Renewable Surface Research Articles

Restoration of the face of a GTE blade tip by pulse laser cladding

Restoration of the face geometry of a GTE blade tip by pulse laser cladding is considered. The algorithm of the engineering procedure is proposed. The renewed surface is studied by macro- and microanalyses.

Surface segregation of cadmium atoms at the interface of mechanically renewable Ag–Cd alloy electrode with surface-inactive electrolyte solution

The surface segregation of cadmium atoms at the interface of mechanically renewed electrodes of the Ag–Cd alloy (containing 1 at % Cd; the region of cadmium solid solutions in silver) with a surface-inactive electrolyte solution is studied in the potential range of ideal polarizability by means of impedance spectroscopy and cyclic voltammetry. It is shown that method of mechanic renewal makes it possible to obtain well reproducible data on the kinetics of electrode surface enrichment with atoms of cadmium which is the surface-active component of this alloy. As follows from the analysis of dependences of the electric double layer (EDL) capacitance on the potential (C vs. E curves) pertaining to different times after the electrode renewal, these dependences can be well described in terms of the model of capacitors connected in series (“the common dense layer”). Using this model, the dependences of the alloy surface coverage with cadmium atoms on the time of exposure of the freshly renewed electrode surface to the electrolyte solution are calculated. The mechanism of surface segregation of cadmium atoms is proposed. It allows the kinetics of relaxation processes that occur in the alloy surface layer to be consistently interpreted. The electrochemical data are supplemented and compared with the results of analysis of the surface composition and the data of the profile analysis over the depth of the same alloy at its interface with vacuum, performed by means of Auger electron spectroscopy.

Research on surface topography wear of textured work roll in cold rolling

Purpose– The purpose of this paper is to build a transient wear prediction model of surface topography of textured work roll, and then to investigate the wear performance of different original textured surfaces. The surface topography of steel sheets is one of the most important surface quality indexes, which is inherited from the textured work rolls in cold rolling. Surface topography of work roll is obviously changing in the cold rolling process. However, surface topography is difficult to measure in the industry production process.Design/methodology/approach– This paper presents a numerical approach to simulate the wear process based on the mixed lubrication model of cold rolling interface developed by Wilson and Sheu (Sheu and Wilson, 1994). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the volume is removed by an abrasive particle which is an abstract concept based on the wear phenomenon of textured work roll. At each simulation cycle, the distribution of the contact pressure is calculated by the lubrication model. The material is removed by an abstract abrasive particle and the surface topography is modified correspondingly. The renewed surface topography is then used for the next cycle.Findings– Through comparative analysis, it can be found that the simulation results possess similar statistical characteristic with the measured data. A set of roughness parameters such as the amplitude, spacing and frequency-domain characteristics are introduced to analyze the wear performance of different textured surfaces. Numerical examples show that the surface topography has a significant effect on the wear performance of work roll in cold rolling.Originality/value– The proposed model can accurately predict the wear process of the surface topography in the cold rolling process, which provides the foundation for optimization of original surface topography of textured work roll. The model can also be considered as a tool applicable for research on control of the surface topography of steel strip in the cold rolling process.

Climate processes in the nival-glacial zone of Trans-Ili Alatau and their impact on mountain glaciation and runoff

On the basis of the latest monitoring data of a high-mountainous glaciological station of Institute of Geography, Republic of Kazakhstan on modern climate changes in the nival-glacial zone and their occurrences in the mode of river runoff are analyzed. Tendencies of changes of the 10 meteorological elements for various intervals of averaging as for the years 1971–2011 are studied (winter, summer and annual mass balance of Central Tujyksu Glacier and annual runoff of the rivers of Ili river basin). Results of the analysis confirm continuation of climate warming in the region; the air temperature in nival-glacial zone raised is commensurable to growth of temperatures in foothill and low mountain zones; the dates of the beginning of snow melting and dates of stable transition of air temperature through 0 °C in the spring and on later terms in the autumn moved for the earlier time; the quantity of precipitation tended to increase especially for the cold period and July. Average temperatures of the cold period grew more intensively than in the summer period. Warming of the nival-glacial zone induced not only due to increase of summer temperatures, but also due to appreciable increase of autumn air temperatures especially in September as well as due to increases of the warm period duration. Starting from 1975 the significant positive trend in long-term fluctuations of runoff for all researched rivers is observed. For the period 1975–2011, steady growth of seasonal snow cover depth in the nival-glacial and middle-mountainous zones of Zailiyskiy Alatau is observed. Positive changes in the fluctuations of winter, summer and annual mass balance of glacier are observed. Nowadays natural climatic influences to the rivers runoff in Ili-Balkash region and renewed surface water resources exceed anthropogenic influences which were determining in the zone of runoff dispersion during the low-flow period.

Sensitive determination of pesticide imidacloprid using a glassy carbon electrode modified with a film composed of multi-walled carbon nanotubes and poly(aspartic acid)

A new voltammetric sensor, based on multi-walled carbon nanotubes (MWCNTs) composite poly(aspartic acid) film modified glassy carbon electrode, was fabricated and used for determination of pesticide imidacloprid. The synergistic effect of MWCNTs and the polymer resulted in a significantly improved electrochemical response (in terms of sensitivity, accuracy and analytical range) towards imidacloprid. Under selective conditions, the determination linear range was from 1.53 × 10−5 g L−1 up to 1.53 × 10−2 g L−1 with a detection limit of 1.15 × 10−5 g L−1 (S/N = 3). The sensor also had an easily renewable surface, good fabrication reproducibility, and inherent stability. Moreover, satisfactory results were obtained with complex samples and demonstrate the reliability of the proposed method.

Molecularly imprinted fibers with renewable surface for solid-phase microextraction of triazoles from grape juice samples followed by gas chromatography mass spectrometry analysis

This paper describes the synthesis and characterization of a new molecularly imprinted solid-phase microextraction fiber able to renew its selective binding sites because of the gradual thermal decomposition of the polymeric network. The injector of the chromatograph operates at 300 °C, and during the desorption step of the analytes (in a short period), the polymeric network is degraded from the surface to the core in volatile compounds that do not interfere with the analysis. The renewable MIP fiber was successfully employed to extract triazole fungicides (triadimenol, tebuconazole, and metconazole) from grape juice samples followed by gas chromatography mass spectrometry analysis. The method was adjusted to the quadratic models from 100 to 2000 μg L(-1), with good precision and accuracy. The limits of quantification (100 μg L(-1) for all analytes) were sufficient to analyze triadimenol, tebuconazole, and metconazole in grape juice samples, where their maximum residue limits in Brazil are 100, 2000, and 1000 μg L(-1), respectively.

Water Resources of African Circum-Sahara Sub Region (Renewable and Non-renewable Approach)

Circum is a preposition in Latin meaning “around” and Sahara is a preposition in Arabic meaning “Desert” so it is the regions around African desert. Studies related to Circum-Sahara are too little in-depth knowledge and focus on certain basins but, are generally limited by national boundaries, and do not take account of the transboundary portions of the reservoirs. The resulting development plans for these limited resources, thus, are seriously impeded by ignorance of the mutual effects of intensive withdrawal. Circum –Sahara region has the least renewable water resources of all geopolitical regions of the world, after the Middle East where the renewable fresh natural water resources amounts to 520 km3/year compared to 42,600 km3/yr worldwide. Surface water resources: These are represented by nine border crossing river basins of 1. Nile, 2. Niger 3. Senegal, 4. Gambia, 5. Volta, 6. Chari, 7. Guir-Saoura; 8. Mejerdah; 9. Juba-Shebelle. However and as a result of the arid or semi-arid climatic conditions which prevail in most of the region, the renewable surface water resources are not only temporally irregular but also often difficult to store. Groundwater resources: These are represented by eight border crossing aquifers and can be classified as renewable and non-renewable groundwater resources, these are 1- Nubian Aquifer System (NSAS); 2- North-Western Sahara Aquifer System (NWAS); 3-Senegalo-Mauritanian Aquifer System (SMAS); 4-Taoudeni Aquifer System (TAS); 5-Mourzouk-Djado Aquifer System (MDAS); 6-Irhazer-Iullemeden Aquifer System (IMAS); 7-Chad Aquifer System (CAS); 8- Errachidia Aquifer System (EAS). The yield of natural resources per inhabitant amounts to 1,000 m3/yr per inhabitant (which corresponds to a population density of 1,000 inhabitants per million m3/yr of resource) .At the present time, six countries of the Circum-Sahara region have natural water resources below 1,000 m3/yr per inhabitant (essentially the Maghreb, in addition to Egypt and Kenya). One of these, Libya, has less than 500 m3/yr. In 2025, another four more countries (Burkina Faso, Ethiopia, Morocco and Somalia) will have resources below 1,000 m3/yr per inhabitant, making a total of ten countries and 405 million inhabitants (69% of the total of all the Circum-Sahara countries).The future hydrology of this region is not rosy and may lead to political disputes.

Keynote--Microsphere-Based Detection of Biological Toxins and Signaling Molecules Using Renewable Surface Microfluidic Platforms With Enhanced Mass Transport and Capture

not Available.

Potential dependence of anodic current transients on the renewed gold surface in thallium-containing thiosulfate solutions

The effect of potential on the anodic current transient times τp, which were measured on the gold electrode surface renewed by cutting off a thin surface metal layer immediately in the thallium-containing thiosulfate solutions of compositions (M): 0.05 Na2S2O3, 10−5 to 10−4 TlNO3, and 0.25 K2SO4, is studied. It is shown that the logarithm of inverse transient times 1/τp linearly depends on the electrode potential. Using the microgravimetrical method, it is found that, in the studied potential range, the amount of chemisorbed thallium ions only slightly depends on the potential, and at E = 0.3 V, it is approximately 0.12 μg/cm2. It is evidenced that the transients reaches a plateau, when an equilibrium surface concentration of catalyst is reached. The value 1/τp reflects the rate of electrochemical oxidation of preliminarily adsorbed thallium(I) ions with the formation of catalytically active thallium(III) ions, and the first electron transfer is the limiting stage of the process.

Surface segregation of silver atoms on Au–Ag alloys according to data of laser-heating induced temperature potential shifts, XPS and conventional electrochemical methods

Process of the surface segregation of Ag atoms at the interface of Au–Ag alloy electrodes with the surface inactive electrolyte (NaF) was studied in the potential region of ideal polarizability by the methods of potential shifts induced by laser heating, impedance and cyclic voltammetry. It was shown that impedance measurements on electrodes with the mechanically renewed surface make it possible to obtain well reproducible data on the kinetics of enrichment of the electrode surface layer with silver atoms. As follows from analysis of capacitance vs. potential dependences measured at different moments after the electrode renewal, these dependences are well described by the model of “common diffuse layer”. The use of this model allowed us to calculate the time dependences of the electrode surface coverage by silver atoms after renewal. Specific features of the influence of the electrode potential on the kinetics of the surface segregation of Ag atoms at the Au–Ag electrode surface were demonstrated and analyzed within the framework of the bulk diffusion model. Data for the metal/solution interface were supplemented by the XPS data for Au–Ag/vacuum interface.

VTT aims to develop plastic composites containing peat fibre

In Finland, the VTT Technical Research Centre has developed methods and product innovations to process the most rapidly renewable surface layer of peat instead of using it for energy production. The goal is to develop bio-based composite materials containing peat fibre, for example for the manufacture of consumer products and construction materials, at the same time reducing the use of oil-based raw materials in production. The advantages of products containing peat fibre are their biological origin, low cost, water resistance, impact strength, excellent fire endurance characteristics and biodegradability, according to VTT.

Recent advances in graphite powder-based electrodes

Graphite powder-based electrodes have the electrochemical performance of quasi-noble metal electrodes with intrinsic advantages related to the possibility of modification to enhance selectivity and their easily renewable surface, with no need for hazardous acids or bases for their cleaning. In contrast with commercial electrodes, for example screen-printed or sputtered-chip electrodes, graphite powder-based electrodes can also be fabricated in any laboratory with the form and characteristics desired. They are also readily modified with advanced materials, with relatively high reproducibility. All these characteristics make them a very interesting option for obtaining a large variety of electrodes to resolve different kinds of analytical problems. This review summarizes the state-of-the-art, advantages, and disadvantages of graphite powder-based electrodes in electrochemical analysis in the 21st century. It includes recent trends in carbon paste electrodes, devoting special attention to the use of emergent materials as new binders and to the development of other composite electrodes. The most recent advances in the use of graphite powder-modified sol-gel electrodes are also described. The development of sonogel-carbon electrodes and their use in electrochemical sensors and biosensors is included. These materials extend the possibilities of applications, especially for industrial technology-transfer purposes, and their development could affect not only electroanalytical green chemistry but other interesting areas also, for example catalysis and energy conversion and storage.

Estimation of degree of lability of gold(I) sulfite and thiocarbamide complexes

The supposition that gold thiocarbamide complexes can be involved in the reduction of electrochemically inactive sulfite complex gold ions as intermediate species is supported by investigating the kinetics of cathodic process in the solution of the following composition: 10−3 M Na3Au(SO3)2, 0.1 M Na2SO3, 0.1M thiocarbamide (TC), and 0.2 M Na2SO4. The study was performed by the potentiodynamic method in the potential scan rate range from 0.05 to 1 V/s using an electrode with mechanically renewed surface. It is found that both Au(SO3)23−, and Au(TC)2+ are labile complexes. This confirms the hypothesis for the mechanism of the catalytic effect of thiocarbamide on the electrode processes involving gold ions in the sulfate solutions, which was proposed earlier.

Back to the Moon: The scientific rationale for resuming lunar surface exploration

The lunar geological record has much to tell us about the earliest history of the Solar System, the origin and evolution of the Earth–Moon system, the geological evolution of rocky planets, and the near-Earth cosmic environment throughout Solar System history. In addition, the lunar surface offers outstanding opportunities for research in astronomy, astrobiology, fundamental physics, life sciences and human physiology and medicine. This paper provides an interdisciplinary review of outstanding lunar science objectives in all of these different areas. It is concluded that addressing them satisfactorily will require an end to the 40-year hiatus of lunar surface exploration, and the placing of new scientific instruments on, and the return of additional samples from, the surface of the Moon. Some of these objectives can be achieved robotically (e.g., through targeted sample return, the deployment of geophysical networks, and the placing of antennas on the lunar surface to form radio telescopes). However, in the longer term, most of these scientific objectives would benefit significantly from renewed human operations on the lunar surface. For these reasons it is highly desirable that current plans for renewed robotic surface exploration of the Moon are developed in the context of a future human lunar exploration programme, such as that proposed by the recently formulated Global Exploration Roadmap.

New type of discharge-produced plasma source for extreme ultraviolet based on liquid tin jet electrodes

A new approach for discharge-produced plasma (DPP) extreme ultraviolet (EUV) sources based on the usage of two liquid metallic alloy jets as discharge electrodes has been proposed and tested. Discharge was ignited using laser ablation of one of the cathode jets. A system with two jet electrodes was tested at a repetition rate of 1 to 5 kHz with dissipated electrical power up to 20 kW. Radiating spectra, time characteristics, and conversion efficiency are similar to conventional DPP schemes with rotating wheels. In the first experiments, the Ga:Sn eutectic alloy, which is liquid at room temperature, was circulating in a closed loop. The high velocity of the jets (30 m/s) ensures a renewed electrode surface for every shot, for a repetition rate frequency of up to 30 to 50 kHz, and provides effective heat transportation from the discharge zone. Modeling and experiments demonstrate that the proposed scheme is able to dissipate up to 200 kW of electrical power without overheating the nozzles and tin surface. It was found that the flexible electrode configuration allows the channeling of essential parts of debris plasma in directions opposite to the EUV collector.

Voltammetric Determination of Dinitronaphthalenes Using a Silver Solid Amalgam Paste Electrode

The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electrode (AgSA-PE), based on the mixture of a fine silver solid amalgam powder (60:40 (w(Hg)/w(Ag))) and a suitable organic pasting liquid (Paraffin oil) in a ratio of 20:1 (w/w), was investigated in an aqueous-methanolic media (1:1). This alternative working electrode provides simple preparation and handling, adequate mechanical stability, easily renewable electrode surface, sufficiently wide cathodic potential window (up to -1200 mV within a pH range of 2.7-12.3), and sufficient sensitivity without any necessary pretreatment. The practical usability of the AgSA-PE was verified by the development of voltammetric methods for the determination of selected environmentally important pollutants (1,3-, 1,5-, and 1,8-dinitronaphthalenes) in an aqueous-methanolic media (1:1). The differential pulse voltammetric methods at AgSA-PE give linear concentration dependences in the range of 1-100 µmol l(-1) with limits of detection of about 1 µmol l(-1) in a mixture of Britton-Robinson buffer of appropriate pH and methanol (1:1).

Performance of Field Installations of Next-Generation Concrete Surface

The next-generation concrete surface (NGCS) is the first concrete texture to be introduced in the past 20 to 30 years. NGCS was conceived as a manufactured texture whose properties were more consistent and predictable and is the quietest nonporous concrete texture developed to date. At the time of construction, the NGCS typically had a noise level of 99 dBA and has had a range of up to 101 dBA over time. Although the NGCS has been in service only 3 years, it is under evaluation at 14 locations in nine states. Data for both noise and friction suggest that the NGCS is performing as intended. The large land surface and the grooves appear to provide the advantage of accident reduction in wet weather. NGCS construction properties provide the platform for a renewable surface called the NGCS LITE.

De-alloying kinetics of an Au-based amorphous alloys

The process of de-alloying, i.e. removal of a less noble metal from an alloy, is applied here by electrochemical means to a Au-based metallic glass, Au40Cu28Ag7Pd5Si20, as a function of potential, temperature, and time. Very fine crystals nucleate with random orientation at the solid–electrolyte interface forming ligaments. The resulting material is constituted by ligaments made of pure Au and pores of smaller size whose dimensions coarsen up as a function of time to slightly above two hundred and below one hundred nanometers, respectively. The microstructure is uniform on both surfaces and across the ribbon. The extent of de-alloying is measured by monitoring the heat of crystallisation of the remaining amorphous phase giving linear trend vs time suggesting the reactions occur on continuously renewed surfaces.

Investing in the curricular lives of educators: Narrative inquiry as pedagogical medium

This paper draws on the experiences of two graduate level curriculum theory classes taught at different teacher education institutions in the US. Teacher educators and curriculum theorists invest in creating reflexive spaces for teachers to explore the complex terrain of lived curriculum. Narrative inquiry is chronicled as acting as an important pedagogical medium toward this aim. The purpose of the paper is to explore what practicing teachers’ narratives reveal about their curricular roles in relation to theory and practice. As participating educators consider their associated teaching identities, phenomenological notions of place are found to be fitting as they navigate understandings of lived curriculum as situated, thoughtful, and intentional. Insights generated through reflexive analysis manifest three thematic intersections: (1) Teachers confronting dissonance between theory and practice as teaching identity displacement; (2) Teachers negotiating greater implacement; and (3) Teachers moving toward embodying the creative space for teaching and learning. Renewed roles surface for teacher educators and curriculum theorists, challenging all involved to purposefully foster contexts for professional learning rather than subservience, and claim the responsibilities to provide the intellectual, emotional, and pragmatic spaces where teachers’ lived curriculum efforts can be developed and nurtured.

Mock-up Divertor of KTM Tokamak on the Basis of Lithium CPS

The objective of this work is to carry out the tests of the KTM tokamak lithium divertor model as well as develop recommendations on the use of lithium technologies in tokamak-reactors. Li-technology will be developed and a Na-K cooled KTM tokamak lithium divertor module will be designed and tested as a result of the project completion. It will be possible to operate the renewed lithium surface module under specific heat loads from 2 to 10 MW/m2 while in a quasi-stationary mode, discharge duration of up to ~5 s. The technical project proposal; design scheme and sketches; and procedure development for preparation, protection, cleaning and rehabilitation of lithium CPS (capillary-porous system) surfaces in tokamak conditions have been completed. The design substantiation calculations; technique development for lithium handling in tokamak conditions; and confirming experiments on T-11M tokamak to prove the procedures developed are still in a progress. The study of both the lithium influence on the KTM plasma discharge parameters and specific power load on the plasma facing components as well as the selection of optimum operational modes of the lithium divertor will be accomplished after completion of the start-up and adjustment tests of the KTM tokamak divertor demonstration models.