Different routes, including the replacements of the template, addition of pore expander and hydrothermal post-synthesis treatment have been used for the pore engineering of spherical MCM-41. A comparison among the pore engineering effects of these methods has been made. The results show that the hydrothermal post-synthesis treatment affords the synthesized material with a larger pore size and narrow pore size distribution without changing the spherical morphology. As far as the pore-size expansion is concerned, the addition of DMTA is the most effective one, but this might be limited by the spherical, morphology. Combining the replacement of C16 TMABr with the Gemini surfactant GEM 16-8-16 with an addition of DMTA gives rise to the largest pore volume and surface area.
The discrete variational Xa method (DV-Xα) within the framework of density-functional theory was applied to study O2 molecule adsorption on NiTi (100) and (110) surfaces. The bond order and charge distribution between Ti and O atoms for two possible O2 molecule adsorption ways on NiTi (100) and (110) surfaces were calculated. It is found that the adsorption way for O−O bond perpendicular to NiTi surface is preferred to that for O−O bond parallel to NiTi surface, and O2 molecule only interacted with one nearest surface titanium atom during the adsorption process. Mulliken population and the partial density of state analysis show that the interaction between Ti and O atoms is mainly donated by O 2p and Ti 4s electrons on NiTi(110) surface, O 2p and Ti 4s, 4p electrons on NiTi(100) surface, respectively. The total density of state analysis shows that NiTi(100) surface is more favorable for O2 molecule adsorption.
Titanium diboride was calculated by the density function and discrete variational (DFT-DVM) method to study the relation between structure and properties. Titanium and its first-nearest boron atoms form a strong covalent bond, so TiB2 has high melting point, hardness and chemical stability. Titanium atom releases two electrons to form Ti2+ ions, and a boron atom gets one electron to come into B− ion. B− takes the sp2 hybrid and forms σ bonds to link other boron atoms in the same layer. The other one 2pz orbital of every B− ion in the same layer interacts each other to form the π molecular orbital, so TiB2 has fine electrical property. The calculated density of state is close to the result of XPS experiment of TiB2. Mainly Ti3d and B2p atomic orbitals contribute the total DOS near the Fermi level.
The kinetics of nucleation of phase transition is a phenomenal theory. Some new technologies of preparation of nanomaterials, for example, by shock wave and by electropulsing, are pulse interactions. Based on the known nonlinear theories of phase transition, the nonlinear kinetics of phase transition is discussed, and a soliton-like model is proposed. This mathematical method can not only explain the basic characteristics of pulse interactions and suddenness of phase transition, and possesses a consistency of mechanism for nucleation and growth.
To study the transformation process of calcium phosphate bioceramic in vivo, biodegradable porous β-tricalcium phosphate ceramics (β-TCP) were used in this experiment. The materials (ø5×8mm) were implanted in the tibia of rabbits. The β-TCP ceramics with bone tissue were retrieved, and treated for histology, and then observed by using a scanning electron microscope (SEM) and an electron probe X-ray microanalyzer (EMPA) every month. The results show that β-TCP ceramics bond to bone directly, new bones are forming and maturing with materials continuous degrading, and the materials are nearly replaced by the formed bone finally. Parts of the materials were degraded, absorpted and recrystallized, the others dispersped on the cancellous bone and the Haversian lamella with an irregular arrangement incorporating in bone formation directly by remodeling structure.
In order to reduce the sintering temperature and improve the preparing conditions of alumina bioceramics, the Mg−Zr−Y composite solid phase additives, were added into high purity Al2O3 micro-powder by chemical coprecipitation method. The powder was shaped under 200MPa cold isostatic pressure, and then the biscuits were sintered at 1600°C under normal pressure. The sintered alumina materials were tested and the sintering mechanism was discussed. The results show that physical properties of the material were improved comparatively. The Mg−Zr−Y composite solid additives could promote the sintering of alumina bioceramics and the mechanism is solid phase sintering.
The effects of small amounts of added elements such as aluminum, titanium and zirconium to MlNi3.8(CoMn)1.2 on its electrochemical performances and performances at high temperatures were investigated. It is found that the addition of aluminum brings about a significant, increase in the discharge capacity at high temperatures, and the capacity decay, during repeated charge-discharge cycles and the self-discharge are both suppressed, while the rate capability decreases. The alloy containing zirconium exhibits a longer cycle life and a better rate capability, but a much lower discharge capacity. The addition of titanium improves the rate capability, but the capacity decreases greatly. An X-ray diffraction analysis indicates that a second phase exists in the alloy with additive Zr or Ti, which improves the discharge-rate characteristics, and the superior stability of the alloy with additive Al may be due to the expansion of lattice parameters and cell volume.
A kind of novel ceria electrolyte was examined. Various trivalent oxides were added as co-dopants to Ce 0.8Gd 0.2O 1.9, and their effects on the conductivity of ceria electrolyte were discussed. It has been found that the co-dopant of trivalent oxides of Sm, Nd, La and Y improves the ionic conductivity notably. Furthermore, the fine original powders, co-dopant and higher sintering temperature may hasten the sintering.
The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared. The results show that platform thernolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery. The optimized working conditions and interference in the determination were invesigated. This result is consistent with that of XRF. The recovery is from 100.8% to 102.2%, the relative standard deviation is from 3. 47% to 5.56% (n=9), and the detection limit of selenium is 378 pg (C=44.5 μ/g to 97.3μg/g.). The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.
Poly ethylene oxide (PEO)x−V2O5−V2O5−MoO3 (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD, TG-DTA, FTIR, etc. The results show that V2O5−MoO3 xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement indicates that the intercalation of PEO improves insertion/extration properties of Li+ ions in the interlayer.
Synthesis of Ni/Al system intermetallic compound under the influence of pulsating electric current is researched. Reactions of Ni/Al system intermetallic compound are analyzed. It is found that solid-state reactions occur at Ni/Al interface and the main way of reactions is atoms diffusing each other under the influence of a high-density pulsating electric current.
By choosing different weight contents of Ni and Cu, Mo alloys have been densified under 1473 K-30MPa-1h in a vacuum furnace. The experimental results indicate that, when the contents of Ni and Cu are 3wt% and 2wt% respectively, the relative density of the sample reaches the maximum value. Ni and Cu play different roles in the process of sintering, the powder Ni, dissolved in the liquid Cu, shows more activating sintering feature for Mo than the solid Ni.
A rarely encountered sericite was investigated using X-ray diffraction, differential thermal analysis, and scanning electron microscopy. XRD analysis shows that the pattern of the sericite in the sample is similar to that of illite. DTA (TG) analyses show that only a weak heat absorption reaction takes place at 566°C, which is contributed to the polymorphic transformation of quartz, and no change in mass was detected in the range from ambient temperature to 800°C. These reveal that no water escapes from the crystal structure of the clay mineral during heating and therefore indicated that the clay mineral is obviously sericite in species instead of illite. SEM observations show that the sericite particles are significantly small in size and growth steps and irregular structures develop on the crystal surfaces as well as the colored mineral inclusions, which might suggest some loss of optical properties of the sample and thus lead to the variance, with earthy luster of the aggregate, from typical sericite in optical characters.
SiO2−GeO2 sols and gel glass coatings with different contents of germanium dioxide were fabricated. Stable and transparent sols could only be obtained when the content of GeO2 was under 35%. It is shown by SEM that only one continuous phase is observed in the coating of 65SiO2·35GeO2 and plenty of Ge, O and Si were all found in it. However, the separated phase is found in the coating of 60SiO2·40GeO2 and a large number of Ge and O. It is proved by the Raman scattering investigation that the separated phase in the coating of 60SiO2 ·40GeO2 is germanium dioxide. The congeries of hydrolystates of Cl3 GeCH2 CH2 COOH play the main role in the formation of the separated phase when the proportion of GeO2 is much higher. Si−O−Ge, Si−O−Si, and Ge−O−Ge bonds form in the coating of 65SiO2·35GeO2 and this coating is homogenous.
The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched. The impact strengthes and fixed velocity friction of the brake blocks prepared by different recipes were tested. The testing results show that it is feasible for needle-like wollastonite and fibrous sepiolite to take the place of asbestos as the reinforced materials of friction materials. The braking effect of the brake blocks is the best when the ratio of the needle-like wollastonite to the fibrous sepiolite was 1∶6.
The comminution of mica with an abrasive water jet is mainly based on three knids of effects, that is, high-speed collision, cavitating effect and shearing effect. Cavitation abrasive water jet was applied for the comminution of mica because cavitation abrasive water jet can make full use of the three effects mentioned above. Besides high speed impacting among particles, cavitation and shearing were also enhanced due to the divergent angle at the outlet of the cavitation nozzle. A JME-200 CX transmission electron microscope was used for observing the size distribution of particles. Variance analysis on the experimental results indicates that the effect of cavitation is much more significant than that of collision. The effect of pressure on comminution results becomes less with the decrease of the particle size.
The availability of accelerated chloride permeability test and the effect of w/c ratio, incorporation of silica fune, maximum aggregate size and aggregate type on the chloride permeability were studied. The mathematic analysis certifies that there is a linear relationship between accelerated test and natural diffusion. Test results show that the chloride permeability of concrete increases as w/c ratio increases whilst a limited amount of replacement of cement with silica fune, the chloride permeability decreases dramatically. The maximum aggregate size in the range of 8 to 25 mm seems also affect chloride permeability but with a much less significant level. The chloride permeability of silica fume lightweight aggregate concrete is very low, especially the concrete made with dry lightweight concrete. The chloride permeability can be evaluated by this accelerated test method.
The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved. The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C). To obtain the same strength, therefore, a smaller fiber volume content in FGDM/C is needed than that in FHDM/C. The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.
Copper gangue (CG), containing a large amount of water with grain sizes of 0.037 to 0.10mm, is an inactive industrial waste generated from copper refineries. When it is dried and used as a cement admixture, the influence of the presence of finely dispersed metallic particles in CG on the microstructure and compressive strength of cement paste has been studied. The results show that the higher the replacement of CG is, the lower the compressive strength of cement mortar is. However, the long-term strength of the specimens with 10% CG, especially after being cured for 3 months, approached to that of the plain mortar. Its mechanism was studied by an electron probe X-ray microanalyzer (EPXMA). The results indicate that a small quantity of Fe(OH)3·nH2O slowly formed from Fe2O3 in the presence of Ca(OH)2, free CaO and MgO of the clinker also slowly hydrated and formed Ca(OH)2 and Mg(OH)2 respectively, so the hardened cement paste became more compact.
To improve the mechanical properties of concrete, Layered Hybrid Fiber Reinforced Concrete (LHFRC) was developed in this paper. Through comparative tests, the effects of layered hybrid fibers on a series of mechanical properties of concrete were discussed. The mechanical properties include compressive strength, tensile strength, flexural strength, compressive stress-strain relationship, flexural toughness and cracking resistance of concrete. The testing results and analysis demonstrate that layered hybrid fibers can significantly improve the flexural strength, toughness and cracking resistance of concrete while the cost of concrete increases slightly.
The chemical reaction between polyvinyl alcohol (PVA) and tri (dioctylpyrophosphoryloxy) isopropyl titanate (NDZ-201) was studied using X-ray photoelectron spectroscopy (XPS). The results show that some C−OH functional groups of PVA react with the titanate coupling agent to form CPVA−O−Ti−O−CPVA bond. The cross-linking of the PVA chains occurs through the formation of CPVA−O−Ti−O−CPVA bonds and produces a three dimensional hydrophobic polymer network. Accordingly, the mechanism is proposed that the titanate coupling agent improves the noisture sensitivity of high alumina cement/polyvinyl alcohol (HAC/PVA) based macro defect free (MDF) composite material.
An ecotypic revetment material consiting of nutrition-expansive perlitic-cement composites is introduced. This planting material can combine vegetation recovery with slope protection. The XRD, SEM and image analysis techniques were used to study its composition and microstructure. Its strength was measured by an electro-hydraulic servo-controlled testing machine. The results show the uncofined compressive strength is about393.6 kPa, and the average elastic modulus is about47.0 MPa. The quartz, felspar, chlorite and calcite are the main non-clay minerals in the planting material. Its particles are mainly spherical, and the range of the equivalent diameter is1.83 to15.96 μm. The results also show the planting material contains a large amount of micro non-capillary and capillary pores, and has a microstructure characteristic of honeycomb and coralline. CSH gel produced by hydration of cement increases the strength and water stability of the particles. The anisotropy and slight orientation of the particles increase the void cross-section area, providing and explanation of the high permeability for the planting material. The better porosity of the planting material is apt tokeep moisture and nutriment, provides oxygen for plant root breathing, and aids to exhaust the carbon dioxide by means of exchanging with atmosphere, hence it can facilitate vegetation.
Based on generalized Hele-Shaw (GHS) model, a numerical simulation of phenolic sheet molding compound (P-SMC) in compression molding is realized by finite element step-by-step computing method. Finite elemental computing and post analysis programs have been written. The compression mold filling process, time and pressure requirements of P-SMC in a closed mold are predicted, and a good agreement is shown when compared with experiments. It will be of theoretical significance for the mold design and the optimization of the technological parameters in the compression molding of sheet molding compound.
In the process of ultrafine particle classification, the separation curve, which reflects the characteristics of separating process, is frequently influenced by the characteristics of separation flow field operating parameters, etc. This paper introduces the concept of system deviation and deduces the calculating method of the separation curves. Meanwhile, it analyses the influences of classification flow field’s specific properties and some operating parameters on the separation curves. The results show that, in the process of ultrafine particle classification, the local vortex in the separation field improves the separation efficiency to a certain degree, but the accuracy will decrease; the coacervation action of particles will seriously influence the classification accuracy.
Bond connectivity topological index Si based on chemical bonds was defined by using a matrix method. And Si is formed by atomic parameters such as the number of valence electrons, the number of the highest main quantum of atoms and the bonding electrons and bond parameters such as the length of bonds, the electronegativity difference of bonding atoms. The molecular bond connectivity topological index S is composed of Si. The thermodynamic properties of saturated hydrocarbons, unsaturated hydrocarbons, oxygen organic, methane halide and transitional element compounds and the molecular bond connectivity topological index S have an optimal correlative relationship.
The properties of road base course materials of granular soils stabilized by AGS granular soil stabilizing cement[1] were studied. The AGS cement has an expansibility to a certain degree, so the dry shrinkage of AGS cement paste and AGS stabilized granular is much lower than that of Portland slag cement. AGS has a good suitability to granular soils. Granular soils stabilized by AGS have a much higher strength than that of soils stabilized by P S cement. The same strength can be reached with 20% reduction of cement dosage for AGS cement. And their elastic and resilient modulus are similar, but the former has a much higher tensile splitting strength, so the AGS stabilized granular has a much better anti-cracking performance than that of the P S stabilized granular. The reduced value of the strength and the density with the retard time for the granular soils stabilized by AGS is lower than that for P S cement.