Production Of Foils Research Articles

Degradation of silicon wafers at high temperatures for epitaxial deposition

AbstractThe material quality degradation of silicon wafers by metal impurities, various crystal defects as well as light and thermally induced mechanisms is very important for the solar cell performance and has been investigated by various groups. In this paper, the material degradation during epitaxial deposition at high temperatures above 1100°C will be discussed. Annealing experiments in hydrogen atmosphere are done with the laboratory rapid thermal chemical vapor deposition reactor to mimic the thermal process conditions for epitaxial growth of silicon from the gas phase. A general investigation of crystallographic and electronic properties of n‐ and p‐type silicon wafers has been done between 950°C and 1150°C. A detailed sensitivity analysis of process parameters like cooling ramp, peak temperature, duration, and ambient gasses has been conducted. The degradation mechanism by metal impurities has been investigated by using silicon wafers with different diffusion barriers. Besides effective minority carrier lifetime, measurements by quasi steady state photo conductance, etch pit density, Raman spectroscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy measurements have been done. The presented results have been used to improve the deposition process of epitaxial thin‐film solar cells, the production of silicon foils with a thickness <80 μm, and the fabrication of epitaxial multi junction solar cells with silicon bottom cell.

The Status and Effect of WTO Law Before EU Courts

The legal status and effect of World Trade Organization (WTO) law before European Community (EC)/European Union (EU) Courts has been a contentious issue right from the very beginning. Although there have been a number of cases in which the Court of Justice of the European Union (CJEU) has addressed the issue, the rulings have left practitioners guessing as to the applicability and effect of WTO provisions in specific cases. This problem most recently came to a head when the General Court (GC) annulled a regulation imposing definitive anti-dumping duties on certain aluminium foil products from Rusal Armenal, an Armenian company. The GC found that the regulation was inconsistent with the applicable WTO law (in particular the Anti-Dumping Agreement [ADA]) and therefore invalid. On appeal the CJEU set aside the GC’s judgment on the grounds that WTO law can be relied on before the EU Courts only where the EU intends to implement a particular obligation and/or where the EU act at issue refers explicitly to specific provisions of a WTO agreement. When even the GC has difficulty in correctly applying the rules concerning the applicability and effect of WTO law, it’s time to step back and take stock. In this article we analyse the judicature concerning the principles governing the application and treatment of WTO law by Union Courts and develop an analytical framework to explain when and how WTO law can have an effect before these Courts.

Chitin Foils and Coatings Prepared from Ionic Liquids

Chitin and its deacetylated derivative, chitosan, are nontoxic, antibacterial, biodegradable, and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as scaffolds for tissue engineering, wound dressings, separation membranes and antibacterial coatings. Unfortunately, there is still a lack of suitable solvent systems for the direct processing of chitin, e.g., into films and coatings. Such solvents must be nontoxic, noncorrosive, nondegrading, and allow for high chitin concentrations. Here, the potential of designed ionic liquids (IL) as solvents for chitin is outlined. Phosphonium‐ and imidazolium‐based ILs are synthesized, characterized and the influence of the cation on the solution process has been evaluated. It is shown that particularly imidazolium carboxylate‐based ILs are appropriate solvents for chitin and are suitable for the production of foils and coatings on both fabrics and foams. image

Recommendation of a Measure for Enhancing the Precision of Dimensions of Foil Products in Single Point Incremental Forming Technology

Single Point Incremental Forming (SPIF) has become a popular technology of forming sheet materials in the recent decades. However, the springback phenomenon, an inborn property of almost all elasto-plastic materials, reduces the precision of dimensions of the products by the finished forming session. This paper attempts to find out a measure to minimize this unwanted obstacle by using both empirical and simulating methods in order to define the relations of springback values among the forming parameters such as diameter of the forming tool, its revolution per minute, its velocity and its feed rate. Analyzing these equations to extract the appropriate parameters of forming for enhancing the precision of SPIF products is the final aim of this paper.

Fabrication of isotopic and natural carbon foils by thermal cracking method and some issues

Isotopic and natural carbon foils made by thermal cracking method are used for various purposes in nuclear physics experiments. An apparatus equipped with an oil free vacuum pumping system has been constructed to produce such foils on a resistively heated metallic Ta filament by the thermal cracking method. Properties of the foils such as accessible thickness and area, uniformity, purity and yield in the foil preparation were investigated. We also investigated the following issue during the foil production; when the Ta filament temperature was decreased after the cracking process, the cracked layer sometimes broke into pieces from the filament. Eventually, we could successfully fabricate enriched isotopic 12C foils and natural carbon foils with thicknesses from 0.2 to 5 mg/cm2 and with a dimension of 20 × 20 mm2 or even larger.

Synthesis of microparticles in 1-kbar hydrogen induced by 10-MeV bremsstrahlung γ quanta in a reaction chamber (Part 2)

A chamber filled with molecular hydrogen at 1.0-kbar pressure was irradiated by bremsstrahlung γ quanta with a threshold energy of 10 MeV at a 20- to 21-μA electron beam intensity for 14 h. Investigations of changes in the structure and elemental composition of the entrance window, manganin foil, and reaction product collector are presented in Part 1 of the article [1]. In this work the results of studying synthesized particles and different formations on inner surfaces of the cut-in-half irradiation chamber (brass sleeve) are discussed. Investigations into the two largest synthesized structures, detected after the irradiation, made it possible to establish the presence of light elements from carbon to calcium in them. Like in the first part of the paper, multiple small lead particles were found and studied. The detected synthesized particles have a complex shape and composition. On both sides of inner surfaces of the cut brass sleeve, thin-walled microtubes are also found, like in Part 1 [1]. The formation of new elements and structures is discussed on the basis of the upstream (fusion) and downstream (fission) models of nuclear reactions [1].

Formation Mechanism of Non-conductive PbSO<sub>4</sub> on IrO<sub>2</sub>-Ta<sub>2</sub>O<sub>5</sub>/Ti Anodes in Copper Foil Production

Formation Mechanism of Non-conductive PbSO<sub>4</sub> on IrO<sub>2</sub>-Ta<sub>2</sub>O<sub>5</sub>/Ti Anodes in Copper Foil Production

Supply Chain Management in Condition of Production Company

Contribution presents application of logistic access, solved through Supply Chain Management (SCM) with orientation mainly to the capacity planning of production with aim to increase flexibility and productivity of production process. Such changes are necessary to be realized by change of company strategy, as well as by project’s preparation and change of investment’s aims for realization of transition to new system of production management. Discussion is orientated to concrete conditions of polygraph company in Slovakia, orientated to production, refinement and sale of flexible foils for packages.

Propulsive performance of unsteady tandem hydrofoils in an in-line configuration

Experiments are reported on the behavior of two hydrofoils arranged in an in-line configuration as they undergo prescribed pitching motions over a wide range of phase lags and spacings between the foils. It is found that the thrust production and propulsive efficiency of the upstream foil differed from that of an isolated one only for relatively closely spaced foils, and the effects attenuated rapidly with increasing spacing. In contrast, the performance of the downstream foil depends strongly on the streamwise spacing and phase differential between the foils for all cases considered, and the thrust and propulsive efficiency could be as high as 1.5 times or as low as 0.5 times those of an isolated foil. Particle image velocimetry reveals how the wake interactions lead to these variations in propulsive performance, where a coherent mode corresponds to enhanced performance, and a branched mode corresponds to diminished performance.

Quantitative assessment of industrial symbiosis for the promotion of circular economy: a case study of the printed circuit boards industry in China's Suzhou New District

Abstract By strengthening material metabolism among collocated enterprises in leading industrial production chains in eco-industrial parks (EIPs), an industrial symbiosis (IS) system can be constructed, which is effective in strengthening the circular economy (CE). It has become important for EIPs to quantitatively evaluate the CE performance of the production chain while also seeking specific measures that could promote resources utilization efficiency. In this paper, we combine the substance flow analysis (SFA) approach with the resource productivity (RP) indicator to evaluate the contribution of IS to the development of circular economy. Through questionnaires and field surveys of key enterprises in Suzhou New District (SND), a substance flow analysis and resource productivity indicator were developed for core materials (copper, water and energy) in printed circuit boards (PCB) production under the excluding waste utilization scenario and including waste utilization scenario. The results show that the RPCu of chain from electrolytic copper production enterprises (ECPE) to electrolytic copper foil production enterprises is respectively 21.38 and 23.15 thousand yuan per ton, from ECPE to copper clad laminate (CCL) production enterprises is respectively 64.15 and 71.32 thousand yuan per ton, and from ECPE to PCB production enterprises is respectively 176.47and 211.21 thousand yuan per ton under the two scenarios. RP is enhanced by prolonging the industrial production chain and the RP under the excluding waste utilization scenario is higher than the including waste utilization scenario for the same chain, which can be achieved through greater IS. Finally we propose further implications on developing CE in EIPs.

Advanced Rolling Technologies for Producing Ultrafine-grain/nanostructured Alloys

Ultrafine-grained materials show high strength at ambient temperature, high-speed superplastic deformation at elevated temperatures, and high corrosion resistance. Such materials have attracted increasing attention in the past twenty years. A number of severe plastic deformation techniques, such as equal-channel angular press, high pressure torsion, groove pressing, twist extrusion, asymmetric rolling, and accumulative roll bonding have been used to develop ultrafine-grained bulk materials. The equal-channel angular press, high pressure torsion, twist extrusion and groove pressing techniques suffer from some drawbacks: firstly, forming machines with large load capacities and expensive dies are indispensable for these processes; secondly, the productivity is relatively very limited; thirdly, the techniques are only suitable for small samples. Compared with equal-channel angular press, high pressure torsion, twist extrusion and groove pressing, the accumulative roll bonding and asymmetric rolling techniques can be used to produce continuous ultrafine-grained sheets in large quantities. In this paper, a survey of relatively recent rolling technologies is presented. The merits and drawbacks of each technique are examined. These techniques are: (1) Asymmetric cryorolling, which has potential for large-scale industrial production of nanostructured materials; (2) Four-layer accumulative roll bonding, which has potential to produce nanostructured materials at room temperature with high bonding quality, used for fabrication of ultrafine material sheets; (3) Asymmetric Rolling of accumulative roll bonding-processed sheets, which has potential for large-scale industrial production of nanocomposite foils.

An innovative development of a four-high foil rolling mill

During foil or ultrathin strip rolling, elastic deflection variation of the work rolls at the contact surface with the strip causes non-uniform thickness distribution of the product in the width direction, which possibly causes a central wrinkling or an edge fracture on the product. This study developed a four-high prototype rolling mill, comprising two work rolls fabricated from an ultrastrength alloy. This prototype rolling mill was composed of a housing frame set, a roll set, a roll gap adjusting mechanism, and a power transmission system. The finite element analysis was used for determining the frame dimensions and work roll diameters. Several experimental rolling passes of stainless steel strips were conducted using this self-developed prototype rolling mill to achieve a 0.05-mm-thick foil product.

Multi‐Functional Filters for Metal Melt Filtration

Safety for road and railway vehicles as well as aircrafts requires highly stressable metallic components. The efficiency of these components is highly determined by the materials quality and purity. During the production process, contaminations within the metal melt can occur resulting in defects in the form of inclusions. It is difficult or even sometimes impossible to reduce or remove those inclusions. Within the Collaborative Research Center 920 “Multi-functional filters for metal melt filtration – a contribution toward zero defect materials” funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) in 2011 at the Technische Universität Bergakademie Freiberg focuses on researching a new generation of metal qualities via melt filtration with superior mechanical properties for use in light weight structures and high demand construction materials. The aim of the collaborative research center is an enormous reduction of non-metallic inclusions in the metal matrix by the use of intelligent filter materials as well as filter systems due to functionalized filter surfaces. So called “active” coatings based on the same chemistry as the inclusions can attract more effective the non-metallic particles and lead to a higher deposition on the filter surface. In addition, new “reactive” coatings are investigated in terms of a chemical reaction between the functionalized filter surface and the gases in the metal melts. The surface design, the tailored thermal shock performance with regard to sufficient corrosion and creep resistance are most challenging tasks requiring an understanding of the control of the structural properties of the filter materials in the nano-, micro-, and macro-ranges, interaction at interfaces as well as temperature related phase transformations. The flow dynamic conditions in the filter during casting are of great importance for the proper design of the filter macro-structure. A material as well as a flow computer aided micro- and macrostructure filter design based on investigated filtration mechanisms can lead to high filtration efficiencies with superior properties – strength, fracture toughness, fatigue- of the casted steel, iron, aluminum, silicon, and magnesium components. In addition, other applications such as recycling of metals, the electronic industry via filtration of copper, or the thin steel and aluminum foil production can adapt part of the generated results. The present special issue focuses in a comprehensive way on selected results covering the entire chain of filtration, from the research of the filter materials, the agglomeration and deposition of inclusions on the functionalized filter surfaces, up to properties of the end metallic product. A total of 16 scientific projects with more than 20 funded researchers are working together by bridging different disciplines. A very important subject is also the qualification of the research assistants with the aim of getting a doctorate degree completed by different soft skills. On behalf of the whole team, we would like to thank all the journal editors as well as review members and invite you to share with us our results and awake your curiosity getting in touch with our CRC for fruitful discussions in this interdisciplinary scientific field. Christos G. Aneziris Institute of Ceramic, Glass and Construction Materials

Sputtering angle effects by Kr mixing in N+ ion beam on the lifetime of nitrided carbon stripper foils

Nitrided carbon stripper (NCS) foils with high nitrogen content were produced by ion beam sputtering of reactive nitrogen gas. Such foils seem to be very useful as strippers in high-intensity heavy ion accelerators. We have conducted comprehensive research, development, and production of such foils with high reproducibility. Krypton, a heavy noble gas, was mixed with the reaction nitrogen gas (IBSRN) in the ion beam sputtering process to produce stripper foils with short sputtering deposition time and long lifetimes in the high intensity ion beam irradiation. With the (N2 + Kr) mixed gas ions we investigated the influence of different sputtering angles (α) on the lifetime of the NCS-foils in case of poly-graphite material. The lifetime measurement of these foils of 20 ± 5 μg/cm2 was performed with a 3.2 MeV Ne+ ion beam as usual. The foils made at a sputtering angle of 15° showed a maximum of 11.0 and 7.5 C/cm2 average charge density, respectively, which corresponded to about 275 and 187 times the lifetime of the best commercially available foils.

Fabrication of ultra-thin nanostructured bimetallic foils by Accumulative Roll Bonding and Asymmetric Rolling

This paper reports a new technique that combines the features of Accumulative Roll Bonding (ARB) and Asymmetric Rolling (AR). This technique has been developed to enable production of ultra-thin bimetallic foils. Initially, 1.5 mm thick AA1050 and AA6061 foils were roll-bonded using ARB at 200°C, with 50% reduction. The resulting 1.5 mm bimetallic foil was subsequently thinned to 0.04 mm through four AR passes at room temperature. The speed ratio between the upper and lower AR rolls was 1:1.3. The tensile strength of the bimetallic foil was seen to increase with reduction in thickness. The ductility of the foil was seen to reduce upon decreasing the foil thickness from 1.5 mm to 0.14 mm, but increase upon further reduction in thickness from 0.14 mm to 0.04 mm. The grain size was about 140 nm for the AA6061 layer and 235 nm for the AA1050 layer, after the third AR pass.

Artificial Ageing Behaviour of Al-4Zr Micro Sheets

The continuous miniaturization of products needed e.g. in the automotive or the microelectronics sector requires process chains, which allow the manufacturing of microscopically small components in high quantities. The development of the required processes and technologies is the aim of the Collaborative Research Centre 747 “Micro Cold Forming” of the German Research Foundation. As a necessary step in the manufacturing process chain heat treatment enables the adjustment of the semi-finished micro components to cold forming. Finally, the in-service characteristics of the aluminium components have to be adjusted by precipitation hardening that increases the strength values beyond those which can be achieved by strain hardening. To provide high strength aluminium alloys with an improved thermal stability new alloy concepts and advanced production processes have been developed within the Collaborative Research Centre (CRC). Besides the scandium containing foils made of alloy Al-2Sc, foils of a novel alloy Al-4Zr with approximately 4 mass-% Zirconium has been produced by means of physical vapour deposition (PVD). In contrast to conventional strip casting techniques the PVD process operates with low temperatures, which should suppress premature precipitation during the foil production and ensure the supersaturated solid solution that is a prerequisite for precipitation hardening. Samples of this material were subsequently artificially aged and characterized by ultra micro hardness measurements (UMH), transmission electron microscopical (TEM) analysis and differential power scanning calorimetry (DPSC) to evaluate the applied aging parameters.

Surface Defects in Foil Direct Chill Strip from Highly-Alloyed Aluminum Alloys

The metallurgical industry is faced with the task of improving specific output of final product with high added value. Production of aluminum foil and thin rolled product is not more than 5% of the total output of aluminum within Russia. Within the scope of OK RUSAL there are three foil rolling plants who produce aluminum foil for overseas technology. In processing highly alloyed materials of the 8006 and 3003 series, a problem remains of billet surface quality, reducing output of finished product.

Microstructure Evolution and Composition Control During the Processing of Thin-Gage Metallic Foil

The manufacture of thin-gage superalloy and gamma-titanium-aluminide foil products via near-conventional thermomechanical processing and two different vapor-deposition methods was investigated. Thermomechanical processing was based on hot-pack rolling of plate and sheet. Foils of the superalloy LSHR and the near-gamma titanium aluminide Ti-45.5Al-2Cr-2Nb made by this approach exhibited excellent gage control and fine two-phase microstructures. The vapor-phase techniques used magnetron sputtering (MS) of a target of the desired product composition or electron-beam physical vapor deposition (EBPVD) of separate targets of the specific alloying elements. Thin deposits of LSHR and Ti-48Al-2Cr-2Nb made by MS showed uniform thickness/composition and an ultrafine microstructure. However, systematic deviations from the specific target composition were found. During subsequent heat treatment, the microstructure of the MS samples showed various degrees of grain growth and coarsening. Foils of Ti-43Al and Ti-51Al-1V fabricated by EBPVD were fully dense. The microstructures developed during EBPVD were interpreted in terms of measured phase equilibria and the dependence of evaporant flux on temperature.

Carbon–silicon stripper foils

TRIUMF operates several high power industrial cyclotrons for the commercial production of isotopes for radiological diagnostics and therapy. Two of these accelerators, TR30-1 and TR30-2, are capable of delivering H− beams of 30MeV and beam currents in excess of 1000μA. For many years, in-house produced diamond-like carbon (DLC) foils of various compositions have been utilized to extract proton beams from these cyclotrons (Zeisler and Jaggi, 2008) [1].The TRIUMF Carbon Foil Laboratory, now incorporated as MicromatterTM, uses pulsed laser deposition to fabricate DLC films in a wide thickness range (from 10nm to ∼10μm). More recently, we reported the production of DLC foils containing boron (Zeisler and Jaggi, 2010) [2]. Carbon–boron multilayer foils have outstanding mechanical stability and show an extended lifetime in high intensity proton beams. In an attempt to further enhance the quality of our beam strippers, we investigated the production of carbon–silicon multilayer foils.

ORTHORHOMBIC PHASE TRANSFORMATIONS IN TITANIUM ALLOYS AND THEIR APPLICATIONS

The link and difference between orthorhombic phase transformations in β-type tita- nium alloys and in Ti3Al containing high concentrations of transition metal elements such as Nb are first outlined in this paper. Recent investigations on these transformations conducted in the authors' group are reviewed followed by discussions of remaining problems. Three examples were presented to illustrate the applications of the orthorhombic phase transformations: design and development of superelastic titanium alloys for biomedical use, preparation of ultra-fine basketweave microstructure of titanium alloy wire for fastener manufacturing, and sheet and foil production of alloys based on Ti2AlNb.