to reduce the particles back to their metallic state. Nevertheless, the mesoscopic order of the particle arrays is slightly decreased as observed by the breakup of larger ordered areas into smaller domains forming island–trench structures. Probing the surface chemistry of the particles with temperature programmed desorption, a rather complex surface chemistry is found to result from the plasma treatments. The first TPD spectrum after the cleaning process with oxygen and subsequent hydrogen plasmas reveals that the particles are loaded with adsorbed and implanted hydrogen. After removal of this hydrogen, subsequent TPD spectra using CO as a probe molecule, show broad signals between 190 and 360 K pointing to nonmetallic surface properties. While the platinum was found to be completely reduced, XPS measurements reveal a remaining fraction of oxidic cobalt species which are enriched at the surface. Thus, although the structure of the close‐packed Co–Pt nanoparticle arrays can be qualitatively preserved during plasma‐based ligand removal, the treatment leads to a complex materials system the chemical properties of which are influenced by the particle components, the substrate, and the plasma media.

Cluster-surface and cluster-cluster interactions:Ab initiocalculations and modeling of asymptotic van der Waals forces

We present fully ab initio calculations of van der Waals coefficients for two different situations: (i) the interaction between hydrogenated silicon clusters and (ii) the interactions between these nanostructures and a nonmetallic surface (a silicon or a silicon carbide surface). The methods used are very efficient and allow the calculation of systems containing hundreds of atoms. The results obtained are further analyzed and understood with the help of simple models. These models can be of interest for molecular-dynamics simulations of silicon nanostructures on surfaces, where they can give a very fast yet sufficiently accurate determination of the van der Waals interaction at large separations.

High-efficiency adhesive compounds for nonmetallic surfaces

Based on the principles of the formation of adhesion contacts with different (including inert) surfaces, a number of physicochemical procedures for an increase in the strength of adhesive joints is developed. These principles are elaborated at the Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine. Basic models of the structure of adhesive ensuring the maximum value of adhesive strength are proposed. It is shown that synthesized epoxy-urethane oligomers ideally correspond to one of these models. Adhesive compositions are prepared on the basis of synthesized multifunctional oligomers and their physicochemical and adhesion properties are studied. The high efficiency of these adhesives for bonding a wide spectrum of materials including adherends with low surface energy is revealed. The set of the properties of developed adhesive compositions makes it possible to use them in the production of items designed for highly specialized purposes.

Diffraction Effects in the Propagation of Radiation in Polarizable Layers

The very low transmission of light through holes smaller than the wavelength has been found to be enhanced for subwavelength apertures in metallic surfaces with periodic corrugations. This effect has been attributed to the interaction of light with surface plasmons. Similar effects obtained subsequently for non-metallic surfaces have been attributed to evanescent waves on the surface produced by the diffracted Bloch waves from different points in the array. We present an exact solution of Maxwell's equations in the discrete dipole approximation (DDA) for a periodic array of polarizable point dipoles in a layer. Metallic as well as non metallic layers are described. When the wavelength is smaller than the lattice period there is a Bragg's scattered wave, while for subwavelength conditions an evanescent wave on the surface appears. The transmission/reflection coefficients are found to oscillate as a function of frequency, with resonances occurring in a broad range of frequencies depending on the polarizability, at which the evanescent field is enhanced. A detailed study is presented for nanostructured arrays. We find that this model agrees with features observed in experiments through hole arrays supporting the role played by diffraction during light transmission through such arrays without invoking surface plasmons and providing a base to analyze more complex geometries.

Design of planar RFID tag antenna for metallic objects

Proposed is a novel RFID tag antenna consisting of an inner spiral dipole, an outer bent dipole and a double T-matching network that is suitable for attaching to metallic objects. For low-cost fabrication, the antenna is printed on a single-layer substrate without a ground plane or shorting pins. The detailed design parameters of the antenna were optimised using the Pareto genetic algorithm so that the antenna would operate adequately both in free space and on metallic objects. The antenna was fabricated, based on the optimised design, and the performance in free space and on a metallic surface were measured. The half-power matching bandwidth (VSWR<5.8) and the reading range of the antenna in free space were 7.6% and 2.8 m, while on a metallic surface the corresponding values were 0.8% and 1.8 m. For non-metallic surfaces (i.e. low dielectric targets, 2<ɛr<4), the antenna exhibited the reading range of 2–3 m.

Special features of macro- and microrelief formation in nonmetallic flat surfaces in diamond grinding

Based on a physical-statistical model for the formation of grinding debris particles and analysis of their interaction in the contact zone, we describe some special features of macro-and microrelief formation in a flat workpiece surface and in the tool working layer.

Shape Estimation Using Polarization and Shading from Two Views

This paper presents a novel method for 3D surface reconstruction that uses polarization and shading information from two views. The method relies on polarization data acquired using a standard digital camera and a linear polarizer. Fresnel theory is used to process the raw images and to obtain initial estimates of surface normals, assuming that the reflection type is diffuse. Based on this idea, the paper presents two novel contributions to the problem of surface reconstruction. The first is a technique to enhance the surface normal estimates by incorporating shading information into the method. This is done using robust statistics to estimate how the measured pixel brightnesses depend on the surface orientation. This gives an estimate of the object material reflectance function, which is used to refine the estimates of the surface normals. The second contribution is to use the refined estimates to establish correspondence between two views of an object. To do this, a set of patches are extracted from each view and are aligned by minimizing an energy functional based on the surface normal estimates and local topographic properties. The optimum alignment parameters for different patch pairs are then used to establish stereo correspondence. This process results in an unambiguous field of surface normals, which can be integrated to recover the surface depth. Our technique is most suited to smooth, non-metallic surfaces. It complements existing stereo algorithms since it does not require salient surface features to obtain correspondences. An extensive set of experiments, yielding reconstructed objects and reflectance functions, are presented and compared to ground truth.

Design and operation of a double-fiber displacement sensor

Design and operation of a double-fiber sensor for displacement measurements are reported in this study. In this arrangement, one fiber transmits the laser light to the target and the second one receives the light reflected off the target and transmits to a photodetector. Utilizing inexpensive plastic optical fibers offers advantages such as higher reflexability and more robustness at a reasonable cost, which are required for some applications. The novelties of the reported design are compactness of the fiber probe, flexibility, long dynamic range (22 mm), and it is possible to use the source and the detector at the same side. The displacement of the target causes the intensity modulation and such a power variation is the base of sensor operation. Measurements for the metallic and non-metallic surfaces are performed and the results for aluminum, copper, and bronze sheets are presented here. Our results indicate that the sensitivity is highest for the plane mirror (288.8 mV/mm), high for the shiny metallic surfaces (230.6 mV/mm), but it can be used for other surfaces with a reasonable sensitivity. Important parameters of the sensor such as reproducibility (1.0%) and hysteresis effect (1.8%) are also investigated for this device. The theoretical formulation of the sensor operation is also developed and the computed results are compared with the experimental ones. The obtained experimental respond curve agrees well with the theoretical one, which verifies the successful operation of the proposed sensor system for precise displacement measurements.

Reflection of Carbon Dioxide (CO<sub>2</sub>) laser radiation from the theatre surfaces

This work has investigated the power of both specular and diffusely reflected beams of CO2 laser radiation from metallic and non-metallic surfaces of an operating theatre including surgical instruments (specula) and different samples of wall paints in theatre 6 of the Aberdeen Royal Infirmary, U.K. where the CO2 laser radiation is used for surgical treatment. Transmission of the beam through theatre clothing materials as well as relationship between incident and reflected power were also investigated. This study has revealed that linear relationship exists between incident and reflected power and that all metallic surfaces reflect a high proportion of the incident CO2 laser radiation. The surgical instrument (vagina speculum) reflects over 55% of the incident CO2 radiation. Other metallic surfaces (e.g. aluminum) reflect up to 60%. Specular reflectance from non-metallic surfaces was as high as 8% from the theater wall (gloss paint). Each of these values produced very high irradiance (W/cm2) of 11.21, 12.71 and 1.66 for vagina speculum, aluminum surface and theatre wall respectively. All cloth materials tested for transmission absorbed over 97% of the incident radiation. Keywords: Laser radiation, reflection, transmission and irradiance. Nigerian Journal of Physics Vol. 18 (1) 2006: pp. 127-134

Hydrogen analysis in solid samples by utilizing He metastable atoms induced by TEA CO 2 laser plasma in He gas at 1 atm

A TEA CO 2 laser (350 mJ–1.5 J, 10.6 μm, 200 ns, 10 Hz) was focused onto a metal sub-target under He as host gas at 1 atmospheric pressure with a small amount of impurity gas, such as water and ethanol vapors. It was found that the TEA CO 2 laser with the help of the metal sub-target is favorable for generating a strong, large volume helium gas breakdown plasma at 1 atmospheric pressure, in which the helium metastable-excited state was then produced overwhelmingly. While the metal sub-target itself was never ablated. The helium metastable-excited state produced after the strong helium gas breakdown plasma was considered to play an important role in exciting the atoms. This was confirmed by the specific characteristics of the detected Hα emission, namely the strong intensity with low background, narrow spectral width, and the long lifetime. This technique can be used for gas and solid samples analysis. For nonmetal solid analysis, a metal mesh was introduced in front of the nonmetal sample surface to help initiation of the helium gas breakdown plasma. For metal sample, analysis can be carried out by combining the TEA CO 2 laser and an Nd–YAG laser where the Nd–YAG laser is used to ablate the metal sample. The ablated atoms from the metal sample are then sent into the region of helium gas breakdown plasma induced by the TEA CO 2 laser to be excited through the helium metastable-excited state. This technique can be extended to the analysis of other elements, not limited only to hydrogen, such as halogens.

Novel patterning of nano-bioceramics: template-assisted electrohydrodynamic atomization spraying.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.

Interaction of an infrared surface plasmon with an excited molecular vibration

The interaction of an infrared surface plasmon and an excited molecular vibration was investigated by using a square array of subwavelength holes in a Ni film which supports propagating, surface-plasmon-mediated, transmission resonances. The largest transmission resonance [the (1,0)(-)] was tuned through the rocking vibration of the hexadecane molecule (at 721 cm(-1)) in a hexadecane film on the mesh by varying the thickness of the film. The interaction of the rocking vibration and surface plasmon is characterized spectroscopically by an increase in the intensity of the vibrational band by more than a factor of 2, variation of the vibrational line shape relative to the spectrum on a nonmetallic surface, and shifts in vibrational peak position by as much as 3.0 cm(-1). Relationships are developed between the transmission resonance position and the thickness and dielectric properties of the coating.

Temperature Limit Values For Touching Cold Surfaces with the Fingertip

At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfaces. Data were collected in four laboratories with a total of 20 males and 20 females performing a grand total of 1655 exposures. Each touched polished blocks of aluminium, stainless steel, nylon-6 and wood using the distal phalanx of the index finger with a contact force of 1.0, 2.9 and 9.8 N, at surface temperatures from +2 to -40 degrees C for a maximum duration of 120 s. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (TC) of the fingertip was measured over time using a T-type thermocouple. A database obtained from the experiments was collated and analysed to characterize fingertip contact cooling across a range of materials and surface temperatures. The database was subsequently used to develop a predictive model to describe the contact duration required for skin contact temperature to reach the physiological criteria of onset of pain (15 degrees C), onset of numbness (7 degrees C) and onset of frostbite risk (0 degrees C). The data reflect the strong link between the risk of skin damage and the thermal properties of the material touched. For aluminium and steel, skin temperatures of 0 degrees C occurs within 2-6 s at surface temperatures of -15 degrees C. For non-metallic surfaces, onset of numbness occurs within 15-65 s of contact at -35 degrees C and onset of cold pain occurs within 5 s of contact at -20 degrees C. The predictive model subsequently developed was a non-linear exponential expression also reflecting the effects of material thermal properties and initial temperature. This model provides information for the protection of workers against the risk of cold injury by establishing the temperature limits of cold touchable surfaces for a broad range of materials, and it is now proposed as guidance values in a new international standard.

Influence of Sulphur Content and Molten Steel Flow on Entrapment of Bubbles to Solid/Liquid Interface

The sliver defects which occur easily on ultra low carbon steel sheet are the most harmful defects, especially to automobile outer panel products. There may be many causes of the sliver defects such as nonmetallic inclusions, bubbles, surface cracks and inner cracks. However, crack formation is not a serious problem in continuously cast ultra low carbon steel because of its good ductility at high temperatures. Therefore, it is important to reduce the amount of nonmetallic inclusions and bubbles just below the slab surface. Electro-Magnetic Stirring in the mold (M-EMS) is an effective tool to remove such bubbles and reduce the amount of the sliver defects, although the effects of M-EMS on the reduction in sliver defects are influenced by the chemical composition of steel, especially by the sulphur content. The slabs cast at No.4CC-1 st strand in Kakogawa Works reveal rather a high content of bubbles when the sulphur content is higher and M-EMS is not applied. In this study, the reason why sliver defects caused by bubbles are more likely to occur on steel of higher sulphur content is discussed based on the interaction between advanced solid/liquid interface and bubbles. The forces acting on the bubbles are theoretically described as a function of bubble radius, velocity and interfacial tension gradient of liquid steel in front of a solid/liquid interface.

Flyrock phenomena and area security in blasting-related accidents

In both the mining and construction industries, blasting is the predominant method for fragmentation of consolidated mineral deposits. The blasting process, however, remains a potential source of numerous hazards to people and surrounding objects. This paper presents the results of the research study on flyrock phenomena and blast area security related accidents in surface mining. The study revealed that a total of 45 fatal and 367 non-fatal accidents in coal, metal and non-metal surface mines had occurred between 1978 and 1998 where the primary causes were the lack of blast area security, flyrock, premature blast, and misfires. The lack of blast area security and flyrock accounted for 281 (68.2%) accidents. Investigations of flyrock accidents have revealed one or more of the following contributing factors: discontinuity in the geology and rock structure, improper blasthole layout and loading, insufficient burden, very high explosive concentration, and inadequate stemming. The study also shows that accidents due to lack of blast area security are caused by failure to use appropriate blasting shelter, failure to evacuate humans from the blast area, and inadequate guarding of the access roads leading to the blast area. The research results should have a positive impact on hazard awareness, prevention, and safe blasting practices in mining and construction industries.