Point contact surface fatigue in zirconia ceramics

The surface deformation and fragmentation behaviour of three zirconia ceramics have been studied by using unlubricated metallic repeated point contact loading at room temperature to investigate the possibilities of cyclic fatigue effects. All tests were conducted on a purpose built computer-controlled apparatus. The zirconias studied were ceria stabilized tetragonal polycrystalline, magnesia partially stabilized, and single crystal calcia stabilized. 120° steel cones were cyclically loaded against the flat, polished zirconia counterfaces, and the damage was observed and analysed as a function of the number of cycles, up to a total of 5 × 10⁵ cycles, for loads of 19.6 ± 9.8 N. The ground tips of the cones plastically deformed during the initial loading cycle to produce a flattened end which conformed with the zirconia counterface. The contact pressures were in the range 4 to 10 GPa. In all cases plastic deformation was observed in the zirconias within, and adjacent to, the contact areas. The degree of plastic deformation increased with increasing number of cycles. After approximately 1 × 10⁴ cycles, localized cracking was induced at the peripheries of the contact zones, which gradually increased in extent until after 5 × 10⁵ cycles there was extensive fragmentation. No material transfer, i.e. metal onto ceramic, or vice versa, was generally observed until after the surface had become rough as a result of the fracturing.     

High strain rate compression of titanium and some titanium alloys

A modified Hopkinson bar was used to compress specimens of commercially-pure titanium, IMI 125 and titanium alloys, AMS 4911B and AMS 4916B, at natural strain rates of between 3 × 10³ s⁻¹ and 3 × 10⁴ s⁻¹. All three materials deformed in a viscous manner with a linear increase of flow stress with strain rate and a macroscopic viscosity of 4·5 kPa s, 5·7 kPa s and 9·2 kPa s, respectively. At strain rates above about 1 × 10⁴ s⁻¹ there was a decrease in macroscopic viscosities to 0·9 kPa s and 2·5 kPa s for the titanium and 4911B alloy respectively, which is attributed to changes in the dislocation drag mechanisms. The results for the 4916B alloy at the higher strain rates were too scattered to give a definite trend. It is suggested that the increase in the macroscopic viscosity with alloying is due to an increase in the dislocation drag coefficient by solution hardening and to a reduction in the density of mobile dislocations by dislocation pinning.

It is also proposed that the susceptibility of these materials to catastrophic shear failure which occurs without prior linear work-softening is due to the higher propensity for titanium and titanium alloys to shear failure as a consequence of their thermo-mechanical properties. The decrease of strain at which shear occurred with increasing strength is in accord with this suggestion.     

The high strain rate compression of 1023 and 4130 steels

Steel specimens of type 1023 and heat treated 4130 steel of hardnesses, between 257 and 450 HV10, were compressed at strain rates between 3 × 10³ and 3 × 10⁴ s⁻¹ using a modified Hopkinson bar. Both steels showed viscous type flow behaviour with a linear increase in flow stress with strain rate. For the 1023 steel there were two linear regions, one from 3 to 12 × 10³ s⁻¹ with a macroscopic viscosity of 4·7 kPa s and two from 14 to 27 × 10³ s⁻¹ with a viscosity of 0·7 kPa s. These results indicate some change in the controlling mechanism. For the 4130 steel the macroscopic viscosity decreased linearly with increasing hardness from 7·4 kPa s at 257 HV 10 to 2·2 kPa s at 450 HV 10. This was probably due to a decrease in the density of mobile dislocations with increased tempering temperatures. At lower hardness values (257 and 300 HV 10) and higher strain rates, a levelling off of the flow stress occurred but the data were too scattered to give a definite trend. The heat generated due to deformation of the 1023 steel was sufficient to produce steady state flow at strains above about 0·3. In the 4130 steel the thermo-mechanical properties were such that linear work softening was observed at a rate inversely proportional to the square root of the strain rate and independent of the hardness. This suggests that the work softening was a function of properties of the common ferrite matrix. The strain at which the work softening commenced decreased with increasing hardness, because of the more rapid heat generation at higher flow stresses. At higher hardness and higher strain rates 4130 steel failed by shear. Shear failure occurred at lower strain rates with increasing hardness and, for a given hardness, at lower strains with increasing strain rate. This behaviour was consistent with Recht's analysis of catastrophic shear failure.     

The effect of number of cycles on the critical transition boundary between fretting fatigue and fretting wear

The object of the present study was to investigate the influence of number of cycles on the critical amplitudes of tangential force and displacement, identifying the transition from a mixed stick-slip regime (fretting fatigue) to a gross slip regime (fretting wear) over a wide range of test conditions. Fretting experiments were conducted on three metal specimen combinations: copper/copper; stainless steel/stainless steel; copper/stainless steel. All experiments took place in air, at ambient temperature, using a crossed-cylinder geometry. Normal loads of 3.4 and 11.4 N were applied with frequencies ranging from 10 to 800 Hz. In most cases, n = 1.2×10⁴ and n = 6×10⁶ were adopted as the representative lower and higher number of cycles, respectively. At different numbers of cycles, critical amplitudes of tangential force and displacement were measured. The scars fretted under separately selected conditions were examined by scanning electron microscopy.

It was found that the critical amplitudes of both tangential force and displacement dropped with increasing number of cycles for all test combinations, but there was an upper limit above which the drop of critical transition values no longer occurred with further increases in the number of cycles. The micromorphology of fretting scars (in a mixed stick-slip regime) revealed that the stick zone has shrunk after a larger number of cycles under the conditions of constant amplitude of tangential force and displacement, and that the damage mechanisms vary for different combinations, although they are all characterized by a central stick zone surrounded by a slip annulus. It was suggested that the decrease of critical amplitudes after a larger number of cycles results from the shrinkage of the stick area, which may be a complex process related to plastic deformation, strain hardening, and the change of stress distribution on the contact surfaces.     

Characterisation of wear debris from UHMWPE on zirconia ceramic, metal-on-metal and alumina ceramic-on-ceramic hip prostheses generated in a physiological anatomical hip joint simulator

There is currently much interest in the characterisation of wear debris from different types of artificial hip joints. There have been numerous studies on the wear of UHMWPE in hip joint simulators, but relatively few studies on the wear of alternative materials such as metal-on-metal (MOM) and ceramic-on-ceramic (COC). The aim of this study was to compare the wear volumes and wear debris generated from zirconia ceramic-on-UHMWPE, MOM and COC hip joints under identical conditions in the same hip joint simulator.

All prostheses showed an initial higher ‘bedding in’ wear rate, which was followed by a lower steady state wear rate. The zirconia ceramic-on UHMWPE prostheses showed the highest wear rates (31±4.0 mm³/million cycles), followed by the MOM (1.23±0.5 mm/million cycles), with the COC prostheses showing significantly (P<0.01) lower wear rates at 0.05±0.02 mm³/million cycles. The mode (±95% confidence limits) of the size distribution of the UHMWPE wear debris was 300±200, 30±2.25 nm for the metal particles, and 9±0.5 nm for the ceramic wear particles. The UHMWPE particles were significantly larger (P<0.05) than the metal and ceramic wear particles, and the metal particles were significantly larger (P<0.05) than the ceramic wear particles. A variety of morphologies and sizes were observed for the UHMWPE wear particles, including submicrometer granules and large flakes in excess of 50 μm. However, the wear particles generated in both the MOM and COC articulations were very uniform in size and oval or round in shape.

This investigation has demonstrated substantial differences in volumetric wear. The in vitro wear rates for the zirconia-on-UHMWPE and MOM are comparable with clinical studies and the UHMWPE and metal wear particles were similar to the wear debris isolated from retrieved tissues. However, the alumina/alumina wear rate was lower than some clinical retrieval studies, and the severe wear patterns and micrometer-sized particles described in vivo were not reproduced here.

This study revealed significant differences in the wear volumes and particle sizes from the three different prostheses. In addition, this study has shown that the alternative bearing materials such as MOM and COC may offer a considerable advantage over the more traditional articulations which utilise UHMWPE as a bearing material, both in terms of wear volume and osteolytic potential.     

The mean dynamic yield strength of copper and low carbon steel at elevated temperatures from measurements of the “mushrooming” of flat-ended projectiles

Mean dynamic yield strengths for copper and mild steel are deduced from strain measurements on the “mushroomed” ends of flat-ended projectiles, after impact on a flat, nominally rigid anvil. The kinetic energy at impact is equated with plastic work, to give a mean dynamic yield strength averaged over the deformed specimen. Experiments are carried out over the temperature range 20–700°C, with impact velocities in the region of 600 ft/sec, giving a mean strain rate estimated at 5 × 10³/sec. The yield stress-temperature results obtained show an abrupt increase in dynamic/static mean yield stress ratio at homologous temperatures, T/T_M, of 0·4 for steel and 0·5 for copper. These results agree generally with the findings from other investigations into high-speed blanking⁵ and indentation.⁷

Existing theories for the mushrooming of flat-ended projectiles^{1, 3} do not predict the profiles actually obtained in the present experiments.     

Fatigue of bitumen and bituminous mixes

This paper gives details of an investigation into the fundamental fatigue properties of bitumen and bituminous mixes. Fatigue tests carried out under constant bending stress, at varying temperatures between −13·5°C and +25°C, show that the material exhibits fatigue properties over wide ranges of stress and that for a particular temperature and speed of loading the log stress-log number of cycles to failure relationship is linear between 10⁴ and 10⁸ cycles. The life under constant stress is highly dependent on the temperature of the test, a low temperature giving a longer life at a particular stress; it is also dependent to some extent on the speed of loading, but taking into account the stiffness of the material which depends on temperature, speed of loading, rheological characteristics and composition of the mix, it has been found that when the logarithm of the strain is plotted against the logarithm of the number of cycles to failure all experimental results at different speeds and temperatures for one mix lie with a certain amount of scatter about a straight line. It appears therefore that the factor affecting the fatigue life is one of strain rather than stress, and the effects of temperature and speed can be accounted for by their effect on the stiffness of the specimen. This has been confirmed by tests under constant torsional strain at different temperatures between −20°C and +40°C, but at the higher temperatures under this type of loading the fatigue life includes a considerable crack-propagation time. Similar results have been obtained from mixes containing different amounts of aggregate, but as the quantity of aggregate in the mix is reduced so the life for a given strain increases, suggesting that the criterion of failure may be one of tensile strain in the bitumen present in the mix. Some tests have also been carried out on pure bitumen specimens at different temperatures.

Careful examination of the fatigue cracks and failure surfaces shows that in nearly all cases failure originates on the principal tensile plane. The effects of such factors as surface conditions, void content and rest periods have also been studied.     

Effects of a second phase on the tribological properties of Al2O3 and ZrO2 ceramics

The tribological properties of four different materials are investigated, tetragonal zirconia (Y-ZTP), Al₂O₃ dispersed in Y-TZP (ADZ), ZrO₂ dispersed in Al₂O₃ (ZTA) and Al₂O₃ (with 300 ppm MgO). These materials are used as a cylinder sliding against a plate of Y-TZP (TZ-3Y)). Compared to Y-TZP, the wear resistance of ADZ composites is increased by a factor of 4–10. At a contact pressure of 230 MPa, a wear transition for Y-TZP is observed from plastic deformation to microchipping and microfracture due to the high interfacial temperature (450°C–550°C) generated by frictional heating. Because of the higher elastic modulus, hardness and fracture toughness at high temperature, ADZ composites show better wear resistance and a higher transition contact pressure (over 400 MPa) under the present conditions. For Al₂O₃, the transition from mild to severe wear occurs when the contact pressure is changed from 250 to 400 MPa. For ZTA ceramics, the wear behaviour does not change because of the presence of a compressive layer due to the zirconia phase transformation during sliding.

In water the wear resistance for ADZ and ZY5 is almost two orders of magnitude higher than the results under dry conditions. Reduction of the interfacial temperature by using water and the formation of a hydroxide layer at the contact surface by the tribochemical reaction of water with the ceramic, as observed by XPS, gives a positive effect on wear resistance.     

Preliminary considerations in the use of industrial sonic nozzles

Preliminary considerations applying to the necessary instrumentation for the use of sonic nozzles is reviewed. A way to make sonic nozzles for industry, together with a method to determine the discharge coefficient of a convergent nozzle operating in the sonic regime in conditions of ideal flow is suggested. The results obtained for the behaviour of the discharge coefficient of sonic nozzles, in the range from 4×10⁴ to 2×10⁵ are compared with the standard ISO 9300 (Standard ISO 9300. Measurement of gas flow by means critical flow Venturi nozzles, 1990) and the curve proposed by Ishibashi et al. (M. Ishibashi, M. Takamoto, N. Wanatabe, Y. Nakao. Precise calibration of critical nozzles of various shapes at the Reynolds number of 0.2–2, 5×10⁵. Proceedings of FLOMEKO 94).     

Tribological behavior of aluminum alloys surface layer implanted with nitrogen ions by plasma immersion ion implantation

Some 2014 and 2024 aluminum alloys were implanted with nitrogen ions (N⁺) by Plasma Immersion Ion Implantation (PIII), and dose range was from 2×10¹⁷ to 1×10¹⁸ N⁺ cm⁻². The microstructure of surface layer was studied by Transmission Electron Microscopy (TEM). The depth profile of the implanted layer was investigated by Auger Electron Spectrometry (AES). The wear test was carried on a pin-on-disk wear tester. The micro-morphology of wear was observed by Scanning Electron Microscopy (SEM). The results reveal that: after implanted with nitrogen ions, the friction coefficient of surface layer decreased, and the relative wear resistance increased with the increase of the nitrogen dose. The tribological mechanism was mainly adhesive, and the adhesive wear tended to become weaker gradually with the increase of nitrogen dose. The upper two effects were mainly attributed to the formation of hard AlN precipitation and supersaturated solid solution of nitrogen in the surface layer.     

Effect of sliding speed on friction and wear behaviour of nanocrystalline nickel tested in an argon atmosphere

The sliding speed dependence of the coefficient of friction (COF) and wear rate (W) of a nanocrystalline (nc) Ni with a grain size of 15 ± 3 nm and a hardness of 5.09 ± 0.11 GPa was compared to that of a microcrystalline (mc) Ni with a grain size of 20 ± 5 μm and a hardness of 1.20 ± 0.05 GPa. The sliding wear tests were performed in an argon environment under a constant normal load of 2 N using three different sliding speeds of 0.2 × 10⁻², 0.8 × 10⁻² and 3.0 × 10⁻² m/s. The lesser wear damage in the nc Ni at any given speed was attributed to its higher hardness and its greater elastic depth recovery ratio compared to the mc Ni. The mc Ni's COFs and wear rates were independent of the sliding speed over the relatively small range used. However, the same small increase in sliding speed caused an 86% reduction in the nc Ni's wear rate, from 3.44 × 10⁻³ to 0.47 × 10⁻³ mm³/m, and a 31% increase in its COF, from 0.49 ± 0.05 to 0.64 ± 0.06. A modified Archard equation was proposed to predict wear rates of Ni as a function of grain size and sliding speed. Increasing the sliding speed made it increasingly difficult for surface damage by plastic deformation to occur in the nc Ni, because the grain-boundary-induced deformation mechanisms are more difficult to operate at higher strain rates. At the highest speed, the smallest amount of debris was generated, which was not sufficient to form protective tribolayers leading to a high COF value.     

A high resolution servo controlled goniometer

Recent advances in X-ray technology have led to a demand for very high precision in the remote angular positioning of analysing crystals. This paper discusses a new design of two-crystal scanning monochromator in which the crystal motions are synchronously controlled by a pair of specially developed goniometers. Each goniometer can locate its crystal at any one of 36 × 10⁶ discrete angular locations spaced approximately 0.000 01° apart. The main features of the goniometer design are described with particular emphasis on the absolute moiré fringe measuring system which is unique to this application     

The wear of artificial finger joints using different lubricants in a new finger wear simulator

A new design of finger wear simulator has been manufactured. The simulator is a dual cycle machine, interspersing dynamic flexion–extension motion, where the loads were 10–15 N, with periods of a static 100 N ‘pinch’ load. Also, a two-piece finger prosthesis has been designed and manufactured from silane cross-linked polyethylene. Using the simulator, a comparison of the wear of the cross-linked polyethylene prosthesis was undertaken, with Ringer solution, distilled water and dilute bovine serum as the lubricants. Each test was run at 37°C and included a control prosthesis to account for lubricant uptake. All prostheses came from the same batch, having a gel content of 87%. In total, testing exceeded 27 million cycles. With bovine serum, the total wear factor for the prosthesis was 0.07×10⁻⁶ mm³/N m. With Ringer solution it was 0.98×10⁻⁶ mm³/N m and with distilled water the wear factor was 0.60×10⁻⁶ mm³/N m. This order of results matched that found with pin on plate wear tests using these same three lubricants. The lower wear found with bovine serum may have been due to the positive boundary lubricating effects of the proteins within the serum. Lubricant uptake was greater and more significant in the bovine serum test.     

Rolling contact fatigue endurance of powder-extruded bearing steel

The mechanical and toughness properties and rolling contact fatigue endurance of powder-extruded bearing steel made from nitrogen atomized remelted turning powder in as-extruded and as-heat treated state are presented. The mechanical and toughness properties are comparable with those of wrought bearing steel. Rolling contact fatigue endurance was tested by the AXMAT method in as-extruded and as-spheroidizing annealed states depending on the austenitizing temperature, which ranged from 790 °C to 870 °C. Powder-extruded bearing steel in both states showed slightly higher hardness (63 HRC), higher contact fatigue resistance (L₁₀ = 80.7 and 55.2 million load cycles, respectively) in comparison with wrought steel (L₁₀ = 31.8 million load cycles). The results demonstrate the advantageous properties of powder-extruded bearing steel for high dynamic loading.     

Fretting properties of SUS304 stainless steel in a vacuum environment

In this paper the effect of the ambient pressure on the friction and wear of SUS304 stainless steel during fretting at room temperature is described.

The ambient pressure was varied from 10⁻³ to 10⁵ Pa. The experiment was carried out under the following conditions: normal load, 14 N; slip amplitudes, 35 and 110 μm; frequency, 8.3 Hz; number of fretting cycles, 6 × 10⁴.

The relationship between the frictional behaviour and the number of cycles is affected by the pressure. The coefficient of friction at steady state increases with a decrease in the pressure to below 10 Pa. From the point of view of the wear mechanism, the transition is determined as that from oxidative wear at the higher pressure to adhesive wear at the lower pressure. The transition pressure depends on the slip amplitude, i.e.it is 2.7 Pa at 35 μm and 10⁻¹ Pa at 110 μm. The wear volume is greater in the oxidative wear regime than in the adhesive wear regime. Oxide wear debris is removed easily from the interface in the former regime. In contrast, metallic wear debris is retained at the interface and adhesive transfer occurs from one surface to the opposing surface in the latter regime. The characteristic feature of the wear damage at 10⁻³ Pa and at 35 μm is the formation of a vertical crack at the boundary between the fretted and the unfretted areas.     

Tribological behavior of select MAX phases against Al2O3 at elevated temperatures

The layered M_n+1AC_n ternary carbides – MAX phases – Ta₂AlC, Ti₂AlC, Cr₂AlC and Ti₃SiC₂ were tested under dry sliding conditions against alumina at 550 °C and 3 N load (for a stress of ≈0.08 MPa) using a pin-on-disk tribometer. Ta₂AlC and Ti₂AlC exhibited low specific wear rates, SWRs, (≤1 × 10⁻⁶ mm³/N m), while the coefficients of friction, μ, were 0.9 and 0.6, respectively. At 0.4, μ of Ti₃SiC₂ was the lowest measured, but the SWR, at ≈2 × 10⁻⁴ mm³/N m, was high. With a μ of 0.44 and a SWR of 6 × 10⁻⁵ mm³/N m the Cr₂AlC sample was in between. No visible wear of Al₂O₃ counterparts was observed in all the tribocouples. Tribofilms, which were mainly comprised of X-ray amorphous oxides of the M and A elements and, in some cases, unoxidized grains of the corresponding MAX phases, were formed on the contact surfaces. The correlations between observed tribological properties and tribofilm characteristics are discussed.     

含芳香氨基酸三肽及其衍生物自由基离子的形成和解离机理研究

铜-配体(L)-三肽组成的三元复合物［Cu(L)M］²⁺,其中,L表示4′-氯-2,2′:6′,2″-三联吡啶(缩写为4Cl-tpy);M表示酪氨酰-甘氨酰-色氨酸(YGW)及其修饰型三肽(CH₃CO-YGW-OCH₃,缩写 Ac-YGW-OMe)。使用该复合物,通过碰撞诱导解离 (collision-induced dissociation, CID)产生两种自由基离子 (［YGW］^·+和［Ac-YGW-OMe］^·+)。采用串联质谱结合密度泛函理论 (density functional theory, DFT)得到气相稳定结构,并研究其气相解离行为。研究结果表明,［YGW］^·+和［Ac-YGW-OMe］^·+的气相解离行为截然不同,［YGW］^·+主要产生［M-CO₂-116］⁺和［M-CO₂］^·+碎片离子;而［Ac-YGW-OMe］^·+在气相中主要产生［M-CH₃OH］^·+碎片离子。推测这两种离子的气相裂解机理分别为：［YGW］^·+羧基上的质子重排到多肽骨架中羰基氧上,经历 C_α-C键的断裂产生［M-CO₂］^·+、断裂色氨酸侧链 C_β-C_γ键产生［M-CO₂-116］⁺离子;［Ac-YGW-OMe］^·+则先经历质子重排到酯基氧上,然后经过C-O酯键的断裂形成［M-CH₃OH］^·+离子。参与重排的质子可能有3个来源：Ac-YGW-OMe中甘氨酸的C_α-H、色氨酸的C_α-H 或C_β-H,该机理有待进一步验证。本研究将为其他类型多肽及衍生物的结构及气相反应机理研究提供参考。     

UPLC/Q-TOF MS/MS负离子模式下环氧烷型环烯醚萜苷的结构表征

利用四极杆飞行时间串联质谱(Q-TOF MS/MS)研究4个环氧烷型环烯醚萜苷同系组分(胡黄连苷Ⅰ、胡黄连苷Ⅱ、胡麻属苷、梓醇)的质谱裂解行为。在大气压化学电离源负离子(APCI~-)模式下,该类同系组分主要的裂解途径除了常见的母环上取代基的断裂,如中性丢失H_2O、CO_2和葡萄糖基等,生成~(1,6)F~-、~(1,4)F~-等特征碎片离子;另外还存在葡萄糖基环的断裂,生成~(0,4)A_1~-、~(1,4)A_1~-及~(2,4)A_1~-等碎片离子。通过对上述环氧烷型同系组分的质谱裂解行为进行归纳总结,依据其裂解规律,利用UPLC/Q-TOF MS/MS对胡黄连提取物中的环烯醚萜苷类化合物进行表征,共初步鉴定出10个环烯醚萜苷,其中包括8个环氧烷型环烯醚萜苷(胡黄连苷Ⅰ、胡黄连苷Ⅱ、胡黄连苷Ⅲ、胡黄连苷Ⅳ、黄金树苷、梓苷、婆婆纳苷和Piscroside B)和2个环戊烷型环烯醚萜(Boschnaloside和Mussaenosidic acid)。该方法有助于推动胡黄连在物质基础表征、质量控制和临床应用上的开发和利用。     

3-D analysis of semiconductor dopant distributions in a patterned structure using LEAP

This work presents the first 3-D analysis of lateral dopant diffusion in a patterned structure using a pulsed laser-assisted local electrode atom probe (LEAP). A structure similar to a device channel was created for this work by performing a 3 keV, 1×10¹⁵ cm⁻² As⁺ implant on a poly-Si line patterned wafer with 70 nm line width and 200 nm line pitch. The wafer was subsequently annealed at 950 °C for 1 s. LEAP samples were made using a site-selective in-situ focused ion beam (FIB) process. The results from LEAP analysis were then compared with high-resolution transmission electron microscopy (HRTEM) and Florida object-oriented process simulator (FLOOPS) results. Good structural agreement was found between the LEAP and HRTEM results. Several 1-D As concentration profiles extracted from the LEAP data were also found to be in good agreement with FLOOPS process simulation results. These profiles also represent for the first time that results from a 3-D process simulator have been able to be confirmed experimentally using a single sample.     

多肽衍生物中自由基介导的选择性C—C键断裂及异构体区分

选择性C—C键断裂反应是化学领域的前沿课题,尤其对于生物大分子,该研究具有重要意义。由于化合物中活性相似的C—C键普遍存在,选择性断裂其中1个C—C键是一大难点。本文以非天然氨基酸组成的多肽衍生物为研究对象,采用TEMPO自由基引发剂策略,将邻甲基苯甲酰(Bz)自由基引入多肽分子(M),在气相中成功制备出［Bz-M+H］^·+自由基离子。通过串联质谱实验发现,该离子相对于质子化多肽分子［M+H］⁺显示出更高的反应活性,具有更丰富的气相解离反应路径,其特征碎片离子［Bz·-a1］⁺和［(Bz-M+H)-HCOOEt］^·+可作为异构体区分和选择性C—C键断裂的灵敏探针,为质谱法区分多肽异构体和选择性C—C键断裂提供了思路和方法。