A new chemical, Peldri II, is evaluated as a compound for drying soft clay materials. Peldri II, a fluorocarbon (1,1-difluorotetrachloroethane), is a solid at room temperature and is a liquid above 25°C. Clay gels are embedded in Peldri II by immersing them in the liquid and allowing it to solidify. Once solidified, Peldri II will sublime, with or without vacuum, to a dry specimen, probably without introducing surface tension. Wyoming montmorillonite saturated in 10−3 M NaCl and 1 M CaCl2 solutions has been examined to compare preservation of its initial structure after Peldri II, critical point, and freeze drying techniques. Transmission electron microscopy of ultrathin sections, scanning electron microscopy, and mercury intrusion porosimetry techniques were used. No differences were detected between Peldri II and critical point drying methods. Peldri II appears to be a significant improvement as an alternative drying agent for clay materials in studies of their structural properties. It is also very convenient for drying large numbers of samples.

Two reference halloysites from New Zealand (Te Puke and Opotiki) were studied by X-ray diffraction under (1) various levels of relative humidity (RH) from 95 to 0% (dehydration), and (2) various temperatures increasing from 25 to 120°C (dehydration). They were also studied by differential thermal and thermogravimetric analyses at 40 and 0.2% RH. The impact of freeze drying along with the influence of cation saturation (Ca and K) on halloysite hydration were studied. The dehydration of the two halloysite samples upon decrease in RH started below 70% RH. However, the dehydration of Opotiki was still incomplete at ∼0% RH regardless of the saturation cation whereas Te Puke was completely dehydrated at ∼10% RH. For each sample, the decrease in RH and the increase in temperature induce similar dehydration behavior, but the dehydration processes of the Opotiki and Te Puke samples are different. The dehydration of Te Puke proceeds with one intermediate hydration state reacting as a separate phase due to the presence of ‘hole’ water molecules. The dehydration of the fully hydrated Opotiki halloysite gives a dehydrated phase and no 8.6 Å phase. The results suggest the presence of different types of water molecule, the ‘associated’ and the ‘hole’ water, controlling the dehydration behavior of halloysites. Freeze-dried halloysite samples are essentially dehydrated and the size of their coherent scattering domains is strongly reduced. Rehydration experiments performed after dehydration either at 95% RH or by immersing the sample in water for 3 months result in their partial rehydration. Calcium saturation promotes the rehydration process. The results suggest the presence of interlayer cations in the Opotiki sample, Ca ions being associated with the strongly held ‘hole’ water. As a result of this study, we assert that the (de)hydration behavior of halloysite is highly heterogeneous and cannot be generalized a priori.

The implantation and controlled release of growth factors can enhance the proliferation and differentiation of cells that promote new bone formation at defect sites. Therefore, chitosan polymer microspheres were prepared by the water-in-oil emulsion (W/O) method and solvent freeze-drying, using glutaraldehyde as an ionic crosslinker, along with the lyophilization of solvents, to microencapsulate growth factors, preventing denaturation. The microspheres were loaded with recombinant bone morphogenetic protein 2 (Rh-BMP-2). They were spherical in shape, with a rough surface ranging in particle size from 0.4 to 1.6 μm. The yield percentage with respect to the polymer was 70% and the BMP-2 load was regulated by the initial protein dose. BMP-2 release experiments were performed for 7 days in PBS solutions at pH 4 and 7.4. The results showed that the protein release rate was only 2% lower at pH 7.4. BMP-2/chitosan microspheres were compatible with the MG-63 cell line (ATCC®CRL-1427™Homo sapiens bone osteosarcoma) and could be considered drug delivery vehicles in bone tissue engineering applications.

Low-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

Macroporous ceramics having unique pore morphologies with ceramic bridges, unidirectional cellular pores, and bamboo-like cells were fabricated by freezing gels with ceramic powder and various gelatin contents. Varying gel strengths were found to be effective for control of the pore architecture from open to closed pore channels. The proposed process is a relatively simple and versatile way to produce tailored pore configurations via a gelation freezing route. In addition, the relationship between the microstructure and mechanical properties of the resulting ceramics was discussed using a multiscale modeling technique, in which a homogenization method was conducted with microscopic models created from three dimensional images, global stress distributions in macroscopic samples by finite element method and local stress distributions. The simulation results were relatively consistent with the experimental results. The multiscale modeling technique was thus confirmed to be a strong tool for the prediction of the mechanical responses of porous ceramics.

In this article, we report on the preparation of few-layered MoS2/graphene nanocomposite (MoS2/GNS-G) with enlarged interlayer distance as the lithium-ion battery anode via a facile hydrothermal method followed by glucose-assisted thermal annealing. During the synthesis, glucose serving as a small organic molecule can interlay into MoS2 nanosheets, which effectively hinder the aggregation and restacking of MoS2 during the process of heat treatment, retaining a sandwich structure of the composite. The enlarged interlayer distance (approximately 0.98 nm), along with the inserted amorphous carbon, could promote efficient lithium migration into active sites, buffer the volume change and stabilize the electrode structure effectively during the lithium insertion/extraction cycling. Electrochemical tests demonstrate that the MoS2/GNS-G delivers a high discharge capacity of 1583.0 mA h/g in the initial cycle at current density of 100 mA/g. The specific capacity remained at the relative high value of 673.5 mA h/g even at a current density of 1000 mA/g.

Evidences show that the composition of β″ formed in age hardening of Al alloys should be the prototype Mg5Si6 with Al and/or Cu addition. In the present work, molecular dynamics simulations are carried out to investigate the influence of the addition of Al and/or Cu to the mechanical properties of the prototype Mg5Si6. Our simulations imply that Mg5Si6 with both Al and Cu addition has relatively poor mechanical performance when compared with other three models. The snapshots of atomic configurations during uniaxial tension test illustrate that only if both Al and Cu dissolve in β″, clusters can form through Al atoms segregating around Cu atoms, thus applying different stress fields on the Al matrix, resulting different mechanical properties in comparison with other three β″ models.

Although the derivation of mice by intracytoplasmic sperm injection (ICSI) using freeze-dried sperm has been demonstrated previously, a comprehensive analysis of their viability, health, and fertility has not. The purpose of the present study was to determine the extent to which ICSI using freeze-dried sperm stored at 4 °C for 1–2 months from mice on either an inbred (C57BL/6J) or hybrid (B6D2F1/J) genetic background results in genomic instability and/or phenotypic abnormality in mice and two generations of their progeny. Fertilization rates (number of 2-cells per injected oocytes) using ICSI of fresh and freeze-dried sperm were similar within and between mouse strains, although fewer freeze-dried sperm-derived embryos than fresh sperm-derived embryos developed to blastocysts in vitro (C57BL/6J and B6D2F1/J) and liveborn pups in vivo (B6D2F1/J only). Nevertheless, once born, mice derived by ICSI using freeze-dried sperm in both mouse strains were healthy and reproductively sound. No major differences in litter size, weaning rate, and sex ratio were noted in the two generations of progeny (F2 and F3) of ICSI-derived offspring using freeze-dried sperm compared with that in the natural mating (control) group. Further, there was no evidence that either ICSI or freeze drying induced genomic instability, as determined by microsatellite analysis of the derived mice and subsequent generations when compared with both parental genotypes, nor were there differences in the number or types of pathological changes in any of the three generations of progeny. We conclude that viable, healthy and genomically stable mice can be derived by ICSI using freeze-dried mouse sperm stored in the refrigerator for at least 2 months. Further, because freeze drying is a simpler and more economical technique compared with embryo and sperm cryopreservation, the results of this study justify additional research to continue to develop and enhance the technique for the preservation, storage, and sharing of genetically altered mice.