METHODS OF MAKING HONEYCOMB BODIES WITH TRACER PARTICLES

Cross Reference to Related Application

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63/412026, filed on September 30, 2022, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present specification relates to methods of evaluating and methods of making porous bodies, or filter bodies, such as porous ceramic honeycomb bodies (filter bodies), with tracer particles.

Technical Background

[0003] Wall-flow filters are employed to remove particulates from fluid exhaust streams, such as from combustion engine exhaust. Examples include diesel particulate filters used to remove particulates from diesel engine exhaust gases and gasoline particulate filters (GPF) used to remove particulates from gasoline engine exhaust gases. Exhaust gas to be filtered enters inlet cells and passes through the cell walls to exit the filter via outlet channels, with the particulates being trapped on or within the inlet cell walls as the gas traverses and then exits the filter.

SUMMARY

[0004] Aspects of this disclosure pertain to porous bodies and methods for their manufacture and use, such as filter bodies with honeycomb matrix structures, which can be in the form of particulate filters, such as gasoline particulate filters.

[0005] In one aspect, a particulate filter body comprising a honeycomb structure comprised of intersecting porous walls having wall surfaces services that define axial channels extending from a first end (configured to be mounted or implemented as an upstream end, or inlet end) in an axial direction to a second end (configured to be mounted or implemented as a downstream end or outlet end), the honeycomb structure comprising plugging material disposed in at least some of the axial channels at the upstream end, and disposed in at least some of the axial channels at the downstream end, wherein particulate matter is disposed on the wall surfaces or in the walls, and wherein the particulate matter comprises tracer particles and non-tracer particles.

[0006] In embodiments, the tracer particles are comprised of a fluorescent material.

[0007] In embodiments, the tracer particles are comprised of quantum dots.

[0008] In embodiments, the tracer particles and the non-tracer particles have differing compositions.

[0009] In embodiments, the porous walls, the tracer particles and the non-tracer particles have differing compositions.

[0010] In embodiments, the particulate matter comprises one or more compositions which differ from a composition of the porous walls.

[0011] In embodiments, each of the tracer particles and the non-tracer particles differ in composition from a composition of the porous walls.

[0012] In embodiments, at least a portion of the particulate matter is deposited onto the wall surfaces, and the tracer particles and the non-tracer particles are trapped on or in the walls of the particulate filter body.

[0013] In embodiments, the majority of the tracer particles are disposed on or within the porous walls to a penetration depth not greater than 5 pm.

[0014] In embodiments, the non-tracer particles are comprised of alumina, silica, or a combination thereof.

[0015] In embodiments, the non-tracer particles are comprised of aggregates of agglomerates comprised of inorganic material nanoparticles. In some of these embodiments, the aggregates are further comprised of an inorganic binder; and some of these embodiments, [0016] the aggregates are further comprised of a silicon-containing binder.

[0017] In embodiments, the non-tracer particles are present at a loading of 0.05 to 50 grams per volume of honeycomb filter body in liters (grams/L).

[0018] In embodiments, the non-tracer particles are present at a loading of 0.1 to 20 grams per volume of honeycomb filter body in liters (grams/L).

[0019] In embodiments, the tracer particles are present at a loading of 0.001 to 0.050 grams per volume of honeycomb filter body in liters (grams/L). [0020] In embodiments, the tracer particles are present at a loading of 0.001 to 0.02 grams per volume of honeycomb filter body in liters (grams/L).

[0021] In embodiments, the tracer particles are present at a loading of 0.001 to 0.01 grams per volume of honeycomb filter body in liters (grams/L).

[0022] In another aspect, a method of manufacturing a particulate filter body is disclosed herein, the filter body comprising a honeycomb structure comprised of intersecting porous walls having wall surfaces services that define axial channels extending from an upstream end ( or inlet end) to a downstream end (or outlet end], the honeycomb structure comprising plugging material disposed in at least some of the axial channels at the upstream end, and disposed in at least some of the axial channels at the downstream end, the method comprising: introducing an upstream flow comprised of one or more fluids and suspended particulate matter into the upstream end of the particulate filter body, wherein the particulate matter comprises tracer particles and non-tracer particles; and depositing at least a portion of the particulate matter onto the wall surfaces, wherein tracer particles and non-tracer particles are trapped on or in the walls of the particulate filter body.

[0023] In embodiments, irradiation (or illumination) of the upstream flow and the downstream flow causes the tracer particles to emit scattered light. In some of these embodiments,

[0024] the irradiation of the upstream flow and downstream flow occur within 5 seconds of each other; in other embodiments, the irradiation of the upstream flow and downstream flow occur simultaneously.

[0025] In embodiments, the method further comprises detecting the scattered light in the upstream and downstream flows to determine respective particle counts or particle concentrations in the upstream and downstream flows. In some of these embodiments,

[0026] the detecting the scattered light in the upstream and downstream flows occur within 5 seconds of each other. In some of these embodiments, the detecting the scattered light in the upstream and downstream flows occur simultaneously.

[0027] In embodiments, the method further comprises determining a filtration efficiency of the particulate filter body from the respective particle counts or particle concentrations.

[0028] In embodiments, the method further comprises terminating the upstream flow into the particulate filter body when, or after, a target filtration efficiency has been determined. [0029] In embodiments, a downstream flow exiting the downstream end of the particulate filter body contains less particulate matter than the upstream flow, entering the upstream end of the filter body.

[0030] In another aspect, disclosed herein is a method for evaluating the filtration effect of a particulate filter body having an upstream end and a downstream end, the method comprising: introducing an upstream flow comprised of one or more fluids and suspended particulate matter into the upstream end of the particulate filter body, wherein the particulate matter comprises tracer particles and non-tracer particles; trapping at least some of the suspended particulate matter with the particulate filter body, such that a downstream flow exiting the downstream end of the particulate filter body contains less particulate matter than the upstream flow; irradiating at least a portion of the upstream flow with excitation light to allow at least some of the particulate matter to emit scattered light; detecting the scattered light in the upstream flow; irradiating at least a portion of the downstream flow with excitation light to allow at least some of the particulate matter to emit scattered light (which is due to their scattering the measurement light); detecting the scattered light in the downstream flow; and determining the filtration efficiency of the particulate filter body from the differences in the scattered light in the upstream and downstream flows.

[0031] In embodiments, the particulate filter body comprises a microstructure which allows at least some of the tracer particles to pass through, and exit the downstream end of, the particulate filter body.

[0032] In embodiments, the method further comprises isolating one or more wavelengths of the scattered light from the upstream flow, the downstream flow, or both. In some of these embodiments, one or more isolated wavelengths are detected in the upstream flow, the downstream flow, or both.

[0033] In embodiments, a bandpass filter isolates one or more wavelengths of the scattered light from the upstream flow, the downstream flow, or both.

[0034] In embodiments, the scattered light in the upstream flow and in the downstream flow are converted into respective electrical pulses, and the electrical pulses are converted into respective particle counts. In some of these embodiments, the number and/or concentration of the tracer particles in the upstream flow are adjusted to increase the strength and/or quality of the electrical pulse signals derived from light scattered in the upstream flow; in other of these embodiments, the respective particle counts are determined by an optical particle counter. In some of these embodiments, the optical particle counter comprises a bandpass filter which is tuned to isolate the signal of the tracer particles from the schedule light signal from all particles; in other embodiments, the optical particle counter comprises a bandpass filter which is tuned to filter out the scattered light signal of the non-tracer particles; in other embodiments, the optical particle counter comprises a bandpass filter which is tuned to isolate the scattered light signal of the tracer particles and to filter out the scattered light signal of the non-tracer particles; in other embodiments, the optical particle counter comprises a laser light source, one or more collecting lenses, and a photodetector; and in other embodiments, the optical particle counter comprises a laser light source, one or more collecting lenses, a photodetector, and a bandpass filter which allows scattered light at one or more selected wavelengths to reach the photodetector while preventing scattered light at other wavelengths from reaching the photodetector.

[0035] In embodiments, the concentration of the tracer particles and/or the aerosol droplet size in the upstream flow is adjusted to maximize the strength and/or quality of the scattered light signal.

[0036] In embodiments, a filtration efficiency is determined at least in part from the particle counts.

[0037] In embodiments, the tracer particles emit scattered light in the low visible spectrum.

[0038] In embodiments, the tracer particles emit scattered light at or near 400 nm.

[0039] In embodiments, the excitation light is laser light. In some of these embodiments, the laser light produces excitation light in the ultraviolet (UV) range. In other embodiments, the laser light produces excitation light at or near 375 nm. in other embodiments, the laser light produces excitation light at or near 375 nm.

[0040] In embodiments, the excitation light is in the ultraviolet (UV) range, and the tracer particles emit scattered light in the low visible spectrum. In some of these embodiments, the excitation light is at or near 375 nm, and the tracer particles emit scattered light at or near 400 nm.

[0041] In embodiments, the tracer particles are comprised of nano-scale synthetic crystal.

[0042] In embodiments, the tracer particles are comprised of quantum dots.

[0043] In embodiments, the tracer particles have a particle size of from 2 nm to 6 nm. [0044] In embodiments, the tracer particles emit scattered light at wavelengths from 2 nm to 6 nm. in some of these embodiments, the tracer particles are quantum dots.

[0045] In embodiments, the tracer particles emit scattered light at one or more wavelengths selected from the group consisting of 2, 2.5, 3, 5, and 6 nm. in some of these embodiments, the tracer particles are quantum dots.

[0046] In embodiments, the excitation light irradiating the upstream flow is different from the excitation light irradiating the downstream flow.

[0047] In embodiments, the excitation light is tuned to one or more respective tracer particle types.

[0048] In embodiments, the tracer particles are injected into an optical particle counter system.

[0049] In embodiments, the tracer particles are introduced into and suspended within the upstream flow.

[0050] In embodiments, the tracer particles are aerosolized prior to introduction into the upstream flow.

[0051] In embodiments, the suspension flow comprises an aerosol flow.

[0052] In embodiments, the particulate filter body is a plugged honeycomb body.

[0053] In embodiments, the plugged honeycomb body comprises a honeycomb structure comprised of intersecting porous ceramic walls having wall surfaces that define axial channels, wherein at least some of the axial channels are plugged at the upstream end, and at least some of the axial channels are plugged at the downstream end.

[0054] In embodiments, the tracer particles comprise submicron tracer particles.

[0055] In embodiments, the tracer particles are submicron tracer particles.

[0056] In embodiments, the tracer particles have a particle size of greater than 0.05 pm.

[0057] In embodiments, the tracer particles have a particle size of greater than 0.10 pm.

[0058] In embodiments, the tracer particles have a particle size of greater than 0.20 pm.

[0059] In embodiments, the tracer particles have a particle size of about 0.05 to about 0.3 pm.

[0060] In embodiments, the tracer particles have a particle size of about 0.1 to about 0.3 pm. [0061] In embodiments, the tracer particles have a particle size of about 0.2 to about 0.3 pm. [0062] In embodiments, the tracer particles in the upstream flow are present in a concentration of 10 to 900 particles per cubic centimeter.

[0063] In embodiments, the tracer particles in the upstream flow are present in a concentration of 50 to 500 particles per cubic centimeter.

[0064] In embodiments, the tracer particles in the upstream flow are present in a concentration of 50 to 250 particles per cubic centimeter.

[0065] In embodiments, the tracer particles comprise fluorescent particles.

[0066] In embodiments, the tracer particles comprise fluorescent microspheres.

[0067] In embodiments, the tracer particles comprise quantum dots. In some of these embodiments, the quantum dots are conveyed to the particulate filter body as aerosol droplets. [0068] In another aspect, disclosed herein is a method for evaluating the filtration effect of a particulate filter body having an upstream end and a downstream end, the method comprising: introducing an upstream flow comprised of one or more fluids and suspended particulate matter into the upstream end of the particulate filter body, wherein the particulate matter comprises tracer particles; trapping at least some of the suspended particulate matter with the particulate filter body, such that a downstream flow exiting the downstream end of the particulate filter body contains less particulate matter than the upstream flow; irradiating at least a portion of the upstream flow with excitation light to allow at least some of the particulate matter to emit scattered light; detecting the scattered light in the upstream flow; irradiating at least a portion of the downstream flow with excitation light to allow at least some of the particulate matter to emit scattered light; detecting the scattered light in the downstream flow; and determining the filtration efficiency of the particulate filter body from the differences in the scattered light in the upstream and downstream flows.

[0069] In embodiments, the particulate matter further comprises non-tracer particles.

[0070] Additional features and advantages will be set forth in the detailed description, which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, comprising the detailed description, which follows, the claims, as well as the appended drawings.

[0071] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. l is a schematic representation of a known optical particle counter.

[0073] FIG. 2 schematically illustrates an embodiment disclosed herein of a modified optical particle counter that uses tracer particles (represented by hollow circles) and a bandpass filter to isolate the signal of the tracer particles from the scattered light signal from all particles.

[0074] FIG. 3 is a flowchart depicting an exemplary embodiment of a process of generating agglomerates and applying filtration material deposits according to embodiments disclosed herein.

[0075] FIG. 4 is an exemplary apparatus for processes to deposit inorganic material with binder on ceramic honeycomb bodies which can be used with tracer particles as described herein.

[0076] FIG. 5 schematically depicts a plugged honeycomb filter body in the form of a wallflow particulate filter according to embodiments disclosed and described herein;

[0077] FIG. 6 is a cross-sectional longitudinal view (in the axial direction) of a portion of the filter body shown in FIG. 4.

[0078] FIG. 7 schematically depicts an axial cross section of a portion of the particulate filter of FIG. 5.

DETAILED DESCRIPTION

[0079] Reference will now be made in detail to embodiments of methods for forming honeycomb bodies comprising a porous honeycomb body comprising deposits on, or in, or both on and in, the porous ceramic walls of the honeycomb body matrix, embodiments of which are illustrated in the accompanying drawings. In embodiments the honeycomb body matrix is a honeycomb structure such as a monolithic honeycomb, for example as produced via extrusion through a honeycomb die; or in other embodiments the honeycomb body matrix comprises two or more blocks or segments of honeycomb matrix which are included or bound together such as by cement. Deposits may comprise material that was deposited into the honeycomb body, as well as compounds that may be formed, for example, by heating, from one or materials that were deposited. For example, a binder material may be transformed by heating into an organic component which is eventually burned off or volatilized, while an inorganic component (such as silica) remains contained within the honeycomb filter body. Deposits of one or more types may be used as sacrificial deposits, or even sacrificial layers. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

Definitions

[0080] As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

[0081] As used herein, "have", "having", "include", "including", "comprise", "comprising" or the like are used in their open-ended sense, and generally mean "including, but not limited to".

[0082] A "honeycomb body," as referred to herein, comprises a ceramic honeycomb structure of a matrix of intersecting walls that form cells which define channels. The ceramic honeycomb structure can be formed, extruded, or molded from a plasticized ceramic or ceramic-forming batch mixture or paste. A honeycomb body may comprise an outer peripheral wall, or skin, which was either extruded along with the matrix of walls or applied after the extrusion of the matrix. A filter body comprise an unplugged honeycomb structure or a plugged honeycomb structure. For example, a honeycomb body can be a plugged ceramic honeycomb structure which forms a filter body comprised of cordierite or other suitable ceramic material. A plugged honeycomb body has one or more channels plugged at one, or both ends of the body. [0083] A honeycomb body disclosed herein comprises a ceramic honeycomb structure comprising at least one wall supporting one or more particulate deposits for example which may be configured to filter particulate matter from a gas stream. The deposits can be in discrete regions or in some portions or some embodiments can form one or more layers of deposit material at a given location on the wall of the honeycomb body. The deposits according to some embodiments comprise inorganic material, in some embodiments organic material, and in some embodiments both inorganic material and organic material. For example, a honeycomb structure of a honeycomb body may, in one or more embodiments, be formed from cordierite or other porous ceramic material and further comprise material deposits disposed on or below wall surfaces of the cordierite honeycomb structure.

[0084] In some embodiments, a second type of deposit material comprises one or more inorganic materials, such as one or more ceramic or refractory materials.

[0085] As used herein, "green" or "green ceramic" are used interchangeably and refer to an unsintered or unfired material, unless otherwise specified.

[0086] Particle counters and spectrometers may be designed to detect all particles within a sample. Being dependent upon detecting all particles may be disadvantageous in measuring the filtration efficiency of particulate filters, especially for very high initial filtration efficiency particulate filters such as gasoline particulate filters, for example because the filtration efficiency can be very sensitive to the specific particles being measured, such as size, composition, charge, and other parameters. Preferably the particle source is controlled as well to prevent any contamination, however such non-contamination can be extremely difficult to achieve in a manufacturing environment. As described herein, we have found that light emitting tracer particles can be optically separated from other particles in the system which are not needed or unwanted in the determination of filtration efficiency, and therefore methods and apparatus are disclosed herein which can provide a very high level of control over the measurement process. Such precision and control can be especially important for measuring ultra-high filtration efficiency particulate filters such as ultra-high FE GPFs with a filter body having an initial or clean filtration efficiency of 99% or greater than 99%, as very few particles escape the particulate filter even when clean such as when new.

[0087] Also, filtration efficiency measurement systems might rely on particle counting upstream and downstream of a predicted filter, and a variety of different methods may be implemented to detect and count particles of different sizes. However, optical measurement systems typically rely on scattered light and therefore are constrained to particles larger than 0.2 pm in diameter for systems which operate in commercial industrial sizes and volumes of filters to be produced and/or measured. Although small size particles might be detected with using other methods, the particle concentration in those methods would need to be quite great, for example more than millions of particles per cubic centimeter in order to get a reasonable signal-to-noise ratio; such high particle concentrations required by those methods are ill-suited for working with gasoline particulate filters, as those concentrations may result in undesirable “soot-loading” of the GPF and may change the characteristics of the GPF due to the measurement itself, and therefore would require additional processing steps to clean or regenerate or otherwise revert the filter body of the GPF to its original clean or initial state. We have found that the particle size range near 0.2 pm is also advantageous because the filtration efficiency curves of GPF’s have a minimum where the particle capture mechanisms change from diffusion dominated to interception dominated. Moreover, optical particle counting does not need to rely on very high particle concentrations for accurate measuring; for example, hundreds of particles per cubic centimeter can suffice. The filtration efficiency of a GPF at that particle size range can be correlated to engine-exhaust measurements. At ultra-high FE levels and low particle concentrations upstream of the GPF, the downstream particle measurement can become noise dominated and can pose a problem for achieving precision. In some cases, the source for the noise in the measurement may be the cleanliness of the measurement system itself. Furthermore, in a manufacturing environment, as many GPF filter pieces as possible need to be measured as quickly as possible, yet measurement systems get contaminated through repeated opening/closing to atmospheric conditions for GPF filter body -loading (as opposed to measurements performed in a clean room), and therefore the FE measurement ought to be conducted relatively quickly, as in a manufacturing environment extended times for long timeaverages for measurements cannot be tolerated. Although particles used in measurement systems can be provided by an aerosol generator, which does give some control over the particle generation by selecting operating conditions and the type of solution (e. g. pressure setpoints), the use of an aerosol generator might constrain the measurement system (for example aerosol measurements could not be carried out at very high temperatures) and therefore does not eliminate the issue of separating source particles from contamination.

[0088] The methods and apparatus disclosed herein can be used to obtain accurate measurement of ultra-high filtration efficiency gasoline particulate filters by optically isolating specific tracer particles from all other (unwanted) particles in the measurement system. Such methods and apparatus could even be implemented in a manufacturing environment. Such tracer particles could be, for example, fluorescent microspheres or quantum dots, which can be injected into a measurement system directly, or in the case of quantum dots, be suspended and enter the measurement system through an aerosol generator. If using quantum dots, measurement of individual quantum dots is not necessary if enough dots are suspended in the aerosol to provide a good signal. The tracer particle concentration and aerosol droplet size can be adjusted independently to maximize the signal. Advantageously, as the filtration efficiency is a measure of a ratio of particles upstream and downstream of the filter, the signal does not necessarily have to be calibrated to an absolute particle size measurement. The excitation wavelength can be tuned to the specific tracers by selecting an appropriate light source, for example a laser light source or “laser source”. The emitted light of the tracers can then be isolated from the scattered light from all particles using a bandpass filter in front of a photodetector, which could help eliminate the need to conduct measurement in a clean room environment and could help to achieve a high level of control over the measurement process. [0089] Various effects can influence a particle depending on particle size. For example, diffusion and electrostatic forces are important for particle diameters less than 0.3 pm, while interception by an object is important for particle diameters between 0.3 and 1 pm, and inertial impaction is important for particle sizes from 1 to 10 pm. Sieving has an effect for particle sizes greater than 1 pm, while gravity and clogging are larger facts for particles greater than 10 pm. A filtration efficiency curve plotted as a function of particle size could illustrate the filtration forces that contribute to collection efficiency: interception, diffusion, impaction, and settling. A minimum in the combined total filtration efficiency occurs near 0.2 pm. We have found that more particles will be able to pass through the particulate filter in this size range and therefore increase the strength and/or clarity and or quality of the downstream signal, which becomes increasingly more important at higher filtration efficiencies; for example, only about 1% of the particles that enter a high filtration efficiency particulate filter eventually might pass through the particulate filter and travel downstream, whereas 99% of those upstream particles are trapped by the particulate filter.

[0090] In embodiments herein, tracer particles in the system can be excited using a laser source, for example in the UV range (e.g. 375 nm), prompting the tracer particles to emit light in the low visible spectrum near 400 nm. The laser light from the source and the scattered light can then be removed with a bandpass filter, and only the tracer particles will be detected.

[0091] Quantum dots could also be used, for example instead of fluorescent microspheres. Due to their small size, quantum dots can be injected into the measurement system via an aerosol generator, so for example many quantum dots can be contained in each individual aerosol droplet emanating from an aerosol generator, eliminating the need to measure individual quantum dots.

[0092] In commercial optical particle counters, as illustrated in FIG. 1, particles in the sample flow scatter the laser light, which is focused on the detector and translated into an electrical signal that can be processed to infer the particle size. Noting that forward-scatter has a high signal amplitude, the source of the particles needs to be controlled, because the scattered light of all particles in the system will be measured. For example, if the measurement system downstream of the GPF is contaminated, negative FE measurement values could be erroneously generated, which would be solely due to measurement error; such difficulties give rise to a main limitation of existing commercial optical particle counters for measuring ultra- high FE levels of particulate filters. Even if all contamination could be removed by running such systems for a very long period of time, such procedure is not feasible in a fast-paced manufacturing environment.

[0093] FIG. 2 schematically illustrates an embodiment of a modified optical particle counter 10 that uses tracer particles 20 (represented by hollow circles) and a bandpass filter 30 to isolate the signal of the tracer particles 20 from the scattered light signal 40 from all particles, that is, tracer particles 20 (represented by hollow circles) and particles to be removed such as engine- emitted particles (represented by solid filled-in circles). The emitted light 58 of the fluorescent tracer particles 20 has the greatest amplitude in the direction of the laser source 50, whose laser source light 52 passes through a first lens 54 to intercept the sampling particles and then passes through a second lens 56 and bandpass filter 30 and on to the photodetector 60, so we have found the placement and orientation of the photodetector 60 should be adjusted to maximize that signal.

[0094] The methods disclosed herein can be useful in evaluating the filtering effect, or filtration efficiency, of a particulate filter, such as a filter comprising a bare honeycomb body, or a filter comprising a honeycomb body with other material deposited thereon or therein, such as filtration material deposits, a layer, a membrane, and/or catalytic material.

[0095] The methods disclosed herein can be useful in adding deposits to the surfaces of porous walls of the particulate filters, such as to measure FE online during the deposition of the filtration material process, such as to provide an indication that deposition may terminate, such by reaching a target FE for the filter body.

[0096] Also disclosed herein is a filter body comprising tracer particles. Tracer particles in filter bodies can help provide source identification, process control information, and/or inventory control information.

[0097] In one aspect, the present disclosure thus pertains to methods for evaluating the filtration effect of a particulate filter body having an upstream end (or inlet end) and a downstream end (or outlet end), the method comprising: introducing an upstream flow comprised of one or more fluids and suspended particulate matter into the upstream end of the particulate filter body, wherein the particulate matter comprises tracer particles, trapping at least some of the suspended particulate matter with the particulate filter body, such that a downstream flow exiting the downstream end of the particulate filter body contains less particulate matter than the upstream flow, irradiating at least a portion of the upstream flow with excitation light to allow at least some of the particulate matter to emit scattered light (due to their scattering the excitation light), detecting the scattered light in the upstream flow, irradiating at least a portion of the downstream flow with excitation light to allow at least some of the particulate matter to emit scattered light (due to their scattering the measurement light), detecting the scattered light in the downstream flow, determining the filtration efficiency of the particulate filter body from the differences in the scattered light in the upstream and downstream flows. In embodiments, the particulate matter further comprises non-tracer particles.

[0098] In another aspect, the present disclosure pertains to methods for evaluating the filtration effect of a particulate filter body having an upstream end and a downstream end, the method comprising: introducing an upstream flow comprised of one or more fluids and suspended particulate matter into the upstream end of the particulate filter body, wherein the particulate matter comprises tracer particles and non-tracer particles, trapping at least some of the suspended particulate matter with the particulate filter body, such that a downstream flow exiting the downstream end of the particulate filter body contains less particulate matter than the upstream flow, irradiating at least a portion of the upstream flow with excitation light to allow at least some of the particulate matter to emit scattered light (due to their scattering the excitation light), detecting the scattered light in the upstream flow, irradiating at least a portion of the downstream flow with excitation light to allow at least some of the particulate matter to emit scattered light (due to their scattering the measurement light), detecting the scattered light in the downstream flow, and determining the filtration efficiency of the particulate filter body from the differences in the scattered light in the upstream and downstream flows. In embodiments, the particulate filter body comprises a microstructure which allows at least some of the tracer particles to pass through, and exit the downstream end of, the particulate filter body. The method may further comprise isolating one or more wavelengths of the scattered light from the upstream flow, the downstream flow, or both. In embodiments, one or more isolated wavelengths are detected in the upstream flow, the downstream flow, or both. In embodiments, a bandpass filter isolates one or more wavelengths of the scattered light from the upstream flow, the downstream flow, or both. In embodiments, the scattered light in the upstream flow and in the downstream flow are converted into respective electrical pulses, and the electrical pulses are converted into respective particle counts. In embodiments, the number and/or concentration of the tracer particles in the upstream flow are adjusted to increase the strength and/or quality of the electrical pulse signals derived from light scattered in the upstream flow. In embodiments, the respective particle counts are determined by an optical particle counter; in embodiments, the optical particle counter comprises a bandpass filter which is tuned to isolate the signal of the tracer particles from the schedule light signal from all particles; in embodiments, the optical particle counter comprises a bandpass filter which is tuned to filter out the scattered light signal of the non-tracer particles; in embodiments, the optical particle counter comprises a bandpass filter which is tuned to isolate the scattered light signal of the tracer particles and to filter out the scattered light signal of the non-tracer particles; in embodiments, the optical particle counter comprises a laser light source, one or more collecting lenses, and a photodetector; in embodiments, the optical particle counter comprises a laser light source, one or more collecting lenses, a photodetector, and a bandpass filter which allows scattered light at one or more selected wavelengths to reach the photodetector while preventing scattered light at other wavelengths from reaching the photodetector. In embodiments, the concentration of the tracer particles and/or the aerosol droplet size in the upstream flow is adjusted to maximize the strength and/or quality of the scattered light signal. In embodiments, a filtration efficiency is determined at least in part from the particle counts. In embodiments, the tracer particles emit scattered light in the low visible spectrum. In embodiments, the tracer particles emit scattered light at or near 400 nm. In embodiments, the excitation light is laser light; in embodiments, the laser light produces excitation light in the ultraviolet (UV) range; in embodiments, the laser light produces excitation light at or near 375 nm; in embodiments, the laser light produces excitation light at or near 375 nm. In embodiments, the excitation light is in the ultraviolet (UV) range, and the tracer particles emit scattered light in the low visible spectrum; in embodiments, the excitation light is at or near 375 nm, and the tracer particles emit scattered light at or near 400 nm. In embodiments, the tracer particles are comprised of nano-scale synthetic crystal. In embodiments, the tracer particles are comprised of quantum dots. In embodiments, the tracer particles have a particle size of from 2 nm to 6 nm. In embodiments, Wherein the tracer particles emit scattered light at wavelengths from 2 nm to 6 nm; in embodiments, the tracer particles are quantum dots. In embodiments, the tracer particles emit scattered light at one or more wavelengths selected from the group consisting of 2, 2.5, 3, 5, and 6 nm; in embodiments, the tracer particles are quantum dots. In embodiments, the excitation light irradiating the upstream flow is different from the excitation light irradiating the downstream flow. In embodiments, the excitation light is tuned to one or more respective tracer particle types, such as by selecting a corresponding light source, for example laser source. In embodiments, the tracer particles are injected into an optical particle counter system. In embodiments, the tracer particles are introduced into and suspended within the upstream flow. In embodiments, the tracer particles are aerosolized prior to introduction into the upstream flow. In embodiments, the suspension flow comprises an aerosol flow. In embodiments, the particulate filter body is a plugged honeycomb body. In embodiments, the plugged honeycomb body comprises a honeycomb structure comprised of intersecting porous ceramic walls having wall surfaces that define axial channels, wherein at least some of the axial channels are plugged at the upstream end, and at least some of the axial channels are plugged at the downstream end. In embodiments, the tracer particles comprise submicron tracer particles. In embodiments, the tracer particles are submicron tracer particles. In embodiments, the tracer particles have a particle size of greater than 0.05 pm. In embodiments, the tracer particles have a particle size of greater than 0.10 pm. In embodiments, the tracer particles have a particle size of greater than 0.20 pm. In embodiments, the tracer particles have a particle size of about 0.05 to about 0.3 pm. In embodiments, the tracer particles have a particle size of about 0.1 to about 0.3 pm. In embodiments, the tracer particles have a particle size of about 0.2 to about 0.3 pm. In embodiments, the tracer particles in the upstream flow are present in a concentration of 10 to 900 particles per cubic centimeter. In embodiments, the tracer particles in the upstream flow are present in a concentration of 50 to 500 particles per cubic centimeter. In embodiments, the tracer particles in the upstream flow are present in a concentration of 50 to 250 particles per cubic centimeter. In embodiments, the tracer particles comprise fluorescent particles; in embodiments, the tracer particles comprise fluorescent microspheres. In embodiments, the tracer particles comprise quantum dots; in embodiments, the quantum dots are conveyed to the particulate filter body as aerosol droplets. In embodiments, the depositing comprises deposition by filtration. In embodiments, deposition by filtration comprises bringing a suspension flow of a plurality of particles in one or more fluids into contact with the surface of the porous wall, wherein the one or more fluids passes through the wall, and at least some of the plurality of particles are trapped by the porous wall. In embodiments, the porous wall has an average porosity of 5% to 75%. In embodiments, the porous wall has a surface porosity of 5% to 75%. In embodiments, the porous wall has a median pore size of 5 to 50 micrometers. In embodiments, the porous wall has a median pore size of 5 to 30 micrometers. In embodiments, the porous wall has a median pore size of 10 to 30 micrometers.

[0099] Methods disclosed herein comprise the use of tracer particles with the application of a material such as a filtration material such as an inorganic material such as a ceramic or refractory material or even a porous ceramic or refractory material. In specific embodiments, the filtration material is an aerosol-deposited filtration material. In some preferred embodiments, the filtration material comprises a plurality of inorganic particle agglomerates, wherein the agglomerates are comprised of inorganic, such as ceramic or refractory, material. In some embodiments, the agglomerates are porous, which may allow gas to flow through the agglomerates.

[00100] Aerosol deposition enables deposition of filtration material onto the porous ceramic walls, which can be discrete regions as small as a single agglomerate or larger such as a plurality of agglomerates, and in some embodiments is in the form of a porous layer of filtration material, on or in, or both on and in, at least some surfaces of the walls of the ceramic honeycomb body. In certain embodiments, an advantage of the aerosol deposition method according to one or more embodiments is that ceramic honeycomb bodies with enhanced filtration performance can be produced economically, and/or more efficiently.

[00101] In embodiments, an aerosol deposition process disclosed herein comprises: mixture preparation (e.g., inorganic material, liquid vehicle, and binder), atomizing the mixture with an atomizing gas with a nozzle to form agglomerates and/or aggregates, comprised of the inorganic material, the aqueous vehicle, and the binder if any, drying the agglomerates and/or aggregates in the presence of a carrier gas or a gaseous carrier stream, depositing the aggregates and/or agglomerates onto the honeycomb bodies, and optionally curing the material. In some embodiments, walls of the apparatus can be heated to assist in drying the aggregates and/or agglomerates.

[00102] An example of an apparatus that may be used for processes to deposit inorganic material with binder on ceramic honeycomb bodies which can be used with tracer particles as described herein is shown in FIG. 4. Generally, apparatuses suitable for methods herein include a duct that defines a chamber. The duct may have several sections defining differing spaces and chambers. In one or more embodiments, the droplets and the gaseous carrier stream are conveyed through a duct having an outlet end proximate a plugged honeycomb body. The duct may comprise a converging section for engaging a proximal end of the honeycomb body. A converging section is advantageous in that fluid convection flow is enhanced. The duct may be in sealed fluid communication with the plugged honeycomb body during the depositing step. In one or more embodiments, the duct is adiabatic, or essentially adiabatic. In some embodiments, the nozzle temperature is regulated to achieve favorable atomization.

[00103] FIG. 4 shows an apparatus 500, Apparatus "A", for forming honeycomb bodies, the apparatus 500 comprising a duct 551, a deposition zone 531, an exit zone 536, an exit conduit 540, and a flow driver 545.

[00104] The duct 551 spans from a first end 550 to a second end 555, defining a chamber of the duct comprising: a plenum space 503 at the first end 550 and an evaporation chamber 523 downstream of the plenum space 503. In one or more embodiments, the duct 551 is essentially adiabatic. That is, the duct 551 may have no external sources of heat. The evaporation chamber 523 is defined by an evaporation section 553 of the duct 551, which in this embodiment; comprises a first section of non-uniform diameter 527 and a second section of substantially uniform diameter 529. The evaporation section 553 comprises an inlet end 521 and an outlet end 525. The first section of non-uniform diameter 527 has a diameter that increases from the inlet end 521 toward the section of uniform diameter 529, which creates a diverging space for the flow to occupy.

[00105] A carrier gas is supplied to the duct 551 by a conduit 501, which may have a heat source to create a heated carrier gas 505. An atomizing gas 515 and a suspension 510 are separately supplied by individual delivery conduits such as tubing or piping to a nozzle 520, which is at the inlet end 521 of the evaporation section 553 and is in fluid communication with the duct 551, specifically in this embodiment with the evaporation chamber 523. The suspension 510 is atomized in the nozzle 520 with the atomizing gas 515. In one or more embodiments, the suspension 510 comprises an inorganic material, an aqueous vehicle, and a binder, as defined herein, which as supplied to the nozzle is a liquid-particulate-binder stream. The liquid-particulate-binder stream is atomized with the atomizing gas 515 into liquid- particulate-binder droplets by the nozzle 520.

[00106] In one or more embodiments, the heated carrier gas 505 flows over the nozzle 520. The atomizing gas 515 can be heated to form a heated atomizing gas. Temperature of the nozzle may be regulated as desired.

[00107] Outlet flow from the nozzle 520 and flow of the heated carrier gas 505 are both in a "Z" direction as shown in FIG. 4. There may be a diffusing area 522 downstream of the nozzle where at least some intermixing occurs. In this embodiment, the diffusing area 522 is located in the evaporation chamber 523, but in other embodiments, the diffusing area 522 may be located in the plenum space 503 depending on the location of the nozzle.

[00108] The outlet flow of from the nozzle intermixes with the heated carrier gas 505, thereby forming a gas-liquid-particulate-binder mixture, which flows through the chamber of the duct 551. Specifically, the gas-liquid-particulate-binder mixture flows through the evaporation chamber 523 of the evaporation section 553 and into the deposition zone 531 at the outlet end 525 of the evaporation section 553. At the intermixing, the gas-liquid-particulate-binder mixture is heated inside the chamber by the heated carrier gas.

[00109] In this embodiment, the outlet flow of the nozzle and the heated carrier gas enter the evaporation chamber 523 of the evaporation section 553 from substantially the same direction. In the evaporation chamber 523, substantially all of the aqueous vehicle from the droplets is evaporated thereby forming agglomerates of the particles and the binder material, the agglomerates being interspersed in a gaseous carrier stream, which is comprised of the carrier gas and the atomizing gas.

[00110] The deposition zone 531 in fluid communication with the duct 551 houses a plugged ceramic honeycomb body 530, for example, a wall-flow particulate filter. The deposition zone 531 has an inner diameter that is larger than the outer diameter of the ceramic honeycomb body 530. To avoid leakage of the gases carrying the ceramic powders, the ceramic honeycomb body 530 is sealed to the inner diameter of deposition zone 531, a suitable seal is, for example, an inflatable "inner tube". A pressure gauge, labelled as "PG" measures the difference in the pressure upstream and downstream from the particulate filter.

[00111] The gas-liquid-particulate-binder mixture flows into the ceramic honeycomb body 530 thereby depositing the inorganic material of the suspension on the ceramic honeycomb body.

[00112] Downstream from the ceramic honeycomb body 530 is an exit zone 536 defining an exit chamber 535. The flow driver 545 is downstream from the ceramic honeycomb body 530, in fluid communication with the deposition zone 531 and the exit zone 536 by way of the exit conduit 540. Non-limiting examples of flow drivers are: fan, blower, and vacuum pump. The aerosolized suspension is dried and deposited on one or more walls of the particulate filter as agglomerates of filtration material, which is present as discrete regions of filtration material, or in some portions or some embodiments as a layer, or both, wherein the agglomerates are comprised of primary particles of inorganic material.

[00113] Flow through embodiments such as apparatus 500 is considered in a downward direction, for example, substantially parallel to the direction of gravity. In other embodiments, the apparatus is configured such that flow is directed in a substantially upward or vertical direction.

[00114] Referring now to FIGS. 6 and 7, a filter body which is a plugged honeycomb body of a particulate filter 200 is schematically depicted. The particulate filter 200 may be used as a wall-flow filter to filter particulate matter from an exhaust gas stream 250, such as an exhaust gas stream emitted from a gasoline engine, in which case the particulate filter 200 is a gasoline particulate filter. The particulate filter 200 generally comprises a honeycomb body having a plurality of channels 201 or cells which extend between an inlet end 202 and an outlet end 204, defining an overall length La (shown in FIG. 6). The channels 201 of the particulate filter 200 are formed by, and at least partially defined by a plurality of intersecting channel walls 206 that extend from the inlet end 202 to the outlet end 204. The particulate filter 200 may also include a skin layer 205 surrounding the plurality of channels 201. This skin layer 205 may be extruded during the formation of the channel walls 206 or formed in later processing as an after-applied skin layer, such as by applying a skinning cement to the outer peripheral portion of the channels.

[00115] An axial cross section of the particulate filter 200 of FIG. 5 is shown in FIG. 7. In some embodiments, certain channels are designated as inlet channels 208 and certain other channels are designated as outlet channels 210. In some embodiments of the particulate filter 200, at least a first set of channels may be plugged with plugs 212. Generally, the plugs 212 are arranged proximate the ends (i.e., the inlet end or the outlet end) of the channels 201. The plugs are generally arranged in a pre-defined pattern, such as in the checkerboard pattern shown in FIG. 5, with every other channel being plugged at an end. The inlet channels 208 may be plugged at or near the outlet end 204, and the outlet channels 210 may be plugged at or near the inlet end 202 on channels not corresponding to the inlet channels, as depicted in FIG. 6. Accordingly, each cell may be plugged at or near one end of the particulate filter only. Tracer particles are represented by hollow circles embedded in the walls forming the channels.

[00116] FIG. 5 shows a checkerboard plugging pattern, although alternative plugging patterns may be implemented in the porous ceramic honeycomb article.

[00117] Tracer particles can be used in conjunction with various combinations of process materials. For example, according to one or more embodiments, an aqueous-based suspension of inorganic material and binder passes through a nozzle and provides a flow of aerosol particles after contact with a gas stream and heat before being forced into the opening channels of the honeycomb body. A layer of inorganic material is then deposited on the porous walls with some agglomerates or inorganic material getting into pores. An off-line heat treatment process may be applied for curing of the layer, which in some embodiments forms a membrane. According to one or more embodiments, the honeycomb bodies made and described herein, both before and after curing, exhibit significantly higher filtration efficiency and/or better FE/dP trade-off than bare honeycomb body substrate parts.

[00118] As used herein, the "clean filtration efficiency" of a honeycomb body or filtration article refers to a new or regenerated honeycomb body that does not comprise any measurable soot loading. In embodiments, the clean filtration efficiency of the honeycomb body or filtration article is greater than or equal to 70%, such as greater than or equal to 80%, or greater than or equal to 85%. In yet other embodiments, the initial filtration efficiency of the honeycomb body or filtration article is greater than 90%, such as greater than or equal to 93%, or greater than or equal to 95%, or greater than or equal to 98%.

[00119] Clean filtration efficiency (at 30° C unless otherwise specified) is determined by measuring the difference between a number of particulates that are introduced into the article and a number of particulates that exit the article before and after exposure to the flow conditions.

[00120] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.