Deposition Of Different Layers Research Articles

Characteristics of residual stress distribution in wire-arc additive manufactured layers of low transformation temperature material

High heat input in wire and arc additive manufacturing (WAAM) tends to result in high tensile residual stress, which adversely affects performance and service reliability. However, low-transformation-temperature (LTT) materials are susceptible to compressive residual stresses due to their low phase-transformation point. Here, the LTT material 10Cr10Ni was used as the deposited material to fabricate a pipe structure, and the contour method was applied to measure the residual stress distribution in the cross-section. A thermomechanical coupling analysis model was developed to investigate the residual stress generation mechanism in 10Cr-10Ni(LTT) during the WAAM process. The simulated deformation and residual stress distributions agree well with the measurements. Through simulation analysis of the deposition of different layers, we found the key to the generation of compressive residual stresses in the LTT layers lies in whether there is a transformation from austenite to martensite during the final thermal cycle. When the deposition height exceeded 5.405 mm (approximately four layers), compressive residual stresses were only generated in the last four LTT layers and transformed into tensile residual stresses in the other layers. This results in a concept called the effective region, which can be used as a guide for reducing stress in WAAM using LTT materials.

Finite Elements Modeling of the Delamination Process at Polymeric Composite Structures

AbstractThe delamination process is the main cause of the process of destruction of composite materials and of any technological process of deposition of different layers. This paper presents finite elements modeling of this type of multi‐layer structure failure from a practice experiment. It is thus attempted to create a mathematical model able to predict the behavior of similar structures under different working conditions.

Development of Spray Pyrolysis System for Deposition of Nano-structure Materials

In this paper, we report the development of the spray pyrolysis technique for preparing different nano-structure materials toward the application in thin film solar cells. The spray pyrolysis system can heat up the substrate to 6000C with less than 0.01% full scale. The ramping rate can be set to 100C per minute. The effective coating area can be up to 100 x 100 mm2. Using this technique, the thickness and roughness of the films can be controlled. The obtained morphology, the microstructure of the thin-films, given by scanning electron microscope, X ray diffraction…showed that the system is suitable for deposition of different layers of the dye sensitized solar cell.

Development of a semi automated dual feed unit to produce FGM coatings using the HVOF thermal spray process

The application of functionally graded materials (FGMs) is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative characteristics result from the gradient from metals to ceramics or non-metallic to metals. The present study investigates an innovative modification of a high velocity oxy-fuel (HVOF) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up with in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously which allows deposition of different layers of coating with changing chemical compositions, without interruption to the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, developed using ANSYS Flotran finite element analysis. In the current research the mixing of different proportions of powders were controlled by a computer using LabVIEW software and hardware, which allowed the control and repeatability of the microstructure when producing functionally graded coatings.

An Investigation of CdZnTe Thin Films for Photovoltaics

Thin film solar cells are widely investigated for terrestrial and space photovoltaic and offer a variety of choices in terms of the device design and fabrication. A variety of substrates, such as flexible or rigid, metal or insulator, can be used for deposition of different layers using different techniques, including physical vapor deposition (PVD), chemical vapor deposition, electrochemical deposition, plasma-based, hybrid, etc. For large-area devices required for realistic applications, thin-film device fabrication becomes complex and requires proper control over the entire process sequence. Detailed investigation of thin-film deposition processes can help in achieving high-efficiency devices over large areas for different solar cells. PVD techniques were extensively used to deposit thin film by using a few targets simultaneously. In this study, single target CdZnTe is used for deposition on glass. Two hundred nm thin films were fabricated. Structural and optical properties of CdZnTe thin films are investigated.

All-printed electronics and its applications: a status report

Mass printing technologies are promising technologies for the production of inexpensive electronics.In recent experiments, we have fabricated an integrated circuit solely by means of fast mass-printing methods without any steps breaking the production continuity. Our results clarified important issues that have to be taken into account when adapting printing technologies to the fabrication of electronics. Compatibility of materials and processes for the deposition of different layers on top of each other, uniformity and quality of layers with respect to electronic requirements as well as resolution and registration turned out to be challenging for the adaptation of printing technologies.In addition, first applications are already available, which rely on simplicity and inexpensive fabrication instead of high integration and high-end performance. Flexible cardboard-keyboards, chipless paper-identification systems as well as simple sensor systems can be regarded as applications that are paving the way for more sophisticated, printed electronics applications.

Thin‐film solar cells: an overview

AbstractThin film solar cells (TFSC) are a promising approach for terrestrial and space photovoltaics and offer a wide variety of choices in terms of the device design and fabrication. A variety of substrates (flexible or rigid, metal or insulator) can be used for deposition of different layers (contact, buffer, absorber, reflector, etc.) using different techniques (PVD, CVD, ECD, plasma‐based, hybrid, etc.). Such versatility allows tailoring and engineering of the layers in order to improve device performance. For large‐area devices required for realistic applications, thin‐film device fabrication becomes complex and requires proper control over the entire process sequence. Proper understanding of thin‐film deposition processes can help in achieving high‐efficiency devices over large areas, as has been demonstrated commercially for different cells. Research and development in new, exotic and simple materials and devices, and innovative, but simple manufacturing processes need to be pursued in a focussed manner. Which cell(s) and which technologies will ultimately succeed commercially continue to be anybody's guess, but it would surely be determined by the simplicity of manufacturability and the cost per reliable watt. Cheap and moderately efficient TFSC are expected to receive a due commercial place under the sun. Copyright © 2004 John Wiley & Sons, Ltd.