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Nowadays, casted multicrystalline silicon is the most important material in photovoltaic industry. In order to reduce the cost of silicon ingots, the recycle of silicon ingot tailings is explored. In this paper, the secondary utilization of silicon block tailings with a thickness of 25 mm, matched with process of diamond wire saw machine was studied. The comparative analysis on technical parameters of bottom red zone and wafers generated by virgin crushed polycrystalline silicon feedstock and secondary utilized tailings was discussed. The result shows that recycle of tailing seeds is feasible. The above-mentioned tailings of diamond wire saw ingots shall be with a thickness of 25 mm. The bottom red zone of area paved by tailings is 2 mm longer than that in area paved by virgin crushed polycrystalline silicon feedstock. But the difference of cell conversion efficiency is negligible, 0.01% lower. Consequently, it is feasible to recycle high-efficiency multicrystalline ingots tailings, which push forward further cost reduction of high-efficiency multicrystalline ingots.

The phase stability, martensitic transition and magnetism of Zn-doped Heusler alloys Mn2NiGa1-xZnx (x = 0, 0.25, 0.5, 0.75, 1) were investigated by first-principles calculations. In Mn2NiGa1-xZnx, Zn atom plays a similar role like main-group element Ga and also occupies the D site. A possible reason for this is the closed 3d-shell of Zn. The austenite-martensite energy difference ΔEM in Mn2NiGa1-xZnx increases rapidly with the doping of Zn, suggesting that the martensitic transformation temperature can be elevated with only a little Zn doping in Mn2NiGa. This can be meaningful for the development of new magnetic shape memory alloys. The variation of ΔEM can be explained by comparing the DOS structure of the austenite and martensite: The Jahn-Teller instability of Mn2NiGa1-xZnx austenitic phase is enhanced with increasing Zn content. An increase of the c/a ratio is also observed at the same time. Zn-doping does not change the magnetic structure of Mn2NiGa1-xZnx, they are always ferrimagnets within the range studied. The magnetic properties of these alloys are mainly characterized by the antiparallel coupled Mn spin moments.

The electronic structure, magnetism and martensitic transformation in Co-V based Heusler alloys Co2V1.5Z0.5 (Z = Al, Ga, In) were investigated theoretically. In these alloys, the tetragonal martensitic phase has a higher stability compared with the cubic austenite. This can be explained based on their electronic structures. Here the energy difference ΔEM between the martensite and austenite is large in Co2V1.5Al0.5 and Co2V1.5Ga0.5, suggesting that they are possible candidates for magnetic shape memory alloys (MSMAs). This also agrees with the existing experimental observation in Co-V-Ga. In Co2V1.5Z0.5 a ferromagnetic to paramagnetic transition occurs together with the martensitic transition. The spin polarization ratio also decreases drastically from close to 100% in austenite to almost zero in martensite. All this makes Co2V1.5Z0.5 alloys a cross-over point of MSMA and spintronics, which can be controlled by magnetic/temperature/stress multi-field. In Co2V1.5Ga0.5 alloy, calculations suggest a degree of Co-V disorder in the experimental sample, which may introduce a weak ferromagnetic state in the martensite and lower the phase transition driving force ΔEM. This can explain the small saturation magnetization of the martensite reported in literature. To improve the properties of Co-V-Ga alloys, adjusting their atomic ordering can be of great importance.

The electronic structure, phase stability and magnetic properties of cubic and hexagonal type Fe2MnGe were investigated and compared with the well-known Heusler alloy Fe2MnSi. Three different structures L21, DO3 and DO19 were considered for them. In both alloys the cubic phase (L21 and DO3) has a lower total energy comparing with the hexagonal DO19 phase at 0 K. But in Fe2MnGe the energy difference between the DO19 and L21 phases is much smaller than Fe2MnSi. The DO3 disorder can lower the stability of the cubic phase further and make the total energies of hexagonal and cubic phases closer, this can help the DO19 phase gain stability. Finally, in Fe2MnGe, the energy difference is 0.12 eV/f.u., much smaller than the 0.41 eV/f.u. in Fe2MnSi. That is the possible reason why Fe2MnGe DO19 phase can be synthesized experimentally and Fe2MnSi cannot. L21 type Fe2MnGe is a half-metal with 100% spin polarization and has a total spin moment of 3μB/f.u. The spin polarization ratio of DO3 phase is also high. But for the DO19 hexagonal phase, a normal ferromagnetic metal character is observed. The calculated total moment for DO19 type Fe2MnGe is larger than 6μB/f.u. This total moment comes mainly from the large and parallel coupled partial spin moments of Fe and Mn.

The stable structure of Heusler alloy Ti2NiAl and its influence on the electronic structure and magnetic properties were investigated theoretically. It is found that in Ti2NiAl, the L21 and XA structures have similar stabilities, this is related to the competition between the “number of valence electrons” and atomic size effect. L21B type structure can lower the total energy of Ti2NiAl further by 0.04eV/f.u. and has the highest stability, in which Ti and Ni atoms occupy the A, C sites randomly. The energy difference between L21/XA and L21B structures is about 0.04eV/f.u. Different atomic ordering influence the electronic structure obviously. XA type Ti2NiAl is a half-metal with an integral total moment of 3.00 μB/f.u., as has been reported in literature. But this character is destroyed in both L21 and L21B structures. In the stable L21B structure, Ti2NiAl is a normal ferromagnetic metal with a total magnetic moment of 0.84 μB/f.u.

Mn-Ni-Co-Ti alloys are newly reported all-d-metal Heusler alloys with magnetic field induced martensitic transformation and large volume discontinuity. Here we investigated the electronic structure and magnetic structural transition in Mn2Ni1.5Ti0.5 and Mn2Ni1.25Co0.25Ti0.5 theoretically. In these alloys, the same number of Mn atoms enter D (0.75, 0.75, 0.75) site when extra Ni/Co substitute for Ti. Mn (D) spin moment is parallel to that of Mn at B (0.25, 0.25, 0.25) site in cubic austenitic phase but becomes antiparallel in tetragonal martensitic phase. Then during the martensitic transition, the total magnetic moment decreases obviously. Compared with Mn2Ni1.5Ti0.5, the doping of Co in Mn2Ni1.25Co0.25Ti0.5 can enlarge the energy difference between the antiparallel and parallel configurations of Mn (B) and Mn (D) moments and thus stabilize the ferromagnetic coupling between them in austenite. DOS structure and charge density difference reveal this is related to the strong d-d hybridization between Co-Mn nearest neighbors. That is the origin of the “FM activation effect” of Co-doping in literature. The “volume-conserving assumption” may need improvement in all-d-metal Heusler alloys. The lowest total energy for Mn2Ni1.25Co0.25Ti0.5 martensitic was obtained when its cell volume is smaller than the equilibrium cell volume of the austenite. The predicted volume contraction is as large as 3.5% with a c/a ratio of 1.45. These results give reasonable explanations for existing experimental observations.

Various market factors (e.g., anti-dumping and anti-bribery, subsidy retreat, etc.) have accelerated technology upgrading and cost efficiency of PV industry. Improving conversion efficiency is an effective way to reduce cost. Mainstream silicon wafer manufacturers are intensifying research and development of "the next generation high-efficiency multicrystalline silicon wafer" that is of higher efficiency. It is essential to obtain the cell efficiency parameters at silicon wafer-side. This work analyzes the relationship between PL image parameters of multicrystalline silicon wafer measured by photoluminescence tester (PL) and the corresponding cell conversion efficiency, and the relationship between parameters of PL image and cells. Firstly, an analysis software is independently compiled to analyze the "black silk" and "normalized intensity" parameters of PL image, with the numerical results of the corresponding silicon wafers calculated. Selected high efficiency multicrystalline silicon bricks are cut into silicon wafers of 190 μm thickness, which are put to tests sequentially on the PL images of multicrystalline silicon wafers and then made into solar cells. The producing process of solar cells includes ordinary acid texturing, diffusion, removal of phosphosilicon silicon glass (PSG), plasma chemical vapor deposition (PECVD), screen printing, etc. Then cell efficiency and V oc parameters thereof are tested, with the correspondence between cell efficiency and parameters thereof and the PL parameters. The experimental data show that the tail is mainly affected by large grain boundaries and high impurity content. The correlation deviation of the cell efficiency, "normalized strength" of V oc and PL images, and "black silk" ratio parameters are greater than those of the middle section and the head. The "black silk" ratio is low, and its solar cells efficiency and V oc are high. The "normalized strength" of PL images is high, and its solar cells efficiency and V oc are high. But the "normalized strength" of PL images and V oc of cell have strong correlation with "black silk" ratio of PL images, and the "normalized strength" and "black silk" ratio of PL images have weak correlation with cell conversion efficiency. The reason is that material properties of PL photoluminescence test silicon wafer are related to the corresponding cell V oc, and cell conversion efficiency is affected by many factors: texture, diffusion, coating processes, etc. In this paper, the expression of "normalized strength" of PL and cell V oc is deduced based on the semiconductor correlation principle. It is proved that the "normalized strength" of PL is strongly correlated with that of cell V oc in principle. The "normalized strength" of PL obtained by the analysis has the closest correlation with the quality of multicrystalline silicon wafers, which can be better used to guide the quality improvement of multicrystalline silicon wafers.

A series of Mn50Ni40In10-xBx (x = 0 - 4) alloys was synthesized and the effect of B-doping on the structure, phase transition and magnetic properties in them has been investigated theoretically and experimentally. It is found that increasing boron content leads to the contraction of cell volume and increase of the martensitic transformation temperature. The doping of B also enhances antiparallel coupling between Mn spin moments in martensitic Mn50Ni40In10-xBx and lowers the Curie temperature of the austenite. Electronic structure calculations were carried out based on Mn50Ni37.5In12.5 and Mn50Ni37.5In6.25B6.25 supercells, which were close to the experimental compositions. The extra Ni atoms substituting for In/B prefer entering Mn (A) site and push Mn to the D site. In austenite ferromagnetic coupling between Mn moments on B, D sites is preferable, while in martensite the coupling between them becomes antiferromagnetic, which leads to a decrease of the total spin moment compared with the austenite. The total energy difference between the cubic austenite and tetragonal martensite increases with the substitution of boron, implying the increase of phase transition temperature. This can be explained from their DOS structures. These results agree well with experimental results and make reasonable explanation for them.

Phase stability, electronic structure and magnetic properties of the FeRu-based quaternary Heusler alloys, FeRuYZ (Y = Ti, V, Cr, Mn and Z = Al, Ga, In, Si, Ge, Sn), have been investigated theoretically. In one primitive unit cell, these alloys contain 24–26 valence electrons. The formation energy Ef of FeRuYZ increases with increasing atomic number of Z when the Y or Z elements belong to the same group in the periodic table. And in the same period, group-IIIA Z element is not preferable for the stability of FeRuYZ compared with corresponding group-IVA element. This can be explained from the charge density difference. The 24-electron FeRu-based quaternary Heusler alloys are all paramagnets. Among them, FeRuTiSi (Ge, Sn) are all semiconductors with real band gap at the Fermi levels. These alloys may have potential applications as thermoelectric materials. High spin polarization ratio is observed in the 25-electron Heusler alloys, among which FeRuCrAl is predicted to have a 100% spin polarization ratio. The 26-electron FeRuCrSi is found to be a spin gapless semiconductor (SGS) with total spin moment of 2μB. These materials can be interesting for the development of spintronic materials. The origin of SGS character in FeRuCrSi was discussed and compared with half-metallic Fe2CrSi, in which Ru and Fe are isoelectronic. These findings can help to design new SGSs in Heusler alloys.

Some studies have elucidated that Minimal residual disease (MRD) in patient with Mantle Cell Lymphoma (MCL) was a significant prognostic factor, with potential value in assessing overall survival (OS) and progression-free survival (PFS). However, most studies were widely varied in included population, sample sources and MRD detection time points. Some studies even have conflicting results. In view of this, a meta-analysis was performed to evaluate association of MRD levels with clinical outcomes in patients with MCL. We identified 7 included articles, which were published in recent 20 years. Then, we extracted or calculated hazard ratios (HRs) and their 95 % confidence intervals (CIs). Our results reveal that patients with MRD negativity have improved OS (HR = 0.63; 95 % CI: 0.50−0.79) and PFS (HR = 0.40, 95 % CI: 0.21−0.76), comparing with patients with MRD positivity. There are also consistent results in subgroups based on sample sources and MRD detection time points. Our study also demonstrates that MRD level is a strong prognostic factor of clinical outcomes. Thus, MRD is expected to be an effective clinical indicator for assessing prognosis and guide treatment decisions in MCL patients.

The effects of Bi-doping on the electronic structure, martensitic transformation and magnetic properties of Heusler alloys Ni2MnGa1-xBix and Mn2NiGa1-xBix (x=0, 0.25, 0.5, 0.75, 1) were investigated theoretically. The substitution of Bi for Ga has a negative effect on the martensitic transformation. The total energy difference ΔEM between the martensite and austenite decreases gradually with the doping of Bi. When x=0.5, 0.75 and 1.0 in Ni2MnGa1-xBix and x=1.0 in Mn2NiGa1-xBix, the martensite phase becomes higher in energy comparing with the austenite. Thus the doping of Bi can lower the martensitic transformation temperature TM and finally suppresses it. The possible reasons for this trend are related to the increasing valence electron concentration e/a and cell volume V with Bi-doping. The competition between them may be ascribed further by the electron density, which combines the effect of valence electron concentration and size effect. The electron densities of Ni2MnGa1-xBix and Mn2NiGa1-xBix decrease monotonously with increasing Bi content. This agrees well with the variation of ΔEM or TM. The doping of Bi does not change the magnetic structure of Ni2MnGa1-xBix and Mn2NiGa1-xBix. The former is ferromagnetic and the latter is ferrimagnetic in both martensite and austenite state. These results can help to introduce new component like Bi to Heusler alloys and discover new functional materials in them.

In order to further improve the quality of high efficiency multicrystalline silicon and the performance of multicrystalline silicon solar cells, we designed a compact nucleation layer on the crucible bottom for casting high performance multicrystalline silicon ingots. The morphology of nucleation grains, the minority carrier lifetime mappings and the defects were analyzed and compared with that of the conventional nucleation layer. The results show that the initial nucleation grains of the compact nucleation layer were finer and more uniform, and there are fewer grains with high defect density at the ingot bottom，which is beneficial to reduce the defect ratio of the whole ingot. Moreover, the solar cell efficiency and electrical performance parameters, such as Rsh was also discussed. It was found that the Rsh has a great impact on the efficiency of multi-busbars solar cells, and the average solar cell conversion efficiency of the wafers grown with the compact nucleation layer is 0.11% higher than that of the wafers grown with the conventional nucleation layer.

Transition metal Zn shows a main group element-like behavior in Heusler alloys Ni2MnGa1−xZnx (x = 0, 0.25, 0.50, 075 and 1.00). Zn enters Ga (D) site when it substitutes for Ga in Ni2MnGa chemically. The equilibrium lattice constant decreases with increasing Zn content. But at the same time the magnetic properties do not change too much. Mn partial moment contributes most to the total moment and couples parallel to that of Ni in both austenite and martensite. The partly substitution of Zn for Ga can lead to an increase of martensitic transition temperature due to the competition between cell volume effect and valence electron concentration e/a. Accordingly, the largest energy difference ΔEM between the austenite and martensite was found when x = 0.5. This was further explained based on the electronic structure from the Jahn-Teller effect. Then Zn-doping can be used as a possible way to adjust the phase transition temperatures in Heusler type MSMAs. Zn is much cheaper than Ga or In, this can be quite meaningful for the development of high performance and low cost MSMAs and broaden their industrial applications.

Influence of Fe substitution for Ni on the magnetic properties and martensitic transformation was investigated theoretically in Heusler alloys Ni2Mn1.5Z0.5 (Z = In, Sb). Fe-doping does not change the general magnetic structure of Ni2Mn1.5Z0.5. In both Ni2Mn15In0.5 and Ni1.75Fe0.25Mn1.5In0.5 the austenitic phase is ferromagnetic and martensitic phase is antiferromagnetic, which leads to the large ΔM observed experimentally. But in Ni2Mn1.5Sb0.5 and Ni1.75Fe0.25Mn1.5Sb0.5, the antiferromagnetic state is stable in both austenite and martensite. This difference is mainly related to the different atomic radii of In and Sb, which change the distance between Mn (B) and Mn (D). Parallel or antiparallel coupled Mn moments determine the magnetic properties of these alloys. But the partial moment of Fe is large and its direction reverses after martensitic transformation, which makes it a possible way to adjust the magnetic properties of MSMAs. Calculation also suggests that the substitution of Fe for Ni can lower the martensitic transition driving force and lead to the decrease of phase transition temperature. These results agree well with preceding experimental results and make reasonable explanation for them.

We have utilized cheaper ambient nitrogen for casting multicrystalline silicon ingots. Ambient nitrogen serves as the N doping source, it causes Si3N4 inclusions and related cracks when the doping amount is too high, while N doping can be effectively controlled by tuning the pressure of ambient nitrogen. The maximum value of the N concentration is measured up to 9.4 × 1015/cm3 by SIMS. The increase of nitrogen concentrations can reduce wafer breakage rate by significantly improving the fracture strength of wafers. The influence of N-O complexes in N-doped MC-Si on electric properties is also discussed. Solar cell efficiencies of N-doped wafers are almost comparable to those from ingots grown under ambient argon.

Mn2NiGa1-xCrx (x = 0–0.5) alloys were synthesized successfully to explore possible Cr-based all-d-metal Heusler alloys with magnetic shape memory effects. When x = 0–0.25, Mn2NiGa1-xCrx are single BCC Heusler phase, but when x = 0.375 some FCC phase co-exists with the main Heusler phase, finally a pure FCC phase is formed in Mn2NiGa0.5Cr0.5. In BCC Mn2NiGa1-xCrx, Cr-doping leads to the decrease of martensitic transformation temperature TM and increase of the saturation magnetization Ms at 5 K. While the FCC phase does not show the trace of phase transition and has a very low magnetization till 5 K. First-principles calculations suggest that, in BCC Mn2NiGa1-xCrx the partial spin moment of Cr is large and parallel to that of Mn (B), which leads to the increase of Ms when x = 0–0.25. A higher stability of the martensite than the austenite is found, which supports the phase transition observed experimentally. It may be noticed that the TM of Mn2NiGa1-xCrx decreases with both increasing e/a and decreasing cell volume, which is opposite to the empirical rule in traditional Heusler alloys. Calculation suggests that Cr–Ga disorder may be a possible reason for this decrease.

The casting method is a low-cost technique to fabricate photovoltaic monocrystalline silicon wafers. The development of cast monocrystalline silicon (CM-Si) materials requires high quality and low cost. To further reduce CM-Si's cost, a large-scale recycled seed has become a focused topic. This work compared new seeds and a large-scale recycled seed in the same growth so that the experimental errors in the growth environment were eliminated. Detailed characterizations on defect distribution and performances have shown that seed recycling will generate extra initial defects. However, it becomes influential for solar cell performance only when defect concentration reaches a certain level. Finally, a related defect propagation mechanism was revealed for manufacturers to optimize industrial growth strategies.

BCC Heusler phase Ni2CoSi has been predicted to be a promising candidate to realize magnetic field induced martensitic transformation. We tried to prepare Ni2CoSi single phase using different methods. Single phase Ni2CoSi cannot be synthesized by arc-melting and annealing. Then we used mechanical alloying method to synthesize Ni2CoSi. But a FCC phase rather than BCC was obtained after ball-milling. The lattice constant of FCC Ni2CoSi is 3.52 A and the Curie temperature is around 900 K. The saturation magnetization at 5 K is 2.44μB/f.u. This FCC phase is stable and no transition is observed when heating to 1173 K. The electronic structure and phase stability of the FCC and BCC Heusler phase have been investigated by first-principles calculations. The FCC Ni2CoSi has lower total energy compared with BCC, agreeing with the experimental observation. But the calculated total moment is much smaller than the Ms at 5 K. This difference is related to the atomic disorder and was discussed by KKR-CPA calculation.

Heusler alloy Co 2 RuSi has been synthesized by melt-spinning technology successfully. Co 2 RuSi bulk sample after annealing is composed of an HCP Co-rich phase and a BCC Ru-Si phase, but melt-spinning can suppress the precipitation of the HCP phase and produce a single Co 2 RuSi Heusler phase. In the XRD pattern, it is found that Ru has a strong preference for the (A, C) sites, though it has fewer valence electrons compared with Co. This site preference is different from the case in Heusler alloys containing only 3d elements and is supported further by first-principles calculations. Melt-spun Co 2 RuSi has a M s of 2.67 μ B /f.u. at 5 K and a Tc of 491 K. An exothermic peak is observed at 871 K in the DTA curve, corresponding to the decomposition of the Heusler phase. Finally, the site preference and magnetic properties of Co 2 RuSi were discussed based on electronic structure calculation and charge density difference.

A series of quaternary Heusler alloys NiCuMnZ (Z = In, Sn, Sb) have been prepared experimentally. Their structural and magnetic properties have been investigated by XRD, magnetic measurements and first-principles calculations. NiCuMnZ all crystallize in a cubic Heusler structure. But the atomic ordering in them is different and related to the main group element Z. NiCuMnSb is highly ordered while NiCuMnIn and NiCuMnSn have a degree of Cu-Mn disorder in the lattice. In these alloys, Cu atom has strong preference for the B (0.25, 0.25, 0.25) site, though Cu has more valence electrons than Mn and Ni. The saturation magnetization M s at 5 K is 3.99μ B /f.u., 4.20μ B /f.u. and 4.02μ B /f.u. for NiCuMnSb, NiCuMnSn and NiCuMnIn, respectively. First-principles calculations suggest that the large total moments mainly come from the contribution of Mn. The T C decreases rapidly from 716 K in NiCuMnSb to 340 K in NiCuMnIn, relating to the increasing degree of atomic disorder in their lattice. But the partial moments of Mn are always in ferromagnetic coupling though they are nearest neighbors in partly disordered NiCuMnSn and NiCuMnIn.

The damping capacity of Ni55−xCuxMn25Ga20 (x = 0, 2, 4, 6) shape memory alloys is studied in details. The results show an increasing damping peak capacity with increasing Cu content. Especially, a high damping peak with the peak value of 0.08 is found in Ni49Cu6Mn25Ga20 alloy, which spans over a wide temperature range of 173 K–425 K. The first-principles calculations indicate the substitution of Cu for Ni weakens the p-d orbital hybridization of Ni55−xCuxMn25Ga20 and reduces its martensite modulus, which thus enhances its twin boundary mobility and the damping capability. Our study sheds light on developing ambient-temperature high damping alloys.

The site preference of 4d transition metal element Zr in Heusler alloys Zr2YAl (Y = Cr, Mn, Fe, Co, Ni) has been investigated theoretically. In these alloys the two Zr atoms prefer entering the A (0, 0, 0) and C (0.5, 0.5, 0.5) sites in the lattice of Heusler alloys and forming L21 structure (Cu2MnAl-type). This is different from previous predictions based on “number of valence electrons”, in which Zr atoms were predicted to occupy A (0, 0, 0) and B (0.25, 0.25, 0.25) sites and form XA (Hg2CuTi-type) structure. Present work suggests that L21 structure has a much lower total energy compared with XA type. Half-metallicity and spin gapless semiconductor character have been predicted in XA type Zr2YAl, but these properties may be disturbed under the more stable L21 structure. The energy difference between the XA and L21 structures increases as Y atom varies from Cr to Ni. The reason has been discussed based on the charge density difference. The magnetic properties of Zr2YAl have been investigated, a new possible Slater-Pauling curve of M = Z−22 has been observed in Zr2CoAl and Zr2NiAl.

Competition between the highly-ordered XA structure and disordered L2 1 B structure in Heusler alloys Mn 2 CoZ (Z = Al, Ga, Si, Ge, Sb) has been investigated. The relative stability of the two structures strongly depends on the main group element Z. When Z belongs to Al or Ga, the XA structure is stabler, but when Z belongs to Si, Ge or Sb, the L2 1 B structure gains stability and is lower in energy. This is related to the different number of valence electrons in main group element Z, which influences the DOS structure near the Fermi level and changes N(E F ). The energy difference ΔE between the XA and L2 1 B structures may be used to estimate the tendency to form L2 1 B structure in different Heusler alloys qualitatively. A large negative ΔE is preferable to retard the A-C site disorder and retain the highly-ordered XA structure. That is just the case in Mn 2 CoAl. A robust half-metallicity is observed in Mn 2 CoSi, Mn 2 CoGe and Mn 2 CoSb, they are always half-metallic under either XA or L2 1 B structure. But in Mn 2 CoAl and Mn 2 CoGa, their spin gapless semiconducting character will be destroyed and replaced by a half-metallic state if L2 1 B disorder occurs. Finally, these results suggest that the L2 1 B structure should be considered together with XA structure when discussing the electronic structure of “inverse” Heusler alloys.

Fe 2 NiSi FCC phase has been prepared by ball-milling successfully, which is different from the BCC Heusler phase prepared by arc-melting in previous literatures. The FCC Fe 2 NiSi is a ferromagnet with a lattice constant of 3.58 A. The phase stability of the FCC and BCC Fe 2 NiSi has been compared by first-principles calculations. It has been found that the FCC structure has a lower total energy compared with the highly-ordered Heusler structures XA and L2 1 , that is the reason why the FCC phase can be prepared by ball-milling. However, the Fe (A)–Ni (C) disorder in the BCC XA structure can lower its total energy further and make it smaller than the FCC phase. So the most stable structure in Fe 2 NiSi is L2 1 B, as has been observed in the arc-melting sample. This can be explained from their DOS structures. The calculated total moments for the FCC and BCC phases agree with their M s at 5 K quite well.

This paper focused on studying an octagonal thermal field to improve the quality of multi-crystalline silicon ingot. A global numerical model was adopted to investigate the effects of the modified furnace on the temperature distribution and temperature gradients distribution during the directional solidification process. The numerical results indicated that a more uniform temperature distribution and lower temperature gradients were obtained in the modified furnace. Meanwhile, the experimental ingot was obtained by using the modified furnace. Experimental tests of minority carrier lifetime distribution, dislocation clusters, and the average conversion efficiency for the conventional ingot and the modified octagonal ingot were carried out. The results indicated that the modified octagonal silicon ingot could achieve lower defect density, especially near the crucible wall. Therefore, the average conversion efficiency of the modified octagonal ingot was improved by 0.12% compared with the conventional ingot. Furthermore, the mechanism and control of ingot side dislocation multiplication were discussed.

Biodiesel soot particles (BSPs) and first heat-treated and then acid-treated BSPs (T-BSPs) were employed as lubricant additives for GCr15 steel/316 austenitic stainless steel contacts in aqueous media. Their tribological performances and mechanisms were tested. The result shows that T-BSPs exhibited better lubricating performances than BSPs in aqueous media. Moreover, it is proved that both BSPs and T-BSPs could enter the friction surfaces and prevent the direct steel–steel contact. In addition, T-BSPs exhibited better dispersion in water, which aided uniform adsorption on the friction surfaces, resulting in better friction-reducing and antiwear performances.

C-doped Fe2MnGaCx (x = 0, 0.05, 0.1 and 0.2) alloys have been synthesized and the influence of carbon on the structure and magnetic properties of Fe2MnGa has been investigated. The doping of C can expand the lattice of Fe2MnGa, suggesting that it enters the interstitial site of FCC lattice. The ferromagnetic coupling in Fe2MnGaCx can be strongly enhanced with increasing C content. The ferromagnetic to antiferromagnetic transition in undoped Fe2MnGa is suppressed by C-doping and disappears when x = 0.1 and 0.2. The saturation magnetization Ms and Curie temperature TC also increase with C-doping. Large coercivity and exchange bias can be observed in the magnetic hysteresis loops of Fe2MnGa, due to the coexistence of FM and AFM states. But in Fe2MnGaC0.2, both of them disappear and a pure ferromagnetic character is observed. All this suggests that C-doping can be a possible way to adjust the magnetic properties of Fe2MnGa and other related alloys.

A series of Fe2MnSi1−xBx (x = 0–0.4) Heusler alloys was synthesized and investigated. The variation of lattice parameters with B content suggests that B prefers entering the substitutional site of Fe2MnSi when the amount is small. But when B content is high, it enters the interstitial site. A spin reorientation is observed at ~54 K in Fe2MnSi, which moves to low temperatures with increasing B content and disappears when x = 0.3. Both the Curie temperature TC and saturation magnetization Ms increase with the substitution of B for Si. The Ms gets closer to the calculated total spin moment Mt. All this suggests that the dope of B can enhance the ferromagnetic character of Fe2MnSi1−xBx. For the high B content, B-doping expands the lattice and enlarges the distance between magnetic atoms. This leads to the increase of Fe and Mn spin moments. The substitution of B for Si has an ordering-effect for Fe2MnSi lattice by forming a strong covalent bonding and relieves the possible Fe-Mn disorder. This effect also contributes to the increase of Ms.

The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe–Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe–Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

A competition between the conventional L21 ordering and inverse XA ordering has been observed in Heusler alloys X2CuAl (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni). In X2CuAl, the site preference of Cu is strongly influenced by the crystal structure of pure X elements. When X element has a close-packed FCC or HCP structure (Sc, Ti, Co and Ni), Cu prefers entering the ( 1 4 , 1 4 , 1 4 ) position and forms the L21 structure, but when X has a BCC structure (V, Cr, Mn, Fe), Cu prefers entering the ( 1 2 , 1 2 , 1 2 ) position and forms the XA structure. So the crystal structure of pure X element should also be considered together with number of valence electrons when discussing the site preference in Heusler alloys. Mn2CuAl is found to be a spin gapless semiconductor (SGS) with fully-compensated total moment. Based on this, a possible rule to design SGS has been discussed. Finally, X2CuAl alloys all have a negative formation energy except for V2CuAl and Cr2CuAl.

The martensitic transformation and electronic structure of Heusler alloys Mn2YIn (Y=Ni, Pd, Pt) have been investigated by both first-principles calculation and experimental investigation. Theoretical calculation reveals that, the energy difference ΔE between the tetragonal martensitic phase and cubic austenitic phase increases with Y varying from Ni to Pt in Mn2YIn. Thus a structural transition from cubic to tetragonal is most likely to happen in Heusler alloy Mn2PtIn. A single Heusler phase can be obtained in both Mn2PtIn and Mn2PdIn. A martensitic transformation temperature of 615 K has been identified in Mn2PtIn. And in Mn2PdIn, the austenitic phase is stable and no martensitic transformation is observed till 5 K. This indicates there may exist a positive relation between ΔE and martensitic transformation temperature. Calculated results show that Mn2YIn are all ferrimagnets in both austenitic and martensitic phases. The magnetic properties are mainly determined by the antiparallel aligned Mn spin moments. These findings can help to develop new FSMAs with novel properties.