The　Ni/Al　nitrate　form　layered　double　hydroxides　(LDHs)　were　successfully　synthesized　at　atmosphere　condition　by　chemical　precipitation　and　hydrothermal　methods　through　pH　control.　Samples　obtained　at　various　pH　conditions　were　characterized　by　XRD,　FT-IR,　TG-MS,　ICP/AES　and　CHN　element　analyses.　It　was　found　that　at　low　pH　value,　nitrate　hydrotalcite　was　obtained,　while　at　high　pH　value,　carbonate　hydrotalcite　was　produced.　Ni/Al　nitrate　form　LDHs　particles　with　good　crystallinity　were　obtained　by　hydrothermal　treatment.　SEM　and　TEM　images　show　that　the　particle　processes　classical　hexagonal　shape.　The　transformation　mechanism　of　the　Ni/Al　LDHs　between　nitrate　and　carbonate　form　under　pH　control　was　also　discussed.　This　study　offers　a　simple　method　to　produce　Ni/Al　nitrate　form　LDHs　with　good　crystallinity　without　controlled　environment　to　exclude　CO2　just　by　controlling　the　pH　value.　(C)　2010　Elsevier　B.V.　All　rights　reserved.