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Micro/nano-textured Si wafers manufactured using metal-assisted chemical etching (MACE) have been the focus of several studies, but the mechanism of bubble generation during the MACE process affecting textured surfaces has rarely been reported. This study investigated the bubble effect due to the different placement patterns of the Si wafer (face-up, stirred face-down, and face-down). The results indicated that the placement pattern of the Si wafer notably influences the uniformity of outward appearance. At 2 h of etching, the outward appearance uniformity of face-up etching was more homogeneous than that of stirred face-down and face-down patterns, and the Si nanowires (SiNWs) processed through face-up etching were longer (41 μm) than those subjected to stirred face-down etching (36 μm) and face-down etching (32 μm). Therefore, the placement pattern of Si wafer can affect the uniformity and properties of SiNWs because of bubbles trapped inside cavities or between SiNWs.

Mineral trioxide aggregates (MTA) have been widely used in endodontic treatments, but after some time, patients suffer tooth discoloration due to the use of bismuth oxide (Bi2O3) as a radiopacifier. Replacement of Bi2O3 with high energy ball-milled single (zirconia ZrO2; hafnia, HfO2; or tantalum pentoxide, Ta2O5) or binary oxide powder was attempted, and corresponding discoloration improvement was investigated in the present study. Bi2O3-free MTA is expected to exhibit superior discoloration. The radiopacity, diametral tensile strength, and discoloration of MTA-like cements prepared from the as-milled powder were investigated. Experimental results showed that MTA-like cements prepared using Ta2O5 exhibited a slightly higher radiopacity than that of HfO2 but had a much higher radiopacity than ZrO2. Milling treatment (30 min to 3 h) did not affect the radiopacities significantly. These MTA-like cements exhibited superior color stability (all measured ΔE00 < 1.0) without any perceptible differences after UV irradiation. MTA-like cements prepared using ZrO2 exhibited the best color stability but the lowest radiopacity, which can be improved by introducing binary oxide. Among the investigated samples, MTA-like cement using (ZrO2)50(Ta2O5)50 exhibited excellent color stability and the best overall performance with a radiopacity of 3.25 mmAl and a diametral tensile strength of 4.39 MPa.

Among the various phases of bismuth oxide, the high temperature metastable face-centered cubic δ phase attracts great attention due to its unique properties. It can be used as an ionic conductor or an endodontic radiopacifying material. However, no reports concerning tantalum and bismuth binary oxide prepared by high energy ball milling and serving as a dental radiopacifier can be found. In the present study, Ta2O5-added Bi2O3 composite powders were mechanically milled to investigate the formation of these metastable phases. The as-milled powders were examined by X-ray diffraction and scanning electron microscopy to reveal the structural evolution. The as-milled composite powders then served as the radiopacifier within mineral trioxide aggregates (i.e., MTA). Radiopacity performance, diametral tensile strength, setting times, and biocompatibility of MTA-like cements solidified by deionized water, saline, or 10% calcium chloride solution were investigated. The experimental results showed that subsequent formation of high temperature metastable β-Bi7.8Ta0.2O12.2, δ-Bi2O3, and δ-Bi3TaO7 phases can be observed after mechanical milling of (Bi2O3)95(Ta2O5)5 or (Bi2O3)80(Ta2O5)20 powder mixtures. Compared to its pristine Bi2O3 counterpart with a radiopacity of 4.42 mmAl, long setting times (60 and 120 min for initial and final setting times) and 84% MG-63 cell viability, MTA-like cement prepared from (Bi2O3)95(Ta2O5)5 powder exhibited superior performance with a radiopacity of 5.92 mmAl (the highest in the present work), accelerated setting times (the initial and final setting time can be shortened to 25 and 40 min, respectively), and biocompatibility (94% cell viability).

The effects of synthesis time on the plasmonic properties of Ag dendritic nanoforests on Si substrate (Ag-DNF/Si) samples synthesized through the fluoride-assisted galvanic replacement reaction were investigated. The Ag-DNF/Si samples were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, reflection spectroscopy, X-ray diffraction and surface-enhanced Raman spectroscopy (SERS). The prolonged reaction time led to the growth of an Ag-DNF layer and etched Si hole array. SEM images and variations in the fractal dimension index indicated that complex-structure, feather-like leaves became coral-like branches between 30 and 60 min of synthesis. The morphological variation during the growth of the Ag DNFs resulted in different optical responses to light illumination, especially those of light harvest and energy transformation. The sample achieved the most desirable light-to-heat conversion efficiency and SERS response with a 30 min growth time. A longer synthesis time or thicker Ag-DNF layer on the Si substrate did not have superior plasmonic properties.

Mineral trioxide aggregate (MTA) typically consists of Portland cement (75 wt.%), bismuth oxide (20 wt.%), and gypsum (5 wt.%) and is commonly used as endodontic cement. Bismuth oxide serving as the radiopacifying material reveals the canal filling effect after clinical treatment. In the present study, bismuth/zirconium oxide composite powder was prepared by high energy ball milling of (Bi2O3)100&minus, x (ZrO2)x (x = 5, 10, 15, and 20 wt.%) powder mixture and used as the radiopacifiers within MTA. The crystalline phases of the as-milled powders were examined by the X-ray diffraction technique. The radiopacities of MTA-like cements prepared by using as-milled composite powders (at various milling stages or different amount of zirconia addition) were examined. In addition, the stability of the as-milled powders stored in an ambient environment, an electronic dry box, or a glove box was investigated. The experimental results show that the as-milled powder exhibited the starting powder phases of Bi2O3 and ZrO2 and the newly formed &delta, Bi7.38Zr0.62O2.31 phase. The longer the milling time or the larger the amount of the zirconia addition, the higher the percentage of the &delta, Bi7.38Zr0.62O2.31 phase in the composite powder. All the MTA-like cements prepared by the as-milled powder exhibited a radiopacity higher than 4 mmAl that is better than the 3 mmAl ISO standard requirement. The 30 min as-milled (Bi2O3)95(ZrO2)5 composite powder exhibited a radiopacity of 5.82 &plusmn, 0.33 mmAl and degraded significantly in the ambient environment. However, storing under an oxygen- and humidity-controlled glove box can prolong a high radiopacity performance. The radiopacity was 5.76 &plusmn, 0.08 mmAl after 28 days in a glove box that was statistically the same as the original composite powder.

This paper reports the preparation and wear behavior of mechanically alloyed Ti-based bulk metallic glass composites containing carbon particles. The carbon/Ti 50 Cu 28 Ni 15 Sn 7 metallic glass composite powders are formed by two-stage mechanical alloying (MA) process. The bulk metallic glass composite was successfully prepared by vacuum hot pressing of as-milled carbon/Ti 50 Cu 28 Ni 15 Sn 7 metallic glass composite powders. The differential scanning calorimeter (DSC) results show that the thermal stability of the amorphous matrix is affected by the presence of the carbon particles. Changes in T g and T x suggest deviations in the chemical composition of the amorphous matrix that were developed due to a partial dissolution of the carbon species into the amorphous phase. Although the hardness of carbon/Ti 50 Cu 28 Ni 15 Sn 7 bulk metallic glass composite is increased with carbon addition, but their wear resistances is not directly proportional to hardness and does not follow the standard wear law. The increase in the wear rate of a carbon/Ti 50 Cu 28 Ni 15 Sn 7 bulk metallic glass composite with high carbon content may be attributed to the residual porosity and in-situ formed hard TiC particles formed in situ in the matrix of the composite.

In the present study, Cu60Zr30Ti10 metallic glass powders were prepared by mechanical alloying of pure Cu, Zr, and Ti powder mixtures. Cu60Zr30Ti10 metallic glass composite powders were obtained after 5 h of milling as confirmed by X-ray diffraction and transmission electron microscopy. The metallic glass powders were found to exhibit a supercooled liquid region before crystallization. Cu60Zr30Ti10 bulk metallic glass were synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass powders at 723 K in the pressure range of 0.72 ~ 1.20 GPa. Cu60Zr30Ti10 BMG with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix was successfully prepared under applied pressures. It was found that the pressure could enhance the thermal stability and prolong the existence of amorphous phase inside Cu60Zr30Ti10 powders.

High-temperature face-centered cubic bismuth oxide phase is a material of great interest given its unique properties. In the present study, α-Bi2O3 and tantalum powders were used as the starting powders for the formation of high-temperature bismuth oxide phase via mechanochemical synthesis by high energy ball milling. (Bi2O3)80(Ta)20 and (Bi2O3)95(Ta)5 in weight concentrations were milled in either an oxygen-free argon-filled glove box environment or an ambient atmosphere to investigate the effects of oxygen concentration and tantalum addition. The as-milled powders were examined using X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and differential scanning calorimetry to reveal the structural evolution. The experimental results showed that for (Bi2O3)95(Ta)5 powder mixtures milled within the glove box, tantalum gradually reacted with the α-Bi2O3 phase and formed a β-Bi7.8Ta0.2O12.2 phase. For (Bi2O3)80(Ta)20 milled under the same conditions, Ta and α-Bi2O3 mechanochemically reacted to form δ-Bi3TaO7 and bismuth after 10 min of high energy ball milling, whereas milling (Bi2O3)80(Ta)20 under the ambient atmosphere with a much higher oxygen concentration accelerated the mechanochemical reaction to less than five minutes of milling and resulted in the formation of high-temperature δ-Bi3TaO7 phase.

Droplet-based microfluidics is a colloidal and interfacial system that has rapidly progressed in the past decade because of the advantages of low fabrication costs, small sample volumes, reduced analysis durations, high-throughput analysis with exceptional sensitivity, enhanced operational flexibility, and facile automation. This technology has emerged as a new tool for many recently used applications in molecular detection, imaging, drug delivery, diagnostics, cell biology and other fields. Herein, we review recent applications of droplet microfluidics proposed since 2013.

Two types of Bi0.4Sb1.6Te3 powder exhibiting particle and grain-size differences were fabricated using a high-energy ball milling process. The mixtures at different ratios were consolidated by vacuum hot pressing to produce nano-/micro-structured composites with the same chemical compositions. Measurements of the Seebeck coefficient, electrical resistivity, and thermal conductivity provided a ZT value as high as 1.19 at 373 K for a sample containing 40% nanograin powders. This ZT value is higher than that of the monolithic nanostructured Bi0.4Sb1.6Te3 sample. The ZT values of this sample at a temperature ranging between 400 and 495 K are between 1.0 and 1.1. Such ZT characteristics make the ZT value suitable for power generation applications because no other materials with a similarly high ZT value have been observed in this temperature range. The achieved higher ZT value is potentially attributed to the unique nano-/micro-structures, in which the dispersed nanograin powders can increase phonon scattering sites and reduce thermal conductivity. Furthermore, the existence of micropowders can provide fast carrier transportation network that enhances electrical conductivity. The results indicated that the nano-/micro-structured Bi0.4Sb1.6Te3 alloy can serve as a high-performance material for application in thermoelectric (TE) devices.

Two kinds of Bi0.4Sb1.6Te3 powder with different particle and grain sizes were fabricated by high-energy ball milling. Powder mixtures with varied weight ratios were consolidated by vacuum hot pressing (HP) to produce nano/ microstructured composites of identical chemical composition. From measurements of the Seebeck coefficient, electrical resistivity, and thermal conductivity of these composites, a figure of merit (ZT) value of up to 1.19 was achieved at 373 K for the sample containing 40% nanograin powder. This ZT value is higher than that of monolithic nanostructured Bi0.4Sb1.6Te3. It is further noted that the ZT value of this sample in the temperature range of 450 K to 575 K is in the range of 0.7 to 1.1. Such ZT characteristics are suitable for power generation applications as no other material with a similar high ZT value in this temperature range has been observed until now. The achieved high ZT value can probably be attributed to the unique nano/microstructure, in which the dispersed nanograin powder increases the number of phonon scattering sites, which in turn results in a decrease of the thermal conductivity while simultaneously increasing the electrical conductivity, owing to the existence of the microsized powder that can provide a fast carrier transportation network. These results indicate that the nano/microstructured Bi0.4Sb1.6Te3 alloy can serve as a high-performance material for application in thermoelectric devices.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Ge1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Ge1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 761 K and 839 K, respectively. The supercooled liquid region ΔT is 78 K. The appearance of wide supercooled liquid region may be mainly due to the Ge additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Ge1 powders.

The oxidation behavior of a Ti 50 Cu 28 Ni 15 Sn 7 bulk metallic glass (TC4-BMG) was studied over the temperature range of 400–500 °C in dry air. The oxidation kinetics generally followed the parabolic-rate law, and the oxidation rates increased with increasing temperature. The scales formed on the TC4-BMG consisted mostly of TiO 2 (rutile structure) intermixed with small amounts of CuO particles. It was found that the scaling rate of the amorphous alloy was slightly faster than that of the crystalline counterpart. The amorphous substrate transferred into the three crystalline phases of Ti 3 Sn, Ti 3 Cu 4 , and Ti(Ni,Cu) during the oxidation at 400–500 °C, indicating the occurrence of phase transformation.

In the present study, Ti50Cu28Ni15Sn7 metallic glass and its composite powders reinforced with 4–12 vol.% of Al2O3 added were successfully prepared by mechanical alloying. In the ball-milled composites, an amorphous matrix with a homogeneous dispersion of Al2O3 particles was developed. The metallic glass composite powders were found to exhibit a large supercooled liquid region before crystallization. The presence of Al2O3 particles did not change the glass formation ability of the amorphous Ti50Cu28Ni15Sn7 powders. Consolidation of the as-milled Ti50Cu28Ni15Sn7 composite powders was performed at a temperature slightly higher than the glass transition temperature under a pressure of ∼1.2 GPa; using this method, the bulk metallic glass composite discs were prepared successfully. However, partial crystallization of the amorphous matrix during the hot-pressing process was noticed. The fracture strength of consolidated composite compacts was increased with Al2O3 additions. The pre-existing particle boundaries may serve as the crack initiation sites which resulted in the brittle failure of the Ti50Cu28Ni15Sn7 BMG composites.

Nanocrystalline iron-added manganese oxide powders were prepared by spray pyrolysis (SP) from manganese acetate and iron nitrate solutions at 400 °C. The as-obtained powders were subsequently deposited onto graphite substrates via an electrophoretic deposition technique (EPD). The as-prepared powders were examined by transmission electron microscopy (TEM) and X-ray diffractometry (XRD); the electrochemical properties of the coatings were further examined by cycling voltammetry (CV). Structural investigation by TEM and XRD revealed that the as-deposited coatings exhibited Mn3O4 phase with nanocrystalline structure. CV examinations showed that the iron addition significantly improved the electrochemical properties of the Mn-oxide powder coatings. The specific capacitance of as-deposited Mn-oxide coating was increased from 202 F/g to 232 F/g when 2 at.% of iron was added. Even after 1200 cycles of life test, the iron-added coatings exhibited higher cycling efficiency (~ 78% of the initial maximum capacitance) than that unadded one (~ 60% of its maximum value).

In the present study, Ti 50 Cu 28 Ni 15 Sn 7 (at.%) metallic glass and its composite powders reinforced with 4-12 vol.% of added SiC were successfully prepared by mechanical alloying. In the ball-milled composites, an amorphous matrix with a homogeneous dispersion of SiC particles was developed. The metallic glass composite powders were found to exhibit a large supercooled liquid region before crystallization. The presence of SiC particles did not change the glass-formation ability of the amorphous Ti 50 Cu 28 Ni 15 Sn 7 powders. Consolidation of the as-milled Ti 50 Cu 28 Ni 15 Sn 7 composite powders was performed at a temperature slightly higher than the glass-transition temperature under a pressure of ∼1.2 GPa; using this method, the bulk metallic glass composite discs were prepared successfully. However, partial crystallization of the amorphous matrix during the hot-pressing process was noticed. The fracture strength of consolidated composite compacts was increased with SiC additions. The pre-existing particle boundaries may serve as the crack initiation sites which resulted in the brittle failure of the Ti 50 Cu 28 Ni 15 Sn 7 BMG composites.

The surface roughness, microhardness, crystal structure and corrosion performance of nickels electroplated at atmospheric pressure and in supercritical CO 2 fluid, respectively, are compared. The experimental results showed that nickel electroplated in the latter case exhibited a lower surface roughness and a higher hardness. In HCl solution, the nickel deposited in supercritical CO 2 fluid had a lower anodic current density and a higher polarization resistance. The advantage of emulsified supercritical CO 2 fluid for electroplating was demonstrated.

Nanocrystalline manganese oxide powders were synthesized by an inert gas condensation technique. The manganese oxide powders, prepared from vaporized metallic manganese in a helium pressure of 10 mbar, then oxidized under the oxygen pressures of 50 and 100 mbar, exhibited a mixture of β-Mn, MnO and Mn3O4 phases. X-ray diffractometry (XRD) analysis identified the predominant oxide formation of the as-prepared powder to be the phase of MnO. In situ synchrotron XRD and differential scanning calorimetry (DSC) data showed that synthesized manganese powder converts from β-Mn to MnO in the temperature range of 150–250 °C and subsequently converts to Mn3O4 above 250 °C. Transmission electron microscopy examinations confirmed that oxidation starts from the surface of the condensed β-Mn particles. Detailed valance variations of manganese of the resulting powders were investigated by synchrotron X-ray absorption spectroscopy techniques.

The corrosion behavior of mechanically alloyed Cu60Zr30Ti10 bulk metallic glass (BMG) in four different corrosive media was studied by the potentiodynamic method. The Cu60Zr30Ti10 BMG shows low corrosion current density and uniform corrosion in 1N H2SO4, NaOH and HNO3 solutions. The Cu60Zr30Ti10 BMG specimen (consolidated at 746K under 1.2GPa) specimen exhibits most corrosion resistance in 1N H2SO4. The formation of the oxide films and the nucleation and growth of pitting will be discussed in light of microstructural investigations.

The oxidation behavior of the (Cu78Y22)98Al2 bulk metallic glass containing ∼55% Cu5Y particles (CYA-composite) was studied over the temperature range of 400–600 °C in dry air. The results generally showed that the oxidation kinetics of the composite obeyed a two-stage parabolic-rate law, with its steady-state parabolic-rate constants (kp values) increased with temperature. In addition, the oxidation rates of the composite were significantly lower than those of the polycrystalline Cu–20%Y alloy. The scales formed on the composite consisted mostly of hexagonal-Y2O3 (h-Y2O3) and minor CuO, while significant amounts of Cu2O and CuO, with minor amounts of Y2O3 were detected for the Cu–20%Y alloy. It was found that the absence of Cu2O is responsible for the slower oxidation rates of CYA-composite.

In the present study, amorphous Ni60Nb20Zr20 and Ti50Cu28Ni15Sn7 alloy powders were synthesized separately using a mechanical alloying (MA) technique. The dual-amorphous-phased (Ti50Cu28Ni15Sn7)100−x(Ni60Nb20Zr20)x (x = 0, 10, 20, and 30 vol%) powders were prepared by mixing the corresponding amorphous powders. The dual-amorphous-phased powders were then consolidated into bulk amorphous/amorphous composite (BA/AC) alloy discs. The amorphization status of as-prepared powders and bulk BA/AC composite discs was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The microstructure of the BA/AC discs showed that the Ni60Nb20Zr20 phase is distributed homogeneously within the Ti50Cu28Ni15Sn7 matrix. The (Ti50Cu28Ni15Sn7)70(Ni60Nb20Zr20)30 BA/AC disc exhibited a relative density of 96.6% and its Vickers microhardness was 726 kg/mm2.

ZnO thin-film transistors (TFTs) have attracted considerable R&D interest due to their high transparency and low photosensitivity compared with typical a-Si:H TFTs. The electrical characteristics of ZnO thin films may be controlled by doping with ternary element, for instance Al, Ga, In, Mg, Zr, etc. In this study, Zn 1 − x Mg x O ( x = 0 to 0.36) thin films were deposited on glass substrates by spin coating. The as-deposited films were baked at 300 °C for 10 min and then annealed at 500 °C for 1 h in air. The results show that, addition of Mg-species in ZnO films markedly enhanced the uniformity of film thickness and improved optical properties. The Zn 0.8 Mg 0.2 O film exhibited the best transparency of 92%, an increase of ∼ 15% over a pure ZnO film, and the rms roughness value decreased to 1.63. The Zn 1 − x Mg x O TFTs were demonstrated to have n-type enhancement behavior. The optimum device with Zn 0.8 Mg 0.2 O channel layer had a field-effect mobility of 0.1 cm 2 /V s, a threshold voltage of 6.0 V, and an on/off ratio more than 10 7 .

In the present study, pure elemental powders of Fe and S were mixed to give the desired compositions of Fe50S50. A SPEX 8000D high-energy ball mill was used to synthesize iron sulfide powders under an Ar-filled atmosphere. The prepared powders were examined by conventional X-ray diffractometry and synchrotron X-ray absorption spectroscopy. The experimental results revealed that mechanochemical reactions occurred during the ball milling process for all the compositions. The Fe50S50 phase was obtained after ball milling for 20 h. Extended X-ray absorption fine structure (EXAFS) results revealed that the nearest neighbor bond lengths of the radial distribution function (RDF) for iron decreased when iron sulfides formed. X-ray absorption near edge structure (XANES) of S K-edges distinguished better the structural evolution of these iron sulfides.

In the present study, Ti50Cu28Ni15Sn7 metallic glass and its composite powders reinforced with 4~12 vol% of SiC additions were successfully prepared by mechanical alloying. The as-milled Ti50Cu28Ni15Sn7 and composite powders were then consolidated by vacuum hot pressing into disc compacts with a 10 mm diameter and thickness of 2 mm. The structure of the as-milled powders and consolidated compacts was characterized by X-ray diffraction. While the thermal stability was examined by differential scanning calorimeter. In addition, the mechanical property of the consolidated bulk metallic glass and its composite was evaluated by Vickers microhardness tests. In the ball-milled composites, initial SiC particles were homogeneously dispersed in the Ti-based alloy glassy matrix. The presence of SiC particles did not dramatically change the thermal stability of Ti50Cu28Ni15Sn7 glassy powders. BMG composite with submicron SiC particles homogeneously embedded in a highly dense nanocrystalline/amorphous matrix was successfully prepared. A significant hardness increase with SiC additions was noticed for consolidated composite compacts.

Amorphous Ti50Cu28Ni15Sn7 alloy powders were synthesized by a mechanical alloying (MA) technique. Differential scanning calorimetry (DSC) results showed that, after 7 hours of exposure to the milling process, amorphous Ti50Cu28Ni15Sn7 alloy powders exhibit a wide supercooled liquid region of 61 K. Consolidation of amorphous powders were performed at a temperature slightly higher than the glass transition temperature under a pressure of ∼1.2 GPa, and bulk metallic glass (BMG) discs can be prepared successfully. However, we noticed partial crystallization during the hot pressing process and were not able to achieve full densification of BMG. The Vickers microhardness of Ti50Cu28Ni15Sn7 BMG was 634 kg/mm2, and the trace of the indentation revealed that pre-existing particle boundaries or interfaces between nanocrystals and amorphous matrix may serve as the crack initiation sites. Thus, typical brittle failure of Ti50Cu28Ni15Sn7 BMG was observed and resulted in relatively low fracture stress compared to that estimated by the microhardness.

Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced (OR) powders were compared with one from water-atomized (WA) powder. The green specimens were sintered at temperatures from 800 to 1000 °C in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR − 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.

The preparation of Mg 49 Y 15 Cu 36 metallic glass powders was accomplished by mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these Mg 49 Y 15 Cu 36 amorphous powders was investigated by differential scanning calorimeter (DSC). The T g , T x and Δ T x are 450, 492, and 42 K, respectively. The as-milled Mg 49 Y 15 Cu 36 powders were then consolidated by vacuum hot pressing into disc compacts with a diameter and thickness of 10 and 1 mm, respectively. After vacuum hot pressing, bulk Mg 49 Y 15 Cu 36 metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix was obtained. The applied pressure during consolidation can enhance the thermal stability and prolong the existence of amorphous phase inside Mg 49 Y 15 Cu 36 powders.

This study examined the amorphization behavior and thermal stability of mechanically alloyed Ni 57 Zr 20 Ti 20 Sn 3 powders synthesized by high-energy ball milling. Complete amorphization is feasible after 5 h of milling. The thermal stability of the Ni 57 Zr 20 Ti 20 Sn 3 amorphous powders was investigated by differential thermal analysis. As the results demonstrated, the temperature interval of the supercooled liquid region defined by the difference between glass-transition temperature and crystallization temperature is 96 K for Ni 57 Zr 20 Ti 20 Sn 3 . The glass-transition and crystallization temperatures of mechanically alloyed samples are different from those reported in the literature for samples prepared by melt spinning techniques. The different thermal stability is believed to be due to the introduction of impurities into the ball-milled samples during mechanical alloying process. The glass transition behavior in the Ni 57 Zr 20 Ti 20 Sn 3 is found to be a kinetically modified thermodynamic phase transformation process.

The oxidation behavior of two Cu-base bulk metallic glasses (BMGs), having compositions Cu–30Zr–10Ti and Cu–20Zr–10Ti–10Hf (in at.%), was studied over the temperature range of 350–500 °C in dry air. In general, the oxidation kinetics of both BMGs followed the parabolic rate law, with the oxidation rates increasing with increasing temperature. The addition of Hf slightly reduced the oxidation rates at 350–400 °C, while the opposite results observed at higher temperatures. It was found that the oxidation rates of both BMGs were significantly higher than those of polycrystalline pure-Cu. The scales formed on both BMG alloys were strongly composition dependent, consisting of mostly CuO/Cu2O and minor amounts of cubic-ZrO2 and ZrTiO4 for the ternary BMG, and of CuO, cubic-ZrO2, and Zr5Ti7O24 for the quaternary BMG. The formation of ternary oxides (ZrTiO4 and Zr5Ti7O24) was inferred to be responsible for the fast oxidation rates of the BMGs.

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Pb1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Pb1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 760 K and 850 K, respectively. The supercooled liquid region is 90 K. The appearance of wide supercooled liquid region may be mainly due to the Pb additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Pb1 powders.

Mg 45 Y 15 Cu 40 (numbers indicate at.%) metallic glass powders were prepared by the mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these Mg 45 Y 15 Cu 40 amorphous powders was investigated using the differential scanning calorimeter (DSC). T g , T x , and Δ T x are 456, 491, and 35 K, respectively. The as-milled Mg 45 Y 15 Cu 40 powders were then consolidated by vacuum hot pressing into disk compacts with a diameter and thickness of 10 and 1 mm, respectively. This yielded bulk Mg 45 Y 15 Cu 40 metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix. The pressure applied during consolidation can enhance thermal stability and prolong the existence of amorphous phase within Mg 45 Y 15 Cu 40 powders.

In the present study, mechanical alloying technique was used to prepare (Mg 2 Ni) 100− x Ti x ( x = 0, 2.5, 5, 7.5, and 10 wt.%) powders starting from elemental powder mixture under an Ar atmosphere. The experimental results showed that the absorbed hydrogen content and reversible hydrogen content was 3.14 and 2.40 wt.% for 15 h milled Mg 2 Ni powders, respectively. The maximum hydrogen absorption content was increased to over 3.8 wt.% with Ti additions. The reversible hydrogen content also increased significantly (18–25%) with Ti additions. Meanwhile, 15 h milled Mg 2 Ni–Ti powders can absorb more than 3 wt.% of hydrogen within 1000 s. Not only the hydrogen absorption ability but the hydrogen absorption rate were improved by the additions of titanium and MA treatment in Mg 2 Ni alloy.

The preparation of Ti50Cu28Ni15Sn7 (numbers indicate at.%) metallic glass composite powders was accomplished by the mechanical alloying of a pure Ti, Cu, Ni, Sn and WC powder mixture after 5 h milling. In the ball-milled composites, the initial WC particles were homogeneously dispersed in the Ti-based alloy glassy matrix. The metallic glass composite powders were found to exhibit a large supercooled liquid region before crystallization. The bulk metallic glass composite with submicron WC particles homogeneously embedded in a highly dense nanocrystalline/amorphous matrix was successfully prepared by vacuum hot pressing the as-milled WC/ Ti50Cu28Ni15Sn7 metallic glass composite powders at 723 K under a pressure of ∼1.2 GPa. A significant hardness increase with the WC additions was observed for the consolidated composite compacts.

The preparation of Ti50Cu28Ni15Sn7 metallic glass composite powders was accomplished by the mechanical alloying of a pure Ti, Cu, Ni, Sn and carbon nanotube (CNT) powder mixture after 8 h milling. In the ball-milled composites, the initial CNT particles were dissolved in the Ti-based alloy glassy matrix. The thermal stability of the amorphous matrix is affected by the presence of the CNT particles. Changes in Tg and Tx suggest deviations in the chemical composition of the glassy matrix due to a partial dissolution of the CNT species in the amorphous phase. The bulk metallic glass composite was successfully prepared by vacuum hot pressing the as-milled CNT/ Ti50Cu28Ni15Sn7 metallic glass composite powders. A significant hardness increase with the CNT additions was observed for the consolidated composite compacts.

In the present study, amorphous Mg 49 Y 15 Cu 36 and Ti 50 Cu 28 Ni 15 Sn 7 alloy powders were synthesized separately by using a mechanical alloying technique. The dual-phase (Mg 49 Y 15 Cu 36 ) 100-x (Ti 50 Cu 28 Ni 15 Sn 7 ), (x = 0, 10, 20, 30, 40, and 50vol%) powders were prepared by mixing the corresponding amorphous powders. The amorphous dual-phase powders were then consolidated into bulk metallic glass (BMG) discs. The amorphization status of as-prepared powders and BMG discs was confirmed by X-ray diffraction and by using a differential scanning calorimeter. The microstructure of the BMG discs showed that the Ti 50 Cu 28 Ni 15 Sn 7 phase is distributed homogeneously within the Mg 49 Y 15 Cu 36 matrix. The (Mg 49 Y 15 Cu 36 ) 50 (Ti 50 Cu 28 Ni 15 Sn 7 ) 50 BMG disc exhibited a relative density of 97.2% and its Vickers microhardness was 526±20 kg/mm 2 .

The hydrogen storage alloy (Mg2Ni)100� xTix (x ¼ 0, 2.5, 5.0, 7.5 and 10.0 at%) powders were synthesized from elemental powder mixture by mechanical alloying (MA) under an Ar atmosphere. The as-milled powders were examined as a function of titanium addition by X-ray diffraction and synchrotron X-ray absorption near-edge structure (XANES) techniques at various milling time. The hydrogen absorption kinetics of the 15 h as-milled powders were evaluated. The maximum hydrogen absorption content of 15 h as-milled Mg2Ni powders can be improved from 3.14 mass% to 3.88 mass% when 5.0 at% of titanium was added. The hydrogenation rate of the Mg2Ni powder was also obviously enhanced by introducing the titanium into Mg2Ni lattices. More than 20% improvement of hydrogen absorption for Mg2Ni intermetallic powders was achieved by adding titanium. [doi:10.2320/matertrans.MER2007169]

Mg55Y15Cu30 metallic glass powders were prepared by the mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these Mg55Y15Cu30 amorphous powders was investigated using the differential scanning calorimeter (DSC). Tg ,Tx , and Δ Tx are 442 K, 478 K, and 36 K, respectively. The as-milled Mg55Y15Cu30 powders were then consolidated by vacuum hot pressing into disk compacts with a diameter and thickness of 10 mm and 1 mm, respectively. This yielded bulk Mg55Y15Cu30 metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix. The pressure applied during consolidation can enhance thermal stability and prolong the existence of amorphous phase within Mg55Y15Cu30 powders.

In this study, γ-Al2O3 particles were dispersed in p-type Bi0.4Sb1.6Te3 through mechanical alloying to form γ-Al2O3/Bi0.4Sb1.6Te3 composite powders. The composite powders were consolidated using vacuum hot pressing to produce nano- and microstructured composites. Thermoelectric (TE) measurements indicated that adding an optimal amount of γ-Al2O3 nanoparticles improves the TE performance of the fabricated composites. High TE performances with figure of merit (ZT) values as high as 1.22 and 1.21 were achieved at 373 and 398 K for samples containing 1 and 3 wt % γ-Al2O3 nanoparticles, respectively. These ZT values are higher than those of monolithic Bi0.4Sb1.6Te3 samples. The ZT values of the fabricated samples at 298–423 K are 1.0–1.22, these ZT characteristics make γ-Al2O3/Bi0.4Sb1.6Te3 composites suitable for power generation applications because no other material with a similarly high ZT value has been reported at this temperature range. The achieved high ZT value may be attributable to the unique nano- and microstructures in which γ-Al2O3 nanoparticles are dispersed among the grain boundary or in the matrix grain, as revealed by high-resolution transmission electron microscopy. The dispersed γ-Al2O3 nanoparticles thus increase phonon scattering sites and reduce thermal conductivity. The results indicated that the nano- and microstructured γ-Al2O3/Bi0.4Sb1.6Te3 alloy can serve as a high-performance material for application in TE devices.

We have studied the amorphization behavior of Mg 85− x Y 15 Cu x ( x =20–40) alloy powders synthesized by mechanical alloying technique. The as-milled powders were mainly amorphous after 10 h of milling. The thermal stability of these Mg 85− x Y 15 Cu x glassy powders was investigated by differential scanning calorimeter (DSC). The ranges of Tg, T x and Δ T x are around 430–459, 467–497, and 30–46 K, respectively. The Mg 49 Y 15 Cu 36 glassy powders exhibit the largest supercooled region of 46 K. The amorphization behavior of Mg 61 Y 15 Cu 24 was examined in details. Amorphous phases gradually became dominant after 7.5 h of milling and fully amorphous powders formed at the end of milling. The thermal stability of Mg 61 Y 15 Cu 24 glassy powders was similar to that of melt-spun Mg 60 Y 15 Cu 25 amorphous alloys. Mg 61 Y 15 Cu 24 bulk metallic glass with homogeneously embedded nanocrystalline precipitates was successfully prepared by vacuum hot pressing. It was found that the applied pressure during consolidation could enhance the thermal stability and prolong the existence of amorphous phase inside Mg 61 Y 15 Cu 24 powders.

In the present study, amorphous Ti 50 Cu 28 Ni 15 Sn 7 and its composite powders reinforced with 4, 8, and 12 vol.% of W additions were prepared by mechanical alloying. After 5 h of milling, amorphous powders with homogeneously dispersed W nanoparticles were synthesized. The as-milled Ti 50 Cu 28 Ni 15 Sn 7 and composite powders were then consolidated by vacuum hot pressing into disc compacts with a diameter and thickness of 4 and 10 mm, respectively. The structure of the as-milled powders and consolidated compacts was characterized by X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy. While the thermal stability was examined by differential scanning calorimeter (DSC). In addition, the mechanical property of the consolidated BMGs was evaluated by Vickers microhardness tests. The experimental results showed that W nanoparticles ranged from 20 to 200 nm were embedded within the amorphous matrix. The presence of W nanoparticles did not dramatically change the glass formation ability of amorphous Ti 50 Cu 28 Ni 15 Sn 7 powders. While the thermal stability of amorphous powders differed from those of its composites. A significant hardness increase with W additions was noticed for consolidated composite compacts.