Atomic layer deposited Al2O3 passivation of type II InAsGaSb superlattice photodetectors

Atomic layer deposited Al2O3 passivation of type II InAsGaSb superlattice  photodetectors
Atomic layer deposited Al2O3 passivation of type II InAsGaSb superlattice  photodetectors

Atomic layer deposited Al2O3 passivation of type II InAs/GaSb superlattice photodetectors

Omer Salihoglu, Abdullah Muti, Kutlu Kutluer, Tunay Tansel, Rasit Turan, Coskun Kocabas, and Atilla Aydinli

Citation: Journal of Applied Physics 111, 074509 (2012); doi: 10.1063/1.3702567

View online: https://www.360docs.net/doc/cb16147190.html,/10.1063/1.3702567

View Table of Contents: https://www.360docs.net/doc/cb16147190.html,/content/aip/journal/jap/111/7?ver=pdfcov

Published by the AIP Publishing

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Atomic layer deposited Al 2O 3passivation of type II InAs/GaSb superlattice photodetectors

Omer Salihoglu,1,a)Abdullah Muti,1Kutlu Kutluer,2Tunay Tansel,2Rasit Turan,2Coskun Kocabas,1and Atilla Aydinli 1

1Department of Physics,Bilkent University,06800Ankara,Turkey

2

Department of Physics,Middle East Technical University,06531Ankara,Turkey

(Received 12December 2011;accepted 8March 2012;published online 9April 2012)

Taking advantage of the favorable Gibbs free energies,atomic layer deposited (ALD)aluminum oxide (Al 2O 3)was used as a novel approach for passivation of type II InAs/GaSb superlattice (SL)midwave infrared (MWIR)single pixel photodetectors in a self cleaning process (k cut-off $5.1l m).Al 2O 3passivated and unpassivated diodes were compared for their electrical and optical performances.For passivated diodes,the dark current density was improved by an order of magnitude at 77K.The zero bias responsivity and detectivity was 1.33A/W and 1.9?1013Jones,respectively at 4l m and 77K.Quantum ef?ciency (QE)was determined as %41for these detectors.

This conformal passivation technique is promising for focal plane array (FPA)applications.V

C 2012American Institute of Physics .[https://www.360docs.net/doc/cb16147190.html,/10.1063/1.3702567]

I.INTRODUCTION

A critical step in the fabrication of optoelectronic devi-ces is the passivation of the exposed surfaces.Such surfaces are often created in order to con?ne current or light.In pho-todetectors,the requirement for the con?nement of current is met by fabrication of a mesa structure,which results in a large number of surface states generated due to the abrupt termination of the crystal structure on the mesa side walls.Ensuing surface leakage currents are typically due to dan-gling bonds,inversion layers,and interfacial traps leading to lower responsivity.In photodetectors based on III-V materi-als,etched surfaces exposed to atmosphere form thin layers of native oxides some of which are good conductors,increas-ing the shunt current.Photodetectors with small pixel sizes (<25l m)suffer from surface leakage more than large pixel photodetectors due to their higher perimeter to area ratio.Thus,for focal plane array (FPA)applications and long wavelengths,passivation becomes an especially vital issue.In order to overcome surface leakage currents,various passi-vation methods such as ammonium sul?de passivation,1,2deposition of silicondioxide layer,3polyimide layer,4and overgrowth with wide bandgap material 5have been used.Passivation is expected to suppress oxidation of the side walls and saturate dangling bonds to prevent surface states.Sulfur passivation replaces oxygen with sulfur at the mesa side walls and saturate the dangling bonds.2,6It is an effec-tive passivation method and is relatively easy to apply but the effect of passivation is temporary and some reports claim that sulfur passivation damages the surface of the photode-tector.6Silicondioxide deposition on sidewalls have also been shown to be an effective technique,but it requires high temperatures for deposition or high RF powers to excite a plasma with potential for damage.With growth temperatures

of about 400 C,high temperatures tend to damage III-V structures and high density energetic plasmas can cause physical damage on III-V surfaces and side walls resulting in unwanted surface states in the bandgap of the III-V materi-als.We note also that oxidation of the etched surfaces is typi-cally very rapid and a thin layer of oxides forms almost immediately prior to passivation.Thus a self cleaning proce-dure eliminating the already formed thin oxide layer would be most welcome.Recent work on the surface and interface chemistry of III-V surfaces passivated with atomic layer deposited Al 2O 3has shown that it is possible to reduce the native oxides during deposition since formation of Al 2O 3is energetically preferred due to lower Gibbs free energy of Al 2O 3(à377.9kcal/mol).7This is lower than the Gibbs free energies of Ga 2O,Ga 2O 3,In 2O 3,As 2O 3,As 2O 5,and Sb 2O 3,which are à75.3kcal/mol,à238.6kcal/mol,à198.6kcal/mol,à137.7kcal/mol,à187.0kcal/mol,and à151.5kcal/mol,res-pectively.8,9Hinkle et https://www.360docs.net/doc/cb16147190.html,ing X-ray photoelectron spectros-copy (XPS)has shown that deposition of Al 2O 3on degreased and etched GaAs strongly reduces Ga and As oxides.10Simi-lar work on InAs has shown strong reduction of In and As oxides.11Work on electrical characterization of MOS capaci-tors fabricated on GaSb has demonstrated strong suppression of Sb 2O 3due to Al 2O 3deposition.12

Surface passivation is even more critical in type-II super lattice (T2SL)InAs/GaSb photodetectors,due to a large number of very thin alternating layers.T2SL detectors have recently received great interest in the development of mid-wave and long wave infrared detectors due to advantages like bandgap engineering,13suppression of Auger recombi-nation,14and interband tunneling 15and has been shown to be a very promising alternative to MCT and QWIP in focal plane array (FPA)applications where,low dark current below 77K is required.

In this work,we propose to use atomic layer deposited Al 2O 3as a passivation layer for InAs/GaSb SL photodetec-tors.ALD is a self limiting process that consists of sequential

a)

Author to whom correspondence should be addressed.Electronic mail:omersalihoglu@https://www.360docs.net/doc/cb16147190.html,,t903122901971.

0021-8979/2012/111(7)/074509/4/$30.00V

C 2012American Institute of Physics 111,074509-1

JOURNAL OF APPLIED PHYSICS 111,074509(2012)

gas phase reactions on the surface of the SL photodetector. The growth of Al2O3with ALD uses two gases that are intro-duced to the chamber one at a time and which react with the gas on the surface adsorbed during the previous sequence. ALD deposited Al2O3has many advantages as a passivation layer such as the control of thickness at the molecular level since in the ALD process,thickness depends on the number of reaction cycles.This leads to a precise thickness control as well as perfect conformal coverage even at sharp edges, large area thickness uniformity,very low process tempera-tures,and plasma free operation.Furthermore Al2O3is a very good dielectric over a very large frequency range.In the case of T2SL photodetectors where mesa etching leads to uneven etching of very thin InAs and GaSb layers at the side walls,conformal coverage at the atomic level may be very bene?cial.These properties of ALD grown Al2O3make it a perfect candidate for passivation of InAs/GaSb super lattice FPA photodetectors.No use of Al2O3as a passivation layer has been made so far for InAs/GaSb super lattice system. II.EXPERIMENTAL

The sample studied in this work was grown commer-cially(IQE https://www.360docs.net/doc/cb16147190.html,A)with molecular beam epitaxy on a GaSb substrate.The photodetector is designed as p-i-n photo-detector with design cutoff wavelength of5l m.It starts with 100nm thick GaSb buffer layer and20nm Al(x)GaAs(y)Sb as an insulator and etch stop layer,followed by1000nm GaSb:Be(p?1.0?1017cmà3)p contact layer.P-i-n part of the design consist of90periods8monolayers(MLs)of InAs/8MLs of GaSb:Be(p?1.5?1017cmà3)p-type layers, 60periods8MLs of InAs/8MLs of GaSb i-layers,60periods 8MLs of InAs:Te(n:5?1017cmà3)/8MLs of GaSb n-type layers and structure is terminated by20nm InAs:Te(n:5?1017cmà3)cap layer to assure good ohmic contact.Appropri-ate shutter sequences were applied to compensate the tensile strain caused by lattice mismatch between InAs and GaSb layers.Single pixel photodetectors were fabricated with 400?400l m mesa size.To minimize surface damage,mesas have been fabricated by standard lithography and wet etch solution.Mesa-isolated photodiodes are de?ned at room temperature,using the chemical solution based on H3PO4/ C6H8O7/H2O2/H2O with200nm per minute etch rate.The etch process has been stopped when etch depth reached the bottom contact layer.The etch depth was about1.5l m.200 cycles Al2O3passivation layer deposition carried out in atomic layer deposition system(Cambridge Nanotech Savan-nah100)with150 C as the substrate holder temperature. Growth of Al2O3has been done by delivering0.015s water vapor(H2O)and0.015s trimethylaluminum(TMA)pulses into the chamber in a sequential manner under constant20 sccm N2gas?ow.A wait time of20s was added after each pulse to ensure surface reactions to take place.Both trimethy-laluminum and water were unheated.The thickness of the ?lm grown in this manner was determined as20nm by subse-quent etching and measurement of the Al2O3?lm.Ohmic contacts were made by evaporating5nm Titanium(Ti)and 200nm Gold(Au)on the bottom and top contact layers of the detectors.Fabricated detectors were bonded to a chip carrier for further characterization.Exact same procedures were applied to another sample without Al2O3passivation to act as a reference detector.

III.RESULTS AND DISCUSSION

To investigate the effect of Al2O3passivation,samples were mounted on a liquid nitrogen cooled cold?nger.Dark current measurements were performed at77K by using a HP4142OA source-measure unit.Figure1shows the meas-ured dark current density versus applied bias voltage charac-teristics of the unpassivated and Al2O3passivated400?400l m single pixel test diodes at77K.Single pixel passi-vated detector shows at least an order of magnitude reduction on dark current density compared with an unpassivated de-tector.Atà0.1V bias voltage,dark current density reduced from4.7?10à5A/cm2to6.6?10à7A/cm2.These meas-urements yielded R0A product values of1.6?103Xácm2 and3.7?105Xácm2for the unpassivated and Al2O3passi-vated samples,respectively.Atà0.1V bias and77K,Al2O3 passivation shows improved dark current results when com-pared with SiO2and SU8passivation.6,16The prominent reduction in dark current due to ALD deposited Al2O3passi-vation is very encouraging for use in FPA applications.6,17 Spectral response of the photodetectors was measured using a Fourier transform infrared spectroscopy(Bruker Equinox55)and a liquid nitrogen cooled cold?nger system. Figure2shows spectral response of the unpassivated and Al2O3passivated photodetectors measured under single pass and front side illumination condition.The cut-off wavelength of the Al2O3passivated and unpassivated photodetectors is determined to be5.1l

m.

FIG.1.(a)Dark current density vs applied bias of unpassivated and Al2O3 passivated400l m single pixel square diodes measured at77K.(b)Zero bias differential resistance vs applied bias voltage characteristics for the unpassivated and Al2O3passivated samples at77K.Dashed line represents Al2O3passivated device and solid line represents unpassivated device.

The responsivity of the photodetectors has been meas-ured at 77K using calibrated blackbody source at 800 C (Newport,Oriel 67000),lock-in ampli?er (SRS,SR830DSP)and mechanical chopper (SRS,SR540)system.Photo-detectors were illuminated with a 300K background with a 2p ?eld-of-view.A 3-5l m blackbody ?lter has been use to eliminate unwanted illumination.Figure 3shows responsiv-ity and calculated Johnson-noise limited detectivity (D*)versus applied bias voltage graph for Al 2O 3passivated pho-todetector.The zero bias responsivity of Al 2O 3passivated photodetector was equal to 1.33A/W at 4l m and 77K.Under zero bias,the peak D*,was equal to 1.9?1013Jones for the Al 2O 3passivated single pixel photodetector at 4l m and 77K.Quantum ef?ciency (QE)of the passivated photo-detector has been determined as %41for single pass front illumination condition.When we compare our results with recent publications,6,16–19ALD grown Al 2O 3passivated

T2SL photodetectors are very promising.In FPA applica-tions,larger perimeter to area ratio increases the effect of surface leakage in the operation of the smaller FPA detectors and passivation becomes an important issue.ALD grown Al 2O 3passivation technique may be a good candidate also for LWIR photodetectors.This will be especially true for photodetectors designed to operate in the LWIR region due to relatively small bandgap of the LWIR photodetectors,where surface leakage currents are more dominant.Work is in progress to demonstrate this.

To understand the nature of the dark current,tempera-ture dependent measurements of the dark current has been done.Relationship between the dark current densities and inverse temperatures at à0.1V bias are shown in Fig.4.The I-V curve is dominated by diffusion current at high tempera-tures and generation-recombination current at low tempera-tures.The diodes with Al 2O 3passivation show lower dark current than unpassivated photodetectors at low tempera-tures.This indicates that the Al 2O 3passivation satis?es sur-face states and prevents current ?ow through the surface channel.Al 2O 3passivated photodetectors show Arrhenius type behavior above 100K,characterizing the dominant bulk diffusion current.The activation energy has been calculated as 0.233eV,which is close to the device bandgap.For lower temperatures the current begins to divert from the Arrhenius type of behavior.Generation recombination (G-R)current becomes dominant for mid temperatures.At 40K dark cur-rent density shows a tendency to decrease indicating that sur-face leakage starts to become important in this temperature range.20For the unpassivated detector,dark current density deviates from the Arrhenius type of behavior at temperatures lower than 120K indicating surface related currents are dom-inant at this range.

The in?uence of Al 2O 3on the performance of the T2SL is closely related to the interface chemistry of the Al 2O 3/https://www.360docs.net/doc/cb16147190.html,ponents of InAs/GaSb SL are chemically very reactive.Their surfaces are easily oxidized and a native oxide layer of several nanometers thick is quickly formed upon exposure to air.21Oxygen diffuses through the surface,reacts with

both

FIG.2.Spectral response of the unpassivated and Al 2O 3passivated photo-detectors at 77K.The cut-off wavelength of the Al 2O 3passivated and unpassivated photodetectors is $5.1l m.Dashed line represents Al 2O 3passi-vated device and solid line represents unpassivated

device.

FIG.3.Responsivity and detectivity of Al 2O 3passivated,400?400l m single pixel test detectors at 77K and 4l m.The zero bias responsivity and the peak value of detectivity,D*of Al 2O 3passivated photodetector was equal to 1.33A/W and 1.9?1013Jones,

respectively.

FIG.4.Temperature dependent dark current measurements of Al 2O 3passi-vated and unpassivated photodetectors at à0.1V bias.

Ga and Sb,and forms oxide layers,through the chemical reaction2GaSbt3O2!Ga2O3tSb2O3.12Using the same argument leads to oxidation of In and As such that2InAst3O2!In2O3tAs2O3.22Further,In2O3and As2O3may react and form InAsO3(Ref.23)since In2O3tAs2O3! 2InAsO3.This mechanism is responsible for the formation of additional conductive channels and,consequently,leads to a large surface component of dark current.Reduction of the oxides during the ALD deposition is due to favorable Gibbs free energies for forming Al2O3compared to As,Ga,Sb,and In oxides.Al2O3formation is energetically preferred to native oxide of InAs and GaSb.

Alternatively,Alt3atoms in the trimethylaluminum (TMA)molecule could possibly replace As atoms that form As2O3or In atoms in an In2O3molecule.24Similar reaction pathways with oxides of other metal atoms are also possible. These are so called interfacial self cleaning reactions of surface oxides.7Reduction of oxides after Al2O3deposition for GaSb and InAs has been con?rmed by XPS measurements.11,12,25 Finally,in the case of T2SLs with large numbers of very thin dissimilar layers,different etch rates of InAs and GaSb lead to roughness on the mesa side walls.Conformal coating of atomic layer deposition creates a perfect protective layer against environmental effects especially against oxidation. This conformal coverage of rough surfaces also satis?es dan-gling bonds more ef?ciently while eliminating metal oxides in a self cleaning process.This makes ALD Al2O3a perfect candidate for passivation of InAs/GaSb superlattice photode-tectors.That this state-of-art passivation technique results in high responsivity and detectivity and very low dark current is a clear indication of improvements due to self healing ALD Al2O3passivation process.

IV.CONCLUSION

In conclusion,we have demonstrated the suppression of dark current and increase in optical response of the InAs/ GaSb superlattice photodetectors with cutoff wavelength at 5.1l m(MWIR).We have used ALD deposited Al2O3passi-vation layer on InAs/GaSb p-i-n design superlattice photode-tectors.Plasma free and low operation temperature with uniform coating gave us conformal and defect free coverage on the side walls.Al2O3passivated superlattice photodetec-tors reduced the dark current from4.7?10à5A/cm2to6.6?10à7A/cm2compared to unpassivated photodetector at 77K and underà0.1V applied bias condition.Corresponding zero bias area product(R0A)improved at least an order of magnitude(from1.6?103Xácm2to3.7?105Xácm2).The zero bias responsivity and detectivity(D*)are determined as 1.33A/W and1.9?1013Jones,respectively for the Al2O3 passivated photodetector at4l m and77K.Quantum ef?-ciency(QE)of the passivated photodetector has been deter-mined as%41for single pass front illumination condition.Temperature dependent dark current measurements revealed that passivated devices show Arrhenius type of behavior at higher temperatures which is indication that dominant current is bulk diffusion current.The calculated activation energy is equal to0.233eV,which is close to the device bandgap.This work shows that ALD coated Al2O3is a good material as a passivation layer for p-i-n design InAs/GaSb superlattice photodetectors.

1E.Plis,J.B.Rodriguea,S.J.Lee,and S.Krishna,Electron Lett.42,1248 (2006).

2V.N.Bessolov and M.V.Lebedev,Semiconductors32,1141(1998).

3A.Gin,Y.Wei,J.Bae,A.Hood,J.Nah,and M.Razeghi,Thin Solid Films 447,489(2004).

4A.Hood,P.Y.Delaunay,D.Hoffman,M.Razeghi,and V.Nathan,Appl. Phys.Lett.90,233513(2007).

5R.Rehm,M.Walter,F.Fuchs,J.Schmitz,and J.Fleissner,Appl.Phys. Lett.86,173501(2005).

6H.S.Kim,E.Plis,A.Khoshakhlagh,S.Mayers,N.Gautam,Y.D. Sharma,L.R.Dawson,S.Krishna,S.J.Lee,and S.K.Noh,Appl.Phys. Lett.96,033502(2010).

7D.Pulver,C.W.Wilmsen,D.Niles,and R.Kee,J.Vac.Sci.Technol.B 19,207(2001).

8G.Hollinger,R.S.Kabbani,and M.Gendry,Phys.Rev.B49,11159 (1994).

9A.J.Bard,R.Parsons,and J.Jordan,Standard Potentials in Aqueous Solu-tions(Marcel Dekker,New York,1985).

10C.L.Hinkle,A.M.Sonnet,E.M.Vogel,S.McDonnel,G.J.Hughes, https://www.360docs.net/doc/cb16147190.html,ojevic,B.Lee,F.S.Aguirre-Tostado,K.J.Choi,H.C.Kim, J.Kim,and R.M.Wallace,Appl.Phys.Lett.92,071901(2008).

11R.Timm,A.Fian,M.Hjort,C.Thelander,E.Lind,J.N.Andersen,L.E. Wernersson,and A.Mikkelsen,Appl.Phys.Lett.97,132904(2010).

12A.Ali,H.S.Medan,A.P.Kirk,D.A.Zhao,D.A.Mourey,M.K.Hudait, R.M.Wallace,T.N.Jackson,B.R.Bennett,J.B.Boos,and S.Datta, Appl.Phys.Lett.97,143502(2010).

13Y.Wei and M.Razeghi,Phys.Rev.B69,085316(2004).

14C.H.Grein,P.M.Young,and H.Ehrenreich,Appl.Phys.Lett.61,2905 (1992).

15D.L.Smith and C.Mailhiot,J.Appl.Phys.62,2545(1987).

16M.Herrera,M.Chi,M.Bonds,N.D.Browning,J.N.Woolman,R.E. Kvaas,S.F.Harris,D.R.Rhiger,and C.J.Hill,Appl.Phys.Lett.93, 093106(2008).

17H.S.Kim,E.Plis,J.B.Rodriguez,G.D.Bishop,Y.D.Sharma,L.R. Dawson,S.Krishna,J.Bundas,R.Cook,D.Burrows,R.Dennis,K.Pat-naude,A.Reisinger,and M.Sundaram,Appl.Phys.Lett.92,183502 (2008).

18E.Kwei-wei,D.Hoffman,B.M.Nguyen,P.Y.Delaunay,and M.Raze-ghi,Appl.Phys.Lett.94,053506(2009).

19R.Helm,M.Walter,J.Schmitz,F.Rutz,J.Fleibner,R.Scheibner,and J.Ziegler,Infrared Phys.Technol.52,344(2009).

20B.M.Nguyen,D.Hoffman,E.K.Huang,S.Bogdanov,P.Y.Delaunay, M.Razeghi,and Z.Tidrow,Appl.Phys.Lett.94,223506(2009).

21C.Cervera,J.B.Rodriguez,R.Chaghi,H.A?¨t-Kaci,and P.Christol, J.Appl.Phys.106,024501(2009).

22C.S.Seibert,M.D’Souza,J.C.Shin,L.J.Mawst,D.Botez,and D.C. Hall,J.Appl.Phys.109,033103(2011).

23G.Hollinger,R.Skheyta-Kabbani,and M.Gendry,Phys.Rev.B49, 11159(2004).

24C.H.Chang,Y.K.Chiou,Y.C.Chang,K.Y.Lee,T.D.Lin,T.B.Wu, M.Hong,and J.Kwo,Appl.Phys.Lett.89,242911(2006).

25H.D.Trinh,G.Brammertz,E.Y.Chang,C.I.Kuo,C.Y.Lu,Y.C.Lin, H.Q.Nguyen,Y.Y.Wong,B.T.Tran,K.Kakushima,and H.Iwai,IEEE Elec.Dev.Lett.32,752(2011).

提高氧化铝透明陶瓷透明度

提高氧化铝透明陶瓷的透明度 氧化铝透明陶瓷:又称半透明氧化铝陶瓷或透明多晶氧化铝陶瓷主晶相为α-A12O3。密度3.98g/cm3以上。直线透光率90%~95%以上。介电常数大于9.8。介电损耗角正切值小于2.5×10-4(1GC>,抗弯强度大于350~380MPa。击穿强度6.0~6.4kV/mm。热膨胀系数(6.5~8.5>×10-6/℃。高温下具有良好耐碱金属蒸气腐蚀性。 原料为纯度99.99%以上的Al2O3,添加少量纯氧化镁、三氧化二镧、或三氧化二钇等添加剂,采用连续等静压成型,气氛烧结或热压烧结,严格控制晶粒大小,可获得高致密透明陶瓷。 用于制造高压钠灯的发光管(工作寿命可超过2万h>。也可用作微波集成电路基片、轴承材料、耐磨表面材料和红外光学元件材料等。 1. 概述 透明陶瓷特性:耐高温耐腐蚀 高绝缘高强度 透明 一般陶瓷—气孔、杂质、晶界、结构 ↓ 对光反射损失+吸收损失 ↓ 光学不透明 2.透光模型 表面反射光 ↑ 入射光→陶瓷材料→透射光 ↓ 内部吸收光 + 散射光 ↑↑ 晶体本身+杂质外表+内散射中心 ↓ 杂质+微气孔+晶粒直径↓ 散射量最大←入射光波长=晶粒直径 3.陶瓷透光的基本条件 1>致密度>理论密度的99.5% 2>晶界无空隙或空隙大小<<入射光波长

3>晶界无杂质及玻璃相,或其与微晶体的光学性质相似 4>晶粒较小且均匀,其中无空隙 5>晶体对入射光的选择吸收很小 6>晶体无光学异向性(立方晶系> 7>表面光洁 4.工艺原理 <1)控制以体积扩散为烧结机制的晶粒长大过程 晶粒过快生长—晶界裂缝,封闭气孔 晶粒生长速度 > 气孔移动速度 —包裹于晶体内的气孔更不易排出 加入适量MgO(0.1-0.5%> →透明Al 2O 3 陶瓷 ↓ 1>MgAl 2O 4 晶界析出,阻止晶界过快迁移 2>MgO较易挥发,防止形成封闭气孔↓ 限制晶粒过快生长—微晶结构透明Al 2O 3 陶瓷 <2)控制气孔平均尺寸 烧结透明Al 2O 3 陶瓷:晶粒~25μm,大小均匀 气孔半径0.5-1.0μm 气孔率0.1% 热压烧结Al 2O 3 陶瓷:晶粒1-2μm,大小不均 气孔半径~0.1μm 对可见光散射效应强 在可见光区透光率:烧结瓷 >热压瓷 <3)其他因素:原料纯度、细度,成型方法,烧结气氛等氢气或真空中烧结,透光率高 5.工艺方法 1)配料 主料:高纯Al 2O 3 (>99.9%> —硫酸铝铵热解法 Al 2(NH 4 > 2 (SO 4 > 4 ?24H 2 O ~200℃ → Al 2 (SO 4 > 3 ?(NH 4 > 2 SO 4 ?H 2 O + 23 H 2 O↑ 500~600 ℃ → Al 2 (SO 4 > 3 + 2NH 3 ↑+SO 3 ↑ + 2 H 2 O↑ 800~900 ℃ →γ-Al 2O 3 + 3 SO 3 ↑ ~1300 ℃/1.0~1.5h →α-Al 2O 3 (少量γ-Al 2O 3 提高活性,促进烧结> 改性料:MgO 以Mg(NO 3> 2 加入,共同热分解 —分布均匀,活性较大的MgO 2)成型和烧结: a>常温注浆或等静压成型,高温烧结 浆料pH=3.5,流动性较好 坯体理论密度 > 理论密度的85% 氢气或真空下烧结,T=1700-1900℃

CBN磨具陶瓷结合剂

目录 摘要〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃 1 1.前言〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃 1 2.CBN磨具陶瓷结合剂性能〃〃〃〃〃〃〃〃〃〃〃〃〃〃 2 2.1耐火度〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃2 2.2本征强度〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃2 2.3热膨胀系数〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃3 2.4润湿性〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃4 3. 目前的制约因素〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃 5 4.CBN砂轮结合剂的分类〃〃〃〃〃〃〃〃〃〃〃〃〃〃 5 4.1树脂结合剂CBN砂轮〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃6 4.2金属结合剂CBN砂轮〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃6 4.3陶瓷结合剂砂轮〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃7 5、CBN磨具陶瓷结合剂在超硬工具上的应用〃〃〃〃〃〃〃8 6、CBN陶瓷结合剂对高速砂轮强度的影响〃〃〃〃〃〃〃〃9 7、金属Al粉对CBN磨具陶瓷结合剂性能的影响〃〃〃〃9 7.1、不同烧成温度下Al粉对磨具强度的影响〃〃〃〃〃〃9 8、应用推广的前景〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃10 9.结束语〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃11 10.参考文献:〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃〃12

CBN磨具陶瓷结合剂 摘要本文简单概述了CBN的结构与性能特点,对近年来有关CBN砂轮陶瓷结合剂的研究进展作了较详细的综述,指出了低熔点、高强度陶瓷结合剂是CBN砂轮陶瓷结合剂的发展趋势,阐述了CBN砂轮陶瓷结合剂实质上就是碱硼硅玻璃结合剂,其中硼酸盐系结合剂因具有低熔点、高强度的特性,使之成为了研究的重点。还介绍了玻璃的特性,和陶瓷结合剂的简介以及玻璃结合剂的特点及加工工艺。 关键词立方氮化硼(CBN);陶瓷结合剂;纳米氧化物; 1.前言 随着我国政治稳定,经济建设快速发展,作为世界制造业中心的地位日益凸现。如何逐步缩小与世界工业发达国家的差距,使经济增长由资源消耗型加速转变为高效节能型上来,走一条具有中国特色的,可持续发展的道路。就磨削领域来说,陶瓷结合剂CBN磨具所具有的高质量、高精度、高效率、低消耗、低成本、低污染、自动化程度高等优异性能,是其他磨削工具无法比拟的。保护环境是我们的基本国策,陶瓷结合剂CBN磨具,从它的原材料生产过程,磨具的制造过程,磨具的使用过程,对资源和能源的消耗都是极低的,属于节能型的高科技产品,非常适合我国现阶段及长远发展。在工业发达国家,陶瓷结合剂磨具的应用发展非常迅速,每年都以40%以上的速度增长。但是据不完全统计,我国的增长速度仅为20%左右,因此,我国的陶瓷CBN磨具拥有广阔的发展空间。

低熔高强陶瓷结合剂的研究

2005年第2期 超 硬 材 料 工 程第17卷2005年4月SU PERHA RD M A T ER I AL EN G I N EER I N G总第60期 低熔高强陶瓷结合剂的研究① 郭志敏1,张向红1,2,臧建英2,王艳辉2 (1.河北建材职业技术学院,河北秦皇岛066004;2.燕山大学,河北秦皇岛066004) 摘 要:为实现陶瓷结合剂超硬磨具的低温烧结,减少或避免高温或由高温引起的对磨粒的伤害,本试验 以黏土、硼玻璃和铅玻璃为主要原料,研制一种低熔点高强度结合剂。通过一系列试验,测定了结合剂的耐 火度,研究了结合剂在高温下的相态,分析了结合剂在高温时与超硬磨粒的浸润性,并测试了结合剂的抗 折强度。试验表明,该结合剂耐火度低、强度高,与超硬磨粒具有良好的浸润性,在高温下呈玻璃态,是一种 低熔点高强度陶瓷结合剂。 关键词:超硬磨具;陶瓷结合剂;低温烧结试验;低熔高强;玻璃态; 中图分类号:TQ164 文献标识码:A 文章编号:1673-1433(2005)02-0007-07 STUDY ON LOW M EL T ING PO INT AND H IGH STRENGTH V ITR IF IED B OND GU O Zh i2m in1,ZHAN G X iang2hong1,2,Z AN G J ian2ying2,W AN G Yan2hu i2 (1.H ebei B u ild ing M a teria ls Institu te of V oca tion and T echnology,Q inhuang d ao H ebei,066004; 2.Y anshan U n iversity,Q inhuang d ao,H ebei,066004) Abstract:L ow m elting po in t and h igh strength vitrified bond is p rep ared to realize sin tering of vitrified bond sup erhard grinding too ls at low er tem p eratu re.R aw m aterials w ere m ain ly clay,bo ric glass and lead glass.T he refracto ry tem p eratu re,the p hase at h igh tem p eratu re,the bending strength of the bond and soakage betw een the bond and sup erhard grain s w ere tested.T he resu lts ju st show that the bond ex ist as glassy p hase and is a low m elting po in t and h igh strength vitrified bond. Keywords:vitrified bond;low m elting po in t and h igh strength;sin tering test at low er tem p eratu re;glassy p hase;sup erhard grinding too ls 0 前言 一般情况下,陶瓷结合剂含有起助熔作用的碱金属氧化物,而且由于其耐火度很高,其烧成温度通常高达1200℃以上,如此高的烧成温度,无论是对金刚石还是对cBN颗粒都有很大的伤害,进而影响超硬磨具的工作效率和使用寿命。为减少或避免温度对超硬磨粒的不利影响,实现磨具的低温烧成,有必要研究配制一种低熔点陶瓷结合剂。 对超硬磨具来说,其加工效率和使用寿命在很大程度上取决于结合剂的性质以及超硬磨粒与结合剂的结合强度,这就要求:(1)结合剂的膨胀系数应尽量与超硬磨料的膨胀系数相等或相近;(2)结合剂与磨粒之间有较强的浸润性和结合力;(3)超硬磨料的超硬性也要求结合剂具有较高的强度。 因此,研制一种低熔点高强度陶瓷结合剂是提高陶瓷结合剂超硬磨具质量的一个关键因素。 1 试验过程 本试验以黏土、硼玻璃、铅玻璃为主要原料,根据配 ①收稿日期:2004-10-20 作者简介:郭志敏(1965- ),女,河北工业大学硕士研究生,主要从事超硬材料和高温材料的研究。 通信作者:王艳辉,项目负责人。

镍基复合材料 57-1

镍基复合材料是以镍及镍合金为基体制造的。由于镍的高温性能优良,因此这种复合材料主要是用于制造高温下工作的零部件。 镍基复合材料主要用于液体火箭发动机中的全流循环发动机。这种发动机的涡轮部件要求材料在一定温度下具有高强度、抗蠕变、抗疲劳、耐腐蚀、与氧相容。在目前正在研制的系统中这些部件选用镍基高温合金。虽然用SiC 颗粒或纤维增强的复合材料可以达到高强度、高刚度和抗蠕变。但在全流循环发动机的富氧驱动气体环境下,这些材料不能兼顾与氧的相容性。发动机起动瞬变过程的热冲击环境,排除了涡轮叶片采用加涂层的材料系的可能。 因此,用整体材料制作的涡轮叶片,必须经受住富氧燃烧产物所形成的环境。因为涡轮部件和涡轮盘在大约9min 运行中一般不用冷却,所以在短时运行中,整体材料温度达到730℃是正常的。对某些设计,希望密度低于6.5g/cm3 的材料的强度要大于1040MPa。应力、温度和化学环境都十分苛刻,要延长维修平均间隔时间(MTBR)使这些材料性能目标更难达到。其它非旋转部件也必须经受住极端运行环境的考验。喷注器面板、喷注壳体和预燃烧器在高温下都必须抗氧化、耐腐蚀、抗氢脆。喷嘴调节和控制流入主燃烧室的推进剂流量。预燃烧室是个小型燃烧室。在这个燃烧室里,产生涡轮驱动气体。在目前一些系统(其中一些被有效冷却)中,这些部件使用钴合金。未来发动机的这些部件,预计有极端的热环境(气体温度接近918℃)和高达62MPa 的压力。Si3N4 整体材料正在用作喷嘴壳体,但陶瓷壳体与金属推力室的匹配困难还没有解决。由于喷嘴壳体的形状是轴对称的,所以早就有人建议这种壳体采用连续纤维增强的复合材料,但部件的匹配条件向连续纤维增强的复合材料提出挑战。 以下为两种比较典型的镍基复合材料及其主要性能: (一)、镍基变形高温合金 以镍为主要基体成分的变形高温合金。镍基变形高温合金以汉语拼音字母“GH”加序号表示,如GH36、GH49、GH141等。它可采用常规的锻、轧和挤压等冷、热变形手段加工成材。按强化方式可分为固溶强化镍基变形高温合金,弱时效强化镍基变形高温合金和强时效强化镍基变形高温合

氧化铝陶瓷的制备与应用

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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。

低温烧成陶瓷结合剂磨具

低温烧成陶瓷结合剂磨具 河南工业大学材料科学与工程学院 侯永改 陶瓷结合剂磨具具有强度较高,耐热性能好,切削锋利,磨削效率高,磨削过程中不易发热和堵塞,热膨胀量小,易控制加工精度,且容易修整等特点。 陶瓷结合剂磨具一般用于粗磨、半精磨、精磨及某些产品的抛光,接触面积较大的成型磨削,超硬磨料烧结体的磨削等。陶瓷结合剂磨具广泛应用于机械制造行业,许多重要的机器零件都要进行磨加工。如喷汽发动机,水压汽轮机,一般用螺旋浆,轴承部件等。在这些零件的加工中陶瓷结合剂磨具都发挥了很好的作用。 陶瓷磨具产量比较大,从过去到现在,陶瓷磨具在磨具总的构成中一直占主要地位,尽管随着结合剂材料种类的不断发展和磨具种类的扩大,陶瓷磨具产量在磨具总产量中呈下降趋势,但仍占有较大比例。因此,有必要对陶瓷结合剂磨具进行进一步的研究,比如降低烧成温度以节约能源,改善磨具的结构与性能等。 一.低温烧成陶瓷结合剂磨具的优势 1.低温烧成含义 就这个问题我从多方面进行了查找,没有一个确定的答案,下面有几个方面的例子: 通过配方调整使工业硬瓷的烧成温度从1400℃降低到1300℃是低温烧成;日用有骨质瓷外观的陶瓷的烧成温度从约1200℃降低到1050~1080℃是低温烧成;工艺陶瓷烧成温度已经达到850~900℃的低温;低温烧成、低膨胀性陶瓷釉料可在700~1000℃的低温范围烧成,并具有低的膨胀系数(热膨胀系数α≤6.0×10-6/℃)。 所以一般说来,凡烧成温度有较大幅度降低(60~100℃)且产品性能与通常烧成产品性能相近的烧成方法可称为低温烧成。 对我们陶瓷磨具来说烧成温度从约1250℃降低到1150℃、1050℃也是低温烧成,但人们习惯上把烧成温度在1000℃以上称为高温烧成,在1000℃以下称

镍基复合材料

镍 基 复 合 材 料 的 应 用 10级金属(1)班 1007024101

镍基复合材料的应用 镍基复合材料是以镍及镍合金为基体制造的。由于镍的高温性能优良,因此这种复合材料主要是用于制造高温下工作的零部件。 镍基复合材料主要用于液体火箭发动机中的全流循环发动机。这种发动机的涡轮部件要求材料在一定温度下具有高强度、抗蠕变、抗疲劳、耐腐蚀、与氧相容。在目前正在研制的系统中这些部件选用镍基高温合金。虽然用SiC 颗粒或纤维增强的复合材料可以达到高强度、高刚度和抗蠕变。但在全流循环发动机的富氧驱动气体环境下,这些材料不能兼顾与氧的相容性。发动机起动瞬变过程的热冲击环境,排除了涡轮叶片采用加涂层的材料系的可能。 因此,用整体材料制作的涡轮叶片,必须经受住富氧燃烧产物所形成的环境。因为涡轮部件和涡轮盘在大约9min 运行中一般不用冷却,所以在短时运行中,整体材料温度达到730℃是正常的。对某些设计,希望密度低于6.5g/cm3 的材料的强度要大于1040MPa。应力、温度和化学环境都十分苛刻,要延长维修平均间隔时间(MTBR)使这些材料性能目标更难达到。其它非旋转部件也必须经受住极端运行环境的考验。喷注器面板、喷注壳体和预燃烧器在高温下都必须抗氧化、耐腐蚀、抗氢脆。喷嘴调节和控制流入主燃烧室的推进剂流量。预燃烧室是个小型燃烧室。在这个燃烧室里,产生涡轮驱动气体。在目前一些系统(其中一些被有效冷却)中,这些部件使用钴合金。未来发动机的这些部件,预计有极端的热环境(气体温度接近918℃)和高达62MPa 的压力。Si3N4 整体材料正在用作喷嘴壳体,但陶瓷壳体与金属推力室的匹配困难还没有解决。由于喷嘴壳体的形状是轴对称的,所以早就有人建议这种壳体采用连续纤维增强的复合材料,但部件的匹配条件向连续纤维增强的复合材料提出挑战。 以下为两种比较典型的镍基复合材料及其主要性能: (一)、镍基变形高温合金 以镍为主要基体成分的变形高温合金。镍基变形高温合金以汉语拼音字母“GH”加序号表示,如GH36、GH49、GH141等。它可采用常规的锻、轧和挤压等冷、热变形手段加工成材。按强化方式可分为固溶强化镍基变形高温合金,弱时效强化镍基变形高温合金和强时效强化镍基变形高温合金3类。

树脂结合剂金刚石工具性能的研究

树脂结合剂金刚石工具性能的研究 树脂结合剂金刚石磨具是金刚石磨具中使用量最大的一类。和金属结合剂金刚石磨具和陶瓷结合剂金刚石磨具相比,树脂结合剂金刚石磨具有磨具硬化温度低,只需200℃左右,远远低于金属结合剂和陶瓷结合剂金刚石磨具的热压成型 温度;生产周期短,生产设备简单,生产能耗少,规模生产可降低成本;形成自锐性,提高磨具锋利性;被加工工件的表面光洁度高,适用于镜面磨削;其缺点是寿命短,耐热性差,易老化。 其中最根本原因是:树脂结合剂胎体对金刚石的把持力小。为了提升树脂结合剂磨具的寿命,通常采用两种方法进行改进。 一种方法是尝试新型树脂或者对现有树脂进行改性,提高树脂的耐热性;另一种方法是对金刚石进行镀覆,提高树脂对金刚石的把持力。镀覆金刚石在金属结合剂和陶瓷结合剂的磨具中应用的相应研究较多,但镀覆金刚石在树脂结合剂中的研究却鲜有报道。 本文通过采用对无镀层金刚石、镀覆刚玉金刚石和金属镀层金刚石制备的金刚石树脂结合剂磨具性能进行对比分析,研究镀覆种类对两种树脂结合剂磨具的锋利性、耐用性、力学性能以及对树脂结合剂的结构和致密度的影响,获得如下结论:(1)采用聚酰亚胺树脂(PI)作为结合剂,在金刚石、聚酰亚胺(PI)、氧化铬等组分确定的前提下,实验填料的最佳配比为碳化硅微粉30(vol)%,合金粉 4(vol)%,冰晶石4(vol)%,此时,树脂金刚石磨具磨削比最大,达到2.286,具备良好的磨削性能,使用性价比较高。(2)按照最佳填料配方,采用无镀层金刚石、镀覆金属(钛、铜、镍)镀层金刚石和镀覆刚玉镀层金刚石压制两组平行实验试样进行性能对比分析。

结果表明:在其他组分含量保持不变的前提下,对金刚石进行表面镀覆处理可以明显提高磨具的磨削比,提高磨具的磨削效率,并且可以提高试样的抗弯强度、硬度等力学性能。三种金属镀层(钛、铜、镍)中,钛镀层的镀覆效果最好,对树脂磨具的磨削性能和力学性能提升明显,无机物刚玉镀层镀覆效果优于金属镀层。 (3)使用无镀层金刚石的配方试样,聚酰亚胺(PI)树脂结合剂金刚石磨具拥有更好的耐磨性和锋利性;使用含镀层的金刚石配方试样,情况相反。在无水冷磨削条件下,酚醛树脂(PF)树脂结合剂使用镀覆镀层的金刚石对树脂磨具的磨削性能提升幅度更大。 (4)对金刚石进行表面镀覆可以影响到热压后酚醛树脂(PF)结合剂的结构和致密度,并且表面更粗糙的刚玉镀层影响更大。靠近金刚石的酚醛树脂(PF)更为致密,对金刚石形成保护性包裹,远离金刚石的酚醛树脂(PF)更为稀疏。

CBN超硬材料磨用低温陶瓷结合剂的设计实验

CBN 超硬材料磨用低温陶瓷结合剂的设计实验 本实验中要求设计一种适用于超硬磨料的陶瓷结合剂,要求其抗折强度大于60MPa ,膨胀系数小于7×10-6/℃,烧结温度不高于950℃。通过配方设计、高温熔制、制样、烧结温度范围测试直至烧结后测试样品的热膨胀系数、抗折强度测试等等。了解设计一种新的超硬磨料陶瓷结合剂需要考虑的多方面的影响因素,从而提高分析问题、解决问题的能力。 实验目的:设计一种低温高强度的CBN 砂轮陶瓷结合剂。 实验流程如下:玻璃组成的设计与配合料的制备→玻璃料的熔制→试样的制备→压制成型→烧结温度范围的测定→烧结→试样相关性能测试(热膨胀系数、抗折强度) 一、玻璃组成的设计与配合料的制备 配料是根据设计的玻璃成分和选择的原料的化学组成来计算的。为得到指定性能的玻璃,玻璃的熔制需要反复实验多次,并多次修改玻璃成分,以达到合乎要求的玻璃性能。因此要根据实验结果反复改变配方,及时调整原来组成及其质量配比。 设计配方时,应注意原料中所含水分的变动,要确切地掌握原料的化学成分,然后按所要求的玻璃成分,并根据各种原料的化学成分计算配方。同时根据试验中相关性能测试所用试样的质量及实验过程中的损耗量,确定原料的总用量。 根据现有实验条件,运用相关专业知识,查阅大量相关文献,并理论计算相关性能的契合度,设计配方如下: 确定玻璃的类型为硼酸盐玻璃体系。 (A )相关计算 1、 膨胀系数(干福熹法计算)《玻璃工艺学》 计算得Ψ= -0.72595 <4,又SiO 2含量为 48.21%,则α(B2O3)=12.4*(4-Ψ)= 8.0172*10-7 α(SiO2)=35+0.5*(67-a)=44.44*10-7 整体膨胀系数计算公式为 2、 熔制温度《无机材料专业实验指导书》 τ=( SiO2+ A1203)/(Na20+ K20+0.5 B203)=4.00827 表1 不同τ对应的熔制温度 查表知熔制温度约为1320C 3、 抗折强度 抗折强度指模局在受到弯曲应力作用时不发生破裂的极限能力。大约相当于抗拉强度的3-3.5倍。 玻璃的化学组成对其强度的贡献符合加法法则。 抗拉强度为71.2835MPa ,则抗张强度213.8505-249.4923 MPa 4、 耐火度 SiO2 A1203 B203 K20 Na20 Li20 CaO MgO 整体 摩尔质量 60.1 102 69.6 94.2 62 29.8 56.1 40.3 质量百分数% 48.21 19.63 13.75 2.45 7.6 2.23 3.56 2.57 100 摩尔组分 80.21631 19.2451 19.75575 2.600849 12.25806 7.483221 6.345811 6.377171 154.2823 摩尔百分数% 51.99321 12.47395 12.80494 1.685773 7.945219 4.850344 4.113118 4.133444 100 膨胀系数(10^-6) 4.444 -4 0.860172 51 40 26 13 6 6.961826 组分膨胀系数(10^-8) 214.2452 -78.52 11.82737 124.95 304 57.98 46.28 15.42 696.1826 温度系数 1 1. 2 1.25 1 1 1 0.5 0.6 0.456895 抗拉强度系(Mpa ) 0.9 0.5 0.65 0.1 0.2 2 0.1 71.2835

重熔处理过程对镍基合金复合涂层的组织变化影响

科技信息SCIENCE&TECHNOLOGYINFORMATION2013年第5期作者简介:刘铎(1980—),男,汉族,工程师,主要从事特种设备型式试验、检测及复合材料制造、电阻焊和堆焊的研究。 0前言磨损是导致工程材料失效的最主要因素之一,如何通过改善材料 的耐磨损性能来降低材料的损耗,一直是材料科学工作者非常关注的 问题。镍基自熔性合金(NiCrBSi )具有较好的力学性能和耐蚀性,是一 种常用的耐滑动磨损材料,其形成的NiCr 、Cr 2B 、Cr 5B 3、CrB 及一些碳 化物有助于提高结合强度和硬度。用其制备的NiCrBSi/WC 复合涂层, 对于汽车气缸摩擦副的耐磨损性提高有很大作用[1-2]。近年来,很多研 究集中在添加元素对镍基合金的性能变化作用,例如Mo 的加入可以 改善涂层的抗咬死性,减少熔覆层的开裂敏感性[3];Ce 或La 2O 3可以促 进硬质相和棒状第二相均匀分布,减少气孔和夹杂[4];Al 2O 3提高复合 材料涂层的整体抗冲蚀性[5];六方BN 具有和石墨一样的润滑机制,具 有更好的热稳定性,对涂层自润滑性的提高有显著影响[6];CrC 促进硬 质相形成,延长涂层在磨损过程中的使用寿命[7]。相应的涂层制备方法 有很多种,常见的有激光熔覆、火焰喷涂、等离子喷涂、高频感应熔覆、 喷焊等等。其中等离子喷涂方法使用较为普遍,其具有参数调整方便 灵活,沉积效率高的优点,在耐磨耐蚀涂层制备方面应用广泛。 本文主要探讨利用超音速等离子喷涂技术制备NiCrBSi/20%WC 复合涂层,并对喷涂后的涂层进行火焰重熔处理,通过对复合涂层火 焰重熔处理前后的显微组织进行检测分析,了解其微观结构变化对复 合涂层机械性能的影响。1试验方法所选用基体材料为碳素结构钢Q235A ,试样尺寸为80×40×5 mm ,表面经喷砂处理后粗糙度达到R a =3.2μm ,并用丙酮清洗。喷涂材 料选用镍基碳化钨粉末(含20%WC ),粒子尺寸在50-150μm ,形貌见 图1,其中不规则块状物质即为碳化钨。 图1NiCrBSi/20%WC 合金粉末形貌 沉积涂层使用美国普莱克斯生产的3710型超音速等离子喷涂设 备,等离子枪为SG-100型。喷涂前利用等离子焰流对基体进行预热 处理,喷涂工艺参数如下所列:电压42V ;电流550A ;氩气45psi ;氢气 15psi ;喷涂距离110mm 。涂层的厚度约0.4mm 。喷涂后涂层经氧-乙炔 火焰重熔后,制备金相试样,用5%的硝酸酒精对界面和涂层部分进行 腐蚀,使用扫描电镜观察涂层的微观结构,能量色散谱(EDS )分析涂 层的成分,X 射线衍射仪的Cu 靶K α线进行相结构研究。用显微硬度 仪分析横截面的显微硬度,测试点选取10个,取平均值,载荷砝码为 100g 。利用滑动摩擦磨损试验机进行磨损试验15分钟,并用扫描电镜 观察磨损区域的表面形貌。2 试验结果与分析2.1涂层的相结构与微观形貌等离子喷涂后的NiCrBSi 涂层,具有典型的热喷涂涂层结构特征,主要是由扁平化的粒子组成,其间夹杂熔化不完全的颗粒,存在部分孔隙。在加入20%WC 后,可以观察到分布于涂层中的WC 颗粒,见图2。这部分WC 颗粒主要来源于喷涂过程中,由于焰流速度过快而未熔化的WC 粉末。通过电镜照片可以观察到,其分布并不均匀,但这种高硬度的材料是提高涂层耐磨性的主要成分。 图2喷涂后NiCrBSi/20%WC 复合涂层形貌 为涂层进行能谱分析,在涂层中有个别区域出现细长针状物质,通过能谱分析可以发现,其主要成分依旧是Ni ,质量百分比占了50%,但Si 、Fe 和Cr 含量相对其他区域有所增加,(Fe ,Cr )7C 3形状大部分为针状,与此结构相似。Cr 和C 的产物很多,但涂层中出现的主要是(Fe ,Cr )7C 3,这与三者之间的反应有关[8]。Fe-C 与Cr-C 产物中都可以溶解Cr 或者Fe ,但在高于1200℃时,Cr-C 反应产物稳定存在,Fe-C 主要是以液态产物存在。由于涂层中的主要元素是Ni ,Ni 与Fe 可以形成γ-Fe ,但由于粉末本身Fe 含量较少,故形成的γ-Fe 并不多。虽然涂层中含有B 元素,但由于能谱对于C 元素只能定性分析而不能定量表示,B 元素比C 元素原子量更低,因此能谱无法检测其存在。但B 和Si 元素可以溶解于γ-Fe 和(Fe ,Cr )7C 3中。氧-乙炔火焰重熔后的涂层,结构产生变化。加入WC 后的涂层,在重熔过程中,主要被γ-Ni 固溶体所包覆。虽然还有块状组织,但经过加热,主要形成W 2C 相,分布于涂层各部分,这在摩擦磨损中起到重要作用。火焰重熔处理对于整个涂层来说,使各种合金元素相互扩散,形成Cr 7C 3,CrB ,Cr 2B 等弥散分布于γ-Ni (主要是Ni-Cr )的硬质相。一般来说,Cr 7C 3维氏硬度可以达到1450HV ,而CrB 可达到1300HV 。经过重熔处理,由于加热充分和元素的扩散效应明显,涂层与基体能够形成冶金结合,较之等离子喷涂形成的主要是机械结合的涂层,其结合强度大幅提高。2.2硬度测试加入20%WC 的等离子喷涂涂层硬度可以由600HV 经过重熔提高到将近1000HV 。这与重熔后硬质相弥散分布,缺陷减少有很大关系。2.3摩擦磨损试验图3a )为等离子喷涂NiCrBSi/20%WC 涂层磨损后的形貌,图3 b )则为经重熔后复合涂层的磨损形貌。通过比较可以发现,NiCrBSi/ 20%WC 涂层的试样磨损表面有明显的犁沟和少量剥落的坑,这是由 重熔处理过程对镍基合金复合涂层的组织变化影响 刘铎王玉刘颖孙大超 (沈阳特种设备检测研究院,辽宁沈阳110035) 【摘要】采用超音速大气等离子喷涂方法,在Q235A 钢基体上制备了含有20%WC 的NiCrBSi 复合涂层,并对涂层进行氧-乙炔火焰重熔处理。利用扫描电子显微镜对重熔前后的涂层进行微观结构分析,并采用X 射线衍射方法研究其相组成。发现重熔处理后涂层中缺陷减少,WC 、CrB 和Cr 7C 3等硬质相被γ-Ni 固溶体所包覆,对提高涂层的显微硬度和耐摩擦磨损性能有显著作用。 【关键词】WC ;NiCrBSi ;重熔处理;复合涂 层 ○科教前沿○72

低温烧成陶瓷结合剂磨具的优点

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透明氧化铝陶瓷制备的研究进展

透明氧化铝陶瓷制备的研究进展 关键词:透明氧化铝,透光率,烧结助剂,烧结工艺 1引言 透明氧化铝陶瓷最早是由美国Coble博士发明的,他通过在Al2O3中添加0.25wt% MgO,于1700~1800℃氢气气氛下烧结出呈半透明的氧化铝陶瓷,从此开创了透明氧化铝陶瓷研究和应用的新篇章[1]。经过半个世纪的不懈努力和研究,科研工作者发现,通过提高氧化铝的纯度、致密度以及合理的调控显

微结构,可以显著提高氧化铝陶瓷的透光性。 随着研究的不断开展,制备氧化铝陶瓷的烧结助剂得到了极大地扩展,除了MgO,一些稀土氧化物(如Y2O3、La2O3、ZrO2等)同样可以作为氧化铝陶瓷的烧结助剂,并且采用复合添加剂的效果优于单独使用MgO。关于添加剂的引入方式,谢志鹏等[2]提出了化学沉淀包覆工艺,在1800℃氢气气氛下烧结,制备了透明氧化铝陶瓷。与传统的球磨工艺相比,该方法能够实现添加剂在氧化铝基体中的均匀分布,从而大大提高了陶瓷的透光性。 关于透明氧化铝陶瓷的烧结技术,最近的研究工作表明,采用热等静压(HIP)、放电等离子(SPS)等特种烧结工艺可以制备出亚微米晶的高性能透明氧化铝陶瓷。例如,Jin等[3]采用SPS工艺,于1250~1350℃,80MPa压力下烧结,制备了晶粒尺寸小于1μm,直线透光率为53%的透明陶瓷。由于晶粒细小,其机械强度也非常优异。 此外,Mao等[4]就氧化铝晶粒光轴取向对透光性的影响进行了研究,他们通过在强磁场条件下进行透明Al2O3陶瓷浆料的注浆成型,使烧结后的Al2O3陶瓷晶粒光轴趋于一致,从而减少六方晶系Al2O3陶瓷因双折射率不同带来的光损失,显著提高透明Al2O3陶瓷的透过率。下面就影响氧化铝陶瓷透光性的各种因素,以及氧化铝粉体选择、烧结助剂及作用、烧结工艺及透明氧化铝陶瓷的应用进行综述。 2影响氧化铝陶瓷透明性的因素 2.1.1气孔 对透明陶瓷透光性能影响最大的因素是气孔率,又包括气孔尺寸、数量、种类。普通陶瓷即使具有高的密度,往往也不是透明的,这是因为其中有很多封闭气孔,并且当陶瓷内部的气孔率大于1%时,陶瓷就基本不再透明。有实验

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