Dynamic response of graphene and yttria-stabilized zirconia (YSZ) composites

A series of dynamic compaction studies were performed on yttria-stabilized zirconia (YSZ) and graphene composites using uniaxial flyer plate impact experiments. Studies aimed to characterize variation in dynamic behavior with respect to morphological differences for eight powdered YSZ and graphene compositions. Parameters of interest included YSZ particle size (nanometer or micrometer) and added graphene content (graphene weight percentage: 0%, 1%, 3%, 5%). Experiments were performed over impact velocities ranging between 315 and 586 m/s, resulting in pressures between 0.8 and 2.8 GPa. Hugoniot states measured appear to exhibit dependence on particle size and graphene content. Shock velocities tended to increase with graphene content and were generally larger in magnitude for the micrometer particle size YSZ. Compacted densities tended to increase as graphene content was increased and were generally larger in magnitude for the micrometer particle size YSZ samples. Resulting Hugoniot curves are compared and summarized to convey the dynamic behavior of the specimens.

Advanced anode materials for sodium ion batteries: carbodiimides

ABSTRACTTMNCN (where TM = Mn2+, Fe2+, Co2+ or Ni2+) have been recently proposed as electrochemically active materials for Na-ion insertion that operate via conversion reaction. Their electrochemical performance for Na-ion batteries is presented here with an emphasis on long-term cycling. With a very low voltage for Na insertion of ∼0.1V vs Na+/Na for MnNCN, the overpotential observed in batteries of MnNCN plays a very important role in their performance, evidencing big differences in the electrochemical performance between materials produced with different nano- and micrometer particle sizes evidenced by SEM images. A more suitable voltage for the conversion reaction accompanied by less overpotential is shown by FeNCN, CoNCN and NiNCN. Despite the lower reversible capacity achieved by FeNCN (450 mAh/g) in comparison with CoNCN and NiNCN in the first cycle; the smallest first-cycle irreversible capacity (220 mAh/g) and the lower voltage plateau (0.3 V vs Na+/Na) make FeNCN a good candidate as an anode material for sodium ion batteries. The voltages of conversion reaction are correlated with the calculated enthalpies of formation suggesting that thermodynamics dominates the observed electrochemical conversion reaction.

Assessment on the Collection Efficiency of an Aerosol Sampler in Micro and Nanoparticles Environment

The collection efficiency (CE) of an aerosol sampler is usually assessed dependently by using a sampler with higher CE and higher sampling accuracy or comparing the grain size distribution, concentration and/or other characteristics of the collected dust to that of the original dust, instead of the sampler itself. To establish a simple method for the assessment on the collection efficiency (CE) of an aerosol sampler, a self-dependent method was derived to calculate the CE of an aerosol sampler, which was patented with the number of ZL200910233001.X by the State Intellectual Property Office of China. According to the patent method, two or more uniform aerosol samplers of the same model were connected in series the inlet of a sampler was connected directly with the outlet of another sampler. The CE (η) of the aerosol sampler can be calculated by a simple equation as:η=1-m2/m1, in whichm1andm2is the weight of the aerosol particles collected by sampler 1# and sampler 2# in the connection sequence, respectively. A cascade impactor sampler was used to sample in a micrometer particle (d50=2.5 μm) aerosol environment and a nanoparticle (d50=42 nm) aerosol environment which were formed artificially in a glove box, as well as a workplace environment which manufactured nanometer powders. The sampling test results indicated that the cascade impactor sampler showed relative high CE (99.51%) for micrometer aerosol but a little bit low CE (95.2%) for nanoparticle aerosol. However, a low CE (93.93%) was calculated out by the method because of low concentration aerosol nanoparticles in the workplace environment, which result to big testing errors. It was found that the assessment result on collection efficiency of a sampler is highly affected by the subsequent analytical methods and detection accuracies after the sampling process. If the precision of the electronic balance was improved to a reasonable higher order of magnitude, the cascade impactor sampler can hopefully show much higher collection efficiency on nanoparticle aerosols.

The Research of Nanoparticle and Microparticle Hydroxyapatite Amendment in Multiple Heavy Metals Contaminated Soil Remediation

It was believed that when hydroxyapatite (HAP) was used to remediate heavy metal-contaminated soils, its effectiveness seemed likely to be affected by its particle size. In this study, a pot trial was conducted to evaluate the efficiency of two particle sizes of HAP: nanometer particle size of HAP (nHAP) and micrometer particle size of HAP (mHAP) induced metal immobilization in soils. Both mHAP and nHAP were assessed for their ability to reduce lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr) bioavailability in an artificially metal-contaminated soil. The pakchoi (Brassica chinensisL.) uptake and soil sequential extraction method were used to determine the immobilization and bioavailability of Pb, Zn, Cu, and Cr. The results indicated that both mHAP and nHAP had significant effect on reducing the uptake of Pb, Zn, Cu, and Cr by pakchoi. Furthermore, both mHAP and nHAP were efficient in covering Pb, Zn, Cu, and Cr from nonresidual into residual forms. However, mHAP was superior to nHAP in immobilization of Pb, Zn, Cu, and Cr in metal-contaminated soil and reducing the Pb, Zn, Cu, and Cr utilized by pakchoi. The results suggested that mHAP had the better effect on remediation multiple metal-contaminated soils than nHAP and was more suitable for applying inin situremediation technology.