Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>Hydrothermal method was directly applied in the preparation of calcium sulfate whiskers with phosphogypsum as raw material</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: " mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: Roman?; New Times AR-SA? ?Times mso-bidi-font-family: mso-hansi-font-family:>，</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>which providing a theoretical basis for the industrialization of calcium sulfate whiskers production from phosphogypsum.Effects of reaction temperature,initial pH of slurry, reaction time,concentration of slurry,and size of phosphogypsum on calcium sulfate whisker products were investigated.Morphology of the prepared whiskers were observed by SEM.Diameters and lengths of calcium sulfate whiskers prepared under different reaction conditions were determined by PEM and image analysis software.Results showed the optimum conditions of preparation were as follows</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: " mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: Roman?; New Times AR-SA? ?Times mso-bidi-font-family: mso-hansi-font-family:>：</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>reaction temperature was at 130~<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="140" UnitName="℃">140 <SPAN lang=EN-US style="FONT-FAMILY: 宋体; mso-ascii-font-family: " Roman?; New Times ?Times mso-hansi-font-family: Roman??><SPAN lang=EN-US>℃</SPAN></SPAN></st1:chmetcnv>,initial pH was 4.0,reaction time was 4 h,concentration (mass fraction) of slurry was 5%,and raw material size was at 50</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: " mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: Roman?; New Times AR-SA? ?Times mso-bidi-font-family: mso-hansi-font-family:>～</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>75 </SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: " mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: Roman?; New Times AR-SA? ?Times mso-bidi-font-family: mso-hansi-font-family:>μ</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>m.Under those conditions CaSO</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times><SUB>4</SUB><SPAN style="mso-spacerun: yes">&nbsp; </SPAN>whisker products with diameter of 2 </SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: " mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: Roman?; New Times AR-SA? ?Times mso-bidi-font-family: mso-hansi-font-family:>μ</SPAN><SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: " 宋体? mso-fareast-font-family: AR-SA; mso-bidi-language: ZH-CN; mso-fareast-language: EN-US; mso-ansi-language: 1.0pt; mso-font-kerning: 12.0pt; mso-bidi-font-size: Roman?; New Times>m and slenderness ratio of 42 could be obtained.</SPAN>