Near infrared transmitting copper oxide nanoparticles
A black IR reflective or transmissive pigment from which LiDAR responsive black coatings can be formed where the pigment displays a Blackness M y value similar to non-IR reflective carbon black. The CuO particles display small crystallites of less than 18 nm and an (−111)/(111) reflectance intensity ratio of less than 1.2. A method of forming the CuO particles includes precipitation of CuCO3 or CuCO 3 /Cu(OH) 2 using an alkali carbonate as a precipitant and calcining the precipitate at about 300° C. to about 400° C.
1 . A black pigment with near IR transmitting and/or reflecting properties, the black pigment comprising
a plurality of CuO crystallites with a maximum dimension of 18 nm or less, and a (−111)/(111) intensity ratio of less than 1.2, wherein the black pigment displays a band gap of 1.7 eV or less.
2 . The black pigment according to claim 1 , wherein
the CuO crystallites are present on at least a portion of an outer surface of particles, and
a diameter dimension of the particles is from about 50 nm to about 10 μm.
3 . The black pigment according to claim 2 , wherein the particles comprise a core portion comprising one of mica, synthetic mica, glass, quartz, or alumina.
4 . The black pigment according to claim 3 , wherein the portion of the outer surface comprising CuO has a thickness of less than about 50 nm.
5 . The black pigment according to claim 3 , wherein the portion of the outer surface comprising CuO is a continuous or a non-continuous shell on the core.
6 . The black pigment according to claim 1 , wherein the crystallites have a maximum dimension of 15 nm or less.
7 . A coating composition, comprising: a fluid vehicle; and a black pigment with near IR transmitting and/or reflecting properties suspended in the fluid vehicle, wherein the black pigment comprises CuO crystallites with a maximum dimension of 18 nm or less, and a (−111)/(111) intensity ratio of less than 1.2, and wherein the coating composition displays a band gap of −1.7 eV or less.
8 . The coating composition according to claim 7 , wherein
the CuO crystallites are present on at least a portion of an outer surface of particles, and
the particles are 50 nm to 10 μm in cross-section.
9 . The coating composition according to claim 8 , wherein the particles comprise a core portion comprising one of mica, synthetic mica, glass, quartz, or alumina.
10 . The coating composition according to claim 9 , wherein the portion of the outer surface comprising CuO has a thickness of less than about 50 nm.
11 . The coating composition according to claim 7 , wherein the crystallites have a maximum dimension of 15 nm or less.
12 . The coating composition according to claim 7 , wherein the black pigment in the coating composition exhibits a Blackness M y value of at least 132.
13 . A method for forming near IR reflecting or transmitting CuO crystallites, comprising:
providing a solution or a suspension comprising a water-soluble Cu(II) salt;
adding a precipitant solution comprising an alkali metal carbonate with the solution or the suspension to form a precipitate comprising CuCO 3 ;
washing the precipitate with water;
isolating the precipitate; and
calcining the precipitate at a temperature between about 300 and about 400° C. to form the near IR reflecting or transmitting CuO crystallites, wherein the CuO crystallites have a maximum dimension of 18 nm or less, and a (−111)/(111) intensity ratio less than 1.2, wherein the CuO crystallites display a band gap of 1.7 eV or less.
14 . The method according to claim 13 , wherein the water-soluble Cu(II) salt comprises Cu (NO 3 ) 2 .
15 . The method according to claim 13 , wherein the suspension comprises a suspension of core forming particles wherein the precipitate comprises a shell on the core forming particles.
16 . The method according to claim 15 , wherein the core forming particles comprise at least one of mica, synthetic mica, glass, quartz, or alumina.
17 . The method according to claim 13 , wherein the step of isolating the precipitate comprises filtering or centrifuging the precipitate, and the method further comprises drying the precipitate after isolating to form a dry precipitate.
18 . The method according to claim 13 , further comprising grinding the precipitate.
19 . The method according to claim 13 , further comprising grinding the near IR reflecting or transmitting CuO crystallites.
20 . The black pigment according to claim 1 , wherein the plurality of CuO crystallites form particle aggregates having a dimension of more than 6 μm.
21 . The coating composition according to claim 7 , wherein the CuO crystallites form particle aggregates having a dimension of more than 6 μm.
22 . The method according to claim 13 , wherein the CuO crystallites form particle aggregates having a dimension of more than 6 μm.