Use of Digestate as Organic Amendment and Source of Nitrogen to Vegetable Crops

Anaerobic digestion is a valuable process to use livestock effluents to produce green energy and a by-product called digestate with fertilising value. This work aimed at evaluating the fertilising value of the solid fraction (SF) of a digestate as an organic amendment and as a source of nitrogen to crops replacing mineral N. A field experiment was done with two consecutive vegetable crops. The treatments were: a control without fertilisation; Ni85 mineral fertilisation with 85 kg ha−1 of mineral N; fertiliser with digestate at an increasing nitrogen application rate (kg N ha−1): DG-N85 DG-N170, DG-N170+85, DG-N170+170; fertilisation with digestate together with Ni: DG-N85+Ni60, DG-N170+Ni60, DG-N170+Ni25. The results showed a soil organic amendment effect of the SF with a beneficial effect on SOM, soil pH and exchangeable bases. The SF was able to replace part of the mineral N fertilisation. The low mineralisation of the stable organic matter together with some immobilisation of mineral N from SF caused low N availability. The fertilisation planning should consider the SF ratio between the organic N (NO) and total N (TKN). Low NO:TKN ratios (≈0.65) needed lower Ni addition to maintaining the biomass production similar to the mineral fertilisation.

Effect of Ni Addition on the Corrosion Resistance of NiTi Alloy Coatings on AISI 316L Substrate Prepared by Laser Cladding

In this paper, an equiatomic NiTi (55NiTi) alloy powder was mixed with pure Ni powder to prepare laser cladding coatings on a 316L stainless steel substrate to study the effect of Ni addition on the microstructure and corrosion resistance of the coatings. The microstructure and phase composition of the coatings were analyzed using a scanning electron microscope (SEM) with configured energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD). OCP (open-circuit potential), PD (potentiodynamic polarization) and EIS (electrochemical impedance spectroscopy) experiments were conducted by a Gamry electrochemical workstation, and corresponding eroded morphologies were observed to evaluate the coating’s anti-corrosion performance. The addition of Ni led to fine and uniform dendrites and dense microstructure under the metallurgical microscope, which were beneficial for the formation of the passive film mainly consisting of titanium dioxide (TiO2). The results show that the pitting potential of the 55NiTi + 5Ni coating was 0.11 V nobler than that of the 55NiTi coating, and the corrosion current density was less than half that of the 55NiTi coating. The corrosion initiated preferentially at the interfaces of dendrites and inter-dendritic areas, then spread first to dendrites rather than in the inter-dendritic areas.

Study on the Effect of Ni Addition on the Microstructure and Properties of NiTi Alloy Coating on AISI 316 L Prepared by Laser Cladding

This paper investigated 55 NiTi commercial alloy powder and 55 NiTi with 5% pure Ni mixed powder (55 NiTi + 5 Ni) coatings fabricated by laser cladding to study the effect of extra Ni addition on the microstructure and properties of the coating. The XRD and EDS results show that the major phases in the coatings were NiTi and Ni3Ti. Besides that, a second phase like Ni4Ti3, Fe2Ti, and NiTi2 was also detected, among which, NiTi2 was only found in 55 NiTi coating. The proportion of the phase composition in the coating was calculated via the software Image-Pro Plus. The hardness of the cladding layer reaches 770–830 HV, which was almost four times harder than the substrate, and the hardness of 55 NiTi + 5 Ni coating was around 8% higher than that of 55 NiTi coating. The wear resistance of the 55 NiTi + 5 Ni coating was also better; the wear mass loss decreased by about 13% and with a smaller friction coefficient compared with the 55 NiTi coating. These results are attributed to the solid solution strengthening effect caused by Ni addition and the second phase strengthening effect caused by the content increase of the Ni3Ti phase in the cladding layer.

Effect of Small Amount of Ni Addition on Microstructure and Fatigue Properties of Sn-Sb-Ag Lead-Free Solder

The effect of the addition volume of Ni on the microstructures and tensile and fatigue properties of Sn-6.4Sb-3.9Ag (mass%) was investigated using micro-size specimens. The addition of Ni into Sn-6.4Sb-3.9Ag tends to increase the number of grains formed in the solidification process and produce a high-angle grain boundary. An amount of 0.1% proof stress of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at a strain rate of 2.0 × 10−1 s−1. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on tensile strength is negligible at both 25 °C and 175 °C. The elongation of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at 25 °C according to the fracture mode change from ductile chisel point fracture to shear fracture. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on the elongation is negligible at 175 °C. The low cycle fatigue test result shows that the fatigue life does not degrade even at 175 °C in all alloys investigated. The fatigue life of Sn-6.4Sb-3.9Ag-0.4Ni (mass%) is superior to those of Sn-6.4Sb-3.9Ag and Sn-6.4Sb-3.9Ag-0.03Ni (mass%) in the high cycle fatigue area. The electron back scattering diffraction (EBSD) analysis result shows that fine recrystallized grains are generated at the cracked area in Sn-6.4Sb-3.9Ag-0.4Ni in the fatigue test at 175 °C, and the crack progresses in a complex manner at the grain boundaries.

Influence of Ni on Fe and Co-Fe Based Catalysts for High-Calorific Synthetic Natural Gas

Fe-Ni and Co-Fe-Ni catalysts were prepared by the wet impregnation method for the production of high-calorific synthetic natural gas. The influence of Ni addition to Fe and Co-Fe catalyst structure and catalytic performance was investigated. The results show that the increasing of Ni amount in Fe-Ni and Co-Fe-Ni catalysts increased the formation of Ni-Fe alloy. In addition, the addition of nickel to the Fe and Co-Fe catalysts could promote the dispersion of metal and decrease the reduction temperature. Consequently, the Fe-Ni and Co-Fe-Ni catalysts exhibited higher CO conversion compared to Fe and Co-Fe catalysts. A higher Ni amount in the catalysts could increase C1–C4 hydrocarbon production and reduce the byproducts (C5+ and CO2). Among the catalysts, the 5Co-15Fe-5Ni/γ-Al2O3 catalyst affords a high light hydrocarbon yield (51.7% CH4 and 21.8% C2–C4) with a low byproduct yield (14.1% C5+ and 12.1% CO2).

Hydrogen Transportation Behaviour of V–Ni Solid Solution: A First-Principles Investigation

Hydrogen embrittlement causes deterioration of materials used in metal–hydrogen systems. Alloying is a good option for overcoming this issue. In the present work, first-principles calculations were performed to systematically study the effects of adding Ni on the stability, dissolution, trapping, and diffusion behaviour of interstitial/vacancy H atoms of pure V. The results of lattice dynamics and solution energy analyses showed that the V–Ni solid solutions are dynamically and thermodynamically stable, and adding Ni to pure V can reduce the structural stability of various VHx phases and enhance their resistance to H embrittlement. H atoms preferentially occupy the characteristic tetrahedral interstitial site (TIS) and the octahedral interstitial site (OIS), which are composed by different metal atoms, and rapidly diffuse along both the energetically favourable TIS → TIS and OIS → OIS paths. The trapping energy of monovacancy H atoms revealed that Ni addition could help minimise the H trapping ability of the vacancies and suppress the retention of H in V. Monovacancy defects block the diffusion of H atoms more than the interstitials, as determined from the calculated H-diffusion barrier energy data, whereas Ni doping contributes negligibly toward improving the H-diffusion coefficient.