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The purpose of this paper is to provide insights for understanding the relationship between rapid manufacturing process for rhenium components in jet nozzle fabrication using electron beam‐physical vapor deposition (EB‐PVD). Specifically, to develop a methodology to characterize and improve this new process through motion planning for maintaining uniformity in the deposition thickness.

This research first identifies several important objectives for the process, and then develops an optimized heuristic method based on a look‐ahead approach to generate motion plans for uniform thickness objective. In this heuristic, the surface of the workpiece is modeled using finite element method and the accumulated thickness of each layer on each element is computed based on its location in the vapor plume using a ray casting algorithm.

Computational experiments show that the proposed algorithm can potentially provide significant improvements in the uniformity of the layers and cost savings in manufacturing compared to prevailing practice, especially for low‐volume production such as aerospace applications.

In this research, net‐shaped jet nozzle has been fabricated using a graphite mandrel. Therefore, the mandrel‐based approach can be limited to producing hollow components.

The proposed method is very generic and thus can be applied for multi‐material manufacturing process identifying the sweet spot of the intersecting vapor plumes.

This research can help the EB‐PVD process for rapid manufacturing which has been considered as financially expensive to be accepted in real practice by providing a relationship of the process‐to‐product transformation through the developed motion planning methods.

To describe the thermal imaging control system used to deposit lines of graphite in a laser chemical vapor deposition (LCVD) system.

A thermal imaging‐based control system is applied to the LCVD process to deposit layered carbon lines of uniform height and width. A 100 W CO₂ laser focused to a 200 μm diameter spot size is used to provide the heat source for the carbon deposition. A high resolution thermal imaging camera is used to monitor and control the average deposition temperature.

Carbon lines are grown with heights of 250 μm and widths of 170 μm consisting of 20 layers. Laser spot temperatures are in excess of 2,170°C, and the total pressure used is 1 atm with a 75 percent methane concentration and the remainder hydrogen. The length of the lines is 3.3 mm, and the scan speed is 5 mm/min. The volumetric deposition rate is 0.648 mm³/h.

The temperature process control resulted in uniform geometry at the center of the lines, but it was not as effective at the ends of the lines where the geometry was more complex.

Introduces a control technique for uniform line deposition for the LCVD process, which represents a core building block for complex geometries. The establishment of basic control algorithms will enable LCVD to realize the potential for rapid prototyping of metals and ceramics with sub‐millimeter feature sizes.

Solid thin films have been deposited on stainless steel 314 (SS 314) substrates in a chemical vapor deposition (CVD) reactor at different flow rates of natural gas mostly methane (CH₄). The purpose of this paper was to investigate experimentally the variation of thin film deposition rate with the variation of gas flow rate.

During experiment, the effect of gap between activation heater and substrate on the deposition rate has also been observed. To do so, a hot filament thermal CVD unit is used. The flow rate of natural gas varies from 0.5 to 2 l/min at normal temperature and pressure and the gap between activation heater and substrate varies from 4 to 6.5 mm.

Results show that deposition rate on SS 314 increases with the increase of gas flow rate. It is also seen that deposition rate increases with the decrease of gap between activation heater and substrate within the observed range. These results are analyzed by dimensional analysis to correlate the deposition rate with gas flow rate, surface roughness and film thickness. In addition, friction coefficient and wear rate of SS 314 sliding against SS 304 under different normal loads are also investigated before and after deposition. The obtained results reveal that the values of friction coefficient and wear rate are lower after deposition than that of before deposition.

In this study, thin film deposition rate on SS 314 was investigated using CVD. The obtained results were analyzed by dimensional analysis to correlate the deposition rate with gas flow rate, surface roughness and film thickness. The friction coefficient and wear rate of SS 314 were also examined before and after deposition.

Oxides in general, by reason of their chemical inertia in oxidising atmospheres, high melting point and high mechanical strength, afford a suitable protective coating at high temperatures. Aluminium oxide in particular also has good thermal shock resistance, good impact resistance at high temperatures, and moderate self‐sealing properties. Hitherto it has been applied to turbojets, space components and rocket jets by flame spraying or arc plasma spraying. Since the characteristic properties of the coating, and hence its efficiency, are directly associated with its degree of structural perfection, the application technique has great importance; in this sense it may be thought, that chemical vapour deposition, allowing the ‘construction’ of the coating atom by atom or molecule by molecule, could produce a material having chemical and physical properties close to the theoretical. For this and other reasons the authors have already had the idea of studying the possible application of this technique for the preparation of a coating of aluminium oxide.

Growth of nickel tip carbon nanorod by means of pulsed plasma chemical vapor deposition (PPCVD) was carried out at different deposition time. Effects of deposition time under the methane plasma on the growth of carbon nanorod were investigated. The nucleation and growth mechanism of nickel tip carbon nanorod were also discussed. Nanoparticles were formed on substrate to introduce more nucleation sites at an elevated deposition time, and the density of nanorod on the surface of the substrate was greatly increased until the proper methane plasma deposition time. The longest nanorods and the highest nanorods density were found after methane plasma treatment of 3 min and 10 min respectively. Nanorod was about 60 nanometers in diameter and about 550 nanometers in length. Nanorods had onion and V-shape with Ni tip.

Describes the key attributes of MEMS technology and existing and future business opportunities. Discusses the various stages in the fabrication of MEMS devices and offers guidance regarding the selection of processing methods for deposition, lithography and etching. Also describes the MEMS‐Exchange program and associated network of fabrication centres.

Laser chemical vapor deposition (LCVD) as a manufacturing process holds the potential to build compositionally and geometrically unique objects. Georgia Tech's LCVD system has been used in the past to create three‐dimensional and laminate structures out of carbon. Recently molybdenum and boron nitride were successfully deposited and upgrades to the system have allowed for higher spatial resolutions and more varied geometric capabilities. Upgrades include the addition of a fourth linear stage and implementation of an argon ion laser. Detailed thermal and fluid modeling have provided more insight as to the important parameters and characteristics of the LCVD process.

A continuous chemical vapor deposition (CVD) method has been used to fabricate pyro-carbon (PyC) coating on continuous silicon carbide (SiC) fibers. The paper aims to evaluate these coated fibers by testing filament tensile and using microstructure characterization.

The continuous SiC fiber-reinforced SiC matrix (SiC/SiC) composite is widely studied in aerospace and nuclear applications. The PyC is the probable option in fusion and fast reactor. However, the conventional fabrication method of PyC coating has some drawbacks influencing performance and efficiency.

The results showed that PyC-coated SiC fibers with continuous CVD method are more straight than conventional ones and residual deformations could not be observed, and these PyC coatings have complete geometry and uniform thickness. In different process conditions, the thickness of PyC coating could control from ∼100 to ∼1,000 nm.

The coated SiC fibers in a lower gas ratio (1:7 to 1:3), lower pressure (500–1,000 Pa) and appropriate winding speed (3 to 5 rpm) have relative high filament tensile strength (∼3.5 to ∼3.9 GPa). And the strength of coated SiC fibers has a negative correlation with the measured thickness of PyC coating. A distinctive growth process was discovered in the continuous CVD method. In a certain range, the quicker growing rate of PyC is obtained in shorter deposition time which means an efficient and quality method could be applied to fabricate coatings.

The purpose of this paper is to enhance the efficiency of the LED by introducing three-step magnesium (Mg) doping profile. Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region). Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region).

Indium gallium nitride (InGaN)–based light-emitting diode (LED) was grown on a 4-inch c-plane patterned sapphire substrate using metal organic chemical vapor deposition. The Cp₂Mg flow rates for the second and third p-GaN layers were set at 50 sccm and 325 sccm, respectively. For the first p-GaN layer, the Cp₂Mg flow rate varied from 150 sccm to 300 sccm to achieve different Mg dopant concentrations.

The full width at half maximum (FWHM) for the GaN (102) plane increases with increasing Cp₂Mg flow rate. FWHM for the sample with 150, 250 and 300 sccm Cp₂Mg flow rates was 233 arcsec, 236 arcsec and 245 arcsec, respectively. This result indicates that the edge and mixed dislocations in the p-GaN layer were increased with increasing Cp₂Mg flow rate. Atomic force microscopy (AFM) results reveal that the sample grown with 300 sccm exhibits the highest surface roughness, followed by 150 sccm and 250 sccm. The surface roughness of these samples is 2.40 nm, 2.12 nm and 2.08 nm, respectively. Simultaneously, the photoluminescence (PL) spectrum of the 250 sccm sample shows the highest band edge intensity over the yellow band ratio compared to that of other samples. The light output power measurements found that the sample with 250 sccm exhibits high output power because of sufficient hole injection toward the active region.

Through this study, the three steps of the Mg profile on the p-GaN layer were proposed to show high-efficiency InGaN-based LED. The optimal Mg concentration was studied on the first p-GaN layer (i.e. layer close to active region) to improve the LED performance by varying the Cp₂Mg flow rate. This finding was in line with the result of PL and AFM results when the samples with 250 sccm have the highest Mg acceptor and good surface quality of the p-GaN layer. It can be deduced that the first p-GaN layer doping has a significant effect on the crystalline quality, surface roughness and light emission properties of the LED epi structure.

This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined.

Materials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials.

HEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA.

The AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages.

It is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.