A NANO COMPOSITE GLASS CONTAINING NANO CRYSTALLINE KTIOPO4 (KTP), WERE SYNTHESIZED BY Sol-gel PROCESSES. AFTER HEAT TREATMENT AT TEMPERATURES HIGHER THAN 750OC, THE K2O-TIO2-P2O5-SIO2 gel MONOLITHS TRANSFORMED INTO KTP NANO CRYSTALS EMBEDDED IN SIO2–BASED GLASS. A POSSIBLE WAY FOR DEVELOPING NONLINEAR OPTICAL MEDIA BASED ON GLASS IS INTRODUCING NONLINEAR OPTICAL CRYSTALS SUCH AS KTP INTO A GLASS MATRIX AND PRODUCING A COMPOSITE...

Sol gel METHOD CAN BE USED TO SYNTHESIZE PURE SILICA AND ORGANICALLY MODIFIED SILICATES BY PARTIALLY REPLACING TETRAETHYL ORTHOSILICATE (TEOS) WITH POLYDIMETHYLSILOXANE (PDMS). IN THIS STUDY SILICA AND SILICA/POLYDIMETHYLSILOXANE XEROgelS WERE PREPARED BY Sol gel TWO STEP PROCEDURE (HYDROLYSIS REACTION UNDER ACID CONDITION AND CONDENSATION REACTION UNDER BASE CONDITION). AFTER CONDENSATION THEY WERE LEFT TO DRY. USING TETRAETHYL ORTHOSILICATE AS A PRECURSOR OF SILICA MATRIX, POLYDIMETHYLSILOXANE AS ADDITIVE, HCL (0.01M) AND NH4OH (1M) AS CATALYIST, XEROgelS WITH DIFFERENT PROPERTIES OBTAINED.FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR) WAS USED TOANALYSIS MATRIX. gelATION TIME FOR TEOS AFTER ADDING AMMONIA IS 1MIN AND FOR TEOS-PDMS IS ABOUT 6 MIN. THE FTIR SPECTRA OF PREPARED XEROgelS ARE SHOWN IN FIG1.A AND 1.B. SIGNIFICANT DIFFERENCES EXIST FOR INTENSITY OF BANDSFOR SAMPELS WITH PDMS AND WITHOUT PDMS. ADDITIONAL PEAKS AT 2963 (1/CM) AND 1262 (1/CM) IN FIG1.A ARE RESPECTLY DUE TO THE FUNDAMENTAL STRETCHING VIBRATION OF C-H BONDS ANDBENDING VIBRATIONS OF SI-CH3 BONDS BELONGING TO PDMS. INTENSITY OF THE BOND RESPONSIBLE FOR OSCILLATIONS IN THE O-H GROUP (3000-3500 (1/CM)) IS LOWER FOR TEOS-PDMS BECAUSE OF HYDROPHOBIC NATURE OF PDMS THAT REDUCES THE O-H GROUPS AND WATER MOLECULES INSIDE XEROgel. ALSO THE BOND LOCATED AT 870 (1/CM) CORRESPONDS TO THE CO-POLYMERIZATION BETWEEN PDMS AND HYDROLYSED TEOS MOLECULES DEMONSTRATING THE FORMATON OF HYBRID MATERIAL.

BACKGROUND: ACCORDING TO RECENT TECHNICAL REPORTS, VARIOUS CHEMICAL METHODS HAVE BEEN DEVELOPED TO CONTROL THE PARTICLE SHAPES, SIZE, AND DISTRIBUTION OF FINE SILICA POWDER. [1]. Sol-gel METHODS IS WELL KNOWN AND AN IMPORTANT ROUTE TO PRODUCE SILICA SUPPORTED CATALYSTS [2]. preparation OF MESOPOROUS SILICA VIA THE NEUTRAL ROUTE HAS IMPORTANT ADVANTAGES OVER ELECTROSTATIC ROUTES, BECAUSE OF THE TENDENCY TO PRODUCE MATERIALS WITH THICKER WALLS AND SMALLER PARTICLE SIZES [3].METHODS: IN THIS PAPER, HIGH SURFACE AREA MESOPOROUS SILICA POWDER HAS BEEN PREPARED BY Sol-gel METHODS. MOREOVER THE EFFECT OF SODIUM SILICATE CONCENTRATION HAS BEEN INVESTIGATED ON THE SURFACE AREA (BET) AND PORE VOLUME OF THE CATALYSTS.RESULTS: IN THIS STUDY, THE SILICA POWDER WAS PRODUCTED FROM BOTH THE WASHING AND DRYING gel AND THEN WE COMPARE TWO DIFFERENT CONCENTRATION OF SODIUM SILICATE SolUTION TO PREPARE SILICA POWDER BY MEANS OF BET.CONCLUSION: THE SYNTHESIS SILICA SUPPORT SHOWED HIGH SPECIFIC SURFACE AREA. THE RESULTS SHOWED THAT SODIUM SILICATE CONCENTRATION EFFECTS ON THE CATALYST MORPHOLOGY AND CATALYTIC PERFORMANCE.