Characterization of Hafnium-Zirconium-Oxide-Nitride films grown by ion beam assisted deposition

Hafnium-Zirconium-Oxide-Nitride (Hf_1−xZr_xO_1−yN_y) films are prepared by ion beam assisted deposition on p-Si and quartz substrates with a composite target of sintered high-purity HfO₂ and ZrO₂. The thermal stability and microstructure characteristics for Hf_1−xZr_xO_1−yN_y films have been investigated. EDS results confirmed that nitrogen was successfully incorporated into the Hf_1−xZr_xO₂ films. XRD and Raman analyses showed that the Hf_1−xZr_xO_1−yN_y films remain amorphous after 1100 °C under vacuum ambient, and monoclinic HfO₂ and ZrO₂ crystals separate from Hf_1−xZr_xO_1−yN_y films with a increase of the annealing temperature up to 1300 °C. Meanwhile, the Hf_1−xZr_xO_1−yN_y films can also effectively suppress oxygen diffusion during high temperature annealing. AFM measurements demonstrated that surface roughness of the Hf_1−xZr_xO_1−yN_y films increase slightly. Then the optical properties of the samples were observed in the ultraviolet-visible range at room temperature. The variation in E_g from 5.64 to 6.09 eV as a function of annealing temperature has also been discussed briefly.     

Fracture behavior under mixed-mode loading of ceramic plasma-sprayed thermal barrier coatings at ambient and elevated temperatures

The fracture behavior under modes I and II loading of ceramic plasma-sprayed thermal barrier coatings was determined in air at 25 and 1316 °C in asymmetric four-point flexure. The mode I fracture toughness was found to be K_Ic = 1.15 ± 0.07 and 0.98 ± 0.13 MPa , respectively, at 25 and 1316 °C. The respective ‘nominal’ mode II fracture toughness values were K_IIc = 0.73 ± 0.10 and 0.65 ± 0.04 MPa . The empirical mixed-mode fracture criterion best described the coatings’ fracture behavior under mixed-mode loading. The angle of crack propagation was in reasonable agreement with the minimum strain energy density criterion.     

Changes in surface morphology of Ti6Al4V alloy and ZrO2-Y2O3 ceramic coating modified by high-intensity pulsed ion beams

The high-intensity pulsed ion beam (HIPIB) technique is developed to treat metallic and ceramic surfaces to improve materials performance. The processing is based on the beam-material interactions: remelting and/or ablation of a top layer on the irradiated surfaces (extreme surface heating effect); subsequently, the molten states may be frozen at an ultra-fast re-solidification rate after termination of the ion beam pulse. Surface smoothing and reconstruction of titanium alloys and ZrO₂-Y₂O₃ coatings have been observed as one of the typical outcome under high-intensity pulsed ion beam irradiation. It is demonstrated that the changes in surface morphology may significantly contribute to the improvements of overall performance of the materials.     

Failure morphologies of cyclically oxidized ZrO2-based thermal barrier coatings

Abstract

Advanced and baseline thermal barrier coatings (TBCs) were thermal cycle tested in air at 1163°C until delamination or spallation of the ceramic top coat. The top coat of the advanced TBC’s consisted of ZrO₂ with various amounts of Y₂O₃, Yb₂O₃, Gd₂O₃, or Nd₂O₃ dopants. The composition of the top coat of the baseline TBC was ZrO₂-8wt.%Y₂O₃. All top coats were deposited by air plasma spraying. A NiCrAlY or NiCoCrAlY bond coat was deposited by low pressure plasma spraying onto a single-crystal, Ni-base superalloy. The TBC lifetime for the baseline coatings was approximately 190 cycles (45 minutes at 1163°C per cycle) while the lifetime for the advanced coatings was as high as 425 cycles. The fracture surfaces and sample cross sections were examined after TBC failure by SEM and optical microscopy, and the top coats were further examined by X-ray diffraction. These post-test studies revealed that the fracture path largely followed splat boundaries with some trans-splat fracture. However, there were no obvious distinguishing features which explained the difference in TBC lifetimes between some of the advanced and baseline coatings.     

Effect of assist ion beam voltage on intrinsic stress and optical properties of Ta2O5 thin films deposited by dual ion beam sputtering

The optical properties and intrinsic stress of Ta₂O₅ thin films deposited by dual ion beam sputtering (DIBS) were studied as a function of the assist ion beam voltage (250-650 V). When the assist ion beam voltage was in the range of 350-450 V, the transmittance at the quarter-wave point reached its highest value (lowest absorption). The refractive index increased to 2.185 as the assist ion beam voltage increased from 250 to 350 V, but decreased as the assist ion beam voltage was further increased from 350 to 650 V.     

Vickers Indentation Fracture (VIF) modeling to analyze multi-cracking toughness of titania, alumina and zirconia plasma sprayed coatings

For massive brittle materials, the fracture toughness in mode I, K_IC, can be determined using various reliable techniques. Besides, Vickers Indentation Fracture (VIF) technique has been developed to locally determine fracture toughness. However, since the indentation test generates a complex three-dimensional crack system around the indent, fracture toughness, K_C, is calculated instead of K_IC. Consequently some authors rightly reject the VIF technique to determine standard fracture toughness by arguing that the literature counts numerous VIF crack equations thus revealing discrepancies of this technique. Nevertheless in some cases (e.g. brittle ceramic coatings) inclusive material techniques are not applicable since presence of the substrate and/or multi-crack network can modify the crack propagation into the coating.In this work, we employed VIF technique to study multi-cracking behavior of titania, alumina and zirconia ceramic oxide coatings obtained by plasma spraying. To calculate VIF toughness, we propose (i) to select two crack equations for radial-median and Palmqvist cracking modes respectively, (ii) to adjust the crack equation of Miranzo and Moya for intermediate cracking mode, (iii) to develop a mathematical approach to determine the cracking mode, (iv) to take into account the multi-crack network by defining an equivalent four-crack system and (v) to propose a universal crack equation applicable independently of the cracking mode.     

Industrially-styled room-temperature pulsed laser deposition of titanium-based coatings

Titanium-based compounds are widely used as coating materials for mechanical, tribological, electrical, optical, catalytic, sensoric, micro-electronical applications due to their exceptionally physical and chemical properties. Recently, the trend of using temperature-sensitive materials like polymers and tool steels with the highest hardness demands new low-temperature coating techniques for protective surface finishing as well as for surface functionalization, but up to now there is lack of industrially scaled vacuum coating techniques at temperatures below 50 °C. An alternative for overcoming this problem is the pulsed laser deposition (PLD) technique, which was up-scaled for industrial demands at Laser Center Leoben of JOANNEUM RESEARCH Forschungsgesellschaft mbH.The current paper summarizes the application of the industrially-scaled PLD technique on the deposition of the presently most important Ti-based coatings: metallic titanium, titanium nitride (TiN), titanium oxide (TiO₂) and titanium carbonitride (TiCN). PLD coating allows, even at room temperature, the formation of film structures of Zone-T type of Thornton's structure zone model, both on substrates aligned normal and parallel to the incident vapor flux. The high-energetic deposition conditions are revealed by the occurrence of (2 2 0) textures for the fcc TiN-based films. The dense grown structure affects advantageously the tribological behavior—generally, low wear rates and (for TiCN) very low friction coefficients were found. For TiO₂ coatings, growing as a mixture of β-TiO₂ and amorphous phases, the easily reproducible change of deposition parameters in the room-temperature PLD allows large differences in the optical transmission and electrical resistance.     

Numerical analysis of fracture behaviour of multilayered bimaterials composites beams

In the present work the finite element method is used to calculate the energy release rate at the interfacial crack tip of Al₂O₃/ZrO₂/Al₂O₃ and Al₂O₃/metal/ZrO₂ composite. The behaviour of the bonded materials is supposed to be linear and elastic. The effects of the layer number, the thickness of the composite beam, the crack length as well as of the crack position on the variation of the energy release rate at the crack tip were highlighted.     

ZrO2陶瓷颗粒在激光作用下组织形貌演变规律

采用激光表面处理技术制备ZrO_2复合热障涂层可使陶瓷颗粒与金属之间实现冶金结合,增加结合强度,但由于陶瓷颗粒和金属热膨胀系数之间的差异,制备大面积复合热障涂层仍存在比较严重的开裂问题.为降低复合材料层的开裂倾向,更好地控制ZrO_2陶瓷颗粒的离散规律,本文针对激光熔注过程中陶瓷颗粒的熔化问题,采用高速摄像、扫描电子显微镜研究了氧化锆陶瓷颗粒进入熔池前后激光对其形貌与离散规律的影响规律.结果表明,在激光能量密度较低的情况下,激光直接作用于氧化锆陶瓷颗粒会导致单个ZrO_2陶瓷颗粒发生裂解现象;当激光能量密度高于2.5 J/mm~2时,ZrO_2陶瓷颗粒熔化严重并发生球化现象.在激光熔注过程中,由于受到激光和高温熔池的双重作用,氧化锆陶瓷颗粒内部晶粒长大,高能量大尺寸晶界促进了Ti熔体向ZrO_2陶瓷颗粒内部扩散.     

Y2O3添加量对Al2O3/ZrO2共晶陶瓷显微组织及力学性能的影响

为探索第三组元Y₂O₃添加对Al₂O₃/ZrO₂共晶陶瓷显微组织与机械性能的影响,本文利用低温度梯度的高温熔凝法制备了直径为20 mm的Al₂O₃/ZrO₂(Y₂O₃)共晶陶瓷块体,采用SEM、EDS及XRD技术对共晶陶瓷进行微结构分析,并利用维氏压痕法对其硬度和断裂韧性进行测试。SEM结果表明,凝固组织由群集的共晶团结构组成,随着Y₂O₃添加量的增加,共晶团形态由胞状转变为枝晶状,内部相间距在1~2 μm范围内变化。力学测试表明,Y₂O₃摩尔分数小于1.1%时,由于组织内部存在低硬度m-ZrO₂及微裂纹缺陷,故陶瓷硬度较低,约为(9.53±0.22 )GPa;当Y₂O₃摩尔分数为1.1%时,陶瓷硬度最大,约为(18.05±0.27)GPa;当Y₂O₃的摩尔分数大于1.1%时,由于共晶团边界区内气孔缺陷及粗大组织增多,引起陶瓷硬度值略有下降。低Y₂O₃摩尔分数添加时,陶瓷断裂韧性相对较高,约为(6.30±0.16)MPa·m^1/2,这与其内部存在大量微裂纹缺陷有关;随着Y₂O₃添加量的增加,陶瓷的微裂纹数量减少、边界区内缺陷增多,断裂韧性降低。     

Effect of substrate temperature and deposited thickness on the formation of iron silicide prepared by ion beam sputter deposition

Ion beam sputter deposition (IBSD) method was employed to find optimum conditions for the formation of epitaxial β-FeSi₂ films on Si(100) substrate. It was found that crystal structure of the films as determined by X-ray diffraction (XRD) analysis is dependent on the substrate temperature as well as on the deposited thickness of sputtered Fe. The film with best crystal properties was obtained either at 873 K with the deposited Fe thickness of 15 nm, or at 973 K with the deposited Fe thickness of 30 nm. The obtained results indicate the importance of Fe and/or Si diffusion in determining the crystal properties of β-FeSi₂ film.     

Numerical study on effects of secondary electrons generated by TEMP II accelerator

A pulsed voltage of magnetically insulated diode and intense pulsed ion beam (IPIB) models have been built according to the experimental results. A model of secondary electrons yield while IPIB irradiated metal target has also been established. The temporal law of secondary electrons induced by IPIB irradiated titanium target according to the energy deposition at surface layer has been calculated based on the models. The maximum number of secondary electrons reached is 10¹³/cm² while the energy density of IPIB is 4 J/cm². And near the surface of target, the electric field rises up to 10¹⁰ V/m with the same IPIB energy density irradiation. The evaporation ions will be accelerated near the target, therefore it is important to the formation of films.     

A study of uv preionization pulsed tea CO2 laser

Abstract

A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home‐made TEA CO₂ laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10^‐16 V cm². The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 μs to 6.0 μs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated.     

Material properties and growth control of undoped and Sn-doped In2O3 thin films prepared by using ion beam technologies

Undoped (IO) and Sn-doped In₂O₃ (ITO) films have been deposited on glass and polymer substrates by an advanced ion beam technologies including ion-assisted deposition (IAD), hybrid ion beam, ion beam sputter deposition (IBSD), and ion-assisted reaction (IAR). Physical and chemical properties of the oxide films and adhesion between films and substrates were improved significantly by these technologies. By using the IAD method, non-stoichiometry and microstructure of the films were controlled by changing assisted oxygen ion energy and arrival ratio of assisted oxygen ion to evaporated atoms. Relationships between structural and electrical properties in ITO films on glass substrates were intensively investigated by using the IBSD method with changing ion energy, reactive gas environment, and substrate temperature. Smooth-surface ITO films (R_rms ≤ 1 nm and R_p-v ≤ 10 nm) for organic light-emitting diodes were developed with a combination of deposition conditions with controlling microstructure of a seed layer on glass. IAR surface treatment enormously enhanced the adhesion of oxide films to polymer substrate. The different dependence of IO and ITO films' properties on the experimental parameters, such as ion energy and oxygen gas environment, will be intensively discussed.     

Thermal diffusivity and conductivity of Li2ZrO3 using the modulated electron beam technique

Thermal diffusivity and thermal conductivity of three Li₂ZrO₃ specimens with two different density values, 82.6 and 87% theoretical density, have been measured between 350 and 900°C. The modulated electron beam thermal diffusivity method was used. Heating the specimens above some 850°C but below 900°C results in a reversible increase in both the diffusivity and the conductivity. When heating to higher temperatures generally still higher increases are noticed but measurements become rapidly unstable and irreversible.     

Solar heat reflective glass by nanostructured sol–gel multilayer coatings

New 3-layer near-infrared reflective glasses were prepared by coating clear float soda-lime glass with nanostructured TiO₂ and SiO₂ films using a dip coating technique. Reflective interference filters at NIR region (800–1000 nm) were designed by simulation and prepared onto 4 mm clear glass. Optical, microstructural and mechanical properties were determined for the coated glasses. 3-layer sol–gel glasses show high visible transmittance >70% combined with high solar reflectance about 30% (with reflectivity up to 60% at region from 800 to 950 nm) and high UV blockage (transmittance <35%). Due to good abrasion resistance of the filters, application for monolithic windows in automotive and architectural areas is promising.     

Photoluminescence properties of ion beam synthesized β-FeSi2

Effects of structural changes near the interface, the implantation dose and the precipitate morphology on photoluminescence (PL) properties of ion-beam synthesized (IBS) β-FeSi₂ have been investigated. The intrinsic PL spectrum attributed to the interband transition of β-FeSi₂ was found by examining the dependence of the PL peak energy on temperature and the excitation power.     

Anomalous phase formation during annealing of La2O3 thin films deposited by ion beam assisted electron beam evaporation

The fifty seven nm thick La₂O₃ thin films were deposited on Si (100) substrates. After deposition, the amorphones thin films, were amorphous, were annealed at 750 and 900 °C for 1 h. It was found that their amorphous structure had been crystallized to hexagonal and cubic structures, respectively. The phase formation of the La₂O₃ thin films was anomalous at higher annealing temperatures. The theory of heterogeneous nucleation was used to interpret the anomalous phase formation of La₂O₃ films. To investigate the effects of the phase structure on these properties, Refractive indexes and dielectric constants of different structures of La₂O₃ films were measured.     

Processing of single-phase ceramic 123 YBaCu-oxide superconductor by hot pressing

High-quality, single-phase, polycrystalline samples of high-temperature superconducting 123 YBaCu-oxide have been processed by hot pressing of specially prepared charge material at elevated temperatures. The samples are orthorhombic with unit cell dimensionsa = 3.824(1) Å,b = 3.888(1) Å, andc = 11.679(2) Å. They exhibit: (i) densities up to 82% of the theoretical value; (2) a sharp phase transition between the normal and superconducting states at 91.6 K; (3) a reduced dependence on thermal cycling effects and on excitation currents in resistivity measurements; and (4) a reduction in surface deterioration due to water, air, and acid attack. The hot-pressed samples supported current densities at least two orders of magnitude greater than those found in cold-pressed samples measured under similar conditions.     

C/C复合材料ZrB2基超高温陶瓷涂层的研究进展

ZrB₂基超高温陶瓷因其优异的高温抗氧化和烧蚀等性能,成为C/C复合材料理想的热防护涂层材料。本文从以下几个方面对C/C复合材料表面用ZrB₂基超高温陶瓷涂层的研究现状进行了综述:介绍了ZrB₂基超高温陶瓷涂层体系的主要制备技术,并对比了其制备的涂层抗氧化性和抗烧蚀性,总结了各制备方法的优点与不足;从单元、双元、三元材料掺杂改性的角度,详述了ZrB₂基复合涂层常见的材料体系,总结了其改性思路;介绍了ZrB₂基涂层在多层结构设计与开发方面的研究现状。最后简要展望了ZrB₂基超高温陶瓷涂层未来的研究方向。