Microstructure and mechanical properties of Mg-3Sn-1Ca reinforced with AlN nano-particles

Microstructural evolution and strengthening mechanisms of Mg-3Sn-1Ca based alloys with additions of different amounts of Al N nanoparticles were investigated.It was found that with increasing the amount of AlN nano-particles the grain size decreases obviously.The existence of AlN nano-particles could refine the primary crystal phases CaMgSn,which provided more heterogeneous nucleation sites for the formation of magnesium.Moreover,such nano-particles could also restrict the grain growth during solidification.After adding AlN nano-particles,both the tensile properties at room temperature and high temperature 250℃and the hardness are largely improved.The improvement of strength is attributed to grain refinement and second phase refinement.

Silica nanoparticle design for colorectal cancer treatment:Recent progress and clinical potential

Colorectal cancer(CRC)is the third most common cancer worldwide and the second most common cause of cancer death.Nanotherapies are able to selectively target the delivery of cancer therapeutics,thus improving overall antitumor eff-iciency and reducing conventional chemotherapy side effects.Mesoporous silica nanoparticles(MSNs)have attracted the attention of many researchers due to their remarkable advantages and biosafety.We offer insights into the recent advances of MSNs in CRC treatment and their potential clinical application value.

Gypsum-based Silica Gel Humidity-controlling Composite Materials:Preparation,Characterization,and Performance

Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.

New Data on Coal, Gypsum, Iron and Silica Sand Deposits and Geochemical Exploration (Pakistan): Revision of 25 Years History of Dinosaur Discoveries from Pakistan

Discoveries of many coal seams at depths by drilling carried by Geological Survey of Pakistan in Sor Range and Harnai Gochina, extended the coal seams at depth which is challenge for mine owners to exploit feasibly. Bed to bed gypsum samplings (and their chemical analyses) of huge gypsum deposits from Sulaiman foldbelt is a base for industrialist and also planers to develop cement and gypsum industries to increase export and foreign exchange for the development of area and Pakistan. Low and high grade sedimentary iron deposits, silica sand and uranium host rocks and their extensions in Sulaiman and Kirthar foldbelts are presented. Anomalies of a few base metals arise as a result of geochemical exploration carried at part of Loralai District of Balochistan. Theropod dinosaurs were frequent in India, while Poripuchian titanosaurs (Sauropoda, Dinosauria) were frequent in Pakistan. Besides some ichnotaxa, many bone taxa such as 1 titanosauriform, 14 titanosaurian sauropod (including one new titanosaur), and 3 theropod dinosaurs are established from Pakistan. Among these 12 titanosaur species and 3 theropod species are named in about 10 km2 area of Vitakri dome and 2 titanosaur species are named in about a few hundred square meter area of Mari Bohri (Kachi Bohri) which is about 10 km westward from Vitakri dome. Pakistan is a unique country which discoverd 14 diversified titanosaurs in a short area and also in a short period (67 - 66 million years ago/Ma). About 400 bones found from a few meter thick upper part of upper shale horizon of latest Maastrichtian Vitakri Formation which is base for titanosaur taxa. Cranial material is in low fraction (but include significant diverse snouts), caudal vertebrae are prominent, the cervicals, dorsals and sacrals have significant numbers, forelimb and hind limb bones have balanced fraction. Humeri, femora and tibiae are most common. To know the position of Pakistani titanosaurs among titanosaurs and sauropods, there is a need to extend list of characters for phylogenetic analyses. This broad feature list should include main characters of titanosaurs from Pakistan and also from global world.

Green synthesis of ZSM-5 using silica fume and catalytic co-cracking of lignin and plastics for production of monocyclic aromatics

ZSM-5 with hierarchical pore structure was synthesized by a simple two-step hydrothermal crystallization from silica fume without using any organic ammonium templates.The synthesized ZSM-5 were oval shaped particles with a particle size about 2.0 μm and weak acid-dominated with proper Brønsted(B)and Lewis(L)acid sites.The ZSM-5 was used for catalytic co-cracking of n-octane and guaiacol,lowdensity polyethylene(LDPE)and alkali lignin(AL)to enhance the production of benzene,toluene,ethylbenzene and xylene(BTEX).The most significant synergistic effect occurred at n-octane/guaiacol at 1:1 and LDPE/AL at 1:3,under the condition,the achieved BTEX selectivity were 24%and 33%(mass)higher than the calculated values(weighted average).The highest BTEX selectivity reached 88.5%,which was 3.7%and 54.2%higher than those from individual cracking LDPE and AL.The synthesized ZSM-5 exhibited superior catalytic performance compared to the commercial ZSM-5,indicating potential application prospect.

Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene:Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles(YP)with center-radial meso-channels were fabricated through a simple and effective method.Al-containing YP-supported NiMo catalysts with different Al amounts(NiMo/AYP-x,x=Si/Al molar proportion)were prepared and dibenzothiophene(DBT)and 4,6-dimethyl-dibenzothiophene(4,6-DMDBT)were employed as the probes to evaluate the hydrodesulfurization(HDS)catalytic performance.The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance.The average pore sizes of series AYP-x supports are above 6.0 nm,which favors the mass transfer of organic sulfides.The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals.Aluminum embedded into the silica framework could facilitate the formation of Lewis(L)and Brønsted(B)acid sites and adjust the metal-support interaction(MSI).Among all the as-synthesized catalysts,NiMo/AYP-20 catalyst shows the highest HDS activities.The improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica,enhanced acidity,moderate MSI,and good accessibility/dispersion of active components.

Residual stress modeling of mitigated fused silica damage sites with CO_(2)laser annealing

A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO_(2)laser-annealed mitigated fused silica damage sites.The proposed model extracts the residual strain from the differences in thermoelastic contraction of fused silica with different fictive temperatures from the initial frozen-in temperatures to ambient temperature.The residual stress fields of mitigated damage sites for the CO_(2)laser-annealed case are obtained by a finite element analysis of equilibrium equations and constitutive equations.The simulated results indicate that the proposed model can accurately evaluate the residual stress fields of laser-annealed mitigated damage sites with a complex thermal history.The calculated maximum hoop stress is in good agreement with the reported experimental result.The estimated optical retardance profiles from the calculated radial and hoop stress fields are consistent with the photoelastic measurements.These results provide sufficient evidence to demonstrate the suitability of the proposed model for describing the residual stresses of mitigated fused silica damage sites after CO_(2)laser annealing.

Effect of Sodium Tripolyphosphate and Silica Fume on Hydration of High Alumina Cement

It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.

Silica-modified Pt/TiO_(2) catalysts with tunable suppression of strong metal-support interaction for cinnamaldehyde hydrogenation

Tuning Strong Metal-support Interactions(SMSI)is a key strategy to obtain highly active catalysts,but conventional methods usually enable TiO_(x) encapsulation of noble metal components to minimize the exposure of noble metals.This study demonstrates a catalyst preparation method to modulate a weak encapsulation of Pt metal nanoparticles(NPs)with the supported TiO_(2),achieving the moderate suppression of SMSI effects.The introduction of silica inhibits this encapsulation,as reflected in the characterization results such as XPS and HRTEM,while the Ti^(4+) to Ti^(3+) conversion due to SMSI can still be found on the support surface.Furthermore,the hydrogenation of cinnamaldehyde(CAL)as a probe reaction revealed that once this encapsulation behavior was suppressed,the adsorption capacity of the catalyst for small molecules like H_(2) and CO was enhanced,which thereby improved the catalytic activity and facilitated the hydrogenation of CAL.Meanwhile,the introduction of SiO_(2) also changed the surface structure of the catalyst,which inhibited the occurrence of the acetal reaction and improved the conversion efficiency of C=O and C=C hydrogenation.Systematic manipulation of SMSI formation and its consequence on the performance in catalytic hydrogenation reactions are discussed.

Theoretical study on the effective thermal conductivity of silica aerogels based on a cross-aligned and cubic pore model

Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, making them a new type of lightweight and highly efficient nanoscale super-insulating material. However, prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution. To investigate the internal heat transfer mechanism of aerogel nanoporous materials, this study constructed a cross-aligned and cubic pore model(CACPM) based on the actual pore arrangement of SiO_(2) aerogel. Based on the established CACPM, the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction, solid-phase heat conduction, and radiative heat transfer. The derived expression was then compared with available experimental data and the Wei structure model. The results indicate that, according to the model established in this study for the derived thermal conductivity formula of silica aerogel, for powdery silica aerogel under the conditions of T = 298 K, a_(2)= 0.85, D_(1)= 90 μm, ρ = 128 kg/m^(3), within the pressure range of 0–10^(5)Pa, the average deviation between the calculated values and experimental values is 10.51%. In the pressure range of 10^(3)–10^(4)Pa, the deviation between calculated values and experimental values is within 4%. Under these conditions, the model has certain reference value in engineering verification. This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.

The Capture and Catalytic Conversion of CO_(2) by Dendritic Mesoporous Silica-Based Nanoparticles

Dendritic mesoporous silica nanoparticles own three-dimensional center-radial channels and hierarchical pores,which endows themselves with super-high specific surface area,extremely large pore volumes,especially accessible internal spaces,and so forth.Dissimilar guest species(such as organic groups or metal nanoparticles)could be readily decorated onto the interfaces of the channels and pores,realizing the functionalization of dendritic mesoporous silica nanoparticles for targeted applications.As adsorbents and catalysts,dendritic mesoporous silica nanoparticles-based materials have experienced nonignorable development in CO_(2)capture and catalytic conversion.This comprehensive review provides a critical survey on this pregnant subject,summarizing the designed construction of novel dendritic mesoporous silica nanoparticles-based materials,the involved chemical reactions(such as CO_(2)methanation,dry reforming of CH_(4)),the value-added chemicals from CO_(2)(such as cyclic carbonates,2-oxazolidinones,quinazoline-2,4(1H,3H)-diones),and so on.The adsorptive and catalytic performances have been compared with traditional silica mesoporous materials(such as SBA-15 or MCM-41),and the corresponding reaction mechanisms have been thoroughly revealed.It is sincerely expected that the in-depth discussion could give materials scientists certain inspiration to design brand-new dendritic mesoporous silica nanoparticles-based materials with superior capabilities towards CO_(2)capture,utilization,and storage.

The Influence of Carbon Nanotubes and Nano-Silica Fume on Enhancing the Damping and Mechanical Properties of Cement-Based Materials

This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.

Surface Effect of Silica Nano-Particles with Different Size on Thermotropic Liquid Crystalline Polyester Composites

Interface properties of nano-silica/thermotropic liquid crystalline polyesters (TLCP) composites were investigated by X-ray diffraction analysis and differential scanning calorimetory. The crystallinity of TLCP in the composites drastically decreased with an increase of nano-silica content, depending on the surface area of the silica particles. Little size effects (40 - 400 nm) in the particles and strong interaction between silica surface and the C=O moieties of TLCP were observed by IR analysis. The glass transition temperature of TLCP (。C higher than that in bulk.

High temperature frictional wear behaviors of nano-particle reinforced NiCoCrAlY cladded coatings

The NiCoCrAlY coatings strengthened by three nano-particles with the same addition were prepared on a Ni-base super alloy using laser cladding technique. The dry frictional wear behaviors of the coatings at 500 ℃ in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the wear mechanism of the NiCoCrAlY coatings with nano-particles, like the coating without nano-particles, is the delamination wear due to the strong plastic deformation and oxidative wear. However, the frictional coefficient of the coatings increases and presents the decrease trend with the increase of sliding distance after adding nano-particles. Moreover, the wear rate of the coatings with nano-particles is only 34.0%-64.5% of the coating without nano-particles. Among the three nano-particles, the improvement of nano-SiC on the high temperature wear resistance of the coating is the most significant.

Microstructure and Oxidation Behaviors of Nano-particles Strengthened NiCoCrAlY Cladded Coatings on Superalloys

Nano-particles which can largely improve the microstructure and oxidation resistance of materials are often used as a strengthening component in metal matrix composites. However, few studies were reported on its application in the bond coat of duplex structure thermal barrier coating（TBC）. Three kinds of NiCoCrAlY coatings strengthened by different nano-particles with the same addition （1%, mass fraction） were prepared by the laser cladding technique on Ni-based superalloy substrates, aiming to study the effects of the nano-particles on microstructure and oxidation resistance of NiCoCrAlY coatings （the bond coat of the duplex structure thermal barrier coatings）. Scanning electron microscope （SEM）, X-ray diffractometer（XRD） and thermogravimetry were employed to investigate their morphologies, phases and cyclic oxidation behaviors in atmosphere at 1 050℃, compared with the coating without nano-particles. With the addition of nano-particles, the growth pattern of the grains at the interface changed from epitaxial growth to non-epitaxial growth or part-epitaxial growth; slender dendrites were broken and cellularized; cracks and pores were restrained; and the oxidation weight-gain and the stripping resistance of the oxide scale were improved as well. Among the three kinds of nano-particles, the SiC nano-particles showed the most improvement on microstructure, while the CeO2 nano-particles were insufficient, but its effects on the oxidation resistance are the same as those of the SiC nano-particles. Based on the discussions of the influence mechanism, it is believed that CeO2 nano-particles would show better improvement than SiC nano-particles if the proper amount is added and the proper preparation technique of micro-nanometer composite powders is adopted, with the synergistic action of nanometer effect and reactive element effect.

Effect of nano-particle size on product distribution and kinetic parameters of Fe/Cu/La catalyst in Fischer-Tropsch synthesis

Effects of nano-particle size on hydrocarbon production rates and distributions for precipitated Fe/Cu/La catalysts in Fischer-Tropsch synthesis were investigated.Nano-structured iron catalyst was prepared by micro-emulsion method.The concept of two superimposed AndersonSchulz-Flory （ASF） distributions has been applied for the representation of the effects of reaction conditions and nano-particles size on kinetics parameters and product distributions.These results reveal that by reducing the particle size of catalyst,the break in ASF distributions was decreased.Also useful different kinetics equations for synthesis of C3 to C9 and C10 to C22 were determined by using α1 and α2 chain growth probabilities.

Surface tension of lithium bromide aqueous solution/ammonia with additives and nano-particles

In order to investigate the effect of additives and nano-particle on the surface tensions of lithium bromide(Li Br) aqueous solution/ammonia, many experiments were carried out based on Wilhelmy plate method. Firstly, the surface tension of Li Br aqueous solution with 1-octanol was measured and then the comparison between the measured results and previous experimental results was given to verify the measuring accuracy. Some new additives, such as cationic surfactants cetyltrimethyl ammonium chloride(CTAC), and cetyltrimethyl ammonium bromide(CTAB) were chosen in the experiments. The experimental results show that CTAC and CTAB can obviously reduce the surface tension of Li Br aqueous solution/ammonia. In addition, it is found that nano-particles cannot remarkably decrease the surface tension of Li Br aqueous solution/ammonia. However, the mixed addition of additives and nano-particles can remarkably affect the surface tension of Li Br aqueous solution/ammonia. That is to say, additives play more important role in reducing the surface tension of Li Br aqueous solution/ammonia. But nano-particles may enhance the heat transfer in the absorption refrigeration process.

Influence of SiO_2 nano-particles on microstructures and properties of Ni-W-P/CeO_2-SiO_2 composites prepared by pulse electrodeposition

Ni-W-P base composites containing CeO2 and SiO2 nano-particles were prepared on common carbon steel surface by pulse co-deposition of Ni,W,P,CeO2 and SiO2 nano-particles.The influence of SiO2 concentrations in bath on microstructures and properties of Ni-W-P/CeO2-SiO2 composites was studied,and the characteristics were assessed by chemical compositions,element distribution,surface morphologies,deposition rate and microhardness.The results indicate that when SiO2 concentration in bath is controlled at 20 g/L,the composites possess the fastest deposition rate,the highest microhardness,compact microstructures,smaller crystallite sizes and uniform distribution of W,P,Ce and Si within Ni-W-P matrix metal.Increasing SiO2 concentration in bath from 10 to 20 g/L leads to the refinement in grain size and the inhomogeneity of microstructures.While when SiO2 concentration is increased to 30 g/L,the crystallite sizes increase again and some bosses with nodulation shape appear on the surface of composites.

Preparation and Characterization of Fe3O4 Magnetic Nano-particles by ^（60）Co γ-ray Irradiation

By using a new method, ^60Co γ-ray irradiation, Fe3O4 magnetic nano-particles were successfully synthesized at room temperature under ambient pressure. The structure, morphology and magnetic properties of these nanoparticles were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM） and vibrating sample magnetometer （VSM）, respectively. The radiation formation mechanism was also discussed. The results show that the absorbed dose can greatly influence the structure, morphology and magnetic properties of the products. XRD and TEM studies show that the product prepared by γ-ray irradiation （10 kGy） is pure FesO4 phase and the mean diameter of these nano-particles is about 21 nm. The Fe3O4 nano-particles synthesized by γ-ray irradiation （10 kGy） are mainly in small cubic shape and the size uniformity of these particles is good.

Pressure-Induced Structural Transitions of the Zinc Sulfide Nano-particles with Different Sizes

ZnS nano-particles with average sizes of 10 nm and 5 nm were fabricated by sol-gel method, and their pressure-induced phase transformations were in-situ examined in a diamond anvil cell by energy dispersive X-ray diffraction （EDXD） from ambient pressure to 35.0 GPa. From the obtained interplanar spacing data,the volume compression ratios were derived at different pressures, and then the bulk modulus and its pressure derivative were obtained by fitting to the Murnaghan equation. It is found that both ZnS nano-particles initially in the zinc-blende phase transformed to cubic NaCl structure in the presence of pressure and the transition was reversible when the pressure was released. Moreover, it is suggested that a smaller particle size will induce a larger transition pressure.