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Few atom thick, twisted bilayer graphene (tBLG) possesses a rotation angle (θ) dependent van Hove singularity (vHs). Fine-tuning vHs serves a potential method to enhance charge transfer (CT) in surface enhanced Raman spectroscopy. This study shows that tBLG having a specific θ promotes as high as a 1.7 times enhancement of the Raman signals of copper phthalocyanine (CuPc) as compared to that caused by single layer graphene (SLG). The results of a combination of reflection imaging spectroscopy and widefield Raman provide spatial and spectral information about both tBLG with θ ranging from 10.9 to 13.7° and the corresponding vHs. Comparison of Raman spectra of CuPc in presence and absence of tBLG demonstrates that a significant enhancement of certain CuPc vibrational modes occurs when the underlying tBLG possesses a θ = 12.2°, showing as high as 6.8 and 1.7 times enhancements of certain vibrational mode as compared to those of CuPc on bare and SLG substrates, respectively. Theoretical calculations indicate that a match between the energies of vHs of tBLG with those of frontier orbitals of CuPc facilitates CT from the distant SLG to CuPc.

The effects of cooling rate on the microstructure and cryogenic impact toughness of coarse-grained heat-affected zone (CGHAZ) and inter-critically reheated coarse-grained HAZ (IC CGHAZ) in 9% Ni steel were investigated. CGHAZ and IC CGHAZ specimens were prepared from 9% Ni steel by controlling the cooling rate of the simulated welding process. The microstructure of the CGHAZ specimens consisted of autotempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the autotempered martensite and the effective grain size decreased. A large amount of fine carbides was distributed inside the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. The microstructure of the IC CGHAZ specimens consisted of tempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the tempered martensite and effective grain size decreased. Finer carbides were distributed inside the tempered martensite than in the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. Cryogenic fracture revealed that ductile fracture occurred in the auto-tempered martensite and tempered martensite, and brittle fracture occurred in the lath martensite. The crack propagation path was zig-zag in the high angle grain boundaries of the lath martensite. The volume fraction of auto-tempered martensite and tempered martensite and the effective grain size in the HAZ specimens had a significant effect on cryogenic impact toughness. In the IC CGHAZ specimens, cryogenic impact toughness decreased and then became constant as the cooling rate increased, due to a decrease in the volume fraction of the tempered martensite and effective grain size.

Facile construction of graphene nanostructures are potentially important for fundamental studies and various applications owing to its transparency and mechanical strength. Here we found that focused laser irradiation of a graphene/entrapped water/hydrophobic substrate leads to vaporization of entrapped water and consequent formation of graphene nanostructures. Graphene mechanically exfoliated on a hydrophobicized Si substrate was served as a transformable and impermeable nanocontainer in which water anisotropically and slowly diffuses from the weak edges into the van der Waals (vdW)-coupled interstitial volume between graphene and the substrate. Time-lapsed Raman mappings show that water entrapment promotes progressive lowering of the frequencies of the G and 2D bands of graphene and exhibits slower diffusion owing to vdW decoupling of substrate-induced doping and biaxial strain of graphene with hydrophobic substrate. Moreover, vaporized entrapped water promotes nanostructures by graphene sliding and bulging actions. This methodology represents viable approach to produce nanostructures from two dimensional materials.

Currently, power semiconductors (IGBT, Thyristor, etc.) are used for the stability and high reliability of DC system operation. However, we have proposed a current limiting DC circuit breaker with superconducting winding to improve the stability of the DC system. This is superior in terms of fast cut-off speed and economy of power semiconductors, and is suitable for changes to the Point to Loads DC system that will be expanded in the future. A superconducting DC circuit breaker is a model in which a superconducting current limiter and a DC circuit breaker are combined. The superconducting fault current limiter uses a superconducting wire made of GdBCO material to limit the initial fault current to lower the current level of the fault current, and the DC circuit breaker blocks the reduced fault current from the superconducting fault current limiter by configuring a mechanical cutoff switch, passive elements L, C and SPD. In this paper, this superconducting DC circuit breaker model was designed and tested by giving two variables, and the operating characteristics were analyzed. The first is the superconducting wire connection method, and the second is the power supply voltage. In addition, the initial fault current, the time when the zero point of the fault current is generated, and the time when the shutdown is completed were compared and analyzed. As a result, it was confirmed that the helical type showed a higher current limiting rate than the spiral type, and the result of reaching a fast current zero point was confirmed.

We have studied the operation of the circuit breaker for 15 kV DC power grid with the combination of the breaker and the HTS Fault Current Limiter (FCL). The HTS FCL limits the fault current by introduce of the impedance under the fault condition, so the circuit breaker with the HTS FCL module can be expected to be able to break the higher prospective fault current successfully. As an attached module to the DC circuit breaker, we performed a design work for a DC resistive HTS FCL module with SuNAM's REBCO conductor with the stainless-steel stabilizer. Considering the operation delay time of the DC circuit breaker, the HTS FCL module should generate a proper impedance for 16 milliseconds at most without any damages. To verify the design results, we designed and make scaled-down model of the HTS FCL module. We also carried out the DC short-circuit test to check the feasibility and the fault current limiting characteristics of the suggested model.

In this study, free-standing PIL/IL composite membranes of 1-bromohexyl-1 methylpiperidinium bromide (Br-6-MPRD) grafted poly(2,6 dimethyl 1,4 phenylene oxide) (ILPPO) incorporated with different amounts of free Br-6-MPRD (0, 2, 5 and 10 wt%) were prepared and the effect of free ionic liquid on CO2, N2 and O2 transport properties were reported. The structure of piperidinium based polyionic liquid (PIL) synthesised was confirmed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectral techniques. Gas permeation results at 1 bar pressure and 25 °C revealed the best CO2 permeability and CO2/N2 as well as CO2/O2 permselectivities of the membrane stretch to 907.20 Barrer (higher than Pebax® 1657), 12.94 and 14.90 respectively for ILPPO/Br-6-MPRD-2 which come within reach of the 2008 Robeson limit. Apart from most of the published works, ILPPO/Br-6-MPRD-2 membrane revealed an anti-trade-off permeability-selectivity performances which is most required and a great challenge for CO2 separation and capture applications.

As coaxial magnetic gears use NdFeB permanent magnets with high-energy density, they have a torque density comparable to that of mechanical gears, and active research activities have been conducted since. However, NdFeB permanent magnets have conductivity and cause high permanent magnet eddy current losses due to the driving characteristics of coaxial magnetic gears. Ferrite has no conductivity, but because of its weak magnetic force, its competitiveness is poor. In this article, Nd-bonded permanent magnet which has high magnetic force and no conductivity is used. Finite element analysis (FEA) calculations and experimental results of coaxial magnetic gears using Nd-bonded permanent magnets were compared, and the direction of applying Nd-bonded to coaxial magnetic gears was presented by comparing the magnetization method of Nd-bonded.

Anion exchange membranes (AEMs) with good alkaline stability and ion conductivity are fabricated by incorporating quaternary ammonium-modified silica into quaternary ammonium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO). Quaternary ammonium with a long alkyl chain is chemically grafted to the silica in situ during synthesis. Glycidyltrimethylammoniumchloride functionalization on silica (QSiO2) is characterized by Fourier transform infrared and transmission electron microscopic techniques. The QPPO/QSiO2 membrane having an ion exchange capacity of 3.21 meq·g–1 exhibits the maximum hydration number (λ = 11.15) and highest hydroxide ion conductivity of 45.08 × 10–2 S cm–1 at 80 °C. In addition to the high ion conductivity, AEMs also exhibit good alkaline stability, and the conductivity retention of the QPPO/QSiO2-3 membrane after 1200 h of exposure in 1 M potassium hydroxide at room temperature is about 91% ascribed to the steric hindrance offered by the grafted long glycidyl trimethylammonium chain in QSiO2. The application of the QPPO/QSiO2-3 membrane to an alkaline fuel cell can yield a peak power density of 142 mW cm–2 at a current density of 323 mA cm–2 and 0.44 V, which is higher than those of commercially available FAA-3-50 Fumatech AEM (OCV: 0.91 V; maximum power density: 114 mW cm–2 at current density: 266 mA cm–2 and 0.43 V). These membranes provide valuable insights on future directions for advanced AEM development for fuel cells.

In fuel cell and electrolysis systems, hydrogen crossover is a phenomenon where hydrogen molecules (H2) permeate through a membrane, lowering the overall process efficiency and generating a potential safety risk. Many works have been reported to mitigate this undesired phenomenon, but it is yet difficult to accurately measure the rate of hydrogen crossover, particularly when the membrane is fully wetted in water. In this work, we investigated the pressure decay method as a simple, convenient, and low-cost method to characterize hydrogen crossover through wetted membranes for water electrolysis systems. Three different ion exchange membranes were analyzed: Nafion 212, Nafion 115, and in-house sulfonated poly(arylene ether sulfone). We rigorously confirmed our method and data by comparing it to the ANSI dataset with the current state-of-the-art equations of state (EOS) to account for the nonideality of high pressure hydrogen systems. The error from the gas non-ideality was less than 0.03%. As expected, the rate of hydrogen crossover showed high dependency on the temperature; more importantly, hydrogen crossover increased significantly when the membrane was fully soaked in water. For dry membranes, the proposed pressure decay method corroborated well with the literature data measured using other known methods. Moreover, for wetted membranes, the obtained data showed high similarity compared to the GC method which is currently the most reliable method in the literature. We attempted to predict the hydrogen permeability of wetted membranes using the solution diffusion model. The model based on the given thermodynamic parameters overestimated the hydrogen permeability, which can be used to estimate the ion channel tortuosity.

Among the various cathode materials used in LIBs (Lithium ion batteries), nickel rich cathode materials have attracted an increasing amount of interest due to their high capacity, relatively low cost, and low toxicity when compared to LiCoO2. However, these materials always contain a large amount of residual lithium compounds such as LiOH and Li2CO3. The presence of lithium residues is undesirable because the oxidation of these compounds results in the formation of Li2O and CO2 gas at higher voltages, which lowers the coulombic efficiency between the charge and discharge capacities during cycling. In this study, using LiNi0.8Co0.1Mn0.1O2 as a starting material, a surface-modified cathode material was obtained by using reducing agent. The reducing agent not only plays the role of reducing the oxide conversion energy but also suppresses the side reaction with the electrolyte due to the surface modification. Residual lithium present on the cathode material surface was reduced from 11,702 ppm to 8,658 ppm, resulting in improved high temperature cycle performance and impedance characteristics.

The process of crosslinking is widely employed to increase the physicochemical stability of anion exchange membranes and, in some cases, improve ion conductivity. For a general case in which a polymer is crosslinked by a crosslinking agent, the physicochemical properties of the polymer can be greatly altered, depending on the type of crosslinking agent. In this study, we induced crosslinking without a crosslinking agent to intentionally maximise various physical properties (i.e., mechanical properties, swelling ratios, and so forth) of two commercially-available polymers. A triazole was incorporated into the conducting group to maximise the ion conductivity, especially under room humidity (RH) conditions. The crosslinked PPO-SEBS membranes prepared through this approach were not only capable of forming very thin membranes (10 μm thickness) with excellent physical properties (34.3 MPa of tensile strength and 91.6% of elongation at break) but also exhibited high hydroxide ion conductivity under 95% RH, and conductivity plays an important role in achieving good fuel cell performance. When the membrane electrode assembly (MEA), as fabricated utilising a crosslinked PPO-SEBS membrane and a platinum on carbon (Pt/C) catalyst on each electrode, was operated in conditions with a H2/O2 gas flow and a 60 °C temperature, a stable fuel cell performance was obtained for a long period of time (300 hours) at a maximum power density of 405 mW cm−2. This result surpasses the performance of commercialized AEMs and is comparable with the performance levels of cutting-edge AEMs when operated under similar conditions.

In this study, we investigated facile “dragging mode” electrohydrodynamic (EHD) jet printing of a polymer-wrapped semiconducting single-walled carbon nanotube (s-SWCNT) ink, for fabrication of NO gas-sensing field-effect transistors (FETs). The “dragging mode” provides a favorable environment for reliable printing and interconnection between the s-SWCNTs. Printing parameters such as supply voltages, printing speeds, and the number of prints were manipulated to find an optimal printing condition and obtain high-performance FETs. Under optimal conditions, the polymer-wrapped s-SWCNT-based FETs exhibited an average field-effect mobility of 2.939 cm2 (V−1 s−1), a threshold voltage of 2.21 V, an on/off ratio of ∼103, and a subthreshold swing of 0.968 V dec−1. Additionally, we demonstrated the application of FETs as NO sensors with high sensitivity and selectivity. The FET-type NO gas sensor exhibits a dynamic sensing range of 500 ppb–30 ppm and clear selectivity among various analyte gases including ethanol, ammonia, and acetone. Therefore, the “dragging mode” EHD jet printing introduced in this study simplifies patterning processes and is a potential reproducible method for the fabrication of next-generation gas sensors.

Printed electronics will be essential in the implementation of next-generation electronic devices, because printing facilitates fabrication of devices on various rigid, thin, or flexible substrates. Inkjet printing enables precise placement of fine droplets of different functional materials; moreover, it is inexpensive and adaptable for mass production. Electrohydrodynamic (EHD) jet printing, a type of inkjet technology, can generate very fine ink droplets by applying an electric field between the substrate and the nozzle; therefore, it is a promising candidate for high-resolution direct printing, which is essential in the manufacturing of various devices. More significantly, the characteristics of EHD jet printing can be conveniently adjusted by modulating the electric field strength, and various functional inks can be used in this process. This paper is a comprehensive review of recent progress in EHD jet printing technology to fabricate various electronic devices and circuits. Applications of various functional inks (electrode, semiconductor, dielectric materials) for each electronic component are also described.

We research team has proposed a current-limiting superconducting DC circuit breaker that combines a High-temperature superconducting wire (HTS) with a DC circuit breaker, and secured its operation performance in our previous study via simulation. In this paper, we designed and produced an actual current-limiting superconducting DC circuit breaker, as well as analyzed its current limiting and breaking performance. In addition, the operation characteristics at different lengths of the HTS with increasing voltage were analyzed. The operation reliability of the proposed DC circuit breaker was demonstrated by a simulation system that was built similar to the actual system.

In the coaxial magnetic gear, the permanent magnets of each rotor face each other, and the driving frequency of each rotor has different values according to the gear ratio. The magnetic flux that changes with time is transmitted to each permanent magnet. If the permanent magnet has conductivity property, losses by eddy currents are occurred in the permanent magnet. It is a major loss of a magnetic gear. Because the loss causes demagnetization by heat, it is mentioned a fatal problem at high speed. In this paper, the characteristics were analyzed by applying permanent magnets without conductivity. In addition, the analysis of the electromagnetic field as well as the mechanical loss were also considered to show which magnet type is advantageous.

We chemically modify a commercially available elastomeric triblock copolymer, poly(styrene-b-ethylene-co-butylene-b-styrene) SEBS, to produce quaternary ammonium-functionalized hexyl bis(quaternary ammonium)-mediated partially-crosslinked SEBSs with different grafting degree of the conducting head groups as highly conductive and stable anion exchange membranes (AEMs). In an attempt to achieve a high ion exchange capacity and hence conductivity of the corresponding membranes without causing ‘gelation’, which these types of SEBS polymers typically experience, we use a SEBS with a high content (57%) of styrene, and graft the quaternary ammonium (QA) as both a crosslinker and the conducting head group on the side chain of the SEBS. The partial crosslinking approach, in combination with introducing these QA-conducting head groups as the side chain of the SEBS, helps to form larger ion clusters, and also to form a nano-phase morphology with long-range connecting channels. This induced the highest ion conductivity, 174.8 mS cm−1 at 80 °C, reported to date among these types of SEBS series. In addition, we obtain excellent cell performance with a current density of 450 mA cm−2 at 0.6 V and a peak power density of 315 mW cm−2 at 95% RH and 60 °C using the corresponding AEM.

Studies on coaxial magnetic gears (CMGs) have been actively conducted. CMGs can replace mechanical gears because they can perform noncontact power transfer minimizing loss and damage from friction. In the design stage of a CMG, 2D electromagnetic finite element analysis (FEA), which is a highly reliable and cost-saving tool, is widely used. However, during prototyping and testing in the review phase of a project, the prototype's pull-out torque is lower than the pull-out torque predicted from 2D electromagnetic FEA, with up to a 40% difference. One explanation for this phenomenon is that the torsional stiffness of the pole-piece structure is low, causing the electrical angle to skew. There are high-frequency magnetic fluxes in the pole-piece structure in which magnetic losses are expected to be high. In many studies, non-metal pole-piece supports that can minimize this magnetic loss were used. The disagreement between analysis and experiment has been demonstrated, but no detailed examination of this effect has been conducted. In this study, metal pole-piece supports are used to remove the torsion possibility. Results from 3D-FEA and experiments are compared, and the results reveal that when torsion is accounted for, the analysis data can be reproduced the experimental data well or not. Furthermore, the magnetic loss on metal supports is analyzed in detail.

In this study, the operation characteristics of an interior permanent magnet synchronous motor (IPMSM) for an electric oil pump (EOP) are analyzed, based on the irreversible demagnetization of the permanent magnet due to temperature saturation. EOP motors are targeted to operate at low-speed high-torque and high-speed low-torque under low and high temperatures, respectively. Hence, the operating temperature is essential for determining the performance characteristics of these motors. Moreover, as a NdFeB type permanent magnet (PM) is utilized, the motor is vulnerable to high temperatures in terms of the irreversible demagnetization of the PM. In this study, the output performance and PM demagnetization ratio of an IPMSM is analyzed at a target ambient temperature. Subsequently, the saturation temperature for each operating point is derived using MotorCAD, which is based on a precise analysis of the thermal equivalent circuit. Finally, the IPMSM for an EOP is analyzed using the derived saturation temperature and compared to the that derived using the ambient temperature.

In this study, a new type of arc-induced DC (direct current) circuit breaker is proposed as a mechanical circuit breaker suitable for DC systems. It consists of mechanical contacts, induction needles, an induction ring, and a ground line. Powerful DC arcs are generated by the movement of the mechanical contact, but they are induced to the ground by the induction needles, and are exhausted. In this study, the cut-off characteristics of the arc-induced DC circuit breaker were analyzed using the Maxwell software. A simulation model was designed, and the electrical field distribution was analyzed according to the contact pole length. In addition, a prototype was fabricated based on the simulation results, and basic cut-off operation experiments were per-formed. As a result, it was possible to investigate the blocking characteristics of the arc-induced DC circuit breaker through the simulation and experiment. Moreover, it was confirmed that the induction needles can induce DC arcs.

Despite the many advances that have been made in using anionic surfactants to disperse and sort single-walled carbon nanotubes (SWNTs) for optoelectronic applications, one-pot methods for deposition of SWNTs in a diameter (dt) and position controlled manner from as-dispersed sample are essential. Here, we designed and prepared flavin-containing self-assembled monolayers (flavin-SAMs) that can be used to assemble dt-selective individualized SWNT networks directly from SWNT dispersions by using the widely-used anionic surfactant. For a given glass substrate, the dimethallylsilane-linked azide, along with surface immobilization was employed to have Click reaction with terminal acetylene tethered to flavin group known to have strong affinity with SWNT. As demonstrated by atomic force microscopy and other methods, along successful assembly of individualized networks, the SWNTs are either fully or partially wrapped in a dt selective manner by isoalloxazine moieties tethered to the surface, displaying Langmuir isotherm adsorption behaviors in a dipping method dependent manner. The assembled SWNT network secures photoluminescence and electrical conductivity albeit its intimacy to underlying substrate and near monolayer coverage of SWNT network, respectively, and, furthermore, preferentially takes place on flavin-SAM over hydrophobic surface.

In this study, effects of carbon and nickel on microstructure and low temperature Charpy impact properties of HSLA (high strength low alloy) steels are investigated. To understand the complex phase transformation behavior of HSLA steels with high strength and toughness before and after welding processes, three kinds of HSLA steels are fabricated by varying the carbon and nickel content. Microstructure analysis, low temperature Charpy impact test, and Vickers hardness test are performed for the base metals and CGHAZ (coarse-grain heat affected zone) specimens. The specimens with the lowest carbon and nickel content have the highest volume fraction of AF, the lowest volume fraction of GB, and the smallest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the highest. The specimens with increased carbon and nickel content have the lowest volume fraction of AF, the highest volume fraction of GB, and the largest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the lowest.

The existing DC (direct current) circuit breakers used for LVDC (low-voltage direct current) extinguish the arc by using an arc chute. The arc chute has an insulating inner barrier and cuts off the current by increasing the length of the arc and raising the arc voltage. If the arc chute fails to extinguish the arc energy by dissipating heat, the arc generation time will increase, thereby raising the possibility of damage to the cut-off contacts. Therefore, we proposed a new arc-induction type DC circuit breaker with key components like mechanical contacts, an induction needle, and a magnet. The arc generated between the contacts is guided to the induction needle and then grounded via a ground wire before being extinguished. The induction needle is a critical component of such mechanism because it induces the arc. The performance of the DC circuit breaker is determined by modifying the induction needle. In this study, the operational characteristics of the arc-induction type DC circuit breaker according to the variation of the induction needle was analyzed using the Maxwell program. The shape and position of the induction needle were changed, and the changes in the electric field were compared via simulation. As a result, the electric field value was confirmed to have been improved by up to about 20.5% when the two variables were applied.

Here we suggest a simple and novel method for the preparation of a high-performance self-humidifying fuel cell membrane operating at high temperature (&gt, 100 °C) and low humidity conditions (&lt, 30% RH). A self-humidifying membrane was effectively prepared by laminating together proton and anion exchange membranes composed of acceptor-doped SnP2O7 composites, Sn0.9In0.1H0.1P2O7/Sn0.92Sb0.08(OH)0.08P2O7. At the operating temperature of 100 °C, the electrochemical performances of the membrane electrode assembly (MEA) with this heterojunction membrane at 3.5% RH were better than or comparable to those of each MEA with only the proton or anion exchange membranes at 50% RH or higher.

In this study, a novel method for reducing the noise generated by single-phase claw-pole motors employed as refrigerator fan blowers is proposed. A single-phase claw-pole motor has the advantages of low manufacturing cost, easy manufacturing, and a high number of turns. However, in such motors, current delays occur owing to a high inductance, therefore, it is necessary to merge the back-electromotive force and current phases into the same phase using the phase advance method. Additionally, a single-phase motor exhibits dead torque and zero torque at an electrical angle of 180° owing to its electrical characteristics, and the dead torque deteriorates the average torque and torque ripple characteristics of the motor. In this study, a novel method is proposed to make the air gap asymmetrical by tilting the claw to reduce the noise generated by single-phase claw-pole motors. An asymmetric air gap allows the cogging torque to eliminate the dead torque caused by alignment torques, causing the torque ripple to decrease. To validate the effectiveness of the proposed method, the proposed model is compared with a base model via three-dimensional finite element analysis. Furthermore, the two models are manufactured and a noise test is conducted in an anechoic chamber to compare the noise difference between the two models.

Optimization and miniaturization of existing electronic devices require the development of advanced nanostructured materials with high phase and structural purity. Over the past decade, barium titanate (BaTiO3) has attracted considerable attention due to its outstanding ferroelectric and dielectric properties. The present study involved the investigation of the phase transition and structural stability of tetragonal BaTiO3 nanopowders with pseudo-cubic phase using an in-situ high resolution and high temperature X-ray diffraction method. Under ambient conditions, the coexistence the tetragonal and cubic phases with weight fractions of 75.7% and 24.3%, respectively, was determined in BaTiO3. In the temperature range of 25 °C-300 °C, phase boundaries of BaTiO3 (180 nm in size) exhibiting several phases were detected. The phase transformation behavior, relative crystal phase content, lattice parameters, crystallite size, and tetragonality of the BaTiO3 nanopowders were established by the Rietveld refinement method at the onset temperature from 25 °C to 300 °C. Up to 150 °C, the nanopowders exhibited a complete transition of the cubic phase. Additionally, a complete tetragonal to cubic transformation was accomplished by a decrease of tetragonality at 125 °C and an increase in the crystallite size at 300 °C.

Zr-based bulk amorphous alloys which were heat-treated from 673 to 1073 K were investigated, and compressive fracture mechanisms related with improvement of mechanical properties were investigated by observing how the type, size and volume fraction of crystalline particles which is generated during the heat treatment affected the fracture mode. The Zr-based bulk amorphous alloys contained nano-sized crystalline particles showed excellent mechanical properties of compressive fracture strength over 2.0 GPa and compressive plastic strain of approximately 1%. The fracture modes of the alloys are changed depending on the heat treatment temperature and their microstructure. When the alloy is heat-treated at 673 K, the nano-sized Zr2Cu particles are generated in amorphous matrix. According to the observation of fractured specimens, in the alloy heat-treated at 673 K, the fine and elongated vein patterns were well developed. The heat treatment temperature increased above Tx, the Zr2Cu particles as well as complex crystalline particles are consist in the heat-treated alloy, which lead to the brittle fracture and the alloy show the low strength of 605 MPa. In the fractured surface of the alloy, large cleavage facets were evenly developed. When the heat treatment temperature up near Tm, the size of Zr2Cu and complex crystalline particles increased to approximately 1 μm and the volume fraction of complex crystalline particles increased up to 52.3%. As the size of crystalline particles change, the size of facet decreased similarly to the size of crystalline particles. Zr-based bulk amorphous alloys which were heat-treated from 673 to 1073 K were investigated, and compressive fracture mechanisms related with improvement of mechanical properties were investigated by observing how the type and size of crystalline particles which is generated during the heat treatment affected the fracture mode. The fracture modes of the alloys are changed depending on the heat treatment temperature and their microstructure. When the alloy is heattreated at 673 K, the nano-sized Zr2Cu particles are generated in amorphous matrix. According to the observation of fractured specimens, in the alloy heat-treated at 673 K, the fine and elongated vein patterns were well developed. The heat treatment temperature increased near Tg, the Zr2Cu particles as well as complex crystalline particles are consist in the heat-treated alloy, which lead to the brittle fracture and the alloy show the low strength of 605 MPa. In the fractured surface of the alloy, large cleavage facets were evenly developed. When the heat treatment temperature up near Tm, the size of Zr2Cu and complex crystalline particles increased to approximately 1 μm.