Effect of Temperature on the Release of Transparent Exopolymer Particles(TEP)and Aggregation by Marine Diatoms(Thalassiosira weissflogii and Skeletonema marinoi)

The presence of diatoms is accompanied by the production of a large amount of extracellular polymeric substances,which are mainly composed of carbohydrates.Transparent exopolymer particles(TEP)are a large class of extracellular polymeric substances with high stickiness that promotes the formation of aggregates and marine snow,which affects marine bio-carbon pump efficiency.The purpose of this research was to determine how temperature increases affect the allocation of cellular carbohydrates and the formation and aggregation of TEP.The results showed that the responses of two different diatom species(Thalassiosira weissflogii and Skeletonema marinoi)differed according to temperature.The cell density and chlorophyll a concentration of the former were not significantly correlated with temperature,while those of the latter were significantly decreased with increasing temperature.This indicates that the two species of diatom may have different heat tolerance ranges.A temperature increase will promote significant formation of TEP by both types of diatoms,including aggregation of S.marinoi as the temperature rises,meaning that the high temperature will produce an aggregate with a larger particle size and thus may increase the sedimentation rate of organic carbon.Moreover,the TEP aggregation of T.weissflogii did not increase;therefore,its particle size was smaller,and so it may remain on the sea surface at high temperatures for longer periods.These influences have a profound impact on the biogeochemical cycling of carbon.

Tribological properties and wear prediction model of TiC particles reinforced Ni-base alloy composite coatings

TiC particles reinforced Ni-based alloy composite coatings were prepared on 7005 aluminum alloy by plasma spray. The effects of load, speed and temperature on the tribological behavior and mechanisms of the composite coatings under dry friction were researched. The wear prediction model of the composite coatings was established based on the least square support vector machine (LS-SVM). The results show that the composite coatings exhibit smaller friction coefficients and wear losses than the Ni-based alloy coatings under different friction conditions. The predicting time of the LS-SVM model is only 12.93%of that of the BP-ANN model, and the predicting accuracies on friction coefficients and wear losses of the former are increased by 58.74%and 41.87%compared with the latter. The LS-SVM model can effectively predict the tribological behavior of the TiCP/Ni-base alloy composite coatings under dry friction.

Photodegradation and Aggregation Prevention of Natural Melanin Nanoparticles by Silica Coating Method

Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, the photodegradating and aggregating natures of melanin, to some extent, restrict the development of this eco-friendly biomaterial. This study is conducted to overcome both disadvantages by a mature method that coating the original melanin nanoparticles with silica as shells. The results revealed that the aggregation of the melanin/silica nanoparticles (MSNP) was decreased obviously by a 5 h coating and appeared a uniformly mono-dispersed solution. The MSNP that coated for 20 h provided an efficient protection on the photodegradation of the melanin with a 50% maintenance of the melanin content compared with 16% of original melanin and 2% of MSNP-5 h.

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter(SPM) within the water column.However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scienti?c cruise in July 2016, in situ ef fective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into(1) small particles(<32 μm),(2) medium particles(32–256 μm) and(3) large particles(>256 μm). Large particles and medium particles dominated the total volume concentrations(VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values(<0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values(0.1–1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles <32 μm in?uenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic ?ne particles, while large particles were mucus-bound organic aggregates or individual plankton.The vertical distribution of coarser particles was clearly related to water strati?cation. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of?ne material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer.Abundant large biogenic particles were present in both surface and middle layers.

The Synthesis of TiNi and Composite Particles in Molten Salts

A novel process for synthesizing TiNi and TiNi/TiC particles, called the high-temperature salt-melting method, is discussed in this paper. So far as this method is concerned, the molten salts are a reaction medium that does not take part in the chemical reaction but can be easily dissolved by water washing. With this method, TiNi shape memory alloy and TiNi/TiC composite particles were prepared in molten salts at 680-850℃. TiNi particles, ranging from 100 nm to several microns in diameter, are obtained and the reverse martensitic transformation is confirmed in these particles by the differential scanning calorimetry （DSC）. The reaction temperature and the holding time have no significant influence on the particle size, morphology or the reverse martensitic transformation characteristics. In the molten salts, the released heat of the chemical reaction causes the local temperature to rise quickly, which is the key to obtaining the desired particulate composite.

Friction behavior of Ti-30Fe composites strengthened by TiC particles

Ti-Fe-x TiC(x=0, 3, 6, 9, wt.%) composites were fabricated through low temperature ball milling of Ti, Fe and TiC powders, followed by spark plasma sintering. The results show that β-Ti, β-Ti-Fe, η-Ti4 Fe2 O0.4 and TiC particles can be found in the composites. The microstructure can be obviously refined with increasing the content of TiC particles. The coefficient of friction(COF) decreases and the hardness increases with increasing the content of TiC particles. The adhesive wear is the dominant wear mechanism of all the Ti-Fe-x TiC composites. The Ti-Fe-6 TiC composite shows the best wear resistance, owing to the small size and high content of TiC particle as well as relatively fine microstructure. The wear rate of the Ti-Fe-6 TiC composite is as low as 1.869× 10-5 mm3/(N·m) and the COF is only 0.64. Therefore, TiC particle reinforced Ti-Fe based composites may be utilized as potential wear resistant materials.

Microstructure and wear properties of the electroslag remelting layer reinforced by TiC particles

The electroslag remelting （ESR） layer reinforced by TiC particles was obtained by electroslag remelting. The microstructure and wear properties of the ESR layer were studied by means of scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and wear test. The results indicate that TiC particles are synthesized by self-propagating high-temperature synthesis （SHS） reaction during the electroslag remelting process. The size of TiC particles is in the range of 1-10 μm, and the distribution of TiC particles is uniform, from outside to inside of the ESR layer, and the volume fraction and the size of TiC particles decrease gradually. Molten iron and slag flow into porosity due to the SHS process leading to rapid densification and the elimination of porosity in the ESR layer during the ESR process. TiC particles enhance the wear resistance of the ESR layer, whereas CaF2 can improve the high temperature lubricating property of the ESR layer.

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.

Microstructure of Fe-Based Alloy Hardfacing Coating Reinforced by TiC-VC Particles

Mierostrueture of the Fe-based alloy hardfaeing coating reinforced by TiC-VC particles was investigated by means of SEM, TEM, XRD and EPMA. The thermodynamics and effect of elements on the carbides were discussed. The result shows that TiC-VC carbides can be formed during arc welding. Carbides with particle size of 2 ～4μm are uniformly dispersed in the matrix. Evidently the covering components and their amount affect the microstrueture and hardness of the coatings. An excellent microstructure and hardness of hardfacing coating were obtained, while the amount of graphite, FeTi and FeV was controlled within the range of 8%- 10%, 15%- 18% and 8%- 12%, respectively.

Generalization of the linguistic aggregation operator and its application in decision making

A generalization of the linguistic aggregation functions （or operators） is presented by using generalized and quasiarithmetic means. Firstly, the linguistic weighted generalized mean （LWGM） and the linguistic generalized ordered weighted averaging （LGOWA） operator are introduced. These aggregation functions use linguistic information and generalized means in the weighted average （WA） and in the ordered weighted averaging （OWA） function. They are very useful for uncertain situations where the available information cannot be assessed with numerical values but it is possible to use linguistic assessments. These aggregation operators generalize a wide range of aggregation operators that use linguistic information such as the linguistic generalized mean （LGM）, the linguistic OWA （LOWA） operator and the linguistic or- dered weighted quadratic averaging （LOWQA） operator. We also introduce a further generalization by using quasi-arithmetic means instead of generalized means obtaining the quasi-LWA and the quasi-LOWA operator. Finally, we develop an application of the new approach where we analyze a decision making problem regarding the selection of strategies.

Microstructure of a Ni Matrix Composite Coating Reinforced by In-situ TiC Particles Using Plasma Cladding

Plasma cladding process was used to prepare the TiC/Ni composite coating on the mild steel substrates. The TiC particles were synthesized in-situ. Microstructure and properties of the coating were investigated by optical microscopy, X-Ray diffraction, SEM, TEM and microhardness tester. The results show that the interface between the coating and the substrate is metallurgically bonded. The coating was uniform and almost defect-free when [Ti+C] varied from 10% to 20% after ball milling. The microstructure of the coating is mainly composed of -Ni dendrite, interdendritic eutectic ( -Ni austenite, M23C6 and CrB) and TiC particles. Most of the TiC particles are spherical and a small fraction is blocky in size of l^2(im. The TiC particles are smaller at the bottom than near the top of the coating. The coating has a gradient microstructure and a highest hardness of lOOOHyO. 1.

Anthracene Adsorption to Particles and Water-Stable Aggregates of Mangrove Sediment in Jiulong River Estuary, China

Polycyclic aromatic hydrocarbons (PAHs) pollution in mangroves has drawn much attention, but knowledge of the sorption of PAHs in mangrove sediment is limited. This study investigated the particles and water-stable aggregates (WSA) of mangrove sediment in Jiulong River Estuary, China, and the characteristics of anthracene adsorption to them. The adsorption of anthracene was strongly influenced by the physicochemical and structural properties of sediment particles and WSA. The main sorbents of mangrove sediment were carbonized particles and clays. The porous structure of carbonized particles made it easy to sequestrate sequester the anthracene, and the aging allowed anthracene to move into deeper sites of the carbonized particles. Clays had high anthracene-fixing capacities, and they included organic matters and formed aggregates. The sorption contents coefficient Kf of anthracene with WSA of different sizes increased in the order 0.063 - 0.25 mm > 0.063 mm > 0.25 - 1.0 mm > 1.0 mm. The order was correlated with which due to the contents and characteristics of organic matters in the aggregates.

Modeling of Adhesive Particles Using a Combination of the Two-Body Interaction and Phase-Field Methods

Discrete materials such as powders and granular materials have been widely used due to their specific characteristics. The precise evaluation is accordingly becoming important, and various numerical schemes have been developed. However, the interactions among the constituent particles are still difficult to model precisely. Especially, contact conditions, which vary with material properties and circumstances, are difficult to formulate. In this study, a computational model for simulating adhesive particles on contact in a many-particle system is proposed. The interaction between the particles was represented by a two-body repulsive force that depends on the distance between particles and an additional adhesive force at the contact point. A phase-field variable was introduced to express the surface of each particle, and the adhesive force was formulated using the phase-field distribution. As a result, the adhesion of particles was properly expressed. For a mono-particle system, neighboring particles adhered and uniformly aggregated, while for a dual-particle system, several characteristic patterns were obtained depending on the initial arrangement of the particles. Repulsive contact was also considered as a specific case, and the corresponding results were obtained.

The fractal research of Ultrafine Fe particle aggregation

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Coercivity of fractal aggregates formed by single-domain particles

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Friction and wear behavior of TiC particle reinforced ZA43 matrix composites

TiC/ZA43 composites were fabricated by XD TM and stirring casting techniques. The tribology properties of the unreinforced ZA43 alloy and the composites were studied by using a block on ring apparatus. Experimental results show that the incorporation of TiC particles improves the microstructure of ZA43 matrix alloy. The coefficient of friction μ and the width of worn groove decrease with the increase of TiC volume fraction φ (TiC). The width of worn groove and μ of the composite during wear testing increase with increasing the applied load. Metallographic examinations reveal that unreinforced ZA43 alloy has deep ploughing grooves with obvious adhesion phenomenon, whereas TiC/ZA43 composites have smooth worn surface. Delamination formation is related to the fatigue cracks and the shear cracks on the surface. [

Microstructure and mechanical properties of Al-TiB_2/TiC in situ composites improved via hot rolling

A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the particles and mechanical properties of the composites,subsequent hot rolling with increasing reduction was carried out.The microstructure evolution of the composites was characterized using field emission scanning electron microscopy(FESEM)and the mechanical properties were studied through tensile tests and microhardness measurement.It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction.The ultimate tensile strength and microhardness of the composites with90%rolling reduction reach185.9MPa and HV59.8,respectively,140%and35%higher than those of as-cast ones.Furthermore,the strengthening mechanism of the composite was analyzed based on the fracture morphologies.

Soil Aggregation and Its Relationship with Organic Carbon of Purple Soils in the Sichuan Basin,China

The interaction of soil aggregate dynamics with soil organic carbon is complex with varied spatio-temporal processes in macro-and micro-aggregates. This paper is to determine the aggregation of soil aggregates in purple soils （Regosols in FAO Taxonomy or Entisols in USDA Taxonomy） for four types of land use, cropland [corn （Zea mays L.）], orchard （citrus）, forestland （bamboo or cypress）, and barren land （wild grass）, and to explore their relationship with soil organic carbon in the Sichuan basin of southwestern China. Procedures and methods, including manual dry sieving procedure, Yoder＇s wet sieving procedure, pyrophosphates solution method, and Kachisky method, are used to acquire dry, wet, and chemically stable aggregates, and microaggregates. Light and heavy fractions of soil organic carbon were separated using 2.0 g·mL^-1 HgI2-KI mixed solution. The loosely, stably, and tightly combined organic carbon in heavy fraction were separated by extraction with 0.1 M NaOH and 0.1 M NaOH-0.1M Na4P2O7 mixed solution （pH 13）. The results show that the contents of dry and wet macroaggregates 〉0.25 mm in diameter were 974.1 and 900.0 g·kg^-1 highest in red brown purple soils under forestland, while 889.6 and 350.6 g·kg^-1 lowest in dark purple soil and lowest in grey brown purple soils under cropland, respectively. The chemical stability of macroaggregates was lowest in grey brown purple soil with 8.47% under cropland, and highest in red brown purple soil with 69.34% under barren land. The content of microaggregates in dark purple soils was 587g·kg^-1 higher than brown purple soils, while 655g·kg^-1 in red brown purple soils was similar to grey brown purple soils （651g·kg^-1）. Cropland conditions, only 38.4% of organic carbon was of the combined form, and 61.6% of that existed in light fraction. Forestland conditions, 90.7% of organic carbon in red brown purple soil was complexed with minerals as a form of humic substances. The contents and stability of wet aggregates 〉 0.25 mm, contents and stability of chemically stable aggregates 〉0.25 mm, contents of microaggregates 〉 0.01 mm, contents of aggregated primary particle （d〈0.01 mm） and degree of primary particles （d 〈0.01 mm） aggregation were closely related to the concentrations of total soil organic carbon, and loosely and tightly combined organic carbon in heavy fraction. Soil microaggregation could be associated with organic carbon concentration and its combined forms in heavy fraction. There was a direct relationship between microaggregation and macroaggregation of soil primary particles, because the contents of wet aggregates 〉 0.25 mm and its water stability of aggregates were highly correlated with the contents of aggregated primary particle （d 〈 0.01 mm） and the degree of primary particles （d 〈 0.01 mm） aggregation.

Synthesis and Deposition of TiC-Fe Coatings by Oxygen-acetylene Flame Spraying

A simpler and more convenient method for producing wear-resistant, TiC-reinforced coatings were investigated in this study. It consists of the simultaneous synthesis and deposition of TiC-Fe materials by oxyacetylene flame spraying. Solid reagents bound together to form a single particle are injected into the flame stream where an in-situ reaction occurs. The reaction products are propelled onto a substrate to form a coating. Microstructural analyses reveal that TiC and Fe are the dominant phases in the coatings. The reaction between Ti and C happens step by step along with the reactive spray powder flight, and TiC-Fe materials were mainly synthesized where the spray distance is 125-170 mm. The TiC-Fe coatings are composed of alternate TiC-rich and TiC-poor lamellae with different microhardness of 11.9-13.7 and 3.0-6.0 GPa, respectively. Submicron and round TiC particles are dispersed within a ductile metal matrix. The peculiar microstructure is thought to be responsible for its good wear resistance, which is better nearly five times than WC-reinforced cermet coatings obtained by traditional oxyacetylene flame spray.

Observation of fine particle aggregating behavior induced by high intensity conditioning using high speed CCD

The aggregating behavior between bubbles and particles induced by high intensity conditioning (HIC) was studied using high speed CCD technique. Bubble size measurement was conducted, and the attachment behavior between bubbles and particles in HIC cell and flotation cell were observed. The results show that in HIC cell, high intensity conditioning creates an advantage environment for the formation of small size bubble due to hydrodynamic cavitations, and these fine bubbles have high probability of bubble-particle collision, which will enhance fine particle flotation. The bubble-particle attachment experiments indicate that in high intensity conditioning cell, a lot of fine bubbles are produced in situ on the surface of fine particles, and most of fine particles are aggregated under the bridging action of fine bubbles. The observation of bubble-particle interaction in flotation cell illustrates that aggregates created by HIC can be loaded more easily by big air bubble in flotation cell than those created by normal conditioning.