High-pressure Deposition Research Articles

THE EFFECT OF THERMAL CYCLING ON DEPOSITION IN AN IMPINGEMENT/EFFUSION COOLING GEOMETRY

Abstract Experiments were conducted in a high-pressure deposition facility to study the effect of engine cycling on the successive buildup of deposits as aircraft shut down and power up. The test facility simulates the pressure and temperature environment of a combustor liner cooling circuit. The coolant flow temperature reaches 894K (1150 °F) and discharges into a 17atm (250 psi) cavity pressure at a nominal pressure ratio of 1.027. AFRL05 test dust with a 0-10micron size distribution is added to the coolant . The cooling circuit consists of a double-walled impingement/effusion cooling plate with nominal hole sizes on the order of 0.5mm. To simulate cycling, the facility is brought up to the desired operating conditions where the first batch of dust is delivered (2-8g). The facility is then ramped down to ambient conditions. Following a “dwell” period of approximately 24 hours, another batch of dust is delivered once the facility is brought back up to the desired operating condition. Test data were acquired for one, two, and four cycles with different dust mass delivered. Values such as discharge coefficient, pressure ratio, Reynolds Number, and temperature are used to evaluate the effects of dust deposition on the impingement/effusion plate setup. Dust capture efficiency is shown to be insensitive to cycling whereas flow blockage is negatively impacted by increased number of cycles for the same total mass delivered. The sloughing of deposit structures during cooling circuit cool down is postulated to be responsible for the observed behavior.

Influence of deposition pressure on microstructure, mechanical and electrical properties of niobium thin films

Niobium (Nb) thin films were deposited on a Si substrate using magnetron sputtering system by varying the deposition pressure. The effect of deposition pressure on the microstructure, residual stresses, and electrical properties was investigated by systematically varying the deposition pressure from 0.15 to 0.60 Pa. The Nb thin films were characterized using hard x-ray reflectivity, grazing incidence x-ray diffraction, four point probe method, and atomic force microscopy. The films grown at lower deposition pressures had smooth surfaces and more compact structures, which are advantageous for lowering electrical resistance but had higher compressive stress. On the other hand, the films grown at higher deposition pressures had columnar type growth with less dense structures, which leads to increase in electrical resistance. However the nature of stresses transform from compressive to tensile. Hard X-ray reflectivity performed on Nb films provides direct insight into the growth and the microstructure which were correlated with the mechanical and electrical properties.

The Stability of Straightened Ta Filament During Chemical Vapor Deposition of Diamond Film

Maintaining the geometrical stability of hot filament is a challenge in chemical vapor deposition (CVD) over a larger area since deformation varies the distance between the filament and the substrate and, consequently, destroys the uniformity of diamond deposition. Herein, Ta filament is straightened with a tensile stress ranging from 4.40 to 11 MPa to suppress deformation, and the stability during the CVD process of diamond film is evaluated. Scanning electron microscopy and energy dispersive X‐ray are further utilized to investigate the morphological and structural evolutions of Ta filament. Results show that straightened Ta filament maintains geometrical stability without any visible deformation or breakage and uniform deposition of diamond film is obtained through Ta filament undergone a transformation from Ta to Ta2C and then to TaC. At high deposition pressure (7 kPa) or a low concentration of methane (1%), the straightened Ta filament goes through a moderate transformation, which implies the cracks caused by rough transformation can be avoided, thus prolonging the lifetime of straightened Ta filament. These works provide significant guidelines for the large‐scale manufacture of diamond deposition.

Nanodiamonds: A Cutting-Edge Approach to Enhancing Biomedical Therapies and Diagnostics in Biosensing.

Nanodiamonds (NDs) have garnered attention in the field of nanomedicine due to their unique properties. This review offers a comprehensive overview of NDs synthesis methods, properties, and their uses in biomedical applications. Various synthesis techniques, such as detonation, high-pressure, high-temperature, and chemical vapor deposition, offer distinct advantages in tailoring NDs' size, shape, and surface properties. Surface modification methods further enhance NDs' biocompatibility and enable the attachment of bioactive molecules, expanding their applicability in biological systems. NDs serve as promising nanocarriers for drug delivery, showcasing biocompatibility and the ability to encapsulate therapeutic agents for targeted delivery. Additionally, NDs demonstrate potential in cancer treatment through hyperthermic therapy and vaccine enhancement for improved immune responses. Functionalization of NDs facilitates their utilization in biosensors for sensitive biomolecule detection, aiding in precise diagnostics and rapid detection of infectious diseases. This review underscores the multifaceted role of NDs in advancing biomedical applications. By synthesizing NDs through various methods and modifying their surfaces, researchers can tailor their properties for specific biomedical needs. The ability of NDs to serve as efficient drug delivery vehicles holds promise for targeted therapy, while their applications in hyperthermic therapy and vaccine enhancement offer innovative approaches to cancer treatment and immunization. Furthermore, the integration of NDs into biosensors enhances diagnostic capabilities, enabling rapid and sensitive detection of biomolecules and infectious diseases. Overall, the diverse functionalities of NDs underscore their potential as valuable tools in nanomedicine, paving the way for advancements in healthcare and biotechnology.

Simulation of Hydrate Particles Aggregation and Deposition in Gas-Dominated Flow

Summary Owing to low-temperature and high-pressure production environments, hydrate generation, accumulation, and deposition are prone to occur in deepwater oil and gas production wells and transportation pipelines, leading to pipeline blockage and threatening the safety of oil and gas production. To explore the aggregation mechanism and deposition law of hydrate particles in the main gas diversion pipeline, this study considered the adhesion effect of hydrate particles and established a hydrate particle aggregation and deposition model based on theory and experiments. The coupled computational fluid dynamics-discrete element method (CFD-DEM) is used in the simulation calculation. The simulation results were compared with the relevant experimental results, and maximum and average errors of 9.48% and 4.56% were observed, respectively. It was found that the main factor affecting the aggregation of hydrates is the adhesion between particles. As the subcooling temperature increased, the aggregation and adhesion of the hydrate particles increased to varying degrees. The tangential adhesion force between the hydrate aggregate particles was significantly greater than the normal adhesion force, and the adhesion force between the particles gradually increased from the surface to the interior of the aggregates. The coordination number of the hydrate particles can quantitatively characterize the degree of aggregation and is affected by many factors, such as adhesion. By studying the particle coordination number, the evolution of hydrate accumulation and deposition under different conditions can be summarized. Based on the simulation results, the mathematical relationship between different dimensionless numbers and hydrate deposition ratio (HDR) was calculated, and an expression that can predict the HDR was obtained, with an average relative error of 10.155%. This study provides a theoretical basis for predicting the aggregation and deposition of hydrate particles in gas-dominated systems and a reference for the development of hydrate prevention and control plans.

Understanding the tribo-corrosion mechanisms of friction stir processed steel deposited by high-pressure deposition additive manufacturing process

Understanding the tribo-corrosion mechanisms of friction stir processed steel deposited by high-pressure deposition additive manufacturing process

Opto-electrical properties of amorphous silicon carbide thin films adjustably prepared by magnetron sputtering at room temperature

The application of silicon carbide (SiC) thin films is extensive, and they can be prepared at room temperature using magnetron sputtering. In this study, a wide range of deposition pressures (0.5–5.5 Pa) was utilized for the sputtering of amorphous SiC thin films. With an increase in deposition pressure, not only does the oxygen content increase, but also the carbon phase changes. The oxygen ratio increases from approximately 6.8% to 20.0% as the deposition pressure rises from 0.5 Pa to 1.5 Pa, and it gradually increases further to around 25.0% as the deposition pressure rises to 5.5 Pa. When the deposition pressure is>3.0 Pa, the amorphous carbon phase transforms into diamond-like and graphite-like carbons. As a result, the optical bandgap varies from about 1.7 eV to 3.6 eV with the change in deposition pressure, while the conductivity reduces from 2.5 × 10-4 S/cm to 1.3 × 10-8 S/cm. This study provides insights into the significant impact of high deposition pressure on the material properties of sputtered SiC thin films. It demonstrates that the chemical bonding, composition, and opto-electrical properties of SiC thin films can be effectively tailored for application in optoelectronic devices.

Effect of argon sputtering pressure on the electrochemical performance of LiFePO4 cathode

The development of a novel small-scale electrical power source technology is essential in the design of microelectronic devices. In this sense, this study presents the optimization of the sputtering deposition parameters to grow a LiFePO4 cathode, a candidate material for the development of solid-state lithium batteries. Specifically, it was evaluated the effect of argon deposition pressure on the electrochemical properties of LiFePO4 cathode. By combining X-ray photoelectron spectroscopy with electrochemical characterization methods, it was revealed that argon deposition pressure modulated the degree of the re-sputtering effects. In addition, it was found that high argon deposition pressure leads to the growth of LiFePO4 films with oxygen and phosphor deficiency. The absence of these atoms caused the decrease in the LiFePO4 electrochemical activity. Conversely, deposition parameters based on low argon sputtering pressure significantly reduced the degree of the re-sputtering effects, which in turn favored the growth of stoichiometric LiFePO4 films with an enhanced electrochemical activity.

Wear and corrosion characterization of single and multilayered nanocrystalline tantalum coatings on biomedical grade CoCrMo alloy

Osteolysis caused by the worn-off particles of polyethylene (PE), and corrosion of CoCrMo head have been two major concerns in total hip replacement as they lead to its early failure. Here we report on the development of a Ta multilayered coating to improve the corrosion resistance of CoCrMo and minimize the wear rate of PE. Deposition of single-layered and multilayered Ta coatings was carried out at ambient temperature utilizingmagnetron sputtering with deposition pressure ranging from 0.3 Pa to 1.9 Pa. The hardness and Young's modulus of the Ta coatings ranged from 8 to 21 GPa and from 179 to 288 GPa, respectively. Excellent adhesion was observed on the Ta coatings deposited at a high deposition pressure. The PE wear rate was 4% lower when sliding against the Ta multilayered coating than with the uncoated sample. Furthermore, the Ta multilayered displayed a 61% greater corrosion resistance than the uncoated CoCrMo alloy. The results indicate that Ta coatings have great potential for artificial joint applications.

Magnetic properties in soft (CoFeB)/hard (Co) bilayers deposited under different Ar gas pressure

We have studied the effect of deposition pressure on the magnetization reversal, domains, anisotropy and Gilbert damping constant in the ferromagnetic (CoFeB and Co) single and bilayer samples. Hysteresis measured by magneto-optic Kerr microscopy for the single layer films prepared at higher deposition pressure indicate no change of loop shape i.e. isotropic behaviour. An enhancement of anisotropy has been observed in the bilayer samples than the single layer samples prepared at a particular deposition condition. However, increasing the deposition pressure to 50 sccm for the bilayer samples, anisotropy gets reduced. For single layer Co film deposited at 10 sccm exhibits branch and patch like domains for different angle between the easy axis and the external magnetic field. However, the Co film deposited at 50 sccm exhibits ripple like domains. In the case of single layer CoFeB, branch and patch like domains are observed deposited at 10 sccm. Patch like domains are found for the CoFeB films deposited at 50 sccm. Pinned labyrinth and ripple kind of magnetic domains along with the big branch domains are found in the bilayer samples. The pinned domains may be due to the interfacial exchange coupling. Similar values of damping constants have been observed for different thin films prepared at different deposition pressure.

Carrier mobility in field effect transistors based on copper-phthalocyanine thin films with different phase structure

Using annealing procedure at different temperatures after deposition at room temperature we obtained copper- phthalocyanine (CuPc) thin films with a — and p —phase structure. A phase structure of thin films was controlled by X-ray diffraction method, morphology was controlled by SEM. The field effect transistors was fabricated by high vacuum deposition of CuPc thin film (thickhess of 100 nm) on Si02 substrate which acting as gate contact. Gold drain and source contacts deposited on the top of active layer of FET. From measured current voltage measurements calculated mobility and concentration of charge carriers in FET. These parameters depend on phase structure of CuPc thin film, and characteristics of our FET are comparable with values of other authors.
 CuPc is commercially available macro cyclic metal complex that can be easily obtained in large quantity and high purity. Together with other phthalocyanine derivatives, the chemically and thermally stable CuPc has wide applications in dye processing, spectral sensitization, chemical sensors, and optical data storage [3-4]. The semiconducting behavior of metal phthalocyanines was first observed in 1948 and they have since attracted great interest in advancement of protptype organic semiconductors. Among the metal substituted phthalocyanines CuPc has been found superior properties [5-7], such as phenomena of field dependent and wavelength-dependent efficiency in an organic static induction transistors, and stabilizing role of CuPc layer on a highly stable organic electroluminescent device based on thin film Alq, and indicated a very weak interaction between CuPc and Au at the interface.
 In general, phthalocyanine materials can exist in several crystalline polymorphs, including a-, p -, x-and y - structure, and the most well known are the thermally metastable a- and p - [8-10], Phthalocyanine films deposited at room temperature usually consist of a-phase crystallites (at sublimation pressure of less than 10 Pa). At higher deposition pressures or at substrate temperature above 210°C, the p -phase directly obtained [11], Although it is well known that a-phase crystallites undergo a phase transformation into P -phase by treatment in various organic suspension media [12,13] or during annealing at higher temperatures [14,15], only some authors describe the nature of the a—>p phase transformation of copper phthalocyanine thin films with a thickness of less than 100 nm [8,14-15].

Corrosion Behavior of Cold Sprayed Aluminum Alloys 2024 and 7075 in an Immersed Seawater Environment

This paper describes the polarization and basic pitting behavior of 2024 and 7075 aluminum alloys produced by high-pressure cold-spray deposition. While cold spray is showing great promise as a solid-state repair approach for metallic structures, the corrosion behavior of these materials still needs investigation, particularly in describing the potential galvanic interactions with the repaired substrate. Potentiodynamic testing was performed on cold-sprayed (CS) aluminum alloys 2024 and 7075, and corresponding wrought AA2024-T3 and AA7075-T651 alloys for comparison. Testing used ASTM D1141 artificial seawater for potentiodynamic polarization, following the MIL-STD 889C standard for testing with consistent results. Pitting was investigated using 120 h immersion tests, with subsequent photography, scanning electron microscopy imaging, and energy-dispersive x-ray spectroscopy analysis of the surface. CS-2024 was found to be more active and reactive than wrought, with enhanced anodic kinetics; it experienced more aggressive pitting than the AA2024-T3 during the immersion test. CS-7075 was found to be less active and more reactive than wrought, with enhanced cathodic kinetics; the CS-7075 demonstrated reduced pitting compared to the AA7075-T651. Possible causes for these differences are discussed, including material homogeneity, CS powder intermetallics, and spray parameters. Overall, CS-2024 and CS-7075 should have little galvanic interaction with their corresponding substrates.

Novel class of nanostructured metallic glass films with superior and tunable mechanical properties

A novel class of nanostructured Zr50Cu50 (%at.) metallic glass films with superior and tunable mechanical properties is produced by pulsed laser deposition. The process can be controlled to synthetize a wide range of film microstructures including dense fully amorphous, amorphous embedded with nanocrystals and amorphous nano-granular. A unique dense self-assembled nano-laminated atomic arrangement characterized by alternating Cu-rich and Zr/O-rich nanolayers with different local chemical enrichment and amorphous or amorphous-crystalline composite nanostructure has been discovered, while significant in-plane clustering is reported for films synthetized at high deposition pressures. This unique nanoarchitecture is at the basis of superior mechanical properties including large hardness and elastic modulus up to 10 and 140 GPa, respectively and outstanding total elongation to failure (>9%), leading to excellent strength/ductility balance, which can be tuned by playing with the film architecture. These results pave the way to the synthesis of novel class of engineered nanostructured metallic glass films with high structural performances attractive for a number of applications in microelectronics and coating industry.

Diamond with nitrogen: states, control, and applications

The burgeoning multi-field applications of diamond concurrently bring up a foremost consideration associated with nitrogen. Ubiquitous nitrogen in both natural and artificial diamond in most cases as disruptive impurity is undesirable for diamond material properties, eg deterioration in electrical performance. However, the feat of this most common element-nitrogen, can change diamond growth evolution, endow diamond fancy colors and even give quantum technology a solid boost. This perspective reviews the understanding and progress of nitrogen in diamond including natural occurring gemstones and their synthetic counterparts formed by high temperature high pressure (HPHT) and chemical vapor deposition (CVD) methods. The review paper covers a variety of topics ranging from the basis of physical state of nitrogen and its related defects as well as the resulting effects in diamond (including nitrogen termination on diamond surface), to precise control of nitrogen incorporation associated with selective post-treatments and finally to the practical utilization. Among the multitudinous potential nitrogen related centers, the nitrogen-vacancy (NV) defects in diamond have attracted particular interest and are still ceaselessly drawing extensive attentions for quantum frontiers advance.

Challenges in Solvent-Free Methods for Manufacturing Electrodes and Electrolytes for Lithium-Based Batteries.

With the ever-growing energy storage notably due to the electric vehicle market expansion and stationary applications, one of the challenges of lithium batteries lies in the cost and environmental impacts of their manufacture. The main process employed is the solvent-casting method, based on a slurry casted onto a current collector. The disadvantages of this technique include the use of toxic and costly solvents as well as significant quantity of energy required for solvent evaporation and recycling. A solvent-free manufacturing method would represent significant progress in the development of cost-effective and environmentally friendly lithium-ion and lithium metal batteries. This review provides an overview of solvent-free processes used to make solid polymer electrolytes and composite electrodes. Two methods can be described: heat-based (hot-pressing, melt processing, dissolution into melted polymer, the incorporation of melted polymer into particles) and spray-based (electrospray deposition or high-pressure deposition). Heat-based processes are used for solid electrolyte and electrode manufacturing, while spray-based processes are only used for electrode processing. Amongst these techniques, hot-pressing and melt processing were revealed to be the most used alternatives for both polymer-based electrolytes and electrodes. These two techniques are versatile and can be used in the processing of fillers with a wide range of morphologies and loadings.

Discharge model and plasma characteristics of high-power pulsed magnetron sputtering titanium target

<sec>High-power pulsed magnetron sputtering has become a popular research tool in surface technology industry because it can prepare the films with excellent surface quality. The plasma density and metal ionization rate are the key factors affecting the quality of the film deposited by high-power pulsed magnetron sputtering. The parameters of high-power pulsed magnetron sputtering (such as applied voltage, pulse width, deposition pressure and peak current) affect the plasma density and metal ionization rate. In this paper, in order to more easily understand the plasma densities and metal ionization rates at the different process parameters, the plasma densities and ionization rates are calculated numerically. An equivalent circuit model established by MATLAB/Simulink software is used to obtain the discharge current curve of high-power pulsed magnetron sputtering titanium (Ti) target. The plasma density near the plasma sheath is calculated by the sheath resistance in the equivalent circuit model. The ionization rate of Ti is calculated by using the semi-cylinder global model theory combined with the discharge current simulated by equivalent circuit model. It is found that under the different high power pulse sputtering voltages, pulse widths and different deposition pressures, the discharge modes are of gas discharge and metal ion discharge, and the gas discharge interacts with metal ion discharge. The equivalent circuit model is produced by the main discharge mode, and the equivalent circuit model composed of capacitor, inductor and resistors in series and in parallel can be used to simulate the discharge current of Ti target. The result shows that the simulated discharge current is accurate in the rising edge and peak value in comparison with experimental data. The value of electron component in the model is related to the saturation ion current.</sec><sec>According to the sheath resistance in the model, the average plasma density in the vacuum chamber increases with increasing sputtering voltage, pulse width and deposition pressure. And the plasma density in the vacuum chamber lies in a range of (2–9) × 10<sup>17</sup> m<sup>–3</sup>. The particle equilibrium equation is established by using the semi-cylinder global model theory. The electron temperature (5 eV) and discharge current are used as boundary conditions to calculate the ionization rate of Ti. The value of the ionization rate of Ti is in a range of 31%–38% at different deposition pressures, and the ionization rate of Ti increases with the increase of deposition pressure.</sec>

Bonding structure and etching characteristics of amorphous carbon for a hardmask deposited by DC sputtering

An amorphous carbon hardmask was fabricated by DC sputtering to evaluate the etching characteristics for semiconductor microstructure patterning. The bonding structure of the carbon films deposited by sputtering was modified by the DC sputtering conditions and the deposition pressure. In the case of a low-pressure deposition process, an sp3-bonding-rich amorphous carbon film was fabricated and had excellent etching resistance. On the other hand, during the high-pressure deposition process, an sp2-bonding-rich amorphous carbon film was fabricated and had poor etching resistance. To understand the degradation process of the carbon hardmask induced by the penetration of fluorine ions into the film during dry etching, the phenomenon of fluorine penetration into the film and the interaction between fluorine and the carbon bonds were studied by density functional theory (DFT). Through the DFT calculations, it is unveiled that the energy barrier for the migration of a fluorine atom through the sp3 bonding path is much larger than that of a fluorine atom through the sp2 bonding path in amorphous carbon.

Study on the performance of titanium film as a diffusion barrier layer for CIGS solar-cell application on stainless-steel substrates

Abstract In this paper, pure titanium (Ti) thin films deposited by radio frequency sputtering were used as a diffusion barrier layer in a flexible copper indium gallium selenium (CIGS) solar cell on a stainless-steel foil and characterized by X-ray diffraction, scanning electron microscopy and second ion mass spectroscopy measurement methods. The influences of the magnetron sputtering pressure on the surface morphology and preferred crystal orientation of Ti films are discussed. It was found that the Ti film showed a (001) preferred orientation and smooth surface topography at lower deposition pressure, while (002) preferred orientation and relatively rough surface topography at higher deposition pressure. In addition, Ti films made with different process pressures were deposited as the barriers and the second ion mass spectroscopy results indicated that a Ti film with the thickness of 200 nm was able to effectively block Fe and Cr diffusion from the stainless-steel foil into the CIGS absorber across the molybdenum back contact. The Ti barrier significantly improved the conversion efficiency of the CIGS solar cell.

Synthesis of nanopowders in a PECVD reactor from organosilicon precursor

In previous work, nanopowders have been obtained during the deposition of thin layers from Hexamethyldisiloxane (HMDSO) using low frequency plasma. The aim of this work is the study of the growth process of these nanopowders in plasma discharge and in deposited films. The plasma discharge was generated from HMDSO precursor in low frequency reactor; optical emission spectroscopy (OES) and scanning electron microscopy (SEM) have been used to investigate the effect of the deposition parameters on the nanopowders growth in the plasma discharge and in the deposited thin layers respectively. For high deposition pressure, OES reveals the presence of SiH (situated at 414 nm), OH (situated at 309 nm), CHO (situated at: 324.3, 351.5 nm) species and some additional emission peaks of CO (situated at: 540.9, 566.6, 578, 646,6 nm). The intensities evolution of these species have been investigated during the discharge plasma and the presence of some of them may be the result from the reaction of the nanoparticles of the deposited powders with the plasma species. Nanoparticles agglomerations have been revealed by SEM observations and their aspect correlated with optical emission spectroscopy measurements.

Demonstration of SiO2/SiC based protective coating for dental ceramic prostheses.

SiO2/SiC coatings were deposited onto ceramics disks using plasma enhanced chemical vapor deposition. The effects of deposition pressure and gas-flow ratio on the refractive index, extinction coefficient, and SiC composition were studied. For the highest studied SiH4 to CH4 gas-flow ratio of 1.5, the refractive index increased by 17% from 2.53 (at the wavelength of 845 nm) to 2.96 (at the wavelength of 400 nm). For the lowest studied SiH4 to CH4 gas-flow ratio of 0.5, the refractive index only increased by 4% from 2.11 (at the wavelength of 845 nm) to 2.20 (at the wavelength of 400 nm). At higher deposition pressures, the variation in refractive index of the SiC coatings was significantly lower showing a slight increase from 1.93 (at a wavelength of 845 nm) to 1.96 at a wavelength of 400 nm. Except for the case of a low SiH4 to CH4 gas-flow ratio of 0.5, for light with wavelengths ≤ 650 nm, the extinction coefficient of the SiC coatings increased significantly. Light with a wavelength > 650 nm had an extinction coefficient near 0 in all cases. After annealing the sample at 400°C for 4 hours, hydrogen-related bonds broke and the stress of the film was reduced from -245 to -71 MPa. By utilizing different thicknesses of SiC, the full standard dental shade guide was matched with the ΔE of each coated disk being less than 3.3 compared to the shade guide.