HfMgMo（3-x）WxO（12） with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structu...HfMgMo（3-x）WxO（12） with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structure for x≤2.0 and a monoclinic structure for x2.0. A near-zero thermal expansion（ZTE） is realized for HfMgMo（2.5）W（0.5）O（12） and negative coefficients of thermal expansion（NCTE） are achieved for other compositions with different values. The ZTE and variation of NCTE are attributed to the difference in electronegativity between W and Mo and incorporation of a different amount of W, which cause variable distortion of the octahedra and softening of the MoO4 tetrahedra, and hence an enhanced NCTE in the a- and c-axis and reduced CTE in the b-axis as revealed by Raman spectroscopy and x-ray diffraction.展开更多
Exploring new abnormal thermal expansion materials is important to understand the nature of thermal expansion.Metal-organic framework(MOF)with unique structure flexibility is an ideal material to study the thermal exp...Exploring new abnormal thermal expansion materials is important to understand the nature of thermal expansion.Metal-organic framework(MOF)with unique structure flexibility is an ideal material to study the thermal expansion.This work adopts the high-resolution variable-temperature powder x-ray diffraction to investigate the structure and intrinsic thermal expansion in Sr-MOF([Sr(DMPhH_(2)IDC)_(2)]_n).It has the unique honeycomb structure with one-dimensional(1 D)channels along the c-axis direction,the a-b plane displays layer structure.The thermal expansion behavior has strong relationship with the structure,ZTE appears in the a-b plane and large PTE along the c-axis direction.The possible mechanism is that the a/b layers have enough space for the transverse thermal vibration of polydentate ligands,while along the c-axis direction is not.This work not only reports one interesting zero thermal expansion material,but also provides new understanding for thermal expansion mechanism from the perspective of the structural model.展开更多
Zero thermal expansion materials are important for the practical applications due to their shape stability as changing temperature.The reported concept of average atomic volume is an available method to hunt new zero ...Zero thermal expansion materials are important for the practical applications due to their shape stability as changing temperature.The reported concept of average atomic volume is an available method to hunt new zero thermal expansion materials.Here,according to this concept,a tetragonal tungstate Cs_(2)W_(3)O_(10)with zero expansion has been found.There is no structure phase transition as increasing temperature from 150 K to 573 K.The coefficient of thermal expansion of axes and volume areαa=0.0074×10^(-6)K^(-1),αc=1.63×10^(-6)K^(-1),andαV=1.60×10^(-6)K^(-1),respectively,in the temperature range of 150~573 K.The temperature-and pressure-dependent Raman spectra reveal that the vibrations of WO6octahedra libration modes with positive total anharmonicity and W-O-W bending mode with negative Grüneisen parameter are possibly the origin of zero thermal expansion in Cs_(2)W_(3)O_(10).展开更多
MgZn_(2)-type(Hf,Ta)Fe_(2),known for its negative thermal expansion during magnetic transition,is a key component in the production of zero thermal expansion composites.This paper presents a basic approach for designi...MgZn_(2)-type(Hf,Ta)Fe_(2),known for its negative thermal expansion during magnetic transition,is a key component in the production of zero thermal expansion composites.This paper presents a basic approach for designing such composites by introducing an additional Laves phase through atomic substitution.Specifically,Co,Ni,A1 and V were chosen to substitute Fe in(Hf,Ta)Fe_(2).The addition of Co or Ni results in the creation of an extra MgCu_(2)(C15)phase in the MgZn_(2)(C14)matrix.The C15phase exhibits positive thermal expansion,which effectively compensates for the negative thermal expansion of the C14 matrix.By adjusting the amount of Co or Ni,zero thermal expansion can be achieved in a given temperature range.Meanwhile,the replacement of Fe by Al or V yields another C14 phase with a higher doping element content relative to the C14 matrix.These two C14 phases possess different magnetic transition temperatures and negative thermal expansion temperature regions.The combination of the two C14 phases results in zero thermal expansion due to the effective thermal expansion compensation between them.Our results serve to identify potential approaches for designing(Hf,Ta)Fe_(2)-based zero thermal expansion composites.展开更多
The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with...The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with the heat treatment of 720℃/3 h+800℃/1.5 h while the crystallinity and crystal size increase with the increase of Li2O contents.Due to the negative thermal expansion coefficient of h/l-quartz s.s.,the thermal expansion coefficient of glass-ceramics decreases with the increasing of Li2O contents.When the Li2O content is 9mol%,the near-zero CTE20-700℃=-0.09×10^(-6)℃^(-1) is obtained upon the heat treatment of 720℃/3 h+800℃/1.5 h.The crystallization activation energy of the glass with 9mol%Li2O is about 351 kJ/mol,and the crystallization mechanism is volume crystallization.展开更多
Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and c...Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and charge upon heating,have limited the ZTE alloys by very few numbers of species.In this work,we report a route to achieving twodimensional(2D)ZTE behavior by regulating crystallographic texture and magneto-volume effects(MVEs)in volumetric positive thermal expansion alloys.This is illustrated in a series of Mn_(x)Fe_(5-x)Si_(3)compounds by those earth-abundant elements.As a result,a 2D ZTE performance with a coefficient of thermal expansion α_(1)=0.45×10^(-7)K^(-1) over a broad temperature window of 10–310 K was observed in MnFe4Si3.The experimental results by synchrotron X-ray diffraction,neutron diffraction,microscopy,and magnetization measurements reveal that such a ZTE behavior is strongly coupled with fiber crystallographic texture and magnetic moment at the crystallographic 6g site that dominates MVEs in the a-b plane.The competition between ferromagnetic Fe_(4d)–Fe_(6g)(J_(FM))and antiferromagnetic Mn_(4d)–Mn_(6g)(J_(AFM))interactions makes the Mn_(1.5)Fe_(3.5)Si_(3) and Mn_(2)Fe_(3)Si_(3)compounds show mixed magnetism and negative thermal expansion(NTE).The integral approach presented here can be used to extend the scope of ZTE/NTE species in other magnetic or ferroelectric materials.展开更多
Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and te...Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and temperature windows.In this study,we report a novel class of near-zero thermal expansion(near ZTE)alloys,ErFe_(10)V_(2−x)Mo_(x),over a wide temperature range(120–440 K).Neutron diffraction and magnetic measurements demonstrated that the ErFe_(10)V_(2−x)Mo_(x)compounds exhibited complex ferrimagnetic(FIM)structures below Curie temperature(TC).The near-ZTE behaviors were closely related to the itinerant Fe 3d moments in the collinear FIM states,as well as the geometric[−Fe−Fe−]linkages.Further,X-ray absorption near-edge structure(XANES)spectra revealed that the nonmagnetic substitution changed the electronic valence states of Fe atoms,which,in turn,changed Fe 3d moments and TC,hence,regulating the thermal expansion behaviors.Our work provides an insight into chemical modifications of thermal expansion in magnetic intermetallic compounds.展开更多
Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a...Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a non-collinear antiferromagnetic(AFM)phase at room temperature(RT).Signifi-cantly,the discovery of novel materials with nearly zero thermal expansion(ZTE)property near RT is required and pursued for avoiding thermal stress and fracture in spintronic devices.Herein,the doping of Sn(Ge)at the Ag site in the triangular lattice Mn_(3)Ag_(1-x)Sn(Ge)_(x)N compounds increases effectively the Neel point and makes the interesting non-collinearГ^(5g)AFM phase exist above RT.The magnetic phase diagrams withГ^(5g)phase up to 498 K were built by the combined analysis of neutron powder diffraction(NPD),magnetic measurements,electronic transport,and differential scanning calorimetry(DSC).The thermal expansion behaviors of Mn_(3)Ag_(1-x)Sn(Ge)_(x)N were modulated,and the nearly ZTE above RT was achieved in Mn_(3)Ag_(0.5)Ge_(0.5)N withinГ^(5g)AFM ordering.Our findings offer an effective way to tailor the non-collinear AFM ordering and correlated thermal expansion behavior for potential use in the emerging field of thermal stress-free magnetic chip materials.展开更多
The existence and multiplicity of positive solutions to a periodic boundary value problem for nonlinear third-order ordinary differential equation are established,based on the zero point theorem concerning cone expans...The existence and multiplicity of positive solutions to a periodic boundary value problem for nonlinear third-order ordinary differential equation are established,based on the zero point theorem concerning cone expansion and compression of order type.Our main approach is different from the previous papers on the existence of multiple positive solutions to the similar problem.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.10974183 and 11104252)the Key Natural Science Project of Henan Province,China(Grant No.142102210073)+1 种基金the Doctoral Fund of the Ministry of Education of China(Grant No.20114101110003)the Fund for Science & Technology Innovation Team of Zhengzhou,China(Grant No.112PCXTD337)
文摘HfMgMo（3-x）WxO（12） with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structure for x≤2.0 and a monoclinic structure for x2.0. A near-zero thermal expansion（ZTE） is realized for HfMgMo（2.5）W（0.5）O（12） and negative coefficients of thermal expansion（NCTE） are achieved for other compositions with different values. The ZTE and variation of NCTE are attributed to the difference in electronegativity between W and Mo and incorporation of a different amount of W, which cause variable distortion of the octahedra and softening of the MoO4 tetrahedra, and hence an enhanced NCTE in the a- and c-axis and reduced CTE in the b-axis as revealed by Raman spectroscopy and x-ray diffraction.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.22071221 and 21905252)the Natural Science Foundation of Henan Province,China(Grant No.212300410086)。
文摘Exploring new abnormal thermal expansion materials is important to understand the nature of thermal expansion.Metal-organic framework(MOF)with unique structure flexibility is an ideal material to study the thermal expansion.This work adopts the high-resolution variable-temperature powder x-ray diffraction to investigate the structure and intrinsic thermal expansion in Sr-MOF([Sr(DMPhH_(2)IDC)_(2)]_n).It has the unique honeycomb structure with one-dimensional(1 D)channels along the c-axis direction,the a-b plane displays layer structure.The thermal expansion behavior has strong relationship with the structure,ZTE appears in the a-b plane and large PTE along the c-axis direction.The possible mechanism is that the a/b layers have enough space for the transverse thermal vibration of polydentate ligands,while along the c-axis direction is not.This work not only reports one interesting zero thermal expansion material,but also provides new understanding for thermal expansion mechanism from the perspective of the structural model.
基金supported by the National Natural Science Foundation of China(Nos.22071221,21905252)Natural Science Foundation of Henan Province(Nos.212300410086,222301420040 and 222300420325)。
文摘Zero thermal expansion materials are important for the practical applications due to their shape stability as changing temperature.The reported concept of average atomic volume is an available method to hunt new zero thermal expansion materials.Here,according to this concept,a tetragonal tungstate Cs_(2)W_(3)O_(10)with zero expansion has been found.There is no structure phase transition as increasing temperature from 150 K to 573 K.The coefficient of thermal expansion of axes and volume areαa=0.0074×10^(-6)K^(-1),αc=1.63×10^(-6)K^(-1),andαV=1.60×10^(-6)K^(-1),respectively,in the temperature range of 150~573 K.The temperature-and pressure-dependent Raman spectra reveal that the vibrations of WO6octahedra libration modes with positive total anharmonicity and W-O-W bending mode with negative Grüneisen parameter are possibly the origin of zero thermal expansion in Cs_(2)W_(3)O_(10).
基金financially supported by the National Natural Science Foundation of China(No.11974184)JiangSu Undergraduate Training Program for Innovation and Entrepreneurship(No.202310288172Y)。
文摘MgZn_(2)-type(Hf,Ta)Fe_(2),known for its negative thermal expansion during magnetic transition,is a key component in the production of zero thermal expansion composites.This paper presents a basic approach for designing such composites by introducing an additional Laves phase through atomic substitution.Specifically,Co,Ni,A1 and V were chosen to substitute Fe in(Hf,Ta)Fe_(2).The addition of Co or Ni results in the creation of an extra MgCu_(2)(C15)phase in the MgZn_(2)(C14)matrix.The C15phase exhibits positive thermal expansion,which effectively compensates for the negative thermal expansion of the C14 matrix.By adjusting the amount of Co or Ni,zero thermal expansion can be achieved in a given temperature range.Meanwhile,the replacement of Fe by Al or V yields another C14 phase with a higher doping element content relative to the C14 matrix.These two C14 phases possess different magnetic transition temperatures and negative thermal expansion temperature regions.The combination of the two C14 phases results in zero thermal expansion due to the effective thermal expansion compensation between them.Our results serve to identify potential approaches for designing(Hf,Ta)Fe_(2)-based zero thermal expansion composites.
基金Funded by the Opening Project of State Key Laboratory of Special Glass and the National Natural Science Foundation of China(No.52072278)。
文摘The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with the heat treatment of 720℃/3 h+800℃/1.5 h while the crystallinity and crystal size increase with the increase of Li2O contents.Due to the negative thermal expansion coefficient of h/l-quartz s.s.,the thermal expansion coefficient of glass-ceramics decreases with the increasing of Li2O contents.When the Li2O content is 9mol%,the near-zero CTE20-700℃=-0.09×10^(-6)℃^(-1) is obtained upon the heat treatment of 720℃/3 h+800℃/1.5 h.The crystallization activation energy of the glass with 9mol%Li2O is about 351 kJ/mol,and the crystallization mechanism is volume crystallization.
基金supported by the National Key R&D Program of China(2020YFA0406202)the National Natural Science Foundation of China(22090042,21971009 and 21731001)+1 种基金the Fundamental Research Funds for the Central Universities,China(FRF-IDRY-19-018 and FRF-BR-19-003B)Neutron texture analysis was carried out at the Spallation Neutron Source(SNS)(Proposal No.2020B26069)。
文摘Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and charge upon heating,have limited the ZTE alloys by very few numbers of species.In this work,we report a route to achieving twodimensional(2D)ZTE behavior by regulating crystallographic texture and magneto-volume effects(MVEs)in volumetric positive thermal expansion alloys.This is illustrated in a series of Mn_(x)Fe_(5-x)Si_(3)compounds by those earth-abundant elements.As a result,a 2D ZTE performance with a coefficient of thermal expansion α_(1)=0.45×10^(-7)K^(-1) over a broad temperature window of 10–310 K was observed in MnFe4Si3.The experimental results by synchrotron X-ray diffraction,neutron diffraction,microscopy,and magnetization measurements reveal that such a ZTE behavior is strongly coupled with fiber crystallographic texture and magnetic moment at the crystallographic 6g site that dominates MVEs in the a-b plane.The competition between ferromagnetic Fe_(4d)–Fe_(6g)(J_(FM))and antiferromagnetic Mn_(4d)–Mn_(6g)(J_(AFM))interactions makes the Mn_(1.5)Fe_(3.5)Si_(3) and Mn_(2)Fe_(3)Si_(3)compounds show mixed magnetism and negative thermal expansion(NTE).The integral approach presented here can be used to extend the scope of ZTE/NTE species in other magnetic or ferroelectric materials.
基金supported by the National Natural Science Foundation of China(21701008,21231001,21590793,and 21731001)National Postdoctoral Program for Innovative Talents(BX201700027)the Fundamental Research Funds for the Central Universities,China(FRF-IDRY-19-018).
文摘Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and temperature windows.In this study,we report a novel class of near-zero thermal expansion(near ZTE)alloys,ErFe_(10)V_(2−x)Mo_(x),over a wide temperature range(120–440 K).Neutron diffraction and magnetic measurements demonstrated that the ErFe_(10)V_(2−x)Mo_(x)compounds exhibited complex ferrimagnetic(FIM)structures below Curie temperature(TC).The near-ZTE behaviors were closely related to the itinerant Fe 3d moments in the collinear FIM states,as well as the geometric[−Fe−Fe−]linkages.Further,X-ray absorption near-edge structure(XANES)spectra revealed that the nonmagnetic substitution changed the electronic valence states of Fe atoms,which,in turn,changed Fe 3d moments and TC,hence,regulating the thermal expansion behaviors.Our work provides an insight into chemical modifications of thermal expansion in magnetic intermetallic compounds.
基金supported by the financial support of National Key R&D Program of China(2022YFA1402600)National Natural Science Foundation of China(NSFC)(52272264)+1 种基金Sino-German Mobility Programme Project(M-0273)the Guangdong Basic and Applied Basic Research Foundation(2022A1515140117).
文摘Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a non-collinear antiferromagnetic(AFM)phase at room temperature(RT).Signifi-cantly,the discovery of novel materials with nearly zero thermal expansion(ZTE)property near RT is required and pursued for avoiding thermal stress and fracture in spintronic devices.Herein,the doping of Sn(Ge)at the Ag site in the triangular lattice Mn_(3)Ag_(1-x)Sn(Ge)_(x)N compounds increases effectively the Neel point and makes the interesting non-collinearГ^(5g)AFM phase exist above RT.The magnetic phase diagrams withГ^(5g)phase up to 498 K were built by the combined analysis of neutron powder diffraction(NPD),magnetic measurements,electronic transport,and differential scanning calorimetry(DSC).The thermal expansion behaviors of Mn_(3)Ag_(1-x)Sn(Ge)_(x)N were modulated,and the nearly ZTE above RT was achieved in Mn_(3)Ag_(0.5)Ge_(0.5)N withinГ^(5g)AFM ordering.Our findings offer an effective way to tailor the non-collinear AFM ordering and correlated thermal expansion behavior for potential use in the emerging field of thermal stress-free magnetic chip materials.
基金supported by the National Natural Science Foundation of China(10971179)the Natural Science Foundation of Changzhou University(JS201008)
文摘The existence and multiplicity of positive solutions to a periodic boundary value problem for nonlinear third-order ordinary differential equation are established,based on the zero point theorem concerning cone expansion and compression of order type.Our main approach is different from the previous papers on the existence of multiple positive solutions to the similar problem.
