Characterization, preparation, and reuse of metallic powders for laser powder bed fusion: a review

Laser powder bed fusion(L-PBF) has attracted significant attention in both the industry and academic fields since its inception, providing unprecedented advantages to fabricate complex-shaped metallic components. The printing quality and performance of L-PBF alloys are infuenced by numerous variables consisting of feedstock powders, manufacturing process,and post-treatment. As the starting materials, metallic powders play a critical role in infuencing the fabrication cost, printing consistency, and properties. Given their deterministic roles, the present review aims to retrospect the recent progress on metallic powders for L-PBF including characterization, preparation, and reuse. The powder characterization mainly serves for printing consistency while powder preparation and reuse are introduced to reduce the fabrication costs.Various powder characterization and preparation methods are presented in the beginning by analyzing the measurement principles, advantages, and limitations. Subsequently, the effect of powder reuse on the powder characteristics and mechanical performance of L-PBF parts is analyzed, focusing on steels, nickel-based superalloys, titanium and titanium alloys, and aluminum alloys. The evolution trends of powders and L-PBF parts vary depending on specific alloy systems, which makes the proposal of a unified reuse protocol infeasible. Finally,perspectives are presented to cater to the increased applications of L-PBF technologies for future investigations. The present state-of-the-art work can pave the way for the broad industrial applications of L-PBF by enhancing printing consistency and reducing the total costs from the perspective of powders.

Preparation and characterization of epoxy asphalt binder for pavement of steel deck bridge

A kind of thermosetting asphalt binder designated as epoxy asphalt, which is composed of two components： maleated asphalt with curing agents and accelerant of epoxy resin and epoxy resin, was prepared. Its paving feasibility and concrete performances were investigated using Brookfield viscosimeter, direct tensile test （DTT）, Marshall testing and the MTS 810 hydraulic servos-system, respectively. Although only 50% to 60% of added maleic anhydride （MAH） reacted with the base asphalt irreversibly （probably by Diels-Alder mechanism）, the curing rate, rupture elongation and tensile strength of maleated epoxy asphalt were enhanced more evidently than those of unmaleated epoxy asphalt. As a result, an epoxy asphalt made from 4% MAH modified asphalt and other curing agents was featured to have an average rupture elongation of 281.9%, an average tensile strength of 2. 63 MPa, and the Marshall stability of its cured concrete reached 37. 0 kN, while that of uncured concrete was 10. 2 kN and the combined beam of fatigue test was still found to behave well after 12 × 10^6 cycles load.

Preparation and characterization of manganese - containing silicates with Z S M - 48 structure

报道了新型杂原子分子筛Ｍｎ－ＺＳＭ－４８的合成与表征。红外光谱和紫外漫反射光谱测试表明Ｍｎ（Ⅱ）离子进入了分子筛骨架。Ｍｎ（Ⅱ）同晶取代Ｓｉ（Ⅳ）导致产物晶粒的形貌和热性质有所不同。反应混合物中１，６－己二胺的含量，水含量和ＳｉＭｎ比对产物的晶化有很大影响。

Gold Characterization by MLA and Technological Tests-Discussion of Sample Preparation and Results

Gold has been present throughout the history of mankind and used to make jewelry and coins, and recently, acquired several industrial uses. The price of gold in international market had a significant increasing, surpassing 100% in the last five years. Thereby, deposits with low levels of gold content, gold with complex associations or in a very fine particle size became exploitable again, allowing new projects and expansion of existing ones. However, for maximum process efficiency is indispensable a deep knowledge of the characteristics of these minerals and their behavior in face of beneficiation processes. Consequently, an accurate routine for mineralogical and technological characterization is essential.

Preparation and characterization of mixed hydroxy-Fe-Al pillared montmorillonite with large basal spacing

Mixed hydroxy-Al-Fe pillared montmorillonites with large basal spacing were successfully prepared through cation-exchanging of Na +- montmorillonite with mixed hydroxy-Al and hydroxy-Fe pillaring solutions made from hydrolysis of corresponding metal salts, followed by calcination to convert hydroxy-Al and hydroxy-Fe into intercalated polycations. According to XRD analysis, the basal spacing d(001) of pillared products dramatically enlarged from 12.7 *! in the Na-montmorillonite to 81 *! in the hydroxy-Fe -montmorillonite and 77.5 *! in mixed hydroxy-Al-Fe-montmorillonite. The N_2 BET surface areas of the pillared montmorillonites also greatly increased to more than 200 m 2/g as compared to about 27 m 2/g for the Na-montmorillonite. IR analysis of hydroxy-Fe, and mixed hydroxy-Al-Fe pillared montmorillonites revealed a new absorption vibration at 1384 cm -1 wavelength. XRF elemental analysis data also showed a high content of Fe_2O_3 in the hydroxy-Fe pillared montmorillonite.

Preparation and characterization of amino or carboxyl-functionalized ionic liquids

New functionalized ionic liquids, 1-carboxylmethyl-3-methylimimidazolium hexafluorophosphate or fluoborate and 1-aminoethyl-3-methylimimidazolium hexafluorophosphate or fluoborate have been synthesized and investigated. The obtained amino or carboxyl-functionalized ionic liquids were all characterized by FT-IR, ^1H NMR and MS （ESI） and their properties such as freezing point, viscosity, solubility, specific gravity, surface tension, and interfacial tension were also determined.

Preparation and Characterization of CeO_2 Superfine Powder

The CeO_2 superfine powder was prepared by the co-precipitation method, using the industrial grade Ce_2(CO_3)_3 and NH_4HCO_3 as starting material and precipitating reagent, respectively. The precipitated precursons and the calcinated products were characterized by the thermogravimetric analysis/thermoanalysis (TGA/DTA), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The results show that using NH_4HCO_3 as a precipitating reagent, the precipitate decomposed full as it was heated to 360 ℃. The CeO_2 superfine powder formed by calcinating the precipitate belongs to a cubic CaF_2-type structure and has the first mean particle diameter 140 nm and second mean particle diameter 630 nm. The CeO_2 powder particles aggregate and grow with raising the calcination temperature.

Preparation and Characterization of New Type Ionic Liquids

A new type of ionic liquids containing cation of diacetone acrylamide [or N-(1,1- bismethyl-3-oxo-butyl)acrylamide] and anions such as CH3COO- (Ac), CF3COO- (TF), BF4-(BF), PF6-(PF), HSO4-(SO) and Cl-(Cl) were prepared by normal neutralization. The obtained ionic liquids were identified by FT-IR and 1H NMR spectroscopy. However, their properties such as melting point, conductivity, viscosity etc. were determined.

Preparation,Characterization and Application of ZnAlLa-Hydrotalcite-Like Compounds

The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.

Preparation, characterization and catalytic performance of single-atom catalysts

Supported and colloidal single‐atom catalysts(SACs),which possess excellent catalytic properties,are particularly important in both fundamental studies and practical applications.The progress made in the preparation methods,characterization,catalytic performances and mechanisms of SACs anchored to metal oxides,two‐dimensional materials and the surface of metal nanoclusters(NCs)are reviewed.The different techniques for SAC fabrication,including conventional solution methods based on co‐precipitation,incipient wetness co‐impregnation,and the chemical vapor deposition method,as well as the newer atom layer deposition(ALD)and galvanic replacement methods,are summarized.The main results from experimental and theoretical studies of various catalytic reactions over SACs,including oxidation reactions,hydrogenation,water gas shift,photocatalytic H2evolution and electrochemical reactions,are also discussed.Moreover,the electronic properties of the single atoms and their interactions with the supports are described to assist in understanding the origin of the high catalytic activity and selectivity of SACs.Finally,possible future research directions of SACs and their applications are proposed.

Efficient Preparation and Characterization of Functional Graphene with Versatile Applicability

Graphene,as star versatile materials having extraordinarily high electric conductivity,electron mobility,thermal conductivity,thermal stability,optical transparency,and mechanical strength,has attracted much attention from scientists and engineers in the field of materials,chemistry,physics,energy,and environment in the last decade and achieved fruitful accomplishment.This review discusses preparation strategies,functionality,characterization,and applications for two dimensional nanosheet and quasi-onedimensional nanoribbon of graphene through direct exfoliation of graphite,chemical vapor deposition of hydrocarbon,laser-induced direct synthesis of graphene,laser etched graphene oxide in the dry state without the use of toxic reducing agent hydrazine,unzipping carbon nanotube,and polycondensation of polycyclic aromatics on the basis of 178 representative references mostly in 2015.The stabilization of graphene oxide prepared in chemical preparation in " top-down" is emphasized.Several vital classic methods of characterizing molecular structure,C/O ratio,defect,morphology,single-or few-layered( 2 to 10 layers) structure,porous and hollow structures,including Raman spectroscopy,AFM,SEM,TEM,STM,electron diffraction,X-ray diffraction,and X-ray photoelectron spectroscopy are systematically introduced.Because graphene possesses novel incomparable multifunctionalities,its versatile applications as novel conducting additives,reinforcing filler,separation membrane,sensor,anticorrosive coating,catalyst,electromagnetic shield,lubricant,and flexible electrode materials in electrochemical and electronic devices,including photovoltaic cells,supercapacitors,rechargeable batteries,sensors,field effect transistors,light emitting diodes,separation membranes,adsorbents and absorbents,catalysts,electro-optic modulator,terahertz emitter and detector,and semiconductors,have been mentioned.Especially in the aspect of both high performance and cost-effectiveness,graphene is expected to be even superior to the expensive carbon nanotubes.

Preparation and Characterization of Collagen-GAGs Bioactive Matrices for Tissue Engineering

Collagen materials were crosslinked by 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) in the presence of chondroitin sulfate (CS), one of glycosaminoglycans (GAGS). PVA and chitosan were also blended with collagen. The physical and chemical properties of the matrices were characterized by SEM, DSC, and ESCA. L929 cells were implanted on the matrices to show the cytotoxic and the biological characters of the materials. The results indicate that EDC is an effective and non-cytotoxic cross-link reagent, which can replace the common dialdehyde reagent. The attachment of CS can improve the stability of collagen and accelerate cell growth. The addition of PVA can prepare porous matrices with smaller bore size. There are reactions between the chitosan and collagen, and the composite has good biological character. The presence of chitosan can also increase the amount of incorporated CS.

Preparation and characterization of NaY zeolite in a rotating packed bed

NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.

Preparation and characterization of CuO-CoO-MnO/SiO_2 nanocomposite aerogels as catalyst carriers

CuO-CoO-MnO/SiO2 nanocomposite aerogels were prepared by using tetraethyl orthosilicate(TEOS) as Si source,and aqueous solution of Cu,Co and Mn acetates as the precursors via sol-gel process and ethanol supercritical drying technique.The gelatination mechanism was investigated by nuclear magnetic resonance(NMR) and X-ray photoelectron spectroscopy(XPS).The microstructure and composition of the CuO-CoO-MnO/SiO2 nanocomposite aerogels were characterized by field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),electron dispersive spectroscopy(EDS) and XPS.The specific surface area,pore size and pore size distribution of the nanocomposite aerogels were determined by the Brunauer–Emmett–Teller(BET) method.The products were analyzed by gas chromatography(GC).The results show that the CuO-CoO-MnO/SiO2 nanocomposite aerogels are porous,with a particle size distribution of 10–150 nm,a pore size distribution of 2–16 nm,an average pore size of 7.68 nm,and a specific surface area of 664.4-695.8 m2/g.The molar fraction of transition metals in the nanocomposite aerogels is 0.71%-13.77%.This kind of structure is favorable not only to increase the loading of catalysts,but also to make full use of the effect of transition metal oxides as cocatalysts;CuO-CoO-MnO/SiO2 nanocomposite aerogels can be used as a novel catalyst carrier in the safer and environment-friendly synthesis of diphenyl carbonate and other fields of catalysis.

Preparation and Characterization of Potassium Monopersulfate/Ethyl Cellulose Microcapsules and Their Sustained Release Performance

Environmental cleaning is an important aspect of bacteria control.Ethyl cellulose microcapsules containing potassium monopersulfate(PMCM)were prepared by emulsified solvent diffusion method.The chemical structure and microstructure of the obtained PMCM was characterized by methods of Fourier transform infrared spectroscopy(FT-IR),optical microscopy,scanning electron microscopy and X-ACT energy dispersive X-ray spectroscopy.The SEM micrographs of the PMCM containing 21.6%of C,46.8%of O,10.7%of S and 19.4%of K was relatively smooth.Thermal stability,sustained release performance,and antimicrobial activity of PMCM were investigated.The results showed that the drug loading and encapsulation efficiency of PMCM were 30.3%and 42.6%respectively.Potassium monopersulfate was fully released after 8 h,following a Fickian diffusion mechanism.Results showed that the microcapsules prepared with a high concentration of potassium monopersulfate solution showed a good antimicrobial effect.The microcapsule wall of the resulting PMCM increased with increasing ethyl cellulose content and had high thermal stability from the data of 69%residue rate.The excellent thermal stability and high sustained release performance of PMCM showed high application value.

Preparation and characterization of uniform circinate aggregates of sheet ZnO nanoparticles

Uniform circinate aggregates of sheet ZnO nanoparticles with a specific surface area of 24 m^2·g^-1 were prepared by the direct precipitation method.The circinate aggregates were hexagonal ZnO,with the wall thickness ranging from 0.5 to 1 μm and the diameter ranging from 5 to 10 μm.The backs of the circinate aggregates were regularly arranged by numerous sheet ZnO nanoparticles with a thickness of 30-80 nm and a diameter of 300-400 nm.The precursors were aggregates of sheet Zn5（CO3）2（OH）6 nanoparticles,which were decomposed into ZnO by calcining in air in the range of 200-285°C,and the ZnO retained the similar special structure.The C2H5OH content had a significant effect on the formation of sheet ZnO.The centripetal force,the Van der Waals force,and the hydrogen bond were deduced as the driving forces of the formation of circinate.

Preparation and characterization of wood/montmorillonite nanocomposites

With montmorillonite （MMT） organically modified as organophilic MMT （OMMT） and water-soluble phenol formaldehyde resin （PF） as intermediate, Chinese fir （Cunningharnia lanceolata） wood/MMT nanocomposites （WMNC） were prepared via nano intercalation compounding and characterized by XRD, SEM and FTIR. Results show that： 1） the preparation of OMMT is very successful; 2） the self-made PF can effectively intercalate into MMT to increase markably its gallery distance and even exfoliate its nano silicate laminae; 3） the XRD analysis indicates that some exfoliated MMT enters the non-crystallized region of microfibrils in wood cell walls and the crystallinity degree of wood in WMNC decreases; 4） the SEM graphs show that multiform MMT exists in WMNC. Some grains block in wood cell lumen, some layers adhere to the wood surface of the inner cell wall and some exfoliated nanolaminae even insert into wood cell walls; and 5） the FTIR analysis suggests that MMT and wood in WMNC perhaps interact via certain chemical bonding.

Recent Advances in the Preparation, Characterization and Applications of Locust Bean Gum-Based Films

Locust bean gum(LBG)is a typical galactomannan isolated from carob bean(Ceratonia siliqua L.)cultivated in the Mediterranean area.Due to its superior biodegradable,rheological and film-forming properties,LBG has been used alone or combined with other biopolymers(e.g.,polysaccharides,proteins and lipids)to develop films.Till now,different kinds of functional ingredients(e.g.,montmorillonite,bacteriocins,antibiotics,plant extract,essential oils and microbial cells)have been added into LBG-based films.Notably,the physical and functional properties of LBG-based films are affected by many factors,such as the structure of LBG,the type and content of other biopolymers and functional ingredients,and the physical treatment of film-forming solution.LBG-based films can be not only used as active packaging and edible coating in food industry but also used as wound dressings in pharmaceutical industry.For the first time,this review focuses on the recent advances in the preparation,characterization,physical and functional properties,and potential applications of LBG-based films.

Preparation and characterization of Pt-WO_3/C catalysts for direct ethanol fuel cells

Three co-impregnation/chemical reduction methods in acidic solutions of pH 〈 1,including ethylene glycol （EG）,NaBH4,and HCOOH,were compared for Pt-WO3/C catalysts.Pt-WO3/C catalysts containing 10 wt.% and 20 wt.% platinum per carbon were prepared by the three methods; their morphology and electrocatalytic activities were characterized.The 20 wt.% Pt-WO3/C catalyst prepared by the co-impregnation/EG method presented the optimal dispersion with an average particle size of 4.6 nm and subsequently the best electrocatalytic activity,and so,it was further characterized.Its anodic peak current density for ethanol oxidation from linear sweep voltammetry （LSV） is 7.9 mA·cm^-2,which is 1.4 and 5.2 times as high as those of the catalysts prepared by co-impregnation/NaBH4 and co-impregnation/ HCOOH reduction methods,2.1 times as high as that of the 10 wt.% Pt-WO3/C catalyst prepared by co-impregnation/EG method,respectively.

Preparation and characterization of calcium aluminate by chemical synthesis

Saturated Ca（OH）2 and AlCl3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 m^2/g. The measurement of hydraulic exotherm revealed that the exothennal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.