Polished Copper Research Articles

A hybrid experimental configuration for emissivity measurement at cryogenic temperatures

Abstract In cryogenic and high vacuum systems, radiation mode of heat transfer is the primary source of energy interaction owing to the wide temperature differentials and very low temperatures and pressures. Measurement of radiative properties such as emissivity is crucial in the design of cryogenic systems. Emissivity measurement at cryogenic temperatures requires careful consideration of the sample preparation and measurement conditions to ensure accuracy and reliability. Most experimental techniques developed so far are complex in their design and equipment, and they work only on a single measuring method. To address these challenges, this research has proposed a simpler and hybrid experimental setup that could employ both calorimetric and heat flux methods to directly measure the total hemispherical emissivity in the range 90 K–180 K. Experiments were conducted with five types of materials (black paint, stainless steel, aluminum foil, aluminized mylar foil, and copper sheet) by using both methods, and the results were validated with the literature data. The data obtained by calorimetric and heat flux methods for each sample showed a high level of consistency with each other, with a variation of only ±1.5%. Moreover, the discrepancy between the measured and literature data was within the acceptable range of 0.3%–10%. The total hemispherical emissivity of mechanically treated copper was higher than that of chemically polished copper by 11%. This simplified setup has incorporated all possible means to minimize heat leakages into and from the cryostat while maintaining accuracy. The obtained data can be used to accurately estimate the radiation heat loads in cryopumps and other cryogenic systems that use similar components.

Comparison between pool boiling system of graphene quantum dots and nitrogen-doped graphene quantum dots suspended in binary base fluids

Using nanofluids instead of conventional heat transfer fluids as a passive method is a well-established and widely used technique by researchers to increase the rate and thermal performance of engineering equipment. In this study, the hydrothermal method with a bottom-up approach was used for the synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots. Then, nanofluid samples were prepared in a two-step process, by adding nanoparticles to binary base fluids of deionized water and ethylene glycol in volume concentrations of (50:50) and (60:40), in four concentrations of 100, 200, 500, and 1000 ppm. In order to better understand the boiling heat transfer mechanism and measure its characteristics such as critical heat flux and heat transfer coefficient, an experimental system was designed and built. Nanofluids based on graphene quantum dots have unique features such as compatibility with the environment, economic efficiency, high stability and suitable heat transfer capability. For this reason, their selection in the pool boiling heat transfer process, in addition to saving energy, is introduced as one of the most effective options for improving CHF and HTC. The tests were performed under saturated conditions, atmospheric pressure, and on a vertical flat and polished copper thermal plate. Prepared nanofluids GQDs and N: GQDs based on DI-water maintained their apparent stability for two months. For GQDs nanofluids at an optimal concentration of 500 ppm with a volume ratio of (60:40) DI-water and EG, compared to DI-water, the greatest increase in CHF and HTC is 90.69, 85.011 % and for N: GQDs at a concentration of 500 with a volume ratio (50:50) DI-water and EG, 75.37 and 78.17 % compared to DI-water.

Energy-efficient microwelding of copper by continuous-wave green laser: Insights into nanoparticle-assisted absorptivity enhancement

As a highly reflective material, copper has been difficult to weld with IR lasers. Short-wavelength (400–600 nm) lasers offer promising solutions to copper welding due to significant increases in absorptivity (to > 50 %). In this work, we present an experimental study on copper welding by CW green laser. We unveil that nanoparticles redeposited on the copper surface from the vaporized plume can strongly modify the surface condition and result in significant enhancement of the surface absorptivity. The absorptivity can be theoretically enhanced by nanoparticles up to 82 % compared to the polished copper surface. Assisted by this absorptivity enhancement, the threshold power density (critical laser intensity) for copper melting is reduced by more than 50 %, so that continuous and smooth conductive welding tracks can be generated in energy-efficient manner. In situ deposition of nanoparticles generated upon cooling and oxidation of the vapor plume in the vicinity of the melt zone has been identified as the key mechanism of absorptivity enhancement. XPS measurements of the nanoparticles indicated that Cu2O is the dominant species in the redeposited nanoparticles. This study provides novel insights into the fundamental mechanisms in highly-reflective material welding by short-wavelength lasers and offers an opportunity for energy-efficient high-quality welding of highly-reflective material thin films, which can find numerous applications in consumer electronics and electric vehicles, as well as battery industries. Moreover, it enables a new process-material-environment design route for laser additive manufacturing of nanoparticle-reinforced metal matrix composites.

Battery Electric Roof Bolter versus Diesel Roof Bolter—Results of Field Trials at a Polish Copper Mine

Battery Electric Roof Bolter versus Diesel Roof Bolter—Results of Field Trials at a Polish Copper Mine

A novel strategy of inserting radiation shields to enhance the performance of thermoelectric generator systems for industrial high-temperature heat recovery

Static thermoelectric generator (TEG) systems have been widely used for recovering the high-temperature heat from the industrial sector. To control the heat loss through the gap uncovered by the thermoelectric legs for system performance improvement, a novel strategy of inserting the radiation shields in the gap that introduced additional surface and spacing resistances and regulated the gap radiation loss, was proposed. With a constructed high-fidelity theoretical model which used the finite element method to consider the temperature-dependent properties of the thermoelectric materials, comprehensive comparisons were conducted between the systems with/without radiation shields and using three commonly adopted strategies to evaluate the effectiveness and potential of this strategy. Compared to the base case without radiation shields, inserting one radiation shield with an emissivity of 0.5 enhances the TEG efficiency and system power by 15 % and 9.5 % respectively. The system using the proposed strategy outperforms that using the commonly adopted strategies, especially the strategies of lowering the gap pressure and filling the gap with thermal insulation materials, highlighting the potential of the proposed strategy. Besides, the influences of the shield emissivity and number were studied; from it, less than two radiation shields made by the polished copper are recommended for practical applications.

Influence of chemistry and topography on the wettability of copper

To understand the complex interplay of topography and surface chemistry in wetting, fundamental studies investigating both parameters are needed. Due to the sensitivity of wetting to miniscule changes in one of the parameters it is imperative to precisely control the experimental approach. A profound understanding of their influence on wetting facilitates a tailored design of surfaces with unique functionality.We present a multi-step study: The influence of surface chemistry is analyzed by determining the adsorption of volatile carbonous species (A) and by sputter deposition of metallic copper and copper oxides on flat copper substrates (B). A precise surface topography is created by laser processing. Isotropic topography is created by ps laser processing (C), and hierarchical anisotropic line patterns are produced by direct laser interference patterning (DLIP) with different pulse durations (D).Our results reveal that the long-term wetting response of polished copper surfaces stabilizes with time despite ongoing accumulation of hydrocarbons and is dominated by this adsorption layer over the oxide state of the substrate (Cu, CuO, Cu2O). The surfaces’ wetting response can be precisely tuned by tailoring the topography via laser processing. The sub-pattern morphology of primary line-like patterns showed great impact on the static contact angle, wetting anisotropy, and water adhesion. An increased roughness inside the pattern valleys combined with a minor roughness on pattern peaks favors air-inclusions, isotropic hydrophobicity, and low water adhesion. Increasing depth of the primary topography can also induce air-inclusions despite increasing peak roughness while time dependent wetting transitions were observed.

Effect of porosity on deuterium retention in titanium thin film

Abstract The absorption process of deuterium in titanium was studied in titanium film produced in two different types of copper substrate, one was a polished copper substrate and the other one was chemically etched copper substrate. Titanium film was produced by thermal evaporation method. It was activated at a temperature of 500 0C followed by deuteration at room temperature. Titanium film was characterized by XRD for crystallographic information, SEM for surface morphology, RGA for deuterium desorption studies and weight measurement for D/Ti ratio. The difference in porosity of both the samples is confirmed from XRD analysis and SEM images. Different diffusion process is observed in two different substrates from the RGA spectra. Presence of multiple trap sites in the thin film of both the substrates is observed from the RGA spectra. From the weight measurement, D/Ti ratio in polished substrate is found to be 1.03 whereas in case of chemically etched substrate it is 1.54.

Geomechanical and Technical Aspects of Torpedo Blasting under Seismic and Rockburst Hazard Conditions in Legnica–Glogow Copper District Mines

The dominant hazard in the Polish copper ore mining industry (LGCD mines—Legnica–Glogow Copper District) is the occurrence of mining tremors and rockbursts. One of the effective active methods of preventing this threat is torpedo blasting, which results in disturbing the structure of roof rocks. A change in the integrity of a roof, especially in the tremor-generating layer or in the contact between stiff rock layers, reduces the possibility of an elastic energy concentration and may also be a kind of stress concentrator, provoking the destruction of rocks. This article presents original solutions for determining the areas of rock mass within a mining area where it is advisable to conduct torpedo blasting, and the experience of blasting in the Rudna copper mine in the LGCD is described. The first part of this article presents the results and experiences of using torpedo blasting prevention in the LGCD mine conditions in the Rudna mine. Assuming that due to the stress of the rocks, torpedo blasting brings the greatest benefits in the areas of elastic energy concentration, the second part of this article presents the results of numerical modeling, on the basis of which the zones of elastic energy concentration in the form of total, shear and volume deformation were determined in the vicinity of mining activities for typical geological and mining conditions in the LGCD. The importance of methods for the verification of the proposed solutions based on the analysis of seismic activity and geophysical mechanisms of events’ foci and seismo-acoustic emissions was also emphasized. The numerical simulations performed and conclusions from in situ observations allowed the formulation of general principles for the selection of torpedo blasting parameters.

Boiling heat transfer characteristics of self-rewetting fluid based on the bi-porous sintered surface

Enhancing boiling heat transfer by changing the working fluid or surface modification is an effective and simple method. In order to investigate the effect of the coupling characteristics of porous sintered surfaces with self-rewetting fluid, pool boiling experiments were carried out on the polished copper surface (PCS) and the bi-porous sintered surface (BPS) with n-heptanol aqueous solution as the working fluid. The experimental results showed that, for the PCS cases, the self-rewetting fluid enhanced the heat transfer coefficient (HTC), while reduced the critical heat flux (CHF). This is because while self-rewetting fluid promoted the generation and detachment of bubbles, it also caused gas–liquid conflict, resulting in the surface was covered by a layer of vapor film. As for the boiling experiments on the BPS, the self-rewetting fluid not only enhanced the HTC but also enhanced the CHF. The Marangoni effect, generated by the self-rewetting fluid, replenished the BPS and coupled with its stronger capillary force. That led to surface wetting and reduced conflict between gas and liquid flow. Consequently, under this coupling effect, the heat transfer coefficient (HTC) of 0.1 wt% n-heptanol aqueous solution was 178.7 % higher than that of deionized water with PCS.

An Analysis of the Impact of Mining Excavation Velocity on the Development of Gaseous and Gaseous Geodynamic Hazards in Copper Ore Mines

The hazards of gaseous geodynamic phenomena and rockbursts are among the most challenging to assess and classify. This perception arises from both a review of the literature and an examination of available instructions and regulations in underground mining facilities. The hazard of gaseous geodynamic phenomena in Polish copper ore mines only appeared in 2009, whereas these phenomena occur and are commonly described in other mining countries. In Polish copper ore mines, due to the room and pillar system in fields with lengths of about 460 m, very often parallel to neighboring fields, which together give a length of about 900 m, it is difficult to identify the location of gas traps due to the large size of the area. This paper presents an analysis of the influence of the velocity of the excavation on the possibility of escalating or reducing the described mining hazards. An analysis of the impact of excavation velocity on the state of gaseous geodynamic and roof fall hazards was conducted for two mining fields. For the considered mining fields, the hypothesis was formulated that an excavation velocity greater than or equal to 17 m/month positively influences a reduction in both gaseous geodynamic and roof fall hazards.

Cross-linked polymer film on copper stubs as a reusable substrate enabling imaging and quantitative analyses of aluminosilicate particles

Access issues to potable waters around the planet is the motivation for research in desalination technologies. One class of materials that is a research focus for desalination membranes are zeolites that are comprised of silicon (Si), aluminum (Al), and oxygen, and have structures that include regular pores of varying sizes dependent on the type of zeolite. A motivation for this study was to enable characterization of non-conductive materials containing Si or Al (e.g., zeolites) using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. To avoid significant background signals directly overlapping with these samples, common sample supports and preparation protocols involving Al or Si were precluded. Cross-linked polymer coatings applied via spin coating onto polished copper (Cu) stubs are shown to be durable for reuse even with the use of aggressive cleaning techniques between samples. SEM and EDS analyses of Cu stubs were performed before and after applying the polymer coating, after drop-cast application of zeolite particles and after their subsequent removal by sonication-based techniques. The data from those trials confirmed there was no background signal from Si or Al and no cross-contamination between samples during these analyses, enabling quantitation of Al and Si in the samples.

Experimental study of nucleate pool boiling with water in atmospheric pressure

This study experimentally investigated nucleate pool boiling heat transfer for a polished copper surface and water fluid couple under atmospheric pressure. The results were compared with the correlations in the literature. The experimental results were compared with the surface-liquid correlation constants Rohsenow, Pioro, Vachon, Griffith, and Das used for the temperature exceedance values. When the results of Griffith's correlation constant were compared with the experimental values, it was seen that it was the most appropriate correlation compared to other correlations, with a minimum and maximum error of 0.4-12%. In addition, Forster-Zuber, Pioro, Kutateladze old, Kutateladze new, Kruzhilin, and Cooper correlations were compared with experimental results regarding the heat transfer coefficient. Compared with the correlation proposed by Pioro for the heat transfer coefficient, it was calculated as the most suitable correlation with a minimum and maximum difference of 0.2-8%

Boiling Heat Transfer Performance of Pure Water on Binary Oxide-Based Nanoparticles Coatings

Abstract Pool boiling heat transfer performance has been evaluated on a binary oxide based nanoparticles coated surface. Electrophoretic deposition techniques were used for TiO2 and Al2O3 nanoparticles coatings on polished copper substrates. Four different surfaces have been prepared by varying the deposition time 2.5, 5, 10, and 15 min which are referred to in the text as coated surface (CS)#1, CS#2, CS#3, and CS#4, respectively. The surface characteristics like surface roughness, morphology, and wettability have changed after the coating. It has been observed that all the deposited surfaces are hydrophobic, whereas polished copper surfaces are hydrophilic by nature. The boiling heat transfer performance of surface CS#2 is superior to the other three surfaces, while CS#4 is the worst. The highest enhancement in boiling heat transfer coefficient (BHTC) observed for CS#2 is 62.3%, corresponding to a heat flux of ∼220 kW/m2. The coating layer thickness was also observed to be an important parameter, apart from surface roughness, wettability, and morphology, which may be a cause for heat transfer deterioration, if it crosses a limiting value. In this study the limiting value of coating layer thickness discovered ∼15 μm experimentally.

Temperature-Dependent Reflectance of Copper with Different Surface Conditions Measured at 1064 nm

AbstractIn order to fully understand and to eventually overcome the instabilities in laser welding of copper using 1064 nm wavelength lasers, it is important to get a deeper understanding about the interaction of the incident beam with the copper surface during the process. One of the main parameters determining this behavior is the temperature-dependent absorptance. However, the existing datasets only show little consistency between the different sources, do often not include the important absorptance step at melt temperature, or they are only calculated. This article thus presents an experimental approach to measure the reflectance of electro tough-pitch copper (Cu-ETP) from room temperature until beyond the melting point with an integrating sphere setup. The setup was developed with particular attention to measurement accuracy up to high temperatures. The reflectance using a 1064 nm laser under an incident angle of 12° has been measured for four different sample groups, which are untreated rolled copper, mechanically polished copper, oxide reduced copper and resolidified copper. The measurement results reveal significant differences in the temperature-dependent reflectance between the sample types and, for some types, also between the samples of the same type. This study investigates the origins of the most significant features in the reflectance curves and their potential impact on processing copper using NIR lasers.

Microstructural study on the effect of thermo-physical properties for plasma sprayed Ni and Ni[sbnd]20Cr splats formed on Cu substrates

Ni and Ni20Cr powder particles were air plasma sprayed onto polished copper substrates to gain insight into the flattening behaviour of both Ni and Ni20Cr particles (splats) formed on a relatively low melting point material (i.e. copper) substrate. The extent of any interfacial bonding, along with any splat-substrate intermixing derived from the different thermo-physical properties of the sprayed particles were characterised. The plan-view features of the splats were captured using scanning electron microscopy (SEM), while splat-substrate interfacial properties were examined using focused ion beam microscopy (FIB) and transmission electron microscopy (TEM). The chemical characteristics of the splat and substrate were analyzed using energy-dispersive X-ray spectroscopy (EDS). The addition of ∼20 wt% chromium to Ni (i.e the Ni20Cr particles) was observed to significantly influence the spreading behaviour of the particles on impact with the substrate, both the extent of any splat splashing and the splat flattening ratio, as well as the microstructure of the splat-substrate interface, including the degree of substrate melting and the likelihood of material from the substrate jetting into the body of the splat. The evidence of intermixing between the splat and the copper substrate for both feedstocks is an intriguing feature of this study. The presence of a thermodynamically formed copper oxide layer during substrate preheating also influenced both the splat formation behaviour and substrate melting as observed by both microstructural examination and investigation through numerical models.

A geometric approach to evaluating the results of Polish copper ores beneficiation

A geometric approach to evaluating the results of Polish copper ores beneficiation

The Effect of the Blasthole Diameter on the Detonation Velocity of Bulk Emulsion Explosive in the Conditions of Selected Mining Panel of the Rudna Mine

The blasting technique is currently the basic excavation method in Polish underground copper mines. Applied explosives are usually described by parameters determined on the basis of specific standa ...

AN ASSESSMENT OF INFLUENCE OF SELECTED CHARACTERISTICS OF FEED ON THE RESULTS OF BALL MILL GRINDING PROCESS COURSE FOR POLISH COPPER ORES

The article concerns issues related to the copper ore ball mill grinding process, operating at different technological parameters. The aim of the study was to investigate the influence of various operating parameters and feed characteristics on selected technological effects (comminution degree, yields of the finest particle size classes, ready for downstream flotation operations). The research program included grinding tests of two lithological types of Polish copper ore (dolomite and sandstone) and their mixtures in the proportions: 70% dolomite +30% sandstone and 30% dolomite +70% sandstone. Material was treated under wet and dry grinding in Bond’s ball mill. Three different grinding time were applied together with three levels of mill’s rotational speed. The feed material with three different particle size compositions was used in the rests. The results show that increases in yields of fine particle size fractions for each sample are dependent on the particle size composition of feed, grinding time and rotational speed of mill. Together with increasing of grinding time, fine particle size fraction contents increase too, especially for the coarse feed without fine particles. In general, higher comminution degrees were obtained for ore mixtures, the most favorable results for a mixture of 30% sandstone +70% dolomite, where S 50 equaled 358 and S 90 = 178. Correlation analysis showed that in fact all technological parameters under investigation were significantly related to the obtained comminution effectiveness.

Qualitative Description of Metal Ore Deposits Parameters Based on Selected Fuzzy Logic Operators on the Example of a KGHM Polish Copper S.A. Copper-Silver Mine

Qualitative Description of Metal Ore Deposits Parameters Based on Selected Fuzzy Logic Operators on the Example of a KGHM Polish Copper S.A. Copper-Silver Mine

Mono and bilayer coatings of alkanethiol and silane on copper: Prevents corrosion and regulate bacterial adhesion

Self-assembling molecules (SAMs) provide a flexible system for surface modification of materials by forming films of molecular thickness. SAMs protect materials from corrosion and modify surface properties such as adhesion, adsorption and wetting due to their molecular composition and orientation. In this investigation, polished copper specimens were dip coated to form SAMs of alkanethiol and silane to study bacterial adhesion as well as for corrosion prevention. The SAM coated specimens were exposed to the log phase cultures of Pseudomonas aeruginosa (aerobic bacteria) and Desulfovibrio vulgaris (anaerobic bacteria) for 12, 24 and 48 hrs, to monitor cell adhesion and biofilm thickness by microscopy. The results showed that alkanethiols SAM promoted adhesion and biofilm formation. The biofilm thickness ranged from 10 to 38 µm for Pseudomonas and 9 – 25 µm for Desulfovibrio sp. Among the SAM coatings tested, octadecyl-trichlorosilane (ODTCS), alkane-thiol and ODTCS (bilayer SAM) showed no bacterial adhesion, however, solitary alkane-thiol SAM showed significant bacterial adhesion. The high hydrophobicity (contact angle ∼140°), antibacterial and anti-biofilm property of the ODTCS coating could have regulated bacterial adhesion. The constant climate test results showed that silane SAM prevented copper corrosion up to ∼160 days (3480 hrs), while the alkanethiol coating could protect up to 10 days (240 hrs). Confocal laser scanning microscopic images of the silane coated copper specimens showed initiation of the corrosion after 160 days of exposure, while at the end of 200 days significant copper corrosion was observed. Surface modification leads to specific biochemical interactions that regulate bacterial adhesion and prevent biofilm formation and corrosion of copper.