The nanocrystalline and amorphous Mg2Ni-type alloys with a chemical composition of (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) were fabricated by melt spinning technology. The effects of spinning rate on the struct...The nanocrystalline and amorphous Mg2Ni-type alloys with a chemical composition of (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) were fabricated by melt spinning technology. The effects of spinning rate on the structure and electrochemical hydrogen storage performance of the alloys were investigated. The as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a nanocrystalline and amorphous structure, suggesting that the addition of Nd facilitates the glass forming of the Mg2Ni-type alloys. Increasing the spinning rate from 0 to 40 m/s gives rise to the discharge capacity growing from 42.5 to 100.6 mA·h/g for the x=0 alloy and from 86.4 to 452.8 mA·h/g for the x=10 alloy. And the cycle stability (S20) rises from 40.2%to 41.1%for the x=0 alloy and from 53.2%to 89.7%for the x=10 alloy, respectively.展开更多
In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology ...In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology was used to fabricate the La_(0.75-x)M_xMg_0.25Ni_3.2Co_0.2Al_0.1 (M = Zr, Pr; x = 0, 0.1) electrode alloys. The influences of the melt spinning and substituting La with M (M = Zr, Pr) on the structures and the electrochemical hydrogen storage characteristics of the alloys were investigated. The analysis of XRD, SEM, and TEM reveals that the as-cast and spun alloys have a multiphase structure composed of two main phases (La, Mg)_2Ni_7 and LaNi_5 as well as a residual phase LaNi_2 . The as-spun (M = Pr) alloy displays an entire nanocrystalline structure, while an amorphous-like structure is detected in the as-spun (M = Zr) alloy, implying that the substitution of Zr for La facilitates the amorphous formation. The electrochemical measurements exhibit that the substitution of Pr for La clearly increases the discharge capacity of the alloys; however, the Zr substitution brings on an adverse impact. Meanwhile, the M (M = Zr, Pr) substitution significantly enhances its cycle stability. The melt spinning exerts an evident effect on the electrochemical performances of the alloys, whose discharge capacity and high rate discharge ability (HRD) first mount up and then fall with the growing spinning rate, whereas their cycle stabilities monotonously augment as the spinning rate increases.展开更多
The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermod...The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermodynamics of TiFe-type Ti−Fe−Mn-based alloy were investigated.The as-spun alloys hold the TiFe single phase,which transforms to TiFeH_(0.06),TiFeH,and TiFeH_(2) hydrides after hydrogenation.La substitution promotes the formation of micro-defects(such as dislocations and grain boundaries)in the alloys,thus facilitating hydrogen diffusion.In addition,the hydrogen storage kinetics properties are improved after introducing La element.With the rise of La content,the hydrogen storage capacity decreases firstly and then increases,but the absolute value of hydriding enthalpy change(|ΔH|)increases firstly and then reduces.When x=0.01,the maximum value of|ΔH|is obtained to be(25.23±0.50)kJ/mol for hydriding,and the alloy has the maximum hydrogen absorption capacity of(1.80±0.04)wt.%under the conditions of 323 K and 3 MPa.展开更多
The microstructure and properties of nanostructured Cu-13.2Al-5.1Ni shape memory alloy (SMA) were compared with those of initial coarse structure. The nanostructured Cu-Al-Ni ribbons were produced via rapid solidifi...The microstructure and properties of nanostructured Cu-13.2Al-5.1Ni shape memory alloy (SMA) were compared with those of initial coarse structure. The nanostructured Cu-Al-Ni ribbons were produced via rapid solidification using melt spinning technique. The structure and properties of both nanostructured and coarse-grain specimens were then characterized using XRD, SEM, AFM and DSC techniques. According to the obtained results, the nanostructured ribbons show one way shape memory effect. Besides, the formation of nanoparticles of γ2 (Cu9Al4) and the nanograins results in a significant decrease in the martensite-austenite transformation temperature. The produced nanostructure not only leads to a considerable increase in the recovered deformation but also results in the structure stability when it is subjected to deformation-recovery cycles.展开更多
Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composi...Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composition not only enhances magnetic properties, but also changes texture direction of the ribbon. Low temperature heat treatment can increase the magnetic properties to some extent, and high temperature annealing decreases the magnetic properties. Both low and high temperature heat treatment have effects on grain orientation, but the difference still exists between the two surfaces of the ribbon. So it is infeasibility to prepare anisotropic Nd_2Fe_ 14B/α-Fe nanocomposite magnets by direct melt spinning.展开更多
Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous h...Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.展开更多
A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw ...A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw resonance. The results show that for shear thin fluids, the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning. When the power index approaches zero, the critical draw ratio points at unity, indicating no melt spinning can be processed stably for such fluids. For shear thick fluids, the critical draw ratio increases in a more rapid way with increasing the power index.展开更多
The morphology and structure of melt spinning Ni-33.6at% Al doped with B and RE were investigated.The results show that the alloy consists of L10 martensitic grains and L12 Ni3Al at the grain boundaries when it contai...The morphology and structure of melt spinning Ni-33.6at% Al doped with B and RE were investigated.The results show that the alloy consists of L10 martensitic grains and L12 Ni3Al at the grain boundaries when it contains no B and RE.The addition of 0.11-0.31wt% B can suppress the martensitic transformation and Ni3Al separation at the boundaries,and a supersaturated B2 single phase NiAl is obtained.The addition of 0.05wt% RE can eliminate Ni3Al precipitated at the boundaries and get complete martensite,but 0.2-0.8wt% RE addition can suppress the martensitic transformation, and supersaturated B2 single phase NiAl is obtained.The formation mechanism of supersaturated B2 single phase NiAl has been analyzed.展开更多
The aim of this study is to investigate the surface quality of the melt spinning wheel, which was changed from smooth type to textured structure, to atomize liquid metal to form powders. The effects of melt spinning p...The aim of this study is to investigate the surface quality of the melt spinning wheel, which was changed from smooth type to textured structure, to atomize liquid metal to form powders. The effects of melt spinning process parameters like wheel speed, gas ejection pressure, molten metal temperature, nozzle–wheel gap and wheel surface quality on the morphological and microstructural features of 6060 aluminum alloy powders and ribbons were investigated. It was observed that ribbon type material was obtained with the smooth wheel and the powder was produced with textured type. The sizes of produced ribbons with smooth surface wheel varied in the range of 30-170 μm in thickness, 4-8 mm in width, and 0.5-1 m in length. The average powder size of the powders manufactured using the textured wheel was in the range of 161-274 μm, depending on the process parameters.Increasing the wheel speed, melt temperature and decreasing gas ejection pressure, nozzle-wheel gap resulted in the decrease of both ribbon thickness and powder size. The microstructures of the powders and ribbons were the equiaxed cellular type, and the average grain sizes diminished with decreasing the ribbon thickness and powder size. The maximum cooling rates were 2.00×10^5 and 1.26×10^4 K/s for the ribbon with thickness of 30 μm and for the powder with size of 87 μm, respectively.展开更多
The influence of the refilled gas pressure on the glass forming behaviour of one of the best ternary glass forming alloys Zr50Cu40Al10 was studied for the melt spinning process. The amorphicity of as-quenched ribbons ...The influence of the refilled gas pressure on the glass forming behaviour of one of the best ternary glass forming alloys Zr50Cu40Al10 was studied for the melt spinning process. The amorphicity of as-quenched ribbons was characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The refilled chamber atmospheric pressure is crucial to the cooling rate of melt spinning. At high vacuum, at pressure less than 0.0001 atm, fully crystalline fragments are obtained. Monolithic amorphous ribbons were only obtained at a gas pressure of 0.1 atm or higher. The extended contact length between thecribbons and the copper wheel contributes to the high cooling rate of melt spinning. Higher chamber gas pressure leads to more turbulence of liquid metal beneath the nozzle; therefore, lower pressure is preferable at practical melt spinning processes once glass forming conditions are fulfilled.展开更多
La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated t...La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.展开更多
Melt spinning (MS) and ball milling (BM) were employed to fabricate YMg11Ni alloy, and their structures and hydrogen storage performances were examined. The results reveal that the as-spun and as-milled alloys bot...Melt spinning (MS) and ball milling (BM) were employed to fabricate YMg11Ni alloy, and their structures and hydrogen storage performances were examined. The results reveal that the as-spun and as-milled alloys both exhibit the nanocrystalline and amorphous structure. The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun alloy. More than that, the as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one, which are 549.8 and 560.9 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property to the as-spun one. On the basis of the time needed by desorbing hydrogen of 3 wt% H2, for the as- milled alloy, it needs 1106, 456, 343, and 180 s corresponding to hydrogen desorption temperatures of 593, 613, 633, and 653 K. However, for the as-spun alloy, the time needed is greater than 2928, 842, 356, and 197 s corresponding to the same temperatures. Hydrogen desorption activation energies of as-milled and as-spun alloys are 98.01 and 105.49 kJ/mol, respectively, which is responsible for that the as-milled alloy possesses a much faster dehydriding rate. By means of the measurement of pressure-composition-temperature (P-C-T) curves, the dehydrogenation enthalpy change of the alloys prepared by MS (△Hoe(MS)) and BM (△Hdc(BM)) is 81.84 and 79.46 kJ/mol, respectively, viz. △Hde(MS) 〉 △Hoc(BM).展开更多
The numerical simulation model of single roller melt spinning for rapid quenching process of NdFeB alloy was built,and the vacuum chamber,cooling roller and sample were taken into account as a system.The existing matu...The numerical simulation model of single roller melt spinning for rapid quenching process of NdFeB alloy was built,and the vacuum chamber,cooling roller and sample were taken into account as a system.The existing mature technology was in order to verify the correctness of simulation.The rapid quenching ribbons with different roll speeds were used as the simulation objects.The results of the numerical simulation and experiments show that the validity of the model has been testified and the reasons of the formation of complete quenching ribbons and by-product have been explained.The experimental thickness of the ribbons is proportional to the theoretical thickness.In the same spray condition,with the roll speed increasing,the thickness decreases linearly.At the speed range of25-30 m·s^(-1),the simulated calculation date is close to the experimental date,which can be considered as an ideal technological parameter.展开更多
Nd_(11)Fe_(71)Co_8V_(1.5)Cr_1B_(7.5) magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that f...Nd_(11)Fe_(71)Co_8V_(1.5)Cr_1B_(7.5) magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that fine nanocomposite microstructure consisting of Nd_2Fe_(14)B and α-Fe phases can be developed at an optimum wheel speed of about 21 m·s^(-1). After optimal annealing (640 ℃×4 min), magnetic properties of B_r=0.64 T, (()_jH_c)=903.5 kA·m^(-1) and (BH)_(max)=71 (kJ·m^(-3)) were obtained for the bonded magnets. The addition of Cr element significantly reduces grain size, increasing the intrinsic coercivity and maximum magnetic energy product.展开更多
The nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)loo-xNdx (x = 0-20) were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy ins...The nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)loo-xNdx (x = 0-20) were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy inspections reveal that, by varying the spinning rate and the Nd content, different microstructures could be obtained by melt spinning. Particularly, the as-spun Nd-free alloy holds an entire nanocrystalline structure but the as-spun Nd-added alloy has a nanocrystalline and amorphous structure, which implies that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Also, the degree of the amorphization in the as-spun Nd-added alloys clearly increases with increasing the spinning rate and the Nd content. The H-storage capacity and the hydrogenation kinetics of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and the phase composition of the alloys. Specially, enhancing the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s makes the hydrogen absorption saturation ratio (R5a) (a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increase from 35.2% to 90.3% and the hydrogen desorption ratio (R10d) (a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rise from 12.7% to 44.9% for the (x = 5) alloy. And the growing of the Nd content from 0 to 20 gives rise to the R5a and R10d values rising from 85.7% to 94.5% and from 36.7% to 54.8% for the as-spun (30 m/s) alloys, respectively.展开更多
High-performance α-Fe/Pr2FelnB-type nanocomposite magnets based on the compositions of PrsFes6B6 microalloyed with Co, Nb and C were fabricated by direct melt spinning. The coercivity was greatly improved from 5.5 kO...High-performance α-Fe/Pr2FelnB-type nanocomposite magnets based on the compositions of PrsFes6B6 microalloyed with Co, Nb and C were fabricated by direct melt spinning. The coercivity was greatly improved from 5.5 kOe for the Pr8Fe86B6 ribbons to 7.4 kOe for the Pr8Fe85NbB5C ribbons. The balanced high coercivity and remanence were obtained in Pr8Fe75Co10NbB5C ribbons due to the Co substitution for Fe, which led to the significant improvement of magnetic properties in these ribbons. A remanence ratio of 0.82, a coercive field of 6.6 kOe and a maximum energy product of 26.2 MGOe in melt-sptm Pr8Fe75Co10NbB5C ribbons were ob- tained at room temperature.展开更多
The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologi...The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_(11)Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_(Ms)(des) = 82.51 kJ/mol and ΔH_(BM)(des) = 81.68 kJ/mol, respectively, viz.ΔH_(MS)(des) 〉 ΔH_(BM)(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.展开更多
The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies sh...The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.展开更多
The effects of the Cr3C2 content and wheel speed on the amorphization behavior of the melt-spun SmCo7-x(Cr3C2)x (x=0.10-0.25) alloys were studied systematically by X-ray diffraction analysis (XRD), differential ...The effects of the Cr3C2 content and wheel speed on the amorphization behavior of the melt-spun SmCo7-x(Cr3C2)x (x=0.10-0.25) alloys were studied systematically by X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and magnetic measurements. The ribbon melt-spun at lower wheel speed (20 m/s) has composite structure composed of mostly SmCo7 and a small amount of Sm2Co17R. The grain size of SmCo7 phase decreases with the increase of Cr3C2 content. With the increase of wheel speed, the XRD peaks become lower and accompanied with a broad increase in backgrounds, indicating a considerable decrease in the grain size of the SmCo7 phase. When the wheel speed increases to 40 m/s, SmCo7-x(Cr3C2)x alloys can be obtained in the amorphous state for 0.15≤x≤0.25 with intrinsic coercive Hci of 0.004-0.007 T. The DSC analysis reveals that SmCo7 phase firstly precipitates from the amorphous matrix at 650 °C, followed by the crystallization of Sm2Co17 phase at 770 °C.展开更多
Temperature regulating fibers(TRF_(s)) with high enthalpy and high form stability are the key factors for thermal management. However, the enthalpies of most TRFsare not high, and the preparation methods are still at ...Temperature regulating fibers(TRF_(s)) with high enthalpy and high form stability are the key factors for thermal management. However, the enthalpies of most TRFsare not high, and the preparation methods are still at the laboratory scale. It remains a great challenge to use industrial spinning equipment to achieve continuous processing of TRF_(s) with excellent thermal and mechanical properties. Here, polyamide 6(PA6) based TRF_(s) with a sheath-core structure were prepared by bicomponent melt-spinning. The sheath-core TRF(TRF_(sc)) are composed of PA6 as sheath and functional PA6 as core, which are filled with the shape stable phase change materials(ssPCM),dendritic silica@polyethylene glycol(SiO_(2)@PEG). With the aid of the sheath structure, the filling content of SiO_(2)@PEG can reach 30 %, so that the enthalpy of the TRF_(s) can be as high as 21.3 J/g. The ultra-high enthalpy guarantees the temperature regulation ability during the alternating process of cooling and heating. In hot environment, the temperature regulation time is 6.59 min, and the temperature difference is 12.93℃. In addition, the mechanical strength of the prepared TRF_(sc) reaches 2.26 cN/dtex, which can fully meet its application in the field of thermal management textiles and devices to manage the temperature regulation of the human body or precision equipment, etc.展开更多
基金Projects (51161015,51371094) supported by the National Natural Science Foundation of ChinaProject (2011ZD10) supported by the Natural Science Foundation of Inner Mongolia,China
文摘The nanocrystalline and amorphous Mg2Ni-type alloys with a chemical composition of (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) were fabricated by melt spinning technology. The effects of spinning rate on the structure and electrochemical hydrogen storage performance of the alloys were investigated. The as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a nanocrystalline and amorphous structure, suggesting that the addition of Nd facilitates the glass forming of the Mg2Ni-type alloys. Increasing the spinning rate from 0 to 40 m/s gives rise to the discharge capacity growing from 42.5 to 100.6 mA·h/g for the x=0 alloy and from 86.4 to 452.8 mA·h/g for the x=10 alloy. And the cycle stability (S20) rises from 40.2%to 41.1%for the x=0 alloy and from 53.2%to 89.7%for the x=10 alloy, respectively.
基金supported by the National Natural Science Foundation of China(Nos.51161015 and 50961009)the National High-Technology Research and Development Program of China(No.2011AA03A408)the Natural Science Foundation of Inner Mongolia,China(Nos.2011ZD10 and 2010ZD05)
文摘In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology was used to fabricate the La_(0.75-x)M_xMg_0.25Ni_3.2Co_0.2Al_0.1 (M = Zr, Pr; x = 0, 0.1) electrode alloys. The influences of the melt spinning and substituting La with M (M = Zr, Pr) on the structures and the electrochemical hydrogen storage characteristics of the alloys were investigated. The analysis of XRD, SEM, and TEM reveals that the as-cast and spun alloys have a multiphase structure composed of two main phases (La, Mg)_2Ni_7 and LaNi_5 as well as a residual phase LaNi_2 . The as-spun (M = Pr) alloy displays an entire nanocrystalline structure, while an amorphous-like structure is detected in the as-spun (M = Zr) alloy, implying that the substitution of Zr for La facilitates the amorphous formation. The electrochemical measurements exhibit that the substitution of Pr for La clearly increases the discharge capacity of the alloys; however, the Zr substitution brings on an adverse impact. Meanwhile, the M (M = Zr, Pr) substitution significantly enhances its cycle stability. The melt spinning exerts an evident effect on the electrochemical performances of the alloys, whose discharge capacity and high rate discharge ability (HRD) first mount up and then fall with the growing spinning rate, whereas their cycle stabilities monotonously augment as the spinning rate increases.
基金financial supports from the Inner Mongolia Natural Science Foundation,China (No.2019BS05005)the Inner Mongolia University of Science and Technology Innovation Fund,China (No.2019QDL-B11)the National Natural Science Foundation of China (Nos.51901105, 51871125, 51761032).
文摘The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermodynamics of TiFe-type Ti−Fe−Mn-based alloy were investigated.The as-spun alloys hold the TiFe single phase,which transforms to TiFeH_(0.06),TiFeH,and TiFeH_(2) hydrides after hydrogenation.La substitution promotes the formation of micro-defects(such as dislocations and grain boundaries)in the alloys,thus facilitating hydrogen diffusion.In addition,the hydrogen storage kinetics properties are improved after introducing La element.With the rise of La content,the hydrogen storage capacity decreases firstly and then increases,but the absolute value of hydriding enthalpy change(|ΔH|)increases firstly and then reduces.When x=0.01,the maximum value of|ΔH|is obtained to be(25.23±0.50)kJ/mol for hydriding,and the alloy has the maximum hydrogen absorption capacity of(1.80±0.04)wt.%under the conditions of 323 K and 3 MPa.
文摘The microstructure and properties of nanostructured Cu-13.2Al-5.1Ni shape memory alloy (SMA) were compared with those of initial coarse structure. The nanostructured Cu-Al-Ni ribbons were produced via rapid solidification using melt spinning technique. The structure and properties of both nanostructured and coarse-grain specimens were then characterized using XRD, SEM, AFM and DSC techniques. According to the obtained results, the nanostructured ribbons show one way shape memory effect. Besides, the formation of nanoparticles of γ2 (Cu9Al4) and the nanograins results in a significant decrease in the martensite-austenite transformation temperature. The produced nanostructure not only leads to a considerable increase in the recovered deformation but also results in the structure stability when it is subjected to deformation-recovery cycles.
文摘Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composition not only enhances magnetic properties, but also changes texture direction of the ribbon. Low temperature heat treatment can increase the magnetic properties to some extent, and high temperature annealing decreases the magnetic properties. Both low and high temperature heat treatment have effects on grain orientation, but the difference still exists between the two surfaces of the ribbon. So it is infeasibility to prepare anisotropic Nd_2Fe_ 14B/α-Fe nanocomposite magnets by direct melt spinning.
基金Projects(51161015,51371094)supported by the National Natural Science Foundation of China
文摘Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.
文摘A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw resonance. The results show that for shear thin fluids, the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning. When the power index approaches zero, the critical draw ratio points at unity, indicating no melt spinning can be processed stably for such fluids. For shear thick fluids, the critical draw ratio increases in a more rapid way with increasing the power index.
文摘The morphology and structure of melt spinning Ni-33.6at% Al doped with B and RE were investigated.The results show that the alloy consists of L10 martensitic grains and L12 Ni3Al at the grain boundaries when it contains no B and RE.The addition of 0.11-0.31wt% B can suppress the martensitic transformation and Ni3Al separation at the boundaries,and a supersaturated B2 single phase NiAl is obtained.The addition of 0.05wt% RE can eliminate Ni3Al precipitated at the boundaries and get complete martensite,but 0.2-0.8wt% RE addition can suppress the martensitic transformation, and supersaturated B2 single phase NiAl is obtained.The formation mechanism of supersaturated B2 single phase NiAl has been analyzed.
文摘The aim of this study is to investigate the surface quality of the melt spinning wheel, which was changed from smooth type to textured structure, to atomize liquid metal to form powders. The effects of melt spinning process parameters like wheel speed, gas ejection pressure, molten metal temperature, nozzle–wheel gap and wheel surface quality on the morphological and microstructural features of 6060 aluminum alloy powders and ribbons were investigated. It was observed that ribbon type material was obtained with the smooth wheel and the powder was produced with textured type. The sizes of produced ribbons with smooth surface wheel varied in the range of 30-170 μm in thickness, 4-8 mm in width, and 0.5-1 m in length. The average powder size of the powders manufactured using the textured wheel was in the range of 161-274 μm, depending on the process parameters.Increasing the wheel speed, melt temperature and decreasing gas ejection pressure, nozzle-wheel gap resulted in the decrease of both ribbon thickness and powder size. The microstructures of the powders and ribbons were the equiaxed cellular type, and the average grain sizes diminished with decreasing the ribbon thickness and powder size. The maximum cooling rates were 2.00×10^5 and 1.26×10^4 K/s for the ribbon with thickness of 30 μm and for the powder with size of 87 μm, respectively.
基金financially supported by the National Natural Science Foundation of China(No.51171119)the Natural Science Foundation of Liaoning Province(No.2013020084)+1 种基金Higher Education Youth Talent Scholar Fostering Project of Liaoning Province(No.LJQ2014015)Project of Shenyang Bureau of Science and Technological Development(No.1091177-1-00)
文摘The influence of the refilled gas pressure on the glass forming behaviour of one of the best ternary glass forming alloys Zr50Cu40Al10 was studied for the melt spinning process. The amorphicity of as-quenched ribbons was characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The refilled chamber atmospheric pressure is crucial to the cooling rate of melt spinning. At high vacuum, at pressure less than 0.0001 atm, fully crystalline fragments are obtained. Monolithic amorphous ribbons were only obtained at a gas pressure of 0.1 atm or higher. The extended contact length between thecribbons and the copper wheel contributes to the high cooling rate of melt spinning. Higher chamber gas pressure leads to more turbulence of liquid metal beneath the nozzle; therefore, lower pressure is preferable at practical melt spinning processes once glass forming conditions are fulfilled.
基金Project supported by National Natural Science Foundation of China(51161015,51371094,51471054)
文摘La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.
基金financially supported by the National Natural Science Foundations of China(Nos.51371094 and 51471054)the Natural Science Foundation of Inner Mongolia,China(No.2015MS0558)
文摘Melt spinning (MS) and ball milling (BM) were employed to fabricate YMg11Ni alloy, and their structures and hydrogen storage performances were examined. The results reveal that the as-spun and as-milled alloys both exhibit the nanocrystalline and amorphous structure. The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun alloy. More than that, the as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one, which are 549.8 and 560.9 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property to the as-spun one. On the basis of the time needed by desorbing hydrogen of 3 wt% H2, for the as- milled alloy, it needs 1106, 456, 343, and 180 s corresponding to hydrogen desorption temperatures of 593, 613, 633, and 653 K. However, for the as-spun alloy, the time needed is greater than 2928, 842, 356, and 197 s corresponding to the same temperatures. Hydrogen desorption activation energies of as-milled and as-spun alloys are 98.01 and 105.49 kJ/mol, respectively, which is responsible for that the as-milled alloy possesses a much faster dehydriding rate. By means of the measurement of pressure-composition-temperature (P-C-T) curves, the dehydrogenation enthalpy change of the alloys prepared by MS (△Hoe(MS)) and BM (△Hdc(BM)) is 81.84 and 79.46 kJ/mol, respectively, viz. △Hde(MS) 〉 △Hoc(BM).
基金financially supported by the National Natural Science Foundation of China(No.51571064)the National Basic Research Program of China(No.2014CB643701)。
文摘The numerical simulation model of single roller melt spinning for rapid quenching process of NdFeB alloy was built,and the vacuum chamber,cooling roller and sample were taken into account as a system.The existing mature technology was in order to verify the correctness of simulation.The rapid quenching ribbons with different roll speeds were used as the simulation objects.The results of the numerical simulation and experiments show that the validity of the model has been testified and the reasons of the formation of complete quenching ribbons and by-product have been explained.The experimental thickness of the ribbons is proportional to the theoretical thickness.In the same spray condition,with the roll speed increasing,the thickness decreases linearly.At the speed range of25-30 m·s^(-1),the simulated calculation date is close to the experimental date,which can be considered as an ideal technological parameter.
文摘Nd_(11)Fe_(71)Co_8V_(1.5)Cr_1B_(7.5) magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that fine nanocomposite microstructure consisting of Nd_2Fe_(14)B and α-Fe phases can be developed at an optimum wheel speed of about 21 m·s^(-1). After optimal annealing (640 ℃×4 min), magnetic properties of B_r=0.64 T, (()_jH_c)=903.5 kA·m^(-1) and (BH)_(max)=71 (kJ·m^(-3)) were obtained for the bonded magnets. The addition of Cr element significantly reduces grain size, increasing the intrinsic coercivity and maximum magnetic energy product.
基金the financial support from the National Natural Science Foundation of China,China (Nos.51161015 and 51371094)the Natural Science Foundation of Inner Mongolia,China(No.2011ZD10)
文摘The nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)loo-xNdx (x = 0-20) were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy inspections reveal that, by varying the spinning rate and the Nd content, different microstructures could be obtained by melt spinning. Particularly, the as-spun Nd-free alloy holds an entire nanocrystalline structure but the as-spun Nd-added alloy has a nanocrystalline and amorphous structure, which implies that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Also, the degree of the amorphization in the as-spun Nd-added alloys clearly increases with increasing the spinning rate and the Nd content. The H-storage capacity and the hydrogenation kinetics of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and the phase composition of the alloys. Specially, enhancing the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s makes the hydrogen absorption saturation ratio (R5a) (a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increase from 35.2% to 90.3% and the hydrogen desorption ratio (R10d) (a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rise from 12.7% to 44.9% for the (x = 5) alloy. And the growing of the Nd content from 0 to 20 gives rise to the R5a and R10d values rising from 85.7% to 94.5% and from 36.7% to 54.8% for the as-spun (30 m/s) alloys, respectively.
基金Project supported by the Fundamental Research Funds for Central Universitiesthe National Natural Science Foundation of China(51101007)the National Basic Research Program of China(973Program)(2010CB934602)
文摘High-performance α-Fe/Pr2FelnB-type nanocomposite magnets based on the compositions of PrsFes6B6 microalloyed with Co, Nb and C were fabricated by direct melt spinning. The coercivity was greatly improved from 5.5 kOe for the Pr8Fe86B6 ribbons to 7.4 kOe for the Pr8Fe85NbB5C ribbons. The balanced high coercivity and remanence were obtained in Pr8Fe75Co10NbB5C ribbons due to the Co substitution for Fe, which led to the significant improvement of magnetic properties in these ribbons. A remanence ratio of 0.82, a coercive field of 6.6 kOe and a maximum energy product of 26.2 MGOe in melt-sptm Pr8Fe75Co10NbB5C ribbons were ob- tained at room temperature.
基金Project supported by the National Natural Science Foundations of China(51761032,51371094 and 51471054)Natural Science Foundation of Inner Mongolia,China(2015MS0558)
文摘The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_(11)Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_(Ms)(des) = 82.51 kJ/mol and ΔH_(BM)(des) = 81.68 kJ/mol, respectively, viz.ΔH_(MS)(des) 〉 ΔH_(BM)(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.
文摘The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.
基金Project (51104188) supported by the National Natural Science Foundation for Young Scholars of China
文摘The effects of the Cr3C2 content and wheel speed on the amorphization behavior of the melt-spun SmCo7-x(Cr3C2)x (x=0.10-0.25) alloys were studied systematically by X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and magnetic measurements. The ribbon melt-spun at lower wheel speed (20 m/s) has composite structure composed of mostly SmCo7 and a small amount of Sm2Co17R. The grain size of SmCo7 phase decreases with the increase of Cr3C2 content. With the increase of wheel speed, the XRD peaks become lower and accompanied with a broad increase in backgrounds, indicating a considerable decrease in the grain size of the SmCo7 phase. When the wheel speed increases to 40 m/s, SmCo7-x(Cr3C2)x alloys can be obtained in the amorphous state for 0.15≤x≤0.25 with intrinsic coercive Hci of 0.004-0.007 T. The DSC analysis reveals that SmCo7 phase firstly precipitates from the amorphous matrix at 650 °C, followed by the crystallization of Sm2Co17 phase at 770 °C.
基金financially supported by the National Natural Science Foundation of China (52073047)the Science and Technology Commission of Shanghai Municipality (20JC1414900)+1 种基金the Program of Shanghai Technology Research Leader (20XD1433700)the INTERNATIONAL COOPERATION Fund of the Science and Technology Commission of Shanghai Municipality (20520740800)。
文摘Temperature regulating fibers(TRF_(s)) with high enthalpy and high form stability are the key factors for thermal management. However, the enthalpies of most TRFsare not high, and the preparation methods are still at the laboratory scale. It remains a great challenge to use industrial spinning equipment to achieve continuous processing of TRF_(s) with excellent thermal and mechanical properties. Here, polyamide 6(PA6) based TRF_(s) with a sheath-core structure were prepared by bicomponent melt-spinning. The sheath-core TRF(TRF_(sc)) are composed of PA6 as sheath and functional PA6 as core, which are filled with the shape stable phase change materials(ssPCM),dendritic silica@polyethylene glycol(SiO_(2)@PEG). With the aid of the sheath structure, the filling content of SiO_(2)@PEG can reach 30 %, so that the enthalpy of the TRF_(s) can be as high as 21.3 J/g. The ultra-high enthalpy guarantees the temperature regulation ability during the alternating process of cooling and heating. In hot environment, the temperature regulation time is 6.59 min, and the temperature difference is 12.93℃. In addition, the mechanical strength of the prepared TRF_(sc) reaches 2.26 cN/dtex, which can fully meet its application in the field of thermal management textiles and devices to manage the temperature regulation of the human body or precision equipment, etc.