Effect of sintering parameters on powder injection molded Ti(C, N)-based cermets

Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TRS) and microstructures of powder injection molded Ti(C, N)-based cermets were investigated, by means of Archimedes’s method, three-point bending test and micrographic analysis. The results show that the optimum sintering cycle for powder injection molded Ti(C, N)-based cermets comprises rapid heating (10℃/min) at low temperatures, slow heating (5℃/min) at intermediate temperatures, holding at the highest sintering temperature (1420℃) for a short time (10min), and holding at the second stage (1360℃) for a longer time (6h) to avoid grain coarsening, and that its TRS reaches 624MPa, and there are little pores in their microstructures.

Spark Plasma Sintering Properties of Ultrafine Ti(C,N)-based Cermet

Ultrafine Ti(C,N)-based cermet was sintered by SPS from 1050℃ to 1450℃ and its sintering properties,such as porosity,mechanical properties and phase transformation,were investigated by optical microscopy (OM),scanning electron microscopy (SEM),X-ray diffraction (XRD),and differential scanning calorimeter (DSC).It is found that the spark plasma sintering properties of Ti(C,N)-based cermet differ from those of conventional vacuum sintering.The liquid phase appearance is at least lower by 150℃ than that in vacuum sintering.The porosity decreases sharply below 1 200℃ and reaches minimum at 1 200℃,and afterwards it almost keeps invariable and no longer increases.SPS remarkably accelerates the phase transformation of Ti(C,N)-based cermet and it has a powerful ability to remove oxides in Ti(C,N)-based cermets.Above 1 350℃,denitrification occurred.Fresh graphite phase formed above 1 430℃.Both the porosity and graphite are responsible for the poor TRS.

Two Cobalt(II) Complexes Derived from the Hydrolysis Product of Di-Schiff Base Ligand N,N'-Bis-(1-benzimidazo-2-yl-ethylidene)-ethane-1,2-diamine:Preparation,Characterization and Crystal Structure of the 6-Coordinate Species [CoL_2]X·H_2O (X = ClO_4^-, N

The reactions of Co（C1O4）2·6H2O and Co（NO3）2.6H2O with the di-Schiff base ligand N,N＇-bis-（1-benzimidazo-2-yl-ethylidene）-ethane-1,2-diamine （LA） in ethanol have been investigated. The reactions of LA with excess amount of cobalt salts yield the six-coordinate complexes [CoL2]（ClO4）E·H2O 1 and [CoL2]（NO3）E·H2O 2 as isolatable products （L= N-（1- benzimidazo-2-yl-ethylidene）-ethane-1,2-diamine）, where L is a tri-dentate mono-Schiff base ligand, resulting from the hydrolysis of the precursor di-Schiff base LA. Both complexes were characterized by X-ray crystallography. Crystal data for complex 1： monoclinic, space group P21/c, a = 11.9214（10）, b = 23.5828（17）, c = 14.0387（12）A, β = 135.219（4）°, C22H30Cl2CoN8O9, Mr = 680.37, V = 2780.1（4） A^3 ,Z = 4, Dc = 1.625 g/cm^3,μ（MoKa） = 0.876 mm^-1, F（000） = 1404, the final R = 0.0725 and wR = 0.1530 for 5726 observed reflections （I 〉 2σ（I））. Crystal data for complex 2： monoclinic, space group P21/c, a = 18.2162（16）, b = 10.0610（6）, c = 18.593（2）A, β = 130.099（3）°, C22H30CoN10O7, Mr = 605.49, V = 2606.5（4） A3 Z = 4, Dc = 1.543 g/cm^3,μ（MoKa） = 0.722 mm^-1, F（000） = 1260, the final R = 0.0619 and wR = 0.1429 for 5194 observed reflections （I 〉 2σ（I））. X-ray diffraction analysis reveals that each cobalt atom in the two complexes is chelated by six nitrogen atoms from two tridentate iigands L, exhibiting a slightly distorted octahedral coordination sphere. In both complexes, the strong hydrogen-bonding interactions between the lattice waters and N-H groups of the ligands result in 1D chains which are further connected by ClO4^- （or NO3^-） groups to form a 3D framework. In complex 2, the strong π-π interactions increase the stability of the structure.

A rate-based method for dynamic analysis and optimal design of reactive extraction: n-Hexyl acetate esterification as an example

The dynamic analysis and optimal design of reactive extraction are challenging due to high nonlinearity of model equations and tough decision of judging criteria. In this work, a dynamic rate-based method is developed on g PROMS platform to get easy access to the solutions of reactive extraction with phase splitting. Based on rigorous criteria, dynamic analysis from initial state to final equilibrium(e.g., evolution of phase composition, mass transfer rate and reaction rate) and optimal design of operating conditions(e.g., extractant dosage and feed molar ratio) are achieved. To illustrate the method, the esterification of n-hexyl acetate is taken as an example. The approach proves to be reliable in the analysis and optimization of the exemplified system, which provides instructive reference for further process design and simulation of reactive extraction.

Synthesis, spectral characterization, catalytic andbiological studies of new Ru(II) carbonyl Schiff base complexes of active amines

The synthesis and characterization of several hexa – coordinated Ru(II) complexes of the type [Ru(CO)(B)(L)] (B = PPh3/AsPh3/py/pip;L = di-basic tetradentate ligand derived from the condensation of isatin with diamines) were reported. IR, electronic, 1H- NMR, 31P-NMR of the complexes are discussed. An octahedral geometry has been tentatively proposed for all these complexes. The new complexes have been tested for the catalytic activity in the reaction of oxidation of alcohols in the presence of N-me- thylmorpholine–N-oxide as co-oxidant. The new complexes were also exhibited antimicrobial investigations.

Microstructure and mechanical properties of Ti(C, N)-based cermets with different molybdenum contents

The microstructure and mechanical properties of Ti(C, N)-based cermets with different content Mo were studied. Different Mo contents were added into Ti(C, N)-based cermets. Effect of sintering temperature on mechanical properties of the cermets was also investigated. Specimens were fabricated by conventional powder metallurgy techniques and vacuum sintered at different temperatures. The microstructure and the fracture morphology were investigated using scanning electron microscope. Transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8%. The mechanical properties are the best when the content of Mo is 8% and the sintering temperature is 1450℃.

The MOOC/SPOC Based"1+M+N"Multi-University Collaborative Teaching and Learning Mode:Practice and Experience

Since 2012, the MOOCs, the massive open online courses, have brought big influences on the higher education in the world. How to use MOOCs to help universities rather than bother them to improve their education level and quality becomes an important issue. In China, many universities have explored the new modes and approaches for MOOC/SPOC-based teaching and learning. Especially, the China MOOC Association on Computing Education(CMOOC association), established in 2014, has done a set of successful practice and achieved fruitful experiences on MOOC courses development and computer education reform. Based on the practical experiences, a MOOC/SPOC based "1+M+N" multi-university collaborative teaching and learning mode is presented, which is adapted to the real situation of Chinese university education. In the paper, the practices and experiences of CMOOC association are introduced, the MOOC/SPOC based "1+M+N" multi-university collaborative teaching and learning mode and its approaches are described. Finally, the suggestions for MOOCs development and applications are also presented.

EFFECT OF RARE EARTH ELEMENT Er ON STRENGTHENING OF INTERFACE OF Ti（C，N） BASED CERMETS

ＥＦＦＥＣＴＯＦＲＡＲＥＥＡＲＴＨＥＬＥＭＥＮＴＥｒＯＮＳＴＲＥＮＧＴＨＥＮＩＮＧＯＦＩＮＴＥＲＦＡＣＥＯＦＴｉ（Ｃ，Ｎ）ＢＡＳＥＤＣＥＲＭＥＴＳ￥ＬｉｕＮｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，...

Some Novel Schiff Bases from Pyruvic Acid with Amines Containing N &S Donor Atoms: Synthesis, Spectral Studies and X-Ray Crystal Structures

Four Schiff bases, from pyruvic acid (1) with amines containing N and S donor atoms, thiocarbohydrazide (2, 61%), 2-methyl-3-thiosemicarbazide (3, 26%), S-benzyldithiocarbazate (4, 51%) and S-n-octyldithiocarbazate (5, 63%) have been successfully synthesized. The conventional method was used and a series of novel linear and cyclic Schiff bases were obtained with or without catalyst. All the Schiff bases were fully characterized by CHN elemental analysis, FT-IR, 1H & 13C NMR, EI-MS and two of the Schiff bases were further characterized by X-ray crystallographic structure analysis. Compound 2 crystallizes in the triclinic space group P-1 and unit cell dimensions are: a = 4.1777(8), b = 5.9538(11), c = 13.458(3) Å, α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0439. Compound 3 crystallizes in the orthorhombic space group P n a 2(1) and unit cell dimensions are: a = 5.5992(2), b = 11.3962(5), c = 10.6473(5), α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0285. Compounds 2 and 3 were obtained as cyclic Schiff bases which are triazine derivatives.

Popping of g-C_3N_4 mixed with cupric nitrate: Facile synthesis of Cu-based catalyst for construction of C-N bond

A novel strategy to synthesize copper-based nanoparticles supported on carbon nitride(C3 N4) was developed by popping of mixture containing C3 N4 and cupric nitrate. Characterizations such as X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD) indicate that the structure of g-C3 N4 maintained although a popping process occurred. High resolution transmission electronic microscopy(HRTEM) characterization illustrated that copper-based nanoparticles with diameter of < 1 nm were well distributed on g-C3 N4. This kind of copper catalyst exhibits high catalytic activity and selectivity in arylation of pyrazole, a simple and effect strategy to construct C-N bond in organic chemistry.According to the results of control experiments and characterizations, cuprous oxide should be the catalytic active phase in the supported coperbased catalyst.

Preliminary Studies on Base Substitutions and Repair of DNA Mismatch Damage Stimulated by Low Energy N^+ Ion Beam Implantation in Escherichia coli

Ever since the low energy N+ ion beam has been accepted that the mutation effects of ionizing radiation are attributed mainly to direct or indirect damage to DNA. Evidences based on naked DNA irradiation in support of a mutation spectrum appears to be consistent, but direct proof of such results in vivo are limited. Using mutS, dam and/or dcm defective Eschericha coli imitator strains, an preliminary experimental system on induction of in vivo mutation spectra of low energy N+ ion beam has been established in this study. It was observed that the mutation rates of rifampicin resistance induced by N+ implantation were quite high, ranging from 9.2 x 10~8 to 4.9× 10~5 at the dosage of 5.2×1014 ions/cm2. Strains all had more than 90-fold higher mutation rate than its spontaneous mutation rate determined by this method. It reveals that base substitutions involve in induction of mutation of low energy nitrogen ion beam implantation. The mutation rates of mutator strains were nearly 500-fold (GM2929), 400-fold (GM5864) and 6-fold larger than that of AB1157. The GM2929 and GM5864 both lose the ability of repair DNA mismatch damage by virtue of both dam and dcm pathways defective (GM2929) or failing to assemble the repair complex (GM5864) respectively. It may explain the both strains had a similar higher mutation rate than GM124 did. It indicated that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N+ implantation. The further related research were also discussed.

Effects of Nitrogen Fertilizer Reduction and Application of Nitrogen Fertilizer as Base Fertilizer on Rapeseed Yield and Nitrogen Absorption

[Objective] The aim was to research effects of N fertilizer reduction and application of N fertilizer （as base fertilizer） on rapeseed yield and N absorption. [Method] Based on Ganyouza No.5, the ratio of N, P2O5 andK2O was set at 1：0.5：0.5; N fertilizers were set involving reduced quantity at 150 kg/hm2 and preferred quantity at 180 kg/hm2; 100%, 80% and 60% of N fertilizers were applied as base fertilizers in the test respectively. In general, field tests were conducted to explore effects of reduced N fertilizer and application of N fertilizer as base fertilizer on rapeseed yield and N absorption. [Resalt] When applied N fertilizer as base fertilizer was the same, plant height, stem diameter, length of major inflorescence, number of effective branch, pod number per plant, seed number per pod, and biomass yield in group with preferred N quantity were significantly higher than those in group with reduced N fertilizer. Rapeseed yield and profits in group with preferred N quantity were signifi- cantly higher than those in group with reduced N fertilizer in field with moderate fertili- ty. In fields with higher fertility, however, the two factors were just a little higher. In group with reduced N fertilizer, use efficiency of N fertilizer, N uptake efficiency, par- tial factor productivity and harvest index of N were all significantly higher than those in group with preferred N fertilizer. Agronomic nitrogen use efficiency in group with preferred N fertilizer was significantly higher than that in group with reduced N fertiliz- er in field with moderate fertility and was significantly lower in field with high yield. With amounts of N, P and K fertilizers fixed, economic characters, yield constitution, yield, profits and N absorption in group, where 60% of N fertilizers were applied as base fertilizer, were significantly higher than those in groups with 80% or 100% of base fertilizer （N fertilizers）. These indicated that rational fertilization would maintain rapeseed yield high and reduce N input to improve use efficiency of N fertilizer. On the other hand, it is effective to improve rapeseed yield.＇to reduce N fertilizer to 150 kg/hm2, and application of 60%. of N fertilizers as base fertilizer is still proved optimal at present. [Conclusion] The research provides.theoretioal and technical references for improvement of yield of rapeseed and efficiency of N fertilizer.

Self-assembled three-dimensional carbon networks with accessorial Lewis base sites and variational electron characteristics as efficient oxygen reduction reaction catalysts for alkaline metal-air batteries

Heteroatom-doped carbon has been demonstrated to be one of the most promising non-noble metal catalysts with high catalytic activity and stability through the modification of the electronic and geometric structures.In this study,we develop a novel solvent method to prepare interconnected N,S co-doped three-dimensional（3D）carbon networks with tunable nanopores derived from an asso-ciated complex based on melamine and sodium dodecylbenzene sulfonate（SDBS）.After the intro-duction of silica templates and calcination,the catalyst exhibits 3D networks with interconnected 50-nm pores and partial graphitization.With the increase of the number of Lewis base sites caused by the N doping and change of the carbon charge and spin densities caused by the S doping,the designed N,S co-doped catalyst exhibits a similar electrochemical activity to that of the commercial 20-wt%Pt/C as an oxygen reduction reaction catalyst.In addition,in an aluminum-air battery,the proposed catalyst even outperforms the commercial 5-wt%Pt/C catalyst.Both interconnected porous structures and synergistic effects of N and S contribute to the superior catalytic perfor-mance.This study paves the way for the synthesis of various other N-doped and co-doped carbon materials as efficient catalysts in electrochemical energy applications.

Microstructure and shear strength of the brazed joint of Ti(C,N)-based cermet to steel

Firm joins were obtained between Ti（C,N）-based cermet and steel with Ag-Cu-Zn-Ni filler metal by vacuum brazing. The effects of technological parameters such as brazing temperature, holding time, and filler thickness on the shear strength of the joints were investigated. The microstructure of welded area and the reaction products of the filler metal were examined by scanning electron microscopy （SEM）, metallographic microscope （OM）, energy-dispersive X-ray analysis （EDS）, and X-ray diffraction （XRD）. The brazing temperature of 870℃, holding time of 15 min, and filler thickness of 0.4 mm are a set of optimum technological parameters, under which the maximum shear strength of the joints, 176.5 MPa, is achieved. The results of microstructure show that the wettability of the filler metal on Ti（C,N）-based cermet and steel is well. A mutual solution layer and a diffusion layer exist between the welding base materials and the filler metal.

Comparative study of the fabrication of ultrafine Ti(C,N)-based cermets by spark plasma sintering and conventional vacuum sintering

Spark plasma sintering (SPS) and conventional vacuum sintering (VS) wereemployed to fabricate ultrafine Ti(C,N)-based cermets. The shrinkage behavior, microstracture, andporosity and mechanical properties of the samples fabricated by SPS were compared with those of thesamples sintered by VS using optical microscopy, scanning electron microscopy, universal testingmachine, and rockwell tester. The results are as follows: (1) The shrinkage process occurred mainlyin the range of 1000-1300 deg C during the VS process, and only a 0.2 percent linear shrinkage ratioappeared below 800 deg C; during the SPS process, a 60 percent dimensional change occurred below800 deg C as a result of pressure action. (2) By utilizing the SPS technique, it is difficult forobtaining fully dense Ti(C,N)-based cermets. Due to the much existence of pores and un-combinedcarbon, the mechanical properties of the sintered samples by SPS are inferior to sintered ones byVS. (3) grain size of the samples sintered by SPS is still below 0.5 urn, but not by VS; because oflow sintering temperature, there are no typical core/rim structures formed in the sintered samplesby SPS1; the main microstructures of the sintered samples by SPS2 are a white core/grey shellstructure, whereas by VS show a typical black core/grey shell structure.

New Schiff Bases from 6,6’-Diformyl-2,2’-Bipyridyl with Amines Containing O, S, N and F: Synthesis and Characterization

Eight novel Schiff Bases, from 6,6′-diformyl-2,2′-bipyridyl (1a, 43%)with O, N, S and F containing amines: Thiosemicarbazide (2a, 70%), 4-Ethyl-3-thiosemicabazide (2b, 75%), 4,4-Dimethyl-3-thio-semicarbazide (2c, 75%), S-benzyldithiocarbazide, SBDTC (2d, 80%), (Trifluromethyl) phenylhy-drazine (2e, 80%), 4-Phenyl-3-thiosemcarbazide (2f, 80%), Thiocarbazide (2g, 70%), 2-Amino-thiophenol (2h, 65%), have been synthesized. The conventional method of synthesis of the Schiff bases involves refluxing the reaction mixture containing the diformyls and amines for 1 hour. The solid products that had formed were filtered off using suction filtration. In few reactions, 2 - 3 drops of conc. sulfuric acid were used to obtain high yield. The structures of all eight novel synthesized compounds have fully been characterized by spectroscopic (IR, NMR, MS) methods.

Synthesis and Characterizations of New Ferrocenyl Schiff Base with NLO Responses

A series of new stable (thermal and photochemical) ferrocenyl derivatives containing C=N bond and benzene ring in long conjugated chains have been synthesized and characterized by (HNMR)-H-1(400MHz), IR, and elemental analysis. Pull-push ferrocenyl complexes that we have prepared have strong NLO responses identified by electronic absorption spectrum.

Effects of molybdenum on the microstructure and mechanical properties of Ti(C,N)-based cermets with low Ni

The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets. Specimens were fabricated by conventional powder metallurgy and vacuum sintered at temperatures of 1440, 1450, and 1460℃ individually. The microstructure and fracture morphology were investigated by scanning electron microscope, and the mechanical properties such as transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8 wt.%; the mechanical properties of the specimens sintered at 1450℃ are better than those sintered at 1440 and 1460℃. The integrated properties of transverse strength and hardness are the best when the content of Mo is 8 wt.% and the sintering temperature is 1450℃.

Microstructure and cutting performance of Ti(C, N)-based cermets heat-treated in nitrogen

Ti（C, N）-based cermets were treated using hot isostatic pressing （HIP） at 1423 K in nitrogen. The microstructures compared with the as-sintered cermets were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, and electron microprobe analysis. It was found that high nitrogen activity in the surface zone resulted in the formation of gradient structure. Approximately 20-1am-deep, nitrogen-rich and titanium-rich hard surface zone was introduced by the heat treatment. The nitrogen activity was the driving force that caused the transportation of the atoms through the binder, titanium towards the surface, and tungsten and molybdenum inwards. In the surface zone, the particle size became fine, the inner rim disappeared, and the volume fraction of the outer rim and the binder phase considerably reduced. Small grains of TiN, WC, Mo2C, and nitrogen-rich carbonitlide phases formed in the surface zone during the heat treatment, improving the tlibological property of the heat-treated cermet.

硅胶键合N-丙基哌嗪n-丙酸钠作为可循环使用催化剂催化4H-吡喃衍生物合成(英文)

Silica‐bonded N‐propylpiperazine sodium n‐propionate(SBPPSP) was found to act as an efficient solid base for the preparation of a series of 4H‐benzo[b]pyran derivatives. SBPPSP was used as a recyclable heterogeneous solid base catalyst for the synthesis of 3,4‐dihydropyrano[c]chromenes, 2‐amino‐4H‐pyrans, 1,4‐dihydropyrano[2,3‐c]pyrazoles, and 2‐amino‐4H‐benzo[e]‐chromenes via the condensation reaction of dimedone, ethyl acetoacetate, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐ one, and α‐naphthol, respectively, with aromatic aldehydes and malononitrile in refluxing aqueous ethanol. The heterogeneous solid base showed similar efficiency when reused in consecutive reactions.