Compositional study of Ti-Nb oxide (TiNbO, TiNbO, TiNbO, and TiNbO) anodes for high power Li ion batteries.

Titanium niobium oxides (TNOs) are attractive anode materials for high power density Li-ion batteries. However, the details of capacity storage in TNOs are not fully understood today as it depends on the Ti and Nb composition and their changes in the oxidation state. This is further complicated by a wide variation in gravimetric capacities reported in the literature for TNO anodes.

Measurement of High Carbon Nanotube Growth Rate, Mass Production, Agglomeration, and Length in a Floating Catalyst Chemical Vapor Deposition Reactor.

The growth kinetics of carbon nanotubes (CNTs) and precursor pyrolysis mechanisms within floating catalyst chemical vapor deposition (FCCVD) reactors have remained opaque despite significant interest in the catalytic mechanisms, CNT growth, and aerogel formation. This study utilizes in situ characterization of reactants and CNTs to determine CNT growth kinetics. By modulating precursors, we avoid the formation of a CNT aerogel within the reactor, which enables direct sampling at independent axial locations of single and agglomerated CNTs and catalyst nanoparticles.

Fractal Scaling in the Gas-Phase Agglomeration of Nanowires.

Assembling 1D nanoparticles (nanowires (NW) or nanotubes) as networks enables bridging multiple scales to form macroscopic materials such as fibers, sheets and electrodes. This can be done directly in the gas phase from 1D nanoparticle aerosols grown by floating catalyst chemical vapor deposition (FCCVD). In FCCVD nanowires/nanotubes grow to high aspect ratios (10-10) floating in a gas stream and can agglomerate to form an aerogel.

Gas-Phase Dynamics of Bundle Formation from High-Aspect-Ratio Carbon Nanotubes.

In floating catalyst chemical vapor deposition (FCCVD), high-aspect-ratio carbon nanotubes (CNTs) are produced in the gas phase at high number concentrations and undergo collision and agglomeration, eventually giving rise to a macroscale aerogel, enabling functional material forms such as fibers or mats to be obtained directly from the synthesis process. The self-assembly behavior between high-aspect-ratio CNTs dictates the resulting morphology at the nanoscale and subsequently the bulk properties of the CNT product. Reorientation between CNTs after collision is a critical step that results in bundle formation and precedes aerogel formation.

Charge-Based Separation of Microparticles Using AC Insulator-Based Dielectrophoresis.

Surface charge is an important property of particles. It has been utilized to separate particles in microfluidic devices, where dielectrophoresis (DEP) is often the driving force. However, current DEP-based particle separations based on the charge differences work only for particles of similar sizes.

Synthesis Pathway of Layered-Oxide Cathode Materials for Lithium-Ion Batteries by Spray Pyrolysis.

We report the synthesis of LiCoO (LCO) cathode materials for lithium-ion batteries via aerosol spray pyrolysis, focusing on the effect of synthesis temperatures from 600 to 1000 °C on the materials' structural and morphological features. Utilizing both nitrate and acetate metal precursors, we conducted a comprehensive analysis of material properties through X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Our findings reveal enhanced crystallinity and significant oxide decomposition within the examined temperature range.

Flexible Bifunctional Electrode for Alkaline Water Splitting with Long-Term Stability.

Progress in electrochemical water-splitting devices as future renewable and clean energy systems requires the development of electrodes composed of efficient and earth-abundant bifunctional electrocatalysts. This study reveals a novel flexible and bifunctional electrode () by hybridizing macroscopically assembled carbon nanotube ribbons () and atmospheric plasma-synthesized NiO quantum dots (QDs) with varied loadings to demonstrate bifunctional electrocatalytic activity for stable and efficient overall water-splitting (OWS) applications. Comparative studies on the effect of different electrolytes, e.

Continuous gas-phase synthesis of iron nanoparticles at ambient conditions with controllable size and polydispersity.

Hypothesis: By altering aerosol growth dynamics with unipolar charges, one can obtain aerosols with narrow particles size distributions, a highly desirable feature in applications of functional nanoparticles.

Experiments: Unlike liquid colloid systems, aerosol particles in the free molecular regime undergo coarsening due to Brownian coagulation and will eventually attain a self-preserving size distribution with a typical geometric standard deviation of 1.46 - 1.

Enhanced Visible Light-Driven Photocatalytic Water-Splitting Reaction of Titanate Nanotubes Sensitised with Ru(II) Bipyridyl Complex.

The ion exchange of Na cations was used to photosensitise titanates nanotubes (Ti-NTs) with tris(2,2'-bipyridine)ruthenium(II) cations (Ru(bpy)); this yielded a light-sensitised Ti-NTs composite denoted as (Ru(bpy))Ti-NTs, exhibiting the characteristic absorption of Ru(bpy) in visible light. Incident photon-to-current efficiency (IPCE) measurements and the photocatalytic reduction of methyl viologen reaction confirmed that in the photosensitisation of the (Ru(bpy))Ti-NTs composite, charge transfer and charge separation occur upon excitation by ultraviolet and visible light irradiation. The photocatalytic potential of titanate nanotubes was tested in the water-splitting reaction and the H evolution reaction using a sacrificial agent and showed photocatalytic activity under various light sources, including xenon-mercury lamp, simulated sunlight, and visible light.

Multi-element analysis of tyre rubber for metal tracers.

The purpose of this study was to identify a characteristic elemental tyre fingerprint that can be utilised in atmospheric source apportionment calculations. Currently zinc is widely used as a single element tracer to quantify tyre wear, however several authors have highlighted issues with this approach. To overcome this, tyre rubber tread was digested and has been analysed for 25 elements by ICP-MS to generate a multielement profile.

Simultaneously enhanced tenacity, rupture work, and thermal conductivity of carbon nanotube fibers by raising effective tube portion.

Although individual carbon nanotubes (CNTs) are superior to polymer chains, the mechanical and thermal properties of CNT fibers (CNTFs) remain inferior to synthetic fibers because of the failure of embedding CNTs effectively in superstructures. Conventional techniques resulted in a mild improvement of target properties while degrading others. Here, a double-drawing technique is developed to rearrange the constituent CNTs.

Measuring the Air Quality Using Low-Cost Air Sensors in a Parking Garage at University of Minnesota, USA.

The concentration of air pollutants in underground parking garages has been found to be higher compared to ambient air. Vehicle emissions from cold starts are the main sources of air pollution in underground parking garages. Eight days of measurements, using low-cost air sensors, were conducted at one underground parking garage at the University of Minnesota, Minneapolis.

Towards Portable MEMS Oscillators for Sensing Nanoparticles.

This paper reports on the design, and implementation of piezoelectric-on-silicon MEMS resonators installed within a portable experimental setup for sensing nanoparticles in a laboratory environment. MEMS oscillators with a center frequency of approximately 5.999 MHz are employed for sensing 50 nm size-selected silver nanoparticles generated in the laboratory.

Highly Oriented Direct-Spun Carbon Nanotube Textiles Aligned by In Situ Radio-Frequency Fields.

Carbon nanotubes (CNTs) individually exhibit exceptional physical properties, surpassing state-of-the-art bulk materials, but are used commercially primarily as additives rather than as a standalone macroscopic product. This limited use of bulk CNT materials results from the inability to harness the superb nanoscale properties of individual CNTs into macroscopic materials. CNT alignment within a textile has been proven as a critical contributor to narrow this gap.

Source terms for benchmarking models of SARS-CoV-2 transmission via aerosols and droplets.

There is ongoing and rapid advancement in approaches to modelling the fate of exhaled particles in different environments relevant to disease transmission. It is important that models are verified by comparison with each other using a common set of input parameters to ensure that model differences can be interpreted in terms of model physics rather than unspecified differences in model input parameters. In this paper, we define parameters necessary for such benchmarking of models of airborne particles exhaled by humans and transported in the environment during breathing and speaking.

Utah Wintertime Measurements of Heavy-Duty Vehicle Nitrogen Oxide Emission Factors.

There have only been a few wintertime studies of heavy-duty vehicle (HDV) NO emissions in the United States, and while they have observed increased emissions, fleet characterization to identify the cause has been lacking. We have collected wintertime measurements of NO emission factors from 1591 HDVs at a Utah Port of Entry in December 2020 that includes individual vehicle identification. In general, NO emission factors for 2011 and newer chassis model year HDV are significantly higher than those for 2017 spring measurements from California.

Surfactant-free synthesis of copper nanoparticles and gas phase integration in CNT-composite materials.

Copper nanoparticles (Cu-NPs) represent a viable low-cost alternative to replace bulk copper or other more expensive NPs ( gold or silver) in various applications such as electronics for electrical contact materials or high conductivity materials. This study deals with the synthesis of well dispersed Cu-NPs by using an Ar + H microplasma using a solid copper precursor. The morphological analysis is carried out by electron microscopy showing particles with a mean diameter of 8 nm.

High-precision solid catalysts for investigation of carbon nanotube synthesis and structure.

The direct growth of single-walled carbon nanotubes (SWCNTs) with narrow chiral distribution remains elusive despite substantial benefits in properties and applications. Nanoparticle catalysts are vital for SWCNT and more generally nanomaterial synthesis, but understanding their effect is limited. Solid catalysts show promise in achieving chirality-controlled growth, but poor size control and synthesis efficiency hampers advancement.

Weakly Coupled Piezoelectric MEMS Resonators for Aerosol Sensing.

This paper successfully demonstrates the potential of weakly coupled piezoelectric MEMS (Micro-Electro-Mechanical Systems) gravimetric sensors for the detection of ultra-fine particulates. As a proof-of-principle, the detection of diesel soot particles of 100 nanometres or less is demonstrated. A practical monitoring context also exists for diesel soot particles originating from combustion engines, as they are of serious health concern.

Comprehensive characterization of mainstream marijuana and tobacco smoke.

Recent increases in marijuana use and legalization without adequate knowledge of the risks necessitate the characterization of the billions of nanoparticles contained in each puff of smoke. Tobacco smoke offers a benchmark given that it has been extensively studied. Tobacco and marijuana smoke particles are quantitatively similar in volatility, shape, density and number concentration, albeit with differences in size, total mass and chemical composition.

Plasma production of nanomaterials for energy storage: continuous gas-phase synthesis of metal oxide CNT materials via a microwave plasma.

In this work we show for the first time that a continuous plasma process can synthesize materials from bulk industrial powders to produce hierarchical structures for energy storage applications. The plasma production process's unique advantages are that it is fast, inexpensive, and scalable due to its high energy density that enables low-cost precursors. The synthesized hierarchical material is comprised of iron oxide and aluminum oxide aggregate particles and carbon nanotubes grown in situ from the iron particles.

A Simple Method for Measuring Fine-to-Ultrafine Aerosols Using Bipolar Charge Equilibrium.

Low-cost methods for measuring airborne microparticles and nanoparticles (aerosols) have remained elusive despite the increasing concern of health impacts from ambient, urban, and indoor sources. While bipolar ion sources are common in smoke alarms, this work is the first to exploit the mean charge on an aerosol resulting from a bipolar charge equilibrium and establish experimentally its correlation to properties of the aerosol particle size distribution. The net current produced from this mean particle charge is demonstrated to be linearly proportional to the product of the mean particle diameter and total number concentration ( ∼ ) for two bipolar ion sources (Kr and Am).

Continuous-Flow Synthesis of Carbon-Coated Silicon/Iron Silicide Secondary Particles for Li-Ion Batteries.

The development of better Li-ion battery (LIB) electrodes requires an orchestrated effort to improve the active materials as well as the electron and ion transport in the electrode. In this paper, iron silicide is studied as an anode material for LIBs because of its higher conductivity and lower volume expansion compared to pure Si particles. In addition, carbon nanotubes (CNTs) can be synthesized from the surface of iron-silicides using a continuous flow coating process where precursors are first spray dried into micrometer-scale secondary particles and are then flown through a chemical vapor deposition (CVD) reactor.

Agglomeration Dynamics of 1D Materials: Gas-Phase Collision Rates of Nanotubes and Nanorods.

The agglomeration and self-assembly of gas-phase 1D materials in anthropogenic and natural systems dictate their resulting nanoscale morphology, multiscale hierarchy, and ultimate macroscale properties. Brownian motion induces collisions, upon which 1D materials often restructure to form bundles and can lead to aerogels. Herein, the first results of collision rates for 1D nanomaterials undergoing thermal transport are presented.