This study assesses the effect of acid corrosion on the luminescence of YAG:Ce coatings. The feedstock powder is prepared by high-temperature solid phase synthesis and the coatings are deposited by air plasma spraying. Microstructure and phase composition are characterized and the effect of acid immersion duration on luminescent intensity is measured. It is found that the luminescent properties of YAG:Ce 3+ coatings have a tendency to fluctuate with immersion time, which appears to be related to phase composition.

A nanostructured WC-CoCr coating was fabricated by HVOF spraying using a new type of WC-CoCr powder in which the CoCr exists in the form of a metallic compound. The CoCr powder constituent was prepared by induction melting and mechanical milling. It was then combined with a WC-Co composite nanopowder and the mixture was agglomerated by spray drying and heat treating. The powders and coatings produced were characterized by means of XRD, EDS, and BSE analysis, nanoindentation testing, and potentiodynamic polarization studies. The results show that the presence of the intermetallic CoCr compound makes nanostructured WC-CoCr coatings harder and much more corrosion resistant than conventional WC-Co-Cr coatings in which Cr exists as an unalloyed metal.

This study assesses the microstructure and mechanical properties of tungsten boride (WB) powder and cemented carbide coatings with WB additions. HVOF-sprayed layers produced from 60WC-30WB-10Co composite powders are compared with conventional 88WC-22Co and 86WC-10Co-4Cr coatings based on phase composition, hardness, wear resistance, and wear surface structure. The results indicate that Co reacts with WB during spraying, forming ternary phases (WCoB, W 2 CoB 2 ) that increase hardness as well as sliding wear resistance.

Nanostructured WC-CoCr powder was prepared and deposited on carbon steel substrates by HVOF spraying. The coatings obtained were characterized based on phase constitution, elemental distribution, and microstructure as well as corrosion and sliding wear behaviors. X-ray diffraction was used to identify the main phase constituents and EDS analysis revealed the distribution of Co and Cr in the coating. The mechanisms involved in the formation of microstructure are discussed along with the effects of Cr on coating performance.

In this study, FeCrB coatings are deposited by wire arc spraying using powder cored wires to investigate the factors that affect thermal conductivity. Experimental results show that increasing boron content in the wires reduces oxide content in the coatings, which increases thermal conductivity. Annealing also increases thermal conductivity, which can be explained by grain growth and a reduction in porosity.

To achieve the necessary creep-rupture lifetimes at the temperatures and pressures associated with advanced ultrasupercritical (A-USC) steam conditions (100,000 h at 100 MPa and 760°C), precipitation-strengthened nickel-based alloys are required for the superheater and reheater tubing in A-USC boilers. Two alloys were considered to have potential for this application: Inconel 740 and Haynes 282 alloy. In support of this application, creep-rupture testing of several heats of Inconel 740 was conducted over a range of temperatures and stresses to develop confidence in qualitatively predicting creep lifetimes under conditions relevant to A-USC steam conditions, with the longest rupture times exceeding 30,000 h. For comparison, the creep-rupture behavior of Haynes 282 alloy was mapped as a function of temperature and stress, but with a significantly smaller dataset. Only a small difference in creep-rupture results between Inconel 740 and Inconel 740H was found although the latter alloy showed significantly greater resistance to η phase formation during testing. Little effect of prior aging treatments (for setting the γ′ precipitate structure) on creep-rupture behavior was observed. Results from a modified power law analysis showed that, while both Inconel 740 and Haynes 282 are projected to meet the A-USC lifetime requirements, the latter offered the potential for better long-term creep resistance.

Molybdenum disilicide (MoSi 2 ) has been applied as protective coating material on various substrates fabricated by different methods due to its good oxidation resistance at elevated temperature, relatively low density and coefficient of thermal expansion and high thermal conductivity. In this work, MoSi 2 coatings were fabricated by low pressure plasma spraying technology (LPPS). Their morphology, composition and microstructure characteristics were intensively investigated by SEM, XRD, EDS and TEM. The oxidation behaviors of MoSi 2 coatings were also explored. The results showed that the MoSi 2 coating was compact with porosity less than 5%. Its microstructure exhibited typical lamellar character. The MoSi 2 coating was made up of grains with irregular shapes and different sizes of 0.1-0.2 µm. It was mainly composed of tetragonal and hexagonal MoSi 2 phases. A small amount of tetragonal Mo 5 Si 3 phase formed and randomly distributed in the matrix of MoSi 2 . The MoSi 2 coating exhibited excellent oxidation-resistant behavior at 1773K, which resulted from the continuous dense glassy SiO 2 film formed on its surface.

Bead blasting and thermal spray coatings are often applied on process kits used in vacuum deposition chambers to improve adhesion between kit surfaces and deposited films. This study shows that in order to maximize chamber service time and reduce processing defects, thermal expansion mismatches must be considered between chamber components, sprayed coatings, and vacuum deposited films. When a titanium sheet coated with arc sprayed aluminum was placed in a titanium nitride deposition chamber, significant particle spiking was observed. However, during the same period of chamber service time, particle performance was stable for titanium coated with arc sprayed molybdenum. It should be noted that the thermal expansion coefficients of Ti and Mo are much closer than those of Ti and Al. By further optimizing the cohesion strength of the arc-sprayed Mo coating, even lower particle counts have been achieved, corresponding to fewer processing defects and prolonged chamber kit lifetime.

A failure incurred in the front-end is typically a bottleneck to production due the need for physical failure analysis (PFA). Often the challenge is to perform timely localization of the front-end defect, or finding the exact physical defect for process improvement. Many process parameters affect the device behaviour and cause the front-end defect. Simply, the failures are of two types: high-resistance and leakage. A leakage mode defect is the most difficult to inspect. Although conductive atomic force microscopy and six probes nano-probing are popular tools for front-end failure inspection, some specific defects still need more effort. The electrical phenomenon and analysis of a crystalline defect will be demonstrated in this paper. The details will be discussed below.

In the recent decade, considerable numerical models have been built up to simulate the thermal spray process. However, much less work has focused on the prediction of thermo-physical properties of the thermal spray coating, in particular the heat insulation properties. In this paper, a microstructure integrated finite element model is developed to investigate the heat insulation behavior of the thermal spray coating. A two-layer model is used to calculate thermal conductivity of the coating, where one layer stands for the coating by a unit cell, while another one for a standard material with known thermal conductivity. In the proposed unit cell model, pores and unmelted particles are assumed spherical and randomly distributed, and the interface between the coating and the unmelted particles is perfectly debonding. Based on the predictions, the effect of the pores, unmelted particles, cracks and their respective distributions on the heat insulation behavior of the coating has been further discussed in the paper.

FeAl Intermetallic compounds have excellent wear resistance and high temperature oxidation resistances. The low temperature brittleness makes intermetallic compound materials more suitable to be applied in the form of coating to protect materials from high temperature oxidation and wear. In the present study, a iron/aluminum composite coating was produced by cold spraying of iron and aluminum powder mixtures and then was annealed at different temperatures to aim at forming an iron aluminide intermetallic based coating. The deposition behavior of iron and aluminum powder mixtures and microstructural characteristics of the as-sprayed deposit were examined by scanning electron microscopy (SEM). The kinetics of the phase transformation of the as-sprayed iron/aluminum composite deposit to iron aluminide was characterized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that after heat treatment at a temperature of 600°C, intermediate phase Al 5 Fe 2 coexisted in the deposit with remaining Fe and Al. With increasing heat treatment temperature to 900°C, the deposits consisted of mainly FeAl phase and a trace of remaining Fe phase.

Ti and Ti alloys can be applied to the steels as a protective coating in view of its excellent resistance to corrosive environment. Cold spraying as a new surface engineering technique has potential advantages in Ti coating manufacturing in comparison with conventional thermal spraying techniques. Ti coatings were prepared on a carbon steel substrate by cold spraying via controlling the process condition variables concluding carrying gas, temperature and pressure. The microstructure of coatings was observed by SEM. Potentiodynamic polarization experiments were performed to understand the corrosion behavior of the coatings. The SEM examination showed that the coatings become more compact with increase of molecular weight, pressure and temperature of carrier gas. Potentiodynamic polarization technique was used to measure the corrosion and electrochemical property of coatings deposited under different process conditions and surface conditions. The polarization curves indicated that the coatings which had lower porosity had lower corrosion current. The polishing treatment peeled the rough outer layer including the small pores as well as decreasing of the actual surface area of the coating, leading to the considerable improvement of corrosion resistance.

In this paper, submicron α-Fe/nylon-12 microwave absorbing composite coatings were deposited by a Low Temperature High Velocity Air Fuel (LTHVAF) spraying technique. The microstructure and the electromagnetic parameters of coatings and powders were tested. The coatings are dense and have low porosity. The microwave reflectivity coefficient of the coatings was calculated with permeability and permittivity of the powders. It shows that there is a relationship between the mass fraction of composite powders and microwave absorption ability of coatings. At the threshold value, the composite coatings can absorb microwave strongly. When the coatings thickness increases, the minimal reflectivity coefficient moves to the low microwave frequency. There exists an appropriate coatings thickness in order to optimize the absorption of the microwave energy. The mass fraction and the thickness can affect the performance of composite absorber coatings.

Optical beam induced resistance change (OBIRCH) is one popular technique for isolating electrical shorts in process development test structures for 130nm and 110nm device technologies. However, OBIRCH inspection on 90nm technology is not always successful: since the OBIRCH signals of samples are very weak, or even comparable to noise. To overcome this, two alternative and complementary methods for isolating the failure have been developed. The first method is to calculate the coarse position of the defect directly from electrical resistance measurements. The second method is to enhance the OBIRCH signal using FIB circuit modification within the test structure. These methods can help locate defect at this structure by using electrical analysis only or enhancing the OBIRCH signal. The first method is an easy and quick method for short failure isolation, while the second can exactly locate the position of failure if the first method does not reveal a surface defect.

Aside from its importance as a design parameter for thermal barrier coatings, measuring thermal conductivity of thermal sprayed coatings itself provides a unique method to critically characterize the nature, quantity and anisotropy of the defect morphologies in these splat-based coatings. In this paper, we present a systematic assessment of thermal conductivity of wide range of thermal sprayed coatings using the flash diffusivity technique. For the case of plasma sprayed yttria-stabilized zirconia (YSZ), coatings obtained from wide ranging initial powder morphologies as well as those fabricated under different particle states were characterized. Both in-plane and through-thickness properties were obtained. Other material systems that were considered include: metallic alloys, semiconductors and other oxides of interests. Issues such as reproducibility and reliability in measurements were also considered and assessed. Finally, working in collaboration with the Oak Ridge National Laboratory (ORNL) for alternate approaches to characterization of thermal conductivity as well as high temperature measurements was performed.

Modern semiconductor devices are continuing to be scaled down and the complexity of the processes involved in producing the devices keeps increasing, in conjunction with this, sample preparation and analysis are increasingly important for accurately determining the sources of defects and failure mechanisms in terms of process integration. This paper discusses ways to characterize integration-driven defects using deprocessing techniques and cross-section imaging to obtain 3-D views of such defects. As an example a single-via test structure is evaluated. The article focuses on the techniques used to deprocess the single-via structure using a combination of RIE, FIB, and wet etching to expose the single via while maintaining the integrity of the structure. The resulting 3-D view of the structure and associated defect allowed for improved understanding of the defect and its origin. This understanding enabled process optimization to minimize such defect formation.

With the advancement in technology and lower operating voltage, new standards have evolved in circuit layout and design. Some of these new standards have increased the difficulties of the physical failure analysis process, especially on the front-end. The phenomenon described in this paper is the unusual voltage contrast (VC) and conductive atomic force microscope (C-AFM) curve on a non-isolated active region. The model and mechanism are demonstrated for front-end failure analysis. Based on this, the solution for analysis is investigated.

LTHVOF(Low Temperature High Velocity Oxygen-Fuel) spray is developed by injecting nitrogen into the gun chamber. The flame temperature can be adjusted between 400K to 800K after cooling, which is identical to cold spray. Copper coatings were sprayed by LTHVOF. SEM photos show that the coatings are dense with a lamellar structure. X-ray diffraction pattern shows that there is no oxide in the coatings. LTHVOF may be another choice for coating production of low melt point metal and nanometer size materials.

Based on the HVO-AF (High Velocity Oxygen-Air Fuel) thermal spray system, the Low Temperature High Velocity Air Fuel Spray was realized by additional liquid feed stocks. In this paper, the microstructure and characteristics of composite coatings sprayed by this spray technology were analyzed. Composite powders were composed at three mass fractions, Fe, 5mass%Fe -polymer, 15mass%Fe-polymer. In the experiments, the coatings properties were tested. The results indicated that all the coatings microstructure is dense and low porosity; metal particles were dispersed with polymer in the coatings. There were little oxide phase in the coatings. The coatings were closely combined with substrate, the reflectance coefficient of 5mass%Fe-polymer composite coatings is better than others, the reflectance coefficient curve of the coatings is 2~6dB at 2~18GHz.

A high efficiency supersonic plasma spray system (HEPJet) was successfully developed with a maximum power of 80 kW and a maximum working gas flow of 6 m 3 /h. It can be used to spray metallic, carbide and oxide powders. The supersonic plasma spraying gun has a single-anode, internal feeding structure. The development of 80 kW inverse power supply with 20 kHz PWM IGBT circuit solved the problems of high output voltage, high output current and strong interference of high frequency. The production cost of this system is only equivalent to that of ordinary plasma systems. The average velocity of Al 2 O 3 particles in the plasma jet measured with a Oseir Spray Watch system reached 740m/s, and the coatings show high quality, good bonding strength and low porosity. The Co/WC coatings deposited by HEP Jet avoided the degradation from WC to W2C which should be attributed to the strong adjustability of the system for jet temperature and jet velocity.