Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting materi...Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting material. The effects of process variables, such as deformation temperature （Td）, strain rate （ε） and height reduction （△h%）, on the magnetic properties of the rings are investigated. A scanning electron microscope （SEM） equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and （BH）max reach the optimum values at Td =800℃,ε= 0.01 mm/s, and △h% = 70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fel4B nanograins along the easy growth a-axis.展开更多
In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DTA analysis on the ...In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DTA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (TbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. This phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by Dy and/or Co. The 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. The grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. The grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). Typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were iHc=4.85 kOe, Br= 11.32 kG, (BH)max = 15.73 MGOe, and mr=0.73.展开更多
Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infue...Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(<10-2m s-1)and R(5.06×103?C s-1)increased,part of theα-Fe soft magnetic phase(31.7vol.%)is suppressed,and a higher volume of Nd2Fe17Bxmetastable phases(47.5 vol.%)areformed.As a result,both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties.In contrast,employing the high values of V(>10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP(Nd-lean)Nd-Fe-Bpowder.展开更多
The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Ndl2.3Fe81.7-xCuxB6 （x=0-1.2） ribbons melt-spun and annealed were systematically investigated by the methods of vib...The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Ndl2.3Fe81.7-xCuxB6 （x=0-1.2） ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550℃ for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum energy product increase by 18.4%, 36.2%, and 49% respectively compared with those of Cu-free samples. The sig- nificant improvement in magnetic properties originates from the freer grains of the samples by introducing Cu, which leads to the stronger exchange-coupling between neighboring grains.展开更多
Structure and magnetic properties of the nanocomposite magnets prepared by mechanical al loying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct α-Fe,55 wt pct Nd(Fe0.8-.Co0.12Nbx B0.08)5.5+45 wt p...Structure and magnetic properties of the nanocomposite magnets prepared by mechanical al loying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct α-Fe,55 wt pct Nd(Fe0.8-.Co0.12Nbx B0.08)5.5+45 wt pct α-Fe (x=0.00, 0.01- 0.03) and 55 wt pct (Nd0.9Dy0.1) (Fe0.77Co0.12Nb0.03B0.08)5.5+45 wt pct α-Fe were studied. It was found that substitution of Co for Fe could significantly improve the permanent magnetic properties of the nanocomposite magnets and typically, the maximum magnetic energy product was increased from 104.8 kJ/m3 (13.1 MGOe) to 141.6 kJ/m3 (17.7 MGOe). In contrast to the case of conventional nominally single-phase magnets, the addition of Nb results in promoting the growth of α-Fe grain and is thus unfavorable for the improvement of permanent magnetic properties of the nanocomposites. Although the addition of Dy can increase the coercivity of the magnets, the increase of magnetic anisotropy of hard phase leads to decrease of the critical grain size of soft phase. Additionally it causes the difficulty of preparing the nanocomposites because it is more difficult to control the grain size of soft phase to meet the requirement of appropriate exchange coupling between hard and soft grains展开更多
This thesis investigates the influence of zinc oxide (ZnO) on the thermophysical characteristics of natural polymer-based nanofluids. The focus is on pectin nanofluids with incorporated ZnO nanoparticles. In this expe...This thesis investigates the influence of zinc oxide (ZnO) on the thermophysical characteristics of natural polymer-based nanofluids. The focus is on pectin nanofluids with incorporated ZnO nanoparticles. In this experiment, varying concentrations of zinc oxide (ZnO) were combined with a constant amount of pectin to study their effects on the final solution’s characteristics. Initially, ZnO and pectin solutions were prepared individually and subjected to magnetic stirring and sonication. The experiment involved three different concentrations of ZnO: 0.1 g, 0.02 g, and 0.03 g, while the weight of pectin remained constant at 0.05g throughout. After individual preparation, the solutions were mixed, further stirred, and subjected to sonication. Two analysis techniques, Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA), were employed to characterize the samples. SEM provided insights into surface morphology and chemical composition, while TGA analyzed mass changes over temperature variations, offering valuable information on material properties. The significance and applications of these techniques in material characterization and analysis were discussed, highlighting their roles in understanding physical and chemical phenomena. The presence of ZnO nanoparticles enhanced the thermal stability of the pectin nanofluids. Contact angle measurements were performed to evaluate the hydrophilicity of the nanofluids. The contact angle trend indicated an increase in hydrophobicity with an increasing concentration of ZnO in the pectin nanofluids. The measured contact angles supported the high stability of the synthesized nanofluids. Overall, this study provides valuable insights into the incorporation of ZnO nanoparticles into pectin nanofluids and their impact on the thermophysical characteristics. The findings contribute to the development of nanofluids for potential applications in drug release and biomedical fields.展开更多
The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and morta...The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.展开更多
Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique wa...Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.展开更多
In line with recent studies,where it has been shown that nanofluids containing graphene have a stronger capacity to boost the heat transfer coefficient with respect to ordinary nanofluids,experiments have been conducted ...In line with recent studies,where it has been shown that nanofluids containing graphene have a stronger capacity to boost the heat transfer coefficient with respect to ordinary nanofluids,experiments have been conducted using water with cobalt ferrite/graphene nanoparticles.In particular,a circular channel made of copper subjected to a constant heatflux has been considered.As nanoparticles are sensitive to the presence of a magneticfield,different conditions have been examined,allowing both the strength and the frequency of such afield to span relatively wide ranges and assuming different concentrations of nanoparticles.According to thefindings,the addition of nanoparticles to thefluid causes its rotation speed to increase by a factor of two,whereas ultraviolet radiation plays a negligible role.The amount of time required to attain the maximum rotation speed of the nanofluid and the Nusselt number have been measured under both constant and alternating magneticfields for a ferrofluid with a concentration of 0.5%and atflow Reynolds number of 550 and 1750.展开更多
Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rat...Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.展开更多
WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravi...WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.展开更多
Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinic...Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinical use up to now,biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment.Polyethylene glycol(PEG)-modification(or PEGylation)has been regarded as the gold standard for stabilising nDDS in complex biological environment.However,the accelerated blood clearance(ABC)of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications.Zwitterionic polymer,a novel family of antifouling materials,have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility.Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues.More impressively,zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution,pressure gradients,impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications.The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS,which could facilitate their better clinical translation.Herein,we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlyingmechanisms.Finally,prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 50804011 and 50931001)
文摘Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting material. The effects of process variables, such as deformation temperature （Td）, strain rate （ε） and height reduction （△h%）, on the magnetic properties of the rings are investigated. A scanning electron microscope （SEM） equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and （BH）max reach the optimum values at Td =800℃,ε= 0.01 mm/s, and △h% = 70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fel4B nanograins along the easy growth a-axis.
文摘In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DTA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (TbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. This phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by Dy and/or Co. The 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. The grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. The grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). Typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were iHc=4.85 kOe, Br= 11.32 kG, (BH)max = 15.73 MGOe, and mr=0.73.
基金supported by the National Key R&D Program of China(Grant No.2022YFB4600300)the National Natural Science Foundation of China(No.U22A20189,52175364)the China Scholarship Council(Grant No.202206290134)。
文摘Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(<10-2m s-1)and R(5.06×103?C s-1)increased,part of theα-Fe soft magnetic phase(31.7vol.%)is suppressed,and a higher volume of Nd2Fe17Bxmetastable phases(47.5 vol.%)areformed.As a result,both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties.In contrast,employing the high values of V(>10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP(Nd-lean)Nd-Fe-Bpowder.
文摘The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Ndl2.3Fe81.7-xCuxB6 （x=0-1.2） ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550℃ for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum energy product increase by 18.4%, 36.2%, and 49% respectively compared with those of Cu-free samples. The sig- nificant improvement in magnetic properties originates from the freer grains of the samples by introducing Cu, which leads to the stronger exchange-coupling between neighboring grains.
文摘Structure and magnetic properties of the nanocomposite magnets prepared by mechanical al loying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct α-Fe,55 wt pct Nd(Fe0.8-.Co0.12Nbx B0.08)5.5+45 wt pct α-Fe (x=0.00, 0.01- 0.03) and 55 wt pct (Nd0.9Dy0.1) (Fe0.77Co0.12Nb0.03B0.08)5.5+45 wt pct α-Fe were studied. It was found that substitution of Co for Fe could significantly improve the permanent magnetic properties of the nanocomposite magnets and typically, the maximum magnetic energy product was increased from 104.8 kJ/m3 (13.1 MGOe) to 141.6 kJ/m3 (17.7 MGOe). In contrast to the case of conventional nominally single-phase magnets, the addition of Nb results in promoting the growth of α-Fe grain and is thus unfavorable for the improvement of permanent magnetic properties of the nanocomposites. Although the addition of Dy can increase the coercivity of the magnets, the increase of magnetic anisotropy of hard phase leads to decrease of the critical grain size of soft phase. Additionally it causes the difficulty of preparing the nanocomposites because it is more difficult to control the grain size of soft phase to meet the requirement of appropriate exchange coupling between hard and soft grains
文摘This thesis investigates the influence of zinc oxide (ZnO) on the thermophysical characteristics of natural polymer-based nanofluids. The focus is on pectin nanofluids with incorporated ZnO nanoparticles. In this experiment, varying concentrations of zinc oxide (ZnO) were combined with a constant amount of pectin to study their effects on the final solution’s characteristics. Initially, ZnO and pectin solutions were prepared individually and subjected to magnetic stirring and sonication. The experiment involved three different concentrations of ZnO: 0.1 g, 0.02 g, and 0.03 g, while the weight of pectin remained constant at 0.05g throughout. After individual preparation, the solutions were mixed, further stirred, and subjected to sonication. Two analysis techniques, Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA), were employed to characterize the samples. SEM provided insights into surface morphology and chemical composition, while TGA analyzed mass changes over temperature variations, offering valuable information on material properties. The significance and applications of these techniques in material characterization and analysis were discussed, highlighting their roles in understanding physical and chemical phenomena. The presence of ZnO nanoparticles enhanced the thermal stability of the pectin nanofluids. Contact angle measurements were performed to evaluate the hydrophilicity of the nanofluids. The contact angle trend indicated an increase in hydrophobicity with an increasing concentration of ZnO in the pectin nanofluids. The measured contact angles supported the high stability of the synthesized nanofluids. Overall, this study provides valuable insights into the incorporation of ZnO nanoparticles into pectin nanofluids and their impact on the thermophysical characteristics. The findings contribute to the development of nanofluids for potential applications in drug release and biomedical fields.
文摘The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.
文摘Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.
文摘In line with recent studies,where it has been shown that nanofluids containing graphene have a stronger capacity to boost the heat transfer coefficient with respect to ordinary nanofluids,experiments have been conducted using water with cobalt ferrite/graphene nanoparticles.In particular,a circular channel made of copper subjected to a constant heatflux has been considered.As nanoparticles are sensitive to the presence of a magneticfield,different conditions have been examined,allowing both the strength and the frequency of such afield to span relatively wide ranges and assuming different concentrations of nanoparticles.According to thefindings,the addition of nanoparticles to thefluid causes its rotation speed to increase by a factor of two,whereas ultraviolet radiation plays a negligible role.The amount of time required to attain the maximum rotation speed of the nanofluid and the Nusselt number have been measured under both constant and alternating magneticfields for a ferrofluid with a concentration of 0.5%and atflow Reynolds number of 550 and 1750.
基金supported by the Key Research and Development Plan of Shaanxi Province (2023-GHZD-12)the Opening Fund of State Key Laboratory for Strength and Vibration of Mechanical Structures (SVL2021-KF-12)+1 种基金Fundamental Research Funds for the Central Universities (G2020KY05112)the 111 Project (BP0719007)
文摘Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.
基金Funded by the National Key Research and Development Plan of China(No.2017YFB0305900)。
文摘WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.
基金financially supported by the National Natural Science Foundation of China(grant no.8217070298)Guangdong Basic and Applied Basic Research Foundation(grant no.2020A1515110770,2021A1515220011,2022A1515010335).
文摘Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinical use up to now,biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment.Polyethylene glycol(PEG)-modification(or PEGylation)has been regarded as the gold standard for stabilising nDDS in complex biological environment.However,the accelerated blood clearance(ABC)of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications.Zwitterionic polymer,a novel family of antifouling materials,have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility.Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues.More impressively,zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution,pressure gradients,impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications.The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS,which could facilitate their better clinical translation.Herein,we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlyingmechanisms.Finally,prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.
