Applied Catalysis A:General 507(2015)75–81
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Applied Catalysis A:
General
j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /a p c a t
a
Effect of ZrO 2,Al 2O 3and La 2O 3on cobalt–copper catalysts for higher alcohols synthesis
Zi Wang,James J.Spivey ?
Department of Chemical Engineering,Louisiana State University,Baton Rouge,LA 70803,USA
a r t i c l e
i n f o
Article history:
Received 22June 2015Received in revised form 15September 2015
Accepted 22September 2015
Available online 26September 2015
Keywords:
Higher alcohols synthesis Syngas Cobalt Copper
Metal oxide promoters
Modi?ed Fischer–Tropsch catalysts
a b s t r a c t
Three cobalt–copper catalysts singly promoted with La,Zr,or Al were studied for catalytic conversion of syngas to higher alcohols.The properties of the promoted catalysts have been characterized by TPR,XRD,XPS and BET.CO hydrogenation was carried out in a plug-?ow reactor under 30bar,GHSV =36000scc/g cat /h,H 2/CO =2,and 250?C at differential conversions.The catalyst activity and selectivity to higher alcohols are greatest on CuCoLa 2O 3:ethanol selectivity 10.5%at a conversion of 0.76%.During 9h of time-on-stream,CO conversion decreased on CuCoLa 2O 3while methanol and higher alcohol selectivity increased.The behaviors on CuCoZrO 2and CuCoAl 2O 3were different.On these two catalysts,CO con-version and selectivity reached a near-steady state much more quickly than CuCoLa 2O 3.These results suggest changes on CuCoLa 2O 3that increase the selectivity for oxygenates continue with time,at least over the time scale investigated here.
?2015Published by Elsevier B.V.
1.Introduction
Increasing demand has focused on renewable and environmen-tally benign energy sources for the catalytic conversion of biomass-,natural gas-,and coal-derived syngas to liquid fuel.An alternative to producing long-chain hydrocarbon products via Fischer–Tropsch (FT)synthesis is the conversion of syngas into more valuable higher alcohols.These higher carbon-number alcohols can be used as hydrogen carriers for fuel cells,or as additives directly blended into gasoline [1,2].However,additional research is required before extrapolating lab-scale studies to industry-level application.Cur-rently,it is dif?cult to commercialize this process due to relatively low activity,yield and stability of the catalysts.Rh-based catalysts have shown high yield to higher alcohols in CO hydrogenation,with net yields typically ranging from 10to 20%[3–6].However,the rel-atively high price of these catalysts has limited the development of more practical processes [7].Among all the non-noble metal based catalysts,cobalt–copper modi?ed Fischer Tropsch catalysts are promising substitutes for noble metal-based catalysts [8–11].Recent studies have shown that promoters can increase the selectivity of Co–Cu catalysts to oxygenates.The Institut Francais
?Corresponding author at:Department of Chemical Engineering,Louisiana State University,S.Stadium Drive,Baton Rouge,LA 70803,USA.Fax:+12255781476.
E-mail address:jjspivey@https://www.doczj.com/doc/3a14605380.html, (J.J.Spivey).
du Petrole (IFP)?led a number of patents on the development of cobalt–copper based modi?ed Fischer Tropsch catalysts for higher alcohols synthesis [8,12–16].Under moderate operating condi-tions,the selectivity to higher alcohols ranged from 20%to 70%.The ethanol yield over Cu–Co-based catalysts ranged from 100to 300mg/(g cat h),suggesting commercial interest in these catalysts.Following the IFP work,a wide range of studies on Co–Cu bimetallic catalysts are reported to further increase the selectivity to higher alcohols [10,17,18].Researchers correlate the activity and selectiv-ity of the catalysts with the type of synthesis method,the alkali promoters used,and physicochemical properties of the catalysts such as metal particle sizes,dispersions,and the atomic proximity of cobalt and copper.
Speci?cally,metal oxide promoters such as ZrO 2,La 2O 3and Al 2O 3greatly affect the reduction and product selectivity of cobalt–copper-based catalysts.For instance,ZrO 2assists the reduc-tion of Co 2+species to metallic cobalt for CO hydrogenation,and ZrO 2promoted catalysts show increased selectivity to ethanol [19].According to Lebarbier et al.[20],La 2O 3-supported cobalt cata-lyst reached almost complete cobalt reduction after H 2treatment,and cobalt dispersion on La 2O 3supported catalyst was higher than those on activated carbon and Al 2O 3.Alumina-supported cobalt FT catalysts show greater stability,high activity and strong metal-support interactions comparing with TiO 2and MgO [21,22].A study of alumina-supported copper–cobalt bimetallic catalysts for CO hydrogenation by Wang et al.[23]reported increased interaction
https://www.doczj.com/doc/3a14605380.html,/10.1016/j.apcata.2015.09.0320926-860X/?2015Published by Elsevier B.V.
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between cobalt and copper particles on a?-Al2O3supported cat-alyst compared with unpromoted catalysts,which improved the selectivity of the catalysts to higher alcohols.Past work shows that the choice of the metal oxide promoters greatly in?uences catalyst morphology,cobalt–copper interaction,and reduction or reaction performance.These metal oxides also promote cobalt–copper cat-alysts in activity and selectivity to ethanol and other oxygenates.
Therefore,the purpose of this work is to study zirconia,alumina and lanthana as metal oxide promoters for cobalt–copper higher alcohols synthesis catalysts.In the present study,cobalt and copper salts are coprecipitated with the third metal salt(Zr,Al or La)to syn-thesize three promoted catalysts,denoted as CuCoZrO2,CuCoAl2O3, and CuCoLa2O3.Coprecipitated metal oxides serve as supports to maintain highly dispersed metal clusters that contain both cobalt and copper particles.The promoting effects of these metal oxides are measured by H2temperature-programmed reduction,X-ray diffraction,X-ray photoelectron spectroscopy,BET surface area, and CO hydrogenation activity studies.The aim of this study is to directly compare the promoting effects of the metal oxides on the activity,selectivity,and stability of these catalysts for higher alcohols synthesis.
2.Experimental
2.1.Catalyst preparation
Catalysts were prepared by pH-coprecipitation method. In the coprecipitation method,cobalt nitrate,copper nitrate and corresponding metal salts(Al(NO)3·9H2O,ZrO(NO3)2,or La(NO3)3·6H2O)were dissolved together in deionized water.The molar ratio of Cu nitrite to Co nitrite to metal salts was kept at 2:2:1.The solution were titrated to100ml water under magnetic stirring at80?C.Meanwhile,a solution of ammonia carbonate was titrated in order to maintain the pH at7.00±0.2.After the titra-tion,the solution was aged at room temperature for6h,then the solid was recovered by washing and?ltration.Collected precipi-tates were dried at90?C for24h,then calcined at500?C for3h under air?ow.The samples are denoted as CuCoAl2O3,CuCoLa2O3 and CuCoZrO2to demonstrate the promoters used in the catalysts.
https://www.doczj.com/doc/3a14605380.html,position and surface area
The compositions of the calcined catalysts were determined by inductively coupled plasma optical emission spectrometry(ICP-OES)method using a PerkinElmer2000DV ICP-optical emission spectrometer.
BET surface area of freshly calcined catalyst were determined by N2adsorption at?196?C.Prior to analysis,the samples were treated in helium?ow at150?C for30min to remove the moisture. A?ow BET procedure using N2concentrations of10%,20%,and30% in a He carrier was used in an Altamira AMI-200system.
2.3.Hydrogen temperature programmed reduction(H2-TPR)
H2-TPR was done on50mg of calcined catalyst in an Altamira AMI-200system.50mg of calcined catalysts were pretreated in Helium?ow at150?C for30min to remove moisture.Reducing gas of50sccm10%H2/Ar?owed through the reactor as the temperature increased at5?C/min to550?C.A thermal conductivity detector (TCD)monitored the consumption of H2.A calibration using TPRs of20,35and50mg Ag2O allowed quantitative analysis of hydrogen uptake by the catalysts.2.4.In situ X-ray diffraction(XRD)
XRD measurements of the catalysts were done at the Center for Nanophase Materials Science at Oak Ridge National Laboratory. Catalyst Samples were loaded into an Anton Paar XRK900reac-tor chamber.A4%H2/He gas was?owed through the chamber to conduct the reduction process,and a PANalytical X’Pert Pro MPD diffractometer with Cu K?radiation( =0.15406nm)was used to record XRD patterns at different temperatures.The spectra were collected from15?to70?with a step size of0.0167?.X’pert High-Score Plus were used to identify phases by the Search&Match feature.
2.5.X-ray photoelectron spectroscopy(XPS)
XPS experiments on calcined catalysts were performed on a Kratos AXIS165X-Ray Photoelectron Spectrometer using monochromatic Al K?1radiation(h =1486.6eV,intrinsic linewidth0.3eV).The pressure in the analysis chamber was kept between10?8and10?9Torr during the experiments.Survey spec-tra with a pass energy of160eV were taken on each sample prior to the measurement to check correct sample alignment.High res-olution scans of Co2p,Cu2p,C1s,O1s,Al2p,La3d and Zr3d were recorded with a pass energy of40eV.C1s peak at284.8eV were used as known standard to calibrate binding energy scale.
2.6.Reaction studies
Reactions were carried out in an Altamira AMI-200R-HP sys-tem equipped with a1/4-in.glass-lined stainless steel reactor tube. 50mg of calcined sample was reduced in a mixture of H2and He for 3h at a standard temperature400?C.After reduction,the reactor was cooled to room temperature in He,then pressurized to30bar and heated to250?C.At this point,He is switched by a simulated-syngas?ow(space velocity=36000scc/g cat/h,H2/CO=2).Products were analyzed in a Shimadzu GC2014gas chromatograph with ?ame ionization and thermal conductivity detectors(FID and TCD). Reaction data was measured continuously until the results are steady.
The reactions were carried out at differential conversion(CO conversion<3%).This minimizes deactivation as well as tempera-ture and concentration gradients in the reactor.This also eliminates the need to capture and analyze a liquid,integral sample over extended periods of time,which does not measure any changes in the product composition with time.
2.7.Temperature programmed oxidation(TPO)coupled with
mass spectroscopic measurements on used catalysts
After the reaction,the samples were purged in He for30min at25?C.The reactor was then heated to750?C at15?C/min in 30sccm10%O2/He?ow.The pro?les of CO2evolution(m/z=44) were collected by an Ametek Quadrupole MS.
3.Results and discussion
https://www.doczj.com/doc/3a14605380.html,position and surface area
ICP-OES Sample composition and BET surface area results are listed in Table1.CuCoAl2O3showed the highest surface area(94.1m2/g),while CuCoLa2O3had the lowest surface area (49.7m2/g).Bulk Co and Cu composition by ICP-OES are shown in Table1.Note that the molar ratios of Co:Cu:metal oxides are intentionally kept as2:2:1for all three catalysts.
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Table 1
Catalyst composition by ICP-OES and BET surface area.a
Catalyst
Composition (wt%)
Cu/Co molar ratio
Surface area m 2/g
Co
Cu
CuCoAl 2O 326.632.0 1.1194.1CuCoLa 2O 318.823.3 1.1449.7CuCoZrO 2
25.7
30.4
1.09
88.8
a
The molar ratio of Cu:Co:metal oxide(Al 2O 3,La 2O 3and ZrO 2)=
2:2:1.
Fig.1.TPR results for CuCOZrO 2,CuCoAl 2O 3and CuCoLa 2O 3from 70?C to 550?
C.
3.2.TPR
Temperature programmed reduction pro?les obtained for the three catalysts are shown in Fig.1.
All three catalysts displayed similar reduction behavior between 185?C and 250?C.For CuCoZrO 2,the ?rst shoulder at ～190?C is attributed to the reduction of CuO to Cu 0.The peak at around 200?C and the shoulder at 230?C correspond to the two-step reduction of Co 3O 4to CoO and CoO to Co 0.CuCoAl 2O 3has a similar reduc-tion behavior.The broad shoulder from 250?C to 350?C in both CuCoZrO 2and CuCoAl 2O 3are due to the reduction of residual CoO to metallic cobalt.
The CuCoLa 2O 3reduction pro?le is somewhat different.Although the same reduction of copper at ～190?C is seen,the fea-ture at 215?C shows an asymmetric peak for CuCoLa 2O 3,which can be assigned as the combination of Co 3O 4to CoO and CoO to Co 0reduction.The broad shoulder above 250?C,associated with the extended reduction of cobalt due to less easily reduced cobalt for the Zr-and Al-promoted catalysts,is not seen on CuCoLa 2O 3.This is probably because of higher dispersion of Cu–Co particles and stronger interaction between cobalt and copper in La-promoted catalysts,consistent with the literature.The promoting effect of H 2reduction by hydrogen spillover mechanism associated with La 2O 3has been reported on lanthanum promoted cobalt catalysts before [20],therefore,the possibility that La 2O 3promoted the reduction of cobalt in CuCoLa2O3catalyst cannot be ruled out.
Table 2shows the experimental and expected hydrogen con-sumption during the TPR.Reduction of cobalt and copper is essentially complete up to 250?C on all three promoted catalysts,with CuCoAl2O3being slightly less reduced (92.7±2.0)than for the other two (97.5±1.2and 96.4±1.6).This is consistent with literature that ZrO 2and La 2O 3facilitate H 2reduction of cobalt and
Table 2
Quantitative H 2consumption during TPR.a
Catalyst
H 2consumed (?mol/g)
Expected consumption (?mol/g)Metal reduced%CuCoAl 2O 3291±631492.7±2.0CuCoLa 2O 3235±324197.5±1.2CuCoZrO 2
294±5
305
96.4±1.6
a
Errors in the H 2consumption values are within 95%con?dence interval.
Table 3
XPS binding energies and surface composition analysis.
Catalyst
Binding energies
Cu/Co atomic ratio by XPS
Cu/Co atomic ratio by ICP
Cu 2p3/2
Co 2p3/2
CuCoAl 2O 3933.8779.7 1.17 1.11CuCoLa 2O 3933.6779.5 1.23 1.14CuCoZrO 2933.6
779.8
1.09
1.09
copper oxides,leading to more complete reduction of the CuCoZrO 2and the CuCoLa 2O 3than the CuCoAl 2O 3catalyst [9,19].
3.3.In situ X-ray diffraction
XRD patterns of the three catalysts during H 2-reduction are shown in Fig.2.For CuCoAl 2O 3,the fresh,calcined catalyst include Co 3O 4and CuO (Fig.2(a)).At 200?C,the intensity of the peaks for Co 3O 4and CuO had decreased,and metallic phases at 43.2?and 50.3?begin to appear.Meanwhile,a peak at 61.8?emerged,which indicates the existence of a CoO phase was apparent at 300?C,but disappeared at 400?C.Only metallic phases are present at 400?C.
The results of the in-situ XRD combined with the TPR patterns clearly show that reduction of CuO starts at ～185?C.The expected reduction sequence of copper and cobalt oxides to reduced met-als is apparent in the loss of the crystalline oxides and appearance of the reduced metals.The long shoulders from 250?C to 350?C in the CuCoZrO 2and CuCoAl 2O 3that are seen in the TPR are not easily distinguished in the XRDs from the CuCoLa 2O 3.At 400?C,all three catalysts are fully reduced.Based on the width of the peaks of all three catalysts,copper clusters are more crystalline than cobalt clusters,which are quite amorphous.
CuCoLa 2O 3and CuCoZrO 2had reduction patterns similar to CuCoAl 2O 3.CuCoLa 2O 3had a tilted background due to a higher dispersion of Co 3O 4and CuO clusters (Fig.2(b)).This is consistent with the TPR results,which did not show a broad shoulder above ～250?C.CuCoZrO 2displayed minor CuO features below 200?C,which indicates the existence of both crystalline and amorphous copper oxide in the calcined catalyst.Signi?cantly,there is no peak that could be directly attributed to cobalt aluminate or lanthanum cobalt oxides,but the possibility of forming cobalt-metal oxides in the catalysts cannot be ruled out.
3.4.XPS
XPS studies of calcined samples were carried out in order to study the chemical state of the elements at catalyst surface,and determine surface metal compositions.The XPS spectra of the three fresh,calcined catalysts for Co (2p 3/2)and Cu(2p 3/2)are shown in Fig.2(d)and (e),respectively.Co 2p 3/2peak located at 779.3eV for all three samples,which shows that cobalt is in the form of Co 3O 4on the surface [18,19].The Cu 2p 3/2main peak is positioned at 933.6eV with a shake-up satellite peak accompanied at 942eV,thus copper ions on the surface for all three catalysts are in the form of CuO [24],as expected.
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Fig.2.Characterization on calcined CuCoAl 2O 3,CuCoLa 2O 3and CuCoZrO 2samples by XRD and XPS.(a)XRD patterns during reduction in 4%H 2/He at indicated temperatures for CuCoAl 2O 3;(b)XRD patterns during reduction in 4%H 2/He at indicated temperatures for CuCoLa 2O 3;(c)XRD patterns during reduction in 4%H 2/He at indicated temperatures for CuCoZrO 2;(d)XPS spectra of Co 2p region for CuCoAl 2O 3,CuCoLa 2O 3and CuCoZrO 2sample (e)XPS spectra of Cu 2p region for CuCoAl 2O 3,CuCoLa 2O 3and CuCoZrO 2sample.
Table 3summarizes copper and cobalt binding energies of the samples surfaces.Surface and bulk Cu/Co atomic ratios calculated by XPS and ICP respectively are also shown in Table 3.Although CuCoAl 2O 3and CuCoLa 2O 3show slightly higher Cu/Co atomic ratio on the surface than in the bulk,these results indicate that all three samples are composed of relatively uniform particles with a con-stant atomic ratio of cobalt and copper.
3.5.Catalyst activity test
Fig.3shows the CO conversion as a function of time-on-stream at 250?C and 30bar.Note that all CO conversions are intention-ally kept at differential CO conversion (<3%)to avoid condensation (Section 2.6).
CuCoAl 2O 3had highest activity under reaction condition.While CuCoZrO 2and CuCoLa 2O 3had much lower activity.CuCoAl 2O 3
and CuCoZrO 2slightly lost activity in the ?rst two hours of reac-tion,then reaching near steady-state after 2–3h of operation.For CuCoLa 2O 3catalyst,however,CO conversion decreased with time over the 9h of operation.
Fig.4shows the changes of product selectivity with time.For CuCoZrO 2and CuCoAl 2O 3,the selectivity to alcohols and C 2+products were relatively stable through 9h of reaction,whereas methane selectivity slightly increased with time.Nevertheless,CuCoLa 2O 3displays more signi?cant changes of the selectivity to C 2+products.The most striking fact is the increase of methanol and ethanol selectivity at 250?C with time.At this temperature,the selectivity to ethanol increased from 6.5%to 10.5%and the selectivity to methanol had increased from 5%to 16.9%after 9h on stream.The increased alcohols selectivity is associated with a small decrease of ethane and propane selectivity.
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Fig.3.CO conversion as a function of time on stream of CuCoLa2O3,CuCoZrO2& CuCoAl2O3at250oC,30bar,and GHSV=36000scc/g cat/h.
CuCoLa2O3shows increased selectivity of methanol and decreased selectivity of methane with time.Methane is synthesized from dissociated CO while methanol is formed from associatively adsorbed CO[25].Therefore,the increase of methane and the decrease of methanol selectivity indicate the increase of associa-tively adsorbed CO and the decrease of dissociatively adsorbed CO with time.
The product selectivity distribution for the three catalysts over 9h time-on-stream is shown in Table4.At250?C,CuCoLa2O3 catalyst showed highest selectivity to ethanol among the three catalysts,CuCoZrO2and CuCoAl2O3had similar selectivity toward ethanol,C2+oxygenates and C2+hydrocarbons.Table4shows that CuCoLa2O3is less selective to C2+hydrocarbons,which means Fischer–Tropsch synthesis in the reaction is inhibited on CuCoLa2O3,leading to higher methanol and ethanol selectivity of CuCoLa2O3catalyst.In general,CuCoAl2O3has properties very sim-ilar to traditional Fischer–Tropsch catalysts,with a high selectivity to methane and C2+hydrocarbons.CuCoZrO2also favors C2+hydro-carbons,but produces more C2+oxygenates than CuCoAl2O3.This could be due to the reason that ZrO2provide more basic sites than Al2O3,which suppress hydrocarbon selectivity and favor oxy-genates formation[26].
CuCoLa2O3shows signi?cantly greater selectivity to methanol and C2+oxygenates than CuCoZrO2or CuCoAl2O3.There is a dif-ference between the formation of methanol and C2+oxygenates. Methanol is formed by the hydrogenation of associatively adsorbed CO,while C2+oxygenates are formed by the hydrogenation of atom-ically adjacent sites,one of which is a CH x moiety produced from dissociatively adsorbed CO and one of which is formed by associa-tively adsorbed CO.These two moieties then form the?rst C-C bond, from which C2+oxygenates are produced[2,27].The relative rates of the formation of these two moieties produces the observed prod-uct selectivities––e.g.C2+oxygenates.The relatively high methane selectivity is consistent with the mechanism in which hydrogena-tion of dissociatively adsorbed CO on cobalt sites is faster than C-C bond formation to C2+oxygenates.
From characterization results,there are no major differences in reduction behavior and surface distribution among the three cat-alysts.This suggests that change of selectivity with time is due to reconstruction of the surface on the CuCoLa2O3catalyst that produces sites favorable to alcohols—both methanol and C2+oxy-genates.Such surface reconstruction of cobalt-copper particles in the presence of syngas has been reported by Xiang et al.[28],who showed major Co surface segregation of the Co–Cu particles took place during syngas exposure,and an“onion-like”graphitic car-bon shell was observed on the particle surface.Lebarbier et al.[20] reported the effect of La2O3on cobalt catalysts,claiming that expo-sure to CO leads to the formation of Co2C on the surface,thus
Co Fig.4.Selectivity changes as a function of time on stream on CuCoLa2O3,CuCoZrO2 and CuCoAl2O3during reaction at250?C.
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Table 4
Activity &products selectivity for CuCoAl 2O 3,CuCoLa 2O 3and CuCoZrO 2at 250?C and 30bar.a
Catalyst
Carbon selectivity
CO conversion (%)
Methane
Methanol
Ethanol
C 3–6oxygenates
C 2–6hydrocarbon
CO 2CuCoAl 2O 335.63 5.02 5.66 2.3826.0623.25 1.93CuCoLa 2O 331.3716.9210.467.4714.4518.030.76CuCoZrO 2
28.14
4.35
7.32
6.09
29.63
22.67
0.58
a
Selectivity and CO conversion were taken at near steady state after 9h of
reaction.
Fig.5.TPO of CuCoLa 2O 3,CuCoZrO 2and CuCoAl 2O 3after CO hydrogenation reaction at 250?C for 9h.
exists in both metallic Co and Co 2C phase.Reaction studies showed slightly increase in the alcohol selectivity was observed for the sample with highest Co 2C/Co 0ratio on the surface.Furthermore,Volkova et al.[29]proposed that Co 2C is able to activate CO asso-ciatively and insert CO into (CH x )ads species that lead to higher alcohols.On CuCoLa 2O 3here (Fig.4),the selectivity to C 2+hydro-carbons decreases while methanation rate increases,which could be caused by the formation of surface carbon or Co 2C [30].The for-mation of carbon or cobalt carbide will decrease catalyst activity and increase methane selectivity [31,32].
Fig.5shows the TPO results to measure any carbon deposition on used CuCoLa 2O 3,CuCoZrO 2and CuCoAl 2O 3catalysts after 9h of reaction.The amount of carbon on the used CuCoZrO 2was much more than CuCoLa 2O 3or CuCoAl 2O 3.This clearly suggests that the relative low activity of the CuCoZrO 2is due to carbon deposition.
CuCoZrO 2and CuCoAl 2O 3shows similar TPO peaks between 200?C and 295?C,but with much more of this carbon on CuCoZrO2,as measured by the area under the TPO peaks.CuCoLa 2O 3shows a shoulder at 230?C,a larger peak at 320?C and another peak at 565?C.Literature attributes the peaks in the 200–300?C region to the oxidation of polymeric carbon species for all three catalysts [33–35].Cobalt carbide decomposes above 300?C [36],there-fore,the peak around 320?C on the CuCoLa 2O 3catalyst can be assigned to the decomposition and oxidation of cobalt carbide.The CuCoLa 2O 3peak at 565?C corresponds to the decomposition of graphitic carbon on the surface [37,38].
Lanthanum promoter in CuCoLa 2O 3seems to play a vital role in promoting the surface reconstruction and changing the prod-uct selectivity to favor alcohols.More in-situ characterizations are required to study the mechanism of surface reconstruction and for-mation of intermediates during syngas exposure,which will help us to further increase higher alcohols selectivity in CO hydrogena-tion reaction.The selectivity to ethanol and higher alcohols can also be further increased by adjusting reaction conditions.For instance,changing the H 2/CO ratio to 1/1will decrease the methane and the methanol selectivity and favor the higher alcohols synthesis [1,25].
4.Conclusion
No major difference in the catalyst reduction behavior is observed for these promoted catalysts during the TPR.The reduc-tion of cobalt and copper are completed for all the catalysts by 300?C,which is consistent with literature.XRD results show CuO and Co 3O 4phases in the fresh,calcined catalysts.The samples show uniform particles which have the same Cu/Co ratios on the sur-face and in the bulk.In the activity tests,CuCoAl 2O 3displayed highest CO conversion,while CuCoLa 2O 3yielded much higher car-bon selectivity to methanol (16.9%)ethanol (10.5%)than the other two tests.All three catalysts showed changes with time-on-stream,with more signi?cant increases in methanation and methanol for-mation compared to other products.Increases in selectivity were particularly signi?cant for CuCoLa 2O 3,suggesting the existence of surface reconstruction and intermediate formation on the surface during the exposure of syngas.Post-reaction TPO detected poly-meric carbon on all used catalysts,while CuCoZrO 2showed highest polymeric carbon accumulation.TPO also showed the existence of cobalt carbide on spent CuCoLa 2O 3.
The addition of the three metal promoter oxides leads to signi?cant differences.Speci?cally,the C 1–C 6alcohol selectivity for the CuCoLa 2O 3(34.9%)is far greater than either CuCoAl 2O 3(13.1%)or CuCoZrO 2(17.8%).This suggests fundamental reasons for CuCoLa 2O 3,Perhaps the surface basicity is increased by lan-thanum oxide to favor alcohols formation [39].Another difference for CuCoLa 2O 3is the hydrocarbon selectivity.The difference in C 2–C 6hydrocarbon selectivity between the CuCoAl 2O 3(26.0%)and CuCoZrO 2(29.6%)on one hand,and CuCoLa 2O 3on the other hand (14.4%)appears to re?ect that on CuCoLa 2O 3the relative rates of the hydrogenation of surface CH x ,to hydrocarbons is lower than the relatively rates of the hydrogenation of the CO ads -CH x bond to C 2+alcohols [2,17,25].The metal promoter oxides studied here clearly affect the formation of the ?nal products on the associative and dissociative adsorption sites,and La in particular promotes the selectivity to oxygenates versus hydrocarbons.
Z.Wang,J.J.Spivey/Applied Catalysis A:General507(2015)75–8181
Acknowledgements
This material is based upon work supported as part of the Center for Atomic Level Catalyst Design,an Energy Frontier Research Cen-ter funded by the US Department of Energy,Of?ce of Science,Of?ce of Basic Energy Sciences under Award Number DE-SC0001058.A part of this study was conducted at the Center for Nanophase Material Sciences,which is sponsored at Oak Ridge National Lab-oratory by the division of Scienti?c User Facilities,US Department of Energy.The authors are thankful to Dr.Viviane Schwartz and Dr.Jong Kahk Keum for setting up in situ XRD experiments.The help of Kimberly Hutchison from North Carolina State Univer-sity,Department of Soil Science on ICP-OES analysis is gratefully acknowledged.
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特种陶瓷材料的制备工艺 10材料1班 王俊红，学号：1000501134 摘 要：介绍粉末陶瓷原料的制备技术、特种陶瓷成形工艺、烧结方法。 目前，特种陶瓷中的粉末冶金陶瓷工艺已取得了很大进展，但仍有一些急需解决的问题。 当前阻碍陶瓷材料进一步发展的关键之一是成形技术尚未完全突破。 压力成形不能满足形状复杂性和密度均匀性的要求。 多种胶体原位成形工艺，固体无模成形工艺以及气相成形工艺有望促使陶瓷成形工艺获得关键性突破。 关键词：特种陶瓷；成形；烧结；陶瓷材料 前言：陶瓷分为普通陶瓷和特种陶瓷两大类， 特种陶瓷是以人工化合物为原料（如氧化物、氮化物、碳化物、硼化物及氟化物等）制成的陶瓷。 它主要用于高温环境、机械、电子、宇航、医学工程等方面，成为近代尖端科学技术的重要组成部分。 特种陶瓷作为一种重要的结构材料，具有高强度、高硬度、耐高温、耐腐蚀等优点，无论在传统工业领域，还是在新兴的高技术领域都有着广泛的应用。 因此研究特种陶瓷制备技术至关重要。 正文：特种陶瓷的生产步骤大致可以分为三步：第一步是陶瓷粉体的制备、第二步是成形，第三步是烧结。 特种陶瓷制备工艺流程图 一、 陶瓷粉体的制备 粉料的制备工艺(是机械研磨方法，还是化学方法)、粉料的性质(粒度大小、形态、尺寸分布、相结构)和成形工艺对烧结时微观结构的形成和发展有着巨大的影响，即粉末制备 坯料制备 成型 干燥 烧结 后处理 热压或热等静压烧结 成品
陶瓷的最终微观组织结构不仅与烧结工艺有关，而且还受粉料性质的影响。由于陶瓷的材料零件制造工艺一体化的特点，使得显微组织结构的优劣不单单影响材料本身的性能，而且还直接影响着制品的性能。陶瓷材料本身具有硬、脆、难变形等特点。因此，陶瓷材料的制备工艺显得更加重要。由于陶瓷材料是采用粉末烧结的方法制造的，而烧结过程主要是沿粉料表面或晶界的固相扩散物质的迁移过程。因此界面和表面的大小起着至关重要的作用。就是说，粉末的粒径是描述粉末品质的最重要的参数。因为粉末粒径越小，表面积越大，单位质量粉末的表面积(比表面积)越大，烧结时进行固相扩散物质迁移的界面就越多，即越容易致密化。制备现代陶瓷材料所用粉末都是亚微米(＜lμm)级超细粉末，且现在已发展到纳米级超细粉。粉末颗粒形状、尺寸分布及相结构对陶瓷的性能也有着显著使组分之间发生固相反应，得到所需的物相。同时，机械球磨混合无法使组分分的影响。粉末制备方法很多，但大体上可以归结为机械研磨法和化学法两个方面。 传统陶瓷粉料的合成方法是固相反应加机械粉碎(球磨)。其过程一般为：将所需要的组分或它们的先驱物用机械球磨方法（干磨、湿磨）进行粉碎并混合。然后在一定的温度下煅烧。由于达不到微观均匀，而且粉末的细度有限（通常很难小于 l μm 而达到亚微米级），因此人们普遍采用化学法得到各种粉末原料。根据起始组分的形态和反应的不同，化学法可分为以下三种类型： 1.固相法： 化合反应法：化合反应一般具有以下的反应结构式： A(s)+B(s)→C(s)+D(g) 两种或两种以上的固态粉末，经混合后在一定的热力学条件和气氛下反应而成为复合物粉末，有时也伴随一些气体逸出。 钛酸钡粉末的合成就是典型的固相化合反应。等摩尔比的钡盐BaCO3和二氧化钛混合物粉末在一定条件下发生如下反应： BaCO3+TiO2→BaTiO3+CO2↑ 该固相化学反应在空气中加热进行。生成用于PTC制作的钛酸钡盐，放出二氧化碳。但是，该固相化合反应的温度控制必须得当，否则得不到理想的、粉末状钛酸钡。 热分解反应法：
论文题目：氧化铝陶瓷的制备与应用 学院：材料科学与工程学院 专业班级：材料化学2班 学号：20090488 姓名：王杰 日期：2011-10-19
氧化铝陶瓷的制备与应用 摘要：氧化铝陶瓷是用途最广泛的陶瓷材料中的一种，它可用作机器及设备制造中的耐腐蚀材料、化工专业中的抗腐蚀材料、电工及电子技术中的绝缘材料、热工技术中的耐高温材料以及航空、国防等领域中的某些特种材料。 Abstract: the alumina ceramics is the most widely use of one of the ceramic material, it can be used as the machine and equipment manufacture of corrosion resistant material, chemical corrosion materials in the professional, electrical and electronic technology of thermal insulation materials, high temperature resistant materials and technologies in the aerospace, defense, etc to some of the special material. 关键词：氧化铝陶瓷耐磨性机械强度耐化学腐蚀 Keywords: alumina ceramics Wear resistance Mechanical strength Chemical corrosion-resistant 氧化铝陶瓷是一种用途广泛的陶瓷。因为其优越的性能，在现代社会的应用已经越来越广泛，满足于日用和特殊性能的需要。[1] 1.硬度大经中科院上海硅酸盐研究所测定，其洛氏硬度为HRA80-90，硬度仅次于金刚石，远远超过耐磨钢和不锈钢的耐磨性能。 2.耐磨性能极好经中南大学粉末冶金研究所测定，其耐磨性相当于锰钢的266倍，高铬铸铁的171.5倍。根据我们十几年来的客户跟踪调查，在同等工况下，可至少延长设备使用寿命十倍以上。
zro2增韧Al2O3陶瓷的制备(ZTA) 摘要: ZrO2/Al2O3复相陶瓷是高温结构陶瓷中最有前途的材料之一,由于其优越的性能和丰富的原料来源,已受到广泛的关注,成为陶瓷材料领域研究的一大热点.本文对氧化锆/氧化铝复相陶瓷的复合机理、最近几年粉体制备常用和最新工艺和ZTA陶瓷应用方面的研究进展进行了综述,并对ZTA复相材料今后的发展进行了展望. 关键词:ZTA;增韧机理;复合粉体制备;研究进展;发展趋势 Abstrac t:Zirconia toughened aluminum (ZTA) hasbeenwidely studied as a new type of toughened ceramic.The aim of this investigation is to review the recent literatures on its synthesismechanisms, new preparation.methods of composite powders and applications. The problems in preparation techniques and developmental trend are discussed aswel.l Key words:ZTA; strengthening and tougheningmechanisms; preparation technology of composite powders;current research situation; development trend Al2O3陶瓷被广泛应用于一些耐高温、强腐蚀环境中,而Al2O3陶瓷断裂韧性较低的致命弱点,限制了它更大范围的使用.采用ZrO2相变增韧、颗粒弥散强化或纤维及晶须补强等方法,可使陶瓷材料的力学性能大大提高,是先进复相结构陶瓷材料的重要发展方向.从ZrO2/Al2O3系统相图[1]可知,即使在很高的温度下ZrO2与Al2O3之间都不会生成固溶体,这就为研究ZrO2/Al2O3复相陶瓷提供了理论依据.由于，ZTA陶瓷是zro2增韧陶瓷中效果最佳者，近年来,不少学者对该系统复相陶瓷进行了大量研究,随着复相陶瓷技术的发展, ZTA 复相陶瓷的研究成为陶瓷材料领域研究的一大热点.本文就近年来国内外文献对ZTA陶瓷的复合机理、制备方法、发展趋势等研究进展做如下综述. 一、ZTA陶瓷的增韧机理 ZTA陶瓷的增韧机理是晶须及纤维增韧,第二相弥散强化增韧, ZrO2相变增韧,以及与金属复合形成金属基复相陶瓷，残余应力增韧等等。以下简单介绍几种研究较热的增韧途径的机理。 1、应力诱导相变增韧 对于ZrO2/Al2O3体系,主要的增韧方式是由ZrO2产生的相变增韧.李世普等人将其解释为[2]：zro2颗粒弥散在Al2O3陶瓷基体中，由于两者具有不同的热膨胀系数，烧结完成后，在冷却过程中，zro2颗粒周围则有不同的受力情况，当它受到基体的抑制，zro2的相转变也将受到抑制。此外，zro2还有另一个特性，是相变温度随着颗粒尺寸的降低而下降，一直可降到室温或室温以下。党基体对zro2有足够的压应力，而zro2的颗粒度有足够小，则其相变温度可降至室温以下，这样在室温时zro2仍可以保持四方相。当材料受到外应力时，基体对zro2的抑制作用得以松弛，zro2颗粒即发生四方相到单斜相的转变，并在基体中引起裂纹，从而吸收了主裂纹扩展的能量，达到增加断裂韧性的效果，这就是zro2的应力诱导相变增韧。 2、微裂纹增韧[3] 毫无疑问，在大多数情况下，陶瓷体内存在有裂纹，包括表面裂纹，工艺缺陷，环境条件下诱发的缺陷，当受外力或存在应力集中时，裂纹会迅速扩展导致陶瓷体破坏。因此，应防止裂纹扩展，消除应力集中，是解决增韧问题的关键。 部分稳定的zro2在发生t-zro2到m-zro2马氏体相变时，相变出现了体积膨胀而导致产
二氧化锆纳米材料 一．用途：纳米氧化锆本身是一种耐高温、耐腐蚀、耐磨损和低热膨胀系数的无机非金属材料,由于其卓越的耐热绝热性能，20世纪20年代初即被应用于耐火材料领域。 自1975年澳大利亚学者K.C.Ganvil首次提出利用ZrO2相变产生的体积效应来达到增韧陶瓷的新概念以来,对氧化锆的研究开始异常活跃。——利用其高硬度、抗磨损、耐刮擦、不燃的特性,极大的提高涂料的耐磨性和耐火效果。由于其导热系数低、并具备特殊光学性能,可用于军事、航天领域的热障涂料及隔热涂料。纳米复合氧化锆具备特殊光学性能,对紫外长波、中波及红外线反射率达85%以上;且其自身导热系数低,可提高其隔热性能。——由于不同晶型纳米氧化锆体积不同,可制备具备自修复功能的功能性涂料。 纳米复合氧化锆行业主要企业产能分布
二．目前的制备方法：化学气相沉积(CVD)法，液相法（包括醉盐水解法，沉淀法，水热法，徽乳液法，溶液姗烧法等），徽波诱导法及超声波法等几大类。 三．具体介绍方法：利用溶胶-凝胶法制备出高度有序的二氧化锆纳米管 简介：溶胶一凝胶法是指金属醉盐或无机盐经水解形成溶胶,然后使溶胶一凝胶化再将凝胶固化脱水,最后得到无机材料.在无机材料的制备中通常应用溶胶—凝胶方法,与传统的合成方法相比,具有高纯度、多重组分均匀以及易对制备材料化学掺杂等优点.该方法要使前驱体化合物水解形成胶体粒子的悬浮液(溶胶)后,成为聚集溶胶粒子组成凝胶,凝胶经过热处理得到所需的物质.溶胶—凝胶沉积法广泛用于在模板的纳米通道中制备纳米管或线.本文主要结合溶胶—凝胶法和模板合成法制备二氧化锆纳米管.由于锆的无机盐价格便宜且对大气环境不敏感[,我们利用锆的无机盐(氯化氧锆)作为前驱体溶液制备稳定的溶胶. 具体过程：
特种陶瓷的制备工艺综述及其发展前景 摘要：本文主要介绍了粉末陶瓷原料的制备技术、特种陶瓷成形工艺、烧结方法以及未来的发展趋势。目前，特种陶瓷中的粉末冶金陶瓷工艺已取得了很大进展，但仍有一些面临急需解决的问题。当前阻碍陶瓷材料进一步发展的关键之一是成形技术尚未完全突破。压力成形不能满足形状复杂性和密度均匀性的要求。多种胶体原位成形工艺，固体无模成形工艺以及气相成形工艺有望促使陶瓷成形工艺获得关键性突破。 关键词：特种陶瓷；成形；烧结；粉末冶金；陶瓷材料 引言 陶瓷分为普通陶瓷和特种陶瓷两大类，特种陶瓷是以人工化合物为原料（如氧化物、氮化物、碳化物、硼化物及氟化物等）制成的陶瓷。它主要用于高温环境、机械、电子、宇航、医学工程等方面，成为近代尖端科学技术的重要组成部分。特种陶瓷作为一种重要的结构材料，具有高强度、高硬度、耐高温、耐腐蚀等优点，无论在传统工业领域，还是在新兴的高技术领域都有着广泛的应用。因此研究特种陶瓷制备技术至关重要。 1 陶瓷原料的制备方法 粉料的制备工艺(是机械研磨方法，还是化学方法)、粉料的性质(粒度大小、形态、尺寸分布、相结构)和成形工艺对烧结时微观结构的形成和发展有着巨大的影响，即陶瓷的最终微观组织结构不仅与烧结工艺有关，而且还受粉料性质的影响。由于陶瓷的材料零件制造工艺一体化的特点，使得显微组织结构的优劣不单单影响材料本身的性能，而且还直接影响着制品的性能。陶瓷材料本身具有硬、脆、难变形等特点。因此，陶瓷材料的制备工艺显得更加重要。 由于陶瓷材料是采用粉末烧结的方法制造的，而烧结过程主要是沿粉料表面或晶界的固相扩散物质的迁移过程。因此界面和表面的大小起着至关重要的作用。就是说，粉末的粒径是描述粉末品质的最重要的参数。因为粉末粒径越小，表面积越大，单位质量粉末的表面积(比表面积)越大，烧结时进行固相扩散物质迁移的界面就越多，即越容易致密化。制备现代陶瓷材料所用粉末都是亚微米(＜lμm)级超细粉末，且现在已发展到纳米级超细粉。粉末颗粒形状、尺寸分布及相结构对陶瓷的性能也有着显著
Durelon Q：对牙髓的刺激如何？ A：Durelon含有的是弱的聚丙烯酸，对牙齿的敏感降到了极低，已被多年的临床使用所证实。 Q：Durelon也具有氟释放能力么？ A：经过3M的独特技术，聚羧酸成分的Durelon同样具有长期的氟释放能力。 Q：Durelon的粘接力如何？ A：Durelon与牙齿之间是通过羧基和钙离子之间的螯和反应，可以与玻璃离子相媲美。 Ketac Cem Easymix Q：Ketac Cem不小心与水混合了，是否需要去除修复体？ A：Ketac Cem的液剂包含了水，酒石酸，以及用安息香酸做的保存剂。其中酒石酸有益于固化特性，并且能提高10%的稳定性。因此，如果修复体已经正确就位，就不需要过多考虑材料固化特性。在没有合并其他情况时，减少10%的稳定性是没有多大影响的。 但是在Ketac Cem的使用守则中，是不允许与水进行混合的。 Q：可以使用Ketac Cem粘接全瓷冠么？ A：这就需要取决于瓷性材料的使用。 目前可用到的材料：玻璃陶瓷 氧化锆或氧化铝陶瓷 由于玻璃陶瓷本身的稳定性低，所以基牙和修复体需要粘性粘接以提高稳定性。而此种粘接是不能由Ketac Cem或其他玻璃离子类水门汀形成的，只能使用树脂类水门汀并且运用全酸蚀技术。此外，在瓷冠内面要应用Rocatec系统改善粘接面，建议使用3M ESPE Sil 使其表面硅烷化。氟酸酸蚀以及硅烷化是适当的选择。以上程序将有益于牙体建构、粘接材料以及间接修复体之间的粘接。 像氧化锆或氧化铝陶瓷这种内在强度高的陶瓷，足以使用传统水门汀，如Kecta Cem。在使用时请参考厂家推荐的适应症，以确定是否可以使用这种水门汀进行粘接。 在这种粘接中，不要先使用氟酸进行酸蚀。而有利于间接修复体的操作是使用Rocatec 硅烷化系统使其表面硅烷化。 RelyX Luting Q：每套包装可以使用多少？ A：对于RelyX Luting来说，推荐使用3匙粉/3滴液来粘接单冠。基于这个比例，可以粘接大约80个单位。 Q：水门汀的有效期是多久？ A：RelyX Luting的有效期是2年。在每次使用完毕后，要注意确保包装瓶药盖好，避免受潮，如果受潮，将会延缓固化。 Q：RelyX Luting可以用来粘接陶瓷修复体么？
二 氧 化 锆 材 料 的 加 工 技 术姓名：罗乔 学号：510011593
摘要 陶瓷材料种类很多，它具有熔点高、硬度高，化学稳定性高、耐高温、耐磨损、耐氧化、耐腐蚀，以及弹性模量大、强度高等优良性质。也正是由于陶瓷材料的这些性质能决定了它的加工也是和普通的材料有着截然不同的加工方式。随着现代工业的发展，对于新型材料的需求也越来越多，陶瓷材料在近十几年来得到飞速的发展。随着它的应用领域越来越广，人们对它的研究也越来越深入。本文将介绍二氧化锆这种比较典型的特种陶瓷材料（人工合成材料）并对其加工技术进行叙述和探讨在国内陶瓷材料的加工技术水平和发展程度。 关键词：陶瓷材料二氧化锆激光加工磨料水射流铣削加工金刚石套料钻
ABSTRACT There is so many kinds of Ceramic material.They have the excellent properties.Such as the High melting point,High hardness,High Chemical stability, Heat-resistant,Resistant to wear,Resistance to oxidation,Corrosion resisting,High Elastic modulus,High strength and so on.Because of these properties , its processing is also with ordinary materials a totally different processing methods.With the development of modern industry,The demand for new materials will be more and more.Ceramic materials get rapid development in recent decade.Along with its application field more and more widely, people have studied it also more and more deeply.This paper will introduce alumina and zro2 which is Synthetic material and its processing technology description and explore the domestic ceramic materials processing techniques and development degree. KEY WORD : Ceramic materials zirconium dioxide Laser processing Abrasive Water technology milling Diamond set of material drill
特种陶瓷概述 10机电一体化3班xxx 指导老师xxx 摘要：本文回顾了陶瓷材料的发展历史，着重评述了特种陶瓷如工程结构陶瓷、生物陶瓷、功能陶瓷等的发展现状，并展望了特种陶瓷的未来发展。 关键词：特种陶瓷、分类、应用、发展及其新动向 1 前言 信息技术、能源和材料是现代文明的三大支柱，材料是人类生产活动和生活必须的物资基础。从现代科学技术发展史可以看到，每一项重大的新技术发现，往往都有赖于新材料的发展。随着能源开发、空间技术、激光技术、传感技术等新技术的出现，现有的一般用途的材料已难以满足要求，开发和有效利用高性能材料和功能材料开始引人瞩目。陶瓷材料具有高强度、耐高温、耐腐蚀、耐磨等特点，因而成为新材料的发展中心。 2 特种陶瓷的定义及分类 特种陶瓷(special ceramics)又叫精细陶瓷(fine ceramics)、先进陶瓷(advanced ceramics)、高技术陶瓷(high-technology ceramics)、或高性能陶瓷(high-performance ceramics)。一般认为，特种陶瓷是“采用高精度的原材料，具有精确控制的化学组成、按照便于控制的制作技术加工的、便于进行结构设计，并具有优异特性的陶瓷”。它的出现与现代工业忽然高技术密切相关。近20年来，由于冶金、汽车、能源、生物、航天、通信等领域的发展对新材料的需要陶瓷材料在国内外已经逐步形成了一个新兴的产业。而特种陶瓷在许多方面都突破了传统陶瓷的概念和范畴，是陶瓷发展史上的一次革命性的变化。 特种陶瓷按照显微结构和基本性能，可分为结构陶瓷、功能陶瓷、智能陶瓷、纳米陶瓷和陶瓷基复合材料。 结构陶瓷：用于高压高温、抗辐射、抗冲击、耐腐蚀、耐磨等环境下的陶瓷材料，可分为氧化物陶瓷、氮化物陶瓷、碳化物陶瓷、硼化物陶瓷等。 功能陶瓷：具有接受特殊敏感功能的陶瓷制品，可分为电功能陶瓷、磁功能陶瓷、光功能陶瓷、生物功能陶瓷。 智能陶瓷：能够接受外部环境的信息而自动改变自身状态的一种新型陶瓷材料，主要有压电陶瓷、形状记忆陶瓷和电流陶瓷。 纳米陶瓷：晶粒或颗粒处于纳米范围(1-100nm)的陶瓷，包括纳米陶瓷粉体、纳米陶瓷纤维、纳米陶瓷薄膜、纳米陶瓷块体。 陶瓷基复合材料：由陶瓷基体和增强体所组成的复合材料，其性能比单一材料的性能优越。初具有陶瓷的高强度、高硬度，良好的耐磨性、耐热性、耐腐蚀性等特点外，还使陶瓷的韧性大大提高，强度和模量也有一定提高。主要有纤维增强、晶须增强、颗粒增强陶瓷基复合材料。 根据陶瓷的性能，吧它们分为高强度陶瓷、高温陶瓷、高韧性陶瓷、铁电陶瓷、压电陶瓷、电解质陶瓷、半导体陶瓷、电介质陶瓷、光学陶瓷（既透明陶瓷）、磁性瓷、耐酸陶瓷和死亡陶瓷。 按照化学组成划分有： 1、氧化物陶瓷：氧化铝、氧化锆、氧化镁、氧化钙、氧化铍、氧化锌、氧化钇、二氧化钛、
日用陶瓷材料的应用与发展 法学092 刘婷09437105 陶瓷材料是人类应用时间最早，并且应用领域最广的材料之一。它是一种天然或人工合成的粉状合成物，经过成型或高温烧结，由金属元素和非金属的无机化合物构成的固体材料。 陶瓷具有耐高温、耐腐蚀、耐磨损、原料丰富、成本低廉等诸多优点。现在，最受关注的三大固体材料是金属材料、高分子材料，以及陶瓷材料。按照其用途的不同，通常可将陶瓷材料分为工业、艺术和日用陶瓷三大类。其中工业陶瓷是指应用于各种工业的陶瓷制品，包括建筑陶瓷、化工陶瓷、电子陶瓷和特种陶瓷几大类；艺术陶瓷主要指花瓶、雕塑等以陈列欣赏和美化环境为主要作用的陶瓷；而日用陶瓷主要是指如餐具、茶具、洁具等日常生活中应用的陶瓷制品。本文主要研究日用陶瓷的应用形式及其发展趋势。 陶瓷材料与其他材料 相对而言，金属材料具有良好的延展性和可塑性，具有良好的热传导性，可是其耐温性和耐腐蚀性较差。高分子材料具有耐腐蚀性和可加工性，色彩丰富，但是其机械强度，耐高温性和耐磨性较差。陶瓷具有高硬度、耐磨、耐酸、耐碱、耐热、耐冷等优越的性能，肌理富于变化，色彩丰富而且不褪色，造型可塑性强，在丰富人们的物质和精神生活，美化环境，以及提升生活品质等方面可达到作用，是其他材料不可替代的。陶瓷致命的缺点在于高脆性和韧性差，这是材料结构所决定的。在室温下，陶瓷材料分子结构几乎不会产生滑移和位错运动，材料处于受力状态时无法通过塑性变形来松弛应力[2]。但是随着生产技术的发展和陶瓷新品种的开发，必然可在其原有基础上逐步改善其容易碎裂的不足，满足相应的产品设计要求。 现在，金属材料和高分子材料越来越多的应用于餐具，容器等日用产品，走
? 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. https://www.doczj.com/doc/3a14605380.html, 5所示,磷酸脲的收率随反应活化剂RX -Ⅲ用量的 增加,先增加而后减少,当其用量为0.15%时,磷酸脲的收率达到67.6%。选择反应活化剂用量为0.15%。 图4 反应物物质的量比与收率的关系 图5 反应活化剂用 量与收率的关系 2.5 验证实验 从以上分析可以得到反应温度为75℃,反应时间0.9h,反应活化剂RX -Ⅲ用量0.15%,尿素与湿法磷酸的物质的量比为1.05∶1为比较合适的工艺条件。在上述条件下进行验证实验,所得磷酸脲收率为79.4%。 测定所得产品中的总氮质量分数(以干基计)为17.9%,磷质量分数(以P 2O 5计)为44.4%,氟质量分数为0.012%,铅质量分数为1.8mg/kg,砷质量分数为1.8mg/kg,重金属质量分数1.8mg /kg 。达到了饲料级磷酸脲的各项理化指标 [10] 。 3 结论与建议 1)在以湿法磷酸和工业尿素为原料悬浮净化法合成磷酸脲的工艺中,反应温度为75℃,反应时间0.9h,反应活化剂RX -Ⅲ用量0.15%,尿素与湿法磷酸的物质的量比为1.05∶1。2)分离母液直接用于加工木材阻燃剂或肥料,降低了由于母液循环利用而增加的能耗。又能防止对环境的污染,解决了环保问题。3)湿法磷酸合成磷酸脲生产成本较低;反应活化剂和悬浮剂的加入和工艺条件的改变,加快了湿法磷酸与尿素的反应速率,提高了湿法磷酸的转化率,减免了传统工艺中对湿法磷酸进行 的净化预处理工序,简化了湿法磷酸生产磷酸脲的 工艺流程,降低了磷酸脲晶体中的杂质含量,提高了磷酸脲产品的品位。4)由湿法磷酸和工业尿素生产饲料级的磷酸脲的悬浮净化法工艺流程的研究是一个非常复杂的问题,尚有许多问题有待于进一步研究解决。如反应活化剂和悬浮剂的配方优化;反应条件和结晶条件的进一步优化,使磷酸脲晶体以更加规整、更好的晶形析出;磷酸脲晶体的过滤和干燥等指标的量化等等。 参考文献: [1] Fowler C W.U rea and urea phos phate fertilizers[M ].Park R idge: N.J.Noyes Data Cor porati on,1976. [2] Harry T L,Ewell F D.Pr oducti on of urea phos phate:US,T103206 [P ].1983-07-05. [3] Cecil P H.Granulati on of urea phos ophate fr om urea and merchant -grade phos phoric acid:US,4512793[P ].1985-04-23. [4] 崔小明.磷酸脲的制备和应用[J ].四川化工与腐蚀控制, 1998,1(1):49-51. [5] 李长彪,李荫泉,彭延明.湿法磷酸制备磷酸脲的连续工艺 [J ].化肥工业,1990,17(3):47-50. [6] 杨晓辉,刘利军,李文强,等.湿法磷酸合成磷酸脲的工艺研究 [J ].宁夏工程技术,2006,5(1):48-50. [7] Dahlia Si m eona Greidinger,Benedict Cytter .Pr ocess for the manu 2 facture of crystalline urea phos phate:US,3936501[P ].1976-02-03. [8] Tang Jianwei,Mu Rongzhe,Zhang Baolin,et al .Solubility of urea phos phate in water +phos phoric acid fr om (277.00t o 354.50)K [J ].Journal of Chem ical &Engineering Data,2007,52(4):1179-1181. [9] 张健,叶世超,陈晓东,等.影响磷酸脲生成质量因素的实验研 究[J ].化学研究与应用,2005,17(1):86. [10] NY/T 917—2004中华人民共和国农业行业标准:饲料级磷酸 脲[S]. 收稿日期:2008-01-15 作者简介:解田(1963— ),男,高级工程师,主要从事精细化工以 及磷复肥生产技术的研究和开发工作,已发表论文5篇,申请专利6项,获贵州省优秀技术创新项目一等奖。 联系方式:xietian@public .gz .cn 一种氧化锆增韧莫来石陶瓷材料及制备方法 本发明涉及一种氧化锆增韧莫来石陶瓷材料及制备方法。采用硅酸锆和α相氧化铝为基体,运用现代增韧和增强技术,加入氧化钇、氧化镁、氧化钙和氧化钛为矿化剂,外加莫来石作晶种,改性增强增韧。采用等静压成型技术,使生 坯体具有均匀性和致密性。在烧结工艺中采用常压高温抽屉窑一次性烧成,温度均匀且成本低。本发明与氧化铝陶瓷材料相比,具有高强度、高韧性、高耐磨性能,生产工艺简单,烧成温度大幅度下降,达到节能降耗的目的。CN,101143783 81 无机盐工业 第40卷第5期
氧化锆陶瓷 摘要：本文介绍了氧化锆的基本性质、氧化锆超细粉体的制备方法、高性能氧化锆陶瓷材料的成型工艺以及其在各领域的应用情况。 关键词：氧化锆；高性能陶瓷；制备；应用 材料所处的环境极为复杂，材料损坏引起事故的危险性不断增加，研究与开发对损坏能自行诊断并具有自修复能力的材料是十分重要而急迫的任务，氧化锆就是具有这种功能的智能材料！ 一、名称：氧化锆陶瓷，ZrO2陶瓷，Zirconia Ceramic 二、种类及特点 纯ZrO2为白色，含杂质时呈黄色或灰色，一般含有HfO2，不易分离。世界上已探明的锆资源约为1900万吨，氧化锆通常是由锆矿石提纯制得。在常压下纯ZrO2共有三种晶态：单斜氧化锆（m-ZrO2）、四方氧化锆（t-ZrO2）和立方氧化锆（c-ZrO2），上述三种晶型存在于不同的温度范围，并可以相互转化： 单斜（Monoclinic）氧化锆（m-ZrO2）<950℃ 5.65g/cc 四方（Tetragonal）氧化锆（t-ZrO2）1200-2370℃ 6.10g/cc 立方（Cubic）氧化锆（c-ZrO2）>2370℃ 6.27g/cc 三、增韧原理 氧化锆增韧的方法,主要是利用氧化锆的相变才能达到的!. 部分稳定ZrO2陶瓷在烧结冷却过程中，ｔ－ZrO2晶粒会自发相变成m－ZrO2，引起体积膨胀，在基体中产生微裂纹，相变诱导的微裂纹会使主裂纹扩展时分叉或改变方向而吸收能量，使主裂纹扩展阻力增大，从而使断裂韧性提高。这种机理称微裂纹增韧。主要增韧方法有：应力诱导相变增韧、微裂纹增韧、残余应力增韧、表面增韧以及复合增韧等。 其中t-ZrO2转化为m-ZrO2相变具有马氏体相变的特征，并且相变伴随有3%～5%的体积膨胀。不加稳定剂的ZrO2陶瓷在烧结温度冷却的过程中，就会由于发生相变而严重开裂。解决的办法是添加离子半径比Zr小的Ca、Mg、Y等金属的氧化物。 材料中的t-ZrO2晶粒在烧成后冷却至室温的过程中仍保持四方相形态，当材料受到外应力的作用时，受应力诱导发生相变，由t相转变为m相。由于ZrO2晶粒相变吸收能量而阻碍裂纹的继续扩展，从而提高了材料的强度和韧性。相转变发生之处的材料组成一般不均匀，因结晶结构的变化，导热和导电率等性能随之而变，这种变化就是材料受到外应力的信号，从而实现了材料的自诊断。 对氧化锆材料压裂而产生裂纹，在300℃热处理50h后，因为t相转变为m 相过程中产生的体积膨胀补偿了裂纹空隙，可以再弥合，实现了材料的自修复。 四、氧化锆粉体的制备 ZrO2超细粉体的制备技术 锆英石的主要成分是ZrSiO4，一般均采用各种火法冶金与湿化学法相结合的工艺，即先采用火法冶金工艺将ZrSiO4破坏，然后用湿化学法将锆浸出，其中间
创新实验设计与训练报告
特种陶瓷的应用与发展 摘要：特种陶瓷是二十世纪发展起来的，在现代化生产和科学技术的推动和培育下，它们"繁殖"得非常快，尤其在近二、三十年，新品种层出不穷，令人眼花缭乱。 关键字：特种陶瓷应用发展前景 特种陶瓷，又称精细陶瓷，按其应用功能分类，大体可分为高强度、耐高温和复合结构陶瓷及电工电子功能陶瓷两大类。在陶瓷坯料中加入特别配方的无机材料，经过1360度左右高温烧结成型，从而获得稳定可靠的防静电性能，成为一种新型特种陶瓷，通常具有一种或多种功能，如：电、磁、光、热、声、化学、生物等功能；以及耦合功能，如压电、热电、电光、声光、磁光等功能。 按照化学组成划分有：氧化物陶瓷、氮化物陶瓷、碳化物陶瓷、硼化物陶瓷、硅化物陶瓷、氟化物陶瓷、硫化物陶瓷，其他还有砷化物陶瓷，硒化物陶瓷，碲化物陶瓷等。 除了主要由一种化合物构成的单相陶瓷外，还有由两种或两种以上的化合物构成的复合陶瓷。例如，由氧化铝和氧化镁结合而成的镁铝尖晶石陶瓷，由氮化硅和氧化铝结合而成的氧氮化硅铝陶瓷，由氧化铬、氧化镧和氧化钙结合而成的铬酸镧钙陶瓷，由氧化锆、氧化钛、氧化铅、氧化镧结合而成的锆钛酸铅镧（PLZT）陶瓷等等。此外，有一大类在陶瓷中添加了金属而生成的金属陶瓷，例如氧化物基金属陶瓷，碳化物基金属陶瓷，硼化物基金属陶瓷等，也是现代陶瓷中的重要品种上。近年来，为了改善陶瓷的脆性，在陶瓷基体中添加了金属纤维和无机纤维，这样构成的纤维补强陶瓷复合材料，是陶瓷家族中最年轻但却是最有发展前途的一个分支。 为了生产、研究和学习上的方便，有时不按化学组成，而根据陶瓷的性能，把它们分为高强度陶瓷，高温陶瓷，高韧性陶瓷，铁电陶瓷，压电陶瓷，电解质陶瓷，半导体陶瓷，电介质陶瓷，光学陶瓷（即透明陶瓷），磁性瓷，耐酸陶瓷和生物陶瓷等等。 随着科学技术的发展，人们可以预期现代陶瓷将会更快地发展，产生更多更新的品种。 特种陶瓷不同的化学组成和组织结构决定了它不同的特殊性质和功能，如高强度、高硬度、高韧性、耐腐蚀、导电、绝缘、磁性、透光、半导体以及压电、光电、电光、声光、磁光等。由于性能特殊，这类陶瓷可作为工程结构材料和功能材料应用于机械、电子、化工、冶炼、能源、医学、激光、核反应、宇航等方面。一些经济发达国家，特别是日本、美国和西欧国家，为了加速新技术革命，为新型产业的发展奠定物质基础，投入大量人力、物力和财力研究开发特种陶瓷，因此特种陶瓷的发展十分迅速，在技术上也有很大突破。特种陶瓷在现代工业技术，特别是在高技术、新技术领域中的地位日趋重要。本世纪初特种陶瓷的国际市场规模预计将达到500亿美元，因此许多科学家预言：特种陶瓷在二十一世纪的科学技术发展中，必定会占据十分重要的地位。 特种陶瓷的应用
氧化锆陶瓷 氧化锆陶瓷第二部分项目第一节特种陶瓷特种陶瓷，又称精细陶瓷，按其应用功能分类，大体可分为高强度、耐高温和复合结构陶瓷及电工电子功能陶瓷两大类。在陶瓷坯料中加入特别配方的无机材料，经过 1360 度左右高温烧结成型，从而获得稳定可靠的防静电性能，成为一种新型特种陶瓷，通常具有一种或多种功能，如:电、磁、光、热、声、化学、生物等功能;以及耦合功能，如压电、热电、电光、声光、磁光等功能。一、分类特种陶瓷是二十世纪发展起来的，在现代化生产和科学技术的推动和培育下，它们quot繁殖quot得非常快，尤其在近二、三十年，新品种层出不穷，令人眼花缭乱。按照化学组成划分有: 氧化物陶瓷氧化物陶瓷:氧化铝、氧化锆、氧化镁、氧化钙、氧化铍、氧化锌、氧化钇、二氧化钛、二氧化钍、三氧化铀等。氮化物陶瓷氮化物陶瓷:氮化硅、氮化铝、氮化硼、氮化铀等。碳化物陶瓷碳化物陶瓷:碳化硅、碳化硼、碳化铀等。硼化物陶瓷硼化物陶瓷:硼化锆、硼化镧等。硅化物陶瓷硅化物陶瓷:二硅化钼等。氟化物陶瓷氟化物陶瓷:氟化镁、氟化钙、三氟化镧等。硫化物陶瓷硫化物陶瓷:硫化锌、硫化铈 还有砷化物陶瓷，硒化物陶瓷，碲化物陶瓷等。除了主要由一种化合物等。其他 构成的单相陶瓷外，还有由两种或两种以上的化合物构成的复合陶瓷。例如，由氧化铝和氧化镁结合而成的镁铝尖晶石陶瓷，由氮化硅和氧化铝结合而成的氧氮化硅铝陶瓷，由氧化铬、氧化镧和氧化钙结合而成的铬酸镧钙陶瓷，由氧化锆、氧化钛、氧化铅、氧化镧结合而成的锆钛酸铅镧(PLZT)陶瓷等等。此外，有一大类在陶瓷中添加了金属而生成的金属陶瓷，例如氧化物基金属陶瓷，碳化物基金属陶瓷，硼化物基金属陶瓷等，也是现代陶瓷中的重要品种上。近年来，为了改善陶瓷
1)应力诱导相变增韧：应力诱导相变增韧是利用应力诱导四方ZrO2马 氏体相变来改变陶瓷材料的韧性，当部分稳定ZrO2增韧陶瓷烧结致密后，四方晶型ZrO2颗粒弥散分布与陶瓷基体中，冷却时亚稳态的四方晶型颗粒受到基体的抑制而处于压应力状态，这时基体中沿颗粒连线方向也处于压应力状态。材料在外力作用下所产生的裂纹尖端附近由于应力集中的作用，存在张应力场，从而减轻了对四方相的束缚，在应力诱发作用下发生四方相(t-ZrO2) 转变成单斜相(m-ZrO2)的马氏体相变，将引起3%～5%的体积膨胀，而相变 颗粒的剪切应力和体积膨胀对基体产生压应变，使裂纹停止延伸，以致需要更大的能量才使主裂纹扩展，即在裂纹尖端应力场的作用下，ZrO2粒子发生马氏体相变而吸收了能量，外力做了功，从而提高了断裂韧性。 2)微裂纹增韧：ZrO2在由四方相向单斜相转变时，因体积膨胀产生的 微裂纹将起到分散基体中主裂纹尖端能量的作用，不论是陶瓷在冷却过程中产生的相变诱发微裂纹，还是裂纹在扩展过程中其尖端区域形成的应力诱发相变导致的微裂纹，都将起到分散主裂纹尖端能量的作用，并导致主裂纹扩展路径发生扭曲和分叉，从而提高断裂能，引起陶瓷断裂韧性的增加； 3)弥散增韧：基体材料中加入ZrO2颗粒，对裂纹起钉扎作用，耗散裂 纹前进的动力。同时，颗粒在基体中受拉伸时阻止横向截面收缩，消耗更多的能量，达到增韧目的。 1)热膨胀失配增韧：热膨胀系数α失配，从而能在第二相颗粒及周 基体内部产生残余应力场，假设第二相颗粒与基体之间不发生化学反应， 果第二相颗粒与基体之间存在热膨胀系数的失配，即?α=αp―αm不等 0(p，m分别表示颗粒和基体)，当?α>0时，第二相颗粒处于拉应力状态 而基体径向处于拉伸状态；当?α<0时，第二相颗粒处于压应力状态，切 受到拉应力，这时裂纹倾向于在颗粒处钉扎或穿过颗粒。微裂纹的出现可 吸收能量从而达到增韧的目的。 2)裂纹编转：裂纹编转是一种裂纹尖端效应，是指裂纹扩展过程中 裂纹尖端遇上偏转剂(颗粒、纤维、晶须、界面等)所发生的倾斜和偏转。 3)裂纹桥联：裂纹桥联是一种裂纹尖端尾部效应，是发生在裂纹尖 后方内某显微结构单元(称为桥联剂，例如纤维、晶须、棒状晶、细长晶粒5 等)连接裂纹的两个表面，并提供一个使两个裂纹面相互靠近的应力，即 合力，这样导致应力强度因子随裂纹扩展而增加，如图1-2所示。当裂纹 展遇上桥联剂时，桥联剂有可能穿晶破坏，如图1-2中第一个颗粒；也有 能出现互锁现象，即裂纹绕过桥联剂沿晶界扩展(裂纹偏转)并形成摩擦桥 如图1-2中第二个颗粒；而第3、4颗粒形成弹性桥，即裂纹桥联。 裂纹扩展路径
特种陶瓷概述 特种陶瓷概述 摘要本文主要叙述了国内特种陶瓷市场发展和生产现状，讲述了相关的制备方法和最新的相关技 术前沿工艺，最后展望了特种陶瓷未来的发 展趋势。 关键词特种陶瓷；市场现状；制备工艺；发展规模 、八、， 刖言 特种陶瓷也称为先进陶瓷、新型陶瓷、高性能陶瓷等，突破了传统陶瓷以黏土为主要原料的界限，主要以氧化物、炭化物、氮化物、硅化物等为主要原料，有时还可以与金属进行复合形成陶瓷金属复合材料，是一种采用现代材料工艺制备的，具有独特和优异性能的陶瓷材料。已成为现代高性能
复合材料的一个研究热点。特种陶瓷于二十世纪发 展起来，在近二、三十年内，新产品不断涌现，在 现代工业技术，特别是在咼技术、新技术领域中的 地位日趋重要。许多科学家预言：特种陶瓷在二^一 世纪的科学技术发展中，必将占据十分重要的地 位。特种陶瓷不同的化学组成和组织结构决定了它 不同的特殊性质和功能，可作为工程结构材料和功 能材料应用于机械、电子、化工、冶炼、能源、医 学、激光、核反应、宇航等领域。一些经济发达国 家，特别是日本、美国和西欧国家，为了加速新技 术革命，为新型产业的发展奠定物质基础，投入大 量人力、物力和财力研究开发特种陶瓷，因此，特 种陶瓷的发展十分迅速，在技术上也有很大突破。 1.发展现状 1.1市场情况: 与20年前相比，目前我国特陶行业结构变化巨大，私营企业、外资企业的数量和比重迅猛增加，特别是外资企业增长势头迅猛，约占我国全部特陶企业的10%左右。当前在电子陶瓷行业中，股份制和三资企业市场竞争力最强。我国特陶市场的开放和市场规模的潜力，吸引许多国外企业纷纷进入，投资不断增加，规模逐步扩大，其投资模式已从最初的产品输入（经销产品）到生产输入（投资设厂），再到应用研究输入（设立实验室），对我国本土特陶企业带来巨大挑战。 1995年我国特种陶瓷产品销售额80亿元人民币（约合10亿美元），其中电子陶瓷约占70%约56亿元；结构陶瓷占30%约为24亿元。相当于日本的1/9、美国的1/5 ,与欧洲的市场规模相当。2015年，特种陶瓷产品产值达到约450 亿元。 45U 460 400
氧化锆陶瓷 一．简介 1.氧化锆的性质： （1）含锆的矿石：斜锆石（ZrO2)，锆英石(ZrO2 ·SiO2)； （2）颜色：白色（高纯ZrO2）；黄色或灰色（含少量杂质的ZrO2），常含二氧化铪杂质；（3）密度：5.65~6.27g/cm3； （4）熔点：2715℃。 （5）氧化锆具有熔点和沸点高、硬度大、常温下为绝缘体、而高温下则具有导电性等优良性质。 2.氧化锆晶型转化和稳定化处理： 在常压下纯ZrO2共有三种晶态：单斜（Monoclinic）氧化锆（m-ZrO2）、四方（Tetragonal）氧化锆（t-ZrO2）和立方（Cubic）氧化锆（c-ZrO2），上述三种晶型存在于不同的温度范围，并可以相互转化，如表1。ZrO2四方相与单斜相之间的转变是马氏体相变，由于四方相转变为单斜相时有3~5%的体积膨胀和7~8%的切应变。因此，纯ZrO2制品往往在生产过程（从高温到室温的冷却过程）中会发生t-ZrO2 转变为m-ZrO2的相变并伴随着体积变化而产生裂纹，甚至碎裂，因此无多大的工程价值。但是，当加入适当的稳定剂（如Y2O3,MgO2,CaO,CeO2等）后，可以降低c-ZrO2 t-ZrO2→m-ZrO2的相变温度，使高温稳定的c-ZrO2 和t-ZrO2相也能在室温下稳定或亚稳定存在。当加入的稳定剂足够多时，高温稳定的c-ZrO2可以一直保持到室温不发生相变。进一步研究发现氧化锆发生马氏体相变时伴随着体积和形状的变化，能吸收能量，减缓裂纹尖端应力集中，阻止裂纹的扩展，提高陶瓷韧性。因此氧化锆相变增韧陶瓷的研究和应用得到迅速发展，氧化锆相变增韧陶瓷有三种类型，分别为部分稳定氧化锆陶瓷；四方氧化锆多晶体陶瓷及氧化锆增韧陶瓷。 晶态温度密度 <950℃ 5.65g/cc 单斜(Monoclinic)氧化锆 (m-ZrO2) 四方(Tetragonal)氧化锆 1200-2370℃ 6.10g/cc (t-ZrO2) 立方(Cubic)氧化锆(c-ZrO2) >2370℃ 6.27g/cc 表1 在常压下纯ZrO2三种晶态 （1）当ZrO2中稳定剂加入量在某一范围时，高温稳定的c-ZrO2通过适当温度下时效处理使c-ZrO2大晶粒（c相）中析出许多细小纺锤状的t-ZrO2（t相）晶粒，形成c相和t 相组成的双相组织结构。其中c相是稳定的而t相是亚稳定的并一直保存到室温。在外力诱导下有可能诱发t相到m相的马氏体相变并伴随体积膨胀，耗散部分能量、抵消了部分外力从而起到增韧作用，称为应力诱导相变增韧。这种陶瓷称之为部分稳定氧化锆，当稳定剂为CaO、MgO、Y2O3时，分别表示为Ca-PSZ、Mg-PSZ、Y-PSZ等。 （2）当ZrO2中稳定剂加入量控制在适当量时可以使t-ZrO2以亚稳状态稳定保存到室温，那么块体氧化锆陶瓷的组织结构是亚稳的t- ZrO2细晶组成的四方氧化锆多晶体称之为四方氧化锆多晶体陶瓷(。在外力作用下可相变t-ZrO2发生相变，增韧不可相变的ZrO2基