Article
Chemistry, Physical
L. Peng, G. Zeng, J. Xian, C. M. Gourlay
Summary: The influence of iron on the formation of Al-Mn-Fe intermetallic compounds (IMCs) has been investigated. It was found that the iron content affects the phase fractions and morphology of the IMCs.
Article
Chemistry, Physical
D. Dubaux, J. Zollinger, M. -C. de Weerd, J. Ghanbaja, S. Mathieu, S. Migot, P. Boulet, S. Sturm, V. Fournee, M. Sicot, J. Ledieu
Summary: We report the formation of large and highly twinned dendrites of the Al13Fe4 approximant phase embedded in an fcc Al-rich matrix. Using a rapid cooling technique, the approximant appears as a 10-fold dendrite. The grain distributions within the arm are complex and a single dendrite arm can contain up to four different orientations. Three types of twins, namely {100}, {001} and {201} twins, have been identified. A growth mechanism involving heteroepitaxial growth from a decagonal Al-Fe quasicrystalline seed is proposed to explain the formation of these specific 10-fold motifs.
Article
Chemistry, Physical
Gangli Yang, Xiaoyan Li, Erhua Ren, Shanshan Li
Summary: The morphology and grain orientations of intermetallic compounds (IMCs) in full Cu3Sn joints were studied at different soldering temperatures, revealing the effects on mechanical properties and fracture mechanisms. Furthermore, the growth rates and transformations of Cu3Sn grains were found to be influenced by temperature.
Article
Chemistry, Physical
Chun-Hao Chen, Yu-Chang Lai, Tung-Han Chuang
Summary: The microstructural evolution of Ag-4Pd ribbon under various annealing conditions was investigated in this study using the EBSD technique. The results showed abnormal grain growth after prolonged annealing treatment, with calculated grain growth time exponent (n) and activation energy providing insights into the dominance of grain boundary diffusion in the material. The deviation of n value and activation energy from those of pure silver could be attributed to alloying elements and twin boundaries within the microstructure.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
C. Haug, D. Molodov, P. Gumbsch, C. Greiner
Summary: Tribological loading induces microstructural changes in metals through dislocation-mediated plastic deformation. Crystal lattice rotations play an important role in friction and wear at the sliding interface, and are influenced by sliding direction and grain orientation.
Article
Materials Science, Multidisciplinary
Ji Hoon Kim, Joo-Hee Kang, Chang-Seok Oh
Summary: This study investigates the deformation mechanism and unique mechanical behavior of commercially pure titanium (CP Ti) at room temperature. A micromechanical analysis was conducted using electron backscatter diffraction (EBSD) and crystal plasticity finite element analyses, revealing the statistical data related to the microstructure of titanium sheets. The calibration of crystal plasticity model parameters corresponding to different deformation modes helps to understand the roles of these modes in dictating the anisotropic and asymmetric behavior of CP Ti.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Multidisciplinary Sciences
Nick R. Lutjes, Silang Zhou, Jordi Antoja-Lleonart, Beatriz Noheda, Vaclav Ocelik
Summary: The study analyzes the spherulitic type of 2D crystal growth in thin amorphous Quartz films using electron back-scatter diffraction (EBSD), revealing the characteristics, growth mode, and possible mechanisms of spherulitic Quartz crystal colonies.
SCIENTIFIC REPORTS
(2021)
Article
Materials Science, Multidisciplinary
Tilman Zscheckel, Wolfgang Wisniewski, Christian Russel
Summary: In this study, the growth mechanism of polycrystalline chemical vapor deposited (CVD) ZnS on a hot isostatically pressed ZnS substrate was investigated using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The orientations and polar axes of the Zn-S-double layers in the zincblende structure of cubic ZnS were analyzed, revealing an epitaxial stacking of {111}-layers at the growth front. The results also showed that the Zn-layer of the analyzed {111}-double layers always points away from the substrate, regardless of the substrate crystals' polarity.
MATERIALS CHARACTERIZATION
(2022)
Article
Materials Science, Multidisciplinary
Chunfei Li, Josiah Dubovi, Clay Klein
Summary: This article presents a method to determine facet orientation using SEM and EBSD, which is validated with facets on spherical particles of 20 μm in an Al60Cu25Fe15 alloy. The experimental results show that the surface of the facet is parallel to the {100} lattice plane of a cubic phase.
MATERIALS CHARACTERIZATION
(2022)
Article
Materials Science, Multidisciplinary
Haitao Zhao, Junheng Gao, Guilin Wu, Honghui Wu, Chaolei Zhang, Yuhe Huang, Shuize Wang, Xinping Mao
Summary: Variant pairing is a critical factor in determining the morphology and boundary characteristics of transformation products. The conventional quantification method based on deviation angles may produce biased results. This research proposes a new quantification method using variant indexing and validates it by comparing experimental results.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2023)
Article
Multidisciplinary Sciences
Kevin Kaufmann, Hobson Lane, Xiao Liu, Kenneth S. Vecchio
Summary: Transfer learning can accelerate the training of deep learning models and improve performance with limited data. In this study, a few-shot transfer learning approach is used to classify electron backscatter diffraction pattern images, demonstrating its applicability for real-world phase identification and differentiation.
SCIENTIFIC REPORTS
(2021)
Article
Materials Science, Multidisciplinary
Junqing Han, Yuying Wu, Kai Zhao, Haoran Wang, Shushuai Liu, Xiangfa Liu
Summary: Cu foil was prepared with columnar grain growth and equiaxed grain growth with different average grain sizes by direct current electrodeposition. The correlation between the microstructures and properties of Cu foil under different grain growth methods was elucidated using EBSD, XRD, AFM, and TEM. The columnar-grown copper exhibited a remarkable preferential ratio of {220} orientation, while the equiaxed grain growth showed a superiority in {200} crystal orientation. The twin boundary density in copper foil increased as the grain growth mode changed, and grain refinement was beneficial to increase the twin boundary density.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Materials Science, Multidisciplinary
A. E. Davis, J. Donoghue, J. R. Kennedy, N. Byres, P. B. Prangnell
Summary: In-situ cooling experiments were conducted on Ti64 samples for the first time, revealing the development of alpha colonies. Primary alpha laths play a crucial role in influencing subsequent colony growth and transformation process by nucleating secondary alpha laths through sympathetic autocatalysis.
Article
Chemistry, Physical
Iztok Naglic, Blaz Leskovar, Zoran Samardzija, Bostjan Markoli
Summary: This study investigated the influence of gallium addition on the phases formed in Al-Mn alloys during casting, revealing that an increase in gallium content led to the formation of IQCs and DQCs in the alloys. Microanalysis showed that IQCs contained more gallium and less manganese compared to DQCs.
Article
Nanoscience & Nanotechnology
Josh Kacher, Timothy Ruggles, Jordan Key, Matthew Nowell, Stuart Wright
Summary: This study demonstrates the ability to quantitatively characterize the dislocation structures in additive and traditionally manufactured alloys, and discusses potential defect formation mechanisms using high angular resolution electron backscatter diffraction analysis.
SCRIPTA MATERIALIA
(2022)
Article
Chemistry, Physical
Y. Cui, C. M. Gourlay
Summary: The study investigates how different twin types and twin variants affect the growth morphology during solidification in primary Al45Cr7 and Al13Fe4 intermetallic compounds (IMCs). The number of twin variants increased with cooling rate, and cyclic twinning resulted in different growth morphologies depending on the twin variants present.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Yangchao Deng, Guang Zeng, Jingwei Xian, Hongyi Zhan, Chuming Liu, Christopher M. Gourlay
Summary: In this study, the formation of intermetallic compounds during the solidification of multi-phase magnesium alloys was comprehensively investigated. The experimental results showed that Mg2Sn forms eutectic particles with 13-Mg17Al12 and r-MgAlZn, containing multiple phases. The lattice match between Mg2Sn and r-MgAlZn was found to be the best, with Mg2Sn being correlated with the icosahedral coordination in r-MgAlZn.
MATERIALS CHARACTERIZATION
(2022)
Review
Metallurgy & Metallurgical Engineering
Guang Zeng, Shiqian Liu, Qinfen Gu, Zebang Zheng, Hideyuki Yasuda, Stuart D. McDonald, Kazuhiro Nogita
Summary: It is widely recognized that a fundamental understanding of phase transformation and microstructure control in Pb-free solder joints can accelerate the development of Pb-free solder alloys for next-generation electronics. Advanced characterization techniques, including synchrotron radiation, provide a comprehensive toolset for measuring the composition, crystallography, morphology, and properties of solder alloys. Research findings on the effects of micro-alloy additions on the microstructure and properties of Pb-free solder joints, particularly on intermetallic phases, have significant scientific and industrial implications for the design of new solder alloy compositions and the reliability of lead-free solder joints.
ACTA METALLURGICA SINICA-ENGLISH LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Liuqing Peng, Guang Zeng, Di Wang, Jingwei Xian, Shouxun Ji, Hongyi Zhan, Christopher M. Gourlay
Summary: This study investigates the formation of Al-Mn IMCs in Mg-9Al-0.7Zn-0.2Mn alloy produced by high-pressure die casting and direct chill casting. The results show that controlling solidification and filtration during casting is important for ensuring small Al-Mn intermetallic particles in these casting processes.
Article
Chemistry, Physical
L. Peng, G. Zeng, J. Xian, C. M. Gourlay
Summary: The influence of iron on the formation of Al-Mn-Fe intermetallic compounds (IMCs) has been investigated. It was found that the iron content affects the phase fractions and morphology of the IMCs.
Article
Materials Science, Multidisciplinary
Yingjie Huang, Guang Zeng, Lixin Huang, Zebang Zheng, Chuming Liu, Hongyi Zhan
Summary: This study investigates the strain rate dependence of deformation and dynamic recrystallization behaviors of basal-textured AZ80 magnesium alloy. It is found that the dominant dynamic recrystallization mechanisms vary with the strain rate. In addition, intergranular micro-cracks are more likely to initiate under high-strain-rate conditions.
MATERIALS CHARACTERIZATION
(2022)
Article
Nanoscience & Nanotechnology
Yangchao Deng, Wei Sun, Yang Yang, Hongyi Zhan, Kun Yan, Guang Zeng
Summary: The impacts of Mg2Sn precipitation on the age-hardening and deformation behavior of a Mg-4Sn-3Al-1Zn alloy have been studied. The alloy shows moderate hardening during ageing treatment at 175℃, with a significant increase in yield tensile strength but reduced elongation. Nanosized Mg2Sn precipitates are uniformly distributed within grains, improving tensile strength properties. Coarsened Mg2Sn precipitates and precipitate-free zones (PFZs) can be observed along grain boundaries. Tensile deformation primarily occurs in slip band array regions in grain interiors for the solution-treated alloy, and in PFZs for the as-aged alloy. The decrease in tensile ductility is caused by early intergranular microcracks initiated by coarse grain boundary Mg2Sn precipitates and PFZs. The results provide insights for developing affordable Mg alloys with a balanced combination of strength and ductility.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Materials Science, Multidisciplinary
N. Hou, J. W. Xian, A. Sugiyama, H. Yasuda, C. M. Gourlay
Summary: In this study, we investigated the morphology transitions of the β-Sn + Ag3Sn eutectic at increasing growth velocity. The orthorhombic Ag3Sn grew as faceted plates or rods with [010] growth direction and (001) as the largest facet in three eutectic growth morphologies. Reproducible β-Sn + Ag3Sn orientation relationships were observed in the latter two morphologies. The mechanisms of spacing adjustment and the reversible transition from plate to rod growth were studied for transient solidification after velocity changes.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Y. Cui, J. W. Xian, A. Zois, K. Marquardt, H. Yasuda, C. M. Gourlay
Summary: The factors affecting the nucleation and morphology of large Ag3Sn plates in solder joints are not well understood. This study investigates the faceted solidification of Ag3Sn and reveals transitions from single crystal plates to cyclic twinned plates and highly branched structures. Real-time X-ray imaging confirms that Ag3Sn cyclic twins originate from a common point during nucleation or the early stages of growth. Soldering to copper substrates catalyzes Ag3Sn nucleation through constitutional supercooling and geometrical catalysis.
Article
Chemistry, Physical
C. J. Lin, L. Peng, J. W. Xian, Q. Li, C. M. Gourlay
Summary: In hypoeutectic Mg-Al-based alloys, Mg17Al12 forms by a eutectic reaction that is usually divorced. The nucleation, growth, and morphology of Mg17Al12-containing eutectic in a multicomponent Mg-9Al-0.7Zn-0.2Mn alloy are investigated. Mg17Al12 forms an interconnected 3D skeleton and occasionally has a preferred orientation relationship with alpha-Mg. The degree of partially divorced growth depends on geometric measures, and fully coupled eutectic microstructures can be generated by manipulating the solidification time and cooling rate.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Yang Yang, Yangchao Deng, Ruifeng Zhang, Yuqing Su, Siyue Liu, Christopher M. Gourlay, Guang Zeng
Summary: This study investigates the correlation between microstructure and corrosion behavior of AZ series alloys using various techniques. The results show that a 3D interconnected eutectic network protects against localized corrosion in chloride solution. Additionally, Al-Mn intermetallics treated with a solution lead to filament corrosion instead of pitting corrosion, due to a reduction in potential difference.
Article
Materials Science, Multidisciplinary
Hu Yao, Guang Zeng, Qinfen Gu, Kazuhiro Nogita, Jing Guo, Qian Li
Summary: The influences of microstructure evolution induced by thermal-mechanical processing on the hydrogen storage performance of Mg-Ni-Gd-Y-Zn-Cu alloys were investigated. The extruded alloy showed higher hydrogen absorption capacity and faster hydrogen ab/desorption kinetics due to refined alpha-Mg grains and the presence of 14H-type LPSO phases. These findings have implications for the design and manufacturing of magnesium-based hydrogen storage materials.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Editorial Material
Materials Science, Multidisciplinary
Hongyi Zhan, Guang Zeng, Qigui Wang, Congjie Wang, Pan Wang, Zhou Wang, Yiwu Xu, Devin Hess, Paul Crepeau, Jianfeng Wang
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Tim M. Schwarz, Hongyi Zhan, Baptist Gault, Christopher M. Gourlay, Ingrid McCarroll
Summary: The peak-aged magnesium-aluminum-rare earth (Mg-Al-RE) alloy AE44-2, produced through high-pressure die casting, exhibits a 10% increase in yield strength due to the formation of nanoscale AlMn precipitates. Atom probe tomography reveals the presence of Ce-rich clusters in the dendritic region rather than the inter-dendritic alpha-Mg in the as cast state, indicating their formation is mainly determined by solidification kinetics rather than concentration. These Ce-rich clusters act as heterogeneous nucleation sites for the formation of Al10Mn7RE2 nanoscale precipitates during the T5 heat treatment, suggesting a potential pathway for tailoring mechanical properties.
SCRIPTA MATERIALIA
(2023)
Article
Materials Science, Multidisciplinary
Y. Liu, K. Zweiacker, C. Liu, J. T. McKeown, J. M. K. Wiezorek
Summary: The evolution of rapid solidification microstructure and solidification interface velocity of hypereutectic Al-20at.%Cu alloy after laser melting has been studied experimentally. It was found that the formation of microstructure was dominated by eutectic, alpha-cell, and banded morphology grains, and the growth modes changed with increasing interface velocity.
Article
Materials Science, Multidisciplinary
Bharat Gwalani, Julian Escobar, Miao Song, Jonova Thomas, Joshua Silverstein, Andrew Chihpin Chuang, Dileep Singh, Michael P. Brady, Yukinori Yamamoto, Thomas R. Watkins, Arun Devaraj
Summary: Castable alumina forming austenitic alloys exhibit superior creep life and oxidation resistance at high temperatures. This study reveals the mechanism behind the enhanced creep performance of these alloys by suppressing primary carbide formation and offers a promising alloy design strategy for high-temperature applications.
Article
Materials Science, Multidisciplinary
Jian Song, Qi Zhang, Songsong Yao, Kunming Yang, Houyu Ma, Jiamiao Ni, Boan Zhong, Yue Liu, Jian Wang, Tongxiang Fan
Summary: Recent studies have shown that achieving an atomically flat surface for metals can greatly improve their oxidation resistance and enhance their electronic-optical applications. Researchers have explored the use of graphene as a covering layer to achieve atomically flat surfaces. They found that high-temperature deposited graphene on copper surfaces formed mono-atomic steps, while annealed copper and transferred graphene on copper interfaces formed multi-atomic steps.
Article
Materials Science, Multidisciplinary
Jennifer A. Glerum, Jon-Erik Mogonye, David C. Dunand
Summary: Elemental powders of Al, Ti, Sc, and Zr are blended and processed via laser powder-bed fusion to create binary and ternary alloys. The microstructural analysis and mechanical testing show that the addition of Ti results in the formation of primary precipitates, while the addition of Sc and Zr leads to the formation of fine grain bands. The Al-0.25Ti-0.25Zr alloy exhibits comparable strain rates to Al-0.5Zr at low stresses, but significantly higher strain rates at higher stresses during compressive creep testing. Finite element modeling suggests that the connectivity of coarse and fine grain regions is a critical factor affecting the creep resistance of the alloys.
Article
Materials Science, Multidisciplinary
P. Jannotti, B. C. Hornbuckle, J. T. Lloyd, N. Lorenzo, M. Aniska, T. L. Luckenbaugh, A. J. Roberts, A. Giri, K. A. Darling
Summary: This work characterizes the thermo-mechanical behavior of bulk nanocrystalline Cu-Ta alloys under extreme conditions. The experiments reveal that the alloys exhibit unique mechanical properties, behaving differently from conventional nanocrystalline Cu. They do not undergo grain coarsening during extrusion and exhibit behavior similar to coarse-grained Cu.
Article
Materials Science, Multidisciplinary
Yiqing Wei, Jingwei Li, Daliang Zhang, Bin Zhang, Zizhen Zhou, Guang Han, Guoyu Wang, Carmelo Prestipino, Pierric Lemoine, Emmanuel Guilmeau, Xu Lu, Xiaoyuan Zhou
Summary: This study proposes a new strategy to modify microstructure by phase regulation, which can simultaneously enhance carrier mobility and reduce lattice thermal conductivity. The addition of Cu in layered SnSe2 induces a phase transition that leads to increased grain size and reduced stacking fault density, resulting in improved carrier mobility and lower lattice thermal conductivity.
Article
Materials Science, Multidisciplinary
Jia Chen, Zhengyu Zhang, Eitan Hershkovitz, Jonathan Poplawsky, Raja Shekar Bhupal Dandu, Chang-Yu Hung, Wenbo Wang, Yi Yao, Lin Li, Hongliang Xin, Honggyu Kim, Wenjun Cai
Summary: In this study, the structural origin of the pH-dependent repassivation mechanisms in multi-principal element alloys (MPEA) was investigated using surface characterization and computational simulations. It was found that selective oxidation in acidic to neutral solutions leads to enhanced nickel enrichment on the surface, resulting in reduced repassivation capability and corrosion resistance.
Article
Materials Science, Multidisciplinary
X. Y. Xu, C. P. Huang, H. Y. Wang, Y. Z. Li, M. X. Huang
Summary: The limited slip systems of magnesium (Mg) and its alloys hinder their wide applications. By conducting tensile straining experiments, researchers discovered a rate-dependent transition in the dislocation mechanisms of Mg alloys. At high strain rates, glissile dislocations dominate, while easy-glide dislocations dominate at low strain rates. Abundant glissile dislocations do not necessarily improve ductility.
Article
Materials Science, Multidisciplinary
M. S. Szczerba, M. J. Szczerba
Summary: Inverse temperature dependences of the detwinning stress were observed in face-centered cubic deformation twins in Cu-8at.%Al alloy. The detwinning stress increased with temperature when the pi detwinning mode was involved, but decreased when the pi/3 mode was involved. The dual effect of temperature on the detwinning stress was due to the reduction of internal stresses pre-existing within the deformation twins. The complete reduction of internal stresses at about 530 degrees C led to the equivalence of the critical stresses of different detwinning modes and a decrease in the yield stress anisotropy of the twin/matrix structure.
Article
Materials Science, Multidisciplinary
Taowen Dong, Tingting Qin, Wei Zhang, Yaowen Zhang, Zhuoran Feng, Yuxiang Gao, Zhongyu Pan, Zixiang Xia, Yan Wang, Chunming Yang, Peng Wang, Weitao Zheng
Summary: The interaction between the electrode and the electric double layer (EDL) significantly influences the energy storage mechanism. By studying the popular alpha-Fe2O3 electrode and the EDL interaction, we find that the energy storage mechanism of the electrode can be controlled by modulating the EDL.
Article
Materials Science, Multidisciplinary
Matthew R. Barnett, Jun Wang, Sitarama R. Kada, Alban de Vaucorbeil, Andrew Stevenson, Marc Fivel, Peter A. Lynch
Summary: The elastic-plastic transition in magnesium alloy Mg-4.5Zn exhibits bursts of deformation, which are characterized by sudden changes in grain orientation. These bursts occur in a coordinated manner among nearby grains, with the highest burst rate observed at the onset of full plasticity. The most significant burst events are associated with twinning, supported by the observation of twinned structures using electron microscopy. The bursts are often preceded and followed by a stasis in peak movement, indicating a certain "birth size" for twins upon formation and subsequent growth at a later stage.
Article
Materials Science, Multidisciplinary
Vaidehi Menon, Sambit Das, Vikram Gavini, Liang Qi
Summary: Understanding solute segregation thermodynamics is crucial for investigating grain boundary properties. The spectral approach and thermodynamic integration methods can be used to predict solute segregation behavior at grain boundaries and compare with experimental observations, thus aiding in alloy design and performance control.
Article
Materials Science, Multidisciplinary
Feiyu Qin, Lei Hu, Yingcai Zhu, Yuki Sakai, Shogo Kawaguchi, Akihiko Machida, Tetsu Watanuki, Yue-Wen Fang, Jun Sun, Xiangdong Ding, Masaki Azuma
Summary: This study reports on the negative and zero thermal expansion properties of Cd2Re2O7 and Cd1.95Ni0.05Re2O7 materials, along with their ultra-low thermal conductivity. Through investigations of their structures and phonon calculations, the synergistic effect of local structure distortion and soft phonons is revealed as the key to achieving these distinctive properties.
Article
Materials Science, Multidisciplinary
Thomas Beerli, Christian C. Roth, Dirk Mohr
Summary: A novel testing system for miniature specimens is designed to characterize the plastic response of materials for which conventional full-size specimens cannot be extracted. The system has an automated operation process, which reduces the damage to specimens caused by manual handling and improves the stability of the test results. The experiments show that the miniature specimens extracted from stainless steel and aluminum have high reproducibility, and the results are consistent with those of conventional-sized specimens. A correction procedure is provided to consider the influence of surface roughness and heat-affected zone caused by wire EDM.
Article
Materials Science, Multidisciplinary
Rani Mary Joy, Paulius Pobedinskas, Nina Baule, Shengyuan Bai, Daen Jannis, Nicolas Gauquelin, Marie-Amandine Pinault-Thaury, Francois Jomard, Kamatchi Jothiramalingam Sankaran, Rozita Rouzbahani, Fernando Lloret, Derese Desta, Jan D'Haen, Johan Verbeeck, Michael Frank Becker, Ken Haenen
Summary: This study investigates the influence of film microstructure and composition on the Young's modulus and residual stress in nanocrystalline diamond thin films. The results provide insights into the mechanical properties and intrinsic stress sources of these films, and demonstrate the potential for producing high-quality nanocrystalline diamond films under certain conditions.
