Showing papers on "Microstructure published in 1997"
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01 Jan 1997
TL;DR: In this paper, the authors present a non-destructive testing of welds for service experience, based on the application of service experience in metallurgy and metallurgical applications.
Abstract: Developments, grades and specifications Alloy design Microstructure Forming and machining Physical and mechanical properties Corrosion Stress corrosion cracking Welding metallurgy Welding processes Weld properties Non-destructive testing of welds Applications Service experience.
449 citations
TL;DR: In this article, the authors describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al 2 O 3 / GdAlO 3 eutectic mixture.
Abstract: Monolithic ceramics are not widely used as structural materials because of their brittleness. Ceramic matrix composites, in which whiskers 1-3 or fibres 4-7 of strong ceramics such as silicon carbide or silicon nitride are embedded in a ceramic matrix, offer improved toughness and strength because the energy of cracks may be dissipated at the whisker/matrik interface. Here we describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al 2 O 3 / GdAlO 3 eutectic mixture. This composite has a microstructure in which continuous networks of single-crystal Al 2 O 3 and single-crystal GdAlO 3 interpenetrate without grain boundaries. Rather than brittle fracture, the material displays plastic deformation at 1,873K owing to dislocation motion, as in metals. The high strength and resistance to brittle failure of this material at such high temperatures augurs well for applications in mechanical engineering.
412 citations
TL;DR: In this article, the thermodynamics and kinetics of hydride formation in a nanocrystalline alloy are presented, as well as the effect of catalyst particles at the surface of the metal.
408 citations
TL;DR: In this paper, the authors reported the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure, which is 40% harder than β-Si 3N4 and is equally strong and tough.
Abstract: Silicon nitride (Si3N4) is a light, hard and strong engineering ceramic1,2. It can withstand harsh environments and support heavy loads at temperatures beyond those at which metals and polymers fail. It can also be manufactured reliably at a reasonable cost and in large quantities. There are two forms of silicon nitride3: α-Si3N4 and β-Si3N4. The former is harder, but only the latter is currently used in engineering applications, because only this form can be given a microstructure resembling a whisker-reinforced composite1,2,4, which gives it the necessary toughness and strength. Here we report the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure. This material is 40% harder than β-Si3N4 and is equally strong and tough. Its hardness (22 GPa) is exceeded only by boron carbide and diamond (which are both brittle). These properties mean that this form of α-Si3N4 should be preferred over β-Si3N4 for all engineering applications, and it should open up new potential areas in which the ceramic can be applied.
385 citations
TL;DR: In this paper, the effect of porous composite electrodes on the overall charge transfer process in solid-state devices, such as solid oxide fuel cells, is theoretically examined by taking into account various parameters such as electrolyte thickness, intrinsic charge-transfer resistance, electrode thickness, and porosity.
Abstract: The effect of porous composite electrodes on the overall charge-transfer process in solid-state devices, such as solid oxide fuel cells, is theoretically examined by taking into account various parameters such as electrolyte thickness, intrinsic charge-transfer resistance, electrode thickness, and porosity. A model is presented that accounts for ionic transport within the electrolyte, electronic conduction through electrocatalyst, and charge-transfer at the electrolyte-electrocatalyst interface. Diffusion of gaseous species in porous electrodes is assumed to be rapid so as not to be rate limiting. The conduction of electrons in the electrocatalyst is assumed to introduce negligible resistance. The activation overpotential as a function of current density is assumed to be ohmic, and an effective charge-transfer resistance is defined. The transport equations are solved numerically in two dimensions using a finite difference technique and analytically in one dimension. The analysis predicts that the use of composite electrodes in devices employing solid electrolytes can significantly increase performance under conditions where the intrinsic charge-transfer resistance is high in comparison to the area-specific resistance of the electrolyte. The results indicate a low effective charge-transfer resistance is obtained for relatively thick electrodes with a fine microstructure as long as the porosity is sufficient to ensure negligible concentration polarization.
371 citations
TL;DR: In this article, the interfacial properties between carbon fibers and surrounding matrix of a composite are drastically affected by interfacial structure, which mainly relates to the surface physico-chemistry of the fiber, which includes its surface chemical groups and microstructure, morphology, surface area, and surface free energy.
Abstract: The interfacial properties between carbon fibers and surrounding matrix of a composite are drastically affected by interfacial structure. This structure mainly relates to the surface physico-chemistry of the fiber, which includes its surface chemical groups and microstructure, morphology, surface area, and surface free energy. These properties can be changed by various surface treatments, including various dry and wet oxidation steps, plasma treatment, electrodischarge, and fiber sizing or coating. These methods improve the interfacial properties significantly and synergistically, although each treatment has its specific application area.
285 citations
277 citations
TL;DR: In this article, single-crystal thin films of Pb(ZrxTi1−x)O3 (PZT) covering the full compositional range (0⩽x ⩽1) were deposited by metal-organic chemical vapor deposition.
Abstract: Single-crystal thin films of Pb(ZrxTi1−x)O3 (PZT) covering the full compositional range (0⩽x⩽1) were deposited by metal-organic chemical vapor deposition. Epitaxial SrRuO3(001) thin films grown on SrTiO3(001) substrates by rf-magnetron sputter deposition served as template electrode layers to promote the epitaxial growth of PZT. X-ray diffraction, energy-dispersive x-ray spectroscopy, atomic force microscopy, transmission electron microscopy, and optical waveguiding were used to characterize the crystalline structure, composition, surface morphology, microstructure, refractive index, and film thickness of the deposited films. The PZT films were single crystalline for all compositions exhibiting cube-on-cube growth epitaxy with the substrate and showed very high degrees of crystallinity and orientation. The films exhibited typical root mean square surface roughness of ∼1.0–2.5 nm. For tetragonal films, the surface morphology was dominated by grain tilting resulting from ferroelectric domain formation. We r...
257 citations
TL;DR: In this paper, the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats were studied with respect to the macrostructure and microstructure.
Abstract: Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.
250 citations
TL;DR: In this article, nanocrystalline TiC/amorphous carbon (a-C) composite films were synthesized at near room temperature with a hybrid process combining laser ablation of graphite and magnetron sputtering of titanium.
Abstract: Nanocrystalline TiC/amorphous carbon (a-C) composite films were synthesized at near room temperature with a hybrid process combining laser ablation of graphite and magnetron sputtering of titanium. Film microstructure was investigated by x-ray photoelectron spectroscopy, x-ray diffraction analyses, and transmission electron microscopy. Mechanical properties were evaluated from nanoindentation, scratch, and friction tests. The films consisted of 10 nm sized TiC crystallites encapsulated in a sp3 bonded a-C matrix. They had a hardness of about 32 GPa and a remarkable plasticity (40% in indentation deformation) at loads exceeding their elastic limit. They were also found to have a high scratch toughness in addition to a low (about 0.2) friction coefficient. The combination of hardness and ductility was correlated with film phase composition and structural analyses, using concepts of nanocomposite mechanics. The properties of the TiC/a-C composites make them beneficial for surface wear and friction protection.
242 citations
TL;DR: In this paper, a series of unlubricated sliding wear tests in air with pins of cemented carbide composites sliding against silicon nitride disks was performed, and the wear rate was proportional to the hardness with a wear coefficient k = 6.9 × 10 −6 for all materials.
TL;DR: In this article, the intermetallic compound Mg2Ni was mechanically ground under a hydrogen atmosphere to synthesize a nanostructured composite material that is composed of nanocrystalline intra-grain and disordered inter-grain regions.
TL;DR: In this article, a method for preparation of zein films involving plasticization of vein with oleic acid to form an intermediate moldable resins was presented, where the resin was stretched over rigid frames to form thin membranes that were set in flexible films.
Abstract: A new method for preparation of zein films involving plasticization of zein with oleic acid to form an intermediate moldable resin was presented. The resin was stretched over rigid frames to form thin membranes that were set in flexible films. The objective of the study was to investigate the effect of film preparation method on film properties. Tensile properties, microstructure, and thermal behavior of zein films plasticized with oleic acid were investigated for films prepared by conventional casting from ethanol solutions and by stretching of plasticized resins. Cast films were stiff and brittle, whereas resin films showed more flexibility and toughness. Differential scanning calorimetry thermograms of cast films indicated phase separations were generated when heated that were not observed for resin films. Microstructure images showed a higher degree of structure development and orientation in resin than in cast films. Glass-transition temperatures of resin films were measured at -94 and 104.4...
TL;DR: In this paper, the authors investigated the interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, SrxLa1-xMnO3 (SLM), with respect to its electrochemical performance.
Abstract: The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, SrxLa1–xMnO3 (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterized by grain size and coverage of SLM on the electrolyte surface. Variation of the grain size was obtained by using three different sintering temperatures, whereas variation of the coverage was obtained by using two powders with a different morphology. This resulted in a set of six cathode/electrolyte samples with different combinations of grain size and SLM coverage at the interface. The cathode overpotential, as a measure for the electrochemical performance, could not be related to the length of the three-phase boundary. Based on the constriction resistance occurring in the electrolyte a model was developed which provides an estimate for the width of the active three-phase boundary zone.This zone is most likely to extend outside the cathode particle across the zirconia surface. The width calculated in this way was found to vary in the range of 0.03 to 0.07 µm for the different electrode microstructures. It is argued that the actual values may be smaller by one or two orders of magnitude.
TL;DR: In this paper, the compositional dependence of magnetic properties, electrical resistivity, and structure have been almost clarified for high resistive Fe-M-O (M=Hf, Zr, rare-earth metals) films.
Abstract: Microstructure, soft magnetic properties, and applications of high resistive Fe-M-O (M=Hf, Zr, rare-earth metals) were studied. The Fe-M-O films are composed of bcc nanograins and amorphous phases with larger amounts of M and O elements which chemically combine each other. Consequently, the amorphous phases have high electrical resistivity. The compositional dependence of magnetic properties, electrical resistivity, and structure have been almost clarified. For example, the high magnetization of 1.3 T, high permeability of 1400 at 100 MHz and the high electrical resistivity of 4.1 μΩ m are simultaneously obtained for as-deposited Fe62Hf11O27 nanostructured film fabricated by rf reactive sputtering in a static magnetic field. Furthermore, Co addition to Fe-M-O films improves the frequency characteristics mainly by the increase in the crystalline anisotropy of the nanograins. The Co44.3Fe19.1Hf14.5O22.1 film exhibits the quality factor (Q=μ′/μ′′) of 61 and the μ′ of 170 at 100 MHz as well as the high Is of ...
02 May 1997-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the basic mechanisms of thin film growth under ion irradiation in the ion energy range below 1 keV are described on an atomic level, with the dependence of the microstructure, such as grain size and orientation, and density of films on the process parameters ion-to-atom arrival ratio, angle of incidence, average deposited energy, and ion energy.
Abstract: Low-energy ion bombardment during growth of thin films from the vapour phase exerts a strong influence on the properties of the films, particularly their microstructure. The basic mechanisms of film growth under ion irradiation in the ion energy range below 1 keV are described on an atomic level. The dependence of the microstructure, such as grain size and orientation, and density of films on the process parameters ion-to-atom arrival ratio, angle of incidence, average deposited energy, and ion energy is discussed with recent results from the literature with silver as an example for a metal, germanium as a semiconductor and titanium nitride as a ceramic compound film.
TL;DR: In this article, the authors evaluate the sources of energy available to drive microstructure changes in thin films, both during and after deposition, and discuss the prospects for controlling the micro-structure of thin film interconnection metals as linewidths are predicted to decrease below 0.1 μm by the year 2010.
Abstract: The microstructure of semiconductor metallization is becoming increasingly important as linewidths decrease below 0.5 μm. At these dimensions, reliability and performance are greatly influenced by specific microstructural features rather than only by the average material properties. In this article, we address the prospects for controlling the microstructure of thin film interconnection metals as linewidths are predicted to decrease below 0.1 μm by the year 2010. First, we evaluate the sources of energy available to drive microstructure changes in thin films, both during and after deposition. The internal energy sources considered are grain boundaries, interfaces, surfaces, strain, solidification, crystallization, solute precipitation, and phase transformations, with energy densities ranging from less than 1 meV/atom to greater than 100 meV/atom. The external energy sources considered are particle bombardment during deposition, mechanical deformation, and radiation damage, which may deliver energies greater than 100 eV/atom. Second, we review examples of microstructure changes in terms of these energy sources. These examples include the dependence of Al–Cu and Ti fiber texture on the roughness of SiO2, orientation change and abnormal Cu grain growth coupled to the precipitation of Co in Cu–Co alloys, and in-plane orientation selection during phase transformation of TiSi2 in very narrow lines. A substantial degree of microstructure control is also achieved in films deposited with off-normal incidence energetic particle bombardment, which has been used to produce both in-plane and out-of-plane crystallographic orientations in metals (Mo, Nb), nitrides (AlN), and oxides (ZrO2). Drawing on these examples, we discuss the prospects for microstructure control in future semiconductor metallization with respect to the list of energy sources, the decreasing dimensions, and the changing fabrication processes. One mechanism in particular, discontinuous precipitation of supersaturated solute atoms, is highlighted as having a substantial amount of stored energy available to drive microstructure evolution, and may provide a means to more fully control the microstructure of semiconductor metallization.
TL;DR: In this paper, the evolution of deformation microstructure in medium to high stacking fault energy fcc metals has been described in terms of a general framework of grain subdivision involving the formation of rotates volume elements for all deformation modes.
TL;DR: In this paper, the temperature dependence of the electric conductance of the elements made of nanocrystalline α -Fe 2 O 3 showed that the gas-sensing properties are strongly related to its surface.
Abstract: α -Fe 2 O 3 ultra-fine powder with an average particle size of 6–26nm has been prepared by a sol-gel process. Thermal analysis, X-ray diffraction and transmission electron microscope were used to study its formation process and micro-structure. The temperature dependence of the electric conductance of the elements made of nanocrystalline α -Fe 2 O 3 shows that the gas-sensing properties are strongly related to its surface. The elements exhibited good sensitivity and selectivity to ethyl alcohol, indicating it is a promising alcohol-sensing material.
TL;DR: In this paper, transparent zinc oxide (ZnO) films were grown by galvanostatic cathodic deposition onto conductive glasses from a simple aqueous zinc nitrate electrolyte maintained at 335 K.
Abstract: Transparent zinc oxide (ZnO) films have been grown by galvanostatic cathodic deposition onto conductive glasses from a simple aqueous zinc nitrate electrolyte maintained at 335 K. The as-deposited ZnO films were characterized with Fourier transform infrared absorption spectroscopy, x-ray diffraction, scanning electron microscopy, optical transmission and absorption studies, and measurement of sheet resistivity as a function of cathodic current density. The ZnO films prepared had a wurtzite structure and exhibited an optical bandgap energy of 3.3 eV which is characteristic of ZnO. At a low cathodic current density of 0.05 mA/cm{sup 2}, ZnO films with excellent electrical characteristics have been obtained. A 2 {micro}m thick ZnO film with an optical transmittance of 72% was deposited by electrolysis for approximately 20 min at a cathodic current density of 10 mA/cm{sup 2}.
TL;DR: In this paper, the carbide size and cobalt content of thermally sprayed tungsten carbide/cobalt coatings (WC-Co) can influence their microstructure, fracture strength, friction response and abrasion resistance.
Abstract: The carbide size and cobalt content of thermally sprayed tungsten carbide/cobalt coatings (WC-Co) can influence their microstructure, fracture strength, friction response and abrasion resistance. In this paper, these properties have been determined for one commercially available and three experimental WC-17 wt.% Co thermally sprayed coatings. The experimental coatings were processed from starting powders containing median carbide size distributions of 1.2, 3.8 and 7.9μm, respectively. All the coatings were produced using a high velocity oxy-fuel (HVOF) spray process. The present results indicate that coatings with a higher percentage of finer carbide size distribution in the starting powder display a higher degree of decomposition of the WC phase to W2C phase and, consequently, display lower fracture toughness and abrasion resistance values. Unidirectional, unlubricated sliding wear tests did not reveal major differences in the sliding wear response of the coatings as a function of carbide size. The micro...
TL;DR: In this paper, the fabrication of thin films of In2O3 from an aqueous sol and an organic solution was reported. And the electrical properties of the films derived from the two systems were discussed based on the differences in their morphologies.
Abstract: This article reports the fabrication of thin films of In2O3 from an aqueous sol and an organic solution. The stability of the aqueous sol with respect to the concentration of indium and pH are discussed. Thermo-gravimetric and differential thermal analysis were performed on the dried sol particles as well as the gel for better understanding of thermal events occurring during the sintering process. Microstructure, phase purity, optical, and electrical properties of the thin films deposited on glass substrates by dip-coating process from aqueous sol and organic solution were studied by transmission electron microscopy, x-ray diffractometry, visible light spectrometry, and the four-probe method, respectively. The electrical properties of the films derived from the two systems are discussed based on the differences in their morphologies.
TL;DR: In this paper, two kinds of oxidation (passive and active) and active-to-passive transition of silicon-based ceramics were discussed thermodynamically, and the rate constants of passive/active oxidation and active topassive oxygen potentials for SiC and Si 3 N 4 were reviewed.
Abstract: Oxidation behavior of silicon-based ceramics such as SiC and Si 3 N 4 at high temperatures is important for their practical applications to structural or electronic materials. In the present paper two kinds of oxidation (passive and active) and active-to-passive transition of silicon-based ceramics were discussed thermodynamically, and the rate constants of passive/active oxidation and active-to-passive transition oxygen potentials for SiC and Si 3 N 4 were reviewed. Passive and active oxidation behavior depended on the microstructure of oxide films and SiO gas pressure on silicon-based ceramics, respectively. Wagner model, volatility diagram and solgasmix-based calculation were used to estimate the active-to-passive transition.
01 Jan 1997
TL;DR: In this paper, a series of oxide-dispersed β-NiAl alloys were oxidized in order to explore the effect of various cation dopants on the ϕ-α phase transformation in the Al2O3 scale.
Abstract: A series of oxide-dispersedβ-NiAl alloys were oxidized in order to explore the effect of various cation dopants on the ϕ-α phase transformation in the Al2O3 scale and the effect of phase composition on the scale microstructure. Larger ions such as Y, Zr, La, and Hf appeared to slow theϕ- toα-Al2O3 phase transformation, while a smaller ion, Ti, appeared to accelerate the transformation.
TL;DR: In this article, a concept for the design of thermodynamically stable superhard nanocrystalline composite materials is presented and verified experimentally on three systems: nc-TiN/a-Si 3 N 4, ncVN/A-Si3 N 4 and ncW 2 N/a -Si 3N 4.
Abstract: We present recent results on the preparation of stoichiometric C 3 N 4 and its hardness which is far below the theoretically expected value. A comparison with the turbostratic substoichiometric CN 0.2–0.35 films prepared by Sundgren et al. shows the dominant importance of the microstructure. Based on some general rules a concept for the design of thermodynamically stable superhard nanocrystalline composite materials is presented and verified experimentally on three systems: nc-TiN/a-Si 3 N 4 , nc-VN/a-Si 3 N 4 and nc-W 2 N/a-Si 3 N 4 . Hardness of about 5000 kg mm −2 (about 50 GPa) or more and a high elastic modulus of 550 GPa were found in all these systems.
TL;DR: In this article, an idealized model for the microstructure of thermally sprayed ceramic coatings, consisting of the stacking of lamellae a few micrometres thick, has been used to estimate Young's modulus of the coating perpendicular to the coating plane.
Abstract: An idealized model for the microstructure of thermally sprayed ceramic coatings, consisting of the stacking of lamellae a few micrometres thick, has been used to estimate Young’s modulus of the coating perpendicular to the coating plane. A theoretical relationship between Young’s modulus and the microstructural parameters has been established. There are two components of elastic strain of the coating under tensile stress, one arising from localized elastic strain at the regions of real-bonded area between lamellae, and the other arising from elastic bending of the lamellae between bonded regions. The bending component only becomes significant for a percentage bonding ratio between lamellae of less than 40%. The bending strain contribution depends strongly upon geometrical parameters of the coating microstructure. The estimated Young’s modulus for a typical alumina coating, based on quantitative microstructural data, was about 24% of that for the fully dense material. Taking into account the variable proportion of α-Al2O3 and γ-Al2O3 forms in an alumina coating, the comparison of the estimated Young’s modulus with published data gives reasonable agreement for the coating prepared over a wide range of processes and experimental conditions.
TL;DR: In this paper, the diffusion coefficient of an appropriate solvent in these materials was evaluated and the initial uptake of solvent exhibits a square root dependence in time as a consequence of Fick's law and permit to evaluate the effective diffusion coefficient in the range 10−11−10−12 m2
Abstract: Dielectric and physicochemical properties of a composite material prepared by incorporating carbon black particles into a polymer matrix were investigated. Two types of carbon blacks, having very different structures of aggregates, were used. The volume fraction of the carbon blacks ranged from 0.2% to 7%, i.e. below and above the percolation threshold concentration observed from the measurements of dc conductivity. The composite samples were characterized in terms of: swelling by a compatible solvent, electron paramagnetic resonance (EPR) response, and frequency variation of permittivity. First, the article attempts to evaluate the diffusion coefficient of an appropriate solvent in these materials. Sorption kinetics experiments with toluene indicate that the initial uptake of solvent exhibits a square root dependence in time as a consequence of Fick’s law and permit to evaluate the effective diffusion coefficient in the range 10−11–10−12 m2 s−1 depending on the volume fraction of the carbon black in the ...
TL;DR: In this article, two types of refined structure are distinguished by optical and transmission electron microscopy, one is created through intense deformation (four extrusion passes through a 90° die, e = 4.62) by dynamic rotational recrystallization and is a well-formed grain (fragmented) structure with a mean fragment or grain size of 0.2-0.4 μm.
Abstract: Submicrometer-grained (SMG) microstructures are produced in an Al–Mg–Si alloy (6061) by subjecting peak-aged and overaged billets of the alloy to intense plastic strain by a process known as equal channel angular extrusion. Two types of refined structure are distinguished by optical and transmission electron microscopy. One structure is created through intense deformation (four extrusion passes through a 90° die, e = 4.62) by dynamic rotational recrystallization and is a well-formed grain (fragmented) structure with a mean fragment or grain size of 0.2–0.4 μm. The other structure is produced by post-extrusion annealing through static migration recrystallization, resulting in a grain size of 5–15 μm. Intense deformation of peak-aged material to a true strain e of 4.62 (four passes) produces a strong, ductile, uniform, fine, and high angle grain boundary microstructure with increased stability against static recrystallization as compared to the overaged material.
TL;DR: In this paper, a detailed analysis of the crystal structures and the growth morphologies of both TiB and TiB2 has been carried out, and the diffusion mechanisms for B atoms in both materials have been identified as vacancy diffusion.
Abstract: Interfacial reaction between titanium matrix and reinforcement plays a crucial role in determining the mechanical properties of titanium metal matrix composite materials In order to improve the mechanical properties of composite materials, it is essential to understand the thermodynamics and kinetics of such interfacial reactions Ti-6Al-4V foils and C/TiBx-coated SiC fibres were used to fabricate composite materials by diffusion bonding The interface formed after annealing at different temperatures has been characterized mainly by scanning and transmission electron microscopies to establish the reaction kinetics between the TiBx coating and Ti matrix It is found that the major reaction product is TiB needles, although a TiB2 layer is also present as a transition phase during the initial stage of the reaction Experimental results indicate that, at a temperature between 870 and 970°C, the growth rate of TiB needles along the needle direction is more than six times of that of the TiB2 layer After a detailed analysis of the crystal structures and the growth morphologies of both TiB and TiB2, the diffusion mechanisms for B atoms in TiB and TiB2 have been identified as vacancy diffusion However, the low activation energy path for B diffusion in TiB is in the [0 1 0]TiB direction, effectively one-dimensional, while that in TiB2 is along 〈 1 1 ¯ 00 Ȳ T i B 2 directions, which form a two-dimensional network In addition, it is found that the estimated diffusion coefficient for B in TiB along the needle direction is about 45 times larger than that in TiB2, although the activation energies for B diffusion in both TiB and TiB2 are effectively the same, being 187–190 kJ mol−1