Mechanical,hygroscopic, and thermal properties of metal particle and metal evaporated tapes and their individual layers

Mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of magnetic head–tape interface and reliability of tape drives. Dynamic mechanical analysis, longitudinal creep, lateral creep, Poisson's ratio, the coefficient of hygroscopic expansion (CHE), and the coefficient of thermal expansion (CTE) tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent values were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from ?50 to 150 or 210°C. Longitudinal creep tests were performed at 25°C/50% RH, 40°C/25% RH, and 55°C/10% RH for 50 h. The Poisson's ratio and lateral creep were measured at 25°C/50% RH. CHE was measured at 25°C/15–80% RH. CTE values of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research included two magnetic particle (MP) tapes and two metal evaporated (ME) tapes that were based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus and creep compliance for these samples were generated for a frequency range from 10^?20 to 10¹⁵ Hz. The effect of tape manufacturing process on the various mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, creep compliance, and CTE for the front coat and back coat of MP and ME tapes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1319–1345, 2004     

Dynamic mechanical and thermal analyses of magnetic particle and metal evaporated tapes and their individual layers

The mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of the magnetic head–tape interface. Dynamic mechanical analysis and thermomechanical analysis tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from ?50 to 150 or 210°C. Coefficients of thermal expansion (CTE) of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research include two magnetic particle (MP) tapes and two metal evaporated (ME) tapes based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus for these samples were generated for a frequency range from 10^?20 to 10¹⁵ Hz. The effect of the tape manufacturing process on the dynamic mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, and CTE for the front coat and back coat of MP and ME tapes. To validate the procedure, data for these individual layers were then used to calculate the corresponding properties of the finished tape. The predicted results were compared with the experimental measurements. The data obtained in the study are also discussed in light of previously published lateral contraction, Poisson's ratio, CTE, and CHE (coefficient of hygroscopic expansion) data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 548–567, 2003     

Long‐term mechanical and viscoelastic behavior of constitutive polymeric materials used for magnetic tapes

Creep‐compliance behavior of specially prepared magnetic tape materials was measured at elevated temperature levels to facilitate the use of a time–temperature superposition (TTS) process. This TTS process allowed for the construction of master curves at a reference temperature of 30°C, which were used to predict the long‐term viscoelastic behavior of the magnetic particle (MP) and metal‐evaporated (ME) tapes used in the study. The specially prepared samples allowed for the use of a rule of mixtures technique to determine the long‐term creep compliance of the front coat and back coat used for the magnetic tapes. To test the validity of this procedure, the front coat, substrate, and back coat data determined through separate experiments were used to calculate creep compliances of simulated tapes. These calculated creep‐compliance curves were then compared to measured data for the actual magnetic tapes. After determination and validation of the front coat, substrate, and back coat creep‐compliance data sets, they were used to determine strain distributions when the tapes are stored in a reel. Strain distributions were calculated for two cases, which reflect how tapes are stored in different drives: (1) the front coat (magnetic + nonmagnetic layer) is oriented away from the hub, and (2) the front coat is oriented toward the hub. Results showed that strain in the critical front coat of a tape is lower if it is stored with the front coat oriented toward the hub. In addition, the use of the creep‐compliance data showed that the MP tape front coat is more susceptible to creep than the ME tape front coat. The strain distributions in future magnetic tapes were also simulated by reducing the thickness and compliance of the layers. Results showed the importance of using lower compliance front coat, substrate, and back coat materials if thinner tapes are to be developed to increase the volume of information that can be stored in a magnetic tape reel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1142–1160, 2001     

Mechanical,hygroscopic, and thermal properties of ultrathin polymeric substrates for magnetic tapes

Mechanical, hygroscopic, and thermal properties of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), and aromatic polyamide (ARAMID). PET films are currently the most commonly used polymeric substrate material for magnetic tapes, followed by PEN and ARAMID. The thickness of the films ranges from 6.2 to 4.8 μm. Tensile tests were run to obtain the Young's modulus, F5 value, strain at yield, breaking strength, and strain at break. The storage modulus, E′, and the loss tangent, tan δ, were measured using a dynamic mechanical analyzer (DMA) at temperature ranges of ?50 to 150°C (for PET) and ?50 to 210°C (for PEN and ARAMID) and at a frequency range of 0.016–28 Hz. Frequency–temperature superposition was used to predict the dynamic mechanical behavior of the films over a 28‐decade frequency range. Short‐term longitudinal creep behavior of the films during 10, 30, 60, and 300 s, 7 MPa, were measured at 25 and 55°C. Long‐term longitudinal creep measurements were performed at 25, 40, and 55°C for 100 h. The Poisson's ratio and 50‐h long‐term lateral creep were measured at 25°C/15% RH, 25°C/50% RH, 25°C/80% RH, and 40°C/50% RH. The in‐plane coefficient of hygroscopic expansion (CHE) at 25°C/20–80% RH and the coefficient of thermal expansion (CTE) at 30–70°C were measured for all the samples. The properties for all films are summarized. The relationship between the polymeric structure and the mechanical and physical properties are discussed, based on the molecular structure, crystallinity, and molecular orientation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3052–3080, 2003     

Viscoelastic characteristics of magnetic tapes with PEN substrates

Viscoelastic characteristics of magnetic tapes with poly(ethylene naphthalate) substrates were studied using experimental techniques. Measurements were made using samples cut from commercially available tapes, and solvents were used to remove front and/or back coat layers to obtain substrates and dual‐layer samples. Experimental results allowed for fundamental compliance and viscosity parameters to be determined using a Kelvin‐Voigt model. Rates of creep‐compliance were also predicted, and comparisons were made with results for tapes that used poly(ethylene terephthalate) and aromatic poly(amide) substrates. Dynamic mechanical analysis (DMA) was used to help make correlations between viscous characteristics measured from the creep‐compliance results and molecular characteristics of the substrates. Time‐temperature superposition (TTS) was used to predict creep‐compliance over extended time periods, and a rule‐of‐mixtures method was used to predict the compliance of constitutive layers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic mechanical analysis of magnetic tapes at ultra‐low frequencies

A custom, ultra‐low frequency, dynamic mechanical analyzer (ULDMA) has been developed to study the correlated effects of temperature and frequency on the viscoelastic behavior of magnetic tapes. It has been used to acquire data needed for the development of future magnetic tapes that require an archival life of up to 100 years. A range of elevated temperatures is used to simulate real‐world storage environments, which enables the investigation of how the viscoelastic characteristics of tape samples influence the extent to which the tape deforms. The experiments and subsequent analysis examine the influence of the molecular structure on the viscoelasticity of magnetic tapes. Experiments were performed on a variety of magnetic tapes, including poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), metalized PET (M‐PET), and metalized Spaltan (M‐SPA). Additional experiments examined PEN and PET substrates by removing the front and back magnetic layers from the tape sample. Because of the viscoelastic behavior of the tapes, a time delay was present between the strain and stress signals, which was determined using a Fourier transform program. The elastic modulus (E), storage modulus (E′), loss modulus (E″), and loss tangent (tan δ) were obtained from the time delay for each of the ULDMA experiments at 25, 50, and 70°C over the frequency range of 0.0100–0.0667 Hz. Plots of these mechanical characteristics demonstrate the ability of frequency and temperature to affect trends associated with mechanical and thermal properties. Finally, some samples displayed an initial relaxation during the ULDMA experiments, which, when modeled using Maxwell's viscoelastic model, provided an insight into the relaxation characteristics of the samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamic mechanical analysis of barium ferrite magnetic tapes with aramid and poly(ethylene naphthalate) substrates

Frequency‐ and temperature‐dependent viscoelastic characteristics of advanced materials used for high‐capacity digital magnetic tapes were analyzed using a custom ultra‐low frequency dynamic mechanical analyzer (ULDMA). The magnetic tapes studied both use barium ferrite (BaFe) magnetic particles. One tape uses an aromatic poly(amide) or aramid substrate, and the other tape uses a poly(ethylene naphthalate) or PEN substrate. ULDMA studies were performed for both types of tape materials using samples cut from reels and the substrates after the front and back coats were removed. Two‐hour experiments were performed at 25, 30, 50, and 70°C temperatures, and four test frequencies were used at each temperature: 0.006, 0.010, 0.033, and 0.065 Hz. Properties determined were the peak strain‐based elastic modulus, E, and the storage modulus, E′, loss modulus, E″, loss tangent, tan(δ), complex modulus, E*, and complex loss, E″/E*, expressed as a percentage. When compared with the PEN tape and substrate materials, the peak elastic modulus, storage modulus, and complex modulus were higher for the aramid materials. Substrates for each material exhibited higher elastic, storage, and complex moduli compared with their respective tapes. Through the complex loss percentage, comparisons were made between the aramid and PEN materials related to their viscoelastic characteristics. Finally, the influence of frequency was shown to have increasing relevance at higher temperatures, with the PEN tape and substrate exhibiting an increase in complex loss modulus in the 50°C range because of the β* secondary transition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41478.     

Viscoelastic analysis applied to the determination of long‐term creep behavior for magnetic tape materials

Creep‐compliance experiments were performed for three representative magnetic tapes. Two of these tapes used a magnetic particle (MP) coating, and one used a metal‐evaporated (ME) coating. The MP tapes used the following polyester substrates: semitensilized poly(ethylene naphthalate) (PEN) and supertensilized poly(ethylene terephthalate). The ME tape used an aromatic poly(amide) or aramid substrate. Time–temperature superposition was used to make creep‐compliance predictions at 30 and 50°C reference temperatures. Comparisons were made with dimensional stability requirements based on position error signal (PES) specifications for magnetic tape drives along with in‐cartridge creep specifications based on PES measurements. Circumferential and lateral creep strains were determined that account for storage of the tapes in a reel, and creep strains were predicted for future tapes with thinner, lower compliance coatings. A rule of mixtures method was also used to extract compliance information for individual layers of MP‐PEN tapes, and stress profiles through the thickness of the tapes were determined. Additional measurements and analyses were performed to determine the creep recovery and shrinkage characteristics for the magnetic tapes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1106–1128, 2006     

The splitting tendency of uniaxially-oriented PET tapes investigated with nano-indentation,nano-scratch,differential scanning calorimetry,and X-ray

Earlier, various additives werescreened to improve the weavability of poly(ethylene terephthalate) (PET) tape. For predicting the weavability, three tests had been used: tensile impact strength, fibrillar versus puckered fracture and an axial folding test. This paper shows the possibility of using a simple nano-indentation method to decide on the splintering tendency of uniaxially-oriented PET tapes, as a predictor for weavability. A plasticity index derived from the nano-indentation correlated with PET tapes that were, or were not, weavable. Nano-scratches applied parallel and perpendicular to the tape also showed differences that could be correlated to the splitting tendency. While investigating these tests methods, it was observed that pure uniaxially- oriented PET tape heat set at 140°C had a non-splintering character even without additives, while polymeric additives were needed to resist splintering for the tape heat set at 240°C. Calorimetry showed no difference in heat-of-fusion implying identical crystallinity in the tapes heat set at 140°C and 240°C. However, X-ray studies revealed that the crystallites in the tape heat set at 140°C were smaller/and or imperfect, and hence there were more lateral tie-molecules that provided it the splitting resistance. Pure PET tape if heat set below 150°C may be a workable solution for weaving, thereby dispensing with the need for toughening additives.     

Study on the Viscoelastic Poisson‘s Ratio of Solid Propellants Using Digital Image Correlation Method

Digital image correlation methods were used for further studies of the viscoelastic Poisson's ratio of solid propellants. The Poisson's ratio and the Young's relaxation modulus of solid propellants were separately determined in a single stress relaxation test. In addition, the effects of temperature, longitudinal strain, preload and storage time on the Poisson's ratio of solid propellants were discussed. The Poisson's ratio master curve and the Young's relaxation modulus master curve were constructed based on the time‐temperature equivalence principle. The obtained results showed that the Poisson's ratio of solid propellants is a monotone non‐decreasing function of time, the instantaneous Poisson's ratio increased from 0.3899 to 0.4858 and the time of the equilibrium Poisson's ratio occurred late when the temperature was varied from −30 °C to 70 °C. The Poisson's ratio increased with temperature and longitudinal strain, decreased with preload and storage time, while the amplitude Poisson's ratio increased with preload, decreases with longitudinal strain and storage time. The time of the equilibrium Poisson's ratio occurred in advance with the increase of longitudinal strain, preload and storage time.     

Viscoelastic behavior of polymer tape in a wound roll

A viscoelastic computational model is developed that uses experimentally determined viscoelastic material properties as input and can be used to predict the behavior of a tape material in a wound roll as stresses relax over time. Experimental creep test results are used to find best‐fit creep‐compliance parameters to describe two high density data storage tape media. The two tapes used in the analysis are a developmental tape with a poly(ethylenenaphthalate) (PEN) substrate and metal particle (MP) front coat similar to linear tape open (LTO4) (referred to in this work as “Tape C”), and LTO3, a commercially available tape with a PEN substrate and MP front coat. Sets of best‐fit creep‐compliance parameters are determined for both tapes. The differences between the predicted behavior using three‐, five‐, and seven‐parameter Kelvin–Voigt models are evaluated, both for a benchmark case and in a viscoelastic wound roll model. The choice of material model is found to significantly influence the predictions of the wound roll model. The differences between different material models for the same material are on the order of the differences found between the two different materials. A material model with a higher number of creep‐compliance parameters, although more computationally expensive, produces better results, particularly over long spans of time. The relative differences between the three‐, five‐, and seven‐parameter models are shown to be qualitatively consistent for several variations in the computational model setup, allowing predictions to be made based on simple benchmarks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Creep and shrinkage behavior of improved ultrathin polymeric films

Long‐term creep‐deformation and shrinkage characteristics of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes, and thinner tensilized‐type PET, PEN, and ARAMID have recently been used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 μm. More dimensional stability is required for advanced magnetic tapes, and the study of creep and shrinkage behavior is important for estimating the dimensional stability. Creep measurements were performed on all available substrates at 25, 40, and 55°C for 100 h. Based on these data, master curves were generated using time–temperature superposition to predict dimensional stability after several years. The amount of creep deformation is considerably smaller for ARAMID and tensilized‐type PET than for PEN, although Standard PET shows the largest amount of creep. In addition, creep measurements under high humidity also show similar trends. Shrinkage measurements at 55°C for 100 h show that the shrinkage of ARAMID is lower than that of PET and PEN. The relationship between the polymeric structure and dimensional stability are also discussed. Based on the creep and shrinkage behavior, ARAMID and tensilized‐type PET seem to be suitable for advanced magnetic tapes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1477–1498, 2002; DOI 10.1002/app.10012     

Measurements of interfacial strength from the blister test

Measurements of the interfacial properties between an elastic tape and poly(methyl methylcrylate) substrates were carried out using a circular blister test. All properties, including adhesive fracture energy G_a, residual stress ς_o and the elastic modulus of the tapes can be deduced in a single test. Three different approaches have been adopted to analyze the relations between blister radius, blister height, and the pressure inside the blister. A comparison of the calculated results from these methods is provided and the details of the fracture process are discussed. Effect of the volume flowrate of the injected fluid was investigated as well. Results show that the deduced value of G_a is about 3.0 ± 0.5 J/m² and the elastic modulus of tape is 330 ± 40 MPa, in good agreement with that determined from the tensile test. The fracture time is reduced from 4000 to 700 s for a flowrate of the injected fluid from 0.05 to 0.5 mL/h. In all cases, quasistatic deformation of the blister is found valid and the effect of the flowrates on the failure mechanics is not significant for the present study. However, one should take the dynamic deformation effect of the blister into consideration when the flowrate is too high. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1899–1912, 1999     

Thermal cycling failure of the multilayer thermal barrier coatings based on LaMgAl11O19/YSZ

Thermal cycling failure of three multilayer TBCs based on LaMgAl₁₁O₁₉ (LaMA)/YSZ was comparatively investigated by using the burner-rig testing method in this work. Results indicate that through optimizing the weight ratio and thickness of the intermediate LaMA/YSZ composite layers, a five-layer TBC with much improved thermal cycling life of 11,749 cycles at 1372 °C surface and 1042 °C bond coat testing temperature has been realized. While, thermal cycling lifetimes of the tri- and six-layer TBCs were 7439 and 7804 cycles at surface/bond coat testing temperatures of 1378 °C/1065 °C and 1367 °C/1056 °C, respectively. Factors related to the 60 wt.% LaMA + 40 wt.% YSZ (60LaMA + 40YSZ) intermediate composite layer with the highest thermal expansion coefficient than other composite layers generating higher internal stress level to the tri- and six-layer TBCs, different bond coat temperature and TGO growth, as well as long-term stability of the LaMA coating during thermal cycling tests, were characterized and compared to understand the different thermal cycling lifetime and failure modes among such three multilayer TBCs.     

Adhesive Properties of Siloxane Modified Polyimides and Application for Multi-Layer Printed Circuit Boards

The adhesive properties of various siloxane modified polyimides were studied for the development of suitable adhesive materials with good thermal stability. Their adhesive properties were influenced by siloxane content in the polymer backbone and the structure of the aromatic component. Among them, the copolyimides with small amounts of the siloxane unit showed the better lap shear strength compared with the corresponding all-aromatic polyimides. They had excellent adhesive strength to various substrates. Their adhesive durability under the highly humid condition (25°C, 90%RH) was also improved mainly due to their lower moisture sorption and lower moisture permeability. However, further siloxane modification lowered their adhesive strength and durability. On the other hand, thee T-peel strength of copolyimides was lowered according to the increase of siloxane content. Based on this study, a new type of adhesive film which was composed of a copolyimide as a major component, SPB-505A, was developed and reported. This is useful for multi-layered printed circuit boards due to the excellent adhesive properties, good electrical properties and distinguished reliability under the hot / wet condition (121°C, 2 atm, 85%RH).     

Stress development in supported polymer films during thermal cycling

A simple and in-situ bending-beam technique has been used to investigate the stress-temperature relationships for three different polymer coatings (viz, poly(methyl methacrylate), FR-4 epoxy resin, and an amide-imide polymer) during thermal cycling. With this technique, we were able to detect stress relaxation near the polymer's glass transition or caused by cracking of the polymer. Knowing the Poisson's ratio and Young's modulus for the polymer, this technique also allows calculation of the polymer's thermal expansion coefficient from measured thermal stress data. The calculated thermal expansion coefficient of poly(methyl methacrylate) (7 × 10^?5/°C) is in good agreement with literature values (5 to 9 × 10^?5/°C).     

Low sintering shrinkage porous mullite ceramics with high strength and low thermal conductivity via foam-gelcasting

Excessive sintering shrinkage leads to severe deformation and cracking, affecting the microstructure and properties of porous ceramics. Therefore, reducing sintering shrinkage and achieving near-net-size forming is one of the effective ways to prepare high-performance porous ceramics. Herein, low-shrinkage porous mullite ceramics were prepared by foam-gelcasting using kyanite as raw material and aluminum fluoride (AlF₃) as additive, through volume expansion from phase transition and gas generated from the reaction. The effects of AlF₃ content on the shrinkage, porosity, compressive strength, and thermal conductivity of mullite-based porous ceramics were investigated. The results showed that with the increase of content, the sintering shrinkage decreased, the porosity increased, and mullite whiskers were produced. Porous mullite ceramics with 30 wt% AlF₃ content exhibited a whisker structure with the lowest shrinkage of 3.5%, porosity of 85.2%, compressive strength of 3.06 ± 0.51 MPa, and thermal conductivity of 0.23 W/(m·K) at room temperature. The temperature difference between the front and back sides of the sample reached 710°C under high temperature fire resistance test. The low sintering shrinkage preparation process effectively reduces the subsequent processing cost, which is significant for the preparation of high-performance porous ceramics.     

Calcium aluminate cement tapes – Part II: Physical properties

Tape casting is a process often used for the preparation of microelectronics substrates. The present work is a continuation of the first part where we have discussed the structural and microstructural characteristics of calcium aluminate cement tape. Indeed, in this second part, we focus on the physical properties of these tapes such as electrical, thermal, mechanical characterizations and surface roughness. We studied in particular how these physical properties vary according to the setting environment (water, air at 50% relative humidity or air saturated in humidity), setting time (1 day, 4 days or 1 month) and setting temperature (20 °C or 70 °C in the case of water setting environment). A Heat treatment on the consolidated tape was made essentially to decrease the dielectric constant. Following our results and comparing the physical properties with those of substrates commonly used in microelectronics, in particular alumina substrates, our films can be potentially used as microelectronics substrate.     

Processing, Microstructure, and Properties of Laminated Silicon Nitride Stacks

By lamination of silicon nitride tapes, components with complex geometries can be produced. Unstructured tapes can be laminated by common thermal compression. Structured tapes, however, have to be joined by pressureless processes using e.g. pastes as lamination aids because deformation of the structures would occur. These pastes usually contain a binder for maintaining the mechanical contact between the tapes during processing. To prevent the high mass loss of typical organic binders during burnout, pre-ceramic polymers were used in this work. These ceramic precursors convert partly into an inorganic material during heat treatment with a significant reduced mass loss compared with common organic binders. Thus, the porosity in the interlayer of a laminated stack is strongly decreased, which should be favorable for the mechanical and thermal properties. This work discusses the resulting microstructure, strength, and thermal diffusivity data of stacks laminated with pastes containing various precursor contents. These results are compared with those obtained by samples prepared by compression of green tapes. It is found that except for some large pores, the microstructure of the precursor-derived interlayers is qualitatively the same as in the tape material. For stacks made by both lamination methods, strength measurements reveal that the properties parallel and perpendicular to the layers are different. It is shown that the same strength level can be obtained both by using the pressureless route and by the compression method. Unlike the strength, the thermal conductivity does not change with the direction of measurement.     

Microstructural,mechanical and thermal shock properties of triple-layer TBCs with different thicknesses of bond coat and ceramic top coat deposited onto polyimide matrix composite

In this study, a triple-layer thermal barrier coating (TBC) of Cu-6Sn/NiCrAlY/YSZ was deposited onto a carbon-fiber reinforced polyimide matrix composite. Effects of different thicknesses of YSZ ceramic top coat and NiCrAlY intermediate layer on microstructural, mechanical and thermal shock properties of the coated samples were examined. The results revealed that the TBC systems with up to 300 µm top coat thicknesses have clean and adhesive coating/substrate interfaces whereas cracks exist along coating/substrate interface of the TBC system with 400 µm thick YSZ. Tensile adhesion test (TAT) indicated that adhesion strength values of the coated samples are inversely proportional to the ceramic top coat thickness. Contrarily, thermal shock resistance of the coated samples enhanced with increase in thickness of the ceramic coating. Investigation of the TBCs with different thicknesses of NiCrAlY and 300 µm thick YSZ layers revealed that the TBC system with 100 µm thick NiCrAlY layer exhibited the best adhesion strength and thermal shock resistance. It was inferred that thermal mismatch stresses and oxidation of the bond coats were the main factors causing failure in the thermal shock test.