State of the art of geopolymers: A review

Geopolymers emerge as an ecological alternative for construction materials. These consist of a mixture of aluminosilicate sources and an alkaline solution that dissolves the silicon and aluminum monomers that come from the source to generate a gel called N–A–S–H that will control the main properties of the geopolymer. The geopolymer stands out for having good resistance to compression, as well as good resistance to high temperatures and corrosive environments. They have great potential as a replacement for classical technologies such as concrete, however, require further applied research to determine their feasibility on an industrial scale.

Utilization of Greenhouse Gases for Syngas Production by Dry Reforming Process Using Reduced BaNiO3 Perovskite as a Catalyst

For the commercialization of syngas production, the utilization of greenhouse gases and the fabrication of an active catalyst for the dry reforming methane (DRM) process are the biggest challenges because of deactivation by carbon deposition, oxidation, sintering, and loss of active surface sites under high temperature. In the present article, BaNiO3 perovskite was synthesized by the coprecipitation method, and its reduced form (r-BNO) was utilized for syngas production by the DRM reaction. It was found that the r-BNO showed high stability and good resistance against carbon deposition, however, the conversions (CH4 and CO2) have been found to be less than 50%. Many techniques such as TGA, XRD, FT-IR, UV-Vis, BET, SEM, TEM, XPS, TPR, TPO, and TPD were used in order to investigate the physical properties and evaluation conditions for syngas production. From the obtained results, it was revealed that BaNiO3 perovskite possessed a hexagonal crystal structure and perforated–rough surface; in addition, its structure was virtually regenerated by oxidation of the r-BNO catalyst, which provides a convenient way to regenerate the original catalyst in an oxidative atmosphere. Structural and surface alterations of the used catalyst, after the DRM reaction, were characterized by using TGA, TPO, and TEM, and it was found that there was no significant deposition of inert carbons (D and G) and deactivation of the r-BNO catalyst.

NEW BEARING STEEL FOR HIGH-SPEED APPLICATIONS

The requirements for speed suitability and fatigue strength of motor spindle bearings are constantly increasing. These challenges can be met by further developing the spindle bearings, e.g. by using higher-performance bearing steels. In the following, the experimental investigation results of a spindle bearing made of a new raceway steel tested on a high-speed rolling bearing test rig are presented. Spindle bearings of the type 7008 (hybrid execution) were tested in an endurance run at a rotational speed of 46 krpm and 3 kN axial load. The operating behaviour was validated based on the bearing outer ring temperature and the vibration behaviour. Microscope analysis of the raceways after the test shows that the new steel has good resistance to micropitting and surface fatigue. The calculated contact pressures, wear parameter and lifetime for the bearings in the tests show that the performance limits of spindle bearings are significantly higher than initially assumed.

Determination of the physical-mechanical properties of a permeable block

This study aims to analyze the influence of the incorporation of crushed polyethylene terephthalate as a substitute for fine aggregate in percentages of 10%, 15%, and 20% for the elaboration of concrete blocks. The methodology used is experimental quantitative approach, where the influence of the addition of crushed polyethylene terephthalate as a substitute for fine aggregate for the elaboration of concrete blocks was analyzed to identify the variation in the physical and mechanical properties of samples elaborated under different substitutions and in this way compare with the Colombian standard procedures. The results found in this study indicated that the blocks with the different percentages of polyethylene terephthalate presented a good resistance compared to the block without polyethylene terephthalate, which presented a resistance of 8 MPa. The blocks with polyethylene terephthalate at 10%, 15%, and 20% presented an average resistance of 6.36 MPa, 3.58 MPa, and 4.63 MPa, respectively. Finally, it was analyzed that the blocks with 10% aggregate are waterproof with normal density. In comparison, the blocks with 15% and 20% polyethylene terephthalate have high permeability, with the ability to drain 1 liter of water in 105 s and 38 s, respectively.

Fermentation of Lulo Juice with Lactobacillus reuteri CECT 925. Properties and Effect of High Homogenization Pressures on Resistance to In Vitro Gastrointestinal Digestion

The aim of this study was to evaluate the use of lulo juice as substrate for producing a potentially probiotic beverage with Lactobacillus reuteri CECT 925. Lulo juices at two pH levels and two levels of HPH treatment have been considered to evaluate the effect of these variables on Lactobacillus reuteri CECT 925 growth, physicochemical and antioxidant properties, and the resistance of microbial cells to gastrointestinal digestion in vitro. Regarding the growth of Lactobacillus reuteri CECT 925, it was mainly affected by the pH of the medium, the rectified juice at pH 5.5 being the most appropriated one. The growth of Lactobacillus reuteri CECT 925 mainly increased the antiradical capacity of the juices. In general, Lactobacillus reuteri CECT 925 showed good resistance to in vitro gastrointestinal digestion conditions, reaching levels above 107 CFU/mL in all cases. The highest resistance was observed in the juice treated at 150 MPa followed by the juice homogenized at 100 MPa.

Experimental Study on Solidification of Pb2+ in Fly Ash-Based Geopolymers

Fly ash from the incineration of domestic waste contains heavy metals, which is harmful to the environment. To reduce and prevent their contamination, heavy metal ions need to be sequestered. In this study, the geopolymer prepared by fly ash, a kind of power plant waste, is used to cure the heavy metal Pb2+, and to investigate the effect of different concentrations of Pb2+ on the compressive strength of the solidified body at different ages; the curing effect is judged by the toxic leaching concentration of heavy metals; the resistance of the solidified body to immersion is evaluated by comparing the change in strength before and after leaching; the fly ash-based geopolymer solidified body is compared with the cement solidified body in terms of curing effectiveness; the properties of the geopolymer and its mechanism of curing heavy metals are explored by microscopic tests. The results show that the fly ash-based geopolymer solidified body has good resistance to immersion; the optimum curing concentration of Pb2+ in fly ash-based geopolymers is 2.0%; compared to pure geopolymers, the strength of the solidified body at 28 d decreases by only 13.0%, and the leaching concentration of Pb2+ is 4.73 mg·L−1, which meets the specification requirements; the curing effect of the fly ash-based geopolymer is better than the cement solidified body; the microscopic test results indicate that the curing of Pb2+ by the fly ash-based geopolymer is a combination of both chemical bonding and physical fixation.

Evaluation of anthocyanin corn under various agro-environment in Indonesia

In the last decade, purple corn gain more attention mainly due to its high nutritional value and attractive color appearance. Purple corn contain anthocyanin 350% higher than normal corn. Based on its excellence, the research was conducted to find out of high yield purple opv corn with good resistance to downy mildew. The experiment was conducted by using randomized block design with three replication. The variable observed including agronomic character like vegetative, generative and scored disease of downy meldows. The result showed that two opve candidate were PMU(S1).Synth.F.C1 and PMU(S1).Synth.D.C1 have the highest yield6,80-6,85 t/ha, higher 50% than PLU. C0 (check). PMU(S1).Synth.F.C1 showed moderate resistence to downy meldows (20%-35%) and PMU(S1).Synth.D.C1 susceptible (>60%).

Thermoplastic sago starch nanocomposites wound dressing fortified with antibiotic-modified HNT

Starches were reported to promote wound healing. However, the hydrophilicity of starch help absorbs the exudates from the wounds during the healing process, but it also enables a bacterial infection that slows the healing process. Halloysite nanotubes (HNT) are attracting many biological technologies because of their high loading capacity and biocompatibility. This paper investigates the modified HNT as a carrier for antimicrobials agent in wound healing materials. Halloysite was modified by dispersing it with chloramphenicol solution using a magnetic stirring method. Thermoplastic sago Starch (TPSS)/modified HNT (MHNTs) biocomposite films of different compositions (0.25, 0.5, 0.75 and 1 wt. % HNT) were then developed using the solution casting method. SEM revealed that modified HNT shows good dispersion on the TPSS matrix. With the introduction of modified HNT, the FTIR peaks of TPSS have altered at the peak of 3693.21 cm-1 and 1040.05 cm-1. In addition, modified HNT reduced the water absorption rate of the TPSS films. Furthermore, modified HNT showed good resistance to bacterial culture and significantly reduced the biodegradability rate of TPSS compared to pristine HNT. From the findings, HNT can be a potential carrier for antibacterial agents to withstand bacterial attacks.

Compensation Gyrocompass Based on MEMS

The study of an astatic compensating gyrocompass, built on the basis of a modulation micromechanical gyroscope (MMG) of a hybrid type, has been carried out. A kinematic diagram is given and the principle of operation of the device has describing. The device uses the modulation principle based on obtaining information about the angular motion of the rotor and creating control torques in a rotating coordinate system, which makes it possible to exclude such a significant disadvantage of MMG as "zero offset". A feature of the gyrocompass under consideration is the use of two channels for controlling the rotor of the MMG, namely: a channel for the formation of a guiding moment, striving to combine its main axis with the direction of the true meridian and a channel for compensating this guiding moment. A linearized mathematical model has building, on the base of which an effective algorithm for the operation of a compensatory astatic gyrocompass is proposed. The device under consideration can be used to determine the true azimuth of the longitudinal axis of a mobile ground object, it has a higher measurement speed compared to devices built on three-degree "heavy" gyroscopes, and has good resistance to external influences (vibrations, shocks, etc.).

Recent Advances in Copper Polycrystal Film’s Grain Boundaries Behavior and Its Influence in Properties with Molecular Dynamic Simulation

Abstract.Copper polycrystal film(CPF) is accepted as a promising material for electroplated film in semiconductor devices for its outstanding conductivity and ductility as well as the good resistance to elector-migration. However, the film material attains a rapid failure in the working environment, and hence the failure mechanism and the fabrication methods require more exploration. In previous studies, it is convinced that grain boundaries(GBs) movement and its interaction with twining boundaries(TBs) and dislocations have a great influence on the failure process. In this study, the applications of Molecular Dynamic(MD) Simulation in the research of CPF have been introduced. The GBs behaviour including deformation of the GBs and the interaction between GBs and TBs that is observed by dislocation extraction algorithm(DXA) has been summarized, and its relation to the properties such as yield strength and the roughness of growth has been discussed. And the best condition to construct a CPF with magnetron sputtering method is concluded to have substrates in 700K as well as low misorientation with grains under incident atoms of large enough kinetic energy and vertical incident angle.