Process for the Preparation of Uniform Sized Phosphor Aerogel

Patent metadata

Field	Value
Publication number	US-2017349445-A1
Application number	US-201715612540-A
Country	US
Kind code	A1
Filing date	Jun 2, 2017
Priority date	Jun 6, 2016
Publication date	Dec 7, 2017
Grant date	—

Abstract

The present invention provides a process for the preparation of phosphor aerogel of uniform size having high porosity, low density; high thermal insulation and high luminescence, which is useful for various applications like lighting, display, sensing and other applications.
More specifically, the present invention provides a simple and versatile process for the formation of monolithic gel, at room temperature, which on further drying at supercritical temperature and pressure result in dry aerogel. Further, annealing under mild reduced atmosphere from 1000°-1400° C. not only retains the porous network with uniform size particles but also crystallizes to form a phosphor aerogel having brightest luminescence with bulk density as low as 100 kg m-3, and strong enough to support a weight much higher than its own weight.

First claim

We claim:

1 . A process for the preparation of uniform sized phosphor aerogel comprising:
a) dissolving the alkoxide,transition metal salt and/or alkaline earth metal salt, dopant,polar solvent,demineralized water in molar ratio ranging from 1:1-2:1-20:5-10:4-10 to obtain a clear transparent solution forming a wet gel within 30 min to 5 hours;b) the wet gel obtained in step (a) was subjected to supercritical drying in an autoclave for 5-6 hours at temperature ranging from 250° C. to 300° C. at 60-120 bars pressure to obtain a dried aerogel followed by 2-3 times nitrogen gas flushing to remove adsorbed solvent molecules from the pores of dried aerogel;c)subjecting the dried aerogel as obtained in step (b) to annealing treatment in a controlled atmosphere of high temperature furnace at a temperature in the range of 800° C. to 1500° C. for 1-5 hours so as to obtain the desired phosphor aerogel.

2 . The process as claimed in claim 1 , wherein the molar ratio of alkoxide,transition metal salt and/or alkaline earth metal salt,dopant,polar solvent anddemineralized water is 1:1-2:1-20:10:4 in which the gelation time is least.

3 . The process as claimed in claim 1 , wherein the said process yields >95% of several visible and/or near infrared color-emitting phosphor aerogels including violet, indigo, blue, green, yellow, orange, red for luminescence applications.

4 . The process as claimed in claim 1 , wherein the polar solvent is selected from the group consisting of methanol, ethanol, isopropyl alcohol, acetone, demineralized water.

5 . The process as claimed in claim 1 , wherein the transition metals and/or alkaline earth metals are selected from the group consisting of zinc, cadmium, nickel, beryllium, magnesium, calcium, strontium and barium.

6 . The process as claimed in claim 1 , wherein the dopant is a soluble salt of transition metal and/or rare-earth metal selected from the group consisting of manganese, copper, silver, cobalt, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.

7 . The process as claimed in claim 1 , wherein the concentration of dopant varies from 1-20 mol% of the precursor salt.

8 . The process as claimed in claim 1 , wherein the temperature for autoclaving the wet gels ranges from 250° C. to 300° C. for 5-6 hours and pressure ranges from 60 to 120 bars.

9 . The process as claimed in claim 1 , wherein the aerogels are annealed under controlled atmosphere at temperature ranging from 800° C. to 1500° C. in a high temperature furnace for 1 to 5 hours.

10 . A Phosphor aerogel obtained by the process as claimed in claim 1 , having particle size in the range of 5-25 nm within ±2 nm size distribution, high porosity of >90% and low density of <100 kg m −3 , exhibiting thermal insulating properties, emitting wide range of colors in the visible and/or near infrared range from 400-1500 nm when excited by ultra violet light having wavelength in the range of 200 to 400 nm and useful in light weight insulted display devices.

11 . The Phosphor aerogels as claimed in claim 10 , wherein the phosphor aerogels are in the form of powder or in the form of desired shapes selected from square, rectangular, cylindrical and circular.

Assignees

• Council Scient Ind Res

Inventors

• Divi Haranath
• Singh Nahar
• Chawla Sneha

Classifications

• C01B25/36

  Aluminium phosphates · CPC title

• C01B33/1585 Primary

  Dehydration into aerogels · CPC title

• C01B25/265

  General methods for obtaining phosphates · CPC title

• C01B25/372

  of titanium, vanadium, zirconium, niobium, hafnium or tantalum · CPC title

• C09K11/595

  with zinc or cadmium · CPC title