The Calculations of 3-Dimensional Ising Model of Finite Width

In order to calculate 3-dimensional Ising model,we develop a method to build a much smaller transfer matrix containing the largest eigenvalue from the original 2^(N_1N_2) × 2^(N_1N_2) matrix V_1. Firstly,the transfer matrix V_1 is written as the linear combination of several basic vectors. Secondly,we divide the basic vectors into several subgroups. The multiplication of a basic vector and V_1 can be written as the linear combination of basic vectors from the same subgroup. Finally,we use a new transfer matrix V_2 to describe the relationship between basic vectors of the same subgroup.V_2 is much smaller than the original transfer matrix and contains the largest eigenvalue of V_1.We use this method to calculate the specific heat per atom Cpaand the magnetic momentum per atom Mpa. The results show that there exists a pair of temperature and magnetic field intensity where the specific heat gets to its maximum value. When N_1N_2 increases,the maximum value of specific heat becomes larger.

Effect of Al_(82.8)Cu_(17)Fe_(0.2) alloy doping on structure and magnetic properties of SmCo5-based ribbons

This work tries to improve the magnetic properties by multi-element doping in the form of a ternary alloy.SmCo_(5+)χwt%Al-Cu-Fe(x=0-7)ribbons melt-spun at 40 m/s were produced by adding Al_(82.8)Cu_(17)Fe_(0.2)alloy into SmCo_(5) matrix,and their phases,microstructure,and magnetic properties were investigated.The results show that both x=0 and 3 ribbons form a cellular microstructure.Al-Cu-Fe addition reduces the content of the Sm_(2)(Co,M)_(7) cell wall,narrows its width,and forms the local disordered micro-regions and solute-segregation nanoclusters in the Sm(Co,M)_(5) grains.With x increasing to5,Al-Cu-Fe addition promotes the phase separation between and within grains of the SmCo_(5)-based alloy.The Al-Cu-Fe addition can simultaneously improve the coercivity and magnetization of the SmCo_(5)-based ribbons,in particular,the magnetization of the x=3 ribbons increases by 35%,while the coercivity of the x=5 ribbons increases by 3.9 times.Finally,the microstructure evolution models are built up,and the relationship between the microstructure and the magnetic properties is discussed.

Microstructure and properties evolution of plasma sprayed Al_(2)O_(3)-Y_(2)O_(3) composite coatings during high temperature and thermal shock treatment

Al_(2)O_(3)-Y_(2)O_(3) composite powder with TiO_(2) additive was plasma sprayed to prepare Al_(2)O_(3)-Y_(2)O_(3) composite coatings.The micro structure and properties evolution of the Al_(2)O_(3)-Y_(2)O_(3) coatings during high temperature and thermal shock resistance were investigated.The results show that the micro structure of the Al_(2)O_(3)-Y_(2)O_(3)-TiO_(2) coating is more uniform than that of the Al_(2)O_(3)-Y_(2)O_(3) coating.Meanwhile,amorphous phase is formed in the two coatings.The Al_(2)O_(3)-Y_(2)O_(3)(-TiO_(2)) coatings were heat treated for 2 h at temperatures of 800,1000 and 1200℃,respectively.It is found that the microstructure and properties of the two coatings have no obvious change at 800℃.Some of the amorphous phase is crystallized at1000℃,and meanwhile Y_(2)O_(3) and Al_(2)O_(3) react to form YAG phase and YAM phase.At 1200℃,all of the amorphous phases are crystallized.After heat treatment,the micro hardness of the two coatings is increased.The thermal shock resistance of the Al_(2)O_(3)-Y_(2)O_(3) system coatings can be improved by using TC4 titanium alloy as substrate and with NiCrAlY bonding layer.Moreover,the Al_(2)O_(3)-Y_(2)O_(3)-TiO_(2) coating exhibits better thermal shock resistance due to the addition of TiO_(2).

In-situ synthesis,microstructure,and properties of NbB_(2)-NbC-Al_(2)O_(3)composite coatings by plasma spraying

The high melting point and strong chemical bonding of NbB_(2)pose a great challenge to the preparation of high-density nanostructured NbB_(2)composite coating.Herein,we report a novel,simple,and efficient method to fabricate in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating by plasma spraying Nb_(2)O_(5)–B_(4)C–Al composite powder,aiming at realizing the higher densification and ultra-fine microstructure of NbB_(2)composite coating.The microstructure and properties of in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating were studied comparatively with ex-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating(plasma spraying NbB_(2)–NbC–Al_(2)O_(3)composite powder).The reaction mechanism of Nb_(2)O_(5)–B_(4)C–Al composite powder in plasma jet was analyzed in detail.The results showed that the in-situ nanostructured NbB_(2)–NbC–Al_(2)O_(3)composite coating presented a lower porosity and superior performance including higher microhardness,toughness and wear resistance compared to the plasma sprayed ex-situ NbB_(2)–NbC–Al_(2)O_(3)coating and other boride composite coatings.Densification of the in-situ NbB_(2)–NbC–Al_(2)O_(3)coating was attributed to the low melting point of Nb_(2)O_(5)–B_(4)C–Al composite powder and the exothermic effect of in-situ reaction.The superior performance was ascribed to the density improvement and the strengthening and toughening effect of the nanosized phases.The in-situ reaction path could be expressed as:Nb_(2)O_(5)+Al®Nb+Al_(2)O_(3),and Nb+B_(4)C®NbB_(2)+NbC.

Effects of cobalt addition on microstructure and magnetic properties of PrNdFeB/Fe7Co3 nanocomposite

The permanent magnetic nanocomposite PrNdFeB/Fe7Co3 ribbons were prepared by directly quenching, and the microstructure and magnetic influence of composite materials with Co substitution were studied. The phase identification and the magnetic properties were measured by X-ray diffraction（XRD） and vibrating sample magnetometry（VSM）. Microstructure observation was performed using scanning electron microscopy（SEM）. The crystallization temperatures of the hard magnetic phase and the soft magnetic phase were measured using differential scanning calorimetry（DSC）. The experimental results showed that Co addition improved the Curie temperature of magnets. When the ribbons were melt-spun at 35 m/s, the added content of Co was 4 at.%, and the magnetic properties were the best, which were remanence（Br） of 0.379 T, coercivity（Hci） of 344.4 kA/m, the maximum magnetic energy product（BH）max of 32.6 kJ/m^3. Besides, the activation energy of each phase was calculated by Kissinger equation, which was 310.4 kJ/mol of Fe7Co3 phase and 510.2 kJ/mol of 2：14：1 phase, respectively.

Electrochemical synthesis,structure characterization and magnetic properties of Tb_(x)Fe_(7)Co_(3)(x=0,0.6,0.8) nanowires

Highly ordered Tb_(x)Fe_(7)Co_(3)(x=0,0.6,0.8)nanowires were synthesized in alumina templates by electrochemical deposition method.Here,the effects of Tb content and annealing treatment on the phase composition,morphology,crystalline structure and magnetic properties were investigated.The asdeposited Tb_0 Fe_(7)Co_(3)nanowires comprise Fe_(7)Co_(3)phase.While after adding Tb,the diffraction peaks slightly shift left,indicating the infiltration of Tb atoms into Fe_(7)Co_(3)phase.After annealing,Tb_0 Fe_(7)Co_(3)nanowires still consist of Fe_(7)Co_(3)phase with a slight enhancement on coercivity.While the annealed nanowires with Tb doped present a complex phase composition containing Fe3 Tb,Fe_(2)Tb,Co_(3)Tb,Co_(17)Tb_(2),TbFeO_(3)and Fe_(2)O_(3)phases distribute in the central portion,and Co_(0.72)Fe_(0.28)at the nanowire outer walls.The annealed Tb_(x)Fe_(7)Co_(3)(x=0.6,0.8)nanowires show higher magnetic performance owing to the formation of hard magnetic phases,the interfacial elastic coupling between hard and soft phases and the coherent Fe3 Tb/Co_(3)Tb interface which restrain the domain wall motion.To be specific,the coercivity and remanence ratio of TbxFe_(7)Co_(3)(x=0.6,0.8)nanowires significantly enhance with increasing Tb content.