【正文】 structure of ncNi is knownthat smaller grain size can be obtained by the addition ofsuitable grain refining agents like saccharine or sodium ,in different amounts，in the case of Ni electrodeposition But few studies had been undertaken to developand evaluate the influence of refining agents on theproperties of nanocrystalline Ni coatings systemically Therefore，the purpose of this paper is to study the effectof saccharine sodiumamountson the microstructure，microhardness，thermal stabilityand corrosion resistance of ncNi coatings.1 Experimental procedureThencNi coatings were prepared by pulseelectrodeposition in a plating bath with aqueous bath6H2O 300g / L，NiCl26H2O 45g / L，H3BO340g / L，C12H25OSO2Na0. 05 g / used reagents of the solutions were analytically experiments were performed at 50 ℃with a current density of 10 A / cycle of 20%and pulse frequency of 800 Hz The pH values of thesolutions were kept at 3.0 by adding the dilute solutionof plate（99%）was used as anodeThecopper was cathode with dimension of 50 mm 40 mm 0.2 the electrodeposition，the coppersubstrate was sanded and washed byalkaline，acid and distilled water in turn.After theprocedure，the treated copper substrate was put into the other parameters were fixed，theconcentrations of saccharin sodium were 0，5，10，15，20，25 g / L， the experiments，allthe electrodeposition time was 15 surface morphology and grain size of ncNicoating were investigated by a JSM6360Lv scanningelectron microscope ( SEM ) and a JEM2000EXtransmission electron microscope(TEM) at acceleratingvoltage of 200 crystal structure of ncNicoatings was obtained on a D8 Xray diffractometer(XRD) with a Cu Kα size of thedeposits was calculated by the(111) Xray diffractionpeak broadening and was estimated by applying theScherrer equation.L = kλ / βcosθwhere β is the full width half maxima(FWHM)，θ thediffraction angle，L the grain size，k ( = 0.89) is thecamera constant and λ( = 0.15406 nm ) is thewavelength of the radiation used.Microhardness of the coatings was determined by aFM700 Vicker’s microhardness indenter with a load of100gf and loading time is 15 test method wasreferred to national standard GB / T 4340. coating thermal stability was estimated by a DSC200F3 differential scanning calorimeter ( DSC) in a nitrogen atmosphere with a 20 ℃ min1 heating anodic potentiodynamic polarization curve of ncNicoatings was measured by a PS168B electrochemicalworkstation in 3.5 wt% NaCl solution.2 Results and discussion Microstructure of ncNi coating XRD patterns of ncNi coatings deposited atdifferent contents of saccharin sodium are shown in Fig.As evidence in Fig. 1，the (111) peaks of depositsare apparently widened and then sharpened with theincrease of the saccharin sodium meansthat the grain sizes of ncNi coatings decreased firstlyand then addition，all the ncNi coatingsexhibit face centered cubic（fcc） lattice with（111）growth order to describe the structure and preferred orientation of the deposits in detail，the texture coefficient (TC)is used，which is defined as:TC =［Ihkl/ Ihkl］/［(1 / n)∑(Ihkl/ Ihkl)］where Ihkl and I176。hkl are the diffraction intensity of thecrystal plane(hkl)in the deposit and standard sample，respectively. n is the number of reflection faces in thediffraction the texture coefficient is greaterthan 1.0，it indicates the existence of a preferredorientation. Table 1 Mean grain sizes and TC of ncNi coatings atvarious saccharin sodium concentrationsFig. 1 XRD patterns of ncNi coating coatings depositedat different saccharin sodium concentrationsAccording to XRD patterns，the grain sizes and TCvalues of the deposits were calculated by applying Eq.(1) and (2).The results are provided in Table 1.It isclear that the mean grain size of ncNi coatingsdecreased with the increase of the concentration till 10g / the grain size increased when theconcentration is greater than 10 g / sodiumis adsorbed on the surface，the mean free path for lateraldiffusion of ions is shortened，which is equivalent to adecrease in the coefficient of diffusion of decrease in the coefficient of diffusion results in increasein ions at the steady state and thus an increase in thetwodimensional nucleation rate。As a consequence，twodimensional growth rates are reduced， leading tofine grain when the concentration is greaterthan 10 g / L，excessive saccharin sodium would makethe overpotential of cathode ， thedriving force of nucleation is weakened and nucleationrate decreases.As a result，the grain size 1 also shows the relationship between thesaccharin sodium concentration in electrolyte and thetexture coefficients of ncNi a saccharinsodium concentration up to 10 g / L，the TC values forthe(111)orientations are greater than 1.0，preferredorientation of ncNi electrodeposits is the dual ( 111 )fiber ，as the concentration increases，the dual(111)fiber texture decreases，and a(220)fiber texture，which is negligible at low saccharinconcentrations，starts to develop.Fig. 2 Surface morphology of ncNi coatings deposited at differentconcentrations of saccharin sodiumFig. 2 shows the change in the surface morphologyof the electrodeposited ncNi with concentration ofsaccharin sodium in our system，the coatingis anomalistic cell deposit with some defects withoutsaccharin sodium in solution due to the very highinternal stresses generated during electrodeposition，which could be eliminated in the presence of saccharinsodium in solution with a saccharinsodium concentration less than 15 g / L， theelectrodeposited foil has a shiny and smooth surface，thecircu