Apparatus and process for atomic or molecular layer deposition onto particles during pneumatic transport

Abstract

The invention provides a process for depositing a coating onto particles being pneumatically transported in a tube. The process comprising the steps of providing a tube having an inlet opening and an outlet opening; feeding a carrier gas entraining particles into the tube at or near the inlet opening of the tube to create a particle flow through the tube; and injecting a first self-terminating reactant into the tube via at least one injection point downstream from the inlet opening of the tube for reaction with the particles in the particle flow. The process is suitable for atomic layer deposition and molecular layer deposition. An apparatus for carrying out the process is also disclosed.

What is claimed is: 
     
         1 . An apparatus comprising:
 a tube having an inlet opening and an outlet opening;   (ii) a feeder device for feeding a carrier gas entraining the particles into the tube, thereby pneumatically transporting the particles in the tube; and   (iii) a plurality of injection points downstream from the inlet opening for introducing two or more different reactants via different injections points of the plurality of injections points into the tube, for atomic or molecular layer deposition on the particles.   
     
     
         2 . The apparatus of  claim 1 , wherein the apparatus comprises a plurality of injection points spaced apart along at least a portion of the length of the tube. 
     
     
         3 . The apparatus of  claim 1 , wherein the tube is provided with a plurality of injection points numbered sequentially from the inlet opening of the tube; wherein odd-numbered injection points are arranged for injection of a first self-terminating reactant; and even-numbered injection points are arranged for injection of a second self-terminating reactant. 
     
     
         4 . The apparatus of  claim 1 , further comprising one or more flush points along at least part of the length of the tube for removing reaction by-products from the tube. 
     
     
         5 . The apparatus of  claim 1 , wherein the apparatus is further configured to increase a linear velocity of the carrier gas downstream from the one or more flush points. 
     
     
         6 . The apparatus of  claim 4 , wherein one or more flush points comprise a filter to allow reaction products to be removed while keeping the particles in the tube. 
     
     
         7 . The apparatus of  claim 1 , wherein the tube has an internal diameter in the range of from 0.02 mm to 300 mm. 
     
     
         8 . The apparatus of  claim 1 , wherein the tube has a length of from 0.1 m to 500 m, and wherein the tube is folded or coiled. 
     
     
         9 . The apparatus of  claim 1 , wherein the tube is contained in a chamber provided with means for heating and/or means for cooling, wherein the chamber can be kept at a temperature in the range of from 0° C. to 1000° C., wherein different parts of the tube can be kept at different temperatures, wherein the tube is provided with a plurality of injection points numbered sequentially from the inlet opening of the tube; wherein odd-numbered injection points are arranged for injection of a first self-terminating reactant; and even-numbered injection points are arranged for injection of a second self-terminating reactant, and wherein tube segments downstream from odd-numbered injection points and upstream to even-numbered injection points are arranged to be kept at a first temperature, and tube segments downstream from even-numbered injection points and upstream to odd-numbered injection points are arranged to be kept at a second temperature. 
     
     
         10 . A process for depositing a coating onto particles being pneumatically transported in a tube, said process comprising the steps of:
 providing a tube having an inlet opening and an outlet opening and a plurality of injection points;   (ii) feeding a carrier gas entraining particles into the tube at or near the inlet opening of the tube to create a particle flow through the tube; and   (iii) introducing two or more different reactants via different injections points of the plurality of injections points into the tube, for atomic or molecular layer deposition on the particles.   
     
     
         11 . The process of  claim 10 , wherein the particles comprise agglomerates of smaller particles. 
     
     
         12 . The process of  claim 10 , wherein a first reactant is injected into the tube via a plurality of injection points downstream from the inlet opening of the tube, and an injection point downstream from another injection point is arranged to increase the velocity of the carrier gas, wherein the injection points are spaced along at least a portion of the length of the tube, and wherein the injection points are spaced along substantially the length of the tube. 
     
     
         13 . The process of  claim 10 , further comprising pre-conditioning the particles in the tube upstream of an injection point. 
     
     
         14 . The process of  claim 10 , further comprising injecting a second self-terminating reactant into the tube via at least one further injection point downstream from the at least one injection point for reaction with particles in the particle flow, wherein the first reactant is a precursor for the second reactant, wherein the further injection point is arranged to increase the velocity of the carrier gas. 
     
     
         15 . The process of  claim 10 , wherein the carrier gas is fed at such velocity that the carrier gas velocity is greater than the particle velocity in the particle flow. 
     
     
         16 . The process of  claim 10 , wherein the particle flow takes the form of a plug flow. 
     
     
         17 . The process of  claim 10 , further comprising removing reaction by-products from the tube at at least one flush point or wherein reaction by-products are removed from the tube at a plurality of flush points spaced along the length of the tube. 
     
     
         18 . The process of  claim 10 , further comprising keeping different parts of the tube at different temperatures, wherein the tube is provided with a plurality of injection points numbered sequentially from the inlet opening of the tube; wherein a first self-terminating reactant is injected into the odd-numbered injection points; and a second self-terminating reactant is injected into the even-numbered injection points, wherein the injection points are spaced such that a self-terminating reaction is substantially self-terminated between injection points, the process further comprising:
 keeping tube segments downstream from odd-numbered injection points and upstream to even-numbered injection points at a first temperature; and   keeping tube segments downstream from even-numbered injection points and upstream to odd-numbered injection points at a second temperature.   
     
     
         19 . The process of  claim 10 , wherein the carrier gas is an inert gas, wherein the carrier gas travels through the tube at a linear velocity of from 0.02 to 30 m/s, and wherein the particle size of the particles being coated is in the range of from 2 nm to 1 mm. 
     
     
         20 . The process of  claim 17 , further comprising increasing a linear velocity of the carrier gas downstream from one or more flush points. 
     
     
         21 . The process of  claim 17 , wherein one or more flush points comprise a filter, and wherein the process further comprises removing reaction products via one or more flush points, while keeping the particles in the tube.